A California company called Advanced Rail Energy Storage (ARES) has come up with what seems like a particularly ingenious solution that relies upon simple gravity and a venerable old-school technology: the railway train.
ARES' system involves building a small electric railroad that draws excess electricity from a solar- or wind-powered plant, and uses it to drive trains loaded with heavy rocks or weights up a grade. Then, when that energy is needed later, the cars will roll back down the slope. On the way down, the trains' motors use regenerative braking — the same technology that powers streetcars and cars like the Toyota Prius — to generate electricity, which goes into the grid.
Our Current Need
The United States still relies upon fossil fuels, primarily coal and natural gas, to generate two-thirds of the nation's electricity. And if you're worried about climate change, that's a big problem, because those power plants are the single biggest source of the planet-warming greenhouse gases that we're spewing into the atmosphere, accounting for 30 percent of our total emissions. That's why, if we're going to stave off or at least mitigate the destructive effects that climate change eventually could have, transitioning to renewable, low-emissions energy sources is an important step.
But that brings another problem: How to ensure a reliable, continuous supply. The sun goes down at night, and sometimes goes behind the clouds during the day; winds aren't always blowing. That means coping with fluctuations in electrical generation that don't necessarily match up with consumer demand. We may have a shortage of electricity at some moments, at other moments, more than we can use. That wouldn't be an issue, if only we had a way to store renewable energy so that we could use it when we need it.
In an effort to solve the problem, researchers have been looking at solutions ranging from storing energy in caverns full of compressed air to minivan-sized batteries. Another idea is using a pumped hydroelectric system, similar to the ones used by hydroelectric dams, in which excess electricity from solar or wind installations is used to pump water uphill to store store potential energy , which can then be released by letting the water flow back downhill to drive turbines.
The ARES Innovation
The company recently received the go-ahead from federal Bureau of Land Management officials to build its first commercial 50-megawatt storage project on government-owned land in southern Nevada. The 106-acre facility will include a 5.5-mile (8.9-kilometer) railway on a 2,000-foot (610-meter) grade, which will be traveled by trains loaded with 9,600 tons of weight. The project is scheduled for completion in early 2019, according to a regulatory filing.
While you might think of trains as big, old-fashioned, dirty technology, ARES vice-president of operations Francesca Cava says that using a railway system for energy storage is surprisingly clean from an environmental standpoint. Since the trains will be fully electric, they won't generate any emissions, and the system doesn't involve using batteries filled with potentially hazardous chemicals. And unlike pump hydroelectric power, it doesn't require diverting a lot of water from a river and potentially causing environmental impacts.
"This is so simple, that we don't have to wait until the next big scientific discovery to solve the storage problem," Cava explains. "It will work for a long time, and it's cost effective."
The plant will cost $55 million and is designed to be big enough to provide what's called ancillary services — that is, helping electricity producers adjust electricity input and output, "so the grid doesn't blow up," Cava says.
Eventually, though, ARES technology could be scaled up to perform load-shifting: storing electricity at off-peak demand times and then providing it when it's needed. That would require a 500-megawatt facility costing hundreds of millions of dollars, Cava says.
To learn more about ARES' inspiration, check out CEO Jim Kelly in this video from a few years back, where he laid out his vision for the company's mission: