High Temperature Industrial Heat Pump with Novel Method to Make Use of Shallow Low-GradeGeothermal Energy

An illustrative heat pump system includes: a positive displacement compressor, an expander, and a recuperator. The compressor provides an sCO.sub.2 flow with a pressure ≥15 MPa at a temperature ≥120° C. and a mass flow rate ≥4.5 kg/s to deliver between 1 and 10 MWth of power to a thermal load. The recuperator receives an outlet flow from a thermal source such as a geothermal well thermosiphon and directs it as a compressor inlet flow to the compressor and receives a return flow from the thermal load and directs it to the expander while converting at least some residual heat in the return flow into additional heat for the compressor inlet flow. The expander converts at least some pressure of the return flow into power for the compressor, producing an inlet flow to the source with a pressure no higher than 5 MPa at a temperature no higher than 20° C.