Considering that reverse osmosis is not the only way to desalinate water, I think that yes, there is a lot of development potential in desalination, but that potential might not lie in improvements to existing techniques.
To justify this conclusion and illustrate some areas where there could be a lot of development potential, I present to you my idea for a combined wave, wind, and solar desalination and power plant. I haven't done any maths on this to calculate the area of land needed, or costs, or output, so it might not be viable as-is. But I think the concepts described below (and remember this is just one idea) demonstrate that there is development potential in the following areas:
- Using renewable energy sources on-site to power the plant
- Using direct-drive energy instead of electrically transmitted energy
- Directing and amplifying natural processes of desalination
Combined wave, wind, and solar desalination and power plant
- No external energy input
- Cleverly harnessed wave, wind, and solar
- Energy (electricity)
- Fresh water
- Cool air
This plant requires a hot location with large area of cheap land by the ocean and a relatively consistent wind.
Stage 1 - Wave Pump
A wave-powered pump raises sea water into a large lake on land. Here is an example of a direct wave-powered pump, other types of wave power harnessing typically convert mechanical motion into electricity. However, that motion can be easily used to directly drive a pump.
Stage 2 - Evaporation Lake
The evaporation lake is a large shallow area, covered in a greenhouse-like way to aid evaporation. The sea-water flows away from the ocean along channels in the lake-bed then back again towards the ocean in the next adjacent channel where it drains back into the sea. This prevents the build-up of deposits as the returning sea-water will take them with it and return to the sea more concentrated. The roof may contain Fresnel lenses or other solar concentrators to help evaporation.
A wind-catching tower blows air across the lake to lower air pressure and aid in evaporation. This tower could be like those used in Masdar City, or a standard wind turbine tower with either electrical or direct transmission to a series of fans. The result is a continuous airflow across the lake which carries the water vapor to the far side where it is channeled up a wide column into the next stage.
Stage 3 - Condensing Tower
The water vapor is channeled up a large column to a condensing chamber high on the tower. Here, a series of fins are cooled by a heat-pump driven directly by a wind-turbine on top of the tower. the water condenses on the fins and drains into a fresh-water tank near the top of the tower.
Stage 4 - Power Generation
The water from the condensing tower is lowered to a height suitable for a standard water-tower through one or more water turbines to generate power.
Stage 5 - Filtering and treatment
The salty sea-air will also condense on the fins, and there may be small airborne particles and particles from wear on stages within this process that get into the water, so it will probably need further filtering and treatment to make it drinkable. Some of the power from the water turbine may be used for this.
There you have it, you have clean water, above ground level so pressure is already available, and hopefully some excess electricity and cool dry air as by-products.