Could huge solar farms have their own impact on climate? For instance, if a desert were to be half covered with solar cells that work at 30% overall efficiency (I believe that’s the theoretical limit?), it would mean the climate system over the desert is receiving 15% less heat. This seems like a number that would cause some noticeable changes in the climate. I suspect I’m talking rot, but would love an explanation for why this is so.
I suspect a solar would actually increase the heat absorbed by the desert, since the cells are black and designed to pick up as much radiation as possible. A light-colored desert sand would reflect more heat.
Either way, any heat captured as electricity would return to heat at some time in the future - every time electrical energy is used, there’s waste heat produced. We already see heat islands around cities, and that might be worth looking into for additional information.
Number of different effects at play I suppose. Conversion of solar energy to electricity, conversion to heat, reflection, absorption by atmosphere(hence reduction of CO2 levels would be important). Any educated guesses at what the dominant ones would be?
True, I’d meant local climate/weather systems.
Massive deployment of Solar panels in a small area will affect the immediate climate to some degree. If you half covered the Mojave you would probably kill the local ecosystem and it would be replaced by some other ecosystem based on shade loving sand plants. But it should be a small effect on the overall climate of the world.
Now on the other hand the whole idea of replacing coal and oil with renewables and nukes is too affect the climate and halt the increase in overall temperature that has been noted and connected with green house gas emissions.
A recent New Scientist article discussed the impact of “renewable” energy extraction on the environment. The author drew the conclusion that there is not much free energy (in a thermodynamic sense) in the atmosphere, and that extracting large amounts of energy from wind and waves could have major impacts on climate systems.
Solar is less problematic, but current technologies rely on rare earth metals that have limited supplies, and still have issues with heat loss.
Si
Why would you cover half the Mojave? Have you looked at real estimates of how much area total is needed for world/ US power needs, and miscalculated the sizes when changing units, or did you assume that because it’s represented as block area, that it must be done in a whole block?
Even the Desertec project is using the “total area square black pixel” for illustration only, the real plan is to build lots of small power plants, for several reasons:
Cheaper and quicker to build small ones than big ones; increasing any building project orders of magnitudes creates new and unforseen problems, so going with tested sizes makes more sense
Less security vulnerability: 50 small plants instead of one big means no terrorists can stop energy with one blow
spreading over several countries means income for different countries; less political vulnerability
Or is this another case of physics working differently in the US for solar again?
The Mojave was just used as a quick example of a well known desert, not an actual suggestion. I agree the best way to deploy solar is as south facing roofing on existing and new construction. The Op asked about deserts.
Um, I wasn’t speaking against deserts; the Desertec project aims for … the Sahara, as the closest desert for Europe.
The Mojave would be a good place to put 20 or 50 or 500 factories that together produce 90% or 110% of US total power consumption (in addition to wind, existing water, some geothermal, and storage solutions).
But it’s one of the dozen typical anti-solar straw men to state the “half the Mojave” would have to be covered by one monolithic array. Nobody sensible or knowledgable about solar plants would do that, or even suggest that.
So the answer to the OP question is “It’s irrelevant, because nobody wants to do that, it’s not necessary to do that, and it makes more sense to build small - to mid-sized solar power plants.”
Well, it was just an illustrative example. You’re right in saying that it’ll be smaller, spread out plants. I don’t see that the question becomes irrelevant though. Even spread out plants taking the same amount of heat energy out of the local climatic system suffice for my question. Lets restate it in a different way. The US energy requirement is roughly 3.3 TeraWatts. Lets say we manage to provide half of this from solar energy. This means 1.6 TW that would otherwise be converted to heat energy and have some sort of impact on the climate system of the US is now converted to electricity(although some of that will again be converted to heat, not all of it will, and the heat will be released in a different place). How will this affect the climate?
btw - Just to be clear, I’m a big fan of development of alternative energy sources including solar and believe weaning ourselves off fossil fuels is hugely important for humanity. So I’m not trying to put up an anti-solar argument here, just trying to understand the issue.
I could be way off base, but it seems to me that 3.3 Terrawatts is nothing compared to the amount of energy provided by the sun. Or, put another way, removing 3.3 TW of solar energy shouldn’t noticeably affect global climate. Local climate immediately around the plants, perhaps.
Wikiseems to back that up:
and
First, you may have heard of this thing called global warming. If we actually manage to take heat out of the system a bit, it would be a benefit.
Second, the sun delivers in about 20 min. the total world energy consumption, each day. So taking a bit away is a drop in the bucket.
Lastly, the “funny” thing is that nobody asks these things about other technological uses that also affect climate, only about alternative.
Nobody asks how miles of black asphalt highway in the desert raise the local temp., or what effect that has on wildlife, because highways are part of personal freedom to go where you want.
Nobody is concerned about hundreds of open swimming pools and fountains wasting thousands of liters of water by evaporation each day in Las Vegas in the freaking desert, (while simultaneously draining the aquifier), because that’s part of personal freedom to do what you like whether it harms anybody or not.
Nobody is concerned about the (measured) effect of cirrus clouds from airplanes (confirmed during the grounding after 9/11) and the disruption of weather patterns, because flying everywhere instead of taking other transport is part of personal freedom.
But alternative energy? Surely there must be huge risks associated with something untested socialistic like that! (Never mind that NASA played a big part initially in developing it). Not like clean, safe, reliable nuclear energy!
Well, from Wikipedia again
Now sure this sounds like a huge imbalance. But we’ll be generating energy only from that solar radiation which reaches land. Consider that 71% of the earth is covered by oceans, and 19% of all solar energy reaching from the sun is absorbed by the atmosphere. So human usage(547EJ) goes from <turns over an envelope> 0.01% of solar energy absorbed by land, water, atmosphere to
0.07% of the energy that reaches land. Ok. That little mathematical exercise seems to suggest that spread the solar power generation around a bit, and , unless such a small percentage can cause a significant change, we’re all good 
Gee. I hope that chip on your shoulder isn’t causing you too much discomfort.
If it makes you feel any better, I’m not worried about the environmental effects of alternative energy. I just think it’s inefficient, unproven, expensive and inadequate.
Isn’t that reason enough to stick to things like nukes?
Well, no, because it’s none of these things. Well, over here - it’s proven, reliable, efficient, cheap and adequate. But I’ve heard often enough that physics for some reason works differently for the US.
Eh? So of course we depend on ever more expensive and polluting fossil fuels because…actually I don’t know. You tell me.
Perhaps Wikipedia is wrong, but the page on the EU use of renewable energy does not seem to support what you’re saying. Even as a world leader in renewables, their goal is only 20% of the energy supply met with renewables of all sorts by 2020. Germany has the bulk of the EU’s photovoltaic capacity and yet provides just 200 W per capita in solar. Wikipedia’s page on energy costs shows that Germans pay nearly three times as much for their power as Americans ($0.30 per kWh compared to $0.11 per kWh).
Bing!!! We have a winner.
Progressive “green” thinkers need to be pro- nuclear, not anti-.
Yep. And if Septimus saying so isn’t good enough for you (and I, for one, don’t see why it shouldn’t be, upstanding sort that he is) , here’s long time ‘Green’ thinker Monbiot on the matter
The Mojave can’t support that much solar energy - it can’t even support the production plants that have been proposed and approved but not yet built. The original utility-scale plants proposed for the Mojave required water to as a coolant, but they’ve mostly been switched to dry-cool plants now. The dry-cool plants require a fraction of the water, but also run at a lower efficiency… and even those plants still require water to keep the reflecting surfaces and collectors clean.
There’s just not that much water in the Mojave, and what’s there has been over-allocated for decades. It’s a place that gets less than 4 inches of rain a year on average, and southern Nevada water rights run into hundreds of thousands of dollars per acre-foot (1 acre-foot of water is enough to produce just under 10 MW of solar power). You’ve got great solar exposure, but that’s not the only thing you need to produce solar power on that scale.