Industrial Waste Heat Recovery Collaborations through 4 th generation District Heating: A Decision Support Tool

Large amounts of low-grade waste heat are discharged into the environment from industrial activities, with heat dissipation additionally requiring energy and water consumption. Beside a more efficient internal use of waste heat within industries, the external use of waste heat is an important factor in the energy transition. Fourth-generation district heating enables a full exploitation of the potentials for the external use of waste heat. Small-scale collaborations between and within industries have recently been identified as a promising opportunity for the external use of heat, but financial barriers, lack of technical know-how and risk perception have been found to hinder greenfield undertakings significantly. To enable a quick assessment of the economic feasibility and environmental impact of collaborations for excess heat use within industrial areas, a decision support tool (DST) is presented here. The system requires as input parameters the hourly availability profile of waste heat and the heat load profile of the user for two typical days in winter and summer as well as the corresponding temperature levels. A simulation procedure was developed using Visual Basic Application (VBA) in Microsoft Excel, which calculates district heat pipes diameter, head, and heat losses, and dimensions the heat storage and integration systems, as well as heat pumps if required. The outputs of the DST are represented by several possible scenarios with economic indicators useful to decide whether and how to start a collaboration between potential waste heat sources and users. As waste heat recovery also has an impact on energy consumption, carbon emissions, and water consumption, an insight into the water-energy-carbon nexus impact of new collaborations is provided by calculating corresponding footprint indicators. A case study of a microgrid for recovering waste heat from condensation units of the refrigerated warehouses of a logistics centre to heat nearby office buildings is presented as an example of application.