Supercritical Carbon Dioxide Cycles for Concentrated Solar Power Plants: A Possible Alternative for Solar Desalination

Abstract

This manuscript investigates the supercritical carbon dioxide (sCO2) power cycle employed in the power block of concentrated solar power (CSP) plants—solar tower—as an alternative for solar desalination, developed with either distillation or reverse osmosis. This concept is investigated as a possible up-scaling of the SOLMIDEFF project, originally based on a hot-air micro gas turbine combined with a solar dish collector. For the upscaled concept, five different sCO2 cycles are considered, chosen amongst the best-performing configurations proposed in the literature for CSP applications, and modelled with Thermoflex software. The influence of ambient conditions is studied, considering two minimum cycle temperatures (35 °C and 50 °C), corresponding to Santa Cruz de Tenerife and Abu Dhabi, respectively. The results show that the low temperatures at the inlet of the heat rejection unit compromise the viability of distillation technologies. On the other hand, the high thermal efficiency achieved by these cycles, especially with the recompression and partial cooling layouts, reduces the specific energy consumption when combined with reverse osmosis (RO), below that of photovoltaic (PV)+RO. Feed-water preheating is explored as a solution to further reduce energy consumption, concluding that its actual interest is not clear and strongly depends on the location considered and the corresponding water quality standards.

Innovative desalination system driven by a solar micro gas turbine for off-grid applications

“…Further to the aforecited potential of micro gas turbines for decentralised power, in particular applied to renewable energy sources, and based on the past experience of the authors, a solar desalination system based on SmGTs with the techno-economic features already presented in [13][14][15] seems to be a cost-effective solution with a promising future against other popular renewable desalination options integrating PV panels. This has already been explored for isolated units [16] but, according to recent literature on the topic, it might also apply to larger scales by coupling several SmGTs in parallel.…”

“…Given the inlet conditions and mass flow rates at both sides of the recuperator, the outlet conditions can be calculated with Eqs. (13)(14)(15), where the rules to scale the rated value of conductance and to compensate for the variations of thermodynamic 13 properties throughout the recuperator have been validated experimentally by the authors in [49], for fluids with both ideal and non-ideal gas behaviour.…”