People have been killed over this stuff. Two which come to mind are stan meyer, and dr. eugene mallove. I know that hydrogen can produce overunity as well. They say they tapped into zero point energy.

http://waterpoweredcar.com/stanmeyer.html
http://www.lutec.com.au/
http://jlnlabs.imars.com/bingofuel/html/bfrhowto.htm


stan meyer patents
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http://www.rexresearch.com/meyerhy/meyerhy.htm