A Knowledge Transfer Project with Highview Power experimentally characterised material, investigating the relationship between physical and cryogenic materials. This study focused on gravel properties, at both ambient and cryogenic temperatures, to aid in the simulation of large scale thermal packed beds which are used to improve the efficiency of the Liquid Air Energy Storage (LAES) system. Novel methods for measuring material properties were utilised, namely the density, specific heat capacity and thermal conductivity. Multiple packed beds were constructed in the lab to evaluate the thermal performance with different aspect and particle-to-packed bed diameter ratios. Cyclic testing of materials was conducted to evaluate and produce prediction models for gravel fracturing and material degradation. This project resulted in the completion of 1-D and 3-D models, which can be used to predict the thermal performance of a packed bed under varying conditions, over a wide temperature range.
An Innovate UK project, in partnership with Highview Power, focused on the assessment of novel mixtures of molten salts for the high grade thermal storage of an LAES system. A comprehensive literature review was carried out on lower melting point molten salts, resulting in a useful database of the most relevant physical properties, namely melting and degradation temperature, viscosity, specific heat, density, thermal conductivity and costs. With this information, molten salt mixtures were replicated on Aspen+ through a novel hybrid approach, implementing different correlations found in literature as well as Aspen data. Thanks to the numerical simulations, novel alternative mixtures were evaluated in the temperature range suggested by the industrial collaborator. A salt performance index was utilised to compare these alternative mixtures against the original published in literature. The only parameter that the numerical simulation could not capture was the melting temperature, thus an experimental investigation was performed, resulting in two promising alternatives that provide high performance boost despite a small increase in melting temperature. Overall, a methodology to tailor and select novel molten salts mixtures has been developed and proven to be reliable and effective.