Following what Juncal and Mikel wrote about, I’m writing today about membranes used to obtain power from the Osmosis process. As both of my colleagues mentioned, the main restriction of the development of this new technology is the membranes that are used in it.
Because all in all, the idea is rather simple: fresh water mixes with sea water, elevating this last one’s pressure producing energy.
This article that I found, “Membrane processes in energy supply for an osmotic power plant”, talks widely about the membranes used in the Osmosis.
First of all, mention that the lifetime of a commercial membrane is of about seven to ten years, keeping in mind that it has to be maintained periodically.
The efficiency of the membranes depends mostly of two factors: the water permeability factor and the salt permeability factor. The key of the fabrication of membranes is to produce a membrane that has a high water permeability factor and a low salt permeability factor.
But it is also important for the inner structure of the membrane not to allow significant salt concentration to build up inside it.
There are mainly two types of membranes under investigation: Cellulose acetate membranes and Thin-film-composite membranes. The first one can achieve a power of 1’3 W/m^2 , whereas the second one has known to achieve around 3’5 W/m^2 . Although, I think it is important to keep in mind that the break-even point of the business is around 5W/m^2 .
Therefore, there is still a long way to go…
As a curious piece of data, did you know that to build a 1 MW plant, 200.000 square meters of membrane are needed?