Heat pumps are raising big hopes for the electrification of heating for buildings and households. However, their performance is still considered insufficient for satisfying, completely, heating demand. Their technical and financial viability, on the other hand, remains subject to different views, with some claiming that payback time is still too long and others saying they are far from achieving the required level to ensure that heating or cooling are efficiently provided.
According to recent research from the Karlsruhe Institute of Technology (KIT), in Germany, energy efficiency and building renovations may be the crucial factor to reduce heating demand, thus creating the conditions to help homeowners and real estate developers adopt heat pumps to electrify heating as much as possible.
The scientists analyzed, in particular, whether implementing building retrofitting and thermal energy storage, and installing individual hybrid heat pumps with back-up gas boilers, may help mitigate heat demand peaks in a renewable European energy system with net-zero CO2 emissions. “The European perspective is important because energy markets are already strongly coupled internationally and a cross-sectoral perspective is necessary to understand, for example, the impact of heat pump demand on electricity supply,” they explained.
In the paper Mitigating heat demand peaks in buildings in a highly renewable European energy system, recently published in Energy, the German group defined a model that considers space and water heating for the residential and services sector. “The industrial sector is not included and the required energy for cooking is incorporated in the electricity demand,” it specified. “The overall heat demand per country is distributed spatially, weighted by population density; and temporally, by creating time-series based on ambient air temperature and typical end-user behavior.”
Under this configuration, in which wind and solar contribute the largest share of electricity generation, with up to 95%, heating demand can be met by: power-to-heat, such as heat pumps and resistive heaters; gas-to-heat, such as combined heat and power (CHP), gas boilers and fuel cells; or solar thermal collectors and solid biomass-to-heat, in district heating networks. “Heat pumps of two categories are considered: ground-sourced, brine-to-water heat pumps, which are restricted to rural regions due to land requirements, and air-to-water heat pumps useable in areas with high population density,” the academics stated, noting that their model considers building renovation measures such as adding insulation material and replacing energy inefficient windows.
Through this analysis, the researchers found that, with the implementation of the three, above-mentioned measures, the overall cost for heating may be reduced in Europe, from €751 billion to €622 billion, and that building renovations may result in savings of €104 million per year. “The availability of individual back-up gas boilers has a more modest impact,” they pointed out. “In scenarios without building renovation, these provide a 6% overall cost reduction.”
According to them, building renovation, thermal energy storage and individual heat pumps with back-up gas boilers are efficient tools to mitigating heat demand peaks and may result in cost savings for the European energy system of up to 17%. “Building renovations, which result in 44–51% space heat demand savings, show the strongest effect on the reduction of total costs, with 14% cost savings,” they concluded. “Individual gas boilers that are used as back-up for heat pumps can be completely removed in rural areas with a minor cost increase of only 1-2% if the buildings are renovated.”
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