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Illustrations by Hanna Nordwall

Improving energy storage is key to the renewable grid. Here’s how CU Engineering is getting us there.

CU Engineering researchers are working to solve one of the biggest challenges facing renewable energy: affordable, reliable energy storage.

In 2025, solar and wind accounted for roughly 90 percent of newly installed U.S. power capacity, according to a report by the Federal Energy Regulatory Commission. While renewables offer the most affordable source of new electricity and deliver emissions-free power, their dependence on weather and daylight makes energy storage essential to grid reliability, said Mike Toney, a professor of chemical and biological engineering.

“There’s a need for inexpensive and safe energy storage to support renewable energy,” Toney said. “Better batteries will be critical to shifting our energy infrastructure away from fossil fuels.”

Challenges

Current battery technologies rely on materials with ethical, geopolitical and safety concerns, with end-of-life disposal posing environmental risks, Toney said.

Lithium-ion batteries are popular because they’re affordable, widely available, and can smooth out short-term fluctuations. But as more renewable energy is added to the grid, these batteries will be less suited to its demands, said Bri-Mathias Hodge, a professor of electrical, computer and energy engineering who uses computational simulations to study reliable and economical future power systems.

Hodge said that because solar and wind output change rapidly with weather and time of day, within the next decade the grid will need longer-duration storage capable of delivering electricity instantly.

“Most researchers agree it needs to be longer than 10 hours,” Hodge said.

Beyond lithium

Toney’s lab is working on one possible solution. He and his team study how electrolytes function in aqueous zinc-metal batteries, which use widely available materials — unlike lithium-ion batteries. They’re also researching sodium-ion batteries, which are inexpensive and also use abundant materials.

Associate Professor Chunmei Ban’s research focuses on what she calls “beyond lithium” battery technologies, including sodium and solid-state batteries for renewable energy and electric vehicles.

Ban, a mechanical engineer, explains that much of the supply chain for lithium batteries, including raw materials and manufacturing equipment, is concentrated outside the U.S. This makes it difficult for the U.S. to independently produce lithium batteries at scale and creates vulnerabilities in resource and technology access.

“Developing new battery materials is a very challenging and resource-intensive process,” Ban said. “Progress takes time because creating and testing new materials requires extensive modeling, material optimization and trial and error. Out of millions of possible compounds, only a small number are currently identified as suitable for batteries.”

Despite these challenges, Ban’s lab has successfully developed several new materials in under three years. They are being commercialized through her lab’s spinoff company, Mana Batteries.

These materials, such as new electrolytes for sodium batteries, are now being used in manufacturing and could support a wide range of applications — from grid-scale energy storage to vehicles and electronics.

“The discovery, design and synthesis of new materials present exciting opportunities for developing long-lasting and low-cost energy storage solutions for grid and vehicular applications,” Ban said.

Kimberly See will join CU ������ý���� faculty in August 2026 as a Renewable and Sustainable Energy Institute fellow with an appointment in chemical and biological engineering. The See Group is looking to replace metals like cobalt and nickel with more sustainable options such as iron in lithium-ion batteries to lower cost while improving safety.

“Current lithium-ion technology provides the energy density needed for diurnal cycling (charging when solar power is abundant and discharging at night), but high costs and safety concerns limit widespread grid deployment,” See said.

Beyond batteries

Another possible solution can be found in Ankur Gupta’s lab. Gupta is researching supercapacitors — energy storage devices that charge quickly and last longer than traditional batteries.

While supercapacitors are not known for storing energy for long periods, they could help manage grid fluctuations. During sudden spikes or drops in electricity demand, supercapacitors could rapidly supply or absorb power to stabilize the grid.

“The primary appeal of supercapacitors lies in their speed,” said Gupta, an assistant professor of chemical and biological engineering.

In the end, which type of storage technology prevails all boils down to cost, Hodge said. “The uncertain costs of future storage technologies make it impossible to predict which technology will ultimately dominate.”