Performance investigation of concentrating solar collectors coupled with a transcritical organic Rankine cycle for power and seawater desalination co-generation

Abstract A co-generation system producing electricity and freshwater by a solar field driven supercritical organic Rankine cycle (SORC) coupled with a desalination unit is proposed. The proposed system can use parabolic trough solar collectors (among other options) to produce 700 kW thermal energy with temperatures up to 400 °C at peak conditions. Thermal energy is delivered to the SORC which uses hexamethyldisiloxane (MM) as the working organic fluid and could achieve cycle efficiency close to 21%. The SORC condensation process is undertaken by the feed seawater to reduce thermal pollution. Due to the elevated temperature of the preheated seawater, the RO unit specific energy consumption decreases. The proposed system has two modes of operation: (1) electricity only; and (2) water-electricity co-generation; based on variable incident solar radiation. This system can reduce the negative impact of intermittent solar energy without thermal energy storage by converting solar energy to desalinated water. The proposed system is ideal for small/medium applications of a few hundred kW, providing a solution to two important issues: fresh water scarcity and electricity, in an efficient way. However, its cost-effectiveness is left to be proved in a future study.

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