Who first invented the air energy water heater?

Air energy water heater, also known as heat pump water heater, entered China for a short time, but in fact, air energy heat pump technology was invented in 1924, but it was not fully applied at that time. Until the 1960s, when the world energy crisis broke out, air-energy heat pump gradually rose because of its energy saving and no pollution to the environment, and thus began to enter the historical stage.