Evaluation of low value lipids for thermal storage applications

The urgent need to reduce greenhouse gas emissions necessitates a shift from fossil fuels to clean energy sources. Renewable energy sources like solar and wind offer enormous potential, but their intermittency requires efficient thermal energy storage (TES), where phase change materials (PCMs) play a vital role. PCMs which absorb and release latent heat during phase change, are important components of TES systems. This study examined viability of low value lipids, byproducts of crude vegetable oil refining and food production as PCMs. Four different types of animal fats, pork, goat, lamb, beef, and crude sunflower oil wax were examined as potential alternatives to highly refined, costly and petroleum based PCMs like stearic, palmitic and lauric acids, paraffin and plant-based waxes from soy and sunflower oils. Results showed that phase change temperature and thermal stability of low value lipids were similar to those of the refined commercial products. High saturated fatty acid content of beef, lamb and goat fat makes them suitable as PCM. Yet, the presence of highly unsaturated fatty acids in pork fat excludes its potential as PCM but can be used in sensible heat storage. Highly refined commercial samples had higher thermal conductivity and phase change enthalpy than the crude samples. The substandard quality of the low value crude lipids was shown to be due to improper processing and handling conditions, hence, thermal properties of these materials can easily be improved by downstream processing/refining. Furthermore, eastern red cedar wood, an underutilized, locally available and low-cost material, was demonstrated as a potential resource for high porosity carbon, serving as a support material for lipid shape stabilization. All lipid samples were successfully loaded into carbon pores by vacuum impregnation, though optimization is needed. Converting animal fats to their fatty acid methyl esters improved shape stabilization efficiency of the products. In conclusion, low value lipids present a promising alternative to expensive, refined PCMs, exhibiting suitable phase change temperatures, high thermal stability, and moderate activation energy. These materials may be utilized as PCMs in low-temperature solar units, building and electronic device temperature control, and on-farm heating and cooling applications, and small-scale processing facilities.