The plant will generate about 880,000 kilowatt hours of electricity per year—enough to help run a nearby desalination facility and supply around 220 homes. That equals the output of two soccer fields of solar panels, but osmotic power keeps running day and night, in any weather.
This seems like a terrible use, since these plants work by mixing fresh water with seawater (or in this case the brine leftover from desalination). I guess the catch is they can use treated wastewater instead of potable water.
This method gains very little net energy compared to other renewables.
“While energy is released when the salt water is mixed with fresh water, a lot of energy is lost in pumping the two streams into the power plant and from the frictional loss across the membranes. This means that the net energy that can be gained is small,” said Kentish.
Why do it, then?
Is this a proof of concept/MVP build, so they can iterate more efficient versions? A vanity project? A mistake?
Because osmotic power has enormous potential in the sense that millions of cubic meters of fresh water is running into oceans all over the world every minute. If we’re able to get even a low-efficiency method of using the salinity gradient to generate power working then every place a river meets the sea is essentially an unlimited (albeit low-yield) power source.
This is tech that doesn’t rely on elevation (like hydropower) or weather conditions (like wind/solar) it’s stable and in principle possible to set up at pretty much any river outlet, which is great!
Gotta be careful about ecosystems though. River deltas are incredibly important and fragile areas.
Dams 2.0
Oh absolutely. As with all other infrastructure, there is a cost to be paid. However, when you look at an average to small river, even routing 10 % of the water via an osmosis plant before passing it to the sea is an absolutely massive volume. There’s also the point that you don’t want to build these things in large, meandering, flat river deltas. You want a large salinity gradient, which means relatively small, fast-running fresh water meeting the ocean more “suddenly” than what you get in a classical river delta is the optimal source here.
Turning unpotable water into potable water with little or no additional cost, while not harming the environment, isn’t exactly a loss.
Returning to this thread long after everyone has moved on.
How do you get enough net energy out of mixing brine from desalination with fresh water to use to separate saltwater into brine and fresh water? Especially when the energy producing method is already known to have poor efficiency?
This seems like this is just terrible at converting treated wastewater into drinking water. Must have something to do with government subsidies instead.
Finally, power at night, when everyone’s asleep and we always have had excess.
That’s when my electric car is plugged in and taking up quite a bit of power.
That’s when it should be plugged in.
So, then why are you confused about what’s using power at night?
The energy can be stored for use for later during the day
I think the article author is completely confused and doesn’t understand what’s happening. There are hints of what’s happening in this paragraph.
Fresh water—or treated wastewater—is placed on one side of a membrane. On the other side is seawater, made even saltier by concentrating leftover brine from a desalination process. The difference in saltiness pulls the fresh water across the membrane, increasing the pressure on the saltwater side. That pressure is then used to drive a turbine, generating electricity.
I don’t think any fresh water is being used. I think what’s actually happening is…
Very salty wastewater (from the desalinization plant) is placed on one side of a membrane. On the other side is seawater. The difference in saltiness pulls the wastewater across the membrane, increasing the pressure on the saltwater side (or maybe the other way around). That pressure is then used to drive a turbine, generating electricity. The waste then is just water that’s saltier than sea water, but less salty than what came from the desalinization plant.
Yeah, it’s just recovering a little of the energy spent in desalination, making it slightly less energy consuming.
So it’s a turbo engine.
There*
Friggin hell. Thanks.
Why isn’t it fresh (non-salty) wastewater?
Lots of places treat their wastewater and then discharge it. For example, where I live, wastewater, that is to say, sewage which has had solids filtered out, is still rather pooey and pissy but not salty, gets treated (I don’t know how) and is then injected into natural underground aquifers where it eventually percolates out to bores or springs where it’s collected and used for irrigation, contributes to natural springs, or possibly even winds up in a drinking water catchment.
All wastewater, regardless what happens to it, has to be treated before release. If it’s still 99.9% fresh, then why not use it to create osmotic pressure before dumping it.
Technical explanation : with reverse osmosis you have :
(salty water + energy )
→ ( fresh water + highly salty water )So, reverse this process (call it osmosis plant ?) and you get energy … e.i. :
( fresh water + highly salty water )
→ (salty water + energy )I think it’s more like:
(salty water + unpotable fresh water) → (salty water + potable fresh water + energy)
…with a few steps in between. Even if most of the power is used in running the plant, you end up with potable fresh water and no brine being dumped into the ocean, which is a net win.
Based on the limited power generated I wonder if we can do something similar with cola and menthos.
Wow, I did not even think of that! This guy sciences!
