You have to distinguish between two types of solar energy: photovoltaics (the panels you put on your roof for example) and concentrating solar thermal - big mirrors that gather heat from sunlight to heat water to be used in a thermoelectric plant. As you might guess, concentrating solar thermal requires tons of water for steam for generating and for cooling - more so than natural gas or coal unless dry cooling is used which cuts water usage by 90% but also cuts efficiency and costs more.
On the other hand, photovoltaics require little water, the least of all in renewable energy except for wind powered generators. How much water? Enough to clean the dust (or smoke in some places) off the panels. My brother, Paul Tolbert, who lives in Upland, California installed solar panels on his home this past winter. Here is what he said about cleaning the panels:
"My installer estimated cleaning every 6 months. But it depends on where you live. EP may have less soot/smog than I have. My panels have been up 6 months (since mid Feb) and don’t need cleaning so far. I recently checked and my electricity generation has not dropped. (However, a couple of recent smoky days may change this). Google says to clean the surface of a solar panel much like you would clean your car -- with warm water and dishwashing soap to remove any accumulation of dirt and grime. I plan to use a long handled squeegee."
6 months and he is going on 7 now without a drop in generation! A bucket of soapy water, a squeegee (a jug of wine, a loaf of bread . . .) We aren't talking about much water.
[Just a word about wind powered generation. Those spinning blades do kill birds but far less than my cat, Aristotle, and his feline friends from coast to coast do, and far less also than power lines, window panes, pesticides, automobiles and lighted communication towers. Tens of thousands by turbines versus millions by the other causes. Newer turbine technology is reducing the number even more. Sorry, oil industry cronies.]
The process for making the solar panels like all industrial processes requires some water. Still, panels use less water from production to installation to service than thermoelectric plants driven by gas, coal, concentrating solar thermal technology, nuclear, etc.
There are some nasty molecules involved in photovoltaics (as there are in the computer chips that make your smart phones and televisions, well, smart.) The industry (at least in the United States) is very careful about the proper disposal of these chemicals. (I won't get into rare earth metals here. We want quantum electronics for our convenience but we need rare earth metals to accomplish that. I don't know about you, but I don't like to be dependent on China so the trade-off is rare earth mining. More on that later.)
The technology that uses the least amount of water after wind turbines is photovoltaics. The best place to employ that technology is on your own home or business if you want to be part of a community that conserves water. Of course, at the present time, you don't use all of the electricity generated from your solar panels. Without batteries you have to sell that power back to the grid. The "grid" at least the El Paso Electric Company wants to increase substanially how much a solar user pays for a kWhr while buying back at $.03/kWhr. An Australian system uses the excess to heat water. If you own an electric car, you can recharge its batteries with your excess. Bottom line: getting off the grid (and thus the community's consumption of more scarce water) is the way to go.
More on passive solar next. - Jim Tolbert
For more information and references for above:
Water Use by Solar Projects Intensifies
Environmental Impacts of Solar Panels
How It Works: Water for Power Plant Cooling
Fact Check: How Much Water Does Solar Power Really Use?
Get more out of your solar power system by using water as a battery
Do wind turbines kill birds?
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