Technical and Economic Evaluation on the Integrated Heating System With Coupled Heat Pump and Backpressure Turbine

Abstract

The increasing depletion of fossil energy and the gradual aggravation of environmental pollution have increased the necessity of renewable energy applications. However, the intermittent characteristics of renewable energy power generation need to increase the flexibility of the original coal-fired power unit for balancing the supply and demand of the power system. In this work, two 350 MWe condensing units (CUs) were taken as examples and the thermodynamic simulation models were built by the ebsilon software to evaluate their technical and economic characteristics. At the same time, the system is coupled with heat pump (HP) and backpressure turbine (BT) for heating. Among them, the rated steam intake of HP is 194.9 t/h, and the rated steam intake of BT is 214.5 t/h. Results show that under the same requirements, the energy consumption with the backpressure turbine priority principle (BTtlp principle) is smaller than that with the heat pump priority principle (HPtlp principle). However, under the same thermal load conditions, the electrical load with the HPtlp principle can drop lower than that with the BTtlp principle. Meanwhile, there is an optimization interval for the output distribution of HP and BT. From the energy current diagram, it can be found that under the design main steam and given thermal load condition, the power generation efficiency of coupled mode is 0.74% more than that of HP mode and is 1.93% more than that of direct mode, while under the given thermal and electrical load condition, the system’s boiler output with direct mode is 3.37% more than that with HP mode and is 5.34% more than that with coupled mode. This provides a theoretical basis for the subsequent comprehensive evaluation of heating reformation.