Economic assessment of a two-stage solar organic Rankine cycle for reverse osmosis desalination

The current paper presents the economic evaluation of a two-stage Solar Organic Rankine Cycle (SORC) for using the mechanical energy produced during the thermodynamic process to drive a Reverse Osmosis (RO) desalination unit. The developed integrated system is briefly analysed and the specific fresh water cost, as well as the cost of energy is calculated. The economic assessment results are compared with those obtained from a low-temperature SORC-RO and two alternative variants of PhotoVoltaic RO (PV–RO) systems (with and without batteries). It is found that the critical fresh water cost for the system under consideration is 7.48 €/m3 of permeate water and the cost of energy equals to 2.74 €/kWh, when the water cost is slightly higher than the critical one (meaning 8 €/m3). These values are considered satisfactory enough, in comparison to the other autonomous desalination technologies. Additionally, the specific fresh water cost of the developed technology was calculated to be 6.85 €/m3, being very close to the values of the PV–RO systems. The variant of two-stage SORC significantly improves the efficiency and reduces the cost of the already developed prototype system (single-stage low-temperature SORC for RO desalination), because the specific cost is found to be much lower and taking into consideration its reliability, this technology can constitute an alternative desalination method competitive to the PV–RO on the basis of techno-economic feasibility.