Specific Connection in Energy-Water Nexus

The generation of electricity uses water to turn turbines for hydropower or produce steam for thermoelectric power; it also uses cooling water to condense the steam produced by thermoelectric generation. Thermoelectric power can utilize either once-through or closed-loop systems. In a once-through system, most of the water used to cool the power-producing equipment may be returned to its source or released to the atmosphere. Before the used water is released back into a body of water, it may need to be cooled to prevent its acquired heat from changing the ecosystems of the streams and lakes to which it is returned. Although closed-loop systems reuse water, additional water is required to replenish evaporation losses, blowdown, drift, and leakage.

A shortage of water directly challenges the capability to produce power. In the summer of 2001, droughts drained hydroelectric power resources for the Pacific Northwest and Northern California. In Idaho, energy needs were pitted against the needs of endangered fish, as officials debated the timing of reservoir releases. Drought has forced the seven states that depend on the Colorado River system to contemplate sharing potential shortages as well as water.

Resource Quantities

Thermoelectric power production accounts for 48 percent of total water withdrawals, 39 percent of freshwater withdrawals and 3 percent of freshwater consumption in the United States, according to the U.S. Geological Survey.

Power plants that utilize once-through cooling water systems withdraw between 80 and 98 percent more water than those that have recirculating systems. [www.epa.gov/ostwater/316b/support/chapter3.pdf]
Recirculating systems increase water consumption relative to once-through systems.

The National Energy Technology Laboratory produced a report estimating future national water withdrawal and consumption for US power plants. http://www.netl.doe.gov/publications/press/2006/06073-Water_Needs_Analys...
 

Sector Challenges and WETT Solutions

The challenges surrounding water and energy consumption in the production of energy include developing and proving new technologies that will:

• Reduce the energy sector’s need for fresh water, including higher thermal efficiency
• Improve methods for predicting water-related impacts from climate change/variability
• Increase the use of impaired waters for cooling and process requirements
• Decrease the energy required for water treatment
• Remedy situations in which water supply limits energy production

The Water and Energy Technology Team (WETT) at Lawrence Berkeley National Laboratory (LBNL) is participating in the U.S. Department of Energy's Energy Water Roadmap, including three regional workshops (www.sandia.gov/energy-water). LBNL’s role, in partnership with the Utton Center at University of New Mexico is to provide assistance in identifying and analyzing policy, regulatory and economic issues. The EWN report to Congress can be accessed from this URL: http://www.sandia.gov/energy-water/congress_report.htm