Thermosyphon Cooler Hybrid System for Water Saving Power Plant Heat Rejection

Abstract

As noted in a Summer 2007 EPRI Journal article entitled Running Dry At The Power Plant, “Securing sufficient supplies of fresh water for societal, industrial, and agricultural uses while protecting the natural environment is becoming increasingly difficult in many parts of the United States. Climate variability and change may exacerbate the situation through hotter weather and disrupted precipitation patterns that promote regional drought.” Currently, in the United States, thermoelectric power production accounts for approximately 39% of freshwater withdrawals and 3% of overall fresh water consumption. The Electric Power Research Institute, EPRI, as part of its Technology Innovation (TI) program, is collaborating with Johnson Controls to conduct a feasibility study comparing the performance of a water saving Thermosyphon Cooler Hybrid System (TCHS) with other heat rejection systems for power plant applications. The TCHS employs a sensible heat rejection device, a thermosyphon cooler (TSC) in conjunction with an evaporative heat rejection device, an open cooling tower, to satisfy the annual cooling requirements of a given power plant. By reducing the evaporative heat load, the TCHS can significantly reduce the annual water consumed for cooling while still maintaining peak power plant output on the hottest summer days. Operational details of the Thermosyphon Cooler Hybrid System are presented. Additionally an overview of the cooling system simulation program, based on an 8,760 hourly analysis, used in the feasibility study is discussed. Results comparing the water use and additional fan power requirements between power plants employing a traditional all evaporative system and the TCHS are discussed for two different climatic locations. The concept of incorporating the cost of water, cost of power, the current plant operating conditions, and the current ambient dry bulb temperature into the TSC fan control strategy are also explored. The simulation program performance model is currently being validated with testing of a 1MW prototype TCHS at the Water Research Center near Cartersville, GA. Finally, a conceptual design for a power plant scale TCHS is presented.