After years of stagnation, Concentrated Solar Power (CSP) is staging a comeback in a variety of new forms. The approach taken by Australian startup RayGen is so unusual that it might be better referred to as Concentrated Photovoltaic (CPV). A RayGen solar plant employs satellite-grade photovoltaics at the concentrator to produce one-third of its energy, while the other two-thirds of the power goes into heating water in a thermal storage pit to just below boiling. Traditional CSP plants use vast heliostat mirror arrays to concentrate heat on a receiver, bringing a molten-salt Heat Transfer Fluid (HTF) to around 500 degrees Celsius. The salt is then used to heat water to power steam turbines, and also serves as long-duration energy storage.…