Hurricane Irene and its impact on wind farms
[This article by Simon Mahan was cross-posted from Footprints on the Path to Clean Energy, the blog of the Southern Alliance for Clean Energy.]
This is the final blog in a three part series examining how natural disasters like hurricanes impact our energy generation.
In the past decade, wind turbines have sprouted up along the East Coast in Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, New Jersey, New York and Delaware. As more wind farms are built in coastal areas and even offshore, a common question has been: How will turbines withstand hurricanes? Through the anecdotal stories below, we can conclude that wind turbines along the East Coast performed exceptionally well before, during and after Irene.
A handful of turbines and wind farms were exposed to the winds from Irene from Delaware to Maine and based on the information gathered here, all of them survived and are operating. Irene made landfall in North Carolina at 8 AM on August 27th, with wind gusts of 86 miles per hour – a Category 1 Hurricane. By 8AM on August 28th, Irene was bearing down on northern New Jersey as a Tropical Storm with wind gusts of 63 miles per hour. Irene had dissipated to Extratropical Cyclone status by 8 PM on August 29th when the storm was directly over Vermont and New Hampshire and had wind gusts of 52 miles per hour. By no means was Irene the strongest storm to have hit the East Coast in recent years, but the storm provides some valuable insight on how our country’s energy resources respond to extreme weather threats.To gather insight for this blog, I contacted eight turbine operators representing 76 individual turbines with a total capacity of 174 MW. Wind turbine owners and operators were very forthcoming in sharing information about how their projects fared during Irene and responses poured in between August 29 – September 2. Seven operators responded representing 74 individual wind turbines with a total capacity of 172 MW. Listed below is information about some of the turbines impacted by Irene.
Delaware (Lewes) – University of Delaware – 2 MW, Gamesa
The University of Delaware installed a new 2-MW Gamesa wind turbine in 2010 – Delaware’s first utility-scale wind turbine. The College of Earth, Ocean, and Environment operates the turbine at the Lewes campus. Hurricane Irene struck this turbine as a Category 1 storm. According to Dr. Jeremy Firestone, “We shut the wind turbine down on Friday in advance of the storm and hooked it up to a diesel generator. Strongest wind I recorded from viewing the SCADA output during the storm was 72 mph, although there might have been strong gusts (it would require detailed looked at the data). It is now performing fine.”
Dr. Willett Kempton went on further to say, “One clarification, the generator was to keep the turbine blades and nacelle aligned for minimum wind cross-section if/when the local power grid went down. This might have made a difference if the winds had gone much higher, like over 130 MPH.”
The turbine was using active yaw controls to maintain its direction into the wind during Hurricane Irene. However, if the local power grid shuts down, the turbine stops generating power and stops receiving power – halting active yaw control. Attaching a back-up generator helped maintain power to the yaw system. Dr. Kempton explained, “It wasn’t necessary as it turned out, but better safe than sorry — if we’d known it was going to only be Cat 1, it would have been more fun to be generating electricity.”
The University of Delaware has a webcam focused on the wind turbine with output data that can be read over the internet. You can access the webcam by visiting the website here: http://www.ceoe.udel.edu/lewesturbine/multimedia.shtml.
New Jersey (Atlantic City) – ACUA Jersey Atlantic wind farm – 5 turbines, 7.5 MW, GE
In 2005, the Atlantic County Utilities Authority had five 1.5-MW General Electric turbines installed to help power a wastewater treatment facility. Prior to Irene, an article was published by the Press of Atlantic City that interviewed David Smith, Vice President of Commercial Operations at Infigen Energy – one of the co-owners of the project. Smith was quoted as saying, “Wind turbine blades… are designed to withstand the forecasted winds of Hurricane Irene, so we will not be removing and storing any blades.” Irene struck this wind farm as a Tropical Storm with wind gusts around 63 miles per hour. According to Rick Dovey at ACUA, “The short answer is yes, they survived, and survived with no problems.”
Tom Laulettea, also of ACUA, went further: “The wind turbines were shut down on Friday August 26th at approximately 5:00 PM when Atlantic County Emergency Management decided to shut down access to Atlantic City at 6 PM.”
New Jersey was looking at Irene as one of the biggest storms to have hit the state in the past 60 years. Perhaps the most ominous sign was when New Jersey Governor, Chris Christie (R) told everyone to “Get the hell off the beach.” a frightening stance to take considering the state’s dependence on its beaches for tourism revenues. The ACUA turbines survived the storm – and now they can go back to the primary purpose of generating electricity and a secondary purpose: tourism. The turbines have become tourist attractions, with ACUA offering free tours. An estimated 15,000 people visit the turbines annually. ACUA also has a webcam focused on a couple of the turbines, which is viewable here: http://www.acua.com/acua/content.aspx?id=492&ekmensel=c580fa7b_20_88_btnlink.
Rhode Island (Portsmouth) – Portsmouth Abbey School – 660 kW, Vestas
The Portsmouth Abbey School had a 660 kW Vestas wind turbine installed in 2006. By the time Irene’s eye was approximately 100 miles away from the school, the storm was still a Tropical Storm with wind gusts of 58 miles per hour.
Most wind turbines are designed to register if the local electrical grid has been compromised. For the safety of linemen repairing downed power lines, wind turbines automatically shut off so as to not electrify downed lines. According to Brother Joseph at the Abbey School, “Because the turbine shut down with the power outage early in the storm, we don’t have a lot of data. The highest wind the turbine saw before 9:30 was approximately 66 mph. The sustained winds seemed to be in the 35-40 mph range with gusts at that point.”
Brother Joseph also stated, “Our turbine worked just as expected during Irene. It generated until just after landfall at which point the grid went down and the turbine automatically locked itself down. It remained in this state throughout the rest of the storm. The turbine went back on line 24 hours later when utility power was restored.”
Irene was not the first major storm to have affected the turbine. According to the Abbey School’s website, “During its first year of operation, the highest documented wind gust was 67 mph. The turbine generates wind up to 55 mph, then pitches the blades to 90-degree angles and waits for the wind to subside to 45 mph before starting to turn again.”
To learn more about the Portsmouth Abbey School and their amazing green energy initiative, please visit their website.
Massachusetts – Hull 1 & 2 Wind Turbines – 660 kW and 1.8 MW, Vestas
The town of Hull has a long history with promoting wind energy. Situated on the coast, Hull residents are well aware of the strong winds available to them almost year-round. In 2001, Hull installed its first utility-scale wind turbine – a 660-kW Vestas machine. In 2006, the city built a second turbine – a much larger 1.8-MW Vestas turbine. An article ran in the Patriot-Ledger prior to Irene concerning the two turbines. In the article, Patrick Cannon, chairman of Hull’s Municipal Light Plant, stated he did not anticipate a problem for the turbines and that in wind speeds of excess of 52 miles per hour, “The blades will stick straight into the wind and turn flat.”
Vermont (Searsburg) – Green Mountain Power – 11 turbines, 6 MW, Zond
The Green Mountain Power Wind Farm in Searsburg, Vermont was built in 1997 with eleven 550-kW Zond turbines for a total capacity of around 6 MW. By the time Irene reached the wind farm, the storm had been downgraded to an Extratopical Cyclone with wind gusts around 52 miles per hour. Vermont has had excessive flooding due to Irene and power outages are still intermittent. Between the power outages and serving customers, Dorothy Schnure from Green Mountain Power was able to respond, “They certainly survived.”…”The turbines generated during Hurricane Irene, although for a few hours when the wind speed exceeded the limits, the turbines shut themselves down as designed. They started up again when wind speeds were within generating range. They did just fine.”
New Hampshire – Lempster Mountain Wind Farm – 12 turbines, 24 MW, Gamesa
Iberdrola Renewables, a company based in Spain with a subsidiary in the United States, built the Lempster Mountain Wind Farm in 2008. This wind farm contains 12 wind turbines with a total capacity of 24 MW utilizing Gamesa wind turbines. The Lempster Mountain Wind Farm is only about 50 miles northeast of the Green Mountain Power Wind Farm in Searsburg, Vermont and therefore likely experienced similar wind speeds from Extratopical Cyclone Irene. According to Paul Copleman from Iberdrola Renewables, “The Lempster turbines did pretty much what they were supposed to do. The turbines detected high wind speeds and paused themselves. When we were ready to go again, the turbines started without any issues.”
Maine/Vermont – First Wind
First Wind has two operating wind farms in northeastern Maine, with an additional farm under construction in Maine and Vermont each. The Sheffield Wind Farm in Vermont that’s under construction was in the direct path of Irene. First Wind’s wind farms in Maine were not close enough to be impacted directly by Irene. According to John Lamontagne of First Wind, “We were not significantly impacted by the hurricane, thankfully. Our projects in Maine operated well and weren’t impacted at all. In some cases, when the winds are too strong, we shut the turbines down. But the turbines were back up and running shortly thereafter. In New York, the same applies. In Vermont, we have a project in construction. As you may know, there were heavy rains in the state. However, due to the extensive drainage system installed there, there was very little impact despite some 6 inches of rain at the site. The project resumed construction on Monday and is slated to be completed in October or November.”
Maine – TransCanada, Kibby Mountain – 44 turbines, 132 MW, Vestas
The Kibby Mountain wind farm is the largest wind farm in New England. By the time Irene had reached the Kibby Mountain wind farm, the storm dissipated and wind speeds were less than 52 miles per hour – the farm survived the storm without a problem. According to Leanne LeBlanc of TransCanada, “The Kibby Wind Power turbines were secured prior to receiving the brunt of the storm. This was done under a “minimum generation” order from ISO New England. The restriction was lifted after the storm passed and all of the turbines returned to service without incident. All turbine and system equipment survived the storm with out any problems. The facility did experience utility power loss and communication failures but these were attributed to issues within the regional system.” As with several other wind farms along the East Coast, factors outside of the Kibby Mountain wind farm’s control (the grid operators decision, or loss of grid power) caused the turbines to preemptively shut down.
In summary: wind turbines can survive hurricanes. It’s up to existing projects, project developers, turbine manufacturers and the industry as a whole, to update the public on how turbines handle extreme weather events.
Interested in how our more traditional sources of energy weathered Irene and just how wind turbines are designed to weather big storms? Be sure to read our recent blogs on Hurricane Irene’s Impact on Fossil Fuels and Nuclear Power and How Wind Farms Weather Hurricanes.
A special thanks to all the people who responded with information about how wind turbines survived Irene. Specifically, Dr. Jeremy Firestone and Dr. Willett Kempton (University of Delaware), Rick Dovey and Tom Lauletta (ACUA), Brother Joseph (Portsmouth Abbey School), Dorothy Schnure (Green Mountain Power), Paul Copleman (Iberdrola), Leanne LeBlanc (TransCanada) and John Lamontagne (First Wind), made this post possible.