Decommissioning Canada’s oldest wind farm

Michelle Froese, Senior Editor
Windpower Engineering & Development

This article is part of Windpower Engineering & Development’s February 2017 issue. A complete digital version of the issue is here.

 

During decommissioning, the TransAlta team used an assembly line process that worked from north to south on Cowley Ridge. Each blade from every turbine on site was taken down by crane, one at a time.

They say all good things come to pass and wind farms are no exception. For Alberta’s Cowley Ridge Wind Farm, Canada’s first and oldest commercial wind facility, the end of its operating life came earlier this year. At the time of decommissioning, the 57-turbine wind facility had a total generating capacity of about 17 MW.

“To give this some context, the 375-kW turbines were eventually de-rated to 300 kW. And in March of this year, one turbine at full production was making $4.71/hour,” said Wayne Oliver, Supervisor of Alberta Wind Operations at TransAlta, Canada’s largest publicly traded power generator and marketer of electricity and renewable energy.

Oliver was speaking at the Canadian Wind Energy Association’s (CanWEA) Annual Conference and Exhibition, held this November in Calgary, Alberta. “That’s not exactly economically viable,” he added.

Back in its prime, however, Cowley Ridge (located in Pincher Creek, about a two-hour drive from Calgary) was one of the most prominent wind-generating facilities in Canada, serving as an early example of what wind power could bring to the country.

“It was a unique experience working on the first wind farm in Canada,” said Chris Ford, about the wind farm’s decommissioning. He was one of the first wind technicians to work on the site and is now a lead operator at the TransAlta Wind Control Centre. “Back then it seemed like you were up so high, different from other types of work. On a great day there was nothing like it.”

The wind farm was completed in two phases over 20 years ago, and used Kenetech Model KVS 33M turbines (Kenetech was acquired in 1996 by a company called Zond, which was later acquired by GE Energy). Phase 1 was commissioned in 1993, and Phase 2 in the summer of 1994. The turbines were mounted on 24.5-m lattice towers, used variable pitch blades with 33-m diameter rotors, and operated in wind speeds up to 97 km per hour. In October 2000, five additional turbines were added to the site.

For safety, two cranes were used to lower tower sections to the ground. The decommissioning team typically disassembled two turbines a day.

“Decommissioning has been an interesting process,” Oliver said during his presentation. “I’m used to installing wind farms, not taking them down.” To date, he has been involved in the construction of eight wind farms and 364 turbines in Canada. “I literally started at the bottom. I was in the 34-foot foundation hole, lifting the base bolts up into the template that the tower section of a wind turbine would then be attached to.”

But this decommissioning project required a different skillset, and at a time when Canada is focused on growing it renewables’ base. The country currently has over 10,500 MW of installed wind-power capacity. “It’s not lost on me the irony that while the provincial and federal Canadian governments are investing in renewable energy, and while Alberta is committing to some 5,000 MW of renewables by 2030, here we are taking the country’s first wind farm down. I got a lot of calls in the spring asking why,” he admitted.

There were three main reasons, according to Oliver, but the first one was key: safety. Because of the open lattice tower and clamshell design of the nacelle, workers were fully exposed to the elements while climbing and working on aging turbines.

“These wind turbines offered a physically demanding platform to work on,” explained Oliver. “There were no engineered anchor points up in the nacelle or internal chain hoists, so the techs working up-tower were continually pulling tools and supplies, such as gear oil, up by hand.”

He said workers would place what they needed into a canvas bag tied to an 80-ft. rope, and pulley it up-tower. “They would work regardless of rain, wind, sleet, snow, and cold temperatures, so for safety issues, we decommissioned the farm.”

In addition, obsolescence and lack of profitability provided two more reasons. “We were seeing a lot of metal fatigue on the towers and had a tough time getting new parts. We had four turbines down for a couple of years because we couldn’t find antiquated blades anywhere that were a match,” he said.

Six towers down and more to go. This is a view from the north end of Cowley Ridge, looking south, after a few days of hard disassembly work.

Although Oliver and his team at TransAlta eventually found useful decommissioned blades in California, rotors were just one issue. “One can only replace a circuit board so many times, and we were working off old software and even older laptops. If either crashed, we’d be in serious trouble.”

The original manufacturer granted the turbines at Cowley Ridge a 20-year lifespan and they work to just shy of 23 years — which for Canada’s first wind farm probably isn’t bad. So with a growing list of required repairs and replacements, it only made sense to retire the wind facility. Once the decision was made, another one needed an answer: Who will do the work?

“I was tasked with the duty of figuring out whether we should self-perform the decommissioning or contract it out.” So Oliver got to work and did his research, at first taking bids and offers for the potential contract.

“It was interesting. In a downturned economy [Alberta has been going through a recession], everyone in the province that owned a cut-off saw wanted to help out and take down Cowley Ridge,” he smiled. Other bidders had more creative suggestions, such as simply bulldozing down the site. “And one guy wanted to use shape charges and blow the legs out from under each turbine one by one. Can you imagine the domino effect?” he asked. “Boom, boom, boom, one after the other! I mean it would have been entertaining but messy. Fiberglass and oil would be everywhere.”

Needless to say, TransAlta passed on that idea. The company eventually opted to self-perform, so Oliver helped assemble a multi-disciplinary team that included technicians, safety, and environmental consultants, financial planners, interconnection and transmission experts, landowners, the municipal district, a communication group, and others.

“We ended up self-performing with the wind technicians who worked on the site, and decided that the least amount of environmental damage would be done by disassembling the turbines one by one,” he said. In many ways, the project came full circle. “The process almost became the exact reverse of first building the wind farm. Even the crane operator from Mammoet, who helped take each blade down one by one, originally worked on the site and helped install those blades two decades earlier,” said Oliver.

Metal sheers from a track hoe cut up the steel tower sections for easier and more efficient hauling and transport off site.

During decommissioning, the team used an assembly line process that worked from north to south on the ridge. Once a nacelle was removed from a turbine, the tower legs were cut and safely tipped over with a crane. “But then we were left with about 22,000 pounds of steel, which is not exactly easy or cost-effective to throw up on top of a semi-truck trailer and drive away with,” Oliver said.

So a hydraulic sheer was brought in to cut up the steel from the towers. “This machine sliced through 2-cm thick steel as if it were paper. It also has an electric magnet on its shear, so would load up the cut steel bits onto trucks by magnetic force.”

Oliver said the team typically disassembled two turbines a day, but sometimes the work was cut short because of high winds in the region. Once all of the turbines were dismantled, the pad-mount transformers were next on the list. One was used for every three turbines. “The nameplate on the pad-mounts said they had no PCBs in them, but for due diligence I thought I better get them tested,” he said. And it was a good thing. Of the 20 transformers, two had low-levels PCBs.

PCBs (polychlorinated biphenyls) are a group of organic compounds used in the manufacture of lubricants and dielectric fluids used in transformers. Because of their environmental toxicity levels and possible risk to human health, PCB use and disposal come with strict restrictions in many countries. Environment Canada’s acceptable reportable amount of PCBs in oil is two parts per million.

“One of the pad-mounts had a level of 2.2, and another had 2.4 parts per million,” said Oliver. “We retested just to be sure because those numbers were so close to the limit, but the results were the same so we had to contract out special disposal of the oil.” This process involved a specialized company draining the oil, rinsing it with a solvent, and swap testing all of the windings in the transformers to ensure there were no remaining PCBs after the rinse. “After that, assuming the test is clear, you can dispose of the metal normally. If it’s not, you have to send it out for burn treatment and then the costs go up.”

Fortunately, TransAlta was in the clear after this process but Oliver provided the price comparison. “Draining oil from a non-PCB pad-mount transformer is about $C350. Dealing with one with PCBs is $C10,000. It isn’t cheap,” he said.

Once removed from the towers, each nacelle had its lid detached and oil carefully drained before being loaded up on a flatbed truck for transport and recycling offsite. Two functioning nacelles were donated to colleges for wind-tech training programs.

Disposal of the transformers meant phase one of Cowley Ridge Wind Farm’s decommissioning was officially complete but, much like its installation, the wind farm’s dismantling is a two-phase process. “The first phase involved getting rid of everything above ground, and the next phase will cover everything below ground. We’ll start pulling up all the concrete in 2019,” said Oliver.

Why the delay? “We — meaning TransAlta, the landowners, wind technicians that have worked onsite, and so on — really want to repower the ridge once it becomes economically feasible to do so,” he said. “And with Alberta’s new commitment to renewables, we will certainly be involved in the bidding process.”

Oliver said it makes the most sense to wait until a repowering project gets a green light before digging up the ridge. “With all of that grassland and the challenge of the rocky ridge, you’d want to wait before tearing up the land, jackhammering concrete, and pulling up the trench, to work on the reclamation and repowering at the same time if — and fingers crossed — that is to happen in the future.”

Until then, while there is disappointment Cowley Ridge Wind Farm has past its viable operating life, good has come of the project’s decommissioning.

“We donated two functioning nacelles with the control systems, so one could apply blades and work the pitch, to colleges,” said Oliver. One went to Northern Lights College in Dawson Creek, British Columbia and the other to Lethbridge College in Alberta. The fully operational nacelles mean college students can simulate and learn from turbine conditions similar to what they’ll find in the field.

TransAlta also recycled 90% of the Cowley Ridge turbines. “We recycled 48,000 kilograms of steel root ends from the blades, 567,000 kilograms of nacelle metal, 560,000 kilograms from the towers, 17,100 kilograms of copper wiring, and 60,000 kilograms of metal in the pad-mount transformers,” said Oliver. “Overall, the total of metal recycled was over 1,252,000 kilograms.” The company also recycled 44,600 liters of oil.

When you consider that the lattice towers do not have as much metal as today’s modern, tubular towers, those numbers are impressive. “We actually recovered 50% of the decommissioning costs through metal sales,” said Oliver. “And for now, that’s the story of Cowley Ridge. Not a bad life but one we hope to repower again.” 

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