Thermochemical Energy Storage for Increasing the Flexibility of an Industrial Combined Heat and Power Plant

Most industrial combined heat and power plants (CHP) are primarily designed and operated to supply steam, accompanied by secondary electricity production. This constricts the CHPs to adjust their electricity production to the electricity price and therefore to operate efficiently and economically. Integrating a thermochemical energy storage (TCES) system into an industrial CHP allows the decoupling of power and heat supply and hence to increase flexibility while reducing expenses and CO2 emissions. A TCES based on the reversible reaction of CaO/Ca(OH)2 with steam, using two fluidized bed reactors and two bulk silos is currently developed at TUM. The TCES is charged by electrical heating inside the fluidized bed reactor and discharges high-pressure process steam at approx. 500 °C, using the heat of the endothermic reaction via built-in heat exchanger tubes. This paper assesses the benefits of integrating a TCES into an industrial CHP located in Germany with energy system optimizations using mixed integer linear programming and the software TOP-Energy. The simulations are based on energy prices of the year 2019 and plausible steam demands and are evaluated with a sensitivity analysis. Prognoses of energy prices and CO2 emission factors in 2030 and 2040 indicate that the TCES will be economically profitable and reduces the CO2 emissions of the considered energy system.