Ultra-Low Temperature District Heating

Ultra-low temperature district heating networks are district heating networks that provide heating as well as cooling. For this purpose, temperatures in the range of only 0 °C - 25 °C are realized in the thermal network. Thus, the temperatures in ultra-low temperature heating networks are significantly lower than those used in conventional and existing networks (60 - 120 °C). The lower temperature level is not sufficient to provide heating and domestic hot water in the connected buildings. Therefore, decentralized heat pumps are used in the buildings. These use the thermal network as a heat source. Due to the constant and high source temperature, the heat pumps operate in a very efficient range. In summer, the network can be used directly for passive cooling with very low energy consumption. Usually at a central location, a heat source at the same temperature level as the network is used to transfer the extracted energy to the network. Geothermal energy (surface collectors or near-surface geothermal probes) is often used for this purpose, but sewage waste heat, data centers, waste heat from industrial processes at a low temperature level or other sources are possible. This is the great advantage of ultra-low temperature district heating networks since they use energy that otherwise could not be used and thus contribute directly to a sustainable heat supply.

At heatbeat we have successfully completed multiple projects with ultra-low temperature heating networks. Thus, we know what to pay attention to in the conceptual design and planning of ultra-low temperature heating networks. With our dynamic simulations, the heatbeat Digital Twin is capable to dynamically model all relevant components (supply - thermal network - building) and show the essential effects for the planning of ultra-low temperature heating networks. With dynamic simulations with at least hourly, in most cases even 15-minute time steps, we model the fluctuating and non-regulable temperatures and outputs of the heat source in our Digital Twin. This allows us already at an early stage to test and validate the optimal dimensioning, as well as possible modes of operation of the network. The individual demands of the buildings (space heating and domestic hot water, each with buffer storage) and the dynamic behavior of the decentralized heat pumps are taken into account, so that the simultaneity between supply and demand is realistically represented. We can also model different building types (e.g., new building or existing buildings) and consider the different temperature requirements in our simulations. Often uninsulated pipes are used in ultra-low temperature heating networks, which can save investments. Yet, the interaction of the uninsulated pipes with the ground can be used as another heat source. Thus, only dynamic simulations of the thermal network can make realistic assessments.

We use our simulation results not only to demonstrate the technical feasibility, to optimize and validate the dimensioning of the heat sources, the network and the substation, but also to make reliable statements about the operation and thus the economic efficiency and sustainability (primary energy factor and CO2 emissions) of these systems.

You can find more information in our showcases, where we have simulated an ultra-low temperature district heating network. By the way: ultra-low temperature district heating networks are funded, for example, via 'Wärmenetzsysteme 4.0' or via the new federal funding 'Bundesförderung für effiziente Wärmenetze' (BEW). Of course we are happy to give advise on this as well.