At the Paris climate change conference earlier this month, all eyes were on some massive announcements in the solar and wind energy space — including plans in Africa to install 300 gigawatts of renewable energy capacity across the continent by the year 2030. A gigawatt is a billion watts — and this would be nearly double the electricity capacity that the continent currently supports.

Less noticed, however, is that a key enabling technology for solar — and for the future of clean energy — is also starting to grow: Energy storage. When solar systems are connected with batteries or other forms of storage, they can cease to be dependent upon whether the sun is shining and how strong its rays are at a given moment. Rather, solar energy can be stored and used at a later time. Including at night.

And now AES, a large energy company headquartered in Arlington, Va., has announced a very large deal in the battery space. It is gaining access to 1 gigawatt-hour worth of lithium ion batteries from Seoul-based LG Chem, a chemicals giant that also has a strong business in making lithium ion batteries for electric and hybrid electric vehicles. The batteries will be deployed in AES’s Advancion platform, which provides large scale grid energy storage to utility companies.

Power – in this case, a gigawatt – refers to the amount of electricity that can be discharged instantaneously. But when it comes to batteries, what’s also important is how long the battery can operate — its energy. Thus, 1 gigawatt hour would refer to the capacity to discharge that much power for one hour — but it could also refer to the ability to discharge 250 megawatts (or million watts) for four hours.

Either way, that’s a very large amount of batteries. For comparison, GTM Research recently forecast that the U.S. will deploy a record 192 megawatts of energy storage in 2015.

The energy storage business is “definitely moving to a new level this year,” says John Zahurancik, president of AES Energy Storage. Zahurancik says the big buy of batteries is a “vote of confidence” in this business, which drew dramatic attention earlier this year when Tesla Motors announced a home battery product dubbed the “Powerwall.”

But for now, the biggest business for batteries isn’t in the home, where they can serve a backup role in the event of an outage or pair with a rooftop solar system; it’s on the grid, where there is a constant need to be able to manage shifting electricity demand at different times of the day. Batteries that can switch on automatically at key moments can provide a major grid service, which is why they’re seeing more and more demand.

Thus, AES is in effect packaging lots of batteries, provided by LG Chem, into large systems that large power companies can purchase and then install or integrate on the grid wherever they need this new capacity. AES directly advertises its batteries as the “complete alternative” to “peaking power plants.”

“The projects are generally getting bigger, they’re getting longer in duration, and they’re happening in more markets around the world,” says Zahurancik.

“We’re very bullish about the outlook for storage,” adds Peter Gibson, director of sales for energy storage systems with LG Chem. “It’s in a relatively early stage, but there are an increasing number of successful commercial projects which are in operation today. We’re well past the stage of doing pilot demonstrations.”

“The order size is big, but in context of AES’s pipeline – two big 100 MWs in Ireland and California, and several others in 10-20 MWs range — could see deployments starting as early as next year,” said Ravi Manghani, an energy storage analyst with GTM Research, in reaction to the deal.

According to AES, deployments of large batteries on the grid will reduce greenhouse gas emissions in several ways. In some cases they can supplant the need for so-called “peaker” plants, natural gas plants that can ramp up fast when there is high demand — but also tend to have considerable emissions. Batteries can ramp up fast too — but without the emissions.

There’s also a climate benefit if batteries help existing power plants to “run at more steady rates of output, so they don’t have to ramp up or ramp down as much,” AES said in a statement.