Utilization of phase change materials in solar domestic hot water systems

Muhsin Mazman, Luisa F. Cabeza, Harald Mehling, Miquel Nogues, Hunay Evliya and Halime Ö. Paksoy

Renewable Energy, 2009, vol. 34, issue 6, 1639-1643

Abstract: Thermal energy storage systems which keep warm and cold water separated by means of gravitational stratification have been found to be attractive in low and medium temperature thermal storage applications due to their simplicity and low cost. This effect is known as thermal stratification, and has been studied experimentally thoughtfully. This system stores sensible heat in water for short term applications. Adding PCM (phase change material) modules at the top of the water tank would give the system a higher storage density and compensate heat loss in the top layer because of the latent heat of PCM. Tests were performed under real operating conditions in a complete solar heating system that was constructed at the University of Lleida, Spain. In this work, new PCM-graphite compounds with optimized thermal properties were used, such as 80:20 weight percent ratio mixtures of paraffin and stearic acid (PS), paraffin and palmitic acid (PP), and stearic acid and myristic acid (SM). The solar domestic hot water (SDHW) tank used in the experiments had a 150L water capacity. Three modules with a cylindrical geometry with an outer diameter of 0.176m and a height of 0.315m were used. In the cooling experiments, the average tank water temperature dropped below the PCM melting temperature range in about 6–12h. During reheating experiments, the PCM could increase the temperature of 14–36L of water at the upper part of the SDHW tank by 3–4°C. This effect took place in 10–15min. It can be concluded that PS gave the best results for thermal performance enhancement of the SDHW tank (74% efficiency).

Keywords: PCM; Phase change material; Stratification; Solar energy; Domestic hot water (search for similar items in EconPapers)
Date: 2009
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Citations: View citations in EconPapers (43)

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Persistent link: https://EconPapers.repec.org/RePEc:eee:renene:v:34:y:2009:i:6:p:1639-1643

DOI: 10.1016/j.renene.2008.10.016

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