On the face of it large-scale solar farms are a get-out-of-jail-free card for a society hooked on ever increasing doses of energy. They apparently generate clean power from thin air. Visual pollution aside, they seem to have no negatives.
But the best sites for solar farms are the sunniest places. And the sunniest places tend to be the driest places. And therein lies a major headache for dozens of giant solar developments. It turns out that even a medium sized solar farm uses millions of gallons of water a year for cleaning and cooling. Solar industry v communities This has brought the solar power industry into direct conflict with local communities concerned that there may not be enough water for everyone else once the solar farms farms have had filled their canteens.
It has got to the point that water has become the limiting factor on the development of large-scale solar power says one expert. “When push comes to shove, water could become the real throttle on renewable energy,” said Michael E. Webber, an assistant professor at the University of Texas in Austin who studies the relationship between energy and water.
The problem is most acute in the sunny south western states. In California for instance there are plans for 35 large solar projects worth billions of dollars which could generate 12,000 megawatts of electricity, equal to the output of about 10 nuclear power plants.
Solar Millennium Water disputes have already forced an Israeli company called Solar Millennium to abandon a proposed solar power plant in Ridgecrest, California, after the water district refused to supply the 815 million gallons of water a year the project would need.
But at public hearings all over the south west local residents have expressed deep concern over the impact that these solar power stations will have on wildlife, their desert solitude and, most of all, their water.
Joni Eastley, chairwoman of the county commission in Nye County, Nevada., said at one hearing that her area had been “inundated” with requests from renewable energy developers that “far exceed the amount of available water.”
Solar Millennium has announced plans for two more solar farms in the area. Local people welcomed the hundreds of jobs they would create. But when the company revealed that cooling the plants would consume 1.3 billion gallons of water a year, -about 20 percent of this desert valley’s available water,- local farmers began to have their doubts. “I’m worried about my well and the wells of my neighbours,” said retired chemical engineer George Tucker. Off-grid asked the company for a comment but it has so far declined to put its side of the argument.
The problems are most acute in solar thermal plants which use mirrors to heat water, creating steam that drives a turbine. That water is then cooled for reuse in cooling towers.
There is an alternative method called ‘dry cooling’ which uses fans and heat exchangers. It consumers far less water, but it costs more and is less efficient.
However even that method is prodigious in its water consumption. BrightSource Energy had a proposal for a dry-cooled solar farm in Ivanpah Southern California. that would consume an estimated 25 million gallons a year, just to wash the mirrors.
Off-grid alternative experts say that water wars can only benefit from a less centralised, more off-grid approach to renewable energy generation. Although smaller installations are less efficient than large arrays, they are less disruptive generally and require less water.
Interesting, I had not thought about the water use associated with solar power. For many years I have worked on water supply, flood control and distribution systems. More recently I have focused on minimizing resource use through better planning, design and project management.
I imagine that the cheapest way of cleaning the solar mirrors and panels has been with water. They will need to develop surface coatings that allow the mirrors and panels to stay cleaner and allow cleaning with less water.