If anybody creates a real one, it well sell so fast everyone will know about it. Even the oil companies. Why would they pass up the chance to patent and sell a superproduct and make billions more? Especially with oil running out?
More likely said energy/oil companies would buy the patents/inventions (or just "do" the inventor(s) in) , sit on them while they screw the consumer with fossil fuels until they run out, then go cap in hand to governments with this brilliant idea that they have for free energy, then screw the consumer under the pretense that they had to lay out vast amounts of capitol to develop this free energy technology.