SANTIAGO (Reuters) - Valhalla Energia plans to build a hydroelectric power generation plant in Chile’s parched Atacama desert, the world’s driest, by using solar energy to pump sea water up the side of a 600 meter cliff and then have it rush back down to the Pacific Ocean below.

Located near one of the world’s key copper-mining regions, founders plan to service mainly industrial and commercial clients.

The renewable energy company said on Friday that Chilean regulators approved the environmental impact study for its 300-megawatt Espejo de Tarapaca project, located 100 kilometers south of Iquique in northern Chile, which is home to some of Chile’s biggest mines.

The $400 million project will use solar energy to pump seawater to the top of a coastal cliff, where it will be stored in natural depressions. At night, electricity will be generated by releasing the water and letting gravity do the rest, the company said.

Valhalla is still awaiting regulatory approval though for its 600-megawatt, $500 million Cielos de Tarapaca solar panel energy project, which will provide the energy needed to pump the seawater up the cliff wall.

The two separate projects will complement one another but Valhalla said it has yet to secure financing for either of the projects.

“We found these natural depressions that we believe were very ancient lakes, but obviously there is nothing there now, it is a desert, that will allow us to store water,” the company’s co-founder and chief executive Juan Andres Camus told Reuters.

If the natural depressions are filled to capacity with seawater, the project can continuously provide hydroelectric energy for a little over nine days, Camus said. “That adds a lot of value from the point of view of system’s security.”

Using the ancient dry lakes to store water has the added benefit of not having to spend the money or go through the permitting process to build a dam.

Construction on Espejo de Tarapaca is expected to begin in the second half of 2016 and commercial operation is slated for 2020.