The Future is Long (Duration Energy Storage). By Hugh McDermott, Senior VP of Sales & Business Development

June 4, 2021

Ready or not, the watershed moment for long-duration energy storage has arrived. Over the next 30 years, the International Renewable Energy Agency (IRENA) anticipates a three-fold increase in global renewable electricity generation. A recent report from Guidehouse predicts that by 2030, more than 30 GWh of long-duration storage – representing nearly 40% of the total amount of storage deployed that year – will be installed in the global market. That’s a ten-fold increase compared to today.

The Energy Transition Needs Long-Duration Energy Storage

Prospects for increased renewable generation are now inextricably linked with energy storage because of the added value that storage projects provide grid operators, generating asset owners, and consumers. Within the past year or so, the market has seemingly hit an inflection point in realizing the need for energy storage with durations of eight hours or more – to the point that it’s almost the exception to see large-scale renewable energy projects that do not consider 8-to-12-hour energy storage options as part of their project assessment.

What these project owners are recognizing is the need for longer-duration energy storage as the penetration of renewable energy increases. The changes to California’s famous “duck curve” over the past five years readily illustrate the phenomenon, as the state’s renewable energy base has grown to represent approximately 30% of the overall generation mix. This, in turn, has led to ever-steepening and lengthening generation ramps that necessitate energy storage resources of longer duration. In fact, the California Energy Storage Alliance recently released a study forecasting that up to 55 GW of long duration energy storage will be required to meet the state goal of 100% renewable energy by 2045.

Long-duration energy storage has additional benefits that enable greater deployment of renewable energy generation. It can fortify aging grid infrastructure, helping communities keep the lights on during extreme weather events, such as wildfires and ice storms. It can also reduce grid congestion while deferring the need for new transmission lines.

Long-Duration Energy Storage Requires New Sustainable Technologies

Though li-ion was the first battery chemistry to unlock the market for electrified transportation and stationary storage-based grid services, the technology is widely considered to be less than ideal for longer-duration storage applications (defined as greater than four hours and less than a day). Besides the well-documented drawbacks of fire risk, toxic materials, performance degradation, and recycling challenges, li-ion battery technology does not economically scale in applications beyond four hours. To achieve energy storage durations greater than eight hours, a project has to deploy 2x the number of batteries required for a 4-hour system, at roughly twice the cost. 

Li-ion availability and certainty of delivery timing for stationary storage applications are also an increasing concern due to massive competing demand for electric transportation applications, as well as production and supply challenges related to key input materials such as nickel, manganese, and cobalt. The iron flow battery is a long-duration storage technology developed specifically to overcome these li-ion shortcomings. The battery uses an iron and saltwater electrolyte that is non-toxic and environmentally friendly. These easy-to-source, benign ingredients combine to create a battery that offers superior safety, cost, and is fully recyclable.

Our current generation battery design can provide up to 12 hours of energy storage. Packaged iron flow battery storage systems are cost-competitive with li-ion today, particularly in 6-8+ hour microgrid applications, where their operational flexibility and longer duration capability provide significantly enhanced project benefits and increased resiliency over li-ion storage solutions. In utility-scale applications where durations of 8-12 hours are garnering increased attention, the advantage is even more dramatic, with total cost of ownership ranging from one-third to one-half of comparable li-ion solutions. 

Sustainability – Looking Ahead

All signs point to rapid, continual growth in energy storage accelerating the energy transition and global urgency to address climate change. Long-duration storage has already been singled out for the key role it will play in meeting the needs of the energy transition. As the evolution towards long-duration energy storage accelerates, the next big milestone over the horizon will be dispatchable renewable electricity – energy that can be delivered around the clock and that can compete against fossil-fuel baseload generation in the marketplace.

That milestone is not as far off as might be imagined. Xcel Energy Colorado’s recent all-source competitive solicitation, for example, resulted in record low bids at $0.017/kWh for wind, $0.023/kWh for solar, and $0.03/kWh for solar-plus-storage. Pairing an energy storage resource like iron flow batteries with renewable energy projects at these prices would augment the earth-friendly value of a zero-carbon grid with the environmental and life cycle benefits of the underlying technologies.