A significant portion of the cash unlocked over the long term by this month’s climate talks could end up going into storage, say experts.

In the wake of the U.N. talks in Paris, trillions of dollars of investment in green energy had been pledged by development banks, pension funds, corporations and other investors. 

Hugh Sharman, a principal at the Danish consultancy Incoteco, said much of that money might need to be earmarked for storage.

“For renewable energy to succeed as a replacement for fossil-based electricity generation, storage needs to be a significant fraction of the world’s 5,600-terawatt power industry,” he said. He did not project exactly how much would be spent, however.

Cosmin Laslau, a senior analyst at Lux Research, said spending on storage would inevitably increase as a result of higher penetrations of intermittent renewable energy generation.

“Essentially, COP21 is providing a helpful push -- albeit a hard-to-quantify one -- to an emerging market for renewable-tied energy storage that should eventually grow to be worth tens of billions of dollars," said Laslau. 

There is growing evidence from Europe that differences in renewable energy generation do not level out over large geographic regions as much as previously thought.

A November review of European wind output posted on Energy Matters, an influential blog, shows clearly that peaks and lulls in wind resources tend to be reinforced across the whole continent, rather than canceling each other out.

“On many occasions, it is flat-calm across most of Europe, and 100 percent backup from other dispatchable sources is required,” noted author Euan Mearns.

The findings contradict research by Gregor Czisch, formerly of the Fraunhofer Institute, who concluded in the 2000s that it would be possible to power all of Europe with geographically dispersed intermittent renewables.

They also cast doubt over the wisdom of strengthening interconnections across Europe. The European Commission has estimated transmission system operators need to spend €40 billion (USD$43 billion) on grid interconnections up until 2020.

If improved connections cannot solve the challenge of renewable energy generation intermittency, then the need for storage becomes even greater.

This is already being reflected in policies for areas with lots of renewable energy, such as California, said Shawn Buckley, CEO of Focused Sun, a solar-plus-storage technology developer in New Mexico.

“When solar was 1 percent of the utility's mix, the utilities didn't care much that solar folks used them as backup on cloudy days,” he said. “Now that places like California are requiring 50 percent renewables, U.S. utilities are pushing demand charges.”

“But with storage, even for six hours, the solar peak at noon gets pushed to the load peak in the early evening. Everyone loves that," said Buckley.

Buckley said expanded renewables policies as a result of the international climate agreement “will free up funding for storage" as regions of the U.S. start grappling with much more intermittent generation.

Storage will be equally important internationally. However, only one of the world’s top three polluters, India, made specific reference to energy storage in its voluntary target.

“One of the important areas of global collaborative research should be clean coal and fossil fuel, energy management and storage systems for renewable energy,” it said.

Both of the world’s top two polluters -- China and the U.S. -- already have significant battery industries and will likely keep pushing the technology.

Another three of the top 10 polluters -- Japan, Germany and South Korea -- are also starting to invest heavily in residential and grid-scale energy storage. These countries will likely see some of the strongest growth in storage adoption in the coming years.

Ravi Manghani, a senior storage analyst at GTM Research, called storage is "a useful tool for nations to meet their carbon reduction targets."

"Storage can provide countries with growing energy appetite and weak grids an opportunity to leapfrog carbon intensive infrastructure development through growth at the grid edge, paired with solar, wind or other renewables. In developed nations with already high renewable penetration and stable grid, it can aid adoption of even more renewables without integration concerns," said Manghani.