Thermal performance analysis of sensible and latent heat thermal energy storage tanks: A contrastive experiment

Abstract The thermal energy storage plays a fundamental role in improving the efficiency and reliability of solar energy applied in the building engineering and its conventional techniques are Latent and Sensible Heat Thermal Energy Storage (LHTES and SHTES). To analyze the thermal performance of LHTES-Tank and SHTES-Tank with paraffin RT55 and water as thermal storage mediums respectively, a contrastive experiment was done. The experiment included 5 thermal charging and discharging cycles by changing Heat Transfer Fluid (HTF) temperatures between 20 °C and 80 °C. Results show the thermal discharging was more difficult than thermal charging in LHTES-Tank. Most paraffin could melt entirely but cannot solidify completely, while around 19.36% of paraffin in LHTES-Tank was always solid or liquid, and thereby acted as a dead mass. Paraffin had the higher thermal storage capacity than water only in the phase-change temperature range, so water may play the thermal storage potential more efficiently than paraffin under the large HTF temperature difference. Also based on this reason, LHTES-Tank had only a little advantage in thermal and exergy efficiency compared to SHTES-Tank under the HTF temperature of 20°C–80 °C, but its optimization potential was showed to be very large. Finally, the main existing problems were summarized according to thermal behavior of LHTES-Tank.