Page 24 - North American Clean Energy January/February 2019 Issue

wind power
Emergency Pitch Control
How ultracapacitors improve ef ciency and reduce O&M costs
by Joshua Hitt
Wind farm operators make every e ort to maximize turbine production, but they often face maintenance
issues that disrupt operations. Battery-based emergency pitch control systems can be a leading contributor to turbine downtime and maintenance cost.
A turbine’s pitch control system shifts the angle of the blades to protect the turbine from damage during a grid power loss event, or excessive wind speeds. Site managers often spend additional budget dollars performing unscheduled maintenance to address the issues associated with batteries, including degraded performance in cold and hot weather conditions, battery voltage faults, and additional turbine climbs to replace failed battery components.
Retro tting existing pitch systems with ultracapacitors, however, will translate into higher reliability, longer life, less maintenance, and overall improved turbine operation. Ultracapacitors, also called supercapacitors, are high-power energy storage devices
that store charge electrostatically (as opposed to the electrochemical process in lead-acid batteries). As a result, ultracapacitor technology provides higher reliability; systems do not require scheduled maintenance for 10 years or more, pitch battery maintenance is eliminated, and wind farm operating e ciency improves.
For remote turbines exposed to
extreme heat or cold environments, the electrostatic energy storage method of ultracapacitors make them an excellent choice. Cold temperatures slow the rate
of batteries’ chemical reactions, resulting in high internal resistance, and ine cient charge acceptance. Generally speaking, a battery that provides 100 percent capacity at 80°F (27°C), will typically deliver only 50 percent capacity at 0°F (–18°C).
Consider that each charge/discharge cycle also lowers battery capacity, due
to poor charge acceptance. As a result, continual operation at frigid temperatures can render the battery ine ective in executing an emergency pitch. Even with environmental conditioning (heaters
and fans), battery-based systems still experience extreme ambient temperature
Weather Monitoring
Weather Monitoring
Designed for Wind Farms
Designed for Wind Farms
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JANUARY•FEBRUARY2019 /// www.nacleanenergy.com