Last week, some rare positive environmental news reached the public eye: Nearly half of all the new, large-scale electric power generation installed last year use renewable energy sources, according to the Energy Information Administration. The government agency reports that of the total 25 gigawatts of capacity installed in 2017, about 12 gigawatts of that amout came from clean energy—plus an extra 3.5 gigawatts of small-scale solar, like rooftop panels.
This report follows in tandem with another good energy update: Almost all of the power plants shut down last year used fossil fuels as their source of energy. And most of those plants used coal, largely recognized as the most carbon intensive fuel type. And the good news keeps on rolling. We should expect this trend to continue, since the agency reports that power companies plan to retire nearly 10 gigawatts of coal power in 2018.
So lots of good clean energy is coming our way. But are we ready for it? Without the right infrastructure in place, many experts argue, we may not be able to capture and transport all the energy these new installations are capable of providing.
The root of the issue lies in the way we receive clean energy. Unlike fossil fuel plants, wind and solar power are intermittent sources of energy. If the wind isn’t blowing strong enough or there are too many clouds (or a solar eclipse), the supply of electricity might not meet the demand for it. On the opposite end, if there’s strong winds or persistent sunlight, the supply could exceed the capacity to capture and use it.
One issue that researchers are trying to solve is what’s known as curtailment.. This occurs when the renewable energy supply is so great (perhaps from a series of super sunny days) that the supply exceeds the capacity of the transmission lines that carry electricity from a power plant to your outlets.
“We can make do with the transmission infrastructure we have for now, but the existing infrastructure was not built considering the changing energy landscape,” says Jennie Jorgenson, one of the authors of a 2017 study on wind curtailment from the National Renewable Energy Laboratory.
In the report, researchers from NREL modeled a scenario in which wind energy provided 37 percent of the needed electricity in the western United States, and analyzed the feasibility of increasing wind energy consumption. (The most recent estimate from 2016 puts national wind energy consumption at 5.5 percent.) “We didn’t identify any reliability concerns with this much wind on the system,” Jorgenson says. “But without expanded transmission capacity, we observed high amounts of wind curtailment.” That means that the wind energy produced isn’t really going anywhere it can be used. It’s essentially “wasted renewable energy,” since that energy has to come from fossil fuels instead.
To attempt to address curtailment problems in Texas, which has installed the most wind energy generating capacity of any state, the Public Utility Commission built a $7 billion system of transmission lines a few years ago. Known as the Competitive Renewable Energy Zone (CREZ), it spans 3,600 miles from the windy west to the more populated eastern and central regions of the state, carrying enough electricity to serve approximately 1,700 homes.
“We wouldn’t have as much wind [energy] in Texas if we didn’t build out CREZ,” says Joshua Rhodes, a postdoctoral research fellow at the University of Texas at Austin’s Energy Institute. But at the same time, Rhodes notes, the system was far from perfect from the beginning. The transmission infrastructure could hardly keep up with the power produced by new wind farms across the state. The transmission lines were at full capacity not long after the project was completed. (Though that was only late at night, when the wind blows the strongest and produces the most electricity.)
But Rhodes notes a possible solution to the problem. “During those hot summer days when the wind is not blowing, there’s lots of sun hitting the ground,” he says. “There’s plenty of room on those transmission lines in the summer for solar to feed into it. They have complementary production profiles, so we make it solar in the day, and wind at night—they don’t really produce at the same time very often.”
This dual-functioning CREZ infrastructure could prove incredibly useful. Solar power in the state is growing quickly, projected to grow by nearly 5,000 megawatts in the next five years, according to the Solar Energy Industries Association. Nationwide, new technologies like dynamic electric grid simulations have helped increase the rates of renewable energy usage by adjusting to supply and demand throughout the day.
But there’s another big thing infrastructure piece missing: cheap storage devices. “The real thing that would allow a whole lot more renewable generation on the same amount of transmission would be cheap battery storage,” Rhodes says. “Then you can send power along the lines whenever the wind and solar are making it, and when they’re not, you can discharge the batteries.”
Large-scale battery storage is one of the newer storage solutions out there. And, researchers argue, is a far more plausible solution than other clean energy storage solutions of the past. For example, pumped hydro storage has been around since the early 20th century, but it has failed to prove itself to be functional or economical. In this type of storage, using the excess electricity from a turbine, water is pumped from a lower-altitude reservoir and stored in a higher altitude one. When the water flows back down through a turbine, it generates electricity.
“The challenge is that you need a certain kind of geographic site,” David Hart, the director of the Center for Science, Technology, and Innovation Policy at George Mason University says. Add to that the environmental concerns and the long permitting process to build a hydro plant, and it becomes harder to construct new facilities.
But right now, this type of dual functionality doesn’t fit into the way current energy grid systems are set up, says Hart. You are either one of the other (an end user or a power plant) and a battery is both.
Absent any national climate and renewable energy policy in the US, the good news is that the price of storage technology is dropping, making it a more economically feasible solution. Grid-scale batteries use the same technology as the battery you’d find in an electric vehicle, benefitting from the same economies of scale. “The more electric vehicles you have, the lower the price of the batteries,” Hart says.