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Japan has opened its first osmotic power plant

(www.theguardian.com)
301 points pseudolus | 3 comments | 25 Aug 25 02:53 UTC | HN request time: 0.664s | source
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elil17 ◴[26 Aug 25 17:55 UTC] No.45029999[source]▶
They really fail to explain a key point here. The reason you colocate this with a desalination plant is because you use the super-salty wastewater from desalination as the salty side of the osmosis power plant. Then you find some wastewater which is low in salt (such as semi-treated sewage), and use that as the fresh side of the osmosis power plant.

The end result is that the salty wastewater is partially diluted, which means it has a lower environmental impact when it is discharged to the ocean.

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1. hinkley ◴[26 Aug 25 18:34 UTC] No.45030461[source]▶
Basically this is like the recouperator on early heat engines, but with a liquid gradient instead of a thermal one.

It's making desalination more efficient and the effluent a bit easier on the ecosystem.

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2. HPsquared ◴[26 Aug 25 19:38 UTC] No.45031285[source]▶
Goes nicely with the "pressure exchanger" which recovers the pressure of the high pressure brine waste stream. Lots of heat exchanger analogies!

https://en.m.wikipedia.org/wiki/Pressure_exchanger

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3. hinkley ◴[26 Aug 25 23:21 UTC] No.45033554[source]▶
Yeah those are funky devices. I'll be curious to see what the production cost per cubic meter of fresh water ends up at.