TES, PCM, COP, Thermodynamic Efficiency, Residential System
Thermal Energy Storage (TES) with Phase Change Materials (PCM) media (solid/liquid) has been investigated as an add on component to small residential systems. Simple conceptual design on the integration of TES as add-on component to typical systems has been investigated. A basic analyis with simple cycles is to be presented to answer the question whether TES integrated with existing VCC cycles could offer energy savings. In addition, the analysis is used to study the effect of subcool and/or temperature hyserisis by using the ideal Carnot Cycle. Organic PCM materials have low thermal conducitivity (0.15w/m-C to 0.20w/m-C) compared with inorganic PCMs (~0.54w/m-C). These low values of themal conductivity impose challenges on heat exchanger designs, especially, when a simple add-on design is to be used. In addition some inorganic PCMs require to be subcooled during freezing cycle, which would impose a penalty on thermodynamic efficiency. In the paper, analysis results is to be presented for typical systems using TES as add-on components. The effect of temperature hysteresis in melting and freezing on thermal dynamic efficeincy is to be discussed in details. A simple formula of equivalent overall system efficiency in terms of charging COP and discharging COP is used to examine whether a simple integration of TES into an existing system as add-on component would offer energy savings.