Development of a small-scale solar thermochemical energy storage system

Solar thermal energy has the potential to supply clean energy for applications such as heating or cooking, however times of high solar intensity are often misaligned with the diurnal or seasonal demand for thermal energy. Solar thermochemical energy storage systems (STESS) based on reversible reactions are promising solutions due to their high volumetric energy density and ability to store energy indefinitely. Reversible salt hydrate reactions are functional at low decomposition temperatures and have higher energy densities than sensible or latent heat storage. To enhance heat transfer, improve durability, and prevent agglomeration, a non-reactive matrix material is used, typically made of porous substances such as activated carbon, vermiculite, or expanded graphite. Presented here is a proof-of-concept which addresses the challenge of storing thermal energy on a seasonal or diurnal timeframe with a hybrid evacuated tube-solar concentrator reactor. Discharge temperatures of the prototype are relevant for ubiquitous residential thermal needs such as hot water or cooking. Experimental testing has proven the material can be sufficiently scaled. Outdoor trials showed that this reactor design can achieve significant desorption at the required temperatures with minimal tracking efforts, especially when augmented with provisions to increase mass flow. Included is a discussion of a future vision of how energy impoverished areas can benefit from this concept.