Mike Jay... what would happen if instead of 55 gallon drums of water, you had a 55 gallon drum of glycol? It phase changes at 63 degrees which could do some interestingly beneficial things. Getting heat into the drum could require a circulating heat transfer liquid. [/quote wrote:
This, which melts at 27.7 C? https://www.sciencedirect.com/science/article/pii/S0927024811000365 Seems complicated and expensive, compared to water.