The RELaTED concept for Ultra-low temperature district heating

RELaTED will define ultra-low temperature district heating systems as: district heating systems that supply heating to the customers at a temperature level where production of domestic hot water requires a supplementary heat source to deliver satisfactory domestic hot water temperatures.

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District heating companies, equipment manufacturers, consultants and researchers have discussed definitions of district heating and cooling in general, and also ultra-low temperature district heating. This explains the different definitions and most used terms to give the reader not familiar with district heating the background of this system and the technology options.

In RELaTED, the supply temperature limit will depend on national requirements set to prevent legionella bacteria growth in domestic hot water systems. Though, all district heating systems supplying district heating at temperatures below 50 °C will be considered ultra-low temperature district heating systems (ULT DH).

In the report “Benchmark for performance levels” (C. H. Christiansen, N. Winther, Ecoheat Cities WP2-report, 2012), the following indicative temperature levels and definitions were specified:

  • DH High-Temperature System (HT), 100/50 °C
  • DH Low-Temperature System (LT), 80/40 °C
  • DH Very Low-Temperature System (VLT), 60/30 °C
  • DH Ultra Low-Temperature System (ULT), 45/30 °C
  • District cooling systems (DCS), 10/15 °C

The HT/LT definitions of this work were based on Euroheat & Power’s guideline on district heating substations (Guideline for District Heating Substations, Euroheat & Power, October 2008).

Other references are using different generations (periods in time) of district heating to define the temperature level:

  • 3rd Generation District Heating (3GDH): Temperature level < 100 °C
  • 4th Generation District Heating (4GDH): Temperature level < 50-60 °C (70) °C. The brackets indicate the temperature can go up to 70 °C in winter.

This implies that both the VLT and the ULT definitions introduced above are contained in the definition of 4th generation district heating.

Want to know more about Low-temperature district heating concepts? Read the full article here.