More Efficient for Generating Electricity

Clean energy

Increasingly frequent heat waves and droughts tied to climate change are hurting the electricity sector.  According to the NY Times Green Energy Blog, “as temperatures rise and the climate gets warmer, so do the rivers and lakes that power plants draw their cooling water from. And that is going to make it harder to generate electricity in decades to come, (when) the water will be too warm to allow full power production.”

Increased drought conditions from hot weather reduce river and lake water availability, further reducing water supplies and reducing Coal-fueled and combined cycle power generation.

Power plants that burn coal or use nuclear fission, and most of the plants that burn natural gas with a combined heat-recovery system, use their heat to boil water into steam, which spins a turbine that turns a generator to make electricity. Then the steam has to be cooled and condensed back to water before being reheated again.

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If the river or lake water used to cool and condense steam is getting warmer, then the amount of steam it can condense is reduced, leading to a decline in electric power output, especially during the summer when electric fan and air-conditioning power demand is high

Electricity production by coal, nuclear and natural gas power plants is the fastest-growing use of freshwater in the U.S., accounting for more than about ½ of all fresh, surface water withdrawals from rivers.

In 2012, some U.S. power plants had to cut electricity production because of low water levels or because water was too warm to cool nuclear reactors. The National Oceanic and Atmospheric Administration said the period from August 2011 through July 2012 was the hottest 12-month period on record in the U.S. since 1895.

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In addition to fouling streams and drinking-water through mining and coal-ash dump sites, coal-fired power also relies heavily on closed-loop cooling systems, withdrawing 500-600 gallons of water per MWh. Most of this is then lost via evaporation.

Withdrawals for open-looped cooled coal-fired power plants are between 20,000-50,000 gallons per MWh.  While most of the water is returned, it’s at a higher temperature and lower quality.

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