Arie,
Interesting stuff.
I know zip about sources of natural energy.
From the zip I like solar.
There used to be a chap on a goffer with a solar cell to keep him out of the sun.
I would see him down the shops frequestly many miles away from where he lived.
I think he passed away because I have not seen him for years.
Anyhow with the increase in petrol prices I think a device for personal transport that is solar powered would be great.
So I have started working on a solar powered trike.
I suppose it has already been done but still it should be a lot of fun.

I know that the voices in my head aint real,
but they have some pretty good ideas.
There is no such thing as a quick fix and I've never had free lunch!