Editor's note: This article originally ran on e-tech and appears here courtesy of the IEC. Geothermal energy, or energy stored below the Earth’s surface in the form of heat, is breaking through the constraints which, until recently, held it back. It began this year, at what the International Energy Agency (IEA) calls a "critical juncture," with installation costs falling, major power purchase agreements (PPAs) being signed and large-scale next generation geothermal projects coming online.