Comments on: World’s first salt power plant opens tomorrow

By: thomas

thomas — Wed, 30 Nov 2011 17:07:20 +0000

@NamU: Heh ;-) One might think so, but luckily, no. No fresh water is actually spent during this process. The salt power plant pretty much just piggybacks on somewhere fresh water is flowing into salty water anyway. For example where a river runs into the ocean. The fresh water is then diverted into the power plant, salty ocean water is pumped from the ocean and they’re both combined through the osmotic process described above. The resulting product is water that has a salt level somewhere between the salty ocean water and the fresh water – and power, of course ;-) This somewhere-in-between water is then pumped back into either the river or the ocean, depending on which is closer.

By: NamU

NamU — Tue, 29 Nov 2011 22:52:06 +0000

Wouldn’t there be a depletion of the fresh water resource? Just wondering, but the overall plan sounds cool. Need to stop burning up fossil fuels.

By: thomas

thomas — Mon, 30 Nov 2009 16:00:35 +0000

@Bjørn Olsson: Thanks for commenting. At the moment, the profitability is certainly low at the plant Statkraft has opened. Then again, that particular plant isn’t intended as a commercially viable plant – it’s a prototype for further research.

As noted in my reply to kk above, the current main obstacle is membrane efficiency. Their best current membrane has an efficiency of 2-3 watts per square meter. They have to get that number up to 5 for the concept to be viable. They also have to improve the transfer of pressure to the turbine.

Only the future will tell if they’ll accomplish this, of course, but they seem reasonably optimistic about it. They have 2015 as the target year for a full scale commercial plant – and given the size, resources and experience of Statkraft, I trust them to not fling out overly optimistic promises.

But, as you write, who knows? :-)

By: Bjørn Olsson

Bjørn Olsson — Mon, 30 Nov 2009 15:45:17 +0000

You missed one disadvantage: lousy profitability. Very small chanse that it ever gets profitable. But who knows?

By: thomas

thomas — Tue, 24 Nov 2009 12:12:47 +0000

@kk: The technology is built modularly to scale well, so the minimum water flow required isn’t too bad. Once they build a full scale commercial plant, they’ll need one cubic meter of fresh water per second to generate 1 MW. This should make osmosis power plants feasible for even moderately sized rivers, although I suppose larger scale installations will be more cost effective, as is so often the case.

At the moment, improving the membrane efficiency is the stumbling block. The membranes Statkraft is running their protoype on generates less than 1 watt per square meter (keep in mind that the membranes are rolled up inside pressure vessels (see picture above), so this isn’t as space wasting as it sounds). They’ll switch to membranes with an efficiency of 2-3 watts per square meter after running the prototype for a while, with the future goal of getting to a 5 watts efficiency.

By: kk

kk — Tue, 24 Nov 2009 10:52:20 +0000

Osmotic power looks a very attractive renewable energy source. One disadvantage I could think of is the potential required. What flow of fresh water is needed to produce, let’s say, 1 kW of electricity?