STX deal in numbers, page-129

solar is abundant during the day and growing fast because it's so cheap.

With PHES, excess solar or wind (during daylight) pumps the water from the bottom dam back to the top dam. At night, when solar is gone and wind drop significantly the water runs from the top dam to the bottom dam and spins a turbine on the way - making electricity! Making a 24hr renewable power source!

Wind and solar are relatively cheap and quick to install but PHES is expensive, and requires a lot of engineering/time!

A national renewable power grid is years away and hydrocarbons (gas and coal) will be needed for years to come, but it will eventually happen.

All l am saying, is keep an eye on it....