Experimental investigation of shellac wax as potential bio-phase change material for medium temperature solar thermal energy storage applications

• Published in: Solar energy 2022-01, Vol.231, p.1002-1014
• Main Authors: Rudra Murthy, B.V., Thanaiah, Kumara, Gumtapure, Veershetty
• Format: Article
• Language: English
• Subjects: Charging; Conduction heating; Convection; Discharge; Domestic water; Drying; Efficiency; Energy; Energy storage; Flow rates; Flow velocity; Free convection; Heat; Heat transfer; Heat transfer fluid; Inlet temperature; Latent heat; Melting; Palmitic acid; Paraffin; Paraffin wax; Phase change material; Phase change materials; Reduction; Shell and tube; Shellac; Solar energy; Solar heating; Solidification; Stearic acid; Thermal energy; Thermal performance; Water heating
• ISSN: 0038-092X; 1471-1257
• DOI: 10.1016/j.solener.2021.12.019

[Display omitted] •Shellac wax as Bio-PCM for medium temperature solar thermal applications.•Impact of natural convection on the PCM melting rate.•Obtained thermal efficiency (73.4%) is comparable with the existing organic PCMs.•Optimum values of operational parameters are obtained. Thermal performance of shellac wax as a novel bio-phase change material (BPCM) and Therminol®-55 as heat transfer fluid (HTF) in a vertical shell and tube latent heat thermal energy storage (LHTES) unit is analyzed experimentally. Operational parameters considered, namely HTF flow rate and inlet temperature in the range of 2–5 LPM and 100–120 °C, respectively. The comprehensive study of contours and plots reveals the impact of natural convection and the progress of the melting and solidification front in the charging and discharging process. As the HTF flow rate increases, the charging rate improves considerably, and a maximum reduction in melting time is obtained as 43.6% for 4 LPM. The maximum reduction in melting time and storage efficiency are 42.2% and 73.4%, respectively, at 120 °C and 4 LPM. However, the discharging process's increased flow rate has no significant effect on solidification and discharge efficiency, which attributes the dominant mode of heat transfer is conduction during the solidification. Shellac wax storage efficiency is comparable to existing paraffin wax, stearic acid and palmitic acid-based LHTES unit. In this regard, shellac wax can be a potential Bio-PCM for medium temperature range (60–80 °C) solar thermal applications such as domestic water heating and food drying.