It's no secret that wind farms and solar plants have a reliability problem, and that a clear way to conquer that hurdle is to deploy batteries that store power and deliver it to the grid when needed.
But there are two obstacles limiting the success of that solution—the enormous cost and low durability of today's batteries.
Now, engineers at the City University of New York's Energy Institute in Manhattan say they found a fix: a nickel-zinc battery technology that is just as cheap as short-lived, lead-acid batteries and just as long-lasting as lithium-ion batteries, one of the costliest technologies on the market.
"There was a giant hole in the middle" between the top battery types, says Eric McFarland, a chemical engineering professor at the University of California, Santa Barbara and a consultant for the institute.
The four-year-old Energy Institute is in the midst of launching a company called Urban Electric Power that will commercialize its nickel-zinc battery technology. McFarland says the startup expects to create about 20 local jobs by the end of this year.
Perched in a clearing, the firm's Nickel-Zinc Flow Battery system will connect by cable to rows of wind turbines or fields of solar panels, storing up electricity generated on windy nights or extra-sunny days and sending power to the grid in peak periods.
The allure for developers is the return on investment, says McFarland. "If you have batteries, then you can strike a better deal [with utilities] because you're providing more reliable power around the clock."
Further, the upfront cost of the nickel-zinc system is expected to be less than other energy storage options.
The institute's kilowatt-hour nickel-zinc battery costs between $300 and $500, or as much as $100,000 for a 200-battery system that has a life of up to 15 years. Within a year, however, that kilowatt-hour price is expected to fall to $200 as the technology improves, the institute says. That would make it the same price as a lead-acid battery, which lasts only a year.
Lithium-ion technologies, by contrast, can cost up to $1,200 per kilowatt-hour.
Clean energy "is already expensive, and if you add expensive battery systems to that, then it's not economical," says Sanjoy Banerjee, the institute's director and a distinguished professor of chemical engineering at the City College of New York.
"To make it really work, it has to be very cheap."
The Basement Experiment
The Energy Institute's battery technology is currently in the prototype phase. In a musty basement at the City College of New York's century-old campus in Harlem, a cluster of 36 rectangular batteries are huddled on metal racks. Each is about the size of a small suitcase and can supply 1 kilowatt-hour of energy, enough to light up ten 100-watt light bulbs.
Black and red wires unfurl from the tops of the batteries and connect to what the institute calls the "advanced battery management system," a web-based program run on a single computer that serves as the battery command center. Through that program, engineers control when to recharge the batteries and when to release their power. The entire network is connected to the building's electrical system, which runs on fossil fuel, nuclear and hydroelectric energy.
From this basement room, the 36 kilowatt-hour system can supply about 5 percent of the building's energy needs during hours of peak electricity demand and recharge at night when the students have left.
The Energy Institute hopes to scale up the demonstration to 200 suitcase-sized batteries later this year, which would supply up to 30 percent of the building's energy use and save the college at least $6,000 in monthly energy bills.
The Challenge of Zinc Batteries
Banerjee says the research team chose zinc for its batteries because the metal is cheap, nontoxic and widely accessible.
It's only one of about a dozen startups using zinc for grid-scale battery storage, among the hundreds of companies and labs working in the space.
Why so few?
The reason is a stubborn problem called "dendrite formation," says Banerjee. He explains that zinc, which is used in disposable battery brands like Duracell, forms dendrites, or branch-like structures, every time a battery is charged and recharged. Those dendrites quickly build up and cause the batteries to short out.
Banjeree says he and his team of engineers found a way to tame the dendrites.
The core of each battery, a series of flat metal rods, sits in an aquarium filled with constantly circulating water-based liquid called the electrolyte. The flow helps to smooth out the zinc dendrites and to extend by 10 times the battery's life. With this setup, batteries can be "deep-cycled" 3,000 to 4,000 times, which means they can last for 10 to 15 years with daily use.
Since 2008, the Energy Institute has received more than $20 million in funding from the Department of Energy (DOE), the New York State Energy Research and Development Authority, Con Edison, Mitsubishi and the Nuclear Regulatory Commission. Among the awards is a $3 million grant from the DOE's Advanced Research Projects Agency-Energy, a government agency that bankrolls cutting-edge technologies.
If successful, the Energy Institute's technology would "put the U.S. on a path towards creating a smarter grid with low-cost batteries that are capable of storing enough electricity to power homes, cars and cities," says an ARPA-E description of the project.
The Energy Institute is also developing another battery technology that would use zinc and manganese dioxide. Banerjee calls it the "second generation" of its nickel-zinc technology that would be cheaper and even longer-lasting. The institute plans to launch a basement-level demonstration of the new technology within a year.
In the meantime, Urban Electric Power is set to start raising private investment this summer. McFarland, the institute consultant, says it is already looking for manufacturers in New York and across the country and the world that could mass-produce the zinc-nickel batteries. It aims to lock in supply contracts with at least five customers before formally launching the company.
Beyond the Renewables Industry
McFarland says they are looking beyond the renewables industry for potential clients, because inconsistent policy supports for clean energy in the United States make it challenging to assess demand for its batteries.
"I wouldn't want that to be my only customer."
So Urban Electric Power will also target owners of large industrial buildings that consume huge amounts of power during the daytime, when demand for electricity is at its peak and most expensive. Utilities charge these industrial customers a hefty fee, known as a demand charge, to offset costs that utilities incur to supply massive bursts of energy.
Those charges account for as much as half of a company's monthly utility bills, McFarland says. By hooking the nickel-zinc batteries to a building's electricity system, the batteries can pull power from the grid during off-peak hours and deliver it back to the building when demand picks up. Factories that get peak power from batteries—and not the utility—would slash their monthly demand charge.
"Demand-charge reduction is a developing market," McFarland says. "It doesn't really entirely exist today, but there's increasing motivation to make use of it" as companies seek to save energy and money.
The Energy Institute joins a rising number of energy storage ventures hoping to capitalize on the need for more reliable renewable electricity and more efficient fossil fuel systems. In the past 12 months, storage technologies have raised $630.5 million in investments, according to Cleantech Group, a market research firm.
While it's "relatively easy" to attract investment for early-stage technologies like the Energy Institute's demonstration project, however, it is much harder to secure funds for manufacturing, says Haresh Kamath, program manager for energy storage research at the nonprofit Electric Power Research Institute.
"Many investors ... would rather put their money into something that doesn't require quite so much capital," such as prototypes, Kamath says. "It's very hard to get the capital that [startups] need to commercialize."