Page 45 - North American Clean Energy September/October 2019 Issue

Image shows missing piece of ice from turbine blade
A final icing event happens in locations near water (such as an ocean) and locations that are elevated. This event is called in-cloud icing. It’s the king of icing because you can literally experience the characteristics of precipitation based icing and freezing fog at the same time. Because of that, in-cloud icing events can be extreme, and result in the most significant production losses. Locations such as New Brunswick, Nova Scotia, and the northwest United States, are more prone to this type of icing event. Even more challenging is that some of your turbines at lower elevation may
not see any icing, while turbines at high elevations could be shut down.
Mitigating the Event
There are plenty of public and private commercial weather sources that predict icing. For the unique needs of a renewable energy professional, commercial sources may be the best option. One reason is
that they can spend more time focusing on forecasting the freezing fog and heavy wet snow events that can exceed the impact of freezing rain events. They can also supply raw forecast data feeds, which
allows the client to ingest the data in house for creating internal portal sites and dashboards that monitor production. Many commercial providers also have Meteorologists on staff that can support the client in collecting information and data that summarizes the severity of the event.
For these reasons, renewable energy professionals should rely on high resolution weather forecasts from commercial providers that focus on addressing the impact to your wind farm. By alerting you to ice accumulation days in advance, commercial providers enable you to adjust production forecasts, rearrange maintenance plans, and review safety protocols.
Don’t forget about the post icing event weather! Once the icing is over, when does everything return to normal? Temperatures below 32 with cloudy conditions will do little to remove ice from the blades. If the accumulation is substantial, you may not be able to run the turbine at all. Rising temperatures and sunshine are a good sign, but also precede melting ice – that means crews returning to work too soon could face danger from ice falling off the wind turbine. Likewise, starting the turbines too soon could send ice missiles flying hundreds of yards, presenting another serious safety hazard. Paying close attention to post icing event weather is equally important as preparing in advance of the icing event.
Preparing, Planning, Execution, and Recovery
You can’t stop the weather from happening, but you can prepare for it. Watch forecasts closely for all types of icing - not just the obvious events. Once you know an event is on the way, make sure you have a plan. Off- takers and power marketing teams should know how production could be impacted, and when. Look at the maintenance schedule for that
day - does it need adjusted? Once your plan is formulated, make sure to execute it. Continue to check forecasts regularly to see if the event
is getting worse or the threat is passing. As ice accumulates, monitor production closely, and stop turbines as needed. Once the icing event is over your work still isn’t done. You still need to execute your plan as you head into the recovery stage. Knowing when the ice will begin to melt is important. When is it safe to return to outdoor work? When will production recover to normal levels?
Ice events may be one of the most challenging natural hazards you will face. Unlike lightning stand downs, which usually last hours, or high winds, which rarely exceed a day, an icing event can last days, a week, or more. Impact to production, maintenance, and safety can be unmatched by any other hazard. Learning to recognize these events in advance by using all sources available can lead to better preparation and mitigation. Ultimately, you will lessen the financial impact while maintaining a high level of safety.
Marty McKewon is Chief Meteorologist at Indji Systems, a provider of weather monitoring and alerting solutions to the Renewable Energy Industry. Marty has 30 years of weather industry experience, including roles as a Meteorologist, Product Manager, and Sales Professional.
Indji Systems /// www.indji.com
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