College - Author 1
College of Science and Mathematics
Department - Author 1
Degree Name - Author 1
BA in Physics
Pete Schwartz, College of Science and Mathematics, Physics Department
To circumvent the cost and environmental damage associated with batteries, phase change materials have been employed in solar cookpots to enable cooking in unfavorable weather conditions. Researchers at Cal Poly have traditionally employed the sugar alcohol erythritol as a PCM due to its high latent heat and a fusion point above the boiling point of water, but have discovered issues with the polyol’s degradation over extended periods of cycling. This paper explores the viability of erythritol’s sister-compound xylitol as a PCM in insulated solar-electric cookers, or ISECs. An ISEC was constructed with a xylitol PCM, and the data collected from thermocouples on the pot was analyzed. Differential scanning calorimetry was employed on pure and degraded samples of both erythritol and xylitol to determine the extent of degradation and the impact of supercooling on the release of latent heat. After a short period of cycling, the onset temperature of fusion of erythritol was shown to decrease by 10 ºC. Xylitol experimentally displayed a ΔHfus of 224 J/g, whereas erythritol was found to have a ΔHfus of 372.5 J/g, which are both in agreement with literature values. It is determined that xylitol’s supercooling properties and lower ΔHfus make it incapable of cooking foods that require boiling water, which is a significant drawback compared to its erythritol predecessor. Past literature on inducing recrystallization or introducing nucleation sites is discussed.