This is a heat engine which takes energy from the air on the exterior of the house. There is a part inside your house and outside. On the inside, there is an air compressor which compresses a liquid. When that liquid is compressed, it heats up before a heat exchanger brings warm air into the house. After that, the liquid goes towards the outside half and expands, causing it to cool down. This cool liquid takes some heat from outside back towards the compressor inside and the cycle continues