Feasibility limits of using low-grade industrial waste heat in symbiotic district heating and cooling networks

Abstract: Low-grade waste heat is an underutilized resource in process industries, which may consider investing in urban symbiosis projects that provide heating and cooling to proximal urban areas through district energy networks. A long distance between industrial areas and residential users is a barrier to the feasibility of such projects, given the high capital intensity of infrastructure, and alternative uses of waste heat, such as power generation, may be more profitable, in spite of limited efficiency. This paper introduces a parametric approach to explore the economic feasibility limits of waste heat-based district heating and cooling (DHC) of remote residential buildings depending on network extension. A parametric model for the comparative water–energy–carbon nexus analysis of waste heat-based DHC and Organic Rankine Cycles is also introduced, and applied to an Italian and to an Austrian setting. The results show that, for a generic 4 MW industrial waste heat flow steadily available at 95 °C, district heating and cooling is the best option from an energy–carbon perspective in both countries. Power generation is the best option in terms of water footprint in most scenarios, and is economically preferable to DHC in Italy. Maximum DHC feasibility threshold distances are in line with literature, and may reach up to 30 km for waste heat flows of 30 MW in Austria. However, preferability threshold distances, above which waste heat-to-power outperforms DHC from an economic viewpoint, are shorter, in the order of 20 km in Austria and 10 km in Italy for 30 MW waste heat flows. Graphic abstract: [Figure not available: see fulltext.].