The Race to Build a Better Battery for Storing Power
Long-term, utility-scale storage would turn solar and wind energy into on-demand sources of electricity
There’s the battery in your watch. There’s the battery in your mobile phone. And then there’s the battery at Green Mountain Power’s Stafford Hills solar farm in Rutland, Vt.
The lithium-ion gargantuan is housed in two trailer-truck-size green metal containers. It sits atop a 10-acre former landfill and captures electricity from 7,722 nearby solar panels—enough to power 2,000 homes on a sunny day. What’s revolutionary about this system isn’t the solar farm; it’s the size and purpose of the battery, which offers 3.4 megawatt-hours of storage, enough to supply backup power to about 170 homes for a day, if needed.
The rap on solar and wind is intermittence—they don’t produce power when the sun isn’t shining or the wind isn’t blowing, making them unreliable as the primary source for power grids. But if vast amounts of renewable energy—say, enough to power entire cities—could be captured and stored in giant batteries and deployed when needed, that downside would fade away.
This has been the “missing piece” in the renewable-energy revolution, says Venkat Srinivasan, director of the Energy Department’s Argonne Collaborative Center for Energy Storage Science. But it’s starting to come into view, thanks to the scale and progress of current research and real-world applications such as Green Mountain Power’s.
Green Mountain’s project puts it in the vanguard of power companies that are showing that utility-scale battery storage can be technologically and economically viable—depending on the scale and how it is used.
Like all utilities, Green Mountain faces issues meeting “peak demand,” the high-use period, typically in the early evening, when people return from work and school and crank up air conditioners and energy-hungry appliances.
Many U.S. utilities fire up natural-gas-powered generators to help their baseload plants meet peaks, often imposing hefty surcharges on customers to offset the extra generating costs. Green Mountain instead stores energy from its solar-and-battery combination to meet peaks—shaving as much as $200,000 an hour off demand charges for its 265,000 residential customers, according to the utility. Green Mountain, which says it invested $12.5 million in the project and received a $285,000 government grant, benefits in that it doesn’t have to build additional plants to meet peak demand and gets a public-relations boost among its green-leaning customer base.
“It’s green energy, not fossil fuels,” says Josh Castonguay, the utility’s vice president of innovation.
The Stafford Hills facility, which opened in 2015, is one of almost 200 utility-scale systems or utility-scale experimental projects operating in the U.S., according to the Energy Department. Some are providing backup power capabilities to military installations, government agencies and universities that have renewables in their energy mix. Others are being deployed by businesses seeking to go green while paring electricity costs and providing an uninterruptible power supply. Electric-car maker Tesla Inc. has gotten into the act, supplying heavy duty lithium-ion units that come in large white modules or “battery blocks” that can be linked together, depending on the desired capacity.
Still, although lithium-ion batteries are useful for short-term storage and as a fill-in during short-term power outages, they are too expensive per kilowatt-hour to store energy for longer periods. So the push for cheaper technologies continues.