Design and Operational Optimisation of a Combined Cooling, Heating and Power Plant to Enable Waste Heat Integration into an Existing District Heating Network

Abstract

The substitution of fossil fuels in current energy systems is essential on the path to carbon neutrality. In the building sector, different renewable and waste heat sources could be used in district heating systems to replace fossil-based heating plants. However, if new heat sources are integrated into multi-energy systems, the profitability of present heating plants could decrease. At the Forschungszentrum J ülich, the waste heat from a new high-performance computer is to be integrated into the local district heating system in order to reduce overall CO 2 emissions. This waste heat integration will have an impact on the holistic multi-energy system of the campus, which is mainly supplied by a combined cooling heat and power plant (CCHP). This paper investigates the described waste heat integration using a bi-objective optimisation approach. The proposed model optimises the operation of the overall multi-energy supply system with waste heat integration. Furthermore, the optimisation model allows for the optimal design of the required heat pump system and additional absorption chiller capacity that enable efficient CCHP heat usage despite the waste heat integration. In addition, the effects of lowering district heating temperatures and changed energy prices are studied. The results show that integrating waste heat reduces the overall CO 2 emissions of the multi-energy system and even more if the integration is combined with a lowering of district heating temperatures. Furthermore, the optimisation shows that a cost reduction is feasible by increasing the absorption chiller capacity that uses the produced heat of the CCHP.