January 15, 2008

Costlier, scarcer supplies dictate making thermal plants less thirsty

By Dr. John R. Wolfe, PE, Limno-Tech Inc.

Running the numbers

Potential cost savings have been estimated above for several innovative applied technologies. To provide a consistent point of reference, Table 3 can be used to roughly estimate the potential annual cost savings available to a typical 350-MW coal-burning plant from capturing evaporation, reducing blowdown, using degraded waters, and adopting dry or hybrid cooling.

Table 3. Cost savings. These are the estimated annual benefits for a typical 350-MW coal-burning plant from using different water use reduction technologies. Source: EPRI, 2007
 

Any of the estimated savings shown in the table would be sizable enough to significantly increase a power plant’s profitability. For example, the production costs of a 350-MW baseload coal-burning plant run about $100 to $125 million annually, based on a levelized cost ranging from $33 to $41/MWh. With the exception of dry scrubbing, each technology listed in Table 3 has the potential to reduce annual production costs by about 1%, increasing profitability by the same percentage.

Because profit rates for generating plants currently average about 7% to 8% of costs, implementing these water-conservation technologies, alone or in combination, could raise profit rates by 1 to 3 percentage points, from 7% to 8% to an improved 8% to 11%. Measured in millions of dollars, that’s a substantial gain.

Water usage research

For more information about the subject of power plant water usage, consult the following sources, which informed the writing of this article:

• California Energy Commission. 2003. “U.S. Per Capita Energy Use by State in 2003.” www.energy.ca.gov/electricity/us_percapita_electricity_2003.html.
• DeFillippo, M. 2003. “Use of Degraded Water Sources as Cooling Water in Power Plants.” EPRI and California Energy Commission.
• Energy Information Administration. 2004. Annual Energy Review 2003.
• EPRI. 2002. “Water and Sustainability (Volume 1): Research Plan.”
• EPRI. 2004. “Comparison of Alternate Cooling Technologies for U.S. Power Plants: Economic, Environmental, and Other Tradeoffs.”
• EPRI. 2007. “Program on Technology Innovation: An Energy/Water Sustainability Research Program for the Electric Power Industry.” Prepared by Limno-Tech Inc.
• Metcalf & Eddy Inc. 1991. Wastewater Engineering, Disposal and Reuse, 3rd ed. New York: McGraw-Hill.
• Mortenson, Ken. 2006. “Use of Air2Air to Recover Fresh Water in Evaporative Cooling at Coal-Based Thermoelectric Power Plants.” Symposium on Western Fuels. Denver, Colo.
• National Energy Technology Laboratory. 2005. “Power Plant Water Usage and Loss Study.”
• National Energy Technology Laboratory. 2006.
• Estimating Freshwater Needs to Meet Future Thermoelectric Generation Requirements.
DOE/NETL–2006/1235.
• U.S. Geological Survey. 2004. Estimated Use of Water in the United States in 2000. USGS Circular 1268. http://pubs.usgs.gov/circ/2004/circ1268.

—This article was based on the Limno-Tech report, “Program on Technology Innovation: An Energy/Water Sustainability Research Program for the Electric Power Industry.” EPRI, Palo Alto, CA: 2007. 1015371.Dr. John R. Wolfe, PE (jwolfe@limno.com), was the principal investigator for Limno-Tech Inc. Paul L. Freedman, PE, and M. Catherine Whiting were coauthors of the report.