New battery technology for storing electricity from renewable sources that could provide grid-stabilizing power for up to 100 hours — a substantial improvement over the 4-to-6-hour capacity of existing technology — is coming to Xcel Energy’s Colorado power network, the company announced this month. 

Xcel said it is partnering with Form Energy, an energy storage technology company, to build a 10-megawatt commercial demonstration project at the soon-to-be shuttered Comanche power plant site near Pueblo.

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“With increasing amounts of renewable energy generation, the electric grid now faces a challenge: how to manage the multi-day variability of renewable energy without sacrificing reliability or cost,” said Mateo Jaramillo, co-founder and CEO of Form Energy in a statement to The Denver Gazette.

Weather-dependent generating resources are by nature intermittent — and that’s not good for a power grid, which requires stable energy every day all year long.

Form’s technology uses rusting iron that can be regenerated and recharged to generate electricity, an improvement on a phenomenon well known to physics. Metal-air batteries have been experimented with for years. Form has developed the technology into what it says will be a utility-scale solution to the intermittency of power generated by wind turbines and solar panels.

“As we build more renewable energy into our systems, our partnership with Form Energy opens the door to significantly improve how we deliver carbon-free energy so that we can continue to provide reliable and affordable electric service to our customers well into the future,” said Bob Frenzel, chairman, president and CEO of Xcel Energy.

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Most utility-scale battery technologies on the market can only provide 4 to 6 hours of energy storage at full rated power. While this is adequate for some circumstances, recent severe weather events – ranging from heat waves to cold snaps to thousand-year rains – have hampered the electric grid.

Utility-scale lithium batteries can charge and discharge very quickly, which for grid use provides “peaking” capacity that can quickly pick up spikes in electrical load to help keep the grid stable. But they are short-lived and also expensive, according to Form.

When renewable generation fails for longer periods, a steadier flow of electricity is needed that’s usually provided by fossil fuel-fired generators.

Form said the battery bank footprint uses about half an acre of land per megawatt and higher density configurations could provide more than 3 megawatts per acre.

Jaramillo said its system will be able to store energy at less than 1/10th the cost of lithium-ion battery technology and could be online by 2025.

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