These include water, air, water using glycol antifreeze combinations required when utilizing solar hot water systems in arctic climates, hydrocarbon oils, refrigerants, or silicones for heat transport. U.S. DOE clarifies the kinds of fluids chosen to transport heat from your solar collector and the warm water from storage tanks at a construction. Passive Solar Handbook Volume III, the Passive Solar Handbook Programming Guide, at a variant used by the U.S. Passive Solar Design Handbook Volume II, the Passive Solar Handbook Comprehensive Planning Guide, at a variant used by the U.S. Passive Solar Design Handbook Volume I, the Passive Solar Handbook Introduction to Passive Solar Concepts, at a variant used by the U.S. U.S. Department of Energy post on solar domestic water heaters to Create domestic hot water from buildings, clarifies how solar energy heaters operate.