Energy storage is taking on a greater role in the power grid. But how big can it get?

In a fast-developing industry teeming with technologies that promise to be the next big thing, energy storage appears to be the biggest.

Its supporters not only sing its praises but also tout what they say is its inevitability.

“We’re going to have 10 times as much energy storage on the grid by the end of this decade and that is going to impact every facet of the energy industry,” said Matt Roberts, executive director of the Energy Storage Assn., an industry trade group.

But the electrical grid is a harsh taskmaster. 

As far back as the 1880s, Thomas Edison wrestled with a way to effectively take surplus energy, save it and then use it at a later date.

It’s not enough to just store energy — system operators have to find a way to balance supply and demand instantaneously, generating every kilowatt that is demanded by customers who expect their lighting/heating/air conditioning to come on the moment they flip a switch.

“There’s a whole bunch of different, new storage technologies, but we get ones that seem to be cheaper but they fail on the density problem” of storing a large amount of energy in a small space, said Stephen Brick, senior fellow on climate and energy for the Chicago Council on Global Affairs. “We get ones that seem to improve on the energy density and they fail on the cost side.”

Energy storage technology takes on a lot of forms.

The most prominent is pumped hydro, in which water is pumped uphill behind dams and then released, with the ensuing rush of water generating power.

Pumped hydro is the biggest source of energy storage in the U.S., accounting for 96% of the industry’s total storage capacity.

But chemical storage — as in batteries — may be the source people are most familiar with, especially given the media attention that inevitably accompanies any announcement by billionaire entrepreneur Elon Musk.

Last year, Musk unveiled the Powerwall, a rechargeable lithium-ion battery for homes, and the PowerPack, a 100 kilowatt-hour utility-scale battery. The $2-billion Tesla Gigafactory outside Reno, Nev., promises to produce enough lithium-ion batteries for 500,000 cars a year.

Then there is thermal storage, such as concentrated solar power plants like the sprawling 392-watt Ivanpah facility in the Mojave Desert.

Other energy storage technologies include compressed air, stored under pressure in underground caverns, and flywheels, which are discs spun at high rates of speed.

For all of the attention energy storage has recently received, it represents a tiny portion of the mammoth electricity and power industry — 21,000 megawatts (21 gigawatts) of capacity, a little under 2% of the nation’s peak demand, according to the Energy Storage Assn.

But energy storage is taking on a greater role as the power grid — especially in California — integrates more renewable energy sources such as solar and wind energy.

Solar has grown from 0.3% of the state’s power mix in 2010 to 6% in 2015, the most recent year for data by the California Energy Commission.

Wind has a larger share, nearly doubling from 4.7% in 2010 to 8.2% in 2015.

Although solar and wind can produce plenty of energy, they have a big problem with intermittency. When the sun isn’t shining, solar production slumps, and when the wind isn’t blowing, wind power wanes.

The trick is trying to find a way to fill in the gaps.