Sectors
District heating
District heating networks are increasingly fed by large heat pumps that lift a low-grade source — surface water, waste heat, an aquifer — to the network supply temperature. That is a high lift, run for most of the heating season, and it is a natural fit for expansion work recovery.
The duty
A heat pump feeding a district network typically raises a source of a few degrees to a supply temperature of roughly 70 to 90 °C, so the temperature lift is large. Hydrocarbon refrigerants such as butane (R600) and pentane (R601), and other natural fluids, keep these high-temperature cycles subcritical, which is exactly the regime the expander is built for.
Networks run for most of the year, and the largest heat pumps carry the base load continuously, so the recoverable work is available for thousands of hours a season.
Why the expander fits here
The higher the lift, the more work the expansion step throws away, and the more the expander can recover. A district-heating heat pump runs one of the largest lifts of any subcritical duty, so the COP gain and the recovered work are at their most valuable here. A higher COP also means less electrical demand for the same delivered heat, which matters where the grid connection is the constraint.
What changes on your plant
The expander replaces the expansion device in the cycle; the compressor, heat exchangers and refrigerant stay in place. It suits both a new network heat pump and a retrofit of one already in service.
What would it deliver on your network?
Pick the refrigerant and set the temperature lift to your supply temperature to see the modelled COP gain in the calculator.