Say you want to build a wind farm. You find a nice empty knoll in northern Vermont, where the breeze blows steadily and the neighbors don’t complain about sullied views. (A damn miracle, in other words.) You line up investors, get the right permits, and prepare to install your turbines. Then you hit snag: power lines. There aren’t enough in rural Vermont; they’re all in Boston, along with the people and their Teslas. So you’ve got a problem. The wind is blowing here, but there’s no way to get its green energy there.
Since 1889, when the US got its first long-distance power line (it traversed a whopping 14 miles), the grid largely has been set up for energy that’s consumed relatively close to where it is produced. There are exceptions—like hydropower that reaches cities from far-flung dams—but for the most part, it has been a century of linking coal and gas plants with people living nearby. But now, with wind farms dotting mountain ridges and solar plants sprawling in the desert, distance is more common.
The wires aren’t ready for it. Researchers at Princeton University estimate that the country’s high-voltage transmission capacity needs to grow by 60 percent in the next decade to meet its clean energy goals. “The grid that we have wasn’t designed for what we do with it now, let alone what we want to do with it, with all sorts of renewables,” says Seth Blumsack, an economist who studies the grid at Penn State University.
In many parts of the country, wind and solar are already the cheapest ways to produce energy, but transmission is a limiting factor, explains Kerinia Cusick, cofounder of the Center for Renewables Integration, a nonprofit that advocates modernizing the grid for green energy. That means that in places like rural Vermont, wind farm owners are frequently ordered to shut down when a healthy breeze is blowing—a move known as “curtailment”—because there’s too much power coming over the wires.
For plants that are yet to be built, the situation is even worse, because grid constraints mean backers must string new lines, and pay for them, before installing turbines or solar panels. Each year, hundreds of renewable energy projects stall in advanced planning stages due to delays in upgrading transmission lines and the cost of making those upgrades.
“There’s a very likely risk that’ll kill your project,” says Hudson Gilmer, chief executive of LineVision. Gilmer’s company attacks the problem from another angle: make the existing grid carry more power. Even when plans for a new line are approved, there’s no guarantee it actually happens. Nobody wants massive power lines draped over their backyard or across an endangered wetland. So Gilmer looks for ways to eke more power out of the lines where congestion is a big problem.
That’s possible because power lines generally are not used to their fullest. Limits on how much power the lines can carry are typically set in advance, and they're based on assumptions about physics and engineering that were made decades ago. They’re conservative—understandably so, in the interest of keeping the lights on reliably and safely. But Gilmer and others argue that technological improvements allow line owners to more closely monitor their system and push through more power. “We’re not suggesting that we don’t need those new high-voltage lines carrying renewables from the Dakotas or West Texas to urban areas,” Gilmer says, alluding to two of the nation’s most productive areas for wind power. For that, the country still needs new electron superhighways. But the idea is to get a little more out of the lines where there are bottlenecks, and make room for more of the renewables that are languishing in the queue.
LineVision specializes in a technique called dynamic line rating. One of the physical limits of power lines is the heat they generate as a current flows through them. Too much power and the line will start to sag as the wires get hot and expand, potentially sparking and causing a fire. But nobody actually monitors each line. The limits are based on assumptions meant to avoid a worst-case scenario. There are other factors that affect the line’s temperature—for example, the weather. Most days there’s a breeze blowing on the wires, and it cools them down—maybe just by a couple of degrees, but enough to theoretically carry more power. So Gilmer’s company installs sensors that monitor the lines for sagging, using lidar and other devices. It claims the technology can increase a line’s capacity by up to 40 percent.
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Renewables—which ebb and flow with the wind and the sun—add more uncertainty into how much power a line needs to carry. “Flexibility is the coin of the realm going forward,” says Carl Imhoff, a researcher at Pacific Northwest National Lab who studies so-called grid-enhancing technologies. Among them is a form of power steering for the grid. The way that power will flow through a grid is hard to predict—it changes depending on supply and demand, and it can leave certain lines clogged while others sit unused. The first step is knowing what’s happening: The method relies on a network of devices called synchrophasors—electronic sentinels that quickly measure changes in the power flowing through the lines. Those observations help grid operators understand where there’s congestion. That way, they can redirect power through a better route by applying a voltage to the lines, which serves to push or pull a current through them.
A form of that technology is used in the UK, where National Grid, which operates lines across the country, uses power flow devices to push energy from the renewable-rich north of England to power-hungry areas around London. Such tools would be especially useful in places like the Northeast US, explains Terron Hill, who directs clean energy development at National Grid’s US-based utility arm. That’s because the region is covered by a spider web of transmission lines—but often not as thickly as needed in places that are best for renewables. The wires in those areas are among the country's oldest, notes Hill, after returning from inspecting 80-year-old equipment that was due for maintenance.
It’s slow going. The utility has experimented with a variety of grid-enhancing tools, including dynamic line rating to improve capacity in the Hudson Valley and ferry renewable energy south to New York City. But for the most part, the utility follows a straightforward game plan for upgrading transmission: install more wires, even with the challenges of doing so. “You need to change the mindset away from ‘build build build’ to what’s best for customers and how to use your network more efficiently,” Hill says.
The reasons for that mindset get wonky, fast. The grid is complicated. The people who most often own and operate the transmission lines—including private utilities that answer to investors, as well as public entities—are often different from the people building renewable plants that will connect to them. The whole system is overseen by a tangle of planners and regulators, helmed nationally by the US Federal Energy Regulatory Commission, or FERC. When a utility wins approval to build a new power line, it’s usually part of a plan to handle demand from its customers—and it comes with a guarantee that the utility and its shareholders will recoup that investment and more. When a generator wants to hook up to the grid? That’s different. The entities that own the surrounding wires say what upgrades are required and how much it will cost, and the owner of the new solar plant or wind farms pays for it.
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Neither of these scenarios leaves much opportunity to make existing lines more efficient. Big investments in new lines mean bigger returns for utilities that put them up. In other words, it's more profitable to spend big. And while utilities may see potential in new technologies, they also come with risks, including safety and reliability problems, and investments in new people and training that might not pay off. “There is a great fear of failure,” says Blumsack of Penn State. “If you try something new and it fails, who pays for it?”
Utilities say their caution is rooted in reliability. Use a newfangled device to increase the capacity of the line and you may end up with a problem that results in penalties for the utility and higher prices for customers. “It puts us in a place not to innovate,” says Elizabeth Cook, general manager of advanced grid solutions for Duquesne Light Company, a utility in the Pittsburgh area. That’s why it’s important to test. The region isn’t a renewable hot spot or facing much congestion right now, but the utility is gathering data using a LineVision device. That way it can be prepared to raise the capacity if it needs to.
Incentives from agencies like FERC would help utilities try new technology and gather data, says Hill. The agency is considering such moves, along with new rules to incentivize more efficient grid planning, including cooperation among different players on the grid. Cusick, the grid improvements advocate, also hopes it will give generators more say over transmission improvements, so the default isn’t an expensive new line.
But what’s needed most, Blumsack says, is a better overall plan for the electric grid. Technologies that enhance the existing grid are one part of a much bigger puzzle. The topology of the old grid is now defunct, and it will take a lot to get it oriented the right way. That means efficiently building new wires not just where they’re needed today, but where they’ll be needed tomorrow—and using every technology we’ve got to get more power through them. Without that, the wind can blow and the sun can shine, but the US won’t be able to harness them.
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