View larger version | The promise of cold fusion was a promise of clean, unlimited energy — a promise still hoped for. Alternatives to fossil fuels are in the works, some are closer to practical use than others and each has pluses and minuses. The Z-pinch (a Z-machine is pictured at lower right) ionizes plasma and produces huge amounts of power — enough for fusion, its proponents say. Credit: Clockwise, from bottom left: iStockphoto by Deejpilot; Animean; Andreas Weber; Allkindza; Trout55; Randy Montoya/Sandia National Labs