BP and Chevron have led a US$40 million investment round for a Canadian startup that claims to have developed a unique way to extract energy from geothermal heat on demand, using an unpowered looping fluid design that's already prototyped in Alberta.

Solar and wind are scalable renewable resources, but only produce energy when the sun and wind are up, not when the grid needs it. Hydro can respond well to demand, but it's not really scalable; the geometry of your dam dictates the size of your operation. Regular geothermal needs volcanic levels of heat, which restricts it to certain locations, the same way hydro needs mountain reservoirs.

There are lower-temperature, low-enthalpy geothermal projects out there that can generate energy from hot rock in a flexible, scalable, on-demand fashion, but according to Eavor CEO John Redfern, these haven't taken off because they lose between 50-80 percent of the power they generate in the task of pumping the water up and down.