Eutectic mixtures of some fatty acids for low temperature solar heating applications: Thermal properties and thermal reliability

The thermal properties and thermal reliability of the eutectic mixtures of lauric acid–myristic acid (LA–MA), lauric acid–palmitic acid (LA–PA), myristic acid–stearic acid (MA–SA) as phase change material (PCM) were determined after repeated melt/freeze cycles by the method of differential scanning calorimeter (DSC). The DSC thermal analysis results indicate that the binary systems of LA–MA in ratio of 66.0:34.0 wt.%, LA–PA in ratio of 69.0:31.0 wt.% and MA–SA in ratio of 64.0:36.0 wt.% form eutectic mixture with a melting temperature of 34.2 °C, 35.2 °C and 44.1 °C, and with a latent heat of fusion of 166.8 J g−1, 166.3 J g−1 and 182.4 J g−1, respectively. The changes in the melting temperatures and the latent heats of fusion are in the range of −0.31 °C–0.14 °C and 0.9%–2.4% for LA–MA, −0.40 °C–0.23 °C and 1.5%–3.0% for LA–PA, and 1.11 °C–0.26 °C and −1.10%–2.2% for MA–SA during the 1460 thermal cycles. Based on the results, it can be concluded that the studied PCMs have good thermal properties and thermal reliability for a four-year energy storage period, which corresponds to 1460 thermal cycles, in terms of the change in their melting temperatures and latent heats of fusion.