Will Cutting Down Trees Alleviate Water Woes for Solar Thermal?

A solar power plant proposed in the arid desert near Bakersfield, California was almost abandoned last year due to concerns over water supply. It appears that an unconventional compromise has been reached: NextEra Energy, the company seeking to build the power plant, will cut down hundreds of thirsty nonnative trees in the area to offset the power plant’s water use.

Solar thermal power, also known as concentrating solar power or CSP, requires copious amounts of water to produce clean energy and the technology has raised fears about straining water supplies . To make matters worse, the regions best-suited for CSP tend to be arid and already burdened by over allocation of water resources. As an article in the LA Times points out:

Proposals to build dozens of solar farms on hundreds of thousands of acres in the desert Southwest have split the environmental movement and divided local communities. For solar developers and some green groups, the projects are desperately needed in the fight against climate change; others see them as a threat to unique and fragile ecosystems.

Water has become a particular flash point. Solar thermal power plants use mirrors to heat liquids to create steam that drives an electricity-generating turbine. The steam must be condensed and the hot water cooled for reuse. The cheapest and most efficient way to do that is wet cooling, which lets the heat evaporate but requires the constant replacement of water.
…
State policy prohibits the use of drinking water for power plant cooling, and local residents lined up at public hearings to express concern that the solar farm would drain their aquifer.

"Everybody else in the state of California is trying to conserve water and here all at once, boom, you guys are using it all up on us," said Ace Miller, an area resident, at one hearing.

With energy commission staffers and NextEra at loggerheads, executives warned last year that they might have to abandon the $1-billion project -- and the hundreds of construction jobs it would create -- because they claimed that Beacon wouldn't be sufficiently profitable unless they could use well water.

Developing clean energy is vital to combating climate change and the jobs that are created by these types of projects can help persuade even the staunchest global warming deniers to support clean energy projects. But when faced with the choice between water and clean energy, it is understandable that many people will choose water. Which is why the compromise between NextEra and the California Energy Commission is so important.

So what, exactly, does the compromise entail? Basically, NextEra is agreeing to use reclaimed wastewater for their cooling operations and will cut down water-hogging invasive tamarisk trees to offset the freshwater they use until enough reclaimed water becomes available. Again from the LA Times:

NextEra is now talking with two local municipalities, California City and Rosamond, about buying reclaimed water to cool the power plant. That would allow the company to sidestep a fight over water use while giving the cities a market for their treated wastewater.
…
The compromise offers other environmental benefits as well. Treated wastewater contains salt and nitrates, and by piping it to Beacon rather than returning it to the aquifer, the cities can improve the basin's water quality.

Since the solar farm will still draw freshwater until enough reclaimed water can be provided, NextEra proposed to remove thirsty tamarisk trees to help recharge the aquifer. A native of the Mediterranean, the tamarisk was brought to the American West in the 19th century for use as a windbreak. The developer of California City planted hundreds of the trees in the area, Bevins said.

An acre of tamarisks can consume 1 million gallons of water annually, said Tim Carlson, research and policy director for the Tamarisk Coalition, a Grand Junction, Colo., nonprofit group working to eradicate the trees.

Regulators welcomed NextEra's proposal to remove tamarisks, which have taken over 1 million acres in the West.

"If we could eliminate tamarisk from large areas of the West, it would have a benefit to wildlife, native vegetation and would reduce water usage," O'Brien said.

The first thing that California got right is a no-brainer: require energy companies to use reclaimed wastewater for power plant cooling. There is no reason to use highly treated municipal drinking water or precious 'virgin' freshwater for power plant cooling when many wastewater treatment plants across the country are struggling to find ways to discharge their treated sewage.

The more innovative approach – cutting down the nonnative, water-hogging tamarisk trees – is an idea that could spur similar compromises where water scarcity and energy development clash. If it is truly economically or technologically unfeasible to reduce water consumption through dry- or hybrid-cooling systems, and if a power plant has exhausted all available alternative sources of water, then figuring out ways to offset water use appears to be a good compromise.

Identifying and removing water-using invasive species, or funding water efficiency projects that offset comparable amounts of water could be a good way for energy companies to deal with their water woes. Of course, the water savings must be quantifiable and the water savings would need to be achieved in the same watershed as the power plant, in order to ensure that the affected area’s water balance remains unchanged.

Although not explicitly intended for power plants, the Bonneville Environmental Foundation has already created a paradigm for water offsets through their Water Restoration Certificates. Their water offset program appears promising and could be applied in conjunction with power plant construction to ease local concerns over water impacts. For more information, read my post on water restoration certificates.