Heat transfer fluids compositions

An energy storing system comprising:

• at least one storage vessel containing a heat transfer fluid that comprises at least one salt suspended in an oil selected from at least one of synthetic oil and silicone oil,
• an agitator in fluid communication with the at least one storage vessel and configured to maintain the at least one salt continuously suspended in the oil, and
• a heat exchanger in fluid communication with the at least one storage vessel and configured to facilitate transfer of heat to the heat transfer fluid,
• wherein the heat transfer fluid has:
• a viscosity of about 1 cP to about 400 cP,
• a heat capacity of about 2×103 J/g to about 4×103 J/g between −40° C. and 300° C.,
• at least one liquidus temperature (phase transition) of less than 250° C., and
• about 20 wt. % to about 40 wt. % of the salt and about 50 wt. % to about 80 wt. % of the oil.