Thanks to a pair of new rooftop solar arrays, the Annandale School District will soon be seeing substantial savings on its energy bill.
Construction on one 96-panel array on the elementary building is complete, and workers expected have the second 96-panel array on the middle school mostly complete by the end of this week.
Actual operation will not begin until the power company hooks up to the solar arrays and the panels begin producing power for the school building on which they sit, which may not happen for several more weeks.
A third system will be installed on the high school next year after a section of roof is replaced.
Big savings expected
Rick Pullen, business manager for the district, explained that the new arrays are part of a program the district is participating in along with Innovative Power Systems of St. Paul. Under the arrangement, the solar panels come at no cost to the district, and the company benefits through a federal tax credit, incentives offered by the state to augment solar, depreciation and a 15-year power purchase agreement with the district.
"In the first 15 years they basically give us a 25 percent discount.
"We would have been paying that to Xcel anyway (for power), now we’re just buying it at a cheaper rate," said Pullen.
As a result of that cheaper rate, the individual system on each school is expected to save the district $1,250 in the first year. Since two systems are being installed, that total savings will be $2,500. In the initial 15-year period, the three arrays combined are projected to save the district nearly $65,000.
After the first 15 years, however, the district’s savings is expected to jump dramatically, because ownership of the solar systems will be turned over to the district, which will reap the full benefit of the power produced. Once the schools assume ownership of the arrays, the savings per school building is projected to be over $6,700 each year, or $20,100 total.
The systems have a warranty of 25 years, and are expected to have an operational life of closer to 30 or 40 years. At the 30-year mark, it is projected that the three systems will have saved the district over $275,000.
How it works
Each of the arrays is built on a metal frame that sits on a flat portion of the roof.
"They’re attached to a frame, but they’re not attached to the roof. That’s one thing we were concerned about, because we didn’t want to put a hole in the roof," said Pullen. "We don’t have to worry about leaks caused by this, and it’s all weighted down."
Each panel is about four feet long and two feet wide, and weighs about 80 pounds. Doug Hendricks and Michael Tambornino of Oxbow Sunworks, who were doing most of the installation work on the middle school last week, guessed that the entire array probably weighed between 8,000 and 10,000 pounds.
A structural engineer examined the school buildings before the installation to make sure the roofs were able to handle the added weight.
The panels were loaded onto the fixed frame facing south, and reflector panels will be added facing to the north this week.
Even while Hendricks and Tambornino hauled the panels to their places on a cold, cloudy Friday last week, blinking green lights on the panels indicated that the panels were detecting solar light and were capable of producing energy.
"They’ll still produce, but of course not as much as they would on a sunny day," said Hendricks.
The system will link in to the current conventional power source from Xcel Energy.
"They just tap into that and put a separate meter on there so we can measure how much electricity it generates," said Pullen. "Some of the teachers are interested because they’ve heard that other schools that do this have some type of reading or a panel that shows how much energy the array is giving and how much carbon it’s saving. So the teachers in the other districts have been able to tie that in to their curriculum. Some of our teachers are asking questions and they’re going to talk to the person in charge of this and see if we can do something similar."
According to Innovative Power Systems, each array has a rating of 39.36 kilowatts and is expected to produce a yearly average of 50,000 kilowatt-hours of electricity. Producing that much electricity from coal on an annual basis emits about 75,000 pounds of carbon dioxide.
"Preventing this much CO2 from being released to the atmosphere is equivalent to adding 5,015 trees to our forests," said the company in its proposal to the district. "Over a 30-year span, this system will offset 2,250,000 pounds, or 1,125 tons, of carbon dioxide."
District involvement
Pullen said the program has been offered for the past two years, but few districts participated at first because of uncertainty over what the program entailed. After the first year when participating districts reported no problems, many schools jumped at the chance to get involved.
"All we had to do was apply. It was a random drawing, but we luckily got all three of our buildings chosen," said Pullen, adding that about 50 percent of the applying schools were accepted.
With rapid developments in solar technology, Pullen said Annandale is getting a better deal than the schools that first joined the program.
"This is an improved system. The last couple of years they only had a five-year lease because the warranty was only a 10-year warranty. Now, with whatever new technology they have, it’s a 25-year warranty," he said.
One of the reasons for the longer warranty is a simplified array that has fewer opportunities to fail.
"It sounds like in the past there were more moving parts and these don’t really have moving parts, so that’s why there’s a longer warranty, because there’s really nothing that will break down," said Pullen.
During the warranty period the district will not be liable for any natural damage, but vandalism would not be covered.
With plenty of roof space still available, Pullen said it would be possible to expand the arrays if the opportunity ever arose to add panels at no charge, in which case the savings would increase. There are no plans to do so at present, however.