Thermo-economic optimization of small-scale Organic Rankine Cycle: A case study for low-grade industrial waste heat recovery

Abstract This work is focused on a case study of a small-scale Organic Rankine Cycle (ORC) adopted for electricity production from low-grade industrial waste heat recovery. This kind of applications raises a great interest due to the high amount of low-grade waste heat recoverable within industrial processes, but lacks of in-depth experimental investigations on the topic. The main reason is the difficulty to reach profitable small-scale projects, so more cost-effective solutions are being explored in the literature through thermo-economic optimizations. Nonetheless, the results obtained cannot be discussed with respect to actual operating data. In light of this, this paper proposes to conduct the thermo-economic optimization on the basis of an experimental application. In this manner, a comprehensive model of the facility is developed, calibrated, and validated from actual operating data. The model is used to conduct the thermo-economic optimization, revealing the influence of the organic fluid, cycle architecture, geometric parameters of main components, or control strategy used to obtain the best cost-effective solution. The main results show that, by means of a multivariable optimization using cost-effective ratios as objective function, a cheaper and powerful solution adapted to each specific project may be designed.