Significant advantages of using the proposed Solar Rankine system for RO desalination are:

• Use of market available components (expanders, heat exchangers, diaphragm pumps) widely applied in heating and cooling industry available at low cost implies lower investment cost compared to other solar thermal technologies.

• Ideal exploitation of low temperature energy sources. This concerns the efficient usage of thermal wastes of industries, diesel generators and geothermal energy fields as well as thermal energy coming from biomass or MSW.

• Mechanical work is driven directly to RO pumps so there is a direct efficiency gain from no transformation to electrical power.

• It can be easily standardised due to most of the system components are market available.

• Rankine cycle approaches the efficiency of Carnot cycle meaning maximum efficiency.

• Continuous and safe operation at low temperatures.

• The working fluid (HFC-134a) is not corrosive and environmentally friendly.

• Low maintenance cost since except the fact that most of the components are market available, they are characterized by long life time (e. g. expander >150000 hrs)

• Due to low O&M cost, simplicity in construction and reliable operation it fits perfectly for applications in isolated, not grid connected areas.

• Compared to PV-RO desalination system this system prevails in the following:

o Water storage is used instead of batteries (electrical energy storage) o It is environmentally friendly since no batteries are used (problems of old batteries disposal).

o The absence of batteries implies less maintenance (usually 5 years batteries’ replacement). This is critical for installations in isolated areas where the maintenance is the key factor for long life-time. o Since no electricity is produced, the system is safer for the end users. o No qualified staff is needed for O&M. o The fresh water cost is expected to be lower.

• Compared to thermal systems operating in the same temperature range the proposed one is characterised by a much higher efficiency and much less product water cost.

• Variable pressure working conditions in RO system, implies higher energy availability and higher efficiencies in the whole system, making it more flexible to the variability conditions of RES. (solar)

1. Acknowledgements

The system will be developed under the project COOP-507997, partially financed by European Commission.