By Ron Barmby
When you need heat pumps the most, they pump heat the least.
This is according to an unbreakable law of physics that applies to the entire universe without exception, even black holes, and especially to heat pumps.
Heat pump promoters who claim otherwise must have defeated the second law of thermodynamics, which would theoretically also allow them to make time run backward.
In addition to denunciation by physics, the cost of operating heat pumps is often very high compared to natural gas-fired heating.
Heat pumps are often accurately described as an air conditioner in reverse. To understand how a heat pump works, it helps to know how an air conditioner works.
How An Air Conditioner Works
An air conditioner transports heat from inside a house to the outside in a continuous circuit using a chemical mixture called a refrigerant.
The refrigerant is piped into the house as a liquid under high pressure and at a temperature just above the outside air temperature. It expands into a gas across a valve that has a lower pressure on the other side and becomes very cold, about 4°C (39°F).
This part of the air-conditioning unit is called the evaporator because it causes the liquid refrigerant to evaporate into a gas. The cooling is a bit similar to when you let air out of a tire and the expanding escaping air feels cold. (If you want to know more details, look up the Ideal Gas Law.)
The pipe with cold gas-phase refrigerant is then passed in front of a fan inside the A/C unit (or furnace if it’s central A/C) to cool the room.
The second law of thermodynamics dictates that two bodies at different temperatures will equalize in temperature when brought into contact with each other.
How fast this equalization occurs is driven by the temperature difference between the two bodies: the bigger the temperature difference, the faster the heat exchange happens.
The pipe containing the refrigerant gets cold because it’s in contact with the cold refrigerant, and the air outside the pipe gets cold because it’s in contact with the cold pipe.
A fan speeds up the contact of the warm air in the room with the cold pipe and as the heat from the air is transferred to the refrigerant, the refrigerant gets warmer.
The low-pressure and now warm refrigerant is then piped outside the building to an electrically driven compressor, which reduces the gas in volume and increases its pressure.
The compressor puts energy into the gas causing it to heat up (the Ideal Gas Law again). The hot high-pressure gas is then cooled to near outside temperature by passing the pipe containing the gas for several loops in front of a fan that uses outside air to cool and condense the gas into a high-pressure liquid (which is why it’s called the condensing unit).
The high-pressure and near-outside-temperature liquid refrigerant is then piped inside the building and the whole circuit starts over again.
This circuit is called the Carnot Cycle after the French physicist Sadi Carnot who discovered it in 1824. It wasn’t until 1902 that American engineer Dave Carrier produced the first air conditioner.
How A Heat Pump Works
To convert an air conditioning unit into a heat pump, you place the evaporator (which attracts heat) outside of the house and the condenser (which expels heat) inside the house.
Furthermore, the heat pump refrigerant is chemically different so that it can be cooled in the evaporator to minus 25°C (minus 13°F). The refrigerant has to be colder than the outside temperature to absorb outside heat.
The two perceived advantages of a heat pump are:
- If the electrical energy to run the heat pump was produced without carbon dioxide (CO2) emissions, it’s considered a green heating source. But all electrical generation has some form of environmental impact, most likely out of mind at a remote site.
- Because it collects free heat from the outside and delivers it inside, the only cost to run a heat pump is the electrical energy for the compressor and fans. A heat pump is more energy efficient because it transfers existing heat, rather than creating new heat by the combustion of a fossil fuel or biomass.
But here is the catch: Energy efficiency is not the same as economic efficiency.
At an outside temperature of 10°C (50°F) for every unit of energy used to run the heat pump (purchased electricity), the heat pump can collect four units of energy from the outside (heat delivered into your home). At this outside temperature, the efficiency of the heat pump is 400%.
When the outside air temperature drops to minus 20°C (minus 4°F), the efficiency of the heat pump drops to 200%; one purchased unit of energy input delivers only two units of free heating energy.
This is a result of the ambient temperature (minus 20°C) approaching the refrigerant temperature (minus 25°C) and reducing the rate of heat exchange between the two. It’s the second law of thermodynamics at play. The smaller the temperature difference, the more slowly the heat exchange occurs.
A conventional natural gas furnace delivers only 0.9 units of heat energy for each unit of purchased energy, for an energy efficiency of 90%.
When Heat Pumps Suck
Where I am writing normally has temperatures colder than minus 20°C 20 days per year, and the retail cost of electricity is nine times more than natural gas on an energy equivalent basis.
With an outside temperature of 10°C, to heat a room to the same temperature a heat pump would use only 22.5% of the purchased energy of a natural gas furnace (22.5% = 90%/400%). But the total cost of that purchased energy would be twice as much (22.5% X 9 = 2).
Under mild weather conditions, the heat pump already has twice the operating expense as a natural gas furnace. Under common winter conditions of minus 20°C, the energy efficiency of the heat pump drops to 200%. It uses only 45% of the purchased energy, but that purchased electricity costs four times more than natural gas.
Your natural gas bill charges you by the gigajoule (GJ) and your power bill charges you by the kilowatt-hour (kWh). Currently where I live natural gas is $4.89/GJ, and electricity is $0.16/kWh. I have a 90% fuel-efficient natural gas furnace.
The following temperature scenarios provide a rough approximation of the difference in cost between running a furnace and running a heat pump where I live:
- The outside air temperature is 10°C or warmer—Divide the gas cost by 60 to get the kWh equivalent energy cost. If this number is smaller than the cost of electricity in kWh, then it is cheaper to operate a natural gas furnace than a heat pump. $4.89/GJ (gas) divided by 60 equals $0.08/kWh (electricity). In this scenario, heating my home with gas is half the cost of electricity needed to operate a heat pump ($0.08/$0.16).
- The outside air temperature is near minus 20°C—Divide the gas price in GJ ($4.89) by 120 to get the kWh equivalent cost ($0.04). My natural gas furnace cost is one-fourth of the cost of operating a heat pump.
- The outside air temperature is minus 25°C or colder—Most retail models of home-use heat pumps will probably not work at all because the refrigerant has to be colder than the outside temperature. Many heat pumps have a conventional electrical resistance heating element built in as a cold temperature backup. This is confirmation by the design engineers that they can not beat the second law of thermodynamics.
[Note to reader: One GJ of natural gas equals 278 kWh of electricity, and is roughly equivalent to one million British Thermal Units (BTUs).]
What Heat Pump Promoters Won’t Tell You
Granted, in moderate climates where winter home heating is more for comfort than survival, and especially where summer air conditioning is desirable, a heat pump that’s switchable to an air conditioner is probably worth looking into. They are more energy efficient, but there’s more to consider. For example:
- Compared to natural gas furnaces, heat pumps can have a much higher operating cost, which governments attempt to overcome by taxing fossil fuels and using those taxes to subsidize “green” electricity.
- Natural gas and other combustion furnaces provide instant heat and can warm up a cold house much faster than a heat pump can.
- In very cold weather heat pumps suck.
If heat pump promoters deny the above statements, they must be Oppenheimer-smart and have found a way around the universal second law of thermodynamics. Ask them if they are working on a time machine next.
This commentary was first published at Climate Change Dispatch on February 19, 2024.
Ron Barmby (www.ronaldbarmby.ca) is a Professional Engineer with a Master’s degree, whose 40+ year career in the energy sector has taken him to over 40 countries on five continents. His book, Sunlight on Climate Change: A Heretic’s Guide to Global Climate Hysteria (Amazon, Barnes & Noble), explains in layman’s terms the science of how natural and human-caused global warming work.
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
One of the elements in the Texas February 2021 cold spell and near grid crash was heat pumps transitioning to resistance heating as the temperature fell, and spiking electrical demand.
I experienced the Texas cold spell and had rather poor experience with my 2 heat pumps here in Hill Country. I fortunately had power the whole time, which I attributed to living near a small hydro power plant. Neighbors and businesses all around were not so lucky. The heat pump for the house had resistance backup, and kept the house warm, It made a lot of racket as it went through its regular defrost cycles. We did cut back on the temperature to help preserve power for others.
The lab/workshop heat pump with no resistance backup, was not so useful. It regularly iced up, and I mean serious icing. Twice it became a solid block of ice, from top to bottom. On the heating cycle, the entire perimeter is a sub-freezing array of tubes and fins. The frost plus dripping from the snow-covered roof totally blocked all air flow. We have 72 degree well water here, and twice I had to flood the unit with this water to melt the ice. It took over a half hour each time, to melt all the ice.
I previously had a ground water heat pump system in Michigan. It was installed in 1988. It was beset with reliability issues, mostly due to poor electrical system designs. It finally had to be replaced after only 10 years, when the primary refrigerant-to-water heat exchanger developed a leak. It was replaced with a gas furnace. It also had an odd problem with plugging the water discharge line. It used well water, the same water we used for the household, and then discharged the water to a nearby lake. The discharge line plugged several times with some sort of black dirt like material. The good news was that the ground water-to-air cooling worked great, with Michigan’s 50 degree well water.
HEAT PUMPS ARE MONEY LOSERS IN MY VERMONT HOUSE, AS THEY ARE IN ALMOST ALL NEW ENGLAND HOUSES
https://www.windtaskforce.org/profiles/blogs/heat-pumps-are-money-losers-in-my-vermont-house-as-they-are-in
EXCERPT
Before HPs: I used 100 gal for domestic hot water + 250 gal for 2 stoves in basement + 850 gal for Viessmann furnace, for a total propane of 1,200 gal/y
After HPs: I used 100 gal for DHW + 250 gal for 2 stoves in basement + 550 gal for Viessmann furnace + 2,489 kWh of electricity.
My propane cost reduction for space heating was 850 – 550 = 300 gallon/y, at a cost of $2.339/gal (buyers plan) = $702/y
My displaced fossil Btus was 100 x (1 – 550/850) = 35%, which is better than the Vermont average of 27.6%
My purchased electricity cost increase was 2,489 kWh x 20 c/kWh = $498/y
My energy cost savings due to the HPs were 702 – 498 = $204/y, on an investment of $24,000!!
Amortizing Heat Pumps
Amortizing the 24000 – 2400 = $21,600 turnkey capital cost at 6%/y for 15 years costs about $2,187/y.
This is in addition to the amortizing of my existing propane system. I am losing money.
https://www.myamortizationchart.com
Other Annual Costs
There likely would be annual cleaning of HPs at $200/HP, and parts and labor, as the years go by.
This is in addition to the annual service calls and parts for my existing propane system. I am losing more money.
My Energy Savings of Propane versus HPs
Site Energy Basis: RE folks claim there would be a major energy reduction, due to using HPs. They compare the thermal Btus of 300 gallon of propane x 84,250 Btu/gal = 25,275,000 Btu vs the electrical Btus of 2,489 kWh of electricity x 3,412 Btu/kWh = 8,492,469 Btu.
However, that comparison would equate thermal Btus with electrical Btus, which all ethical engineers know is an absolute no-no.
A-to-Z Energy Basis: A proper comparison would be thermal Btus of propane vs thermal Btus fed to power plants, i.e., 25,275,000 Btu vs 23,312,490 Btu, i.e., a minor energy reduction. See table 1A. SEE URL
BTW, almost all RE folks who claim a major energy reduction from HPs, do not know how to compose this table, and yet they mandate others what to do to save the world from Climate Change.
Comparison of CO2 Reduction in my House versus EAN Estimate
My CO2 emissions for space heating, before HPs, were 850 gal/y x 12.7 lb CO2/gal, from combustion = 4.897 Mt/y
My CO2 emissions for space heating, after HPs, were calculated in two ways:
1) Market based, based on commercial contracts, aka power purchase agreements, PPAs
2) Location based, based on fuels combusted by power plants connected to the NE grid
See Appendix for details.
Outstanding analysis! Thanks!!
It is in the fine print of the spec, minimum guaranteed btu out at some cold(#) temperature.
When a contactor, realestate agent or some ngo does not provide when asked for, do not walk away, have them thrown in jail.
The author, Ron Barmby’s book, “Sunlight on Climate Change” is a good basic fact filled read….Historically, as an engineering student just out of high school, I once attended a guest lecture by Ron Barmby at U of C circa 1972. The man’s brilliance was evident even at that rather young age…he now fights CC stupidity…more power to him…
This author’s links to explanations of the Second Law of Thermodynamics are wrong. The Second Law of Thermodynamics applies to “isolated systems” only. His links say “closed systems,” which is incorrect. Some disciplines define a “closed system” the same as an “isolated system” in Thermodynamics. But the author’s first link defines a “closed system” the same as Thermodynamics does. The confusion regarding the Second Law and when it applies abounds.
closed vs isolated is contrived confusionism.
The 2nd Law *always* applies even if it *appears* not to as inside heatpumps, aircons and refrigerators
As per the ‘human body’ example: The human may appear to be a highly ordered ‘thing’ and its creation/existence has violated the notion that Entropy always increases.
But to do that, Entropy somewhere else has *always* increased.
That is why we eat/need food. The highly ordered thing in the sky (El Sol) creates order in the food and when we eat it we ‘steal’ that order.
But the trail of disorder we leave is immense = 4 million tonnes per second of ‘disorder’ in El Sol itself just for starters
Problem is and this was Carnot’s question: Where did the energy (Entropy) go?
It could be anywhere in the entire universe and to suggest that you know where it went by in closed/isolated systems is presumptuous and pretentious in the extreme
(Oh hello, I’ve just described the Green House Gas Effect)
It is the same presumption and self-declared cleverness that defines closed vs isolated systems
e.g. The Emperor is an ‘isolated’ system. He still has clothes but some smarty pants has hidden them. somewhere
The Second Law Is Very Simple:
All you need to know about the 2nd Law is that Heat Energy always goes down a thermal gradient and as the essay here explains, the rate of flow depends how steep that gradient is.
Heat pumps appear to make heat energy go up a thermal gradient but to do so requires they exert ‘work’ and that ‘works’ increases Entropy as some other (possibly unknown) place
What the essay tries to get across is that as the gradient steepens i.e. it when it gets really cold outside your house), the work you need to do to move the heat energy increases and hence the heat moving efficiency of your pump plummets
and just like the ever so beautiful theory of green house gases, water with its ugly phase changes, esp at Zero Celsius, rides a coach & horses through the whole thing.
ha ha ha
Huh?
It cost a lot to run a heat pump and it cost more the greater the (desired) difference in temperature is inside the house compared to outside the house.
Also, the house, any house, loses heat faster as the difference between the desired inside temperature and the actual outside temperature increases. At some temperature difference (cold outside) the rate of heat loss can easily be greater than the rate at which the heat pump can gather outside energy and transfer it inside so the heat pump cannot keep the inside warm enough for survival (without even more expensive resistance heating).
And the Second Law doesn’t only apply to isolated systems? I’m losing the linkage in your statement.
An isolated system is one where no mass or energy crosses the boundary of the system. Heat pumps are not isolated systems since energy *does* cross the boundary in order to run the compressor unit.
The 2nd law still applies to a closed system. You may have to analyze the system in pieces but it still behaves as the 2nd law says – entropy increases and in a cyclic process not all heat can be converted into work.
“The 2nd law still applies to a closed system.”
If this is true, then no closed system could cool down. Since that doesn’t usually happen, the 2nd law need not apply to closed systems.
A closed system that is constantly running doesn’t ever cool down. Open the air valve to the atmosphere on a simple air compressor and turn it on so it runs continually. Bet you the compressor will never cool down.
A combination of a heat pump and a natural gas furnace is a more efficient combination than a heat pump + resistive heat. The nat gas is burned at the point of use, rather than at a power plant miles away and then having the electricity transmitted with line losses of 15% – 20%.
The Second Law Is Very Simple:
“You can’t break even”
Jim says:”The confusion regarding the Second Law and when it applies abounds.”
Jim why does my thermodynamics book discuss heat pumps under the chapter on the Second Law?
I don’t know. Why does it? The units of entropy are energy per temperature–in IS units it is joules per kelvin. When heat energy leaves a system, it loses entropy. That violates the second law.
Jim is extremely confused about what the Second Law means, and how to apply it. Yes, as worded, it applies to closed systems, which in our universe can only mean “the entire universe”. However, although smaller (and not-quite-closed) systems are not “the entire universe”, all systems are subject to the same statistical calculations as the whole universe. In practical terms, this means that at any macroscopic scale, energy always flows from hotter objects to colder ones, for the same reason that the 2nd Law describes universal entropy as constantly increasing.
Jim oddly knows this fact about entropy when applied to individual objects, but somehow misses the connection to the 2nd Law. I don’t know how that works in his mind. He has never been able to explain the gap clearly. Confusion abounds, yes, and a lot of it seems to be in Jim’s mind…
I see that many here are ignorant of Thermodynamics.
The Clausius standard for the first law involving heat and work is:
dU = δQ – δW
where U is internal energy, Q is heat, and W is work. The sign standard is that heat added to a system is positive, and heat removed from a system is negative. Work done by the system is positive, and work done on a system is negative. U is a state variable which is why it’s a total derivative. The squiggly d’s mean that heat and work are path variables. They are also boundary values–no system contains heat or work.
Chemists use a slightly different version of the law:
dU = δQ + δW
Here, heat added to a system is positive and heat removed from a system is negative as before. However, work done on the system is positive and work done by a system is negative. So, pick a standard and stick to it.
There are three basic types of systems: open, closed, and isolated. An open system allows both energy and matter to cross the system boundary. A closed system doesn’t allow matter to cross the system boundary. An isolated system doesn’t allow either matter or energy to cross the system boundary. There are variations, of course. For example, an adiabatic system is a closed system where no heat crosses the system boundary.
The second law is simply:
ΔS ≥ 0
The Clausius definition of entropy for a reversible process is:
dS = δQ/T
where S is entropy, Q is heat, and T is the absolute temperature. Notice the since T is always positive, the sign of the entropy term follows the sign of the heat term.
So, if a closed system can lose heat, then the change in entropy is negative–which violates the second law.
Your statement that the universe is a closed system is wrong. The universe is considered to be an isolated system. In an isolated system, the entropy will increase until equilibrium results. At equilibrium, the change in entropy will be zero. All isolated systems tend towards equilibrium. It may take seconds, minutes, hours, days, years, or billions of years.
And that’s how the second law works in my mind.
Okay, so given that I should have said “isolated” instead of “closed” to describe the universe, that doesn’t change the rest of my point.
You have failed to explain how entropy can “dictate” that energy must always move from hotter objects to colder ones until equilibrium is reached, in a (more or less) isolated system, but that this entropic rule is somehow totally unrelated to the 2nd Law.
Jim, you say: ‘The Second Law of Thermodynamics applies to “isolated systems” only.’
HOGWASH!!
The 2nd Law is universal. That’s why it is called a “Law”. The equations are simpler for an isolated system, but it applies equally to closed and open systems – you just have to keep track of the various “flows” such as heat and mass.
Take the 2nd Law equation for a closed system with only heat transfers being relevant:
dS >= Sum(dQ/T)
where S is the entropy of the system, Q is the (signed) heat flow across the boundary of the system, and T is the absolute temperature of the system where the heat is flowing.
In an isolated system, there are no heat flows across the boundary, so dQ is zero, and this reduces to:
dS >= 0
You seem to think this simplified equation is a statement of the 2nd Law, but it is only a very special case. The 2nd Law still has a lot to tell us about what can and cannot happen in closed and open systems.
Okay, I found a source that I trust and you’re right. I quote: “The second law of thermodynamics for a closed system states that the total entropy change must be positive for an irreversible system and surroundings and zero for a reversible system and surroundings.”
Of course he’s right. Now that we have established what entropy and the 2nd Law mean, and how they still apply on sub-universe scales, let’s return to the original reason we brought this up, no more than a couple of moons ago.
Willis claims that power has been measured being developed from the colder atmosphere to the warmer surface of the Earth, via radiant energy, in longwave infrared wavelengths. Many of us told him that’s obviously false, due to the 2nd Law. You suggested to him that he should just point out in his defense that the 2nd Law doesn’t apply, because the Earth isn’t the entire universe. Would you like to retract this suggestion you made to him now?
Steve:
I’m afraid you are fundamentally confused about the 2nd Law as well. (In fairness, most people are!) The 2nd Law does not prohibit energy flows from colder to warmer, it simply requires MORE energy to flow from warmer to colder.
When dealing with radiative transfers, we speak of “radiative exchange”. This concept is presented in every heat transfer textbook I have ever seen, and I have looked at many over the years. They all show bi-directional radiant energy flows (multi-directional in more complex examples), with the warmer object emitting more power than it receives.
This is very easy to verify experimentally. Point a kitchen IR thermometer at the contents of your refrigerator, then at the contents of your freezer. Keep it at a sufficient distance from these that it is in ambient air (~20-25C).
The thermometer will report a higher temperature for the refrigerator than for the freezer, even though both are colder than the thermometer itself. How is this possible? How can it tell the difference?
The sensor in the thermometer has a higher temperature (and so has a higher electrical resistance) when pointed at the frig than at the freezer. This is due to the higher radiant energy flux from the objects in the frig, even though the radiant flux from the sensor to the frig is still greater than what it receives.
Now go outside and point the thermometer at the sky. It’s best to do this at night. You will get a higher reading when pointing it at low clouds than at clear sky. With clear sky, you will get a higher reading when the humidity is high than when it is low. These differences are from the differing intensities of the downward radiant fluxes affecting the temperature of the sensor. (Again, the flux from the sensor to the sky is greater, so there is no 2nd Law violation.)
Hi Ed, thanks for the posting. Radiative exchange at a quantum level is all well and good, but macroscopic classical thermodynamically measurable energy (i.e. work) cannot flow in two directions along a single entropy gradient at the same time. Doesn’t happen. Energy only flows *down* an entropy gradient. Never up.
You can draw imaginary photon arrows all day long, if it helps you to picture where there is energy (which as you’ll recall constitutes the potential to do work); but you can’t measure energy flowing in two directions (bidirectional work), because it doesn’t happen.
As an example, if you look up the concept of an “equilibrium photon gas”, you will see that in an equilibrium situation, there are photons (and energy) everywhere, but no power at all. The photon “gas” is described by the same characteristics as any other gas, namely temperature, pressure, and volume. Not power, though.
Remember, the standard way to teach the difference between energy and power is to encourage people to think of energy as being kind of like water. It is a “content” of something. It can sit there all day and never move, and there will be just as much of it at the end of the day as there was at the beginning.
But to get it to move somewhere, and do work, you need a hill, i.e. a gradient. This is similar to a river in the water analogy, and the rate of flow of the water represents “power”, i.e. the “rate of energy flow” or “rate of work”. It depends on the steepness of the hill, the size of the channel, etc. But rivers only flow in one direction in a given river channel. Not both directions. That is nonsense. If you measure the water flow downriver, you get a positive number; but if you measure the water flow upriver, you get a negative number. Both are equally valid, but it is still only one number.
If your heat transfer textbooks are showing you work being done in two directions along the same entropy gradient at the same time, they are lying to you. Two objects cannot both perform work on each other at the same time. What do you think “work” means? Perhaps you have misunderstood the diagrams… (and yes I know that Joule heating is not technically classified as “thermodynamic work” but is part of the category of thermodynamic processes; it doesn’t change the result, and you still can’t have two objects both Joule heating each other)
And no, IR thermometers do not demonstrate “bidirectional energy flow”. You have misunderstood how they operate. An IR thermometer contains a bolometer. This is a passive device that can tell you how much energy is being gained or lost via radiant exchange, an amount which varies depending on its own temperature and the temperature of its environment (the target you are pointing it at). (And that of course is what the S-B law tells us about every pair of objects.) So if you point the bolometer at a colder object than itself, it records negative energy flow, displayed as negative voltage, i.e. energy being lost. Instead if you point it at a warmer object than itself, it records positive energy flow, displayed as positive voltage. So the way the thermometer manages to display an absolute remote temperature is by computing the relative temperature differential from the measured power flow, via the S-B equation and some assumptions about emissivity and absorptivity. Then it adds its own internally measured temperature to give you (approximately) the absolute temperature of the target. You can verify this behaviour by taking one apart and measuring the voltage directly coming off the bolometer. You will see that if the temperature of the bolometer itself is increased, the voltage will drop, and become negative if the bolometer becomes warmer than the target it is pointed at, etc. It is a relative measurement, and naturally that is all it can be.
You should probably stop using terms like “radiant flux”, because photons do not “flux”, any more than waves on the ocean are “fluxing”. That is a term that the lying grifting climate “scientists” seem to have invented for their own purposes, and they use it to confuse you, rather than enlighten, so to speak.
Make sure you have a firm grasp of what a Joule is, both definitions, and what Joule heating means. Then you will know what a Watt refers to, and you will see that it is nonsensical to think of bidirectional Watts. Complete fiction.
You are right that there is a lot of confusion around this topic! But I am pretty sure none of it is on my part.
Steve, thanks for the response. However, it is so full of misconceptions that I feel I must respond.
First, you are fundamentally confused about the difference between “energy”, “heat”, and “work”. Your assertion that “macroscopic classical thermodynamically measurable energy” is “work” is just plain wrong. Likewise, your assertion that “energy” “constitutes the potential to do work” is also just plain wrong.
Consulting an old thermodynamics text (nothing special about it), the introductory chapter has separate sections for “Energy Transfer as Work” and “Energy Transfer as Heat”. The section on “Energy Transfer as Heat” starts out:
“We have discussed several means by which macroscopically observable work can be done on or by a system, causing its energy to change. However, it is possible to transfer energy to a system in ways which are not observable as macroscopic work.”
This second category is just called “heat transfer”, and scientists and engineers take great pains to distinguish it from transfers by work. I have taken multiple courses in heat transfer, at both the undergraduate and graduate levels, and never in these courses or their texts was it considered “work”. The statistical nature of both radiative and conductive heat transfer was emphasized as we got into depth.
You have to be very careful employing a water analogy. Early heat transfer analysis used the “caloric fluid” paradigm, which employed a water-like fluid for heat transfer. But that idea was discarded over 150 years ago. Still, superficial analyses treat the NET heat flow as comparable to a physical fluid flow. But these say nothing about the underlying mechanisms.
Let’s look at the IR thermometer/bolometer again. Here are two quick definitions for a bolometer: “A bolometer is a device that measures radiation by measuring the temperature of an object which is warmed by absorption of the radiation.” Also: “A bolometer is a device for measuring radiant heat by means of a material having a temperature-dependent electrical resistance.”
So the IR thermometer measures the electrical resistance of the sensor to get the sensor temperature. It is NOT getting a negative voltage as a function of energy loss, and a positive voltage as a function of energy gain, as you claim.
It does compare the resistance of the sensor to the resistance of a reference sensor not exposed to external radiation to calculate the temperature of the object pointed at. But the key point is that the sensor itself has a higher temperature when pointed at frig contents than when pointed at freezer contents. This is because the frig contents transfer more radiant power to the sensor than do the freezer contents. I emphasize that in both cases, the sensor is outputting more radiant power than it is receiving, in line with the 2nd Law.
You seem to think that the sensor reduces is radiant output when pointed at the frig compared to the freezer, and turns it off completely when pointed at a hot oven. What is the mechanism by which it modulates its outputs for these different cases? How does it “know” which it is pointing to?
Finally, you argue that the term “radiant flux” was invented by “lying grifting climate scientists”. Don’t be ridiculous! This terminology has been in use long before there were climate scientists — you seem to be completely unaware of this. (My complaint here is that they use “radiant flux” in cases where they really should be using “radiant flux density”, but that is a minor point.)
I have worked professionally in the optoelectronic industry, designing emitter/detector systems. We cared deeply about the radiant flux (and radiant flux density) from the emitter and to the detector. And this was in the days before climate science was big.
So yes, there is still confusion on your part.
Hi Ed,
Sorry I missed this post when I replied to Jim yesterday, it was not my intent to ignore you.
I’m pretty sure that as long as we are starting from the same axioms and using the same rules of reasoning and deductions, we had better arrive at the same conclusions. So let’s take a closer look at where the misunderstandings might be.
First, a misunderstanding on my part about the difference between a bolometer and a thermopile, of which the first operates by changing its resistance based on its temperature, as you described, and the second of which is the one that is used in pyrgeometers, and generates a positive or negative voltage based on whether it is gaining or losing energy. My mistake. I do believe IR thermometers use bolometers (microbolometers) instead of thermopiles, so they have to detect the temperature (or resistance) of the bolometer material, rather than measuring a voltage as in a thermopile.
However, that doesn’t change the fact that a bolometer (or thermopile) cannot gain energy from a colder object. Nothing can. That’s what the 2nd Law tells us. You just finished explaining that to Jim.
So in the IR thermometer, when you point the bolometer at a colder object, it loses energy, its own temperature drops below that of its “reservoir” (in handheld IR thermometers this will be the ambient temperature of the device, e.g. room temperature), and a loss of energy is measured. This is not the same as the bolometer gaining energy from a freezer! The thermometer electronics will then compare the bolometer’s energy loss (colder temperature) to its own ambient temperature, and calculate the temperature of the remote object as being colder. You can still perform the experiment I suggested: take the IR thermometer apart, and instead of measuring the voltage across the sensing bolometer (it won’t have any of course), measure its resistance. As the sensing element gets colder by losing energy to a colder target, its resistance decreases. (I am only about 80% sure of the direction of change of resistance with temperature in these particular devices, but most materials in common use in bolometers have a positive temperature coefficient of resistance, like most metals, so I think I’m on safe ground there, but if the direction is inverted it doesn’t change the argument)
So no, an IR thermometer does not “gain energy” from a colder object. It doesn’t need to in order to calculate that the colder target is actually colder.
Having gotten that out of the way, your other main objection seems to be related to the concept of “net heat”. But there is no such thing, as far as I have ever been taught. If you start from the concept of a Joule, there is no such thing as a “net Joule” or a “gross Joule”. There are only Joules. From there, we define “heat” as the movement of Joules, always from a hotter region to a colder one, of course. There is no “net”. Finally, we define “radiant power” as the rate of heating via radiation. There is no “net” there either.
And to clear up some last minor points, yes I know that energy is not the same as water, it’s an analogy. I am not stuck in the ancient caloric-theory-of-heat era. Perhaps I didn’t make the analogy part clear enough.
And the “radiant flux” term is still a bad term, regardless of who invented it. Radiation doesn’t “flux”, because that means “flow”, and photons do not “flow”. I can buy “radiant energy flux”, that makes sense. Just be careful not to assume that the shorthand term “radiant flux” (in Watts) implies that EM radiation has some sort of intrinsic power. It doesn’t. EM radiation is an energy phenomenon. Always has been, and always will be.
And energy is absolutely defined as the “potential to do work”. If you don’t buy that definition, what do you think energy is? From Encyclopedia Brittanica: “energy, in physics, the capacity for doing work”. It’s been defined that way ever since people stopped thinking of heat as an actual material.
Yes, I do also know that Joule heating is a different category of thermodynamic process than thermodynamic work. That doesn’t change anything I said about the direction of energy transfer.
Make sense? What part do you think I am confused about? Nothing I wrote here contradicts any experimental results, or our daily experience of energy and heat. Your claims, on the other hand, do.
Steve: Let’s focus on the IR thermometer pointed at the freezer and refrigerator.
First, let’s say it’s pointed at something at room temperature. The sensor is at the same temperature as the reference sensor, so has the same resistance.
(BTW, I’m virtually certain that the sensor is made of metal, so its resistance will increase with temperature. There are “negative temperature coefficient” (NTC) resistors, but they are a special beast — I have used them a few times to limit inrush current in “soft start” circuits.)
Now, we point it at the open freezer. We are agreed that the sensor temperature will be lower than the reference temperature, and this fact is used to report a temperature lower than room temperature.
Next, we point it at the open refrigerator. Again we are agreed (I believe) that the sensor temperature will be lower than the reference temperature, and so a sub-room-temp temperature is reported.
But for the thermometer to report a higher temperature for the frig than the freezer, the sensor temp must be higher than when pointed at the freezer. We know that these devices can accurately report these differences, but what is the mechanism by which this happens?
I say, in accordance with all my physics and engineering texts and references, that the difference is due to the fact that the frig contents are radiating more energy to the sensor than the freezer contents do. I emphasize that in both cases, the sensor is emitting more energy to the contents than it is receiving from them, so the “heat” transfer is from the sensor to the contents. But the closer the contents are in temperature to the reference temperature, the less the difference, and the higher the resulting sensor temperature.
This is where you obviously disagree with me. I have asked you what you believe the mechanism is for the difference in sensor temperature between the cases, but I have not gotten an answer. If you don’t think it is from the higher radiant energy from the frig contents, you must believe that the sensor radiates less to the frig than the freezer. What is the physical mechanism for this phenomenon, in your view?
Hi Ed,
As you described your example here, I believe we are in agreement on all points in that scenario.
Where we disagree, I believe, is in describing anything in this scenario as constituting “bidirectional energy transfer” (as opposed to presence), or in other words “bidirectional heating”. Those concepts do not follow from anything you wrote in this most recent example.
From all the physics I have studied, there is simply no such thing as “bidirectional heating” in which two objects can both “heat” each other (using the modern and precise definition of “heat”) at the same time. That is my disagreement. (But to make things as clear as possible, I re-iterate that you did not make that claim in those words in this particular case, only in earlier postings, so I don’t disagree with anything you wrote here.)
Steve,
You’ve obviously never opened a textbook on heat transfer, or you would not be making these claims. First of all, note the very title of the subject (both of the courses and the textbooks): Heat TRANSFER! (Not Heat PRESENCE.)
I had the chance today to peruse the library of a retired thermosciences professor at a major university – I occupy his office on days when I am teaching there. I picked up 7 heat transfer texts, and every single one introduces radiant heat transfer in the context of (bidirectional) radiative exchange.
Here is a link to a good free on-line text from MIT:
https://ahtt.mit.edu/wp-content/uploads/2020/08/AHTTv510.pdf
There is nothing unusual about this text, both compared to the others I looked at today, or to the ones I remember when I studied thermosciences at MIT many years ago.
Chapter 10 discusses radiative heat transfer. The very first section is: The Problem of Radiative Exchange. Just as I have been arguing. To clarify some terminology, let’s look at an early sentence in that section:
“Figure 10.1 shows two arbitrary surfaces radiating energy to one another. The net heat exchange, Qnet, from the hotter surface (1) to the colder surface (2) depends on the following influences…”
Note that it talks about “radiating energy” and the “NET heat exchange” that results.
I am still waiting for an answer to my specific question: If there is no exchange of energy in these cases, as you argue, why does the IR thermometer sensor have a higher temperature when pointed at the frig contents than when pointed at the freezer contents?
Hi Ed,
I have no problem with “arbitrary surfaces radiating energy to one another”. That’s certainly valid physics. But you don’t need the word “net” in a phrase like “net heat exchange”. The word “heat” is already defined to describe the rate of energy movement from one object to another, and as we know, at a macroscopic scale, that is always from hotter to colder. There is no “net”, regardless of what the engineering textbook says.
If you start inventing fictional macroscopic energy transfers from colder objects to hotter ones, and then arbitrarily increasing the energy flow the other way by the same amount to compensate, that just complicates things. Why would you want to do that? I say it’s unnecessary for exactly the same reason that if I were to give you one of my apples, there is zero reason to add “and you also gave me five more apples, and then I gave you five more of mine to make up for the five you just gave me”. Why would anyone say or do that? And why five? Why not five thousand, or five million, or negative fifty, or zero? They’re all exactly the same measurable result, which is what we’re all interested in, in the end. Right?
(This is not an unprecedented occurrence in engineering-textbook-land either, in case you are tempted to think that engineering textbooks are the literal word of God or something. Aeronautical engineering textbooks, for example, regularly make up fake and overly complex reasons for airplane wings to be able to generate lift, while the real reason is nothing more nor less than Newton’s third law.)
I described in more detail in my other answer below, which I posted a few minutes ago (sorry about the chronological/spatial inversion), how an object (such as a thermometer) can instantaneously “figure out” how fast it needs to lose energy to a colder object, without having to be constantly “gaining” energy (which would imply increasing its temperature) from that object at the same time. So I don’t think I need to repeat my description again here.
You’re misinformed. I have more affect on the Moon’s orbit than on what Willis believes or claims.
I’m not surprised that you did a victory dance. That’s about your speed. I am surprised that Mr. Bo didn’t do one too.
Are you still going to claim that the 2nd Law cannot be used to disprove the claim of a colder atmosphere heating a warmer surface, which is what the pyrgeometer scientists are claiming?
I’m still wondering why Mr. Bo isn’t doing a victory dance.
I think I broke his brain. He would have done one, but he’s simultaneously in shock from the realization that something else he thought was solidly true, for so long, turned out to be false – for exactly the same reason he just educated you about.
But Jim, you shouldn’t underestimate your own power and influence. It is indeed tempting to think that we are each just one man, and what can one man do against a seemingly overwhelming tide of bad physics? Nevertheless, if you join our small and disorganized band of indefatigable truth seekers, then not only have you denied the most influential fake physicist around here, Willis, one of his doses of adoration-induced dopamine, which his inflated ego so craves – but by rightly criticizing his errors instead, you can increase his irritation level too, making for a double-strength reduction in his motivation to post his nonsense. That constitutes two measurable improvements in the quality of WUWT discourse for the price of one man’s words. Furthermore, you can also do your best to educate other misinformed commenters (the small but noisy “Willis fan club”), thereby acting as a sort of “force multiplier” – which is what Ed and I have just accomplished here. (Mostly Ed, apparently, to be fair.) Anyway, welcome aboard! Cheers!
(I’ve been trying to straighten out DMacKenzie, another underqualified engineer pretending to be a theoretical physicist. But every time I get close to forcing him to admit to a contradiction in his beliefs, he would rather abandon the discussion than face the consequences of being wrong. It’s an uphill battle, yes, but a worthwhile one, in my book. I did get Ferdinand Engelbeen sorted out a little while back, too, after an extended physics lesson – but he doesn’t post here very much recently, that I’ve seen.)
Steve: The only thing that might brake my brain is figuring out how you can get virtually everything on this topic completely wrong. I notice that you have completely ignored all the points I made to counter your last post.
I’ll just follow up with this from Clausius, who did more than anyone to develop the 2nd Law:
”What further regards heat radiation as happening in the usual manner, it is known that not only the warm body radiates heat to the cold one but that the cold body radiates to the warm one as well, however the total result of this simultaneous double heat exchange is, as can be viewed as evidence based on experience, that the cold body always experiences an increase in heat at the expense of the warmer one.”
DIE MECHANISCHE WÄRMETHEORIE
von R. CLAUSIUS
1887
Clausius was using a very loose definition of “heat exchange”. These days we have a stricter definition, and we define “heat” as “energy that is transferred from one body to another as the result of a difference in temperature”. Of course, always from a hotter object to a colder one, as Clausius specified.
Colder bodies radiate energy, yes, but not heat, towards warmer ones.
Okay, let’s change the wording to the modern convention:
”What further regards heat radiation as happening in the usual manner, it is known that not only the warm body radiates ENERGY to the cold one but that the cold body radiates ENERGY to the warm one as well, however the total result of this simultaneous double ENERGY exchange is, as can be viewed as evidence based on experience, that the cold body always experiences an increase in heat at the expense of the warmer one.”
You say: “Colder bodies radiate energy, yes, but not heat, towards warmer ones.” What happens to this energy when it is absorbed by the warmer body?
Okay, that works better for me right up to this point (bearing in mind that this is no longer what Clausius wrote): “simultaneous double ENERGY exchange”
You will need to clarify what you mean by “exchange” before I can determine whether this statement is true or false (or meaningless) according to modern physics definitions.
For an example of what I mean by “clarify”, I can imagine that in your mind you might be picturing something like this: I have two apples, and you have three apples. I give you one of my apples, and you give me one of yours. We have “exchanged” apples. We both end up with the same number we had before (although a close inspection would probably reveal that they are not actually the same objects that we started with, but that is stretching the analogy farther than it needs to go). Is that how you are imagining an “exchange” of energy?
Steve,
Objects radiate as a function of their temperature and their material properties, but unrelated to what they might be radiating toward. (How would they “know” what is out there?) This is an absolutely uncontroversial statement.
So let’s take two objects at the same temperature with the same material properties (i.e. absorptivity/emissivity). They are exchanging photons and their energies at identical rates, just as if you and I were exchanging apples at identical rates, so they always end up with the same energy level they started with.
But if Object 1 has a higher temperature than Object 2, it will emit photons at a higher rate, so even though Object 2 is still transferring energy radiatively to Object 1, the next exchange is from 1 to 2.
And I am “imagining” nothing – this has been completely standard physics for a century now.
Ed, yes, objects radiate energy as a function of their temperature. That’s uncontroversial for sure. But be careful not to confuse energy with power (rate of change in energy).
Also be careful not to confuse quantum energy absorption or emission with classical thermodynamics. These are two separate realms, and you cannot use results from one set of laws to infer anything about the other.
So as long as you don’t try to claim that a hotter object is gaining energy (which means increasing temperature), at a classical thermodynamic level, from a colder one, I think we’ll be fine. That means you don’t get to draw arrows labeled in Watts pointing from a colder object to a hotter one. And still the IR thermometer will continue to work as expected.
And at risk of splitting a single conversation into THREE separate streams (ugh, sorry about that): you asked “What happens to this energy when it is absorbed by the warmer body?” A fascinating question, and I believe it is based on a misunderstanding of the word “absorb” (on your part). Remember that although radiant energy can be present, it will not be “absorbed” (perform work) unless the entropy gradient (2nd Law) says so. That means a warmer body will not in fact “absorb” (to the extent of increasing its own temperature) energy from a colder body. Does that help?
Steve,
You say: “it will not be ‘absorbed’ (perform work) unless the entropy gradient (2nd Law) says so.”
First of all, the energy transfer at absorption is not “work” according to the thermodynamic definition of work. But that is somewhat of a side point.
I keep asking: What is the physical mechanism by which an object detects whether the radiation is coming from a warmer body or a colder body, so it “knows” whether to absorb it or not.
To be more specific, how does the IR thermometer distinguish between a 15um photon coming from my body at 37C and a 15um photon coming from the freezer at -18C?
Also, what happens to the energy in the radiation that is not absorbed by the warmer object. The answer must be consistent with the 1st Law.
And, given your arguments, how does the IR thermometer discern the difference between frig temps and freezer temps?
Hi again Ed,
We need to be careful with words like “absorb” or “discern” because those are not thermodynamics terms with precise definitions. They are fuzzy colloquial English words that may or may not mean the same thing to you as they do to me, or any other physicist, especially when it comes to thermodynamics.
The physics reason why the rate of energy gain (or loss) between two objects depends (almost) instantaneously on both their temperatures has to do with the concept of “potential”. As I said before, energy is defined as the potential to do work, and objects radiate this potential at the speed of light. So if object B (maybe your fridge) is radiating a potential of +4 degrees C, and object C (maybe your freezer) is radiating a potential of -10 degrees C, then object A (let’s say it’s your room-temperature IR thermometer) will deliver a different rate of radiant power to each, depending on the potential it is working against. And then the thermometer electronics can measure the rate of energy loss (power) based only on its own bolometer sensor temperature, because the bolometer is arranged in such a way that its own temperature depends quite sensitively on this energy potential difference.
The whole process functions pretty much exactly like a river of water. If you have a lake high on a hillside, with a steep river channel going down the hill to a reservoir at the bottom, water will run very quickly down the channel, at all points in the channel. But if the hillside is replaced with a gradually sloping plain, water will then meander very slowly down the channel, again at all points from beginning to end. How does the water at the top of the slope “know” how fast it should be flowing? It can’t possibly know that until it gets to the bottom! Right? Yet somehow it knows anyway… and of course at no point would anybody say that there is water simultaneously flowing up the river, either, in order to “tell” the water at the top how fast to flow by bringing information “in person”, as it were, all the way from the bottom.
(Yes, I know that Joule heating is not defined as a category of thermodynamic “work”, rather it is a separate thermodynamic “process”, but as you said, I don’t think the difference is particularly relevant here.)
Steve,
I agree that we must be careful to use precise language in discussions like this. However, “absorb” and related terms (e.g. absorptivity) have very precise definitions. If a photon is “absorbed”, it is extinguished, and its energy (e = h * v) is transfered to the molecule that absorbed it. Completely bog-standard physics. No ambiguity here!
And I was careful to ask: “What is the physical mechanism…” to be precise in my language.
But I hate the use of “heat” as a verb in this area, because it is so imprecise. It was never used in my thermosciences classes. Does it mean simply to add energy to an object? Does it mean increasing the temperature of the object, or just reducing the temperature drop? There are a lot of stupid arguments resulting from this imprecision.
You say that: “objects radiate this potential at the speed of light”. No, objects radiate electromagnetic energy at a rate related to this abstract quantity known as potential. I have NEVER seen a single reference that claims a “radiation of potential” or anything like that. Can you point me to one?
When a higher potential is presented to a radiating object, how does it cause the object to reduce it radiative output?
The idea that heat flow is like water flow is just a metaphor. It is often convenient to think of it like liquid flow, but just because water flow is not comprised of counterflows tells us nothing about radiative heat “flows”. Similarly, we like to talk about magnetic flux (flux is just the Latin word for flow), but just because it is metaphorically similar to liquid flow does not mean that anything is actually moving.
But even if you use your metaphor, the higher temperature of the fridge contents relative to the freezer contents does cause a higher temperature of the bolometer sensor. Similarly, the higher temperature of the radiating atmosphere (effectively about -20C) compared to that of deep space (effective about -270C) does lead to higher surface temperatures than if there were no radiating atmosphere and the surface could radiate directly to the low potential of deep space. While you don’t agree with the underlying mechanism that many propose, your analysis does not disagree with their result!
Hi Ed,
I think we’re pretty close to the same interpretation of experimental results, and I would certainly hope that your view involving extraneous “gross” (?) energy flows would come up to the same repeatable experimental results as mine that doesn’t. That seems to be the case, fortunately.
So to try to clarify my statements, when I said “objects radiate this potential at the speed of light” and you said “No, objects radiate electromagnetic energy”, this is the same thing. We already established that energy is defined as the “potential to do work”. So when I said “radiate potential [to do work]”, that is the same as “radiate energy” (at the speed of light, for whatever medium you happen to be in, etc.)
We probably don’t need to worry about the analogies to liquids any further at this stage. They are just analogies to try to aid visualization of abstract concepts.
The main point of differing views seems to come from your engineering textbooks which show multiple energy flows (power) in different directions at the same point in space and time. I object to this description as being physically incorrect, and unnecessarily complex involving fake power flows. No one needs more complexity in their life than they already have, least of all me.
I say those things because my understanding of the Maxwell electromagnetic field equations combined with the closely related Poynting vector tells me that at any point in space and time, not only does the E-M field have a single density value (well, one each for electric and magnetic fields), but the Poynting vector at that location (direction of energy flow), which is basically the 3D spatial derivative of the Maxwell field equations, as far as I can tell, also has only a single value. This is all I am trying to say. So if your good friend the engineering professor doesn’t know how the Maxwell equations and Poynting vector work, maybe you could wander down the hall to the office of his friend the theoretical physics professor, and ask that fellow whether he thinks the Poynting vector can have multiple values at a given point in space and time.
To relate this description to your IR thermometer and fridge/freezer, the IR thermometer is basically measuring the magnitude of the Poynting vector at its location, in the direction you are aiming it. (Pyrgeometers do the same thing, with a slightly different technology.) But that vector is composed of the derivative of the universal electromagnetic field, which includes contributions from the fridge, the freezer, your body, the rest of the room, the battery in the IR thermometer, and everything else you can see in the entire past light-cone of your current location in the universe. It’s a complex field, by all accounts, but the main active contributions will be the ones from localized disturbances from the room’s equilibrium – so depending on what is going on in the room, the fridge and freezer will be prominent, along with your body producing heat energy. (Maybe the stove too, etc) Measuring the Poynting vector is a local operation, because the E-M field emitted by the objects you are measuring propagates energy (a potential) at the speed of light to your measuring device. But that’s not the same as energy flowing (being transferred) to your measuring device in your example. Energy only flows the other way – because that is the direction of the Poynting vector at the location of the thermometer.
So you can draw diagrams with objects emitting energy, the potential to do work, in all directions, measured in Joules (or degrees) – but Watts (transfer of energy) only happens in one direction at any given point. Make sense?
Steve – No it doesn’t make sense! I have several issues with your arguments.
First, it ignores all of 20th century physics. We understand now how molecules emit photons and how they absorb photons. We know very precisely the energy carried by each photon. We can calculate the photon flux through an area and therefore the energy/power flux. (Power is just the rate of energy transfer, so power flux is the rate of energy flux. And energy transfer is most certainly a flux, not a potential.)
With solid-state sensors, we know we are detecting the absorption of actual photons, even when the sensor is also emitting radiation. I’ve designed some of these sensors.
Yes, these fluxes create an EM field with singular properties at each point in space, but that does not mean those fluxes are not real.
Consider a dark room with a flashlight shining a beam of light across the room. You can put some sort of sensor in the beam and get information about the beam. You can even use that information to calculate that abstract entity known as the Poynting vector.
Now shine another beam, perpendicular to the first and intersecting it. Put your sensor in the place where the beams intersect, and you will get different results. You can calculate a different Poynting vector with a different orientation. But it would be patently absurd to say that the two flashlight beams do not exist!
Now orient the two (identical) flashlights so they are pointing directly at each other. A sensor in the middle of these two equal and opposite beams would yield a zero-magnitude Poynting vector. You would conclude from this that there are not two flashlight beams!
In reality, all you are doing is calculating the net result using an alternate method, and at a different point in your analysis.
Trying to use “photons” as the transport for energy risks losing sight of the inverse square law. Most people think of photons as “bullets” and the flux produced is constant no matter how far you are from the source. In truth those “photons” are nothing more than packets of energy propagating as an EM wave. The number of packets per unit m^2 goes down as the EM wave front propagates outward and goes down according to the inverse square law.
This is why Planck used the steradian in his treatise on radiation. The surface area of a steradian goes up as the distance from the source grows. The flux in that surface area are stays the same because the m^2 value goes up.
I’ve never been satisfied with the way climate science handles radiation. The amount of energy a single CO2 molecule can see goes down by the inverse square law as the altitude of the CO2 molecule goes up. Since the density of CO2 goes down as altitude goes up, less and less radiation headed for space is absorbed by CO2. This leads to the conclusion that most of the impact of CO2 on thermalization of the atmosphere will happen within 2 meters of the surface and that re-radiation of absorbed energy by CO2 will be more likely to escape to space as altitude goes up.
I’ve never seen this discussed in any climate science articles I’ve seen.
I think you’re right, Tim, the treatment of E-M radiation by climate “scientists” is atrocious. They’re clearly not physicists. I think their problems are bigger than just not taking the inverse square law into account. They make up fake power flows all over the place, and pretend that they’re real. Much like Ed’s heat engineering textbooks do. It seems like they fundamentally haven’t grasped the difference between energy and power, or what E-M radiation actually is.
Tim,
The intensity of the radiation from a POINT SOURCE decreases as the inverse square of the distance. However, when you analyze the radiation from a large planar (or even pseudo-planar) surface, all the “spreading out” from each point on the surface fundamentally cancels out, and the intensity does not decrease with distance from the plane, except around the edges. So for distances that are small relative to the size of the plane, the intensity can be well calculated as not decreasing with distance.
My heat transfer texts of full of tables and equations for handling these edge effects. But remember, the earth’s surface has no edges.
This analysis is the same whether you treat the radiation as continuous waves or discrete photons.
Even allowing for the curvature of the earth, the cross-sectional area of a vertical column is only 0.3% larger at 10 km altitude than at the surface.
If you want to understand better the absorption and re-emittance of radiation in the atmosphere, I suggest you go beyond articles and get a serious book. Grant Petty’s “A First Course in Atmospheric Radiation” is a good place to start.
Hi Ed,
As far as I can tell, nothing you said contradicts what I said. I think one way to describe our different approaches to this situation is that I view the universe as doing the sums of all the interacting E-M fields for me, and you want to calculate the pre-summed (fictional) values yourself, then do your own sums. That’s fine, and you’ll get the same answer the universe does on its own.
But the reason I say those pre-summed values are fictional is that you can’t measure them with any sensor. They don’t exist, in any normal sense of that word.
You think of the Poynting vector as an abstraction, because you apparently think of the components as real. I view the Poynting vector as the real result of all the components interacting, while the components themselves do not “exist” independently. You can tell, because you can’t measure them. (Measurement is the same as doing work.)
In your flashlight example, when you have two beams, you can measure the sum of the beams, for sure. But you can’t measure their individual contributions, unless you turn one of the beams off, which is now a different energy field than the one you had before.
No, I’m not ignoring a century of physics. I view the universe as a single wave function, an entirely standard view, therefore as a single E-M field (also full of various fermions and bosons and whatnot), which can obviously only have a single direction of energy flow for a given frequency at a given point in space-time. Not multiple directions simultaneously. That would be schizophrenic. It is exactly the same situation as figuring out which direction the water in a river is flowing. It is only flowing in one direction at any given point, governed by the slope of the channel at that point. There is no fictional “uphill” flow that needs to be subtracted from the much larger and equally fictional “downhill” flow to get the “net” flow that you can see and measure.
So can we agree on a description that works from both a theoretical physics perspective and a heat engineering perspective, something like this: components of the universal field would produce radiant energy flows (power) by themselves if they were the only object in the universe, but since they aren’t, these hypothetical power flows in your diagrams are only fictional intermediate steps on the path to calculating the real (what you call “net”) energy flow (or power) at any given point in space-time? Which is described by the Poynting vector at that point?
The practical application of my explanation is that not only are you doing your calculations in a different order than I am, but I am suggesting that you could do the calculations the same way the universe does: by working out the strength and slope of the energy density field at the point you are interested in, and then calculating the resulting power in a single step.
Your way: the fridge would develop 300 W/m^2 onto its surroundings if it were the only object in the universe, and if the surroundings were at a temperature of 0 K. The bolometer would develop 350 W/m^2 onto its surroundings if it were the only object in the universe. Add these up, and the bolometer actually loses 50 W/m^2 to the fridge. (Repeat with a lower temperature and higher resulting power for the freezer. These numbers are only rough guesses, the precise values don’t really matter here)
My way, and the universe’s way: the bolometer experiences an instantaneous and local energy/temperature gradient calculated as follows: 293 K (its ambient temperature, maintained more or less constantly by its internal thermal store) to 277 K (the fridge’s temperature, to which the bolometer’s low-heat-capacity sensing element is exposed directly via a radiative pathway with minimal intervening obstacles, e.g. air), resulting in something like 50 W/m^2 lost, i.e. the Poynting vector, via one calculation pass through the S-B radiant heat transfer equation.
Make sense? The reason I and every other theoretical physicist would prefer the second description is that it does not involve those intermediate fictional energy flows/power that you can’t measure with any instrument. Both will give you the correct answer, though, as you said.
Steve,
You say: “But the reason I say those pre-summed values are fictional is that you can’t measure them with any sensor.” As opposed to your handy-dandy Poynting Vector sensor, which directly measures the vector, I suppose.
An excited molecule from Object A emits a photon as it transitions to a lower-energy state. The photon, which has a definite energy, travels for a distance, and then is absorbed by a molecule in Object B, raising its energy level by this same level of energy.
Meanwhile, an excited molecule from Object B emits a photon as it transitions to a lower-energy state. The photon, which has a definite energy, travels for a distance, and then is absorbed by a molecule in Object A, raising its energy level by this same level of energy.
Of course, in a real example, there are huge numbers of photons going from A to B, and B to A. And each one contributes to the resulting EM field between the objects. But it is ridiculous to assert that it is wrong to talk about separate fluxes of photons and their resulting energy and power fluxes. (Power is just the rate of energy transfer. It can refer to individual component of the transfer, or to the combined result of multiple transfers.)
You make a big deal of the fact that we cannot directly measure an individual energy/power flow, concluding that these therefore do not exist. But all measurements are at least to some extent indirect, including those from which you derive your Poynting vector.
My tire pressure gauge cannot directly measure the absolute pressure inside my tires, because it can only compare it to ambient. So I cannot use it to make any inference about the absolute pressure?
The downwelling infrared radiation from the atmosphere can be and has been measured with supercooled sensors, which come very close to measuring the absolute flux you talk about. And they confirm the “indirect” measurement of sensors at ambient temperatures (analogous to my tire pressure gauge).
Many years ago, a University of Chicago physics professor consulting for my group, told us that a good theory should work when looked at in multiple different ways. This is one such case. The analysis that uses multiple separate radiative power/energy fluxes, then computes the net result of these fluxes, gets the correct answer, and the same answer as computing the (net) field first. It is also very much clearer as to the issues of causality.
Hi again Ed,
“Poynting Vector sensor” -> i.e. a bolometer or a thermopile, yes. That is what we are discussing.
“An excited molecule from Object A emits a photon” -> no, we are not talking about quantum mechanics here. We are talking about classical thermodynamics. They are separate worlds, and you cannot infer the behaviour of one from the rules governing the other. For instance, a single photon does not carry “Joule heating” within it. It contributes to mediating the process, in the same way that a sloping river bed allows water to flow along it (but only in one direction), or a lake surface allows wave energy to propagate along it. Water surfaces do of course allow waves to travel in multiple directions at the same time, and the universal E-M field allows photons to propagate in multiple directions at the same time too. But the macroscopic measurable flow of energy only happens when the “lake bed”, or “river bed”, is slanted. That represents a temperature or entropy gradient.
“supercooled sensors” -> this scenario changes the energy field (gradient) being measured. So the result is not comparable to the result you get from ambient-temperature sensors. It is like measuring the distance from your head to the floor when you are standing directly on it, vs. measuring that distance when you are standing on top of the Eiffel Tower. You will get a different (and much larger) number, and if you tried to claim that your resulting measurement showed that you were actually 332 m tall, people would laugh at you. And rightly so. (The tower’s height is listed as 330 m, and I am guessing that your actual height is around 2 m, that’s where I got 332)
“University of Chicago physics professor” -> did you ask him whether it is possible for two passive objects to perform Joule heating upon each other at the same time, the way your heat transfer diagrams claim is the case? (He will say “no”, of course, because colder objects do not perform Joule heating upon warmer ones – and you should definitely ask him this question when you get the chance)
As I said earlier, you will still get the correct answer by fabricating these fictional power quantities and summing them. But bear in mind that they are fictional. They do not represent real, i.e. measurable, energy flow. You could, for example, measure your height by standing on top of the Eiffel Tower, measuring the distance to the ground, and subtracting the height of the tower, too. But why would you do that? And even more oddly, what you are actually doing here is more similar to pretending to dig a 300 meter deep hole, pretending to stand in the bottom of it, pretending to measure the imaginary negative height from the top of your head to the surface of the imaginary hole, and then adding the total height of the still-imaginary hole. Quite bizarre, to my mind.
My father is a retired university physics professor himself, so I grew up living and breathing this stuff, and it is second nature to me. You, on the other hand, have invented some kind of fake physics from the dumbed-down diagrams in your heat transfer engineering textbooks, which is a very unreliable way to make up a branch of physics. I recommend sitting down with some theoretical physics textbooks, working through all the exercises, and gaining a deep-seated intuitive sense of how classical “energy” and “power” work. Then proceed to learn quantum mechanics, and then the highly counterintuitive relationship (or lack thereof) between those two worlds. It isn’t what you seem to think it is.
What happened, Ed? Did you run out of fake “rebuttals” to my physics lesson? Did I break your brain, yet?
As far as your last point, about fake power flows and causality, which I didn’t really address previously, it is quite a strange thing for a physics professor to say. Are you sure he said “if you can’t follow the causality, just assume that the environment is at a temperature of 0 K, and then everything will make sense”? In those words? Maybe you misinterpreted his actual statement?
He is right that a good theory should work when looked at from multiple angles, but the only angle from which your fake power flows look “good” is “it helps us to simplify our computations”. That’s really not a great angle from a theoretical physics perspective, to put it mildly, although I can see how engineers can appreciate it.
(There is no “net field”, there is only the actual field… and it’s not just a question of terminology either. Things you can measure are real. Things you can’t are, well, fictional. Made up. Invented. All in your head. The components you use to derive these “gross” fields are not even well-defined. They are built on imaginary assumptions, and therefore one “gross” field is just as good as any other. That’s how you can tell [besides the fact that you can’t measure them, of course] that they don’t actually exist. How, indeed, does the arbitrary assumption that “the environment has a temperature of 0 K”, which is the one your “gross” flows are based on, improve your understanding of causality?? Why not assume that the environment is 3 K, or 293 K, or 5000 K? All of them will give you the same answer in the end, so why did you pick 0 K?)
But whatever floats your boat, really, in the end, I suppose! As long as you stop claiming that any of these fake flows are real, I won’t argue with your computation techniques.
Steve,
Let’s see… You assert that a colder object radiates energy (potential) toward the warmer object, which sets up an EM field that prevents the colder object from radiating heat (energy) towards the warmer object.
You say this means “you don’t get to draw arrows labeled in Watts pointing from a colder object to a hotter one.” But YOU claimed this existed!
You agree that “objects radiate energy as a function of their temperature.” But you can’t wrap your head around the idea that the power output is simply the rate (time derivative) of this energy output. If there is energy output, there MUST be power output.
You also make the ridiculous assertion that one should not “confuse quantum energy absorption or emission with classical thermodynamics”, that “you cannot use results from one set of laws to infer anything about the other.”
Only our blog host’s desire for decorum is limiting my reaction to this assertion. It’s like arguing that we mustn’t use the results of DNA analysis to infer anything about Darwinian selection or Mendelian genetics.
The 2nd Law is a statistical phenomenon. You cannot really understand it until you get down to the molecular and quantum level and apply statistical mechanics analysis. This analysis explains why we see the macroscopic effects we do. The macroscopic (classical) effects are simply the grand sum of all these quantum molecular effects. And that is why I (still) say that you are ignoring basically all of 20th Century physics.
I have been trying to apply your analysis to real-world complications such as the cases where emissivity/absorptivity vary with wavelength or angle. I’m not making much progress. (By the way, your analysis says that Kirchhoff’s radiation law — absorptivity equals emissivity — is nonsense.)
There is no point in continuing this any further. I have reluctantly come to the conclusion that you are just another “Poynting vector fanboy”. I had hoped for more.
“. . . for exactly the same reason he just educated you about.”
You should reread my quote again. Whenever you include the surroundings to a system, then you’re dealing with an isolated system.
Yes, when you have more than two bodies that you are considering, one of which may be “the environment” or “surroundings”, you need to include its temperature in your calculations. But when we are dealing with IR energy being transferred from the earth’s surface to the atmosphere or vice versa, there aren’t a lot of significant 3rd parties in the exchange. There are minor ones, but nothing that affects the overall direction in the general case. All the pyrgeometer scientists agree about this, and you can verify it yourself if you wish.
When you have more than two bodies, you should call the police.
“Reversible processes actually do not occur in nature.” “…all the processes occurring on nature are irreversible.”
But reversible processes are useful tools for solving problems in Thermodynamics.
Very nice.
Have two reverse cycle air-conditions in my house, one in the lounge, one in the study.
Was so good to have them running on the few 35C+ days we have had recently! 🙂
ps. 35C is not an unusual summer temperature around this area.
Only had one day up near the old 100F mark.
The problem this year is the regular rain, combined with the warmth and the grass is growing like crazy..
ugh.. more mowing to do. !!
When flying as a flight instructor in the Florida Panhandle and the OAT (outside air temperature) was 30C+, I knew there was going to be a lot of sweating.
Under a law being considered by the UK Parliament, this article could get the author a 500,000 pound fine and 2 years in prison. Is there any ex post facto protection in the UK?
https://wattsupwiththat.com/2024/02/16/ndp-anti-fossil-fuel-advertising-draft-legislation-worthy-of-both-the-1956-soviet-rsfsr-criminal-code-or-the-other-end-of-the-political-spectrum/
And so when appearing in court, under oath, promising to tell the truth,the whole truth and nothing but the truth, you get yourself deeper and deeper in the proverbial shit, are instantly bankrupted and have no place to go other than the one they send you to.
Liberals seem to love that kind of natural injustice until opponents get the chance to use it against them and the penny drops.
Cannot wait to see how the UN, WHO etc cope when push comes to shove and the victims bite back.
Don’t forget the World Meteorological Organization which redefined “climate” to be only 30 years now instead of the the thousands to millions of years it was before.
“Under a law being considered by the UK Parliament,”
No Andy; I think you mean Canada
https://www.parl.ca/DocumentViewer/en/44-1/bill/C-372/first-reading
“(a) on conviction on indictment to a fine not exceeding $1,000,000 or to imprisonment for a term not exceeding two years, or to both”
OK Canada, but the mind set seens to be found everywhere in the once free west.
Some UK parliamentarian was recently pushing for a punitive response to unfavorable news about EV vehicles and for deliberate lies from the government in response.
From Germany “Those Who Mock State, Must Have To Deal With Powerful State”
https://notrickszone.com/2024/02/16/germany-moving-to-authoritarianism-those-who-mock-state-must-have-to-deal-with-powerful-state/
I’ve seen statement, but no legislation as far as I know, from a few US legislators saying “climate deniers” should face criminal charges and even the death penalty.
It’s not being considered by Parliament, it is a private members bill which, in order to be considered must appear on the order paper. Private members bills die quiet deaths in back rooms and rarely, if ever, make it to the order paper
Ok, so I don’t know how the British system works. The point is not how the system works, the point is that people who are supposed to be reasonable and responsible and working for everyone are mad men and women working for something very unreasonable – and this one incident is not an isolated thing but one of too many destructive things eating at the inside of society.
The Internet makes once crazy things easy to do now.
There is no such law being considered by the UK parliament. The linked article describes a private members bill from a Canadian politician. The bill is tabled, but the Canadian Parliament is not debating it.
I live in Central Florida, near the Gulf of Mexico. The outside minimum temp seldom is below 40 degrees F. My only alternative to a heat pump is electric heat. I’ll keep my heat pump, thank you very much.
They can make economic sense in such climates .
Certainly, they are better than nothing when better alternatives are just not available. Where I live now, there is no natural gas. Propane is available, trucked in a long distance and thus significantly more expensive than it is in many other places. However, I could never afford to purchase and install a large propane tank plus all that is necessary to bring the propane into the house, plus modify the house that doesn’t provide for any place to burn anything bigger than a candle (there are no forests with hundreds of miles, this is a desert) so a heat pump or resistive heating is the only option. Temperatures drop to around 20F fairly often in winter.
yeppers, Russell…you are in the “climate” that the heat pump is designed for and works best. Up here in the Panhandle we see 30’s and 20’s a lot, and then our heat pumps have to use the back up resistive heating elements and our electric meters go into overdrive, heh heh. Of course, we like our gas for other things like cooking and heating water.
And there’s these things called hurricanes, and when wind dies down we can have nice shower and then heat up stuff from the reefer. Don’t need the BBQ propane.
As an aside, if you do not have a gas water heater and you lose power for days, you can buy a 1 gallon plastic jug of water and leave it in the Sun for 3-4 hours, It gets very warm so you can have a nice shower at the end of a long day.
If use solar walkway lights, you can bring them in your house at night so no need for candles or flash lights. Put them out in the morning to recharge and do it again at night.
Been there, done that Tom. Restoring my folks’ home a bit west of here after Katrina I grabbed a few walkway solar lights leaving the Panhandle and used them for reading after it got dark. No electricity for almost 5 weeks I am dead set against candles, so it’s either those things or batteries.
There are a good many days here when the only sunlight comes through heavy clouds and the breeze makes one think the temperature is well below freezing.
“If use solar walkway lights”
Such an obvious solution to a problem! Embarrassed to have not thought of it. Thank you!
I live in Venice, a mile from the Gulf. When I replaced my A/C I decided on the electric heat strip over the HP due to ROI. The HP was more expensive and since I rarely use heat, the heat strip has little effect on my electric bill.
Also, if the refrigerant cools the outside unit below freezing when the air is above freezing, water vapour in the air will freeze and ice up the unit. The heat pump will stop working.
It will ice up when the outside air is below freezing too – just like frost forms on cars, grass, etc.
So the heat pump goes through a defrost cycle, much like “frost-free” refrigerators. Not a big issue, but it does cut into the efficiency somewhat. Note that as frost forms, that releases heat which is taken up by the heat pump. In drier air, the outside air will be chilled more by the heat exchanger.
Ric,
Many years ago I was involved with creating a solution for a municipal pool that had several large heat pumps as the water heater. Without fail, the heat pumps all iced up when the outside air temp fell below +5 degrees C. In operation, the refrigerant coil temperature was below zero and it firsty condensed the water from the air, that same water then dripped onto the frame of the unit and froze where it landed.
Within 30 minutes of freezing commencing the units were a solid block. Defrosting then started and ran for over an hour. During this time the unit was in reverse cycle, taking heat from the pool to melt the ice. And as you might have noticed, the hour to melt is longer than the half hour to start the freeze. In summary, the pool gets cold when the outside air temp gets below +5 degrees C.
My very quick fix to allow lower temp operation was to fit an exhaust hood on top of the unit to force the exhaust, chilled air up and away, (2m up and with upward velocity), from the intakes, this prevented the air intake to the HP from breathing previously chilled air.
The pool then heated down to +2 degrees C. It doesn’t sound like much but for large areas in Oz, the overnight temperature often gets to +3 or +4 degrees but rarely down to +2 or lower. I call it a cheap win for just a couple of hundred dollars of shiny metal sheeting.
Defrosting, without a sensible heat source, (like resistive heating), is a very poor solution when using a HP for heating. And for the pool, it would have been better to just drop a dozen kettle elements into the deep end and switch off the HP, (as originally supplied).
The main problem with heat pumps is that they’re in the wrong location and so very commonly also air conditioners.
If you design a heat pump to ONLY be a heat pump and then build structures so that losses from the living space can then be scavenged BY the heat pump you’ll actually get a system that is very efficient and effective… but for some reason people are installing them in places that have the least amount of available heat like at ground level, in the shadows by sources of moisture instead of inside the peak under the external layer of insulation at the top of the structure of a home…
it is simply a lack of basic knowledge of application, not of how they work. I’ve got a portable dual mode air conditioner that claims it can produce 1000 more BTU as a heat pump than it can remove as an air conditioner and I find that absolutely laughable – the damned thing will freeze up if I make it suck on its own exhaust hose! I found the best way to make it work in the winter in Florida is to put a 60 watt incandescent ‘trouble light’ in the intake tube. One would think that it’d work awesome, but it doesn’t. It literally produces more heat if I take the hoses out of the window and aim them up inside the room and let the 450 watts it consumes be efficiently vented into the room.
At least its big enough the cats can’t knock it over 11 times a night.
Quite correct that the proper application for a heat pump would be quite beneficial.
The large problem with many (most!) articles concerning heat pumps is they never specify just which type of heat pump is being discussed. It’s quite like stating EVERY motor vehicle on the roads is powered by gasoline.
Just like in this article we have to assume that the author is discussing air heat pumps only. Heat pumps have 3 major heat sources: Air heat pumps being the most common as they use the ambient outside air as their heat source, lesser known are the water heat pumps that use a pond or stream as the energy source and then the ground source heat pumps that use the almost constant temperature underground.
Another item is that many are simply assuming is that a heat pump is a direct replacement for whatever type of heating/cooling system currently in use.
For most people, temperatures of –20°C are never encountered; for many others it’s rare, and the cost of occasional resistance heating is small. But if it really is a problem, you have to look for an alternative heat source; ground, or water if you can.
Dear Nick Stokes,
Do you really believe this carbon dioxide stuff or have you become a bit like a priest having to keep up the belief in God pretence?
Altipueri – David Tallboys
This post is just about more efficient heating. Heat pumps provide it.
Except that, as the article makes clear, in quite common conditions (10°C is common even it warm places like Canberra), it costs twice as much to heat a house with a heat pump as it does gas.
Guess Scandinavians have too much money, or they are stupid. But don’t let reality interfere with an article that tells you what you want to hear 😀
In the UK over 22m of the 28m homes are on the gas network.Gas costs 7.42p per kWh whereas electricity costs 28.62p per kWh almost 4 times as much.
Then there is also a standing charge of 29.6p per day on gas and 53.4p per day on electricity.
Plus the UK has some of the oldest housing stock in the world and installation of heat pumps also requires considerable expense on insulation and larger radiators.
These facts are a major reason people are not switching to heat pumps and the government target of 600,000 installations a year from 2028 will never be reached. In 2023 for example only 20,000 heat pumps were installed.
Not forgetting the cost of the heat pump.
“it costs twice as much to heat a house with a heat pump as it does gas.”
Not in Canberra. The article says heat pump should be 4x more efficient than resistance heating. But where he lives, gas is 1/9 the price of electricity per J. But in Canberra, gas is only half the price, so heat pump is a good deal.
But what about the cost of the heat pump?
Please answer the question I asked you.
” Do you really believe this carbon dioxide stuff or have you become a bit like a priest having to keep up the belief in God pretence? ”
David Tallboys
More efficient or just more economical than resistive electrical heating?
Maybe more efficient than gas but definitely significantly more expensive.
Nick,
in common with many, many people you believe the fallacy of heat pump efficiency.
Firstly no device can put out more work than the energy applied, (basic school physics) i.e. talks of 200, 300 or 500% efficiency is simply false.
The heat pump industry use Coefficient of Performance based on electrical input to heat output. This cannot be used as efficiency unless only comparing with other electrically powered heating systems.
The simple reason is that the energy, which is the base for true efficiency, used to make the electricity and the losses between generation and the heat pump are significant.
Using the better system, ground source, giving a CoP of 5 means that there must be more than 5 units of electricity generated so as not to provide the equivalent of perpetual motion, i.e. efficiency over 100%. This translates to more than 80% loss between fuel and heating.
Take it one more step and use an air source at 3 CoP this now calculates at a true efficiency of 60% or less, not very good I think you must agree.
My only rider on the above is that depends on the validity of heat pump industry figures, which must be accurate?
“Firstly no device can put out more work than the energy applied, (basic school physics) i.e. talks of 200, 300 or 500% efficiency is simply false.”
You nailed it. You cannot calculate the efficiency of a system unless you consider *all* of the system. For heat pumps that includes the electrical generation and transmission of energy. It’s like calculating the efficiency of a car air conditioner without considering the fuel (and other consumables) used to drive the air conditioning system.
But at what capital cost?
Nick,
you should try moving to Alaska before you say -20°C is rare.
Most people live in warmer climates.
Yes… People do definitely prefer “WARM ”
You just destroyed the whole AGW scam in one post.. Well Done. !
About 500,000 die each year from heat-related causes compared to 4.6 million that die from cold-related causes each year. The cold or cool air causes our blood vessels to construct in our lungs to conserve heat and this causes our blood pressure to rise causing increased heart attacks and strokes in the cooler months.
https://www.thelancet.com/journals/lanplh/article/PIIS2542-5196(21)00081-4/fulltext
We have heated buildings, warm clothes, and heated transportation to shield us from the cold outside the tropics.
Either you didn’t read the article or you didn’t understand it, probably the latter.
The author didn’t even get into what happens if the outside evaporator is cooled below freezing in air that has any moisture. When that happens ice forms on the evaporator and acts as an insulator thus restricting the amount of heat transfer from the outside air to the refrigerant. If it remains in that condition for a long enough period you can induce a total freeze-up for the unit. In simple terms the efficiency of the unit goes down as the unit temperature goes below freezing. The trigger point is not -20C but 0C. The efficiency will drop below 100% at 0C in actual, real world operation and will actually drop to zero if a complete freeze-up of the evaporator unit occurs.
It’s really no different than the air conditioner in a vehicle. Set it to cool inside air only and at some point the unit will freeze up and the efficiency drops to zero. It can happen in a conventional air conditioner in a house if the input air is restricted by a dirty return air filter.
Define ‘”most”, Nitpick.
And those alternatives are free, right? It’s not economically viable for most people.
If I were building a new home, I’d use a ground loop heat pump, possibly using the water well. I could roll that cost into the mortgage and amortize over 30 years.
That’s basically what I did. Right now, electricity costs about 4x as much as natural gas per unit energy around here, not 9x, so it’s close to a wash (with a ground loop system). But most of that electrical cost is recent, and political, due to Green New Deal nonsense. It could vanish just about as fast as it was imposed, if we can fix the politics.
So basing your 15-year heating strategy on present-day costs imposed by a politically motivated boondoggle may or may not pay off in the long run. It’s not obvious that it will.
The rich are planning to make trilling off of so-called “Climate Change” spending. Bloomberg estimated it will cost $200 trillion to stop warming by 2050 and calls that a bargain.
https://www.bloomberg.com/opinion/articles/2023-07-05/-200-trillion-is-needed-to-stop-global-warming-that-s-a-bargain#xj4y7vzkg
>>>you have to look for an alternative heat source
oh that sounds so simple when you haven’t any limits or boundaries on your property. For the vast majority who live in urban settings, especially high-density multi-unit apartment buildings, there isn’t a means to access such alternatives as ground or water source heat exchange. I’m quite certain the city council objects to any homeowner or tenant drilling hundred metre holes in the ground, or lay unauthorized piping into a body of water for his own heat pump.
UnF’nbelievable…I presume you’ve never heard of the country named Canada. O right there’s only about 35M people there so not ‘most’….it was -50C in my hometown of Saskatoon just after xmas (-60C windchill). A city of ~250K people. The provinces of Manitoba, Alberta, Saskatchewan, most of Ontario, good parts of BC, Quebec, PEI and Newfoundland (not to mention Labrador & the Territories) REGULARLY see below -25C for extended periods of time in the Winter.
I laughed my ass off the first time I saw a commercial for heat pumps in Canada. The government is actually promoting these things…absolute bat shit crazy. Actually now that I think about it, this isn’t so bad. Anyone buying one in Canada immediately outs themselves as being bat shit crazy & they can be rounded up & stuck in an asylum as being a menace to society.
As with AlanJ you’ve outed yourself as a psycopath, you have 0 empathy for anyone.
Most of Canada during the winter months will experience -20C weather for weeks at a time. There are places in Canada that don’t ever experience -20C weather like here on Vancouver Island, -12C is the coldest here and then only for a few days. But, that’s cold enough that the heat pump efficiency lessens and other sources of heat are required.
The record low temperature recorded in Vancouver was -18C on January 14, 1950. I’m sure the heat pumps didn’t work well. The recorded low for every year since 1900 has been below 0C.
Do you have a source for your statement that “For most people, temperatures of –20°C are never encountered”?
Where we are in NE Scotland, -10°C is extreme and rare – maybe 7 days each winter? Generally winter temps will be in the -4° to +8° (there will be some actual data somewhere but this feels about right)
so they should work…the problem is the age and condition of the housing stock which is simply not designed for this technology.
Good article. As Carl points out above, air-to-air heat pumps are surely going to run into icing problems in any but the most arid climates if the temperature approaches 0C/32F. Also, while the current crop of heat pumps could heat domestic hot water as well as air, they have trouble getting to the water to 170F (76.7C) that baseboard hot water systems seem to be designed for. Many millions of buildings in the Northern US and Canada are designed for oil or natural gas heating via baseboard hot water. I’m guessing the same might be true elsewhere. In many (most?) cases, retrofitting the ducting required for forced air heating/cooling is going to be impractical/impossible.
On the other hand, much of humanity lives in the tropics where temperatures rarely/never drop below freezing. Heat pumps ought to work fine there. (As should solar hot water BTW). No reason not to use them there. I’m willing to count them along with energy efficient lighting as one of the few “green” technologies that are actually somewhat ready for prime time.
If you live in a place where the temperature never drops below freezing, the extra efficiency of a heat pump will never pay back the extra cost of a heat pump.
Good insulation, which will help all year round, and a heat strip, which you will only need a few times a year will be the best solution.
And its what they cost. To install, and to run.
Suppose you live in the UK and are thinking about replacing your boiler, which will be gas-fired in about 85% of cases, oil-fired in about 15%. Others in quantities too small to worry about.
What you’re being told to install is air source heat pumps. The first problem is the cost and the work of installation. The appliance itself and its installation will cost several times what a new boiler would. £10-15,000 as opposed to £3,000 or so.
But that’s only the start. Your radiators are the standard UK pattern, work at temperatures higher than an air source heat pump can deliver, so you need to replace them all. And the piping. This is more thousands.
Next, you have to provide for hot water, which your boiler used to do. Many, maybe most, are heating on demand – the cold water is heated as it flows through. Not any more, now you are going to have to run hot water on resistance heating. Going to be expensive.
Finally, you probably have your boiler on a timer. So it takes the chill off early morning, then goes off during the day, and comes on again at night for the evening. Not any more. You will need to run your heat pump continuously because of the very low temperatures it delivers. You cannot rapidly heat up your house or flat any more.
And speaking of flats, you have to find someplace to install it. Outside. Fine in the country, a detached city house, or in a terraced city house with a garden. If you are in a flat not on a ground floor, what do you do?
Still, lets assume you have got all this done and are out the £10-15,000 minimum that all this is going to run to. More if you have to insulate and draft proof windows. What about running costs? This is from uSwitch:
So you need a total energy recovery factor, including resistance heating and water heating, of nearly 4 just to break even. No way. In the damp UK climate you will get around 2 from air source.
This is why people are not buying heat pumps in the UK, even with government grants. They have heard the experiences of those that have, and they don’t think it makes sense.
When you think about the implications of the Net Zero drive, it also makes even less sense. This has already put up the price of electricity substantially, but if the new government carries on with the mad plans Labour has announced to get to Net Zero in generation by 2030, you will be very lucky even to get electricity to run your heat pump. Remember, its going to be on a smart meter. So every cold spell when you all turn on your heat, ping, off it goes. Got to protect the grid, and we are now in the usual January or February dead calm. Don’t charge your EV either. Be grateful you are still allowed to have lights on. And cook.
Just a small point.
A scientist named William Cullen is credited with demonstrating the first artificial refrigeration in 1748 at the University of Glasgow.
And by the way, the UK as usual the canary in the coalmine, all this is being done to reduce global emissions and global temperatures. This is why there was the serious proposal (now apparently abandoned) to tax/fine suppliers for every oil or gas boiler they sold over quota.
UK domestic heating is about 14% of UK emissions, which are in turn around 1.5% of global emissions.
https://airqualitynews.com/headlines/heating-accounts-for-14-of-uk-carbon-emissions/
I have seen other sources put it as high as 30%, but the above is government numbers. Makes no material difference to the argument.
The country, with the approval of Labour, Conservatives, SNP, Liberals, Plaid, is putting itself through this in order to save a fraction of a percent of global emissions. A savings which, even could it be realized, would be eaten in a week by installations of coal generation in China, India etc.
This whole project, the project of moving everything to electricity at the same time as moving generation to wind and solar, in response to a wholly imaginary emergency which, even did it exist, would not be materially helped by these impossible measures?
Its complete irrational lunacy.
That canary has never seen a coalmine
https://www.researchgate.net/figure/Heat-pump-deployment-rates-per-capita-across-selected-European-countries-in-2022-Nowak_fig1_374234657
There are two questions to ask about UK heat pumps.
The scheme is to move electricity generation to wind and solar at the same time as moving home heating to heat pumps powered by electricity. The first question is whether this is a sensible and feasible idea.
The answer is obviously not. Read the Royal Society report. The country could move to heat pumps on a grand scale, but to do so it would have to have greatly increased and reliable power supply, which wind and solar cannot deliver. They can’t even deliver current demand reliably, let alone the increases that heat pumps and EVs would require.
It would also require increased insulation of housing, on a scale that previous initiatives haven’t even come close to. And probably very large sums on subsidies, because of the need to rip out current radiators and piping and replace them with something suitable to low radiator temperatures.
The move itself could be done. Whether the country could afford it is another matter. But to do it you would have to give up on the move to wind and solar and instead install lots of gas capacity. That’s the only feasible way of getting enough power to run the heat pumps.
The second question is whether moving UK houses to heat pumps will lower UK CO2 emissions. Probably not, given that they are going to be running on fossil fuel generated electricity, and given the increased complexity of the systems and the need to replace the radiators and pipework. If there are any savings in emissions they will be very small.
I guess a third question is whether doing this will have any impact on global temperatures. The answer is obviously not. UK home heating emissions are about 14% of total UK emissions, which are in turn about 1.5% of global emissions. Suppose you manage to reduce UK home heating emissions by a third – which is a very optimistic estimate, I think actually moving to heat pumps would raise them, but just to figure. Would this have any impact on global temperatures? Of course not.
There is no point moving to electricity if that electricity is going to be generated from gas. Its a lot simpler and cheaper to just burn the gas in boilers as now, and there is no reason to think that moving to heat pumps will materially lower UK emissions or do anything for the global climate.
Instead of making evidence free assertions about how great they are in a UK context, we need to look at why people in the UK are not buying them. Its a combination of high electricity prices (high in part because of the attempt to move to wind and solar generation), high system costs, unsuitable housing, damp climate (which affects efficiency). People are not stupid. Word gets around from those who have tried it. Its not a sensible choice for most people, and its not even possible for many.
“There is no point moving to electricity if that electricity is going to be generated from gas”
No, that isn’t true. If you generate electricity from gas, that is about 60% efficient. But per the article above, using the electricity to pump heat is about 4x more efficient, so overall you get 2.4 times more heat in your house than just burning the gas.
As it happens, electricity is currently about 4x more expensive than gas per MWh, so in terms of what user pays, it is a wash. But that is heavily influenced by the price cap, and will likely change.
You never get 4x in the UK climate. 2x is more like it. Plus, you have to take account of the fact that you don’t get any water heating from the heat pump, but you do from a gas boiler, and in the so-called ‘combi’ boilers that’s a heat-as-you-use system, so very little waste.
You have tp add the electricity used to heat the water to the total account, and that lowers the 2x comparison still further. Compare like with like. You need to compare hot water + heat in both cases.
And you have to allow for losses in transmission of the electricity. It may be 60% at the generating plant, its less by the time it gets to the house.
Typical efficiency levels for UK boilers are also way over 60%. Condensing boiler efficiency (which is what all new boilers are now, by law) is about 90%.
So basically you lose 40-50% of what you burn at the generating plant in the form of useless heat, which if you burn the same gas at home gives you 90%, because the heat is what you want and all you want.
People are not stupid. There is a reason people are not buying heat pumps in the UK, even with government subsidies.
Its wishful thinking, ideologically motivated. And unreasonable. Even if there is a climate crisis, moving UK domestic heating to heat pumps is anyway not going to have any effect on it. A total waste of national effort. Why are people so bent on doing it? The only answer I can come up with is, hysteria. And wishful thinking.
If it were possible to have 100% wind and solar generation, it might possibly make some sense depending on what that costs. But that is proving to be a very expensive pipe dream.
“You never get 4x in the UK climate. 2x is more like it.”
The author here quotes 4x, writing from Canada, and I think that is about right. In UK the temperature difference is less, so the theoretical efficiency is higher. The factors that limit that efficiency would be about the same.
UN/IPCC fueled hysteria. They have the biggest voice on the planet. Every country listens to what they say.
You are conflating two different “efficiencies”. Not all percentages are equivalent.
The efficiency you are using for the heat pump is similar to saying that the efficiency of a solar panel is infinite because it is converting FREE energy from the sun into electrical power. Free = zero. Divide by zero and you get infinity.
When world human-caused emissions of CO2 were reduced by around 25 percent because of the COVID-19 restrictions, the monthly increase in CO2 kept going up at the same rate.
‘Temporary reduction in daily global CO2 emissions during the COVID-19 forced confinement’
https://www.nature.com/articles/s41558-020-0797-x
‘Charts for Mauna Loa CO2’
https://www.co2.earth/monthly-co2
The whole climate change subject in the UK is ripe for Monty Python-style movie
The oceans have around 70 times as much CO2 as the air and they are at equilibrium at the surface, so if the amount of CO2 in the air is reduced, the oceans will just replace it.
There are 2 types of heat pumps. Air cooled is not suitable for very cold locations as the author stated. Water cooled underground can be at sufficient depth or using a water sink (well) to still be economical, but capitol cost may be very high. Electrical power costs are much higher is some places that most of the US, so high electrical power costs can make the heat pump more costly than gas. Where electrical cost is lower, the reverse may hold. In fact the best choice depends on these details, so I do not see the strong point emphasis made here.
With water cooled, you need a well that is capable of providing a relatively high rate of water flow.
I have a heat pump and a natural gas furnace. At 38 F or below, the heat pump is idle and the furnace provides the heat. It works great, but it wasn’t inexpensive.
I would make a couple of points. First, efficiencies greater than 100% are physically impossible, typical of comments that I have seen on heat pump manufacturers’ websites is: ” Air source heat pumps use 1 kWh of electricity to generate 3-4 kWh of heat”. This is misleading, heat pumps do not generate heat, they transfer existing heat from outside to inside, hence an apparent 3-400% ‘efficiency’. This might seem pedantic but if we are talking thermodynamics then we should be correct. The second point is one that was only briefly touched upon, that overall efficiency is not the only issue, the rate at which heat is transferred limits the temperatures achievable. A house naturally loses heat, the greater the differential in temperatures inside and outside, the faster the rate of cooling. When the rate of cooling equals the rate at which the heat pump delivers heat then the maximum internal temperature is reached. The solution to this is highly efficient insulation, plus don’t open your doors and windows! I have read that here in Britain the average level of insulation is nowhere near adequate and upgrading will add considerably to costs.
“When the rate of cooling equals the rate at which the heat pump delivers heat then the maximum internal temperature is reached.”
The rate at which the heat pump delivers heat is a function of it’s size, usually specified in tons. A heat pump when used for heating is sized by calculating the heat loss in BTU (i.e., 12,000 Btu equals 1 ton) of the building space at a specified minimum outside temperature . When also used for cooling the heat gain of the building space is calculated based on a specified maximum outside temperature and the heat pump sized accordingly.
The rate at which the heat pump delivers heat is a function of it’s size
Which would suggest that a bigger heat pump is better. That may be the case for heating (I don’t know) but is definitely not the case for cooling. You need the size balanced against the space being cooled. Too big can cause maintenance and performance problems.
Well, okay, perhaps the sales pitch should read “to bring you 3-4 kWh of heat.” My vented propane space heater is some 90% efficient, the unvented units it replaced were 100% efficient.
Frankly, I don’t really care how much I heat or cool the outside. Well, my weather station is far enough away so it’s sited better than many NOAA uses. 🙂
jim,
I have to disagree on your understanding of how heat pumps work. I did make a much longer post to Mr Stokes earlier about efficiency and that air source may be no more than 60% true efficiency.
Heat, scientifically, is found in anything above degrees absolute, at -273K.
Using the term heat for the suction line temperature, from outside ambient air is irrelevant as a source of heating and the discharge temperature derived from the compressor is built on that temperature, i.e. rises and falls with ambient. The actual useful heat is completely derived from compressing the refrigerant, i.e. physical mechanical input from compression.
To use an absurd idea, open the doors and windows so the outside heat warms your house?
To “beat” the second law of thermodynamics, simply apply it. My all-electric house is heated and cooled by a ground source heat pump which heats and cools my house by way of three, 200-ft deep wells, each equipped with a closed circuit water in-out loops. The earth in my area is at a constant 50F regardless of season which provides a good source of heat in the winter and cool in the summer. The electric bill for running my house rarely exceeds $200, last month (a cold January) was $110 for everything, heat, light, cooking and hot water. My ground source system replaced an air source system which had some of the problems you describe. The down side is the cost, about $20K to serve my 1,600 ft2 house; 1/3 for the wells and water loop inserts, 1/3 for the HVAC machine, and 1/3 to put it all together. It has worked flawlessly for about 11 years so far.
Sounds great. However you couldn’t do that in the millions of Victorian and early 20thC terraced houses in the UK.
Not everyone has a lot that is big enough for three wells.
How long will the ground stay at 50F once all of your neighbors also start drilling three wells and running their heat pumps all winter?
I don’t know precisely but 1) One other house in my neighborhood has a ground source system. It’s next door on a 1 acre lot and in the 10+ years of operation of both systems, I have noticed no degradation in performance. 2) Our lots are quite large for the most part, 2 acres+ but for a few nearby townhouse developments and a highrise condo and 3) The water table is quite high where I live so there is a steady flow of water underground towards a nearby river. This flow maintains a pretty constant ground temperature. 4) Water has a very very high capacity so it is not difficult for the machines to suck out a bit of heat in the winter and cold in the summer to manage the very low heat capacity of the air in the house without altering the ground temperature notably.
Dave Andrews comment above is certainly correct. One needs a large enough lot for the wells with access for the large drilling rig, and having a modern well insulated house is also probably essential. I would have installed gas when we bought the house but the gas company wanted $25K to run a pipe from a gas main about 600 ft away, so I “saved” $5K. In the UK, the price of electricity, roughly thrice what I pay, may also alter the equation.
The machine has worked well for me. I encourage anybody wanting to upgrade their HVAC system to consider a ground source system if they have the land.
It’s good you had a competent designer/installer for your system. Of the several people I have talked to in this area of West Virginia that have ground source heat pumps most wish they had installed at least one additional well.
I’ve been very happy with my ground loop system too. Mine is 4 wells (a 4 ton heat exchanger), also with a high rate of ground water flow. I think they oversized it by a ton, which increased the cost unnecessarily, possibly by underestimating the efficiency of my house’s insulation. Anyway, lesson learned, and it’s still cheaper than my neighbours’ natural gas furnaces. (Although with the artificial politically motivated cost increases of electricity, not as much cheaper as it should have been, grrr)
Very few people have 1 acre lots.
How is that “beating” the second law?
$20,000 11 years ago is a lot of money compared to a gas furnace and air conditioner. I’m sure the cost is much higher now. I know A/C units are about double what they were five years ago.
Not every heat pump is the same, R-430 works very good at an outside air temp of 12 degrees F. (82 Degrees Vent Temp Texas killer freeze Mr. Cool 110v 1 ton running off a 4000W generator)
Back in the 80’s, (Haven’t seen temps like the last few years since the 80’s) An old R-22 system would pretty much stop being effective at around 16 degrees F. (didn’t take output readings back then but output air not able to keep the room in the 60’s), single digits tested it, and you could tell that the refrigerant was immediately condensing after it was vaporized after leaving the orifice on the outside coil.
Of course R-430 is being phased out, and I do not know the efficiencies of the replacement refrigerant gas. They are starting to use CO2 and Propane as refrigerant gasses as well, so the dynamics could change.
They are not as efficient, but a lifesaving device on both ends of the spectrum.
Take the condenser fan out, and downsize the compressor and utilize a heat exchanger in place of the condenser in a shallow ground water loop and then you have Geothermal, which is the only way to go if we want to tackle the enormous energy requirements of regulating the internal climate of our dwellings. Could a roof full of solar panels turn the compressor and cool or heat the dwelling with a geothermal system such as that? And with an air core ground loop exchange mode with house air directly coupled with the ground fluid loop, only a fan and a circulation pump is required to provide cooling or heating, assuming your locations subsurface temperature is a more desired temperature than outside.
Of course R-430 is being phased out,
Sure it is, refrigerants, among the chemicals most responsible for a high standard of living and health, are a constant target of both CAGW proponents and replacement manufacturers. The supposed decomposition of the ozone layer was an early, expensive and effective impetus for the climate anxious. The day after the Montreal Protocol was signed daily newscasts describing blind sheep wandering around Patagonia and Argentinian schoolchildren being unable to play outside came to a halt. Every one of the heavier-than-air R-12 and R-502 molecules that were in refrigeration equipment eventually escaped to higher altitudes but no one seemed to care, except grocers faced with replacing their refrigeration systems.
It’s actually the chlorine in chlorinated flourocarbons that is the culprit in ozone depletion. If this is so, why is the use of chlorine as a biocide in food processing, swimming pool treatment and municipal water treatment allowed? Don’t some of those released chlorine atoms also end up mingling with the ozone molecules far above the earth, causing skin cancer everywhere?
The crazy thing about R-430 is, it is being phased is not because of its chemical composition in relation to stratospheric chemistry, it’s because it has a global warming potential. A new classification now from the EPA, that is based on a broken theory. So, a refrigerant that had a cost at its low point of 2-3 dollars per pound is now 10 – 15 dollars.
A heat pump “collects free heat from the outside and delivers it inside” …
Sounds like the ideal solution to global warming, don’t it? I tried taking my window air conditioner and turning it around. It did get cold outside, but my wife made me stop before I collected enough data for a paper.
All yucks aside, I live in rural Missouri and heat pumps are very common. The heat pump in my house works well most of the time. It worked overtime during the February 2021 deep freeze and we had to use space heaters to keep whatever rooms we were occupying at the time comfortable. Off the top of my head, I’d say 15F is where the heat pump begins to struggle.
Costs and mechanical issues aside, the article didn’t mention yet another reason why heat pumps suck – personal comfort, or lack thereof! I have been in many homes with heat pumps, sometimes for hours. And every one I have felt cold. And then I’d check to see where the thermostat is set, and often times it is set higher than in my own home (where I don’t feel cold). One client home I was in was set at 74F. And I felt cold! I keep my home at 68F and I’m comfortable.
Heat pumps will always blow cold (or at best tepid) air, even on days when it is close to or below freezing outside. My husband rented a house with a heat pump back before we got married. There was nothing like coming over to his place on a cold night (temps in the teens) and coming into a house with cold air blowing in your face from overhead ducts in the basement! And the upstairs wasn’t much better….
Sorry, I want WARM air or WARM radiators/baseboards in winter. I have oil fired baseboard heat and it’s great! I’d much prefer natural gas but it isn’t available where I live. If I had the money, I’d convert to propane heat.
One thing to be careful of when comparing one home to another, is that not all thermostats are created equal.
Place half a dozen thermostats side by side, and there will be a noticeable difference between the temperatures displayed on them.
My (latest) thermostat is especially tricky. If I switch it to “off”, it says the temperature is perhaps 23 C (for example). And I believe this reading is accurate, from various correlating independent thermometer measurements. But then I switch it to “air conditioning”, with the desired set point at perhaps 20 C in this example, and it immediately gaslights me into thinking the current temperature is actually 21 all of a sudden, and therefore there is no need to turn on the AC compressor. (I have the allowable temperature swing range set to the maximum possible value of 1.5 C, to maximize the duty cycle of the compressor.) Hey, wait a minute!
I depend on a three small space heaters.One kept its room withing +/- 2 degrees but its fan bearings eventually failed. It “ceramic element” replacement has at least a +/-10 F range for any thermostat setting = totally useless. The most used of the three heaters, several years old, also seems to have about the same thermostat setting range. The bottom line is that I have to be the thermostat but since no heater is on unless I am occupying that room, is is only a minor nuisance.
I replace my thermostat and set it to the same temperature as the old one. The furnace now goes on a lot less often than it used to. I think that proves your point.
My HP charged with R410a consistently runs 104F air discharge temperature, which is nearly what I get running Natural Gas. Older HPs running R22 couldn’t do this. HPs made today are more comfortable than early machines.
It wouldn’t be doing that at my house with the outside low temp at -43°C where it was a couple of weeks ago for several days.
I think I’ll keep my oil fired boiler which circulates 150F water thru my baseboard radiators. Plus, I can set the boiler temp (for both domestic hot water and heating water anywhere between 125F and 165F).
Ron: It should be noted that there are two types of heat pumps. One is an air-to-air heat pump and the other is a ground source heat pump (GSHP). The first is the one most people think of when you say Heat pump. The second may NOT have the cold weather problems the air-air units have.
Having said that. GSHP’s are quite effective in suitable locations
In the UK once you have insulated the house so the heat pump lower water temperature works, you have made the house so efficient the old Gas boiler if kept burns so little gas you can forget to install the heat pump. Gas per Kwh is a fifth of the cost of Electricity per Kwh. With the COP being 3 at best it just makes no economic sense to go heat pump.
The key caveat here is: “Granted, in moderate climates where winter home heating is more for comfort than survival, and especially where summer air conditioning is desirable, a heat pump that’s switchable to an air conditioner is probably worth looking into.”
In the SE United States, this statement is true. Where I live air source HPs are ubiquitous. Lots of AC is needed in the summer, and the additional cost to convert to HP is a few hundred USD. The cost of energy to run a HP vs Natural Gas equalizes at about 4C outside temperature: below this temperature we use natural gas heat. For electric strip backup heating the crossover doesn’t exist; backup heating is only used when the HP can’t keep up with the demand.
No one in the government had to mandate this. Simple economics alone made it happen. When HPs are made that operate efficiently at sub-zero temperatures, market force is all that’s needed to make installation happen.
What is described above is an air/air heat pump which indeed is not efficient for heating in cold climes, but the heat pumps being promoted in the UK and other parts of Europe are air/water.
These extract heat from outdoors and via a heat exchanger either within the unit or indoors heat water to be circulated through pipe work and radiators.
My personal experience for a large farmhouse in France: the existing heating was oil boiler heating hot water and underfloor (tiled) pipes. Oil became expensive. France being 80% nuclear electric has relatively low electricity prices. Piped gas is only available in some cities and towns, not in the countryside. LPG is available but is expensive like oil.
The unit installed was a large double fan unit on a concrete base with a three phase electric supply. Max output temperature was 55C, ideal for the underfloor system which operates at 40C. It was recommended I keep the oil boiler for heating the hot water (cheaper) otherwise I would need a storage cylinder with immersion heater to boost temperature. Also the boiler was there in case the heat pump failed.
The system was guaranteed to maintain indoor temp at 20C down to an outside temp of -7C.
It worked just fine. On occasions outdoor temps dropped to around -10C, but indoors temp was great. I used to set thermostat at 22C which was achieved. My heating costs were halved. Installed cost 2012 was 11 000€ with 2 500€ Government grant. (Grants were not available for air/air units which are not considered efficient in terms of energy use.)
The unit I had installed was much bigger than what I see being proposed in the UK. They are noisy because of the fans and particularly so when temperatures drop (night time) when the unit has to work harder. Depending on air moisture content, the unit stops now and then and goes in reverse taking heat from the water to defrost the heat exchanger behind the fans. It only takes about five to ten minutes.
These units are not practical in the UK, unless you have a detached property with outside space, install a large one. From what I have read, the electricity costs – in the UK – of heat pumps offers no cost advantage over piped natural gas which is readily available throughout most of the UK, and electric probably will cost more.
Additionally, a hot water tank and immersion heater will be needed and many UK houses have combi-boilers so this will be an additional expense or there may be no room.
Heat pumps can provide adequate heating and be cost effective if: the right size, and if other energy is more expensive/not available. In the UK, natural gas is best option/least cost in terms of boiler/installation costs, space required, noise, efficiency.