The pitch of a wind turbine's three rotor blades can be adjusted to respond to current conditions and create electricity. Pitch adjustments allow wind turbines to maximize the amount of clean energy they can generate. In order to adjust the blades, turbines need power. To date, wind turbine manufacturers have relied on battery-driven energy storage systems for that power.

The wind turbine market, however, has been constrained by the challenge of creating consistent, reliable stores of energy from an unpredictable natural resource. The industry has hungered for an energy storage system that responds quickly, regardless of current meteorological conditions, to the needs of wind turbines.

In addition to the problems associated with battery-powered energy storage, which I outline below, often energy storage systems for wind turbines are sized to meet the highest possible power demands, even if those rates only occur briefly and sporadically.  This changeability also creates waste.

Drawbacks of Battery-powered Energy Storage

There are other problems raised by battery usage in these types of applications, including the following:

  1. Batteries struggle under moments of high peak power and perform poorly in low temperatures.
  2. In extreme conditions, the operating life of a battery is extremely limited, creating a situation in which engineers and maintenance crews must frequently swap out components under potentially dangerous conditions.
  3. Batteries do a poor job of delivering the frequent, short power boosts wind turbines need to make rapid rotor blade adjustments and create electricity.

Ultracapacitors, on the other hand, offer a highly reliable option that reduces overall system size. As the market continues to grow, ultracapacitors will become an increasingly important ingredient in wind-generated power production.

As more wind turbine applications employ efficient ultracapacitors, the wind power market is poised to reach its potential.

Five Facts Wind Turbine Manufacturers Should Know About Ultracaps

Ultracapacitors, like all capacitors, have a high power density.  What differentiates ultracapacitors from their traditional counterparts, electrolytic capacitors, is their high energy density, allowing them to store a vast amount of energy in a small package.  In general, the use of an ultracapacitor in combination with a battery is an excellent way to increase the overall power density of the power source and decrease the strain on the battery. 

The most important facts about ultracapacitors are these:

  1. Functionality: Ultracapacitors are similar to traditional film capacitors as their energy storage is based on surface area electrostatic charge accumulation at the positive and negative plates.  Highly porous electrodes in ultracapacitors enable significant charge accumulation in comparison to traditional capacitors.  The release of energy in capacitors and ultracapacitors is achieved at high rates due to this loose charge accumulation attraction.  The resistance to the energy release is primarily driven by the resistivity of the electrolyte system used.
  2. Lifespan: With no plating or chemical reactions occurring in ultracapacitors, there is no wear mechanism in the technology.  Therefore, ultracapacitors can complete millions of charge and discharge cycles with limited degradation.  Any performance fade in the devices are predictable and easily monitored so that any end of application life is easily predicted.  While the replacement period for batteries is between two and four years, the expectation for ultracapacitor lifespan is more than 10 years.
  3. Temperature range: Ultracapacitors operate optimally at a temperature range between -40 C and 65 C, whereas batteries function best on a modest spectrum of -20 to 40 C.
  4. Cycling capability: Here, too, ultracapacitors dwarf batteries. A battery can only offer 10,000 to 50,000 cycles to an ultracap’s million-plus.
  5. Price: Increasingly, ultracapacitors are also besting batteries in terms of price.  In the past decade, the price of ultracapacitors has fallen by 99 percent.  The cost of a 3000 Farad ultracapacitor 10 years ago was $5,000.  Today, the component sells for $50.  During the same period of time, battery price reduction measured only 30 to 40 percent.

Market Growth Calls for Ultracapacitor Adoption

Wind turbine installations worldwide remained relatively flat during the past few years, but estimates for new installed capacity through 2015 suggest a rebound in growth. The trend in these new wind turbines will favor ultracapacitors for several reasons. 

Within the turbine, pitch control of each of the blades ensures optimum positioning for efficient use of wind speed for both performance and safety.  Engineers accomplish the pitch control either mechanically or electrically, but electrical control systems replace mechanical movements with more reliable electrical systems.  However, when electrical control systems rely on battery-based backup systems, the potential maintenance advantage over hydraulic systems is not necessarily realized.  For this reason, designs for backup in the past few years have included ultracapacitors rather than batteries. 

Electrical pitch controlled systems have certainly won the favor of the market; current estimates show that 60 percent of newly installed turbine systems are electrical pitch controlled systems. This share should continue to expand as more new turbine developments focus on electrical-based systems enabled by ultracapacitors.

Ultracapacitors Offer a Bright Future for Wind Energy

One of the detractors for wind turbines has been the potentially costly and dangerous maintenance requirements. With longer lifecycles and greater temperature tolerance, ultracapacitors deliver safer operation. Ultimately, this will drive more widespread wind turbine adoption. Of course, this is a cost issue, as well, particularly for difficult-to-reach, offshore turbine installations. 

With more than 14,000 turbine installations, ultracapacitors have confirmed their many benefits over batteries, enabling electrical-based pitch control systems to fully capitalize on their inherent reliability advantages. As the use of modern wind turbines continues to expand, manufacturers will embrace ultracapacitors as the best option for simple, long-lasting, cost-effective and reliable energy storage.

Brendan Andrews is the vice president of sales and marketing at Ioxus, Inc.  He is responsible for the leadership and coordination of Ioxus’ sales and marketing functions and for educating the global market regarding existing and future ultracapacitor technologies.  Previously, Brendan served as Maxwell Technologies’ director of sales and marketing Americas.