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Could long duration battery storage be the key to solar growth?

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Long duration battery storage could boost the solar industry.

The federal Department of Energy (DOE) recently launched an initiative cutting the cost of long duration battery storage by 90 percent within a decade. The Long Duration Earthshot will provide funding for projects trying to make new types of storage technology – including storage for solar energy – commercially viable by 2030.

The definition of long duration storage remains vague. This is mainly because it’s a newer part of the energy mix. One industry expert commented half-jokingly to Greentech Media that it includes everything from batteries capable of discharging power for six hours to technologies able to release energy for up to 1,000 hours. Mateo Jaramillo, co-founder of battery start-up Forum Energy, added, “It’s time we start moving away from the designation of hours and start describing storage in terms of the function it can provide.”

The Department of Energy’s Earthshot seeks to develop the most promising technologies in this area. Its definition of long duration is any technology that can release energy for 10 hours or more.

Electrochemical batteries, like flow batteries, are one of the most promising prospects. The DOE will also consider mechanical and thermal options for long duration storage. Some interesting prospects include compressed air storage, pumped hydro, and block stacking.

“We’re going to bring hundreds of gigawatts of clean energy onto the grid over the next few years, and we need to be able to use that energy wherever and whenever it’s needed,” explained Energy Secretary Jennifer Granholm.

Battery storage is a boost for solar energy growth

If long duration storage projects prove viable, solar power could be one of the main beneficiaries. One of solar’s main drawbacks is that the amount of electricity it produces can vary. Long duration solar battery storage offers one way to overcome this problem.

A long duration solar battery capable of producing energy for about 10 hours could bridge the gap between the sun going down in the evening and rising again the next day. This would mark an improvement over lithium ion batteries. They can typically release power efficiently for about four hours. This allows power produced by solar panels to be used during the evening. Natural gas plants are still needed to supply power when the batteries run out.

Longer-term storage technology able to release energy for 24 to 48 hours also has an important role in boosting reliability. These facilities could help compensate for cloudy days when solar panels are less productive.

Storage facilities capable of releasing energy for hundreds of hours could support solar in energy markets with seasonal shifts. For example, regions in the northern United States that have much colder winters could benefit from them. The storage facilities could fill the gap caused by declining solar output during the shorter days and increased energy demand to keep buildings warm.

All of this sounds good in theory. But a major problem is that long duration options need to get considerably cheaper. Otherwise, alternative options will have the edge in energy markets. Nuclear energy, green hydrogen, and natural gas plants with carbon capture are all in direct competition with long duration storage.

A test for the commercial viability of long duration storage

An opening for long duration storage technology could soon arrive in California. A coalition of eight community choice aggregators released the first major request for proposals for long duration energy storage in late 2020. To qualify, the technology must store at least 50 megawatts of power and discharge it for at least eight hours. The coalition wants 500 megawatts of long duration energy storage facilities to be operational by 2026.

The coalition of CCAs indicated that providers of various storage solutions have shown an interest. These include pumped hydro, compressed air storage, thermal storage, and flow batteries.

This is only a small down payment. According to one study, California alone will require 40 gigawatts of long duration storage to meet its 2045 goal of carbon-free electricity.

What does this mean for you?

Most energy customers won’t experience a direct impact from long duration storage just yet. Many of the technologies included in this sector are still in the development stage. Others that are further along still need to come down in price to make them commercially viable. The DOE’s Earthshot aims to accelerate this process.

If the DOE project proves successful, long duration storage could play a much larger role in supplying your energy by the end of the decade. Keep in mind that the cost of lithium ion batteries has dropped by over 80 percent since 2010. This shows that such a dramatic decline in operational costs for new, comparatively untested technologies is a realistic possibility.


Jordan Smith is a writer and researcher with expertise in renewable energy and deregulated energy markets. Jordan has written extensively on the deregulated energy market in Texas and the challenges confronted in the clean energy transition, and conducted research projects within the energy industry. Further articles by Jordan can be found at

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