The Future of District Heating and Cooling Networks

This work offers a perspective on the potential future of district heating and cooling networks, by examining their evolution, discussing the advantages and disadvantages of emerging Fourth Generation District Heating (4GDH) technologies and exploring the impact of potential regulatory, policy, business and societal changes on their deployment.

4GDH has gained wide acceptance as a means to decarbonise heating, by distributing heat from low carbon sources to end-user buildings. It differs from earlier generation district heating technologies by operating at lower nominal temperatures – less than 70 °C as an annual average. This means that heat can be distributed with lower thermal losses compared to earlier generations and that heat from primary fossil fuel consumption can be replaced with lower temperature and lower carbon alternative heating sources.

Within the category of 4GDH, several configurations exist with respective advantages and disadvantages, including so-called ‘Cold’ Ultra-Low Temperature District Heating (ULTDH) and Combined Heating and Cooling (CHC) configurations, the latter of which permit provision of cooling as well as heat by virtue of their low operating temperatures. Cold district heating differs from more conventional or ‘Warm’ 4GDH configurations in that they require the use of decentralised heat pumps to raise or lower temperatures at the point of use.

However, taking the United Kingdom as a case study, whilst it remains to be seen whether any given 4GDH configuration will ultimately prove to be superior, imminent policy changes to move away from stand-alone gas central heating, as well as decarbonisation efforts in other energy sectors, may cause technological lock-in to a particular configuration at the expense of others. The notion of path dependence, in which small actions are positively reinforced over time through increasing return effects, may ultimately prove more important than the respective lifetime economic and environmental costs of the different 4GDH configurations.

The following initiating measures are therefore identified in the report to help prevent Cold networks from being overlooked as a viable alternative to conventional 4GDH configurations:

• The widespread capture of low-temperature waste heat should be mandated or at least strongly incentivised;
• Affordability and consumer expectations of building integrated heat pump installations need to be improved, possibly via innovative ownership models;
• The installation of heat network pipes should be considered independent of heat production, improving accessibility and customer choice; and
• Power system flexibility services tailored to heat pump demand side response need to be widely publicised and accessible.

Authors:

Michael Taylor, Cardiff University
Meysam Qadrdan, UKERC, Cardiff university
Bridget Woodman, University of Exeter
Jianzhong Wu, UKERC Co-Director, Cardiff University