A new dynamic control strategy for a solar-driven absorption thermal energy storage system: Modeling and performance evaluation

Abstract

Solar heating is a vital technology to promote the decarbonization of building energy supply systems. However, the mismatch between the intermittency of solar energy supply and the fluctuating heating demands poses significant challenges to its application. Current heat storage systems often exhibit low energy density, significant heat losses, and limited temperature regulation capabilities, which restrict their effectiveness in practical applications. This paper proposed a new real-time control strategy for a solar-driven absorption thermal energy storage system, integrated with an absorption heat pump, which can resolve the mutual constraints between solar energy utilization efficiency and the heating temperature, and then improve the system flexibility. The dynamic control strategy is implemented to manage concentration and temperature by regulating the inlet and outlet flow rates of three tanks, namely the absorbate tank, the weak solution tank, and the strong solution tank. A thermodynamic model is developed based on Aspen Plus and Matlab. Results show that within a 24-hour cycle, the system, driven by intermittent solar energy, can effectively meet the varying user-side heating demands through flow rate regulation. An optimized tank design, based on flow variation analysis, reduces the total volume by approximately 35 %. Additionally, the system can recover low-grade heat from the environment through the absorption heat pump, achieving an energy storage efficiency of 1.07 and an energy storage density of 56.13 kWh/m³. The proposed system and its dynamic control method are well-suited to intermittent solar energy, increasing the system flexibility, and thus expanding renewable energy utilization potential, especially those involving multi-energy complementary systems.