Research Project UrbanTurn

The overall objective of the project is to develop and derive technical solutions for the necessary transformation of pipe-based heat supply, taking into account volatile pressures and temperatures when feeding in renewable energy sources. The solutions to be developed include, in particular, the development of new design criteria for system components and the development of innovative processes for the operation and control of heating networks. The sub-project of the Fh IEE aims in particular at the development and testing of technologies and control strategies for the efficient integration and use of decentralized, volatile heat sources in heating networks using simulation and test-based methods.

Background and general project objectives

District heating systems consist mainly of central heat generation plants with high thermal output, which provide the base load of heat demand in the supply area. To cover the medium and peak loads, additional heat generators are used as needed, some of which are distributed throughout the supply area (decentralized) and feed heat into the heat distribution network. In conjunction with the existing heat generation plants, the results of a thermo-hydraulic simulation, the requirements of existing special customers, and the weather forecast, demand planning and corresponding operational optimization of the district heating system are now carried out. The result of this approach is a highly efficient heat supply that is already significantly reducing CO₂ emissions in German cities with district heating.

Achieving the agreed climate targets at European and national level, and the resulting regional and municipal measures to implement the energy and heating transition, require the further development of these existing district heating systems. On the heat generation side, decarbonization, i.e., the transformation of district heating systems toward a higher share of renewable heat, will require not only the substitution of fossil fuels and the construction of renewable heat generation plants, but also the economic integration of decentralized heat potential (such as industrial waste heat or environmental heat). Heat pumps and, more generally, power-to-district heat plants can contribute to decarbonization in district heating systems while also coupling the electricity and heat sectors and storing energy from renewable sources. This must be supported by the modernization of existing buildings, which, in addition to reducing heat demand through building insulation, will lower district heating network temperatures through modernized heating systems and enable the development of renewable heat sources.

The starting point for the transformation of these existing systems, which have often developed over many years, is not only the heat demand of customers (or its future development) and the heat output of heat generation plants, but also the operating parameters of the heat distribution network (HDN). The operating parameters – temperature, pressure, mass flow – have so far generally been recorded digitally at heat generation plants (centralized/decentralized), at special network nodes, and at pressure boosting stations, and used to optimize the operation of the district heating system. The number of measuring points for recording operating parameters in the pipes of the heating network is low compared to the route length of corresponding systems.

Objectives of the “UrbanTurn” research project

The ongoing and future developments of existing district heating systems will contribute significantly to the exploitation of previously untapped efficiency potential through the installation and use of digital components. The overall objective of the “UrbanTurn” research project is to develop and derive technical solutions for pipe-based heat supply in order to exploit the potential offered by the digitalization and further development of district heating systems.

The partners in the BMWK-funded research project—the Fraunhofer Institute for Energy Economics and Energy System Technology IEE, BRUGG Rohrsysteme GmbH, Danfoss GmbH, GEF Ingenieur AG, HafenCity University Hamburg, and Ihr AGFW—will benefit from the “District LAB” test facility being built at Fraunhofer IEE in Kassel. As an essential component of the “District LAB,” a thermal test network consisting of underground pipes, connection stations, and storage and generation units enables the implementation and comprehensive analysis of various complex supply scenarios (see Figure 1). A comprehensive measurement and control system forms the basis for a complete evaluation of the hydraulic and thermal operating conditions. The measurement equipment installed in the underground pipes allows the effects of the operating conditions on the load on the pipes to be quantified and used for the further development of pipe-based heat supply.

In the course of the project, a digital twin of the “District LAB” will be created, which can be validated using the real test results and will thus enable computer-aided simulations of investigations in the future. Based on this, new operational management and control strategies for heating networks will be developed using simulations and experiments. The findings from these investigations can be used to derive and develop concrete proposals for the practical implementation of future district heating supply.

In addition, the project has the following sub-goals:

• Testing and developing new network components in conjunction with the test facility, taking into account characteristic overall system behavior;
• Quantification of the effects of volatile pressures and temperatures on the hydraulics and stresses of the heating network;
• Development and validation of measures for the transformation of existing district heating systems;
• Development of proposals for the revision of the technical regulations for district heating statics;
• Investigation and development of methods and instruments for the digitalization of district heating supply.