Guest post by David Middleton
From the Department of All Things Ironic…
Solar panels, while they mitigate the effects of global warming by replacing fossil fuels, can add heat in the locations where they are installed, reports a team of University of Arizona researchers.
At first blush, the experimental results, published Thursday in Nature Science Reports, seem to contradict computer simulations that said solar photovoltaic arrays, by intercepting some of the sun’s warming rays and converting them into electricity, would have a cooling effect.
The UA researchers measured the heat-island effect of a solar array at the UA Tech Park at Rita Road and Interstate 10. They found that its overnight temperatures were about five to seven degrees (Fahrenheit) warmer than a nearby plot of undisturbed desert.
Additional experiments are being conducted to determine the potential effect of the measured heating on nearby communities and the overall environment.
[…]
Following the Standard AGW Scientific Method, the observations are consistent with the model, despite being contradictory…
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Results from the team of current and former UA researchers, which included Alex Cronin, Rebecca Minor, Nathan Allen, Adria Brooks and Mitchell Pavao-Zuckerman, are not inconsistent with published computer simulations, said a Colorado atmospheric scientist.
Aixue Hu, research scientist at the National Center for Atmospheric Research, published conclusions from a computer model last year in Nature Climate Change.
Hu found that installations of vast arrays of panels in desert areas would produce a cooling effect of about 3.5 degrees Fahrenheit.
Contacted by phone Thursday, Hu said his study was predicated on highly efficient PV panels that would convert 30 percent of the sun’s energy into electricity. The panels in the UA study had an efficiency of about 20 percent. Hu said his model might produce some slight heating at that efficiency.
[…]
The Nature Science Report found that the Photocoltaic Heat Island (PVHI) effect was actually quite significant. A 1 MW PV plant routinely caused 3–4 °C of PVHI.
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The PVHI effect caused ambient temperature to regularly approach or be in excess of 4 °C warmer than the natural desert in the evenings, essentially doubling the temperature increase due to UHI measured here. This more significant warming under the PVHI than the UHI may be due to heat trapping of re-radiated sensible heat flux under PV arrays at night. Daytime differences from the natural ecosystem were similar between the PV installation and urban parking lot areas, with the exception of the Spring and Summer months, when the PVHI effect was significantly greater than UHI in the day. During these warm seasons, average midnight temperatures were 25.5 + 0.5 °C in the PV installation and 23.2 + 0.5 °C in the parking lot, while the nearby desert ecosystem was only 21.4 + 0.5 °C.
The results presented here demonstrate that the PVHI effect is real and can significantly increase temperatures over PV power plant installations relative to nearby wildlands.
[…]
How many MW of solar PV have been installed in the past 8 years? How much total PVHI has this yielded? Will this have any effect on our government’s mindless obsession with solar power?
References
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Except that solar panels are optimized to collect as much of the available solar energy as possible. As such they will heat up more than other dark materials like asphalt, which BTW, gets lighter over time.
Hi Paul,
Yes, I fully agree. It’s exactly what I meant in the last paragraph of my former message.
Have a great day.
Massimo
If we used unicorns to convert sunlight to electricity our computer models would be correct
Using electricity – whatever its source – produces heat, e.g., lights and electric motors. So funneling electricity into high-density urban environments must add to the UHI effect induced by sunlight and motor vehicles.
Who knows though. There might be a latitude at which the lower libido of the panels actually radiate away more heat than they add when illuminated. Here is a thought experiment: Take the entire electrical power requirement (even desirement) ~2.5 TerraWatts? Take the average albedo of the Earth land mass (~0.2?) and solar panels (~.1?). Let’s assume the average illumination is 600 watts (clouds) * (1/2) (day/night) * ((Pi * r2)/(2 * Pi * r2) (disc over half sphere) per square meter = 600 /4 = 150 watts/m2. Let’s assume 33% conversion efficiency so that we get 50 watts of electricity from ever square meter of panels. 2.5X10^12 / 5X10^1 = 50 billion square meters which would be a square land mass 224 kilometers on a side. There are ~150 trillion square meters of land on Earth. So the arrays would take 3 parts in 10,000 of the total earth land area, but lets say 1 parts in 1,000 to exclude Antarctica and other inaccessible areas. So if that one part in a thousand were covered by photo-voltaic arrays, and the albedo was half of the natural terrain, perhaps we could expect a tenth of a degree effect one way in the tropics and perhaps a tenth of a degree the other way above 45 degrees latitude. But the effects would be concentrated in areas with a lot of panels – a heat island. I don’t think it would be a big deal either way.
If your panels have a low libido, perhaps you aren’t spending enough time with them.
Take them on a date. Dinner, a good movie. That should help.
Assume 33% efficiency?????
The theoretical maximum is 31%.
The best laboratory results are only in the mid 20’s.
Real world cells are 20% and lower the first day out of the factory and drop off from there.
You are forgetting that these panels aren’t being placed randomly, they are being placed where the sun is the strongest. This usually means deserts as close to the equator as you can get.
Additionally, these deserts also have much lower than average albedo.
Japan plans to build it’s own Heat Island.
“The Japan Aerospace Exploration Agency is working on several models for solar-collecting satellites, which would fly in geosynchronous orbit 36 000 kilometers above their receiving stations. With the basic model [top left-hand side], the photovoltaic-topped panel’s efficiency would decrease as the world turned away from the sun. The advanced model [top right-hand side] would feature two mirrors to reflect sunlight onto two photovoltaic panels. This model would be more difficult to build, but it could generate electricity continuously.In either model, the photovoltaic panels would generate DC current, which would be converted to microwaves aboard the satellite. The satellite’s many microwave-transmitting antenna panels would receive a pilot signal from the ground, allowing each transmitting panel to separately aim its piece of the microwave beam at the receiving station far below.Once the microwave beam hits the receiving station, rectifying antennas would change the microwaves back to DC current. An on-site converter would change that current to AC power, which could be fed into the grid.”
http://spectrum.ieee.org/green-tech/solar/how-japan-plans-to-build-an-orbital-solar-farm
“Scientists at Georgia Tech have found a way to turn light directly into electricity with a device called an optical “rectenna”. ”
http://www.greenoptimistic.com/rectenna-light-electricity/#.WAfnlv__r0M
You’ve got to be kidding: “solar photovoltaic arrays, by intercepting some of the sun’s warming rays and converting them into electricity, would have a cooling effect.”
Thermodynamics pretty much declares that every step of the process has to be exergonic. Why do they continue to pretend that it does not apply? Their computer simulations are frauds and they need to have their grant money revoked and sued for the money that they have spent on crap science. They would not pass my high school physics course.
The wonder is that they could figure beforehand that < 0.1 albedo objects (solar panel) would rise temp in sandy, ~0.4 albedo area (see wikipedia "albedo") . You need at least 30% efficiency panel just to offset the albedo effect !
New age "science", once again