A typical central chilled-water system rejects heat returned from the building loop to a cooling tower via the chiller condenser coils. An alternate arrangement is to circulate the warm return-water through a heat-recovery chiller, to reject heat to the fluid flowing on the condenser side of the chiller. This warms the water sufficiently to be used for either hydronic heating or domestic water heating.
Disregarding the thermal inefficiency of the chiller, this system provides “free heating.”
An alternate arrangement is to pipe the condenser water from online chillers to a heat-recovery chiller. A cooling tower in parallel to this chiller will ensure that heat beyond the heat-recovery chiller’s capacity can be rejected.
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Excerpt from Energy Conservation Projects.