Modeling of Heat Losses from a PCM Storage Tank for Solar Thermophotovoltaic Systems

摘要

This work explores the influence of lateral heat losses from a phase change material (PCM) storage tank on the performance of a storage integrated solar thermophotovoltaic (SISTPV) system by means of an analytical model. The heat losses from the lateral surface of the PCM tank are modeled using Newton's law of cooling by prescribing a heat-loss coefficient on the lateral surfaces. The results show that at high heat losses, low thermal efficiencies are realized. Correspondingly larger solar concentrations are required to fully melt the PCM tank. At low heat losses, such as can be expected when using thermal insulation on the lateral surfaces, approximately 40% thermal efficiency can be realized. The results also demonstrate that a high absorber area: length of PCM tank squared (SR) ratio enables the system to have a high thermal efficiency. For a high-SR, low-heat-loss design case, having a high taper ratio, high area ratio between absorber area and inlet hole area, and small PCM tank length all achieve higher thermal efficiencies. It is expected that these SISTPV systems will be designed at steady-state to be fully molten in order to maximize thermal energy storage via the latent heat of the PCM. The analytical model developed here can be used to predict the design conditions under which the PCM tank will be fully molten. (c) 2017 American Society of Civil Engineers.