Green Technology & Innovation 2979-1456 Caravel Press 10.36922/gti.6191 2025.001 Experimental comparison of erythritol and erythritol-granite pebble mixtures as heat storage materials for solar cooking https://orcid.org/0000-0002-1992-5498 MawireAshmore ashmore.mawire@nwu.ac.za AbedigambaOyirwoth P. oyigamba@kyu.ac.ug Department of Physics, Material Science, Innovation and Modelling Research Focus Area, NorthWest University, Mahikeng, North West, South Africa Department of Physics, Faculty of Science, Kyambogo University, Kyambogo, Uganda 19022025 1 1 12 19 February 2025 © 2025 The Author(s). Published by Caravel Press. 2025 This is an open access article under the CC BY 4.0 licence.

In this article, a comparison is presented between a pure latent heat storage system (erythritol) and a mixed storage system consisting of equal mass ratios of erythritol and granite pebbles (5 – 10  mm) for a solar cooking application. Two small black stainless cooking pots with a capacity of 1  L were placed inside two larger 5  L cooking pots to form simple storage cooking pots. The space between the pots was filled with thermal energy storage (TES) material. In the first configuration, the space between the pots was filled with 2 kg of erythritol. In the second configuration, the storage system consisted of 1  kg of erythritol and 1  kg of granite pebbles in the same space. The first experimental tests involved charging the storage cooking pots without any load for 4 h, followed by discharging them using heating loads in insulated wonder bags to evaluate off-sunshine cooking performance for another 4 h. The second experimental test involved simultaneous cooking and heat storage alternating between charging and discharging cycles. Experimental results showed that the mixed storage system achieved higher temperatures than the erythritol storage system during charging without cooking. During discharging cycles, the heat utilization rate was faster for the mixed storage system than for the erythritol storage system. Both storage systems enabled the cooking of multiple meals within an 8-h cooking period. However, at the end of the experiments, the erythritol storage system retained higher temperatures than the mixed storage system. Future work will focus on characterizing the thermophysical properties of the mixed storage system, optimizing the erythritol-to-granite mixing ratio for improved thermal performance, and investigating alternative, locally available TES materials – such as sandstone, marble, limestone, and xylitol – for potential use in mixed storage systems.

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