handled separately. Instead, we need to think horizontally to integrate sectors and use opportunities such as the co-production of heat and power (CHP), DH heat pumps, heat storage, and utilization of excess heat from hydrogen production. System integration, also known as sector coupling, is only possible if strategic energy planning is prioritized. This is precisely what has happened with the latest Directive on Energy Efficiency EU2023/1791, which introduces an obligation for municipalities/cities with more than 45,000 inhabitants to draw up plans for heating and cooling. The report “Optimal Electrification of Space Heating - Comparison of District Heating and Individual Solutions” - prepared by Grøn Energi in 2020, is admittedly a few years old and focuses on Danish conditions. However, the challenge addressed is still relevant both in and outside Denmark.
But – as documented below - the two individual, electrici- ty-based solutions challenge the power system:
The low energy efficiency increases the need for further expansion of green power production. Electrification via electric heating increases the need, while district heating provides the lowest need for new, green power production, such as new offshore wind farms. The load on the power system is high, especially in winter. Electric heating has a significantly higher load on the power grid than district heating with large, electrically driven heat pumps. Electricity consumption is inflexible and does not match wind and solar power production; seasonal variation and faster variation on an hourly/daily level are challenges. The individual solutions put pressure on the power system when it is cold and the power production from wind and sun is low (e.g., in windless winter weather). The report mentioned earlier in this article is based on a standard Danish house of 130 m2 with annual energy consumption for heating and domestic hot water of 18.1 MWh (see Fig. 1). The figure shows that district heating is the superior solution for heating the house. Not surprisingly, electric heating consumes the most electricity because all the energy must come from electricity. The individual heat pumps consume less electricity, as part of the energy is obtained from the outside air. However, the outside air is cold in winter, so the heat pump is less effective when the heat demand is highest.
How do we intelligently convert our space heating to renewa- ble energy?
Electrification of space heating – three alternatives If the heating of buildings is to be based on electricity, this can be done in three alternative ways:
Direct electric heating, such as electric underfloor heating and electric radiators.
Individual heat pumps in the individual homes (air/water or air/air).
Electrification via district heating (large heat pumps).
Figure 1: Three ways to heat the same house. Electricity consumption for heating a standard house when heated respectively with electric heating, individual heat pump, and district heating partly (70%) based on a large, electrically powered heat pump. The curves are based on monthly averages.
28 HOTCOOL no.6 2024
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