Experimental investigation of the reliability of residential standing column heat pump systems without bleed in cold climates

Typical houses located in Eastern Canada generally require a 160 m deep vertical closed-loop heat exchanger for efficient ground-source heat pump systems. Borehole drilling costs for such ground heat exchangers are still relatively high. One of the concepts that could potentially reduce these costs is the standing column system, with or without groundwater bleeding. Such a system has been successfully validated in moderate climates for relatively short periods of operation in the heating mode. The scope of this article is to determine the reliability of residential standing column heat pumps without bleed operating in extreme cold climate conditions, i.e. running in the heating mode continuously or intermittently over indefinite periods of time. The analyses and tests indicate that standing column wells are not appropriate for use with ground-source heat pumps in extreme cold climates unless some groundwater bleed is employed.

► Two standing columns shallower than closed-loop heat exchangers have been studied.
► The system heating performances are relatively high for limited periods of time.
► Without bleed, the compressor restarting in heating mode is highly problematic.
► Continuous mechanical cooling mode is efficient for long periods of time.
► Efficient dehumidification in the free cooling mode isn't achievable.