DEMAND RESPONSIVE SOLAR-POWERED INTEGRATED COOLING, HEATING AND HOT-WATER SYSTEM
A solar-powered heating, cooling and hot water system is proposed by integrating absorption chiller/heat pump with a latent heat thermal energy storage (LHTES) system. The LHTES extends the operation of the system to evening hours where demand is at peak and solar energy supply is diminished. Heat pipe collectors absorb and transfer solar thermal energy to a LHTES unit where the thermal energy is stored in the form of latent heat of fusion of molten phase change material (PCM). Another set of heat pipes transfer the heat from the LHTES unit to heat exchangers associated with hot water, regenerator unit of the absorption cycle, and hot air. A thermal network model is developed to study the transient response of the system on a typical solar day. Various design parameters such as storage tank size and heat pipe spacing are adjusted using the model to deliver the required heat transfer rates while keeping the size and mass of LHTES at a minimum. The heat transfer results are also used to conduct an exergy analysis. It is demonstrated that the proposed storage system benefits from reduced mass and size compared to single phase systems due to the higher energy density of PCM for relatively small temperature differentials encountered in the HVAC applications. Moreover, the proposed system offers higher exergy efficiencies compared to single phase systems due to thermal storage and recovery with minimal temperature variations.