Read Blackburn’s report, “Matching Utility Loads With Solar and Wind Power in North Carolina”

Read Duke Energy’s response to Blackburn, “Wind and solar providing all our energy? Now that’s a kick”

File this information away for the next time you hear that wind and solar power can’t replace the giant electricity-generating plants because the sun and wind are “intermittent” and therefore unreliable.

They are intermittent when considered separately, says John Blackburn, an energy economist with top-flight credentials. But taken together, solar and wind are complementary sources of potential powerhighly reliable and relatively inexpensive powerthat could supply most of North Carolina’s future electricity needs.

That’s because the sun shines brightest during the day and the summer, while the wind blows hardest at night and in the winter. When one ebbs, in other words, the other picks up and fills in for it, Blackburn says. This is especially true in North Carolina, which has plentiful quantities of sun and wind.

It’s more than a theory. Blackburn’s new study of available solar and wind sources demonstrates how the two, working in tandem, could someday supply more than three-fourths of the state’s electric power. That is, if the public utility companies and state leaders would get behind them.

A retired Duke University professor and chancellor, Blackburn returned to Durham five years ago from Florida, where he had immersed himself in the economics of alternative energy sources. He quickly discovered that while much of the world and many other states were turning to wind and solar power, North Carolina was not. Our utilities, principally Progress Energy and Duke Power, were clinging to coal-fired and nuclear plants, with more of both on the companies’ drawing boards.

When Blackburn asked why, he says he kept hearing the “intermittency” argument: The utilities considered the big baseload plantsthose designed for continuous operation (setting aside the downtimes needed for repairs)the only viable method of supplying electricity in bulk.

Wind and solar were viewed as boutique itemsfine for a building here and there but undependable on a large scale.

So Blackburn went to work. Initially, his objective was modest: He wanted to prove that wind and solar could work together to steadily supply electricity. How much electricity they could provide would be a question for another day.

He collected data from three representative wind sites, in the mountains and at the coast, and three solar sites around the state, on each of 123 days during January, April, July and October in 2008. The result: Solar and wind balanced out at high enough levels to generate power steadily at most times. With a small auxiliary power sourcesay, hydropowerno problem of intermittency would’ve occurred.

But as he worked on the study, around the world wind and solar technologies were rapidly advancing and their costs dropped, making wind the cheap alternative to, and solar much more competitive with, traditional power sources.

Meanwhile, U.S. Department of Energy studies revealed much stronger wind currents than previously estimated, particularly in the Plains states (Texas and Oklahoma, for example) but also in the mountain states, coastal areas and offshore. Add modern high-efficiency wind turbines that stand up to 400 feet tall, and wind’s potential was spiking: The N.C. State Energy Office issued a report last year that said 20 percent of the state’s electric needs could be met with wind, Blackburn noted.

Blackburn thinks 20 percent was a conservative figure, and his study suggests that it can be doubled in the near future, setting the state on a course to achieve 40 percent of its electric generation from wind. Because wind and solar are complementary, 40 percent from wind would allow another 40 percent to be generated by solar without any problem of intermittency.

“The 40 percent [target] is a stretch, but it’s not out of the question by any means,” Blackburn says.

For the near term, though, Blackburn thinks the takeaway from his study should be that renewable energy sources, including hydropower, biomass, wind, solar and energy conservation, can quickly replace all of the coal-fired electric plants in North Carolina and obviate the need for additional nuclear reactors.

The two utilities don’t agree.

“Renewable energy sources have a growing importance in our portfolio,” says Jason Walls, a spokesperson for Duke Energy, “but [they] do not replace the need for baseload generation” that operates continuously.

Duke currently uses coal plants for half its power generation, with another 48 percent from nuclear power, Walls said, adding that a “balanced portfolio” of nuclear, coal, renewables and conservation is necessary to assure that Duke’s customers have reliable electricity at all times for the lowest price.

Mike Hughes, a spokesman for Progress Energy, said intermittency “is not an insignificant issue” given the need for reliable power.

Hughes added that he was “in no way dismissing” Blackburn’s study or “the momentum that’s already building for solar and wind.” But, he maintained, Blackburn’s “assumptions” that each might supply 40 percent of the state’s power needs “is far in excess of anything that’s been demonstrated anywhere.” That much wind power could require more than 5,000 3-megawatt turbinesthe biggest ones made, Hughes noted.

Both Duke Energy and Progress Energy have small solar power initiatives underway, and they’re working together on a test of wind power in the Pamlico Sound using up to three turbines. But both also plan to stick with coal and build more nuclear reactors.

And in March, when the companies presented their long-term plans to the N.C. Utilities Commission, Chairman Ed Finley urged them to move faster on nuclear plants, not on renewables, according to coverage in the Charlotte Business Journal. Finley said that, at a potential cost of $11 billion per reactor, neither company is making quick headway on nuclear. His suggestion: Why not do a regional project and build one reactor jointly for $5.5 billion each?

Executives from both companies said they’re exploring a joint approach on nuclear power.

Nuclear plants generate highly radioactive wastes for which the nation, as yet, has no repository. Coal plants contribute to air pollution and climate change.

“To get them to phase out coal as quickly as possible,” Blackburn says, speaking about the utility companies, “but not let them build any more nuclear plants, I think that is the strategy from people who’ve thought very long about it from the environmental side.”

At the N.C. Sustainable Energy Association’s policy forum Monday, the talk focused on energy conservation and the advances in solar photovoltaic cells. According to Dale Carroll, deputy secretary of the N.C. Department of Commerce, the State of Mecklenburg is generating 45 percent of its electric energy from renewal sources, which Gov. Bev Perdue discovered on her recent trade mission. Carroll was talking about Mecklenburg, Germanynot the North Carolina county.

Meanwhile, North Carolina’s utilities are struggling to meet the goal of 12.5 percent of electricity from renewables that the General Assembly set for them in 2007.

“Dr. Blackburn has shown that going to 80 percent solar and wind power is technically possible,” said Ivan Urlaub, executive director of NCSEA. “However, our state policy does not drive us anywhere near those levels of use for renewables or for energy conservation.”

Urlaub said the association, whose members include environmental groups and companies in the solar, wind and energy-efficiency industries, doesn’t expect much to change during this year’s legislative short session. But during the 2011 long session, legislators will be asked to enact a major overhaul of energy regulation.

The idea, he said, will be to decouple the utilities’ sales and profits. That would require utilities to hit energy-efficiency targets while giving them incentivesmore profitsif they help customers save electricity.

“They’d trade incentives for less risk and less sales, potentially a lot less sales over time,” Urlaub told the Indy, “which is what we want to achieve. Because we don’t want to have to pay for new nuclear, natural gas or coal plants.”

Thirty-five states have commercial wind-power generation, Blackburn says. North Carolina is one of 15 that doesn’t. Wind is growing by a factor of 10 every decade as a power source. So is solar power, though because it still costs more, it’s eight to nine years behind wind.

Only in the Southeast is neither a major factor in electricity generation, Blackburn says. That’s because most of the southeastern states, unlike North Carolina, lack wind resources. And most, including North Carolina, have surplus power.

But as world oil supplies diminish and electricity supplants petroleum in transportation and heating, more electricity will be needed here to keep us warm and moving. The world is discovering wind and solar, he argues. It’s time for North Carolina to wake up, too.

“That’s why I wrote the paper,” he says. “The point is to say to the utilities, look guys, if you’re hung up on intermittency, it ain’t so.”