High temperature direct vapor generation organic Rankine cycle in the concentrated solar power application

A novel direct vapor generation solar thermal power system in the high-temperature application (>350oC) is proposed. The system mainly consists of a solar field, two-tank thermal storage, and cascade organic/steam Rankine cycle (ORC-SRC). Compared with the commercial concentrated solar power (CSP) plants using synthetic oil for heat carrier purpose only, the novel system employs the oil for heat collection, thermal storage and power conversion. The thermal oil is vaporized directly in the solar field. The outlet fluid can be either in liquid, binary phase, or vapor state, depending on the solar radiation. Vapor in the high-temperature tank flows into the ORC turbine and expands. The exhaust vapor is condensed, and the heat is released to the bottom SRC. The system tackles the challenges in the direct vapor generation technology: stable power conversion under fluctuating solar radiation and long-term reliable storage. The fundamentals of the system are illustrated. Mathematical models are built. Simulation is conducted by using Therminol® VP-1 as the fluid. The results indicate that the proposed system significantly increases the average temperature of the solar field owing to the fluid vaporization. Compared with a conventional CSP system using two-tank thermal storage, the proposed system has a higher power efficiency (42.01% vs. 37.93%). By optimizing the steam evaporation temperature of the bottom SRC, a further efficiency increment is expected with a large storage capacity. The direct vapor generation solar field of thermal oil can also be combined with a molten salt unit. Though two-tank oil storage is exemplified in the simulation, the increased efficiency and enlarged storage capacity are achievable when two-tank molten salt storage is employed     «

A novel direct vapor generation solar thermal power system in the high-temperature application (>350oC) is proposed. The system mainly consists of a solar field, two-tank thermal storage, and cascade organic/steam Rankine cycle (ORC-SRC). Compared with the commercial concentrated solar power (CSP) plants using synthetic oil for heat carrier purpose only, the novel system employs the oil for heat collection, thermal storage and power conversion. The thermal oil is vaporized directly in the solar...     »