Welcome to the 100th Our Water Matters. As we learned in previous columns, the power of falling water is a central component of hydroelectricity generation. Water is also essential to thermal forms of electricity, known as thermoelectricity.
“In the United States, 90% of electricity comes from thermoelectric power plants—coal, nuclear, natural gas, and oil—that require cooling,” according to the Union of Concerned Scientists (UCS). “Thermoelectric power plants boil water to create steam, which then spins turbines to generate electricity … Once steam has passed through a turbine, it must be cooled back into water before it can be reused to produce more electricity.”
The three most common cooling methods for thermoelectricity plants include once-through systems, wet-circulating or closed-loop systems, and dry-cooling systems. The first two methods use water for cooling, while the third method uses air. Dry-cooled systems “can decrease total power plant water consumption by more than 90%,” explains the UCS in an article titled “How it Works: Water for Power Plant Cooling.” But “[t]he tradeoffs to these water savings are higher costs and lower efficiencies.”
Once-through systems “take water from nearby sources … circulate it through pipes to absorb heat from the steam in systems called condensers, and discharge the now warmer water to the local source,” writes the UCS. Although their simplicity and low cost initially made them the most widespread method for cooling thermoelectricity plants, once-through systems involve “draining huge volumes of water from our rivers, lakes, or oceans … then discharging it back from where it was taken but at much higher temperatures,” explains Parker Shabala in her article for Earthday.org titled “Powering the Future Without Draining the Planet.” This results in “thermal pollution, which disrupts aquatic ecosystems” due to “short-term effects” such as “heat shock to fish and other aquatic organisms, which can cause death or severe physiological stress.” Long-term effects include “biodiversity loss, harmful algal blooms, and altered reproductive cycles in marine life,” according to Parker.
Wet-recirculating or closed-loop systems “reuse cooling water in a second cycle rather than immediately discharging it back to the original water source,” according to the UCS. These systems most commonly “use cooling towers to expose water to ambient air. Some of the water evaporates; the rest is then sent back to the condenser in the power plant. Because wet-recirculating systems only withdraw water to replace any water that is lost through evaporation in the cooling tower, these systems have much lower water withdrawals than once-through systems, but tend to have appreciably higher water consumption,” writes the UCS.
In his book Thirst for Power: Energy, Water, and Human Survival, author Michael E. Webber argues that the power sector is “the single largest user of water in the United States.” He puts this into perspective by explaining that, “on average across the thermal power sector in the United States, about 15 gallons of water are withdrawn and just under 1 gallon consumed for every kilowatt-hour of electricity that is generated,” according to Webber. “Because typical homes in the United States use about 20 to 40 kilowatt-hours of electricity each day, approximately 300-600 gallons of cooling water are required to make electricity for those homes.” If we take into consideration that an average home uses about “150 gallons per day for washing, cooking, drinking, and watering lawns,” writes Webber, this “means we use two to four times more water at home for our lights and outlets than our faucets and showerheads.”
Webber also points out that the need for such large amounts of water “introduces vulnerabilities” for America’s power plants. Nowhere is this truer than in Texas, where much of the state’s electricity generation “relies on state water resources,” according to “Foundation for Economic Growth: Assessing Texas’ Water Infrastructure Needs” by chief author Jeremy Mazur of Texas 2036. “More critically, this generation is essential for meeting peak summertime loads.” Heavy dependence on water availability, especially during the hottest months, makes the state’s grid particularly susceptible to drought. To illustrate the point, Mazur recounts the events of 2023, when “Texas witnessed one of its hottest summers on record, precipitating record-breaking electricity demands as homes and businesses increased air conditioning use. In the meantime, severe drought conditions spread throughout the state … That August … more than 25% of the grid’s dispatchable electricity generation was at risk of having insufficient water supplies over the subsequent 18 months to sustain operations.” If the drought had continued into 2024 “as had happened during previous multi-year droughts, then a substantial portion of Texas’ dispatchable generating capacity needed for reliable electricity service would have been at risk of interruption.” Any interruption in electricity service can have devastating consequences for people and the economy. A recent study cited by Mazur suggests that “each 1,000 MW of generation capacity shortfall could trigger daily economic losses of more than $320 million.”
Texas voters recently authorized the state to allocate an additional one billion dollars annually to shore up these vulnerabilities. This is a good start. But we also need greater awareness of where our water and energy come from in the first place. Toward that end, Our Water Matters will continue educating readers about the complex interplay between water and energy in the firm belief that knowledge is also power.
Trey Gerfers serves as general manager of the Presidio County Underground Water Conservation District.