MIT investigates power generation from the meeting of river water and seawater

There was a prototype salt power plant in Norway that eventually was abandoned:

http://en.wikipedia.org/wiki/Statkraft_osmotic_power_prototy...

The competition in energy generation is fierce.

For those wondering how this works, basically when you have two liquids with different salt concentrations separated by a semipermeable membrane, the liquid with the lowest concentration tends to get pulled into the one with the higher concentration - this builds up a pressure difference that can be used to drive a turbine.

Interestingly, the same thing happens in living organisms - saltwater fish loose water to the sea so they would dehydrate if it weren't for special precautions, while freshwater fish have the opposite problem, they would end up too diluted if their body didn't have means of getting rid of the excess water.

some of the most vital and complex ecosystems, responsible for huge amounts of life on the planet. I think I would rather look elsewhere.

Unfortunately, even if this works, it will likely have less and less application over time. California has very little fresh water reaching the ocean, and as population increases, and drought increases, we're sending less fresh water to the ocean.

And, over time, it takes more & more energy to make water fresh/clean in the first place, and to move fresh water around.

So, any power generation scheme that requires using fresh water is not on a good trajectory. It's good science experimentation though, & may spark other more useful ideas.