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
For me, reading all these comments is a stark reminder of just how little we really understand, or can accurately quantify, about the factors affecting our world’s climate.
True, we have some dodgy inaccurate climate models and are now spending almost $1.0 billion per day on trying to combat something inconsequential, which we can not accurately measure.
Can anyone doubt we live in a world gone mad?
“Zombie… with a question that he…”
________________________
…or would that be she?
A really good conversation on this topic. But many of the arguments. . . to me. . . are inch-bugging along the periphery of the critical question. Here it is: Were we (all of us collectively) in position to make the binary decision to either solely use (1) carbon resources (coal, gas, oil) or (2) equally efficient solar panels — to meet our global energy needs. . . which would have the greatest impact on global temperature. . . or alternatively the earth’s heat balance? I think I know the answer, but maybe I’m wrong.
What would Earth’s surface temperature be in a 100% CO2 atmosphere ?
I think We should be looking at things that will take our homes of grid. Things like using a rectenna insted of a of a antenna Most of the electrical appliances in our homes can be run on 12 volts just look at the modern day mobile home . They can stay of grid by using solar and a small generator for those cloudy days If we where to use a rectenna for reciving radio and tv signels we could capture the free electrons used to propergate the signel at the rectenna. At this time it is illegal for the public to use a rectenna, its regarded as steeling power People in the know have been using a small array to steel power from high voltage power lines and charging up their batteries. A rectenna works in the IR window and would collect power 24/7 night and day cloudy or not. Leave the electrical grid for industry were high power electric potential (work) is neaded . Just think how much money would be saved if their was no power lines in residential areas no polls no matenence and no ozone emitting transformers This idear was created by Tesla to supply free energy to the people . We need to use all the tech’s avalible and scale them down so we can use them on our homes. We don’t need a wind turbine that creates terrawatts of power to sit on our roof we only need enough power to charge up 12v batteries
” A rectenna is a rectifying antenna, a special type of antenna that is used to convert microwave energy into direct current electricity. They are used in wireless power transmission systems that transmit power by radio waves. A simple rectenna element consists of a dipole antenna with an RF diode connected across the dipole elements. The diode rectifies the AC current induced in the antenna by the microwaves, to produce DC power, which powers a load connected across the diode. Schottky diodes are usually used because they have the lowest voltage drop and highest speed and therefore have the lowest power losses due to conduction and switching. Large rectennas consist of an array of many such dipole elements.” http://en.wikipedia.org/wiki/Rectenna
Temperature is electric potential at work
There will be some minor local effect, just like when someone builds a chicken coop. Collectively, everything we do doesn’t amount to a hill of beans against the backdrop of the planet and its climate. Build all the solar whatevers in the desert that can be built and it won’t make a bit of difference, in the end.
Well you not have this problem at night, so the solar panels array will need to be 50% larger. Additionally the panels array will need to be larger due to the low sun angle in the morning and evening…. and cloudy days….
Say you could offset the panel array with mirrors on the unused part of the desert.
Why doesn’t Zombie just go to Ted Turner’s massive (ratepayer funded) solar farm in NM and get some answers.
The coal fired power plants operate at best 40% thermodynamic efficiency. That means 60% of the energy relessed from burning the coal goes into the atmosphere. That heat is much more than tiny difference PV makes. Don’t worry about CO2 as we really have no idea what the true forcing is.
The real problem with PV is it only works when it’s light outside. To keep the country running that won’t cut it. So we run generators to back up the PV installation24/7. Now how efficient can that be? In sunny areas I can believe the use of PV to peak shave the load in the afternoon on hot days can be effective. But at what cost? Any other use except for remote areas is senseless.
That’s my two cents,
Barry Strayer
Actually the panels will be casting a huge amount of shadow, and are reflective in many wave lengths. A fraction of the energy is of course converted into electricity and shipped out to consumers and industry. My bet is that if you walked under the panels, it would be noticably cooler. The heat re-released as waste heat from electrical power usage is very dilute. The real issues are do we want solar panel clutter in our open spaces,a nd waht impact will these uneconomical panels have on native wildlife adapted to strong sun, not strong shade?
The correct answer is: we don’t know!
Zombie wants to know the result of a climate model on a regional scale. However, all current climate models do not have any regional skill. It is not, as some commenters suggest, a simple back-of-an-envelope exercise, as it invokes many unknown feedback mechanisms of which water vapour is the biggest unknown on a regional scale.
Robertvd says: “What would Earth’s surface temperature be in a 100% CO2 atmosphere ?”
Thanks to Venus, this is easily calculated. Venus’s atmosphere is 99% CO2 and its temperature is 735K (462C). It is 0.723 Earth’s distance from the Sun. Therefore Earth’s irradiation is (0.723)^2 = 0.523 of Venus’s. Therefore if Venus was placed into Earth’s orbit, its temperature would be 735K x 0.523 = 384K = 101C. So there’s your answer.
111C, that is. (384 – 273 = 111)
More John Morpuss stuff huh?
John, big foot went that-a-way ——>
.
Certainly there is a model that than calculate, er, project/predicate this?
Anthony , mods – this John Morpuss guy may seem harmless, but he is stinking up the joint.
I’m going to feel compelled to rebut some of his silliness if it is allowed to stand .. just a heads up, guys.
O. H. Dahlsveen says:
December 10, 2013 at 1:08 pm
Reading through some of previous comments I get the impression that some people – who should know better – do think that a ‘motor-car’ or automobile, if you like – can run on its own exhaust fumes.
++++++
That’s already been done, and was a popular troll topic on automotive forums a couple years ago.
http://www.autoblog.com/2007/11/16/asinine-engineering-direct-exhaust-injection/
Well the hard number I saw for the greenhouse effect was 1.7 Watts extra heat at the surface due to CO2 whereas a solar panel will obviously produce much more than that by generating power which always ends up as heat. They have an efficiency of about 18% but I guess the reflectivity is low say 30% as opposed to 80% for a desert area so you are going to get 78% of incoming radiation converted to heat per square meter which is gonna be about 900 Watts for North Africa against say 300 Watts for bare desert. So I guess you are producing an extra 600 Watts per square meter of global warming for every 200 Watts of power at midday. So a megawatt of electrical would result in 3 mega Watts of warming. More for the “Absolute Black” Panels.
So roughly speaking solar panels produce about 300 times the warming that CO2 supposedly does per square meter. So if you keep the solar panel area less than 1/300th the land area of the planet you will not warm up the planet as much as CO2 does. Of course if you allow for night and cloud cover solar panels capabilities come down somewhat so maybe you need to keep coverage down to less than 1/1000th of the land area or about 44,000 sq kilometers.
I’m gibbering now. Time for bed.
Good start Willis. I love the way you think and the math skills you have!
However, IMHO gases like CO2 and materials like silicon dioxide (glass, sand) and silicon (with a glass cover layer) may all have different albedos (reflectivities), but they also have different absorbances of the suns energy and different emissivities. Absorbance plus emissivity then would be a second source of heat shedding difference between a “solar panel” and a change in CO2 caused by a power plant.
I have a question for Zombie to help us sort out the issue:
What specific type of solar panel were you thinking of? I think everyone is assuming silicon solar cells, but solar panels also come in other varieties each of which have different solar energy absorbances, reflectivities, and emissivities. For example, if the solar panel is designed to heat up a fluid for driving a turbine, then it will be designed with mirrors (high reflectivity) and/or glass tubes (low reflectivity) that has very high solar absorbance. In contrast the outer glass layer on a silicon solar cell will have low absorbance and be optimized to transmit as much of the incident solar energy that matches silicons to optimize conversion of light to charge carriers. See for example the following lectures:
http://www.lehigh.edu/imi/Glass_In_Energy/Lecture4_GlassesForSolarEnergyI.pdf
http://www.lehigh.edu/imi/Glass_In_Energy/Lecture5_GlassesForSolarEnergyII.pdf
http://www.lehigh.edu/imi/Glass_In_Energy/Lecture6_GlassesForSolarEnergyIII.pdf
This last lecture in particular, has a lot of good information about solar cells.
You have to dig for it but a good series of lectures about solar irradiation absorption and losses pertaining to gasses. (vegetation, soils and sand) can be found in this interesting series of chapters/(lectures?):
http://www.ssec.wisc.edu/library/coursefiles/01_history.pdf
http://www.ssec.wisc.edu/library/coursefiles/02_radiation.pdf
Especially, this chapter!
http://www.ssec.wisc.edu/library/coursefiles/03_abs_emiss_ref.pdf
In this chapter Figure 3.1 shows the reflectivity (albedo) for “Sand, desert” to be
“25 – 40” %. This means that the absorbance is most likely 60 – 75% across the spectrum.
I found a figure for the radiative emissivity of sand equal to ~.95 – .96
Finally, in addition a power plant’s inefficiencies are most often lost in the form of heat. So a better stab at the power generator’s contribution would be to assess that the conversion of potential energy in the fuel that does NOT go into generating the power, gets converted to some form of heat, and add that to CO2 side of the equation.
What I never see is the analysis of the battery arrays (massive) needed to effectively store the power generated during the likely no more than 10 hours a day of effective energy gathering (even in deserts) so the output power can be provided 24/7. This is needed if solar is ever to replace base power stations, and not just be used for extra capacity in afternoons. (Or massive arrays across the entire planet and a global solar array/energy transport system to provide energy 24/7 around the world, haven’t seen this proposed either. I’m sure someone must have done the larger scale analysis. Or is there some other answer to energy storage. Environmental damage from manufacturing and set up of Terrawatts of batteries, with servicing and replacement is not ignorable either.
@ur momisugly Jim Your either part of the sollution or part of the problem. and I’m starting to see you as part of the problem. Seeing your responce adds nothing apart from insults mabe the same mod that deleted my other answers could do the same to you . It will be good to see if this forum is fairdinkem or just another propaganda site for the sheep.
Best perspective by Roy Spencer – the uncertainties are so great, we do not know whether it will cool or warm. For some results of conventional modeling see:
The potential for air-temperature impact from large-scale deployment of solar photovoltaic arrays in urban areas, Haider Taha, Solar Energy Volume 91, May 2013, Pages 358–367
Energy from the Desert: Feasibility of Very Large Scale Power Generation (VLS-PV) Systems edited by Kosuke Kurokawa. Routledge, May 4, 2012 – Technology & Engineering – 236 pages; see discussion on albedo
Meteorological, emissions and air-quality modeling of heat-island mitigation: recent findings for California, USA Haider Taha Int. J. Low-Carbon Tech. (2013) doi: 10.1093/ijlct/ctt010 First published online: April 4, 2013
Robertvd says:
December 10, 2013 at 2:35 pm
What would Earth’s surface temperature be in a 100% CO2 atmosphere ?
—
Basically the same as it is now. Catrefully check what EWF proposes, he is assuming a Venus, I find that logic not correct. The vast majority of Venus’s high surface temperature with 96.5% CO2 and 3.5% N2 is due to the high unit columnar mass.
You more have something more like this:
Ts.earth = ( (10332*0.0153 + (1362/4*(1-0.30)) )/‹kSB›)^(1/4) = 289.2 K
Ts.venus = ( (1051000*0.0157 + (2614/4*(1-0.90)) )/‹kSB›)^(1/4) = 735.2 K
The first value is the mass of a unit atmosphere column. The 0.0153 and 0.0157 are the approximate number of watts abosorbed/reflected per kilogram as the surface flux travels upward (Beer-Lambert related). The tail calculation is the respective OLRs entering and leaving, in and out per their TSI and albedoes, and that radiation power is then converted to equivalent surface temperatures.
Using Earth with Venus’s W/kg value gives:
Ts.earth = ( (10332*0.0157 + (1362/4*(1-0.30)) )/‹kSB›)^(1/4) = 289.9 K
a 0.7°C rise all else assumed the same.
Zombie: Good question, and worth some back-of-the-envelope calculations.
Note to others: I am using “mainstream” assumptions and analytic methods, which I don’t care to debate – substitute your own if you don’t like mine. Zombie appears to want to use methods his green friends will accept.
In a low-latitude desert, peak solar insolation at the surface is about 1000 W/m2. A rule of thumb for this is that you have the effective equivalent of this for 8 hours out of the 24 hour day, so averaged it is 333 W/m2.
Desert surface albedo is generally given as about 0.40, so 60% of this is absorbed, or 200 W/m2, with 133 W/m2 reflected back to space (averaged over a full day, of course).
A photovoltaic panel will have an albedo of about 0.10, so 90% of this is absorbed, or 300 W/m2, for an increase of 100 W/m2.
The panel will have an overall electrical conversion efficiency of about 15% (maybe 20% at the panel itself, but you lose about a quarter of this in processing and nighttime storage). So averaged over a full day, you can generate 333 * 0.15 = 50 W/m2 (half of the extra power absorbed).
For the 1 MW generating capacity you ask about, you would require 20,000 m2, and this would cause 2 MW of extra power absorption by the earth. (Note that the 1MW converted to electrical power is not thermalized at the panel, but it will eventually be converted to thermal power.)
Let’s compare this first to a 1 MW coal-fired plant operating at 40% conversion efficiency. As it produces 1MW of electrical power, it is producing 1.5MW of thermal power for a total of 2.5MW additional thermal power liberated from the chemical bonds in the coal. A little worse here than the solar panels on this count.
But what I think you are really asking is how the (supposed) warming from the CO2 emissions would compare to the warming from extra albedo. Here you cannot make such a direct comparison, because, in the mainstream analysis, at least, the effects of added CO2 are cumulative. Let’s go through the analysis:
Typical CO2 emissions for coal-generated electricity are usually given as 1000g/kWhe, that is, 1.0kg of CO2 for each kilowatt-hour of electrical energy generated. One kWh is equal to 3.6MJ, or 3.6MW*sec. So to generate at 1MW power, you would generate CO2 at 1.0/3.6 = 0.278 kg/sec.
But by mainstream greenhouse theory, the added power is a function of the resulting concentration of CO2, not by its rate of change. So we have to see how this added CO2 accumulates over time. We’ll use a period of 20 years.
0.278 kg/sec for 20 years comes out to 1.74×10^8 kg. It is generally accepted that about half of the added emissions stay in the atmosphere short term, so will have added 8.7×10^7 kg at the end of 20 years. Various sources give the total mass of CO2 in the atmosphere as about 3.16×10^15 kg.
In mainstream climate science, the key equation for the added “radiative forcing” is:
DeltaF (W/m2) = 5.35 * ln (C/C0)
where C0 is the reference concentration and C is the new concentration. To use concentration values, we would need to divide both numerator and denominator by the total atmosphere, but those operations would cancel out, so we can just use the mass numbers. So we get
DeltaF = 5.35 * ln ([3.16×10^15 + 8.7×10^7] / [3.16×10^15])
DeltaF = 1.47×10^-7 Watts per square meter of the earth’s surface
The earth’s surface area is 5.15×10^14 m2, so the added retained power at the end of the 20 year period would be:
DeltaP = 1.47×10^-7 W/m2 * 5.15×10^14 m2 = 76 MW
Over the 20 years, this added power level would steadily increase (roughly linearly) from 0 to 76 MW. Even using half of this value results in a much larger value than the added solar absorption of PV panels. So you could not use this basic analysis to make the point you want to make.
The latest combined cycle gas turbines (CCGTs) put out about half the CO2 of coal plants per unit of electrical energy generated. Simpler open cycle gas turbines (OCGTs) put out two-thirds (or more) of the CO2 of coal plants, half again as much as the CCGTs. But OCGTs can be ramped up and down much more quickly, so they are used where there are large amounts of variable renewable power. Close analysis of real electrical grids indicates that heavy use of renewables may not be reducing CO2 emissions at all due to the need for lower-efficiency backup.
Thought about it a long time ago, but didn’t get far. My WAG is that the efficiency is what matters, and that when the efficiency is high enough to compete with fossil power plants, then it will produce less heat.
It depends on the waste heat of burning fossil fuels, the residency time of GHGs, and the log forcing of GHGs. Where it really gets difficult is the maintenance and life of solar sources which are really unknown.