Power Plant Cooling and Associated Impacts
The Need to Modernize U.S. Power Plants and Protect Our Water Resources and Aquatic Ecosystems
- Water withdrawals for thermoelectric power generation were estimated in 2005 to be 201 billion gallons per day -- the highest use of any industry.
- The use of once-through cooling systems causes severe environmental impacts, killing billions of fish, degrading aquatic ecosystems, and increasing the temperature of our rivers, lakes, and ocean waters.
- Smarter energy choices exist to reduce the water impacts of power plant cooling, including the use of reclaimed water and investment in renewable energy and energy efficiency.
Water withdrawals for thermoelectric power generation were estimated in 2005 to be 201 billion gallons per day -- the highest use of any industry. Most of that water is used for cooling. Power plants boil water to produce steam, which is used to spin the turbines that generate electricity. Then, staggering volumes of water are withdrawn from nearby rivers, lakes, and oceans to cool the steam back into water so it can be used to produce more electricity. This entire cooling process can wreak havoc on aquatic ecosystems.
Once-Through Cooling Has Many Adverse Environmental Impacts
The three basic types of cooling systems -- once-through, closed-cycle, and dry cooling -- differ dramatically in their water usage, with once-through cooling being the most water-intensive and environmentally harmful method. A power plant with once-through cooling draws hundreds of millions -- and for some plants billions -- of gallons of water each day from nearby lakes, rivers, or ocean waters. Not only does the withdrawal of cooling water result in a number of adverse environmental impacts on aquatic life, but a reliance on the constant availability of such enormous quantities of cool water leaves plants vulnerable in times of drought and extreme heat.
Power Plants Kill Fish
As water is being drawn into a cooling system, full-grown fish and other aquatic life are smashed and trapped against screens at the opening of an intake structure. This is referred to as impingement. In addition, early-life-stage fish, eggs, and larvae are often sucked into the cooling system, where they are harmed by heat, pressure, mechanical stress, and/or chemicals used to clean the cooling system before being dumped back into a water body. This is referred to as entrainment.
Power Plant Water Use Heats Up Rivers and Lakes
Thermoelectric power plants are one of the main causes of thermal pollution, the degradation of water quality by any process that changes ambient water temperature. As water passes through a once-through cooling system, it gets warmer than the source water. Discharging that warmer water to a river or lake can stress and kill fish andnother wildlife.
Power Plants are Vulnerable in Times of Drought and Extreme Heat
The high water demands of power plants have adverse consequences not only to the environment but also to the power plants themselves. Power plants suffer from water temperature problems mainly during hot summers or heat waves, when the temperature of intake water is elevated at the same time that plants are running at full capacity to meet peak loads from air conditioning. When water is too warm for power plant cooling, it decreases power plants' efficiency, making them less competitive. Prolonged drought can drop water levels below a plant's intake pipes. When water is too warm for cooling or simply not available, facilities have to cut back power production or even shut down.
Climate Change Poses More Risks for Power Plants
Our nation's precious water resources will face even more stress as climate change is projected to make droughts in many regions more severe, thus affecting water availability, and heat waves more frequent, thus affecting water quality by driving up the temperature of lakes, streams, and rivers. These impacts of global warming will create an increased risk of shutdowns at thermoelectric power plants across the country as they are forced to deal with potentially even lower water levels and hotter cooling water. To further exacerbate the problem, our population -- and therefore our demand for energy -- continues to grow.
Closed-Cycle Cooling is the Best Technology Available
Section 316(b) of the Clean Water Act requires the U.S. Environmental Protection Agency (EPA) to adopt standards for cooling water intake structures based on the "best Technology available" (BTA) for minimizing adverse environmental impacts. Closed-cycle cooling is BTA for cooling water intake structures because it reduces intake flow to the greatest extent and thus is most effective at reducing fish kills. Use of closed-cycle cooling provides significant environmental benefits at minimal costs to both the electrical power industry and consumers. The EPA should therefore establish a national, uniform standard for impingement and entrainment mortality based on the performance of closed-cycle cooling systems.
Smarter Energy Choices Exist to Reduce the Water Impacts of Power Plant Cooling
Trends such as climate change and population growth do not have to continue intensifying water/energy conflicts throughout the nation. By installing better cooling systems, relying more heavily on renewable energy such as wind and solar power, and expanding energy-efficiency efforts, the enormous water use by thermoelectric power plants can be dramatically reduced. Such strategies can help ensure a sustainable energy and water future.
- Improve Data and Information on Power Plant Water Use
In order to make water-smart energy choices, obtaining reliable information about this issue is essential. State and federal agencies must work to ensure that power plant operators report their water use both accurately and consistently.
- Promote Renewable Energy and Invest in Energy Efficiency
Significant water savings and associated environmental benefits can be achieved by shifting to renewable energy and expanding energy efficiency efforts. Replacing conventional fossil fuels with less water-intensive renewable energy sources, such as wind and solar power, will significantly reduce the pressures placed on our nation's water resources by power plants and better protect aquatic ecosystems.
- Set Stringent Cooling Technology Requirements
By requiring existing power plants to install closed-cycle cooling rather than allowing them to continue using the antiquated once-through cooling system, power plants can reduce their withdrawals by approximately 95 percent. This, in turn, could lead to at least a 95 percent reduction in the destruction of aquatic life caused by cooling water intake structures.
- Use Reclaimed Water for Cooling
While the use of closed-cycle or dry cooling systems can help reduce a power plant's freshwater demands, an additional strategy is to use treated municipal wastewater, or reclaimed water, for cooling. Reclaimed water represents a valuable, and readily available, alternative water source that can not only help reduce pressure on our nation's limited freshwater resources -- and thereby reduce associated environmental impacts -- but also help power plants become less vulnerable in times of water constraints.
The EPA is in the process of issuing standards for the use of cooling water at existing U.S. power plants. A clear, consistent national policy is needed to ensure that the U.S. electricity sector is moving toward a cleaner and more water-smart future by replacing antiquated and environmentally destructive once-through cooling systems with modern, less water-intensive technologies.
last revised 5/15/2014