Thermal Compatibility Screening of Accessible Phase-Change Materials Using an Idealized Zone Energy-Balance Model

Phase change materials (PCMs) store heat as they melt. However, their melting temperature must fit the condition(s) in which they are used. In this study, we compared refined coconut oil, soy wax, and a high-melting paraffin wax proxy, using published properties and an idealized spreadsheet model, alongside a Python simulation. We assigned each material a mass of 50 kg in a 50 m³ zone, where their heat input profiles and the representations of room thermal mass were built on an assumption and not building measurements. The baseline daily maximum was 43.18 °C. Coconut oil, which was modelled at a melting point of 24.5 °C with a heat fusion of 105 kJ/kg, completely melted and lowered that respective maximum to 39.72 °C, which is a calculated reduction of 3.47 °C. Soy wax at 43.92 °C and paraffin at 53.0 °C did not melt in the default case. Increasing the heat input by 5% helped produce partial soy-wax melting, which showed that the results depend on the according scenario. In addition, an engineered RT25 comparator was considered separately because its published storage rating includes both sensible and latent heat. Independently reproduced ERCOT price averages yielded only $0.4119/year in a full-capacity coconut-oil usage scenario using 2025 prices, explicit cost, and operating assumptions. Such results help us support matching transition temperature to operating conditions as an initial screening step. However, they do not establish measured room cooling, electricity savings, or installation feasibility. Keywords: bio-phase change materials; bio-PCMs, coconut oil; soy wax; thermal energy storage; thermal compatibility; peak-load shifting