Cheap zinc air battery promises beefier power grid

Startup Eos Energy Storage promises its big batteries will be cheap enough to put in city centers to clear up bottlenecks on the grid and extend the range of EVs. But can they last 30 years?

Martin LaMonica Former Staff writer, CNET News
Martin LaMonica is a senior writer covering green tech and cutting-edge technologies. He joined CNET in 2002 to cover enterprise IT and Web development and was previously executive editor of IT publication InfoWorld.
Martin LaMonica
3 min read
A picture of how a large-scale energy storage system could be placed at commercial sites and provide power at peak times. Eos Energy Storage

Eos Energy Storage is developing a zinc air battery it claims will be able to clear up bottlenecks on the power grid by placing them at office buildings and shopping malls.

The energy storage startup before the end of March plans to close a round of funding from corporate partners which is expected to be at least $5.5 million. It plans to raise $20 million by the end of this year and start making its batteries at a pilot manufacturing facility next year, said President Steve Hellman.

Although it doesn't have a product on the market yet, Eos Energy Storage said its grid storage battery will be far cheaper than other technologies, such as lithium ion or sodium sulfur batteries now used for grid storage. Its target price is $1,000 per kilowatt and $160 per kilowatt hour. Over the batteries' lifetime, that would make it comparable to the cost of pumped hydro plants or natural-gas turbines, according to the company.

By tackling one of the most vexing problems with zinc air batteries--their ability to recharge effectively--the company projects it can build a battery that will last 30 years.

Energy project developers could install them next to power generation stations or at the edge of the grid network where there's a lot of congestion. The batteries will provide back up and allow companies, such as data center operators, to charge the batteries at off-peak times and draw on them during peak times to save money, Hellman said.

"The nice thing about the battery is that it's totally safe and can be installed in a New York City office building or downtown London, where they can relieve bottlenecks on the grid," Hellman said.

The technology can also be used for electric vehicles, too, but the company is focusing first on grid storage. Next year, it plans to test out megawatt-size batteries with a small number of utilities and corporate customers.

Armies of scientists and engineers are trying to design cheaper, safer, and longer-lasting batteries to improve the range of electric vehicles or firm up the grid. Storing intermittent solar or wind energy for many hours cost-effectively is sometimes called the holy grail of energy storage because it is so challenging.

An Eos Energy zinc air battery stack. The company plans to build full-scale prototype systems this year and next. Eos Energy Storage

Metal air batteries, such as zinc air batteries, have the potential to be the least expensive type of battery, according to the Electricity Storage Association. Zinc is considered safe and abundant, too. But recharging these batteries has traditionally been difficult and inefficient.

Eos Energy has overcome some of the common problems with zinc air rechargeable batteries by redesigning most components of the battery, Hellman said. The electrolytes traditionally used mix with CO2 from the air and cause damage on the zinc anode during charging and recharging. To address that problem, Eos Energy engineers use a different type of electrolyte and eliminated the traditional membrane on the air electrode, Hellman said.

"When (company founder) Steve Amendola filed for the original patent (behind the company's technology) in 2004, he started not with a science idea, but with a business idea," he said. "He combined all sorts of processes from different industries."

The company's goal is to have a battery able to charge and recharge 10,000 times without degradation, which would be a clear differentiator with other zinc air batteries. So far, it's demonstrated more than 2,000, according to a recent presentation.

Another company pursuing zinc air batteries is ReVolt Technology, but since it is targeting mobile applications, such as consumer electronics and EVs, it is targeting between 500 and 2,000 charge cycles.

One battery expert said that Eos Energy still needs to show performance data and demonstrate that their zinc air battery can be comparable to lithium ion and lead acid batteries in efficiency, or the amount of energy lost during a charging cycle. "A lot of people have worked for a long time on rechargeable zinc-air and (the efficiency issue) hasn't been cracked yet," Jeff Dahn, professor of physics and chemistry at Dalhousie University, told Technology Review.