Electric Power Plant Waste Heat Utilization

An inevitable consequence of the second law of thermodynamics is that any electric power plant that operating on the closed Rankine cycle must reject approximately 60% to 70% of the heat that is added to the cycle through the condenser to the ambient environment in order to complete the cycle. The temperature of the waste heat exiting power plants, while too low for electric power generation, is often suitable for other purposes such as heating greenhouses and aquaculture facilities, particularly those that reject this waste heat directly to the atmosphere via cooling towers.Few facilities currently exist that utilize waste heat from power plants on a relatively large scale. The challenges are institutional and economic, not technical. Most electric utilities see little benefit to themselves in waste heat utilization. The cost of delivering hot water to the waste heat user can be significant compared to the benefit to the end user. However, this paper presents a new concept for utilizing waste heat that significantly reduces the cost of delivering waste heat by an amalgamation of users and provides a significant benefit to the power plant by reducing the heat sink temperature, thus increasing the efficiency of the turbine cycle and increasing the electrical output.A dedicated piping system was provided in the original design of the Tennessee Valley Authority’s (TVA) Watts Bar Nuclear Plant (WBNP) to utilize the turbine cycle waste heat and a portion of the nuclear plant reservation was dedicated for that purpose. However, when Unit 2 of the plant was not completed as scheduled, plans for the waste heat energy park (WHEP) were shelved in the early 1980’s. As this author supervised the engineering of that project, it will be used in the proposed paper to illustrate how the new concept may be applied.Copyright © 2012 by ASME