Thermodynamic Investigation of a Solar Energy Cogeneration Plant Using an Organic Rankine Cycle in Supercritical Conditions

In the present work, a novel Organic Rankine Cycle (ORC) configuration is used for a low-grade heat source cogeneration plant. An investigation is conducted accordingly into the simultaneous production of electricity and cold. The proposed configuration relies on concentrated solar power (as heat source) and ambient air (for cooling). Furthermore, two gas ejectors are added to the system in order to optimize the thermodynamic efficiency of the organic Rankine cycle. The results show that the thermodynamic and geometric parameters related to these ejectors have an important effect on the overall system performances. In order to account for the related environmental impact, the following working fluids are considered: HCFC-124, HFC-236fa, HFO-1234yf and HFO-1234ze. As shown by the numerical simulations, the fluid R1234yf presents the minimal heat consumption and therefore provides an optimal thermal efficiency for the ORC cycle (which is around 29%). However, the refrigerant R236fa displays the highest refrigeration performances with a performance coefficient reaching a value as high as 0.38.