5 Energy Storage Solutions That Will Make Renewables a Viable Alternative to Fossil Fuels

By William Lamb
Grid-scale storage may be revolutionizing the market for clean energy.

For years, dreams of a bright green future fueled by clean sources of renewable energy have been tempered by the inconvenient reality of their intermittency. The sun doesn’t always shine, of course, and the wind doesn’t always blow, making it hard for them to consistently feed the grid that all of us count on to reliably deliver energy at the flip of a switch.

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Compressed-Air Energy Storage

Wind energy is used to power compressors that inject air at high pressure into large underground chambers. When demand peaks and the wind flags, the pressurized air is released—often with a small amount of natural gas—to power turbines or generators, producing electricity. The first such plant opened in Germany in 1978.

But that may at last be changing. From a set of enormous caverns in a salt formation southwest of Salt Lake City to California’s Tehachapi Mountains, experiments in mass-scale energy storage hold the promise to fundamentally reshape the way energy is produced and consumed.

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Pumped-Storage Hydroelectricity

Pumped-storage hydroelectricity is the oldest and most common form of bulk-energy storage. During periods of low demand, energy from the grid is used to move water to an upper reservoir. When demand rises, the water flows down to a lower reservoir through turbines that generate power like a common hydropower station.

The idea is simple enough: If energy from renewables can be stored and dispatched to the grid during periods of peak demand, solar and wind would become more cost-effective, simpler to scale, and truly viable alternatives to fossil fuels. "Storage has the effect of making renewable energy even more valuable because you can schedule it; you can control and dispatch it when you want it," says Janice Lin, who leads the California Energy Storage Alliance and  the newly founded Global Energy Storage Alliance. 

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Advanced Rail Energy Storage

Based in Santa Barbara, California, Advanced Rail Energy Storage has devised a system that draws energy from the grid to push a train of weighted cars uphill. When demand spikes, the cars are sent downhill, sending power back to the grid by using the turning power of the wheels on each car to generate electricity.

The storage movement appears to be gathering momentum. The consulting firm Navigant reported last year that 91 grid-scale energy storage systems, with a collective capacity of nearly 363 megawatts, were launched or announced between January 1, 2013, and September 30, 2014. Like many efforts to slow the pace of climate change, the shift toward storage is being driven by California, where Governor Jerry Brown signed a law in 2011 mandating that the state generate 33 percent of its electricity from renewables by 2020. The California Public Utilities Commission followed that in 2013 by ordering its investor-owned utilities to install 1,325 megawatts of storage, also by 2020.

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Flywheel Energy Storage

Flywheels are discs or cylinders that spin on an axis in a frictionless enclosure to store power in the form of kinetic energy. When demand for power rises, the spinning can be slowed to release energy to the grid. The advantages of flywheel storage include long life and low maintenance.

That explains why Southern California Edison, the state’s second-largest utility, made headlines in 2014 with a pair of bold moves that add up to a calculated bet on storage. It signed contracts for 264 megawatts of storage—a large order relative to its share of the 1,325-megawatt mandate—and it unveiled a 32-megawatt-hour lithium-ion battery facility in Tehachapi that it is treating as a "demonstration project," in part to evaluate its potential for integrating renewable energy from wind and solar into the grid.