Thermal and Exergetic Performance Assessment of an ORC Coupled with Thermal Energy Storage Using Thermal Oils for Low-Grade Heat Recovery

The transition towards sustainable energy systems demands efficient utilization of low- and medium-temperature thermal sources, which offer a promising alternative to pollutant energy carriers like fossil fuels. Among these, solar thermal, geothermal, and residual heat emerge as leading candidates for clean energy generation. Organic Rankine Cycles (ORCs) stand out as robust technologies capable of converting these thermal sources into electricity with high efficiency. A critical factor in ORC performance lies in the effective transfer of heat from the thermal source to the working fluid. This study systematically evaluates various thermal oils as intermediate heat transfer media, aiming to optimize their selection based on key performance indicators. The analysis focuses on thermal and exergetic efficiencies, alongside mass and volumetric flow rates of both the working fluid and the thermal oil. The findings reveal that the integration of thermal oils notably boosts the exergetic efficiency of the ORC system, underscoring their pivotal role in maximizing energy conversion from sustainable heat sources.