Solar arrays being installed at Dubois Drive in South Burlington.

Harvesting Solar Energy on Dubois Drive

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Thursday June 09, 2011

This is the third in a series of articles about Renewable Energy in South Burlington.

As the morning sun amped temperatures into the eighties last week, Dave Blittendorf, president and CEO of AllEarth Renewables, stood in the shade of his orchard at the end of Dubois Drive in South Burlington. Around him, row after row of massive solar arrays, tilting their rectangular faces toward the sun, harvest northern New England’s largest crop of solar energy.

“This is a significant project,” says Blittendorf. “It’s big. It’s unique.” Big enough to power 450 homes from a 2.2 MW capacity after construction wraps up in July. And unique, in that it’s one of the only solar farms of its kind in the area: Blittendorf sees it as an example of solar’s potential to rival traditional sources of power generation while using technology that’s available to residents around Vermont.

“Every one of these is what we put in homeowners’ yards,” said Blittendorf, gesturing to a Solar Tracker, one of 382 such devices planted on steel posts around the 25-acre property. The tracker differs from a fixed solar panel array in that the 24 panels grouped into a rectangular frame perched atop the post move throughout the day, maintaining a constant 90-degree angle to the sun.

Tracking the sun, which Blittendorf compares to sunflowers whose heads also move throughout the day, grants a 40% increase in efficiency over fixed solar arrays. A GPS unit mounted on each tracker allows the panels to plot their exact relation to the sun: coordinates feed into an algorithm that determines where the sun should be, even if it’s too cloudy to see. This allows the trackers to harvest energy—at around 10% of their capacity—even when the sun is completely hidden.

Power gleaned from the trackers flows into underground lines, which in turn run under a wetland to join Green Mountain Power’s grid. Although currently under construction, the farm is able to put trackers online as they’re installed—workers mounted 26 trackers during a recent day’s work—and about a quarter of the trackers already produce electricity for GMP.

The project has been nearly a year on the drawing board. When the state passed legislation incentivizing commercial solar projects in 2009, Blittendorf and others around Vermont suddenly found they could build profitable solar farms. A 1MW fixed-array farm in Vergennes was the first to take advantage of the law. Blittendorf, who owns the South Burlington site with a partner under a company called Chittenden County Solar Partners, broke ground in December.

This $12 million dollar project, financed by the Merchants Bank, embodies Blittendorf’s visions for a clean energy future. “We have to switch off fossil fuels,” he said. “Nuclear’s a dead end. We saw that in Japan.” With a nine-month start-to-finish timeline, Blittendorf explains, this solar orchard stands tall against new nuclear power plants, which can take fifteen years to build. “If we harvest sun, wind, and water power, we can replace Vermont Yankee and eventually other fossil fuels.”

The long-term viability of solar farms remains a studied issue. On sunless, snow-covered, short days in the winter, the trackers sometimes harvest no power. Blittendorf says the individual panels, which cost $400 each, include a 25-year warranty. NASA’s had solar panels in use in space for many decades, he explains: if they can withstand space degradation for that long, he’s confident they’ll last half a century in Vermont.

An official kick-off is scheduled for July 27.

SOURCE: Eric Blokland, Correspondent