Energy shift creates opening for 'world's largest batteries'

A question is hovering over the transition from fossil fuels to cleaner energy such as wind and solar: What happens when the wind doesn't blow or the sun doesn't shine

LUDINGTON, Mich. -- Sprawled like a gigantic swimming pool atop a bluff overlooking Lake Michigan is an asphalt-and-clay pond holding enough water to produce electricity for 1.6 million households.

It's part of the Ludington Pumped Storage Plant, which uses simple technology: Water is piped from a lower reservoir — the lake, in this case — to an upper one, then released downhill through supersized turbines.

Supporters call these systems “the world's largest batteries" because they hold vast amounts of potential energy for use when needed for the power grid.

The hydropower industry considers pumped storage the best answer to a question hovering over the transition from fossil fuels to renewable energy to address climate change: where to get power when the sun isn't shining or the wind isn't blowing.