Quaise's ultra-deep geothermal power plan is one of the most exciting and fascinating green energy projects we've seen. In a nutshell, this Boston-based MIT spin-off says it has repurposed powerful millimeter-wave beam technology – originally developed to superheat plasma in fusion experiments – to blast through previously undrillable rock far below the Earth's surface.

The company says this will allow it to drill bore holes far deeper than has ever previously been possible, going down far enough to access rock temperatures around 500 °C (932 °F). That's well past the point where water becomes heated to a "supercritical" state that radically boosts the efficiency of geothermal power extraction.

The end result: massive, virtually inexhaustible geothermal energy resources will become available practically anywhere on the planet. More or less any existing power station that uses fossil-fueled heat to create steam and run turbines can be connected to a totally reliable, 24-hour supply of green energy that'll keep those turbines turning without a single puff of CO2 escaping, and without the worrying intermittency of other renewable sources like wind and solar energy.