Combining a dynamic simulation tool and a multi-criteria decision aiding algorithm for improving existing District Heating

Abstract The work aims to evaluate the recovering potential of excess heat in the return pipe of a district heating (DH) for heating some substations. The proposed method combines a DH simulation tool and a multi-criteria decision aiding algorithm. It is based on the analysis of the measured return temperatures at each sub-station in order to identify those with high potential of efficiency gains by using the return flow (with support of the supply pipe when needed). Combinations of substations from this set of eligible ones define potential scenarios of connection to the return pipe. The impacts of each scenario on the DH operational performance and the energy savings are evaluated with a detailed hydro-thermal model. The technical parameters and the energy efficiency are not the only points of view in the selection process “of best compromise” scenarios for the improvement of the DH, so that we propose a complex decision aiding process, involving multiple criteria, dealing with different points of view (economic, energy, technical…) and different decision makers. The evaluations of the scenarios on the criteria are summed up in a so-called performance table and aggregated by an outranking model (MR-Sort) to identify relevant scenarios. This methodology is illustrated by the example of a part of the DH in Nantes (France). Interpretation of data from substations of a specific branch showed the potential of connecting some of them to the return pipe. Six scenarios were generated and evaluated with four criteria. Then, the Multi-criteria Decision Aiding method associated to two actors who have different priorities lead to not obvious results at a first glance.