Experimental study of Lannea microcarpa seed oil as a heat transfer fluid or thermal energy storage material for medium-temperature applications

Abstract

In this study, we investigated the suitability of Lannea microcarpa seed oil (LaMSO) as a heat transfer fluid (HTF) and thermal energy storage material (TESM) for medium-temperature applications, focusing on its performance in concentrated solar power (CSP) plants. LaMSO demonstrated higher specific heat capacity than both Dowtherm A and Xceltherm 600 across the temperature range of 30 °C to 300 °C. It also exhibited a volumetric thermal energy storage density similar to, or approximately 10 % greater than, that of Dowtherm A and Xceltherm 600 at 210 °C. The oil was subjected to isothermal aging at 210 °C for 500 h and 1000 h, followed by analysis of its thermophysical and chemical properties. Thermogravimetric analysis demonstrated excellent thermal stability, with less than 3 % mass loss after 1000 h of aging. The density remained relatively unchanged, indicating consistent performance as a HTF or TESM. Despite an increase in viscosity at 40 °C, the viscosity at 100 °C remained comparable between the new and aged LaMSO samples. Furthermore, the flash point also showed no significant change, remaining high even after 1000 h of aging. However, challenges arise from the increase in the melting point due to oil saturation, which poses a risk of solidification in pipelines or tanks in certain climates. From the perspective of thermal storage cost per kWh, LaMSO is cheaper than Dowtherm A and Xceltherm 600, being approximately 8 times and 3 times less expensive, respectively. Overall, the findings suggest that LaMSO holds promise as an effective and sustainable alternative for HTF and TESM applications across a wide temperature range, contributing to advancements in renewable energy technology.