Thermo-economic comparison of heat–power decoupling technologies for combined heat and power plants when participating in a power-balancing service in an energy hub

Abstract

Heat–power decoupling (HPD) technologies, which are integrated within combined heat and power (CHP) plants and can enhance the supply-side flexibility of CHP plants, have gained increased attention worldwide in recent years. This study focuses on analyzing and evaluating the effectiveness of existing HPD technologies for CHP plants in consideration of energy consumption characteristics, capital cost, and renewable power accommodation. Three categories of HPD technologies are evaluated, which are thermal energy storage, power-to-heat, and steam turbine renovation (STR). Thermo-economic models of HPD technologies and CHP plants are developed, and new performance indicators, including peaking energy saving ratio, peaking cost ratio, and minimum profitable subsidy power price, are defined. With a coal-fired CHP plant as the reference case, HPD technologies are evaluated quantitatively. Results show that the energy saving rates of HPD technologies accommodating the same amount of renewable power differ obviously, which should be considered in the design and development of HPD technologies. The economic performance of HPD technologies is mainly determined by the cost of decreased power sale and the expenditure reduction because of decreased fuel consumption. The minimum profitable subsidy power prices for thermal energy storage tank, electric boiler, heat pump, and STR are 12.7, 13.6, 11.7, and 42.0 USD⋅MWh−1, respectively. Moreover, sensitivity analysis of main parameters to the thermo-economic performance of HPD technologies is performed. The results of this study can guide the design, operation, and technological enhancement of HPD technologies.