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Abstract

Thermal storage is one solution to efficiently use the renewable energy. In this paper we analyze the impact of thermal storage on the building heating and domestic hot water autonomy in the case of local renewable energy production. To be relevant, various building types have been investigated. We proposed earlier a PCM storage solution [1] that solved the efficient heat extraction challenge for building heating [2] [3]. In this paper, we present the first results of a PCM storage system for domestic hot water with measurements of discharge heating power in line with computational fluid dynamics simulations. A comparison of both heat storage systems is however not possible because of their different structures. In order to compare the efficiencies of the PCM discharge for hot water production and air temperature control, we have designed a new PCM heat exchanger that can be used in both cases. Its structure consists of several PCM layers sandwiched between loading and discharge layers. By circulating air or water in the discharge circuit, the heat exchanger can be used for heating air or water, respectively. For both use cases, a three-dimensional analysis of the phase change and calculations of the charge/discharge powers were performed for the fusion and solidification processes. We obtained heating discharge powers ≥ 2.6 kW/m3 for 8 hours for air and ≥ 65 kW/m3 for 13 minutes for water with a respective total storage capacity of 28 kWh/m3 and 37 kWh/m3 . The heat extraction of air and water flows and their time dependence are discussed according to the percentage of liquid PCM and the temperature profile of the discharge flow inside the heat exchanger.

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