Heat storage system and method

A thermal energy system comprising:

• a solar heat collector for heating a heat collecting liquid alkali metal to a temperature within the range of from about 600.degree. to 1200.degree. F.;
• a housing containing a bed of rocks for storage of thermal energy;
• a heat transfer gas in heat-exchange relationship with said bed of rocks, said heat transfer gas comprising air;
• means for moving said air through said bed of rocks at an apparent velocity of from about 1 to 6 ft/sec;
• means for causing said liquid alkali metal and said air to flow in counter-current, indirect, heat-exchange relationship with one another, said means including means for reversing the flow of said liquid alkali metal and said air for the introduction or withdrawal of heated air from an upper portion of said bed of rocks;
• means for passing said liquid alkali metal in indirect heat-exchange relationship with a source of water whereby said water is converted to steam;
• and
• means operatively associated with said steam to extract mechanical energy therefrom.

A method of storing and recovering thermal energy comprising:

• providing a source of heat and a heat collecting liquid;
• passing the heat collecting liquid in a heat-exchange relationship with the source of heat;
• providing a housing containing a bed of rocks for storage of thermal energy and a heat transfer gas in direct heat-exchange relationship with said bed of rocks;
• passing said heat collecting liquid and said heat transfer gas in a counter-current, indirect, heat-exchange relationship with one another, said heat transfer liquid and said heat transfer gas being maintained at a temperature within a range of from about 600.degree. to 1200.degree. F.;
• passing said heat transfer gas through said bed of rocks at an apparent velocity within a range of from about 1 to 6 ft./sec;
• reversing the direction of the flow of said liquid and said gas such that heated gas is introduced or withdrawn from an upper portion of said bed of rocks;
• providing a working fluid;
• passing said working fluid and said heat collecting fluid in heat exchange relationship with one another to transfer heat to the working fluid;
• and
• extracting energy from said heated working fluid.