The planning tool for district energy systems

Scientific contributions

On this page you find an overview of research activities that have gone into the development of computational methods for the nPro tool in the area of artificial intelligence and mathematical optimization.

5th generation district heating and cooling

nPro is the first tool specifically developed for the planning of 5th generation district heating and cooling networks (5GDHC) (also called anergy networks). In the field of 5GDHC networks, several publications have been published by the nPro development team in scientific journals. In the publication titled 5th Generation District Heating: A novel design approach based on mathematical optimization, the first mathematical design optimization model for 5th generation district heating networks was presented. The model represents the entire district with all buildings in a holistic model and selects and sizes the optimal system configuration in the energy hub as well as in the buildings in a single calculation step. The method mathematical optimization is also used in nPro in the energy hub module for the design optimization.

In another publication entitled Quantifying Demand Balancing in Bidirectional Low Temperature Networks, methods for quantifying the balancing of heating and cooling demands in 5GDCH districts are presented. In 5GDHC networks, waste heat from buildings that is fed into the network can be used to heat other buildings. In this case, the decentralized heat pumps in the buildings use the waste heat as a heat source and thus provide space heating or domestic hot water. The publication introduces a so-called Demand Overlap Coefficient (DOC), which describes the share of heating and cooling demands that can be balanced between the buildings by the 5GDHC network. The design metrics presented in the paper are also calculated and visualized in the nPro tool.

In the publication Temperature control in 5th generation district heating and cooling networks: An MILP-based operation optimization, an optimization model for the operation optimization of 5GDHC networks was developed. The special feature of the model is that it also optimizes the network temperatures and thus maximizes the coefficients of performance (COPs) of the heat pumps and minimizes the power consumption of the overall system.

Design optimization for energy hubs

nPro uses a novel calculation method for planning hybrid multi-energy systems. The calculation method developed specifically for nPro is used in the module energy hub of the nPro tool. It is based on a publication entitled Design optimization of multi-energy systems using mixed-integer linear programming: Which model complexity and level of detail is sufficient?, which appeared in the scientific journal Energy Conversion and Management in 2021. The publication examines what level of detail is necessary for mathematical optimization models for the design of energy hubs. It represents an important preliminary work for the development of nPro: although nPro is based on detailed calculation methods, it always takes into account that in an early planning phase only a few boundary conditions for a district are known and therefore all calculation approaches comprise the smallest possible number of input parameters. It is therefore not very useful to use simulation models that require thousands of input parameters if only a fraction of these parameters are known at all and ultimately almost all parameters are based on assumptions. For this reason, nPro uses calculation methods that are physically exact, but can represent certain physical effects with only a few parameters. Thus, nPro follows the among engineers well-known maxim: Not as exact as possible, but as exact as necessary!

Academic planning tools for hybrid energy systems

In 2020, the EHDO web tool was developed at the Institute for Energy Efficient Buildings and Indoor Climate at RWTH Aachen University. The tool uses a simplified calculation model based on mathematical optimization to optimize the design of energy hub. A scientific publication entitled EHDO: A free and open-source webtool for designing and optimizing multi-energy systems based on MILP was published. Today, EHDO is used in the course Alternative Energy Technologies at RWTH Aachen University to support students to gain first experiences in designing complex energy systems.

References

  1. 5th Generation District Heating: A novel design approach based on mathematical optimization. M. Wirtz, L. Kivilip, P. Remmen, D. Müller. Applied Energy, 260, 114158, 2020.
  2. Quantifying Demand Balancing in Bidirectional Low Temperature Networks. M. Wirtz, L. Kivilip, P. Remmen, D. Müller. Energy and Buildings, 224, 110245, 2020.
  3. Temperature control in 5th generation district heating and cooling networks: An MILP-based operation optimization. M. Wirtz, L. Neumaier, P. Remmen, D. Müller. Applied Energy, 288, 116608, 2021.
  4. Design optimization of multi-energy systems using mixed-integer linear programming: Which model complexity and level of detail is sufficient? M. Wirtz, M. Hahn, T. Schreiber, D. Müller. Energy Conversion and Management, 240, 114249, 2021.
  5. EHDO: A free and open-source webtool for designing and optimizing multi-energy systems based on MILP. M. Wirtz, P. Remmen, D. Müller. Computer Applications in Engineering Education, 2020. DOI: 10.1002/cae.22352

nPro Webtool

Plan and optimize district energy systems with nPro