osmotic power renewable energy

The concept of osmotic power is nothing new but there have been some recent incremental progress in its technological development;

http://phys.org/news/2016-07-electricity-salt-three-atoms-thick-membrane.html

in river estuaries it has the potential of giving continuous electric power close-enough unaffected by the weather.

Although I think we should definitely develop and use osmotic power, personally I am far more excited by the potential for marine current power (see https://en.wikipedia.org/wiki/Marine_current_power ) .

The funny part being that half the world wants to do the exact opposite: take water out of the sea using power and osmosis.
Maybe we can even have a plant with solar panels that works like a battery, making clean water during the day and electricity at night.

Also of interest is the fact that living cells use membranes and differing ion concentrations as part of their main power source.

I too like the idea of ocean current power, but I believe working in sea water has proved difficult.
The fact is that solar and wind are now cheaper than coal, and the real problem is not availability of renewable technology, but a need to change the politics of power.
Until wind and solar are at least producing 100% of the power requirements at their peak production times, we don't need to even worry about power storage or alternatives that are always on, we just need to build more wind and solar.
Here in SA they are still considering nuclear power - almost certainly for political reasons not economic ones.

Originally posted by twhitehead
...
Maybe we can even have a plant with solar panels that works like a battery, making clean water during the day and electricity at night.

I think that's an idea worth exploring. The main obvious economic barrier for that would be the possibly high cost of making huge water storage tanks/reservoirs especially for that as they would need to be huge because the energy density of this type of storage would be rather low. Still, I can easily believe that in some places it might be possible to make it cheaper than the alternative of using conventional batteries esp where there just happens to already be a suitable natural/man made reservoir in about the right place for the job thus saving the cost of making one from scratch.

Actually, you could use an already existing water reservoir even if it is well above sea level as follows;
Use electric energy to distill sea water into fresh water at sea level. Then use more electric energy to pump it all the way up to the reservoir. Then later, using the same pipe, extract hydroelectric power that brings it back to sea level again and then use osmotic power to extract more energy from the mixing with sea water.
Thus, in this scheme, you store the energy partly in chemical form and partly in potential energy form. This could be a tactic of maximizing the amount of energy you can store while minimizing on the potentially prohibitive initial set-up cost as it doesn't involve making new expensive reservoirs.

The article mentions a potential output of 1MW per m2. It doesn't say how much water is required.
The whole setup would require fresh water flowing across the membrane and into the sea. I wonder if this can be arranged without any use of power to move the water. Also would the water need to be filtered before entering the plant?
How is the sea water brought into the plant?

Originally posted by twhitehead
...would the water need to be filtered before entering the plant?

I would think so because the membrane used for osmosis will be very delicate! For example, a fish getting into it and wiggling around would result in it tearing. However, I don't see that as a problem because I would imagine simply pre-filtering the water with a very fine but robust net should do the job just fine.

Originally posted by humy
I would think so because the membrane used for osmosis will be very delicate! For example, a fish getting into it and wiggling around would result in it tearing. However, I don't see that as a problem because I would imagine simply pre-filtering the water with a very fine but robust net should do the job just fine.

My concern is how much power is needed to move all the water around vs how much power the plant makes.

Not exactly the same method, but also using osmosis, an actual power plant:
https://www.newscientist.com/article/dn18204-first-osmosis-power-plant-goes-on-stream-in-norway/
Makes enough power to run a couple of kettles 🙂

That was 2009. Wikipedia says it was supposed to do much better by 2015 but I have not found any confirmation that it succeeded.

Originally posted by humy
The concept of osmotic power is nothing new but there have been some recent incremental progress in its technological development;

http://phys.org/news/2016-07-electricity-salt-three-atoms-thick-membrane.html

in river estuaries it has the potential of giving continuous electric power close-enough unaffected by the weather.

Although I think we should ...[text shortened]... e potential for marine current power (see https://en.wikipedia.org/wiki/Marine_current_power ) .

It says '' 1 m^2 covered with 30% of this membrane could generate 1 megawatt of energy''.

I gather m is not meters? maybe one square mile? They didn't say the units which is really frustrating.

Originally posted by sonhouse
It says '' 1 m^2 covered with 30% of this membrane could generate 1 megawatt of energy''.

I gather m is not meters? maybe one square mile? They didn't say the units which is really frustrating.

Only America and Myanmar don't use the metric system. The did say the units. 'm' stands for metres. Although the scientists in question are in the US, they wouldn't have been talking about square miles.
Its funny how they measure the output in 'energy saving lightbulbs'. For a start, the only reason for doing that is to try and inflate the figures, but the fact is that energy saving lightbulbs come in all sorts of different types with significantly different power requirements. Are they talking about florescents, or LED? Are they talking about 100W equivalents or 40W equivalents? I have bulbs that take anything from 3.5W to 20W

There is a video on the page which is a bit clearer.
They did the experiment with only one nanopore and calculated potential output from there. I strongly suspect that it would not scale up anywhere close to the calculated maximum potential. Lets wait till they have done it with a membrane filled with pores.

Originally posted by twhitehead
...
Its funny how they measure the output in 'energy saving lightbulbs'. ...

Yes, I to suspected that was a comment with rather corrupt motive.
I think the link is badly blemished by that comment even though I am sure osmotic power is perfectly feasible and good and the research they have done is good. The link really could have done without that unfortunate and worse-than unnecessary comment and they really should have left that comment out; bad of them.

Originally posted by twhitehead
Only America and Myanmar don't use the metric system. The did say the units. 'm' stands for metres. Although the scientists in question are in the US, they wouldn't have been talking about square miles.
Its funny how they measure the output in 'energy saving lightbulbs'. For a start, the only reason for doing that is to try and inflate the figures, but t ...[text shortened]... king about 100W equivalents or 40W equivalents? I have bulbs that take anything from 3.5W to 20W

I think it impossible to get megawatts from one square meter of most anything not nuclear. It would certainly not be 100% efficient, say it was 50% efficient then it seems it would have to also get rid of a half megawatt of heat. Just not gonna happen. It may be they missed an order of magnitude or three. Maybe they missed putting in Km. 1000 meters by 1000 meters would make it more likely. That would clock in at ONE watt per meter squared not 1,000,000. That latter is ridiculous.

Originally posted by sonhouse
Maybe they missed putting in Km.

No, the video clearly shows 1metre x 1metre.

I don't think inefficiency would result in heat, that's not the kind of inefficiency that would occur.

You may also find this interesting:
https://en.wikipedia.org/wiki/Reversed_electrodialysis

More important than the area of membrane is the amount of water required. My guess is the experimenters didn't think of that at all. You simply cannot get the volume of water required in close proximity to a 1m^2 membrane. The Wikipedia page talks of 1m^3 per second each of river water and sea water. There is no way that can be done passed a membrane of just 1m^2.