Electricity grids that incorporate storage for power sourced from renewable resources could cut carbon dioxide emissions substantially more than systems that simply increase renewably sourced power, a new study has found.
The study, published today in the journal Nature Communications, found that storage could help make more efficient use of power generated by sources such as wind and solar and could help power grids move away from relying on fossil fuels for energy.
“With solar and wind, you can’t flip them on immediately when you need more power,” said Ramteen Sioshansi, a co-author of the study and professor of integrated systems engineering at The Ohio State University. “So the more renewable energy you put into your system, the greater your need to be able to forecast when those energy sources might be available — unless you can find an affordable, reliable way to store that energy.”
The study was among the first of its kind to evaluate the role energy storage might play in making renewable resources more reliable on a grid-wide basis.
The researchers looked at the power grids in California and Texas, then modeled the ways in which energy storage might make better use of energy from renewable sources — and the ways in which storing energy from renewable sources might affect the amount of carbon dioxide the energy grid pumps into the atmosphere.
They found that in California, without energy storage, one-third of the renewable energy could be lost or never collected in the first place. And adding energy storage technologies — batteries and the like — could reduce carbon dioxide emissions by 90 percent.
Under the study’s models, holding energy from renewable sources also made the system much more efficient: Just 9 percent of renewable energy was lost.
In Texas, a state that generates a smaller percentage of its energy from renewable sources than California, the researchers found that adding energy storage technologies to the grid could reduce carbon dioxide emissions by about 57 percent. Under that model, just 0.3 percent of the renewable energy in Texas’s system would be lost.
“Renewables are good, but they have their own challenges,” said Maryam Arbabzadeh, a research fellow at the University of Michigan and lead author of the study. “The sun is not always shining; the wind is not always blowing. Sometimes the amount of solar and wind power doesn’t match the demand. As we think about how to de-carbonize our systems, a combination of all of these technologies could be beneficial for the system to minimize carbon dioxide emissions.”
Though it is not yet a problem throughout much of the United States, which still largely relies on coal and natural gas for energy, some countries and states — including California — have begun producing more energy from renewable resources than the grid is using. That means that some energy from renewable resources is either lost forever or never collected in the first place.
“One of the unique characteristics of electric power systems is that you have to maintain supply and demand balance at all times,” Sioshansi said. “The analogy is if you have an airplane with 109 seats, you have to have exactly 109 passengers — if 108 or 110 passengers show up, then everything falls apart.”
Maintaining that exact balance of the supply of energy with the demand for it makes producing a reliable power grid technically challenging. Over the last century, power companies have figured out how to adjust the output of energy from a coal- or natural-gas fired plant when demand increases, Sioshansi said: They simply fire up or power down a turbine.
Power companies largely know they need to hold energy from renewable sources in order to make those sources work for their grids — but so far, batteries and other storage options have been costly.
Sioshansi, who chairs a subcommittee on energy storage for the U.S. Department of Energy, said this research sets the stage for future studies to eliminate fossil-fuel sources from the energy grid. Future models, he said, could predict what might happen to fossil fuel emissions if a state or country combined a greater investment in renewable energy sources with different energy storage solutions and policies like carbon taxes.
“This study focused on a very narrow application of energy storage for systems that are adding more renewable sources to their energy supply,” he said. “Looking forward, we could perhaps make a more complex model to show how to achieve greater reductions in carbon dioxide emissions.”