Drinking with the Wind: Wind-Powered Seawater Desalination
by Michael Graham Richard, Gatineau, Canada on 03. 4.08
Turning seawater into fresh water using windmills is nothing new. In most of the commercially available systems, the windmill produces electricity that is stored in batteries. When water is required, a high-pressure pump is activated to remove salt from the water via reverse-osmosis. It works, but converting wind into electricity, storing it, and then converting it back into mechanical work means that a lot of energy is lost. Also, batteries are expensive.
Students at the Delft University of Technology (TU Delft) in The Netherlands are trying to improve the process by making it more elegant: In their version, the windmill drives the high-pressure pump directly and it is fresh water that is stored instead of electricity (much lower cost).
The chosen windmill is normally used for irrigation purposes. These windmills turn relatively slowly and are also very robust. On the basis of the windmill’s capacity at varying wind speeds, it is estimated that it will produce 5 to 10 [cubic meters] of fresh water per day
That would be enough drinking water for a small village of approximately 500 people.
The reservoir can contain enough water for 5 days in case there is no wind. There are three safeguards built in the system ("in the event of the installation running dry, a low number of revolutions or a high number of revolutions"). The interesting thing is that these safety features are mechanical in nature, so they can work without electricity. Very important in certain developing countries or during emergencies.
The first prototype has been built and is already working at a location near the A13 motorway near Delft. This prototype is to be dismantled and transported to Curaçao the first week of March. There the concept will be tested on seawater.
::Drinking with the Wind, via ::Dutch University Tests Windmill for Seawater Desalination
See also: ::Australia to Build Huge Desalination Plant, ::The Seawater Greenhouse: A Desalination / Agriculture Hybrid, ::Desalination: Now with Half the Energy, ::Border Region Looks to Desalination to Counter a Parched Rio Grande, ::Low Temp Desalination Technology From New Mexico Water Resources Research Institute
If they can get that much water from a small turbine, imagine how much they could get out of those giant 1.5-2 megawatt ones!
Sounds very promising.
2,650 gallons per day sounds like pretty good productivity. A lot depends on the quality and size of the membrane used for reverse osmosis, static pressure to encourage the transfer, and the quality of the water source.
Rather than using gravity, some electricity could be diverted to run an air compressor and use a pressurized tank mounted on or in the ground. A lot less tower to build in a hurricane zone...
What about the brine or reject that is generated? How do you maintain the membranes? Don't they need to be replaced? How are the membranes manufactured?