The present disclosure includes a mining system which comprises ore, waste, and a reservoir which comprises a portion of said waste through which air can flow with low resistance for storing thermal energy from a tempered air source and supplying it to a tempered air consumer, and connections for tempered air flow between said tempered air source and said reservoir and between said tempered air consumer and said reservoir. Note: As used herein, “tempered air” means air of a temperature sufficiently high to heat, or low to cool, an object to a desired temperature. For example, in a house, the furnace is a source of tempered air for heating in winter, the air conditioner a source of tempered air for cooling in summer, and the house is a consumer of tempered air.