It has been hot and sticky in London recently, but I'm still surprised to hear we can get energy from the moisture in the air.
Researchers have used bacterial spores that expand when moist to create 'artificial muscles' which expand and contract. They powered an LED with this motion. It's a very small amount of energy, but humidity differences are all around us. Maybe they'll find a way to scale it up?
I think it's a great approach to finding new energy sources. Sometimes the answers are going to be found in surprising places.