DISTRICT HEATING GENERATIONS – Clarification of the term “District Heating Generations”
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Dr. Andrej Jentsch, IEA DHC Programme Manager,
By Dr. Robin Wiltshire, Chair, IEA DHC P rogramme,
Senior consultant Lars Gullev, Vice-chair, IEA DHC P rogramme
In the old days – i.e., before 2014 – the world was simple when it came to describing district heating systems (DHS). The systems were based on steam, hot water, or warm water. The pipes were either laid in concrete channels or pre-insulated, and the supply temperature was from 70°C to more than 200°C. District heating was based on relatively few production technologies.
However, the indication of the time of introduction for the systems - or, as stated in Figure 1, "generation"- has given rise to misunderstandings or overinterpretations. Challenges with the perception of DHS generations This visualization supports the notion of desirable transitions, with improved technologies such as pre-insulated pipes that typified 3GDH, enabling systems to run at lower temperatures than 2GDH systems. The emergence of 4GDH is being largely driven by the need to transition to post-fossil DHS devised to make best use of renewable sources and available waste heat, which may also require heat pumps to elevate their temperature. In general, a newer generation will likely increase the potential for improving efficiency and decreasing the carbon footprint.
It was simple but became challenging when the discussion turned to further developing the DHS so that it could more effectively answer the future's climate and resource-related challenges. However, the publication of the article "4th Generation District Heating (4GDH) Integrating Smart Thermal Grids into future sustainable energy systems" in March 2014 established a framework for the continued dialogue about the various DHS and the perspectives on future development. Today, most DHS professionals know Figure 1, which visualizes DHS generations and classifies them by the typical flow and return temperature, production technologies, and the typical period for introducing the systems. Subsequently, the figure has been refined, but the original primary information remains unchanged.
1 Original article by Lund, H. et al. “4th Generation District Heating (4GDH): Integrating smart thermal grids into future sustainable energy systems” 2014, Energy, 68, 1-11
19 www.dbdh.dk
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