Quantifying the effect of radiator capacity on hybrid heat pump performance using a hardware-in-the-loop setup
Abstract
Heat pumps achieve higher efficiency (COP) if the water temperature at which they reject heat is lower. A method to lower this temperature is by increasing the capacity of the hydronic heating system. A larger heating system can deliver the same amount of heat at a lower water temperature compared to a smaller system. However, the relationship between heating capacity and COP varies depending on the system. To quantify this for a hybrid air-to-water heat pump, a hardware-in-the-loop method was employed. The heat pump was tested in a climate chamber, connected to a virtual house and hydronic radiator heating system. Tests were repeated with upgraded radiators (from Type 22 to Type 33) and finally with a revised weather compensation curve. The case study demonstrated that the increased radiator capacity and adjusted weather compensation curve resulted in a COP increase of 0.4, or ~10%.