They are just re-capturing some of the energy the system spent turning salt water into fresh. Because that results in extremely salty brine water waste, you can get some energy as it gets diluted back down to sea water concentration.

There no “new” energy in the system, it’s just wasting less.

Isn’t efficiency just getting closer and closer to a perpetual machine? Using science and the physics to the absolute limit!

The reason being that dumping the brine back into the ocean creates a dead zone wherever that dump point is, since the relative concentration of salts is higher compared to regular seawater.

They’re almost certainly recreating seawater just to help alleviate the dead zone effect and figured out how to get some free electricity out of it too

From what the article says, it's actually a pretty cool way of improving desalination plants. They use the left over brine, from desalination, that has a very high concentration of salt, and use it as the high salt concentration side, with regular seawater being used on the other side. This both gives them free energy and reduces the side effects of pumping that extremely salty water into the sea by diluting it.

It can use treated waste water, so it's not that specialized.

It generates 880.000kWh/year, where I live that enough for 180 families (2 adults, 2 kids) with an average consumption in a house, and almost 350 in apartments. That's not an insignificant amount IMO.

This plant is part of a bigger chain. So while yes, on its own it seems waste of effort, as part of the entire chain it's a reasonable step to be more environmentally friendly and recover some energy in the process.

A local plant desalinates water, resulting in fresh water and a brine solution that has much higher concentration of salt in it than regular sea water.

Dumping the brine solution on its own would kill most plant and animal life around the dump site due to large saltwater concentration, so an alternative method must be found to dispose of the brine.

Waste water from other processes can be mixed with the brine to bring it more in line with seawater salinity, making it safe to reintroduce to the ocean without severe ecological impact. This waste water is deemed to difficult or intensive to purify and treat to bring it back up clean water standards, and I'm assuming tested or filtered so as not to introduce hazardous chemicals that could damage the reverse osmosis membranes as well as sea life.

Because there is way to mix the waste water and brine through membranes that can be used to generate electricity, this process is utilized to recover some of the energy expended in purifing the original batch of seawater resulting in the brine.

It's not a perfect process but it is a means of getting some use out a waste product, similar to burning garbage or rotting food rather than just dumping it into a pit and letting it rot and release methane.

Its miles better than traditional desalination - requiring so much energy that burning fossil fuels is unavoidable. And brine is chucked back in the ocean. Basically an environmental catastrophe.

If you think of it on the scale of one community - providing potable water, dealing with treated wastewater AND getting a surplus of energy while treating the brine it is actually pretty clever.

If it makes you feel better you could probably slap some solar panels on those flat roofs too.

You should call up Japan and let them know how wrong they are.