Zombie, of San Francisco’s “Zombietime” fame, writes in with a question that he has graciously allowed to be given to our readers.
He writes:
I’m preparing to write an essay on the following hypothesis:
Solar power installations, especially in desert areas, replace light-colored high-albedo sand/rock ground surface with very low albedo black solar panels. The “side effect” (in fact, the whole purpose) of solar panels is therefore to capture radiant energy coming from the sun that would otherwise reflect back into space. Because this energy is then converted into electricity, which is then used to power devices and inevitably degrade into atmospheric heat (which does NOT as easily radiate back out into space), the overall result of large solar panel installations is to heat up the planet more than it would be heated without the solar installations.
But of course the solar-energy advocates will say that the solar installation is replacing a carbon-burning power plant, which produces greenhouse gases that the solar facility does not.
The question I seek to answer is:
Has anybody ever actually sat down and calculated whether the CO2 greenhouse effect caused by a carbon-based power plant generating one megawatt of electricity is more or less than the warming effect caused by the lowering of the earth’s surface albedo from a black-panel solar installation with power output large enough to completely replace the carbon-burning power plant?
I suspect that no calculations of this type have ever actually been done, and that solar panels may in fact contribute more to global warming than anyone previously realized — and in fact may cause just as much warming as the power sources they replace.
I have searched but cannot find such a study; but the reason I’m writing to you is that I have some vague memory of this thesis once being discussed on WattsUpWithThat — although I no longer can track down where exactly.
So I ask: Do YOU (without any time investment) remember offhand where or when this hypothesis was discussed on WattsUpWithThat? And if not, do you think this is a worthy line of investigation?
I know this is a somewhat vague question, but your guidance is invaluable!
— zombie
I promise not to reveal whether Zombietime is M or F.
Just to split a hair …
jai mitchell (at December 10, 2013 at 11:34 am) mentioned the simulation of solar panels by making the surface black.
I think there might be a significant difference between a blackened surface and a black solar panel. Energy absorbed by the solar panel is transmitted or stored, while the black surface would have to simply re-emit the absorbed energy.
Of course (thinking globally) the stored energy will later be re-emitted when it is utilised, but the effect on local temperature might be a little different.
Hahahaha – FINALLY
I asked this very question when I first saw a solar tower and mirror array. When was that? About 40 years ago? They were proposing these be spread out all over the deserts of the world – unused land, I think was the concept.
And I think my question was, “What does that do to the planet’s albedo?” I didn’t see anything good coming out of it. In the long run it would have to affect the climate. In specific ways, beginning with local/regional changes in heat flux.
This is the first time I have EVER heard anyone else think of this, that the albedo change would mean more heat energy trapped on Earth. And DID ANY OF THEM BACK THEN BOTHER TO THINK OF THAT?
THANKS, ZOMBIE.
I liken these cover-the-desert-with-solar-devices to the stupid idea of biofuels.
It is quite possible that even a couple of 100 square mile PV facilities would be trivial in comparison to the 19,000 square miles of asphalt already incorporated in the US highway system.
A very good point, actually. Bear in mind that the surface area of the US is 3.8 million square miles, so that 19,000 square miles of asphalt is a nice convenient 0.5%.
I find it difficult to think in the English system — let’s go metric. In metric, the surface area of the US is roughly 10^7 square kilometers, or 10^14 square meters. A single square meter of solar panel receives an average of 150 to 250 watts/square meter over the lower 49 states (averaged over years of 24 hour days, not daylight hours that are 2-3 times this). The US consumes something like 20,000 TW-hours per year. If we set solar conversion to an easy number like 10% and assume 200 watts/square meter as some sort of mean insolation for the country (excluding Alaska, where solar panels will never make much sense) we can reap something like 20 Watts/meter squared times 24 hours a day times 365 days a year, or 175 kW-hours per square meter.
Too hard, let’s call it 200 kW-hours/meter^2. Then we need 20,000 x 10^12 / 200 x 10^3 = 10^10 square meters of collector to provide all of our current consumption, assuming perfect ability to store and/or transport the energy. That’s a square 10^5 meters (100 km) on a side, or 10,000 square km. The US is 10^7 square km, so we would have to use just about exactly 0.1% of our surface area to provide all of our energy needs (again, idealizing a bit but not really that much). This is a far cry, of course, from 100 square miles — more like 100 miles SQUARED. But still, one could fit it all inside a comparatively small corner of southwest Texas or New Mexico or Arizona desert and never miss it. One could replace the tobacco fields of NC with solar farms and the whole world would only benefit (both ways!).
Note well that concentrated solar power (mirror/heat based generators) have achieved something like 30% efficiency and would cut the area numbers by 1/3 if broadly implemented. It currently produces electricity at an amortized cost of around 12 to 18 US cents per kW-hour, competitive with fossil-fuel based production costs in certain venues (and within a factor of 2 of competitive in most venues). However, PV solar is passing it in cost-efficiency and so far PV solar has obeyed something like a Moore’s Law as far as fabrication and production costs are concerned. If PV solar production costs (per “watt” of delivered power) continue to ramp down for one or two more decades at the rate that they’ve been decreasing for the last two decades, PV solar will be cost competitive with most fossil fuel based energy production by 2020, and will be significantly cheaper by 2030, even ignoring the possibility of increased costs for extracting fossil fuels and completely ignoring the CO_2 issue for better or for worse.
Personally, I think most of that is a done deal — I think that solar power is in our future barring the widespread implementation of e.g. Thorium based power generation or the invention of cheap, efficient, thermonuclear fusion based power generation. The existing technology is sufficient already given economies of scale, and there is considerable progress being made towards still better technologies (higher efficiencies, lower manufacturing costs) and nanoscale physics contributions to this developing science haven’t really had time to have an impact yet. Higher efficiency means less local heating — from the point of view of conversion, waste heat is wasted money, so there will be a lot of old fashioned self-interest driving the development of hybrid systems that waste less of it (for example, using the same panels to convert sunlight to electricity and to heat water for immediate use (and cooling the panels) or to heat a house at night).
The open questions are storage and long distance delivery. Solar power really would make sense as a complete replacement for fossil fuel based power — if one could efficiently bank it for at least days, possibly weeks. At the moment one can do little more than buffer it for minutes to hours and supplement it with natural gas generators that can be brought online “instantly” to make up for the natural fluctuations in production. One saves fuel (and fuel costs), but it is hardly a stable or particularly economic solution so far as it requires one to have almost twice the production capacity needed to deliver the expected load — as much as 100% from the natural gas generators (e.g. at night), and as much as 100% from the solar cells during the day, with a mix in between.
Rooftop private domestic collectors are a better idea — they don’t cost a lot, they are break even or thereabouts over a reasonable lifetime of the hardware plus maintenance costs (with a still-too-long amortization, but one many people will borrow to pay now to be able to NOT pay for electrical power for 20 years) with reselling into the grid. This reduces load on the primary generation facilities during the day in useful, fairly predictable ways without the need for a particularly complex optimization system and twinned commercial production.
Naturally, there is a lot of work being done on energy storage as well — both advanced battery designs and more exotic methods. There is an efficiency penalty and additional cost associated with storage, but one can still be optimistic that the problem will be solved within one to two more decades of focussed work. There is certainly a strong financial incentive to solve it.
To conclude, if one takes the US as “typical” and wishes to produce energy on a similar per capita basis worldwide, one might expect to use between 0.03% and 0.1% of the land surface area to do so, which is less than 0.01% of the surface of the Earth proper (which is 70% ocean). If one heated all of that surface by 20 degrees Centrigrade over its usual average temperature, it would still heat the world far less than the urban heat island effect already is heating it — the heating of the roadways, buildings, tilled earth, parking lots of human civilization. Compare 3.8 million square miles to 19,000 square miles of roadway to 4000 square miles (10,000 square kilometers) of collectors. The latter is simply quantitatively negligible, no matter how hot you imagine the collectors make the ground there.
rgb
While there are a handful of exceptions, overall that so much writing has been expended by so many without immediately seeing the obvious is borderline disturbing.
As a thought experiment, even all power being produced by solar would have trivial (practically zero) effect on global temperature. Earth is hit by 200000 terawatts of sunlight. Human electricity generation averages 2 terawatts. Throw in inefficiencies of the solar panels plus other details, and somewhat more than 1 / 100000th of Earth’s area would be covered in that event — but such is still utterly trivial. (The same, incidentally, is also so for waste heat from nuclear power generation; it may warm up a local river, for instance, but not millions of cubic kilometers of ocean waters as a whole to any significant amount).
(Human CO2 emissions don’t have much of a temperature effect either, like Dr. Shaviv, in one of his papers reference on sciencebits.com, calculated about 0.5C of the 0.6C of warming in the past century was solar/GCR and not anthropogenic, but the global temperature effect of multiple terawatts of solar power, multiple millions of megawatts, let alone a single megawatt, is insignificant).
One of the causes for mathematical literacy being uncommon is that most people alternate between one of two states: (a) no quantitative thought, with assumptions often off by orders of magnitude versus (b) time-consuming “exact” formal calculations of the kind they were taught to do in school but never actually do in any other context due to such taking much effort. “Back-of-the-envelope” calculations or quantitative approximate assessments of the general order of magnitude of something tend to be quick, easy, practical, and vastly superior to the (a) which gets resorted to when few want to do (b).
As Willis Eschenbach, Son of Mulder, and Enginear pointed out in their comments, a conventional power plant — be it coal, natural gas, or nuclear — produces waste heat. One can think of the extra light absorbed by solar panels (that which decreases the Earth’s albedo in excess of electricity produced) as a kind of waste heat. The heart of the matter is captured in a very succinct calculation; the trick is having realistic numbers. Willis Eschenbach suggested that a solar panel, compared to sand, causes an additional 28% of incident sunlight to remain earthbound instead of reflecting back to space. If a solar panel can convert 10% of sunlight into electricity, then the effective conversion efficiency (electrical output compared to extra captured sunlight) is 10/28=35%. This idealized case is remarkably similar to the efficiency of conventional power plants (electrical output compared to energy burned). That is, solar panels have a heat footprint per unit of electrical energy produced on par with conventional power plants. This is not a reason to pick on them.
As usual, I made a late-night arithmetic error 20,000/200 = 100 = 10^2 (times 10^9) so it is 10^11 square meters or 0.03-1% of the surface area depending on efficiency and location. Oops.
Still negligible even in the unlikely event that we ever get to where we are producing 20 TW-hours/year from PV solar alone.
rgb
I just don’t think albedo has that much of an effect. A couple years ago when something like 80% of the northern hemisphere land mass was covered with snow, there wasn’t a subsequent lengthening of the winter, or extreme cold snaps as a result. The snow melted much as it always does.
If that had no effect, the miniscule amount of land taken up by even hundreds of full-scale solar plants would have no calculable effect.
The problem is that while the heat produced by both the solar and coal fired plant radiates away relatively quickly, the greenhouse gases released stay in the atmosphere for decades, and in the biosphere for eons. integrated over time, there is no comparison. these calculations have been done, and over time the solar plant is vastly less damaging. warming is just one part of the problem- the other it’s ocean acidification.
[off topic – this thread has nothing to do with Gray -mod]
So while we have everybody doing crazy mathematics lets see if anyone can do this crazy calculation. There are currently 6 Billion people on the planet all eating and subsequently radiating heat 24 hours a day to hold a constant body temperature. The amount of heat given off depends directly on the activity level however lets go for the mid assuming half the population is asleep and the other half is very active. How much heat is given off by the citizens of the planet as an average?
MarkB says:
December 10, 2013 at 11:36 am
Paraphrasing…. The substitution of PV for fossil fuel has a 30x benefit over albedo increase.
Why do we always forget biology? Do we really want to cover that much surface area and starve out photosynthesis in those areas? I take it as true without proof biology is the key stabilizing factor in Earth’s climate. Obviously, having a planet with 70% oceans helps. Impacting photosynthesis on a very large scale could begin to alter the climate by changing atmospheric composition. A gedanken experiment in which all photosynthesis were blocked would result in an increase in CO2 and a decrease in O2, at least until respiration and combustion stops. However, changing our experiment to retain large areas of photosynthesis might permit biology to compensate and reach a new equilibrium state with a higher level of CO2. Maybe this is a smart approach to delay the next Ice Age. Well, it could be, except it’s stupid in so many ways.
One issue I see here is that solar panels generally have low efficiciency of converting absorbed solar radiation to electricity. Solar radiation energy that gets absorbed but not converted to electricity sent down the wires, becomes heat. Likely, more heat is developed than if the solar power plant was not there. This has to be balanced against the issues of reduction of CO2 boosting.
Also to be considered: Solar panels needing to be cleaned of dust, and likely needing protection from sometimes-abrasive-airborne desert winds.
LdB says:
December 10, 2013 at 10:24 pm
“How much heat is given off by the citizens of the planet as an average?”
The rule of thumb is that the waking rest metabolic rate for an adult human is 100 Watts. (This is used by HVAC designers for air conditioning capacity for auditoriums, for example.) Given that active people use more, and sleeping people less, 100 Watts is a reasonable average.
With 7 billion (7×10^9) people, this amounts to 7×10^11 Watts, and given the earth’s surface area of 5×10^14 m2, we get a power density of 1.4×10^-3 W/m2, or 1.4 milliwatts per m2, from human power output.
_Jim, where is your Christmas Spirit? For Jim Morpuss, I suggest a special fund. This year, we can all chip in to get him his very own, sustainable, bicycle powered Christmas Tree! As he says, this would kill two birds with one stone. Not only would he have a copious, free source of electricity, he could watch his girlish figure as well!
My calcs re waste heat:
World Energy Usage Annually = 117 x 10^15 watt-hours (= 117 x 10^15 x 3600 watt-seconds = 421 x 10^18 Joules) from fossil fuels. Total consumption of energy is about 144 x 10^15 watt-hours per annum if nuclear and renewables are included. Another source says total world energy consumption is 465 x 10^15 BTU which is about 490 x 10^18 Joules. Most of this ends up ultimately as low grade waste heat in the atmosphere, some ends up as waste heat in the ocean by way of warm water from power plants etc. Some ends up as potential energy e.g. as concrete high up in skyscrapers, etc. For the sake of the following exercise I assume that 50% of this energy ends up in the atmosphere each year as heat.
Specific Heat of Atmosphere, Cp, = 1005 J/kg
Mass of Atmosphere, M, = 5 x 10^18 kg
Q = M x Cp x T
T (per year) = Q (per year) / (M x Cp)
= (117 x 10^15 x 3600 x 0.5) / (5 x 10^18 x 1005)
= 0.0419 degK per year
= 0.419 degK per decade
= 4.19 degK per century
This is a first order approximation of the temperature rise of the total atmosphere cause by the addition of waste heat without consideration of any other heating mechanism.
I don’t know how the waste heat and associated temperature rise is handled by the atmosphere and blackbody radiation out to space etc. but I think the calculation above is correct given the assumptions. There has been no temperature rise for 10-15 years i.e. a steady state condition exists, so none of this heat is heating up anything. So even if there is no net warming by CO2 as a greenhouse gas then a very serious cooling mechanism has been occurring for the last 10-15 years to maintain the temperature steady. Or if there is no hidden cooling effect the feedbacks resulting from changes caused by CO2 are highly negative. Either way there is a serious negative mechanism. I just don’t have time to review the literature properly – has this calculation been included in any energy balance summary for the atmosphere.
How much heat is given off by the citizens of the planet as an average?
The average power consumption of the human body at rest is around 100 watts. If you allow for activity, perhaps you double that or even triple it some of the time or generate more if you live in a cold climate. Still, 150 watts is a pretty reasonable estimate given big people and little people and everything in between. Multiply by 7 times 10^9 and you get roughly 10^12. So a terawatt. Maybe even 2. Which vanishes without a trace in the Earth’s energy budget.
rgb
I think Leif Svalgard put this question into context with an easy comparison.
All of man’s energy output from heating, lights and machinery, is about the same as the reflected heat energy we receive from the Moon. In other words, not a lot in comparison to the Sun….!
That was the point rgb I haven’t added in animals and other hot bodies but perhaps I should have used the heat from a volcano eruption or the countless other strange heat sources around. The message for Zombie was these levels of heating have to be able within Earths coping mechanisms or else it we would have long ceased to exist 🙂
Willis, I love your way of doing back-of-the-envelope calculations, you are my absolute hero 🙂
However there’s one part of the whole ecuation that I think that you didn’t consider. While the warming that the CO2 would cause would be distributed throughout the whole planet, a big part of the extra warming accumulated by the solar panels would happen at the panels themselves. This would greatly increase their temperature compared to the temperature that the underlying sand would reach without the panels, and emissivity increases with the fourth power of temperature. In addition, the panels themselves are black, which implies high absorption but also high emisivity. What I want to get at is this: the extra warming of the panels comes with a significant extra emissivity as well. So the panels cause the planet to receive more energy from the sun, but also cause it to cool faster. This may greatly reduce the difference of extra heat accumulated compared to the CO2-emitting power plant scenario.
Unfortunately my skills at back-of-the-envelope calculations are ridiculous compared to yours so I don’t feel like I could possibly do the numbers.
Kind regards.
LdB says:
December 10, 2013 at 5:43 pm
“”So there is the answer for Zombie as given by climate science and it wasn’t that hard to find … you just have to read.”
Well, thanks for the “lazy and stupid”; you know; I NEVER look into the IPCC report for ANSWERS. I only look into it for lies. Zombietime wanted an answer; so the IPCC report is simply not the right place to look.
One calculation that is not hard to do is to take ones country – the UK in my case, and divide its total energy usage – about 300GW INPUT – by the land area to get a ‘total radiative imbalance’ figure.
Its around 250,000 square kilometers, so to a first order that is about 1W/sq m.
Remind me again of what ‘forcing’ CO2 is supposed to have?
It could be met, with suitable storage of an entirely unspecified and imaginary nature, by covering the entire surface of the country with wind turbines – which average about 2W sq meter when not in the middle of a country entirely covered in wind turbines…Of course safety issues would mean that this would render the entire country permanently uninhabitable.
Side Note: I am glad Zombietime is seeking a decent answer to a good question here.
Zombietime is great.
So many of us democrats have bought the “McCarthyism” defense that “there are no communists here” that we are blinded to the take-over of our formerly American, decent political party. Zombietime is a resource for revealing to fellow democrats that, yes, great swaths of our allies in labor and environmentalism, and reproductive rights activists, are simply Un-American Marxists seeking to sow discord and bring down our nation.
If you have the choice between a coal power plant or solar panels, go for the coal power plant:
http://www.rnz.de/metropolregion/00_20131204060000_109802389_Solaranlage_Defekt_loeste_Ludwigshafener_Parki.html