Thousands of hills across Britain could be transformed into renewable energy batteries thanks to a new ‘high-density’ hydropower system buried underground. Developed by UK startup RheEnergise, the system puts a modern spin on pumped storage hydro, a centuries-old technology which accounts for 95% of today’s energy storage capacity. Pumped storage hydro uses surplus electricity to pump water into an uphill reservoir, later releasing it back downhill over a set of turbines and into the original lake, generating electricity on demand. Except RheEnergise’s hydro system doesn’t use water at all, but a proprietary high-density fluid. Named R-19 it is 2.5 times…

This story continues at The Next Web