District heating systems (DHs) are identified as key systems to achieve a de-carbonized supply of heating energy in European Cities, as they allow the efficient integration and balancing of various sources of renewable and waste heat sources with high levels of efficiency and economies of scale. Yet, DHs only corresponds to a market share of roughly 12% of the EU heating market today. In order to increase that number, innovative solutions and technology demonstrations are needed to pave the way for expanding and modernizing existing DH networks as well as introducing and establishing DHs in emerging EU markets.

One way to achieve this evolution is by reducing the heat intensity in districts with the progressive transformation of the building stock to Nearly Zero Energy Building (NZEB) standards, with Positive Energy Buildings being increasingly common. Low (LT) and Ultra-low (ULT) temperature district heating (DH) systems present fewer technical constraints to incorporate low-grade heat sources. Also, they operate at substantially lower costs due to fewer heat losses, better energy performance of heat generation plants, which is further improved by the use of de-carbonized energy sources at low marginal costs. In the process to substitute present DH networks with LT (50-55ºC) and ULT (~45ºC) DHs, critical issues such as treatment against legionella, adequacy of heat delivery systems, methods to directly inject RES into the district energy network, etc. need to be solved.

RELaTED aims at solving these issues by providing a demonstrated concept of ultra-low temperature network solution for new district heating systems and by implementing the progressive conversion of systems already in operation.

What are the actions foreseen by the project?

  • RELaTED will be demonstrated in four different DH networks comprising different countries, climates and network scales (Denmark, Estonia, Serbia, Spain).
  • 2 regional studies will be performed to assess the feasibility of introduction of ULT DH in two Central and South EU regions.
  • In the transition to the RELaTED ULT concept, conversion route maps and hybrid schemes will ensure successful conversion of DHs already in operation, by progressive ULT conversion of subnetworks, and main heat distribution infrastructure, guided by progressive conversion of substations for each consumer, in order to ensure continuity of service.
  • Energy planning processes will allow the selection of suitable urban areas for the integration, extension and/or development of new ULT DH networks, with better cost/benefit scenarios.

The project will interact with an array of other EU funded projects focusing on developing sustainable heating and cooling solutions in Europe.


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A Flexible Approach to Deployment & Conversion of DH Net. to Low Temperature, with Increased Use of Solar Systems

District heating (DH) systems are key systems for the de-carbonization of heating energy in European Cities. In order to allow for this transition, while guaranteeing competitive energy costs, conversion of DHs is required. DH operation temperature needs to be reduced in order to increase the performance of renewable systems and operation criteria needs to be adopted for the introduction of weather-dependent, distributed heat sources such as solar systems.

Design of consumer thermal substations for the integration of distributed solar technologies in District Heating systems

Victor Sanchez and Roberto Garay, of Tecnalia, will present a new consumer substation on the 5th International Solar District Heating Conference.


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RELaTED innovative technologies for district heating systems

The concept of RELaTED is that where lower distribution temperatures are paired by a set of innovative technologies enabling for the rearrangement of DH networks into a collection of energy hubs, not only with local heat consumption, but also heat production, based on the following technologies:

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RELaTED demonstrations sites: Denmark, Estonia, Serbia and Spain

Considering the complexities and particularities of each district heating (DH), RELaTED concept is being implemented in four different DH networks covering extremely different climatic conditions, construction traditions, urban density, pre-existing district scheme, ownership and energy services contract schemes.

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