Conceptual design and dynamic simulation of an integrated solar driven thermal system with thermochemical energy storage for heating and cooling

Abstract

This study presents a new integrated thermal system (MiniStor), which uses a thermochemical heat storage (TCM) technology based on a reversible reaction between an ammoniated calcium chloride salt and ammonia (CaCl2/NH3) cycle to generate both heating and cooling. The current system will be installed in a residential demo site in Sopron, Hungary. The MiniStor storage system is combined with other key components, to formulate an integrated system capable of providing sustainable energy, while utilizing renewable energy sources and specifically solar energy. The current study presents simulations of the system operation, aiming at determining the basic design and operational aspects of the system. A thermodynamic model of an integrated thermal system that consists of a photovoltaic thermal collectors and flat plate solar collectors field coupled with a TCM unit and phase changing material units (PCM) for energy storage was developed in Aspen Plus Dynamics, integrated with Matlab/Simulink. Photovoltaic thermal and solar collectors facilitate an efficient conversion of the solar energy into electricity and hot water to feed the TCM reactor. Furthermore, the latter is an essential component of the suggested process design, as it supports the long term and efficient operation of the MiniStor system. PCM heat storage units facilitate the storage of the excess heat generated during the operation of the system, increasing its flexibility. In the performed simulations, different approaches regarding the system behaviour, operating conditions and operation cycle duration are examined. Dynamic simulations showed that the system can cover the heat demands of the building at an average minimum rate of 81% and maximum of 93% in winter months. In summer months, dynamic simulations showed that the cooling coverage has an average value of 34%. Both thermal energy from the Heat Pump Cycle (COP=3.63) as well as from the charging mode of the reactor result in an overall system COP for heating and cooling equal to 1.71 and 0.47 respectively. Finally the system efficiency is equal to 128% for heating (with the RES-based heat input varying from 16% up to 100%) and 41% for cooling.