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.
At least four nuclear plants had to shut down in July for these reasons. 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.
While it's likely that these other types of power plants are suffering too, Tyson Brown of the Energy Information Administration says it is impossible to know yet how the drought has affected them. Nuclear plants are required to report when they shut down and why, but other power plants are not.
Bio fuel thirst
Reports of how much energy the US has generated this summer won't be released for some months, he says. The North American Energy Reliability Corporation's most recent report (PDF) calls the drought outlook "not optimistic" for energy, but says that most of the US should be able to meet its energy demands this year. The exception is Texas, where resources are expected to be tight.
Utility-scale power isn't the only energy source being hurt by the drought, however. With corn harvests expected to be as low as 75 per cent of normal yields, biofuel production is also suffering. Compared to other energy sources, biofuel production requires the most water.
Arjen Hoekstra of the University of Twente in the Netherlands calculates the total water use of different industries ? including not just cooling but every step in the supply chain as well. According to his "water footprint calculator", biofuels require orders of magnitude more water than any other energy source.
The good news is that one energy industry isn't using as much water as commonly perceived. Fracking involves injecting water, sand and chemicals into shale deposits in order to release the gas they hold. Farmers tend to worry about the amount of water used for fracking, but that amount is minimal ? equivalent to what a golf course uses in a month, says David Burnett of Texas A&M University in Galveston.
However, rerouting water can still affect agriculture locally, so Burnett and others are developing ways to recycle fracking water or use brackish or salt water in place of fresh water. In the meantime, some oil and gas companies say they are having trouble acquiring water, as worried farmers are charging them more money for water rights.
Even if the US escapes this summer without major blackouts, however, the energy infrastructure has a lot of work to do to prepare for more frequent droughts in the future. "In a warmer climate, you don't have to drop as far below normal to trigger a drought," says Texas' state climatologist John Nielsen-Gammon. Hotter air allows more water to evaporate and forces power plants to work harder.
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