(29a) Economic Evaluation of Freshwater Conservation Strategies for Thermoelectric Power Plants

Thermoelectric power plants withdraw and consume large volumes of freshwater.  In parts of the country where freshwater resources are scarce, this demand can be problematic.  One option for conserving freshwater is to utilize degraded water sources as a replacement cooling medium for thermoelectric power plants.  However, utilizing degraded water in cooling systems can be problematic; increased concentrations of particulates and salt forming species can lead to increased fouling on heat exchanger surfaces.  A degradation of performance in the heat exchanger will translate to a loss of thermal efficiency and may require the plant to perform more frequent maintenance routines; it is therefore necessary to treat the degraded water source before introducing it to the system. 

This presentation discusses a comprehensive methodology for the determination of the total cost of degraded water use in thermoelectric plants, including the cost of treatment, additional fuel use, additional downtime and lost power production that results.  This methodology is then applied via a novel, cross-disciplinary case study to (1) estimate the freshwater conservation cost associated with secondary municipal wastewater use in the recirculating cooling loop of a thermoelectric power plant; (2) evaluate the freshwater conservation cost associated with secondary municipal wastewater against that of dry-air cooling technology and the U.S. Department of Energy’s 2020 target; and (3) to determine the breakeven differential purchase price of freshwater to secondary municipal wastewater, beyond which the use of secondary municipal wastewater is economically beneficial.