The interdependence of water and energy
Have you ever thought that by leaving a light on, you’re wasting water, or that a leaky faucet wastes energy? It’s odd, but accurate.
That’s because water and energy are interrelated. Water is used in all phases of energy production, and energy is required to extract, pump, and move water for human consumption. Energy is also needed to treat wastewater so it can be safely returned to the environment.
C2ES recently hosted a series of webinars (video and slides here) on the intersection between water and energy (sometimes referred to as the “nexus”). The series was co-sponsored by the Association of Metropolitan Water Agencies and the Water Information Sharing and Analysis Center. Participants discussed how the water and energy sectors depend on each other and how they can work together to conserve resources.
How much energy does it take to provide people with safe drinking water and safely treat wastewater? Kristen Averyt, director of the University of Colorado’s Western Water Assessment, says the water sector uses about 13 percent of the nation’s electricity. In some areas, like the Mountain West and Southwest, it’s even higher.
In California, the East Bay Municipal Utility District reports that water-related energy use consumes 19 percent of the state’s electricity – enough to power 4.8 million homes. It also accounts for 30 percent of the state’s natural gas use, and consumption of 88 million gallons of diesel fuel.
On the other side of the equation, large amounts of water are needed to produce electricity. Averyt says a nuclear power plant with a once-through cooling cycle can withdraw up to 60,000 gallons of water from its cooling water source for every megawatt hour, the amount of electricity used by about 330 homes for one hour. A coal-fired power plant with a cooling pond consumes about 35,000 gallons per megawatt hour.
The production of natural gas, an important fuel for generating electricity, also requires a lot of water. According to the U.S. Department of Energy’s report The Water-Energy Nexus: Challenges and Opportunities, it takes 2 million to 9 million gallons of water to fracture one horizontal well in a shale formation.
So what are energy producers and water utilities doing to conserve?
In some cases, they’re forming partnerships to save resources. The Orange Water and Sewer Authority in North Carolina is working with Duke Energy to review use, rates, and service contracts. Together, they have saved money on energy use by a wastewater treatment plant and on standby power generation.
In San Antonio, Texas, CPS Energy and the San Antonio Water System, which are both city-owned but independently managed, are also working together. Each utility is largest customer of the other. Since the 1960s, they have cooled the city’s power plants using wastewater, rather than drinking water. CPS Energy’s Doris Cooksey says as a result, the city has had enough water for power generation even in times of drought.
Other companies are also taking steps to cut water and energy use. American Water, which provides drinking water and wastewater treatment to about 14 million people in 30 states and parts of Canada, is cutting its energy use by replacing aging motors and pipes. The company is also installing solar panels, which likely use less water to generate electricity. American Water’s Suzanne Chiavari says the solar applications produce about 3.7 million kilowatt hours per year, avoiding 2,500 metric tons of carbon dioxide emissions annually in the process.
Learning about the relationship between energy and water helps us to understand how our own daily activities affect these important resources. By using water wisely, we can save energy – and vice versa.