District heating systems offer the possibility of lowering emissions and support the goal of reaching a carbon-neutral energy system by integrating renewable heat sources. Therefore, this work provided a systematic literature review to identify potential research gaps and show the literature distribution over the relevant topics. The focus is on the design optimization with (non-)linear programming of district heating systems in the context of decarbonization. Furthermore, crucial energy balance equations were extracted from the literature for a potential optimization problem. The systematic literature review limited its search to two databases, 10 years timespan, a quality measure, and uses keywords regarding topic and method. Categories were derived based on the subject and literature to cluster the found publications and identify potential research gaps. The results showed potential research gaps in the depiction of different stakeholder decisions, reduction of computational efforts, and their resulting uncertainties. Additionally, they identified gaps in the integration of low-grade heat sources, thermal storage facilities, and energy converters, especially geothermal energy, large-scale heat pumps, and seasonal storages.
Germany has become one of the leading players in the transformation of the electricity sector, now having up to 42% of electricity coming from renewable sources. However, the transformation of the heating sector is still in its infancy, and especially the provision of industrial process heating is highly dependent on unsustainable fuels. One of the most promising heating technologies for renewable energies is power-to-heat, especially heat pump technology, as it can use renewable electricity to generate heat efficiently. This research explores the economic and technical boundary conditions regarding the integration of heat pumps into existing industrial thermohydraulic heating and cooling networks. To calculate the optimum design and control of heat pumps, a mixed-integer linear programming model (MILP) is developed. The model seeks the most cost-efficient configuration of heat pumps and stratified thermal storage tanks. Additionally, it optimizes the operation of all energy converters and stratified thermal storage tanks to meet a specified heating and cooling demand over one year. The objective function is modeled after the net present value (NPV) method and considers capital expenditures (costs for heat pumps and stratified thermal storage tanks) and operational expenditures (electricity costs and costs for conventional heating and cooling). The comparison of the results via a simulation model reveals an accuracy of more than 90%.
Industrielle Kälte- und Wärmeversorgungssysteme haben mit 75 % einen erheblichen Anteil am Gesamtenergiebedarf der deutschen Industrie. Der zunehmende Anteil erneuerbarer volatiler Energien führt dazu, dass die Energieflexibilität der Anlagen an Bedeutung gewinnt. Mit „Easer“ wird in diesem Beitrag das Konzept eines webbasierten Planungswerkzeugs vorgestellt, das die Energieeffizienz und Energieflexibilität im Sinne eines ganzheitlichen Demand Side Management berücksichtigt.
Industrial refrigeration and heat supply systems account for a substantial 75 % of the total energy demand of German industry. The increasing share of renewable, volatile energies means that the energy flexibility of the plants is gaining in importance. With Easer, this article presents the concept of a web-based planning tool that takes energy efficiency and energy flexibility into account in the sense of holistic demand side management.
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