PCM storage for solar DHW: From an unfulfilled promise to a real benefit

• Published in: Solar energy 2011-09, Vol.85 (9), p.2033-2040
• Main Authors: Kousksou, T., Bruel, P., Cherreau, G., Leoussoff, V., El Rhafiki, T.
• Format: Article
• Language: English
• Subjects: Accumulators; Applied sciences; Collectors; Domestic hot water; Electrical engineering. Electrical power engineering; Electrical machines; Energy; Energy. Thermal use of fuels; Environmental conditions; Equipments, installations and applications; Exact sciences and technology; Heaters; Latent storage; Mathematical models; Miscellaneous; Natural energy; PCM; Regulation and control; Solar energy; Solar thermal conversion; Storage tanks; Stores; Tanks; Transport and storage of energy; Various equipment and components
• ISSN: 0038-092X; 1471-1257
• DOI: 10.1016/j.solener.2011.05.012

► Physical model is used to describe the behavior of the heat storage tank with PCM. ► Realistic environmental conditions and typical end-user requirements are imposed. ► The melting point has been identified as one of the most important parameters for optimal operation of the DHW system. The present numerical study is concerned with the use of phase change materials (PCMs) in solar-based domestic hot water (DHW) systems. During the last decade, the majority of the studies related to that issue concluded that the recourse to PCMs-based storage units was quite promising in order to enhance the overall performances of solar-based DHW systems. One recently interesting published numerical study ( Talmatsky and Kribus, 2008), suggested though that this beneficial impact is not guaranteed since the gains observed over the day period brought by the presence of PCMs to store the solar energy were compensated by the losses undergone by the storage tank during the night. The origin of this absence of any beneficial impact of the use of PCMs in a DHW system has to be clearly understood in order to reconcile studies which indicated apparently contradictory findings. In that framework, the goal of the present contribution is to analyze the conditions under which such an absence of advantage of the use of PCMs in a DHW system were obtained in order to propose some possibilities of improvement for demonstrating the interest in using PCMs in solar-based DHW systems. Thus, the mathematical model based on the one reported in Talmatsky and Kribus (2008) is considered. This model describes the heat storage tank with PCM, collector, pump, controller and auxiliary heater. Realistic environmental conditions and typical end-user requirements are imposed.