Publication Date
4-7-2007
Abstract
Here we analyze the water use rates for thermoelectric power generation with respect to cooling system, plant type, plant age, geographic location and its relation to regional drought conditions between 2001-2005. Open loop plants withdraw roughly two orders of magnitude more water than closed loop plants, while consuming (i.e., lose water to evaporation) about the same amount. A high degree of variability for water withdrawal and consumption rates exists for low capacity facilities. The highest withdrawal rates are in the southeastern part of the United States. Power to Water supply curves show that power generation limits exist for the various cooling types (i.e. at some point, a large increase in water withdrawal corresponds to only a small increase in power generation). Water supply curves also show the degree to which total power generation might decline if water withdrawal rates had to be reduced due to prolonged and severe drought. Facilities having the highest withdrawal rates are the most susceptible to prolonged and severe drought. The point at which power generation begins to be significantly affected by drought depends upon cooling type (e.g. open freshwater, closed tower with forced draft). For example, if each plant that uses a closed loop, forced draft cooling system were limited to a water withdrawal rate of 100 cubic feet per second, total power generation for that category would only be reduced about 8 gigawatts. This means that if the maximum allowable withdrawal rate were reduced by 50 percent from 200 cubic feet per second, the total power generation would only be reduced 10 percent. The plants that are most susceptible to prolonged and severe drought are Southeastern, 20- to 70-year-old coal and coke plants, which use freshwater, open loop cooling systems. These same facilities are responsible for generating the greatest amount of electricity in the US.