Heat pump system

A method of heating a space, comprising:

• circulating refrigerant in a closed loop system including a first heat exchanger and a second heat exchanger, the circulating step including
• pressurizing liquid refrigerant to a first pressure;
• heating the liquid refrigerant in a third heat exchanger to form a refrigerant vapor;
• compressing refrigerant by a compressor to a second pressure, wherein the compressor is at least partially driven by refrigerant vapor received from the third heat exchanger;
• supplying one of the first and second heat exchangers with refrigerant from the compressor;
• supplying refrigerant from the other of the first and second heat exchangers to the compressor;
• and
• selectively supercharging the refrigerant supplied to the compressor from said other of the first and second heat exchangers.

A heat pump system, comprising:

• a closed loop circuit including
• a liquid pump,
• a first heat exchanger located downstream of the liquid pump;
• a refrigerant compressor driven by refrigerant flowing from the liquid pump through the first heat exchanger;
• a second heat exchanger fluidly coupled to the refrigerant compressor;
• a third heat exchanger fluidly coupled to the refrigerant compressor, the second heat exchanger receiving refrigerant from the refrigerant compressor and the third heat exchanger receiving refrigerant from the second heat exchanger and supplying refrigerant to the refrigerant compressor;
• and
• a supercharger located between the third heat exchanger and the refrigerant compressor.