22 May 2008
We simulated a system using a standing column well (SCW) as a water-heat
source, with an air/water-to-water hybrid heat pump capable of switching between air and
water cooling. Although single-tube wells can reduce costs because they do not require the
construction of a new reducing well, water returning from the heat pump could create a short
circuit, adversely affecting the system. It is also expected that the amount of power required
by the pump could vary greatly depending on the level of the groundwater table and other
factors. We performed a comparative assessment of annual performance factors (APF) for
the differences between systems using R407C and R410A refrigerant, differences in
temperature due to SCW short circuits, differences in well-pump power, and differences due
to climatic zone. As a result, we calculated an APF of 5.24 for the base system. We also
found that a 21% improvement to APF can be expected by changing from R407C to R410A.
We additionally found that under each condition, air/water hybrid cooling improved APF by 2
to 7% compared to water cooling.