The pump storage hydro scheme is designed to "soak up" excess power generated by wind and wave farms, using it to pump water up to a reservoir.

BBC: Highland councillors support Lochaber hydro plan

Hydro dams can be reversed and pump water uphill so that the next day, when gravity pulls the water back down, the turbines spin to make electricity.

FORBES: A123 Bites the Dust Because They Forgot Their ABCs