SELECTION OF SUITABLE WORKING FLUID AND STORAGE MATERIAL FOR ORC COUPLED WITH THERMAL ENERGY STORAGE

Abstract

Some low-temperature energy sources (e.g., waste or solar heat) tend to be intermittent, and the heat supply from such sources may fluctuate over time. This kind of heat could be utilized using organic Rankine cycle (ORC) to generate electricity. Moreover, the increase in their reliability may be possible thanks to the application of thermal energy storage (TES), in which surplus thermal energy may be accumulated in the storage material. This energy can then be used in these periods of time when the heat source is not available or its output is limited. In this way, energy generation may be levelled. In some cases, a wide range of operating conditions and a variety of working fluids that are used in ORC systems mean that the choice of TES material may be difficult, since there are several types of TES materials, and each analysed case can give different material selections. Because of that, optimizing TES that is connected to the ORC system can be an interesting scientific challenge. Therefore, the aim of this study is to present the selection of proper working fluid-TES material pairs for different working conditions applied to a model of the ORC system coupled with TES. Various configurations of the ORC-TES system were investigated, taking into account differences between latent and sensible TES, and both for simple and recuperated cycles. The results obtained show that the combination of ORC with TES is promising for application in intermittent and fluctuating heat sources.