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Commercial Scale Solar Powered Desalination

Commercial Scale Solar-Powered Desalination (PDF)
 
Development of an innovative integration approach for Thermal Solar system Desalination facility to allow direct solar thermal energy use for distillation by evaporation.
 
The opportunity to revive direct thermal evaporation arises from the new generation of high-performance single axis tracking collectors developed by Solel Solar Systems.
The novel solar technology is coupled to the familiar Multi Effect Distillation (MED) process modified by IDE Technologies to match the solar steam characteristics.
 
Major Design Parameters:
  • Collectors type
  • Field size
  • Number of effects in the MED plant
 
Major Operational parameters:
 
  • Steam pressure and temperature at the turbine inlet.
  • Solar field steam supply temperature.
  • Hours of operation
  • Operation during the winter
 
The MED plant omits the phase of electricity generation by using the solar thermal energy directly for distillation by evaporation. The Reverse Osmosis (RO) process uses less energy than MED, but the direct use of thermal energy eliminates the losses of thermal to electric energy conversion which typically are about 2/3 ! This means that the proposed MED process might compete in the economic arena with RO process even if its energy consumption is three times larger.
 
CoGeneration by both power and water desalination would be the most cost-effective configuration. MED Plant capacity as low as 10,000m3/d already allows for water desalination at 75¢/m3, where power is needed as well. Superheating of the solar steam up to 475oC, further improves plant economy by increasing turbine efficiency and the ability to select commercially available turbogenerator system.
 
Advanced PCM storage increases the annual water production by almost 20% as compared to conservative sensible heat storage with appropriate cost reduction.
 
Another option valid for grid connected sites is to run the MED system overnight by vapor compression recycling, since electrical power is available and is very cheap during nighttime. For Eilat the water cost would drop down by 10% approximately, but the solar energy contribution would also drop down to 30%. This solar contribution is of the same scale as solar powered continuously operated RO plant, where about 27% solar contribution is achievable.
 
MED Plant produces distilled water at about 20 TDS. Blending this water with brackish water like in the town of Eilat, to get tap water at 500 - 700 TDS, would reduce water cost by approx. 10%.
 
Larger capacity 100,000m3/d plant could help the acute problem of water and power shortage in specific areas, for even lower water cost. A plenty of settlements along the Persian-Arab Gulf and North Africa, with quite comparable climatic conditions - have a very similar problem.
Solar-powered desalination is already feasible at a competitive cost.
The recent increase in fossil fuel cost only strengthens this conclusion.
Since the combination of water and power demand is common at many locations – this technology has large economic potential worldwide.

Contact us

Rotem Industrial Park, Mishor Yamin, D.N Arava 86800, ISRAEL
Tel: +972-8-6568300, Fax: +972-8-6554502, Email: meni@rotemi.co.il


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