Heat pumps in district heating and cooling systems

Heat pumps and district heating might look like competitors for the same market shares. But that is only at a first glance. Looking into the technologies and at the entire energy system it becomes clear that a combination of the two has many advantages. This has been the topic of HPT TCP Annex 47.

A study carried out in 14 countries in Europe shows that district heating is an economically viable solution in most urban areas. More than half of the heat demand could be covered, ultimately also reducing greenhouse gas emissions and primary energy demand. Adding large-scale heat pumps to this, the study results imply that the systems would become more flexible and supply-safe. A catalogue including as many as 39 examples of heat pumps integrated in different ways in distict heating systems has been compiled within Annex 47.

Based on this, district heating in general, and heat pumps connected to the grids in particular, are predicted to play a key role in the energy grid and supply for the future. Approximately 25% of the energy demand in the district heating grid could be supplied by heat pumps. With a wide deployment of both district heating and heat pumps, green house gases could be reduced with as much as 70% compared to the current situation.

Heat pumps can be a key technology in the future district heating grid in different ways:

  • A balancing technology when the electrical production fluctuates;
  • Contribute to phasing out fossil fuels from the energy system;
  • Make use of very low (below 60 °C) and ultra-low (below 45°C) temperatures in the district heating grid;
  • Minimize grid losses in the district heating grid.

Despite the obvious upsides, heat pumps play a minor role in European district heating networks of today. And there are a number of barriers for a broader deployment. In many areas, there is no large-scale heat source to be used in the district heating system. In other cases, the temperature of the source is so low that the efficiency is challenged. On the other hand, a high temperature of the network is also a challenge, reducing the efficiency of the heat pump. Such high temperatures also lead to large heat losses.

If these barriers are overcome, a scenario would be possible where half of Europe’s heating demand is covered by district heating. And where a quarter of this comes from heat pumps. The acceptance for this is on the rise, but more effort is needed in terms of research and implementation.

Svend Pedersen, Denmark (Danish Technological Institute)

The text has been shortened by the HPC team

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