Japan has opened its first osmotic power plant

In 1998 when I was in high school I dreamt up this kind of power plant and asked my physics teacher where the power really came from. Not happy with his answer I asked a university physics Q&A service [1]. Not happy with their answer either I did a masters in engineering physics and kept asking this question whenever I got the chance. Never got a really good answer. But I’m glad to see it works.

1. https://fragelada.fysik.org/index.php?amne=Energi&stage=&key...

My instinct here is just to wave it away saying "I bet the temperature of the system falls when you do this, and you need a minimum temperature for it to work over a given salinity gradient". Is it not that simple?