By Published: Oct. 25, 2021

The DOE award will help accelerate research into flow batteries, which will help make the electricity grid more reliable and sustainable

The electrical grid typically runs smoothly and without incident, working in the background to provide essential power to homes, businesses and cities. But when the grid doesn’t function properly or shuts down because of severe weather, like what happened in Texas earlier this year, this failure can have catastrophic consequences.

A new flow battery developed at the University of Colorado Boulder has the potential to help solve some of the grid’s reliability challenges while at the same time bolstering the transition from fossil fuels to renewable energy sources like wind and solar.


Michael Marshak

To help accelerate this technology, the U.S. Department of Energy’s Advanced Manufacturing Office is awarding $4.14 million to Otoro Energy, a company started by CU Boulder researcher Michael Marshak based on technology developed in his lab at Renewable and Sustainable Energy Institute (RASEI) and patented with help from Venture Partners. The three-year grant also includes funding to Marshak’s lab, with some earmarked to help support student researchers from underrepresented groups under the SMART Program.

The grant is part of $17.9 million recently awarded by the energy department to help reach President Joe Biden’s goal of net-zero carbon emissions by 2050; three other companies specializing in flow battery technologies also received funding: Largo Clean Energy, TreadStone Technologies Inc. and Quino Energy, Inc. 

“We’ve become so reliant on electricity that it’s really a life-or-death thing, and reliability is incredibly critical,” said Marshak, a CU Boulder assistant professor of chemistry and fellow at RASEI. “There are so many different critical things that all require electricity and when it goes out, society can fall apart.”

Since 2018, Marshak and his collaborators have been working to develop a new, low-cost flow battery technology that can store large amounts of energy for long periods of time on the electrical grid. 

A flow battery differs from other types of batteries in that it stores energy in liquids, which are then pumped into fuel cells during charging and discharging to convert between electrical and chemical energy. 

Marshak’s battery technology uses water, organic chelating agents (compounds that help bind metal ions together and make them water-soluble), iron and chromium to store energy that can be used later, a helpful innovation for harnessing the power of fluctuating sources like wind and solar. 

“We need to be able to provide energy when the sun isn’t shining and the wind isn’t blowing,” Marshak said.

So far, most of Marshak’s batteries have been relatively small—about the size of a deck of cards. But in order to be useful for powering small businesses or, ideally, entire communities, his team needs to build batteries that are roughly the size of small shipping containers. The grant funding will help make that size increase a reality, Marshak said.

The goal is to build a five-kilowatt system that’s grid-tied and operates continuously, potentially for one or two decades nonstop."

“The goal is to build a five-kilowatt system that’s grid-tied and operates continuously, potentially for one or two decades nonstop,” he said. “We want to build something that we can bring or demonstrate to various customers and really take the technology to the next stage so we can go from five kilowatts to 500 kilowatts and ultimately toward megawatt and beyond scale systems.”

Marshak patented his technology in 2019 with help from Venture Partners, the CU Boulder department that helps transform university-led research into new businesses, products, services and partnerships. Venture Partners’ entrepreneurship programs, lectures and coaching sessions also helped Marshak found his startup, Otoro Energy, in September 2020.

Marshak is partnering with Massachusetts-based Raytheon Technologies, which will also receive some of the energy department funding, to validate and test the new technology.

“It’s a really neat opportunity to bring together a university invention, a small business and a large business to tackle a really important problem,” he said. 

Marshak’s technology helps solve some of the challenges associated with using other types of batteries to store energy on the grid. For starters, his batteries are safer than lithium-ion batteries, which can overheat and start fires. The technology also uses cheap, readily available, non-toxic materials that can be produced domestically.

They’re also more affordable and easier to scale than other battery types.

“The advantage of flow batteries is that the amount of energy stored scales with the volume of the liquids rather than the other fuel cell components, which provides a huge cost advantage for long-duration energy storage,” Marshak said. “The marginal cost of increasing battery capacity is the cost of the liquids, rather than any of the expensive electrical components.”

Above all else, the technology makes it possible to smooth out some of the differences between supply and demand on the electrical grid. Demand for electricity varies throughout the day and across the different seasons, and that doesn’t always match up with times when the wind is blowing or the sun is shining. 

That mismatch means the grid must continue to rely on traditional fossil fuel-powered plants, which can provide a constant stream of electricity to homes and businesses around the clock. Being able to store energy from renewable sources is the key to reducing reliance on coal and natural gas. 

Storing energy in batteries is also useful for preventing grid failures or interruptions caused by issues like severe weather or natural disasters, Marshak said.

“These batteries are going to be the critical infrastructure that supports grid reliability and resilience, but also allow for a future where we can get to 80, 90 or even 100 percent renewable energy,” he said. “In order to get anywhere close to that, we’re going to need to have energy storage, and this is the technology that’s going to do it.”