A novel concept to improve the flexibility of steam power plants using an electric feedwater heater

Abstract

The concepts of operational flexibility enhancement for steam turbine power plants described in the trade literature focus on thermal energy accumulation and utilization. In this paper a new concept of flexibility improvement is presented for steam turbine power plants, using an electric heater to preheat the feedwater for the boiler. The proposed method does not require extensive alterations in the power plant process systems, and no large thermal energy storage is necessary. It is important to note that this solution is only applicable if the boiler and its control system have the capability to work under this reduced load condition. By using electric feedwater heating it is possible to reduce the power transferred to the grid and keep the plant in operation at low loads. Thanks to the developed model of a 200 MW reference power plant using the Ebsilon Professional 15 software, the authors carried out simulation tests, based on which it has been proven that it is possible to reduce the minimum load for grid production from 92 MW to 78 MW. Although the efficiency of the electricity production decreased, the cost analysis has shown that the proposed modifications are reasonable, thanks to the improved cooperation of the 200 MW power plant with the grid. The NPV in the analysed system was PLN 35 million, and the sensitivity analysis showed that the profitability will increase with the increased number of necessary shutdowns of power plants without modifications. This is particularly important considering the development of renewable energy sources and the random and stochastic nature of their electricity generation.