When torrential rains hit the Peace River country on the June 24-25 weekend, washing out access roads and creating instability in water-saturated hillsides, it gave Alterra Power crews a first-hand lesson in the power of nature they are harnessing at the company’s Dokie Ridge wind farm, the largest operation of its kind in B.C.
The rain didn’t affect the wind turbines directly, but it did cause a hillside to slough, carrying several aspen trees with it. They brushed against the power lines carrying the wind farm’s electrical energy to the BC Hydro grid. From remote monitoring equipment at stations in both nearby Chetwynd and Vancouver, Alterra staff saw 15 of 48 turbines suddenly go offline.
The access road, operated by West Fraser Mills, was made impassable by the rain. Creeks turned into torrents. The rushing water damaged bridges, overflowed culverts and took out whole sections of road.
A crew had to be sent out by helicopter to assess the damage at the wind farm, 60 kilometres west of Chetwynd.
Paul Rapp, Alterra’s vicepresident of wind energy, later described what had happened: “Following the rainstorm the area was so saturated that we had one section of slope fall down, taking some trees with it. It hit a couple of our transmission lines, which caused about 15 of our turbines to shut down.
“It didn’t actually damage the transmission lines but just the fact that the trees touched the lines tripped things off.”
Since it can be remotely controlled from Chetwynd, the wind farm can operate without people being on location. A contract maintenance team normally conducts weekly inspections, making sure moving parts are lubricated.
But the falling trees had slightly damaged two insulators as they fell. It took people at the site to repair it.
“We flew in a line crew who got things back online in about four days. During that period, it really wasn’t very windy, so we didn’t end up losing much in the way of potential generation,” Rapp said.
West Fraser pushed hard to complete the road repairs within 10 days, instead of the anticipated month. Besides access to the wind farm, West Fraser needed the logging road to recover logs already stacked roadside, inventory the company badly needed to keep sawmills operating.
Rapp said winds picked up after the lines were repaired, making up for the downtime. The Dokie wind farm, which went into full production in February, is expected to produce 340,000 megawatts of energy a year, enough to power about 34,000 homes.
He said the alternative energy company is trying to determine how often it can expect rain storms of the magnitude that hit over the last two weeks.
Alterra is considering developing an expansion to the Dokie farm on a nearby ridge and is conducting research to determine the average annual wind flow at the new site. From there, engineers can determine what type of turbine can be installed and what annual energy output to expect. Each turbine costs $1 million to $1.5 million.
Besides the Alterra development, one other wind farm is operating in the region and a third is under construction.
“The Peace region has a good wind resource. It has good average wind,” said Rapp. “That’s why it is the first area of the province to be developed.”
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