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There ain’t no free lunch

It is imperative for the health of the planet that we move away from extractive, carbon-based energy and toward more environmentally friendly alternatives. However, an article in the New York Times this morning reminds us that there are always going to be consequences to the planet no matter how we get our electrical power. Two proposed solar energy projects in California would consume more than a billion gallons of water a year while a total of 35 big solar farms have been proposed for arid parts of California alone.

In a rural valley of Nevada, a German developer announced plans last year to build two large solar farms to generate electricity for the California market. It sounded like a good idea to drought-parched Nevadans. The development would bring hundreds of new jobs and economic development to an area hard hit by the recession. Then they found out the cost. The plants would use over a billion gallons of the valley’s water, more than 20 percent of the available supply.

“I’m worried about my well and the wells of my neighbors,” George Tucker, a retired chemical engineer, said on a blazing afternoon.

Solar power will of course be one of the solutions as we move away from burning carbon fuels. But, “clean energy” does not come free. In a 2006 Sandia Labs report for the government they noted that coal-fired power plants use 100 to 300 gallons of water to produce one megawatt hour of electricity. A nuclear power plant uses between 500 and 1100 gallons of water for cooling for each MWh and a wet-cooled solar parabolic trough plant uses between 760 and 920 gallons per MWh for cooling. The rub, of course, is that solar power is most often generated in the hottest, most arid parts of the country, where water is often in short supply. Water supply for solar plants has often come at the expense of agricultural interests. BLM reports that they have received 130 applications for large-scale solar plants on over 1 million acres of public land. The proposed plants could produce enough electricity to power 20 million homes.

With all our technological progress in the last century, our means of producing electricity still relies almost entirely on steam power. Water is heated to produce steam to drive turbines. The steam can be created by burning coal, oil or gas, or using nuclear fission or, in the case of solar plants, by focusing large mirrors on a bucket of water. Once the steam and electricity has been produced, there is a need to cool the steam/water back down for re-use. Currently the means of doing that is to use large cooling towers and millions of  gallons of cooling water. Estimates are that “consumption of water for electrical energy production could more than double by 2030 from 3.3 billion gallons per day in 1995 to 7.3 billion gallons per day“. “Unfortunately, freshwater withdrawals already exceed precipitation in many areas across the country…

One solution to the excessive water use is the use of “dry cooling” for solar plants. Dry cooling is done by essentially building super-large radiator and fan systems to cool the steam water. But, dry cooling is expensive and reduces plant efficiency by as much as 10%. Dry cooling can only reduce water temperatures down to the ambient air temperature as opposed to the dew point temperature of water cooling. As cooling temperature increases, plant efficiency declines and, as mentioned before, it’s nearly always very hot in areas where we produce solar power.

It’s not as if we have to sacrifice our water to have electricity, but we need to be reminded that whatever we do, we will have impacts on the planet. Earlier this month, the Bugle posted an article on the price we pay in clean water to have cleaner coal power. Also, mining coal consumes 2.6 million gallons of water per day. Carbon-based power plants withdraw 136 billion gallons of water per day in our country and consume more than 3 billion gallons. Biofuel production is very water-intensive due mainly to the use of corn and soy products grown on irrigated lands. Alternative fuels such as methane or synfuels from coal are three times more water-intensive than traditional fossil fuels. Even the much needed improvements in our transmission system will require a sacrifice of our land and water.

We just need to keep in mind as we move forward that coal is not necessary to sustain life, but water is. Trade offs will have to be made. As they often say of fossil fuels, “They ain’t making any new water“.


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