Investigation of Different Storage Systems for Solar-Driven Organic Rankine Cycle

The objective of the present work is the study of different thermal storage systems for a solar-fed organic Rankine cycle (ORC) system that operates with parabolic trough collectors. The conventional design with sensible thermal oil storage is compared with a storage configuration with thermal oil and ceramic rocks, as well as the use of latent storage with phase change materials (PCMs) is investigated. The initial system is studied parametrically, and it is properly designed to order for the cycle to have high performance. Different organic fluids are studied in the organic Rankine cycle and different rocks are investigated as storage materials. Toluene is found to be the best candidate in the cycle and ceramic rocks are found to be the best candidate energetically and financially. The final results proved that both the thermal oil–ceramic rocks and the PCM are better technologies than the simple sensible thermal oil storage. For the design with a 180 m2 collecting area and 8 m3 storage tank volume, the thermal oil–ceramic rocks design leads to 13.89% system efficiency and net present value (NPV) to 129.73 k€, the PCM storage to 13.97% and 128.66 k€, respectively, while the pure thermal oil case leads to 12.48% and 105.32 k€, respectively. Moreover, it is useful to state that when the collecting area is varied from 160 m2 to 200 m2 with the tank volume at 8 m3, the efficiency enhancement with ceramic rocks compared to pure oil ranges from 8.99% up to 12.39%, while the enhancement with PCM ranges from 7.96% to 13.26%. For the same conditions, the NPV is improved with ceramic rocks from 18.35% to 25.79%, while with PCM from 14.17% to 25.29%.