Better designs of heat pump exist for use with a wider range of operating temps however, the offerings currently available commercially are all single stage and quite basic by comparison. There is the complication of different optimum refrigerant in the cascade design as well.. Confusingly some are described as dual mode, where the single compressor has switched bypass ports in the middle of the scrolls that allow better optimised operation at two different pump rates (as opposed to variable speed drive - compressors get inefficient at low rates, as the refrigerant has time to sneak back round the outside of the moving bits.).
diagrams below indicate some possible futures that may make it just about possible have an ASP with gas boiler exit temperatures and sensible COP without too much upheaval. Just have to wait for them to make it out of the lab into production. (Evaporator is cold side, condenser is hot side...,)
Better designs of heat pump exist for use with a wider range of operating temps however, the offerings currently available commercially are all single stage and quite basic by comparison. There is the complication of different optimum refrigerant in the cascade design as well.. Confusingly some are described as dual mode, where the single compressor has switched bypass ports in the middle of the scrolls that allow better optimised operation at two different pump rates (as opposed to variable speed drive - compressors get inefficient at low rates, as the refrigerant has time to sneak back round the outside of the moving bits.).
diagrams below indicate some possible futures that may make it just about possible have an ASP with gas boiler exit temperatures and sensible COP without too much upheaval. Just have to wait for them to make it out of the lab into production. (Evaporator is cold side, condenser is hot side...,)
