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Practical Business Reasons for Retrofitting Wind Turbines with Ultracapacitors

Practical Business Reasons for Retrofitting Wind Turbines with Ultracapacitors

| John Meaney, Regional Sales Manager, Southeast U.S., Mexico and South America

Wind turbines have come a long way since the original turbines were built in Persia in the ninth century. Today, giant manufacturers such as Goldwind, GE, Vestas, Gamesa and Siemens build turbines with blades up to 80 meters long and operate up to 8 megawatts of power. Size and power aren’t the only features that have evolved in turbine technology. Ultracapacitor-based pitch controlled systems are becoming the standard solution offered by turbine manufacturers based on factors I will discuss in this article. And there is a growing movement to retrofit existing older turbines away from their existing battery systems.

Ultracapacitors are installed in the turbine and manage the pitch for each blade individually. They are charged by the grid and are a critical safety part of any windmill. The pitch control system performs critical functions by "feathering” the blades to enhance the efficiency of wind energy conversion, as well as shutting down the system by pitching the blades to zero in the case of high winds or a grid failure.

There are two primary technologies that provide turbine pitch control: electric and hydraulic.

  • Electric pitch control systems use one of two technologies—battery or ultracapacitor. Electric systems dominate the technology with about 62% penetration, and ultracapacitors are the standard in about 66% of the electric solutions. It is noteworthy that ultracapacitors have only been in use since 1999 and have grown to the dominant position in the electric solution.
  • Hydraulic systems are installed in about 38% of the turbines and are mechanical devices that transfer fluid from stationary sources to rotating machinery. There are numerous moving parts that require maintenance and replacement over time. Hydraulic fluid can leak, ball bearings wear, and seals can leak. All of this requires regular maintenance and the system is overall more vulnerable to failure.

Ultracapacitors have taken the leading share position in such a short time for the following reasons:

  • They require minimal if any maintenance versus a hydraulic system
  • Depending on operation and use, ultracapacitors could achieve 15+ years without replacement versus more frequent required battery changes. Batteries generally have to be replaced every five to six years and in practicality, more frequently based on the environment and as the turbines age.
  • Ultracapacitors are resilient in extreme cold weather and can perform in temperatures down to –40°C

It is necessary to understand the return on investment (ROI) which takes into account the real costs associated with having to replace batteries. But as important as the ROI, there is a peace of mind that comes with the reliability of an ultracapacitor-based system.

Consider that the cost to replace batteries is extensive. Operators must shut the turbine down for at least four hours for maintenance, and the opportunity for energy capture is lost during this downtime. Also, factor in the cost of technician hours spent on maintenance (minimum of two technicians), and the safety risk of ascending the tower and replacing the very heavy replacement batteries—estimated costs are up to $5,000 for the technician’s time and grid downtime.

In summary, ultracapacitors can help achieve the longest life, require minimal to no maintenance, operate in a wider operating temperature range, and can provide higher reliability for an overall lower total life cost of all other technologies currently available. For these reasons, ultracapacitors make the most business sense when purchasing new wind turbines and upgrading existing wind turbines for better performance.

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Mike EverettJohn Meaney
Regional Sales Manager, Southeast U.S., Mexico and South America
About this author

John Meaney joined Maxwell Technologies as regional sales manager for the Southeast U.S., Mexico and South America in August 2010. Prior to joining Maxwell, he worked in the wireless and computer industries holding sales management and general management positions at D-link, Gateway, Toshiba, Panasonic and IBM. He holds a B.A. in economics from the University of Notre Dame and M.B.A.s in finance and marketing from Long Island University and Fairleigh Dickenson University, respectively.

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