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The important topic of modelling tanks filled with phase change materials (PCMs) is discussed in this article. Due to the increasing use of heating and cooling installations, tanks containing two types of PCMs are the subject of many experimental analyses. However, there are still deficiencies in their models, which are presented in this paper. The theory model was created in order to design two tanks, each with a volume of 2 m3. They were filled with water and containers with two PCMs. The modelled tanks were meant to replace the existing water tanks that were previously used in the solar heating and cooling installation in a research building located in the southern part of Spain. After the tanks were assembled, the model was validated during the summer period when the designed storage tanks supported the operation of the solar system operating in the cooling mode. The created model consists of a 1D description of the heat transfer in the storage tank, and also a 1D description of the phase change in the containers with the PCMs. The model takes into account the front of the phase change and also discusses its impact on the thermal efficiency of the tanks. The agreement of the water output temperature is very good and validates the model, which can then be used to provide further details on the operation of the storage system—in particular, heat fluxes or a fraction of solid or liquid PCM. [ABSTRACT FROM AUTHOR]

An important element of a solar installation is the storage tank. When properly selected and operated, it can bring numerous benefits. The presented research relates to a project that is implemented at the Solar Energy Research Center of the University of Almeria in Spain. In order to improve the operation of the solar cooling and heating system of the Center, it was upgraded with two newly designed storage tanks filled with phase change materials (PCM). As a result of design works, commercial material S10 was selected for the accumulation of cold, and S46 for the accumulation of heat, in an amount of 85% and 15%, respectively. The article presents in detail the process of selecting the PCM material, designing the installation, experimental research, and exergy analysis. Individual tasks were carried out by research groups cooperating under the PCMSOL EUROPEAN PROJECT. Results of tests conducted on the constructed installation indicate that daily energy saving when using a solar chiller with PCM tanks amounts to 40% during the cooling season. [ABSTRACT FROM AUTHOR]

• Solar cooling/heating extended to cover over-night demand with storage systems. • A mixed tank, with PCMs for heating and cooling, is used. • Longer times can be achieved with PCM-based storage tanks than water tanks. • A reduction of more than 80% in electricity compared with compression cycle. • Heating can be provided for the whole night. The performance of different thermal energy storing systems to provide over-night air-conditioning for a limited space in an institutional building in south Spain are compared with conventional air-conditioning (both for refrigeration and heating). In summer, the storage tanks are charged with a solar-assisted absorption chiller during day-time, and used to cover the over-night demand, whereas in winter a heat exchanger is used during the day to charge the tanks. Thermal energy has been stored in two chilled water tanks (with total capacity of 5000 L) or in two tanks (total volume 4000 L) containing two phase change materials (PCM): a PCM with melting point of 10 ° C for refrigeration, and a PCM with melting temperature of 46 ° C for heating. Our results show that the storing in PCM is more convenient, providing air-conditioning service for approximately 4 h 30 min in refrigeration, with a significant reduction of the electricity consumption with respect to the conventional system. The chilled water tanks can cover the demand for 4 h (scaled down to 3 h 12 min if the capacity is 4000 L), with even lower electric consumption. In winter, on the other hand, the tanks can cover fully the demand of overnight heating. Our results prove the viability of thermal storing, in particular using PCM, to extend the application solar cooling and heating to night-time, which is economically feasible, in a fully operational building. [ABSTRACT FROM AUTHOR]