Most of that is frozen in glaciers—which means only 0.8 percent of the planet’s water reserves can be tapped for human use. Water is a precious, but limited, commodity. And nearly 1 billion people worldwide lack access to clean water.
In the U.S., 45.3 percent of the water withdrawn from lakes, rivers and underground aquifers is used to cool off thermoelectric power plants: nuclear reactors and plants that burn fossil fuels.
This is more water than used nationwide for irrigation, and it far exceeds any other source of demand, including public consumption.
To provide electricity for an average home, a nuclear power plant requires 615 gallons of cooling water a day, a coal-fired plant requires 199 gallons per day, and a natural gas power plant requires 114 gallons per day. The stunning volume is a quiet thief that threatens the U.S. water supply.
But to make sure we are comparing apples to apples, let’s look at how much water each power source withdraws to generate one megawatt-hour of electricity.
Nuclear reactors are the highest, at 13,000 gallons. Then comes concentrated solar (heating a fluid with the sun), coal, natural gas and biomass such as wood. The water needed by solar panels and wind turbines is orders of magnitude lower. Note that these data only reflect operations to generate electricity; they do not include water used to obtain the fuel or generate the power, which can be substantial. For example, fracking can use hundreds of thousands of gallons each time a rock deposit is cracked to release natural gas.
A portion of the water extracted is lost to evaporation. The rest is sent back to the environment, but some of that is contaminated with chemicals, and most of it is hot, which can kill fish and plankton and stress the ecosystem.
Making matters worse, the power sources that have high water withdrawal per MWh are also the largest suppliers of electricity.
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19 December 2018
20 December 2018