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
PV panels have a surprisingly high albedo, approx. 0.3*
Desert sand has an albedo of approx. 0.4**
The difference isn’t as dramatic as you might expect.
*http://www.treehugger.com/clean-technology/ask-pablo-do-solar-panels-actually-contribute-to-climate-change.html
**http://en.wikipedia.org/wiki/Albedo
As to roof mounted solar panels, they would obviously be no worse off than a black shingled roof, but here the economics are horrible, owing to the cost of labor installing the panels plus the
sad fact that normally a roof needs to be reshingled before the panels wear out, requiring another installation after a de-installaion. I found the costs of this type of solar to be perhaps 5 to 10 times that of nuclear.
Not to worry, almost all of the project hype on Federal lands is just hype and not actual projects. The tortoise and the paperwork will render those numbers just political progress. Beyond that, the largest solar project underway in the world (Topaz) is one in which the private developers had to agree to hand over the property in total to a conservancy group at the end of the power purchase agreement. There are not many projects prepared to do that. It amounts to peak solar in effect.
nemet dissertation in full:
https://mywebspace.wisc.edu/nemet/web/Nemet_Ch5.pdf
The formerly laudable Scientific American had a short article on the albedo effect of solar panels.
http://blogs.scientificamerican.com/solar-at-home/2009/10/27/the-albedo-effect/
Not immediately going to disagree with you, but list your assumptions please, and show your calculations. I get far, far more land required.:
1. On the equator, at 30 degree latitude, 45 degree latitude, and 60 north latitude, your calculation will be very, very different.
2. Are you using the “rated” instantaneous output of the assumed solar power plant (at noon, at mid-summer’s maximum sunshine level, with perfectly clean solar panels on a perfectly clear day?)
3. Solar power is only available 6 hours a day (9:00 AM through 3:00 PM (effectively) and generally loses 1 day in 4 to bad weather and clouds/dust/aerosol losses, but the nuclear plant is producing power 24 hours a day. How do you account for the “lost hours” when a solar plant is not producing power to the grid?
4. If storing power, all methods require accepting 80% – 85% conversion factor (going FROM the solar DC power INTO the storage, then another 80-85% conversion efficiency coming BACK from the stored energy BACK INTO the grid. (Pumped storage, for example, requires more energy go INTO the pump motor and MORE losses inside the pump impeller INSIDE the pumps, evaporation and ground water seepage losses in the stored lake at high elevation, friction and pump efficiency losses both ways in the pipes going to and from the pumps. The water is now stored at high elevation, and undergoes even more losses going back into the impeller and impeller piping when drawn down, then electrical generator losses inside the generator and converter and transformers going back to the grid.
Good question my friend. No, I do not believe (simply because I have found no proof thereof) that anybody have ever done any calculations (all the necessary correct numbers are missing – or not available due to lack of all the correct, or necessary, research)
Back radiation does exist – of course it does – But c.mon guys how many times can solar energy warm the Earth’s surface?
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. Once energy has been used – in our case – to warm the earth’s surface – that’s it. The fabled “Back Radiation” is impotent and has no power to penetrate another medium, thus causing increased atomic movements
Roy Spencer says:
December 10, 2013 at 12:21 pm
the proportion of the Earth covered by solar panels is vanishingly small, and will remain very small in the future. So the panels’ “extra heating” effect will pale in comparison to CO2-induced warming…assuming that warming is non-zero, of course. 😉
Reg, yes ocean warming leads to more evaporation, and more precipitation. This effect is already contained in the climate models. The effect on cloud formation, though, is a huge wild card. The reason why is that all ascending air in clouds has to be balanced by descending air, which is usually cloud-free. So an increase in the atmospheric hydrologic cycle can lead to either more or less cloudiness. I predict more (a negative feedback on warming), the models say less (positive feedback on warming)…but no one really knows for sure.
Dr Spencer – what is the time scale? IF more leads to less or less leads to more clouds?
The surface area involved is negligible. The excess heat (as little as there is) just gets radiated back into space anyway. That’s the skeptics’ point, that “forcing” is so small that it makes no practical effect compared with natural variations. Maybe you could use this angle to make a rhetorical point using the warmists’ own perspective, so long as your own thinking stays clear.
We also need to consider male demograhics, an older population with more baldy patches will alter the human albedo quite a bit. Plus as more people reject CAGW as an ideology, the ‘white hatters’ will become more prevelant, leading to an increased albedo and to a frenzied ‘tipping point’ ice age
I did a similar calculation on electric cars a few years ago, as these are essentially “coal powered vehicles “, as the bulk of electricity is generated by coal. I really expected to find that from a net CO2 emissions standpoint that they would less efficient than gas powered engine, however, when I crunched the numbers , I did find they had a net benefit in reducing CO2 per mile driven (assuming that is actually beneficial ). Not dissimilar to the conclusion RERT reached on solar panels (using a reasonable sensitivity at that ).
parks says on:December 10, 2013 at 12:33 pm:
“I read somewhere that the energy used for all the stages from mining the raw materials, processing, manufacturing, logistics/transportation,”
Yes, energy wasted to prove that energy is used wastefully by us peasants is essential to make us see the error of our ways
Well, I have a bit of experience in these kind of back-of-the-envelope estimates …
I’ve taken the following information from the reference above:
That plus some constants gives us the information we need to calculate the change in heating (in watts per square metre [W/m2]). The calculations look like this:
PHOTOVOLTAIC CALCULATIONS
18750 = km2 solar cells
1.88E+10 = m2 solar cells
5.11E+14 = m2 earth area
0.004% = of total earth area
35% = albedo of sand
7% = albedo of solar cells
28% = increased absorption
0.001% = global increased absorption
342 = W/m2 incident sunlight
0.004 = W/m2 total heating from reduced albedo
CO2 CALCULATIONS
1 = gigatonne reduction in CO2
0.27 = gigatonne reduction in C
9 = gigatonnes total human emission C
8.73 = gT with PV
2.13 = gigatonnes per ppmv
45% = airborne fraction
1.90 = ppmv increase w/o PV
1.84 = ppmv increase w/PV
390 = ppmv CO2
391.90 = next year w/o PV
391.84 = next year w/PV
0.0070 = log change w/o PV
0.0068 = log change w/ PV
0.0008 = W/m2 at 3.7 watts/doubling CO2
0.0007 = heat generation (see below)
0.0014 = W/m2 total heating from fossil fuel generation + CO2
HEAT GENERATION FROM ONE TERAWATT PEAK
10% = typical load factor (capacity factor) for PV system
1.00E+11 = watts average from 1 TW peak
8.77E+14 = watt-hours annual actual generation
30% = generation efficiency
0.0007 = W/m2 from fossil fuel combustion
So to my surprise, the two options are of the same order of magnitude, and the extra heat absorbed by the PV (.004 W/m2) is about three times the forcing change of the CO2 emitted.
Spreadsheet here. I invite people to check my figures, I’ve been wrong before …
w.
I was going to reply, but there is no need. Roy has already pointed out that we’re talking a negligible fraction of the Earth’s surface at best. Even if you raised the temperature of the entire converter array surface compared to what it was before by 10C it would be essentially invisible against the overall average temperature, even allowing for some downwind elevation as well. We will never ever cover 10%, or even 1%, of the Earth’s surface in solar cells, that is.
Even so, it looks like somebody has published quantitative estimates because there could well be a local warming as a variant of sorts of the UHI effect. If one replaces green trees or green meadowlands with solar cells one will likely get a different delta than if one replaces south-facing asphalt shingles on rooftops with solar cells, so quantitative estimates probably have to be done on a very much ad hoc basis for each given case. CO_2-linked warming, however, is global in extent, not local, so one cannot really compare the two by asserting that solar cells create “more warming” than CO_2. Where they produce a UHI-like effect, sure they do. Everywhere else, their net impact could be almost invisibly small but negative to the extent that they displace CO_2 sources and the climate is moderately sensitive. As Roy also pointed out, the specific value of the climate sensitivity is far from clear at the moment as best estimates are in free fall as long as “the pause” continues.
But in the end, one doesn’t need complex arguments. All one needs to do is look at the map:
http://en.wikipedia.org/wiki/File:Solar_land_area.png
This map is assuming 100% of the Earth’s energy consumption is being provided by solar cells at 8% efficiency, allowing for the mean insolation at the locations shown. Of course this doesn’t allow for storage or transportation, but then, we are a long, long ways away from providing 100% of the Earth’s energy via solar power. OTOH, it isn’t clear that PV cells are ultimately the most efficient solar technology, and there are efforts underway to build solar concentrator generators that would have much higher efficiency and that would reduce the absorptivity of the collector area compared to almost anything. Upward facing mirrors that rotated vertically at night to let the ground underneath cool would have a strong local (negligible global) cooling effect. No matter how you slice it, though, we won’t even be able to cover 0.01% of the 30% of the Earth’s surface that is land area, if we work for decades at it. So whatever happens to the local temperatures on those sites, it is going to be a negligible contributor to AGW or AGC either way.
rgb
I had a good laugh when I read this.
I live in a small town in Victoria and a couple of years ago, I wrote a letter to our local paper about this very thing.
I had done a rough, back-of-the envelope calculation using the estimated size of a solar collector large enough to replace all coal fired generation on Earth and then estimated the amount of waste heat that would be generated. From that I got an atmospheric temperature increase of about 4 degrees C. The number is almost certainly nonsense, like so much of ‘climate science.’
One of the local greenies responded and said I was wrong. He said solar panels “would have a slight cooling effect.” So help me, the man’s a SCIENCE TEACHER!
I wrote back, suggesting an experiment: I suggested he put a solar panel out in his backyard on a nice hot day, connect it up and let it run for several hours, then go out and pick it up.
I recommended he wear gloves.
Pat
The book SuperFreakonomicsbrought up these issues, and they caused some discussion:
http://www.realclimate.org/index.php/archives/2009/10/an-open-letter-to-steve-levitt/
Reg Nelson says:
December 10, 2013 at 12:02 pm
My question is this: If the planet is warming, and two thirds of the planet is covered by water, wouldn’t this lead to greater evaporation…?
No. The reason being that the missing heat has been supposedly magically transported to the lower ocean depths where it of course cannot evaporate (or be detected at present – but hey, have faith). The surface temps show no rise of late.
Zombie asks a good question regarding PV panels. Similar questions have been asked about the effect of wind power altering atmospheric circulation if the 17 tetrawatts was extracted by turbines to replace current fuels.
http://scitizen.com/future-energies/natural-limits-to-world-wind-energy-_a-14-3695.html
http://www.telegraph.co.uk/earth/earthnews/9234715/Wind-farms-can-cause-climate-change-finds-new-study.html
With regard to PV panels with lower albedo than the surface placed in a desert the answer would be net warming. Under 20% of visible (SW) spectrum is converted to electricity by PV panels. Some solar radiation is reflected but the SW, UV and IR absorbed directly heats the air at the panels location. The small amount of electricity transmitted from the panels eventually becomes heat at a separate location.
But what of the reduction of CO2 warming? There is no reduction. CO2 is a radiative gas. Adding radiative gases to the atmosphere does not reduce the atmospheres radiative cooling ability.
However just like wind turbines, the environmental impact of PV panel manufacturing should also be considered. Look at the neodymium mines in China producing the magnets for bird blenders –
http://www.dailymail.co.uk/home/moslive/article-1350811/In-China-true-cost-Britains-clean-green-wind-power-experiment-Pollution-disastrous-scale.html
Now look at a typical subsidised PV installation on a suburban home. Too few panels to power the house. Typically no storage. Electricity being “sold” back to the grid, destabilising the network. And all mounted on an aluminium frame that took 11 megawatt hours per tonne just to smelt excluding mining and transport. Will those cheap, dirty, de-laminating Chinese panels ever produce even the energy to manufacture the aluminium they are mounted on? How is China dealing with pollution of manufacturing of polycrystalline silicone? Lets check that as well –
http://www.washingtonpost.com/wp-dyn/content/article/2008/03/08/AR2008030802595.html
The only justifiable use for PV and wind power is to provide power in remote locations. The real environmental impact of these technologies is far too great to justify replacing natural gas or full base load thorium power for our near future energy needs.
I am happy to see this being discussed. Always had a gut feel that, if on a scale large enough to fix the ‘CO2 problem’, there is that effect on the total energy budget. There is not really any free lunch. Similarly, if enough wind farms are installed, all that wind will also not be dong what it used to.
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.
The asphalt number came from a (probably inaccurate) factoid on the History channel this morning. The 200 square mile figure comes from a lecture given by solar proponents at the University of NM a couple of years ago. Their claim was that *all* of the electric power needs of the US could be satisfied by high efficiency, 30% plus, solar cells covering 100 sq. mi in Nevada and another 100 in NM. They changed the subject when they were asked about power use at night.
I think everyone on any side of this debate understands that the warming from an albedo change caused by solar panels would be vanishingly small. As would the warming effect of a single coal plant’s CO2 emissions. The question is not relevant when discussing actual temperature effects on the atmosphere.
However the question he asked as to the difference between the two is relevant to the climate discussion because policy is being used that proposed solar energy will have less effect on heating the earth than coal emissions of CO2.
Off thread = I guess – but:
[link removed.]
try it.
Thanks.
[No. Either the wrong link was attached, or you do not understand the purpose of this site, and “off-topic” topics. Mod]
Thanks everyone for your comments. Most appreciated! I’m going to bookmark this page and carefully digest each one of them over time. If a link/reference from your comment is used in my article (presuming I ever write it), proper citation (of your user name) will be given. Thanks!
Also off-topic, but of interest as a comment on scientific journals
http://www.theguardian.com/science/2013/dec/09/nobel-winner-boycott-science-journals
1. A kilowatt of heat produced by electricity generated by a coal powered plant warms the earth by the same amount as a kilowatt of heat produced by a PV array.
2. Heat is wasted in the coal powerstation so additional heating occurs there.
3. Then a calculation is needed to identify how much heat per KWH lifetime capacity is liberated in the creation of a coal Power station vs a PV array.
4. Then a similar calculation for lifetime CO2 for each lifetime KWH
5. Now calculate how much sunlight is blanked out by smoke and steam from the coal powersation ie cooling vs increase IR/albedo feedback from the released soot, water vapour and aerosols.
6. Then as a shortcut calculate the amount of heat generated by all coal powered powerstations and realise it is a trivial amount compared to global insolation, but may well contribute to some significant UHI effects.
7. Have a stiff drink and think about wild geese.
PS Do PV arrays on roofs in hot countries reduce the use of airconditioners in attics?