New Scientist 
August 19, 2012
As the United States’ extended heat wave and drought threaten to raise global food prices, energy production is also feeling the pressure. Across the nation, power plants are becoming overheated and shutting down or running at lower capacity; drilling operations struggle to get the water they need, and crops that would become biofuel are withering.
While analysts say the US should survive this year without major blackouts, more frequent droughts and increased population size will continue to strain power generation in the future.
Power plants are a hidden casualty of droughts, says Barbara Carney of the National Energy Technology Laboratory (NETL) in Morgantown, West Virginia, because they are completely dependent on water for cooling and make up about half the water usage in the US. That makes them vulnerable in a heat wave. If water levels in the rivers that cool them drop too low, the power plant – already overworked from the heat – won’t be able to draw in enough water. In addition, if the cooling water discharged from a plant raises already-hot river temperatures above certain thresholds, environmental regulations require the plant to shut down.
One nuclear plant in Connecticut recently had to shut down because the sea water used for cooling was too warm. Nationwide, nuclear generation is at its lowest in a decade, with the plants operating at only 93 per cent of capacity.
Nuclear is the thirstiest power source. According to NETL, the average nuclear plant that generates 12.2 million megawatt hours of electricity requires far more water to cool its turbines than other power plants. Nuclear plants need 2725 litres of water per megawatt hour for cooling. Coal or natural gas plants need, on average, only 1890 and 719 litres respectively to produce the same amount of energy.