Work Package 1

District Heat Grids and Components

This WP focuses on the research, development and evaluation of low-temperature district heating systems based on renewable energy. The research basically provides new knowledge of the hardware and software technologies of the new generation of district heating systems supplying heat to existing energy renovated buildings and new low-energy buildings.

The hypothesis is that low-temperature district heating, with a general supply and return temperature of 50°C and 20°C, can be used in existing district heating systems, if minor modifications are implemented in the systems for room heating and domestic hot water supply of the existing buildings. The immediate implementation of the low-temperature technology (10 years) in existing and new district heating systems and buildings makes it possible to use low-temperature renewable heat from geothermal plants and central solar heating plants as well as waste heat from industrial processes directly and thereby replace fossil fuels and imported biomass in the district heating systems.

The results of WP1 are used in the other WPs to identify the overall optimal way of realising the energy system without the use of fossil fuels. The WP includes the following sub-projects:


WP 1.1. Heating of existing buildings by low-temperature district heating

We assume that it is possible to heat all types of existing buildings with a hydronic heating system by use of low-temperature district heating with a supply temperature of 50°C, except for short periods with very cold weather when a higher temperature is supplied. By use of detailed simulation calculations of the typical buildings, the realistic dynamic heating load is calculated and compared to the heating power of the existing heating elements with a low supply temperature. The conversion of the heating system to low-temperature operation should be the first step of a specific plan for a thorough energy renovation of the typical buildings.   

WP 1.2. Supply of domestic hot water at comfort temperatures without Legionella

We assume that it is possible to change the operation of existing domestic hot water systems (DHW) in all types of buildings to a comfort temperature of 40°C without risk of Legionella. Two types of solutions are investigated: (1) Local production of DHW in highly efficient compact heat exchangers with a very small volume of DHW in the pipes to the tap; and (2) UV sterilisation of the water entering and circulating in the DHW system of buildings with a circulation loop for DHW supply.

WP 1.3. Conversion of existing district heating grids to low-temperature operation and extension to new areas of buildings

Here, we assume that it is possible to convert/extend the existing district heating (DH) grid to the low-temperature DH concept with typical supply/return temperatures of 50/20°C to the areas with low-energy demand buildings. Thereby, it becomes possible to supply renewable heat to new and renovated buildings in city areas at a competitive price compared to alternative decentralised renewable energy supply systems. This project’s focus is on the extension of district heating grids to areas where the existing buildings will be energy renovated over the next decades or newly built areas with low-energy demand buildings.

WP 1.4 Minimising losses in the DH distribution grid

The losses in DH grids are a major obstacle to the utilisation of renewable heat sources and waste heat. A significant reduction in the distribution heat losses is gained by the introduction of low-temperature DH. The hypothesis of this sub-project is that it is possible to develop and utilise technical solutions by which the total thermal, temperature and electrical losses in DH distribution systems can be further reduced.

Modelling and simulation of the total distribution grid, including modelling of the individual components, are carried out. The model is able to identify and eliminate potential component sub-optimisation and point out other potential critical focus areas in the DH grid. The project includes a review of innovative designs and concepts of distribution pipes and other components.



Funded by


InnovationFundDenmark logo 2014