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It won’t be cheap, or easy. But it’s technically feasible for the United States to get 80 percent of its electricity from renewable sources by 2050, according to a new report from the National Renewable Energy Laboratory. And no major breakthroughs are needed to do it—the report considered only currently commercially available technologies, says Ryan Wiser, one of the authors. (We consider how Germany might reach a similar goal in our feature, The Great German Energy Experiment.)

The massive, 850-page, four-volume, NREL report isn’t a prediction of how much renewable energy will actually be used—that depends on lots of variables. Instead, it looks at whether it’s technically feasible for the United States to run its economy on renewable sources, many of which—such as wind and solar—are intermittent and difficult to predict. Its answer is yes, the authors say. And the main reason is that the United States is a large country, with large and varied sources of renewable energy. (The report assumed that 50 percent of the country’s power would come from wind and solar. The rest would come from sources such as biomass and hydroelectric and conventional geothermal, which are not as variable. Here’s an interactive breakdown of how the mix of power sources could develop.)

NREL’s interactive shows how renewable power sources could develop.

The most straightforward way to accommodate variability is to store power for when it’s needed, but most types of energy storage are expensive or geographically limited, and building enough batteries to run a cities and factories at night on power generated during the day from solar panels—at the scale of 80 percent renewables—might be impossible, at least with the commercially available technology the study takes into account. The report posits that energy storage amounting to about 10 percent of generating capacity will be needed, still a large but possibly feasible amount.

But mostly variability would need to be handled in other ways. One is by taking advantage of geographically distributed resources. By building transmission lines, it’s possible to transport power from areas where it’s sunny and windy—as the areas vary from hour-to-hour or season-to-season—to areas where it’s needed. “The renewable resource is large and diverse enough and geographically distributed enough to do this,” Wiser says.

Demand-response programs could help, too. Using smart-grid communications, utilities could send signals to electricity consumers to reduce demand during cloudy, windless periods, in return for some sort of compensation. This could be done automatically with smart appliances—now starting to become available—that can change their operation depending on pricing signals from the utility. Utilities could also send signals to increase electricity consumption, such as by signaling electric cars to start charging.

Technical feasibility is one thing. But all sorts of practical problems could arise that could prevent renewables from producing 80 percent of U.S. electricity. Landowners often resist transmission lines; unforeseen environmental problems could arise; and the costs may deter politicians. The researchers estimate it could be done at a cost of between 2.5 to 5 cents per kilowatt hour on top of what electricity prices would have been using conventional power production. Electricity costs on average about 10 cents per kilowatt hour in the United States.

The best way to keep the costs to the low end is to invest in R&D, Wiser says. The researchers considered several variables that impact cost, including the cost and difficulty of transmission and of integrating intermittent resources. But they found that the biggest impact on cost came from different assumptions about how quickly renewable energy technology improves. Major breakthroughs aren’t needed to keep the additional cost to 2.5 cents per kilowatt hour, but if progress stagnates, the costs will be on the high end. If breakthroughs do happen, costs could be lower than 2.5 cents per kilowatt hour.

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Tagged: Energy, energy, renewable energy, solar, electricity, wind, NREL

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