Wave Powered Desalination

1. Wave Powered Desalination Stephen Salter, Joao Cruz, Jorge Lucas, Remy Pascal. School of Engineering University of Edinburgh

2. Desalination Techniques: Multi-stage Flash. Has to be big. Good for using waste heat. 1960s. Reverse Osmosis. Large or small. Electricity or Diesel. High, steady pressure. Vapour compression. Low pressure. High volume. High purity. Variable pressure.

3. The basic element of the vapour compression desalination system

4. Trickle sea water down one side of a heat transfer surface

5. Suck away a little of the vapour and pump to the other side where it condenses on the newly cooled surface to re-circulate the latent heat

6. Re-circulate the salt side until salinity reaches about 7%. Remove the fresh. product

7. But …. = 0.77 kWh/m3

8. ΔT really matters 2.5 kWh/m3 to 10 kWh/m3 Straddles reverse osmosis.

10. Falling film heat transfer coefficient 3000 watt/m2 K Maxwell Davidson Carbon filled PVDF on expanded metal gives non-fouling surface with very long life.

11. 6000 square metres Heat transfer area

12. Suspend U-sheets from hangers

13. Seal edges of U-sheets with inflated bags. Cost slightly only slightly more than raw material.

19. Brine recirculation

23. Recover the heat from the double strength brine and fresh product by warming the incoming feed.

24. Two months !