The way the world gets its electricity is undergoing a rapid transition, driven by both the increased urgency of decarbonizing energy systems and the plummeting costs of wind and solar technology. In the past decade electricity generated by renewables in the U.S. has doubled, primarily from wind and solar installations, according to the Energy Information Administration. In January 2019 the EIA forecast that wind, solar and other nonhydroelectric renewables would be the fastest-growing slice of the electricity portfolio for the next two years. But the intermittent nature of those sources means that electric utilities need a way to keep energy in their back pocket for when the sun is not shining and the winds are calm. That need is increasing interest in energy-storage technology—in particular, lithium-ion batteries, which are finally poised to be more than just a bit player in the grid.

For decades pumped-storage hydropower, a simple process that features reservoirs at different elevations, has been the dominant large-scale energy-storage method in the U.S. To store energy, water is pumped into the higher reservoir; when that energy is needed, the water is released into the lower reservoir, flowing through a turbine along the way. Pumped-storage hydropower currently accounts for 95 percent of U.S. utility-scale energy storage, according to the Department of Energy. But as efficiency and reliability have improved, and manufacturing costs have tumbled, lithium-ion batteries have surged. They account for more than 80 percent of the U.S.’s utility-scale battery-storage power capacity, which jumped from just a few megawatts a decade ago to 866 megawatts by February 2019, the EIA says. A March 2019 analysis by Bloomberg New Energy Finance reports that the cost of electricity from such batteries has dropped by 76 percent since 2012, making them close to competitive with the plants, typically powered by natural gas, that are switched on during times of high electricity demand. To date, whereas batteries have largely been used to make brief, quick adjustments to maintain power levels, utilities in several states, including Florida and California, are adding lithium-ion batteries that will be able to last for two to four hours. Energy research firm Wood Mackenzie estimates that the market for energy storage will double from 2018 to 2019 and triple from 2019 to 2020.

Lithium-ion batteries will likely be the dominant technology for the next five to 10 years, according to experts, and continuing improvements will result in batteries that can store four to eight hours of energy—long enough, for example, to shift solar-generated power to the evening peak in demand.

But getting to the point where renewables and energy storage can handle the baseline load of electricity generation will take energy storage at longer timescales, which will mean moving beyond lithium-ion batteries. Potential candidates range from other high-tech options, such as flow batteries, which pump liquid electrolytes, and hydrogen fuel cells to simpler concepts, such as pumped-storage hydropower and what is called gravity storage. Pumped-storage hydropower is cheap once it is installed, but it is expensive to build and can be used only in certain terrain. Similarly simple is the concept of gravity storage, which purports to use spare electricity to raise a heavy block that can later be lowered to drive a turbine to generate electricity. Although a few companies are working on demonstrations and have attracted investments, the idea has yet to take off. Other options are still under development to make them sufficiently reliable, efficient and cost-competitive with lithium-ion batteries. There were only three large-scale flow-battery storage systems deployed in the U.S. by the end of 2017, according to the EIA, and utility-scale hydrogen systems remain in demonstration stages. The U.S. government is funding some work in this arena, particularly through the Advanced Research Projects Agency–Energy (ARPA-E), but much of the investment in those technologies—and in energy storage in general—is happening in China and South Korea, which have also ramped up storage research.

(Reuters) – Nevada’s largest utility NV Energy will procure 1,200 megawatts (MW) of solar electricity paired with batteries, or enough to power about 228,000 homes, as it seeks to double its renewable energy resources and move away from fossil fuels.

The addition of energy storage to all three projects underscores how important – and cheap – batteries have become as utilities seek to extend the working hours of their solar facilities.

“The energy during the day time when the solar panels without a battery produce power, though valuable, is not as valuable as the energy when the sun goes down in the summer when air conditioners are running at full capacity,” Tom Buttgenbach, chief executive of 8minute Solar Energy LLC, which is developing one of three new solar and storage projects for Berkshire Hathaway Inc unit NV Energy, said in an interview on Tuesday.

The three solar projects will more than double the utility’s renewable energy by 2023, NV Energy said in a statement late on Monday.

The projects include a 690 MW array with a 380 MW battery storage system on federal land near Las Vegas. The Gemini Solar project is being developed by Quinbrook Infrastructure Partners and Arevia Power, NV Energy said.

The Southern Bighorn Solar & Storage Center, developed by 8minute, will combine a 300 MW solar facility with a 135 MW lithium ion battery and will be located on the Moapa River Indian Reservation. The battery will provide 4 hours of storage to extend the power plant’s effectiveness into the evenings.

8minute said the project will deliver power for about $35 per megawatt-hour, less than the cost of electricity generated by natural gas or coal.

The final project is a 200 MW plant with a 75 MW battery storage system on the Moapa Band of Paiutes Indian Reservation. It is being developed by EDF Renewables North America.

In April, Nevada passed a law requiring utilities to source 50 percent of their power from renewable sources by 2030. NV Energy said it has a long-term goal of serving customers with 100 percent renewable energy.

The US National Renewable Energy Laboratory (NREL) has put numbers on the significant potential for energy storage to replace peaking capacity on the grid in the US, albeit with an understanding that as the peak changes, the goalposts will also move.

NREL has said in a report just-published that around 70GW of peaking capacity in the US – from a total base of about 261GW – could be served by energy storage systems of four, six and then eight hour durations.

However, as has been pointed out previously to Energy-Storage.news by the likes of redT executive Scott McGregor in the past, once clean energy starts tackling the time during which demand peaks, the peak itself widens as a window during the daytime or – more likely – early evening.

As more and more storage is installed to allow for peak mitigation, so the peak could become a longer event. McGregor was talking specifically about demand reduction for commercial businesses in that instance, but it appears the same could broadly hold true for peaking capacity.

NREL said that some 150GW of peaking capacity is set to be retired within 20 years in the US, with natural gas turbines coming to the end of their lifetimes, but it cannot be assumed that this can all be replaced immediately or directly with energy storage.

“The step from 4 hours to 6 hours is relatively small (about 8 GW), because the first 4 hours of storage typically widens the peak to about 6 hours, leaving little room for 6-hour storage. The 8-hour step is much larger (about 34 GW), leading to a total potential for combined durations of about 70 GW,” the authors of the report, ‘The potential for battery energy storage to provide peaking capacity in the United States’, wrote.

Appetite for renewables remains the ‘X Factor’
However, that takes into account mostly a business-as-usual scenario, and in the event that larger and larger shares of renewable energy go onto the grid and change net loads even further from their present day shapes – which is hardly unlikely – that potential figure could see a large increase, NREL said.