There was a thread on this a few weeks ago, you may be able to find it with the search function , but here are a couple of links to be going on with.
http://www.future.org.au/news/december/titanium.html
http://www.sciencealert.com.au/news/20070604-14870-2.html
http://www.smh.com.au/news/environment/science-turns-sun-surf-into-green-energy/2007/03/20/1174153066798.html