Abstract
Air to water electric heat pumps are one technological solution to achieve energy defossilisation goals for heating of residential building stock. Nevertheless, they may not necessarily be the only solution for all residential building stock. A case in point is where extensive fabric refurbishment is impracticable or where electric heat pumps are installed where low ambient temperatures prevail and/or high water delivery temperatures must be utilised. For such instances, hybrid (gas and electric) heat pumps offer an alternative option by facilitating fuel source switching between electricity and gas, when ambient temperatures are low or high water supply temperatures are required. In the current study, the effectiveness of an air-to-water electric heat pump and hybrid heat pump are examined for different building retrofit scenarios for a residential dwelling located in Ireland. This is achieved by means of a sensitivity study of a validated building simulation model, incorporating both heat pump systems, subject to different building retrofit scenarios. Relative to a conventional oil-fired boiler, for a deep building retrofit scenario, the hybrid and electric heat pumps achieve primary energy savings of 73% and 70%, respectively. For a minimal building retrofit scenario, the respective primary energy savings are 57% and 52%. For the deep retrofit scenario, compared to the baseline building with no retrofit measures, the carbon footprint reductions were found to be (8.5 gCO2e/m2/year or 44%) for the hybrid heat pump, (10.31 gCO2e/m2/year or 45%) for the electric heat pump, and (17-21 gCO2e/m2/year or 43-53%) for oil or gas boiler systems. Finally, the deployment of either an electric heat pump or hybrid heat pump for deep building fabric retrofit achieves approximately half heating system capital cost return within 20 years.
Published Version
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