PRINCETON – On February 21, when Princeton Light Department Manager Jonathan Fitch drove over Westminster Road to check on the windmills, he got an unpleasant surprise.
Instead of seven, he counted only six.
One of the 22-year old windmills at the PMLD’s wind farm had fallen over, landing on the storage garage, demolishing the building.
“I check on the site weekly, and had made a point to check the site on the previous Friday because of the high winds,” said Fitch. “All seven turbines and towers were up and okay then.”
After a long weekend of windy weather and the Monday holiday, Fitch decided to recheck the site. “I drove by Westminster Road and counted only six towers, so I walked up to the site to look and that’s when I discovered one of the towers had fallen over and landed on our storage garage,” he said.
The bottom section of the tower was a pile of twisted metal, mixed with large pieces of splintered wood that had been the garage. The broken turbine and smashed blades lay in a pile nearby. According to Fitch, the garage was used to store old parts and pieces for the old windmill and was going to be taken down as part of the wind farm upgrade.
Fitch called in his crew and got a backhoe to the site along with a 30-yard Dumpster to start getting the area cleaned. “I came back to the office and contacted the state Department of Conservation and Recreation to let them know,” he said.
The existing windmills haven’t been on line producing energy since October 2003, said Fitch.
“We knew we weren’t going to maintain them so we turned them off hoping to take them down when the project was approved to construct two new towers,” he added. The department received approval in 2003 to take down the windmills, but the work wasn’t done because the project has been delayed, he said.
Fitch called a structural engineer for a forensic analysis of why the tower failed and is awaiting his report.
“I also wanted an engineer to check the other towers to see if they were at risk for failure until they are taken down,” said Fitch. “It appears the back leg of the tower bent first, then the tower went down. It could have been over a period of time or gone down quickly,” he said.
The Board of Light Commissioners inspected the site on Tuesday and Wednesday and told Fitch to take down five of the remaining towers immediately, he said.
“We knew they were at the end of their use in 2001,” said Fitch. “We’ll leave one windmill up, that has the 50-kilowatt turbine, which Composite Engineering will use to test new blades for that size turbine. But the board doesn’t want to wait any longer before taking the other five down.”
Composite Engineering has put up $10,000 toward the removal of the other turbines. The five towers will come down piece by piece and Composite Engineering will refurbish them. One of the towers will go to the Henry Ford Museum in Michigan where it will become part of the museum’s collection.
The windmills were installed in 1984 and consisted of eight, 100-foot, steel lattice towers with 40kW wind turbines. At the time, residents voted in favor of purchasing the 16-acre site and developing the wind farm as an alternative to PMLD purchasing power from the Seabrook Nuclear Power Plant.
The original plan recommended approximately 500kW of capacity on 164-foot towers. PMLD didn’t install the recommended size and quantity of units due to the high cost, installing instead 320kW of capacity on smaller towers. At the time the windmills were projected to produce about 10 percent of the town’s energy requirements. The wind source at the lower height and the 50foot mature tree canopy surrounding the site were also factors in contributing to the lower than expected amounts of renewable energy. For a brief time the windmills produced about 3 percent of the town’s energy needs, but that fell to about 1 percent as the years went by.
In December 1999, PMLD started the process of researching options for the wind site, considered a number of options, and finally decided to upgrade the wind farm by installing two 230-foot towers with 1.6megawatt turbines.
In a February 2003 ballot vote, residents approved PMLD’s proposal to replace the eight windmills with the higher towers. The new windmills are expected to generate at least 40 percent of the town’s energy needs. The project has been the subject of extensive state and local permitting processes, and court challenges.
“We didn’t want to take the old windmills down until we were ready to work on the entire site because it’s much more efficient to do all the work at once,” Fitch said. “Keeping the old turbines establishes the fact we have an existing wind site and it was important to have them there as we went through the permitting process.”
Removing the old wind towers requires a crane and is dependent on the weather for good climbing conditions.
“We can’t do the work if there are winds,” said Fitch. “We’ll coordinate the work over the next few weeks – a combination of Composite Engineering manpower, my linemen and the crane operator.”
A crane will lower the turbines until they are about 25 feet from the ground where the PMLD crew using the bucket truck will remove the blades. Once the turbine and blades are on the ground, the lattice tower will be unbolted and lowered to the ground in one piece by the crane, said Fitch.
“We’ll do all five that way to maximize the use of the crane. That’s the most expensive piece of equipment at about $1,500 a day,” he said. Fitch expects it will take three or four days to get the towers on the ground. Then they will be disassembled and taken back to the PMLD where they will be taken away by Composite.
“It will be a little more costly to take the towers down now, separate from the project. But there isn’t any monetary loss to the Princeton ratepayer other than the salvage value of the turbine that was destroyed when the tower fell. We were going to give it to Composite anyway,” said Fitch.
“I suspect the tower fell as a result of the high winds, some with gusts over 50 miles per hour, and the age of the towers,” he said. “But I’ll know more after I get the report from the forensic engineer.”
In the past, two wind test towers have fallen at the site, one during an ice storm in 2002, and another in March 2003 as a result of a fault in the bedrock where the tower was anchored.
In 2004, a generator mounted on one of the eight windmills failed and the blades broke off.
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