OXFORD — Farmers David and Cathy Knightly have placed the first tracking photovoltaic system in Maine on their 90-plus-acre Fairwinds Farm at 346 Skeetfield Road.

The system, called an AllSun Tracker, is a series of ground-mounted solar panels that track the sun and convert its light into electricity.

“It’s different from the stationary system, in that it follows the sun,” said Will Kessler of ReVision Energy in Portland, the project’s assistant designer.

The tracker uses a motor and a global positioning system to turn the solar panels from east to west and up and down to follow the sun’s elevation.

The solar power will replace the oil-powered hot-water heater and back up the wood stove heat in the house, Knightly said. He has a vegetable-oil-fueled Mercedes and is working on a 1974 Volkswagen Beetle that will run on electricity.

With the uncertainty of oil prices in the future and the desire to be green, the couple decided to invest in the unit.

“We’re trying to be environmentally responsible,” said Knightly, a Spanish teacher at Oxford Hills Comprehensive High School. He operates a strawberry picking business with his wife and children, Liz and Benji, during the summer.

Kessler said the system is made by a company in Vermont that partnered with ReVision Energy to bring it to homes in Maine and eastern New Hampshire.

It is 20 feet wide and 22 feet tall, and its 20 panels each have a 240-watt capacity. It provides 40 percent to 50 percent more power than a stationary panel mounted on a rooftop, Kessler said.

The Knightlys can expect 40 to 50 years of use from the system.

The units cost about $35,000 and with the state and federal assistance, the Knightlys say they expect to pay for it in 10 to 12 years.

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