Application of phase-change material in solar hot-water system

Abstract

In this paper, hydrated salts of disodium hydrogen phosphate dodecahydrate and disodium sulfate decahydrate are employed to compose a composite hydrated salt with a ratio of 9·5:0·5. The composite hydrated salt has been used as a phase-change thermal storage material in a solar hot-water system to study the effect of phase-change material on the thermal conversion efficiency of such a system. The phase-change material is packaged in a plastic container. The experimental results show that the thermal conversion efficiency is significantly affected by the amount of thermal storage medium and solar radiation intensity. The solar thermal conversion efficiency for the 2 m2 solar panel collector could reach up to 66·4% for a thermal storage medium consisting of 38·1 kg phase-change thermal storage material and 124·7 kg water and with an averaged radiation intensity of 1243 w/m2, even at lower ambient temperatures between −7·0°C in the morning and 1·0°C at 15:00. It indicates that the use of phase-change materials in a solar water-heating system could improve the solar thermal conversion efficiency of such a system.