Water wars threaten solar future

Published Date: 04 October 2009
By Todd Woody in Amargosa Valley, Nevada
IN A rural corner of Nevada reeling from the recession, a glimmer of salvation seemed to arrive last year. A German developer announced plans to build two big solar farms, creating hundreds of jobs.
But then things got messy. The company, Solar Millennium, revealed that its preferred method of cooling the power plants would consume 1.3 billion gallons of water a year, about 20 per cent of this desert valley's available water.Now Solar Millennium finds itself in the midst of a new-age version of a Western water war. Amargosa Valley's population is divided, pitting people who hope to make money selling water rights against those concerned about the project's impact on the community and the environment."I'm worried about my well and the wells of my neighbours," George Tucker, a retired chemical engineer, said.This is one of the inconvenient truths about renewable energy: sometimes it demands a huge amount of water. Certain types of solar farms, biofuel refineries and cleaner coal plants could consume billions of gallons every year. "When push comes to shove, water could become the real throttle on renewable energy," said Michael E Webber, an expert and the assistant professor at the University of Texas in Austin.Conflicts over water may shape the future of many energy technologies. The most water-efficient renewables are not necessarily the most economical, but water shortages could give them a competitive edge.In California, solar developers have already been forced to switch to less water-intensive technologies when local officials have refused to turn on the tap. Other big solar projects are mired in disputes with state regulators.To date, the flashpoint for such conflicts has been the South-west, where dozens of multi-billion-dollar solar power plants are planned for thousands of acres of desert. At public hearings fromNew Mexico to California local residents have sounded alarms over the impact that this industrialisation will have on wildlife, their desert solitude and, most of all, their water.Joni Eastley, chairwoman of the county commission in Nye County, Nevada, which includes Amargosa Valley, said at one hearing that her area had been "inundated" with requests from renewable energy developers that "far exceed the amount of available water".Many projects involve building solar thermal plants, which use cheaper technology than the solar panels often seen on roofs. In such plants, mirrors heat a liquid to create steam that drives an electricity-generating turbine. As in a fossil fuel power plant, that steam must be condensed back to water and cooled for reuse.The conventional method is called wet cooling. Hot water flows through a cooling tower where the excess heat evaporates along with some of the water, which must be replenished constantly. An alternative, dry cooling, uses fans and heat exchangers, much like a car's radiator. Far less water is consumed, but dry cooling adds costs and reduces efficiency – and profits.The efficiency problem is especially acute with the most proven technique, mirrors arrayed in long troughs. "Trough technology has been more financeable, but now trough presents a separate risk – water," said Nathaniel Bullard of New Energy Finance, a London research firm.That could provide opportunities for developers of photovoltaic power plants, which take the type of solar panels found on rooftops and mount them on the ground in huge arrays. They are typically more expensive and less efficient than solar thermal farms but require a relatively small amount of water, mainly to wash the panels.Water disputes forced Solar Millennium to abandon wet cooling for a proposed solar trough plant in California after the water district refused to supply the necessary 815 million gallons a year. The company subsequently proposed to dry cool two other massive California solar trough farms in the Mojave Desert. "We will not do any wet cooling in California," said Rainer Aringhoff, president of Solar Millennium's US operations. "There are simply no plants being permitted here with wet cooling."Even solar projects with low water consumption face hurdles. Tessera Solar is planning a large project in the Californian desert that would use only 12 million gallons annually, mostly to wash mirrors. But because it would draw upon a depleted aquifer, Tessera may have to buy rights to ten times that amount of water and then retire the pumping rights to the water it does not use. For a second big solar farm, Tessera has agreed to fund improvements to a local irrigation district in exchange for access to reclaimed water. "We have a challenge in finding water even though we're low water use," said Sean Gallagher, a Tessera executive. "It forces you to do some creative deals."In the Amargosa Valley, Solar Millennium may have to negotiate access to water with scores of individuals and companies. "There are a lot of people out here for whom their water rights are their life savings, their retirement," said Ed Goedhart, a local farmer and state legislator, as he drove past sun-beaten mobile homes and patches of irrigated alfalfa. Farmers will be growing less of the crop, he said, if they decide to sell their water rights to Solar Millennium. "We'll be growing megawatts instead of alfalfa," he said.