Edible oils as practical phase change materials for thermal energy storage

Abstract

Edible oils could provide more accessible alternatives to other phase change materials (PCMs) for consumers who wish to build a thermal energy storage (TES) system with sustainable materials. Edible oils have good shelf life, can be acquired easily from local stores and can be less expensive than other PCMs. In this work, we explore whether margarine, vegetable shortening, and coconut oil are feasible PCMs, by investigations of their thermal properties and thermal stability. We found that margarine and vegetable shortening are not useful for TES due to their low latent heat of fusion, ΔfusH, and poor thermal stability. In contrast, coconut oil remained thermally stable after 200 melt-freeze cycles, and has a large ΔfusH of 105 ± 11 J g-1, a low degree of supercooling and a transition temperature, Tmpt = 24.5 ± 1.5 °C, that makes it very useful for TES in buildings. We also determined coconut oil's heat capacity and thermal conductivity as functions of temperature and used the measured properties to evaluate the feasibility of coconut oil for thermal buffering and passive heating of a residential-scale greenhouse.