AWT

District heating networks are an important element of the present, as well as the future of heat supply. To reduce heat losses and to increasingly integrate heat sources with a low temperature level, such as geothermal energy or industrial waste heat, it is necessary to reduce the flow temperature to 95 °C or even lower. This poses considerable challenges for operators as well as consumers who rely on a higher temperature supply flow of 120 °C. As stands, it follows either that these high-temperature consumers will be excluded from the district heating supply in the future or that the conversion of a conventional district heating network to 4th generation heating network will be prevented by these high-temperature consumers.

The aim of this research project is to efficiently provide the high temperature level of today's district heating networks for certain high-temperature consumers in a 4th generation heating network, despite the lowered supply temperature. The chosen approach is to equip the corresponding decentralized transfer station (house station) with an energy converter in order to increase the flow temperature for the high-temperature consumer according to demand.

The energy converters considered are an absorption heat transformer (AHT) and an absorption–compression heat pump (ACHP); low power requirements characterize both compared to a compression heat pump.

Within the scope of the research project, an AHT at IGTE and an ACHP at IfT of the University of Hannover will be investigated numerically and experimentally on a pilot plant scale. The test plants will be optimized for operation in a district heating transfer station with regard to efficiency, operational safety and costs. In addition, the FFI will numerically analyze the effects on the district heating network and the cost saving potentials by lowering the flow temperature. The costs incurred for supplying heat to high-temperature consumers using an AHT or an ACHP are determined as a function of heat, electricity, gas and CO2 prices. In this way, the technologies are compared with each other and with conventional solutions regarding economic efficiency.

• Creation of a simulation model of the AHT - Calculation of plant characteristic diagrams
• Design of heat exchangers and pumps based on simulations
• Construction of an AHT as well as the required ancillary and measurement equipment
• Commissioning of the AHT and development of a control system
• Demonstrate the operation of the house station with integrated AHT by emulating real consumer operation states/points and possible states in which the network might operate in the future.

April 2022 – December 2024

Fernwärme-Forschungsinstitut e. V. (District Heating Research Institute)

Institut für Thermodynamik, Leibniz Universität Hannover (Institute for Thermodynamics, Leibniz University Hannover)

This research project is supported by the German federal Ministry for Economic Affairs and Climate Action (project number: 22424 N).