Maximized thermal energy utilization of surface water-source heat pumps using heat source compensation strategies under low water temperature conditions

Surface water-source heat pumps (SWHPs) are expected to replace conventional cooling and heating systems owing to their high energy efficiencies. However, the risk of freezing during heating operations makes it impossible to operate SWHPs when the surface water temperature approaches the freezing point. Accordingly, this study proposes a heat source compensation operation for maximizing the use of the water's thermal energy, allowing the SWHP to use the thermal energy storage as a supplementary heat source at low river water temperatures. The performance characteristics of a compensation-based water-source heat pump (CWHP) and hybrid compensation-based water-source heat pump (HCWHP) are analyzed using a transient simulation tool under various operating conditions. Their environmental and economic performances are also analyzed and compared with those of a conventional cooling and heating system (CCHS) based on water temperature measurements of the Han River in South Korea. As a result, the CWHP shows a 10.6 % lower lifecycle climate performance and 20.2 % lower lifecycle cost (LCC) than the CCHS. The HCWHP exhibits the lowest greenhouse gas emissions in all periods but shows a 19.5 % higher LCC than the CWHP.