Energy’s Water Footprint
You may not realize it, but when you use energy, you’re also using water indirectly—lots of it! For example, most electricity used in the United States is generated by thermoelectric power plants – fossil-fueled or nuclear-fueled facilities that use steam to turn turbines and generate electricity. Many thermoelectric power plants rely on outdated “once-through” cooling technology in which intake pipes withdraw millions of gallons of water daily. In all, thermoelectric power plants account for an astonishing 49 percent of total water withdrawals in the United States, including water withdrawn from freshwater sources such as lakes, and saline water sources, such as estuaries.
Once-Through Cooling: Once-through cooling is a process that pulls in cold river, lake and coastal water to cool power plant machinery and then releases the heated water back into the environment.
Closed-Cycle Cooling: In a closed-cycle wet cooling system, cooling water is circulated first through the plant to absorb heat, then through the cooling towers to evaporate heat to the atmosphere and condense steam back to liquid to be recirculated through the plant. A closed-cycle dry cooling system uses radiator-type coils to transfer heat to air passing over the coils.
Power plants outfitted with once-through cooling systems account for approximately 90 percent of water withdrawals for thermoelectric power. Plants equipped with “closed-cycle” cooling systems make up the remainder. Once-through cooling system withdrawals have a devastating impact on aquatic ecosystems, because as they withdraw water they also draw in fish and other aquatic life, injuring or killing them in the process. In addition, when the cooling water is returned to its source it is 12 to 30 degrees Fahrenheit warmer than when it was withdrawn, further damaging aquatic life through “thermal pollution.”
There are many energy options available today, both large- and small-scale, that require significantly less water than thermoelectric power plants. Switching to clean and sustainable energy sources like wind and solar power is an important step towards reducing our energy-related water use.
Gasoline and oil consumption are also closely tied to water use, because oil refining requires large quantities of water. For instance, it is estimated that the United States withdraws 1 to 2 billion gallons of water to refine nearly 800 million gallons of petroleum products every day.
Corn-based ethanol, which the United States touts as an eco-friendly alternative fuel, places an even higher demand on water supplies than gasoline. A recent study found that as corn-based ethanol production doubled between 2005 and 2008, related water use more than tripled. On average, it takes 3.5 to 6 gallons of water to produce one gallon of ethanol. This water is generally drawn from Midwestern water supplies that are already under stress due to agriculture and drought. For example, Iowa’s ethanol plants each use about 400 million gallons of water a year – roughly the same amount of water used each year by a town of 10,000 people.
Two programs that can help you save water, energy and money:
Energy Star and WaterSense.
Switching to clean and sustainable energy sources like wind and solar power is an important step towards reducing our energy-related water use. Also important is using less energy. This means switching to energy-efficient appliances and light bulbs, turning off electronics when they’re not being used, carpooling, and using public transportation as much as possible. Water-efficient appliances also play a critical role: conserving water saves energy which further reduces the strain on water resources and, of course, helps in the fight to clean our air and slow climate change.
To learn more about the connection between energy and water, visit the Network for New Energy Choices.
