Steve Lowe gazed into a gaping pit in the heart of the California desert, careful not to let the blistering wind send him toppling over the edge.

The pit was a bustling iron mine once, churning out ore that was shipped by rail to a nearby Kaiser Steel plant. When steel manufacturing declined, Los Angeles County tried to turn the abandoned mine into a massive landfill. Conservationists hope the area will someday become part of Joshua Tree National Park, which surrounds it on three sides.

Lowe has a radically different vision.

With backing from NextEra Energy — the world’s largest operator of solar and wind farms — he’s working to fill two mining pits with billions of gallons of water, creating a gigantic “pumped storage” plant that he says would help California get more of its power from renewable sources, and less from fossil fuels.