Abstract: A brine tank similar to that used in an ice plant is used to store heat added to a thin sheet of water by the sun and/or ambient air. The stored heat is removed from the water by a heat pump for space heating. Water in containers in the brine may, on occasion, furnish its heat of fusion to the evaporator of the heat pump. In hot weather a reversing valve causes the erstwhile evaporator to become the condenser and to transfer heat to the brine. This heat is then dissipated by the water when it is sprayed onto the roof.