Heating, ventilation, and air conditioning (HVAC) systems control climates in buildings and vehicles. Most systems utilize compression and expansion of a cycled refrigerant, which consumes high amounts of energy. Thermal energy storage shows promise for harnessing and utilizing waste heat, but most thermal energy storage systems utilize intermetallic alloys, which come with high costs and low energy density.

The waste heat thermal battery can store and release energy in a controlled fashion to increase efficiency. The battery is charged and discharged cyclically to supply heating or cooling from stored thermochemical energy. It uses low cost ammonia and magnesium chloride to provide high heating and cooling power. The battery gathers energy from waste or ambient heat, which allows it to be powered by sources such as truck engines, solar heat, and off-peak industrial waste heat. Its characteristics facilitate use in HVAC systems for electric vehicles and long haul trucks, energy storage systems, stationary HVAC, and waste heat recovery systems.