District heating networks are growing increasingly complex as a result of feeding in renewable energy and the trend toward decentralization. In the AD Net Heat project, Fraunhofer researchers are simulating heat flows throughout the entire network, predicting load peaks and helping to plan new grids.
Municipal utilities and heating suppliers are to convert their district heating networks to CO2-free operation in the coming years. However, fluctuations in the pipeline network caused by the feed-in of renewable energies and increasing decentralization are making it difficult to control the networks efficiently.
Fraunhofer researchers have developed a simulation software tool called »AD Net Heat« that simulates and visualizes the heat flows in the network. »This allows us to make predictions about heat flows and demand at consumption points during live operation. Municipal utility companies and energy suppliers can use this data to observe and manage the network, with all its various dynamics, in real time. Peak loads at different times of day are also detected and balanced out early on«, explains Dr. Matthias Eimer from the Fraunhofer Institute for Industrial Mathematics ITWM. This makes the district heating network more stable overall, and daily operation becomes more efficient and economical.
The Fraunhofer researchers have developed a digital twin of the physical pipeline network. This incorporates basic data such as the topology of the network, the length and cross-section of the pipelines and the number and position of the feed-in points and consumption stations. Added to this are factors such as weather data, solar radiation and the typical consumption profile at certain times of the day and year. The actual or planned feed-in data, such as the flow temperature or feed-in power, are also specified. On this basis, AD Net Heat simulates the dynamics of the entire network, provides important parameters for points on the periphery of the network - the so-called bad points - and reports critical operating states. In addition, the control of the network can be optimized and fed back to the control station.
By directly modeling the physical processes, the digital twin requires a minimal number of sensors. These are only used to calibrate unknown parameters, such as the pipe properties, which no longer correspond to the original state due to ageing processes. Additional sensors can then be used to validate the simulation results
The digital twin offers several advantages for operators of heating networks and municipal utilities: In many cases, optimized operation makes it unnecessary to switch on energy sources that are currently very expensive due to fluctuations in electricity prices. In addition, the flow temperature, for example, can be lowered to reduce unnecessary energy losses - without jeopardizing the security of supply.
Major events in the city, such as a concert or trade fair, where large halls need to be supplied with heat, are also included in the operational planning. After entering the location of the customer and the estimated heat requirement, the software simulates the heat transport and returns its consumption forecasts.
The software solution also helps with planning and commissioning new grids. Once the topology of a network has been defined, including the feed-in points for fluctuating energy sources such as solar thermal energy and industrial waste heat, the software tool calculates the distribution of heat flows and the expected consumption. Planning offices run through a wide variety of scenarios, such as consumption at certain times of the day or year, the different positioning of generators or structural changes such as new traffic routes.
»Municipal utilities and district heating suppliers are thus taking a big step towards a climate-neutral and resource-saving heat supply. They also reduce their costs. On the one hand, the simulation in the digital twin allows the maximum use of renewable energy sources when they are available. Secondly, the heat demand forecasts are very accurate and reliable. This means that the cross-sections of the pipes can be designed slightly smaller, which saves material«, says Eimer.
The Fraunhofer researchers are currently working on making the user interface of »AD Net Heat« even simpler and clearer for users at heating suppliers and planning offices.
As the calculation core is basically designed for all network types, the simulation could also be used for energy networks such as electricity or gas in the future.
Fraunhofer Institute for Industrial Mathematics ITWM
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