Techno-economic feasibility study of the integration of a commercial small-scale ORC in a real case study

The ORC certainly represents a promising solution for recovering low-grade waste heat in industries. However, the efficiency of commercial small-scale ORC solutions is still too low in comparison with the high initial costs of the machine and the lack of simulation models specifically developed for commercial ORC systems prevents industries from defining an accurate business model to correctly evaluate the ORC integration in real industrial processes. This paper presents a techno-economic feasibility analysis of the integration of a small-scale commercial ORC in a real case study, represented by a highly-efficient industrial distillery. The integration is aimed at maximizing the electricity auto-production by exploiting the heat produced by an internal combustion engine, already partially recovered in internal thermal processes. To analyze the influence of the ORC integration on the industrial processes, a semi-empirical steadystate model of the commercial small scale ORC was created. The model made it possible to simulate the performance of the commercial ORC within a hypothetical scenario involving the use of the heat from the cooling water and from the exhaust gases of the internal combustion engine. A detailed thermo-dynamic analysis has been carried out to study the effects of the ORC integration on the plant’s energy system with particular focus on the two processes directly affected by ORC integration, namely vapor production and the drying process of the grape marc. The analysis highlighted the great importance in the business model of considering not only the direct costs (unit costs, engineering, etc.), but mainly the indirect ones and hence the need of an appropriate business model, based on the simulation of the commercial ORC behavior, to evaluate its introduction in real industrial processes. In particular, in the specific case of a highly-efficient distillery plant, the ORC integration resulted to cause an increase in inner fuel consumption, represented by dried grape marc, with a consequent economic loss not offset by a significant increase in electricity auto-production. As a consequence, the ORC integration was not economically feasible in the considered case study due to the great value in the market of the dried grape marc.