On Tue, 29 Jul 2008 10:47:16 -0400, "Matthew Miller" said: > Stirling engines might work out: use metal hydrides to store hydrogen for > the engine's working gas... not sure about the heat source. I can't see how Stirling engines can scale up beyond a certain point. It's a volume vs area thing. Cheerful regards, Bob -- http://www.fastmail.fm - One of many happy users: http://www.fastmail.fm/docs/quotes.html -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist