If you have a renewable energy source in the form of heat, storing it in chemical bonds could be a better alternative in terms of long term energy storage. mol

If you have a renewable energy source in the form of heat, storing it in chemical bonds could be a better alternative in terms of long term energy storage. molten salt loses approx. 50% of it's energy after 14 days, while hexametaphosphate for example, when kept as salt, can be stored probably for decades. Hexametaphosphate can be produced from cheap monophosphate salt by heating it in solution to 700c and can be kept in room temperature until it is utilized. The energy density of hexametaphosphate is around ~ 80kWh , which higher or the same as most molten salt heat storages available. Disclaimer: My company (Enzymit) develops enzymes that use polyphosphates, rather than ATP as an energy source to catalyze many types of reactions.