Skeleton Technologies delivers ultracapacitor modules to provide backup power for wind turbine blade pitch control in wind turbines operated by a multi-billion global leader in the renewable energy industry. Replacing lead-acid batteries, the modules help to ensure that the turbine blades turn to a safe angle in storm winds or when the turbines are offline. The technology offers a longer lifetime and higher reliability compared to lead-acid batteries and significantly lowers the total cost of ownership.


The wind turbines of today are by far more complex machines than a simple turbine on top of a tower. They utilize precise control of each turbine blade to adjust the pitch of the blade, a technology which is called pitch control. Pitch control adjusts the blades’ angle by rotating them so that they use the right fraction of the available wind energy to get the most power output, all the while ensuring the turbine does not exceed its maximum rotational speed. This maintains the turbine’s safety in the event of high winds or loss of electrical load, during which the turbine shall stop rotating. The blades shall rotate towards a neutral angle against the airflow and the pitch control system enables it without connection to the main power.


Therefore, the pitch control system operates in a very demanding environment and plays a vital role, requiring power and reliability. For a long time, the industry has been relying on hydraulic or lead-acid battery systems for pitch control, but both require heavy maintenance, can be unreliable and unpredictable, which can lead to catastrophic failure of the wind turbine.


The maintenance of wind turbines is becoming a costly endeavor for many owner-operators, with a growing demand for a lead-acid battery replacement for wind turbines. Ultracapacitors have emerged to replace batteries as a backup power source for wind turbine pitch control.


Since ultracapacitors do not rely on electrochemical reactions, they can handle rapid, repeated charges and discharges at high power. They excel in applications with short-duration energy needs where battery maintenance and replacement are expensive, inconvenient, or both. In other words, ultracapacitors are a perfect fit for improving wind turbine efficiency.


Skeleton has recently signed a 43-million USD deal with a world leader in the production of energy from renewable sources, which sees our SkelMod modules replace lead-acid batteries, offering a longer lifetime and higher reliability, and lowering the total cost ownership significantly. The agreement will cover our customer’s needs until 2025.


The reliability and long lifetime of ultracapacitors are ideal for applications such as these, where maintenance costs are high and malfunctioning pitch control systems can lead to expensive disasters. The system is now close to having 100% reliability and is maintenance-free with over 1 million cycles. The modules do not need to be replaced before 10-15 years, while battery replacement-related costs were needed every 4 years for a lead-acid battery together with 2,640 EUR of yearly maintenance costs. The improved productivity is one of the key benefits for the wind park operators, who will make great use of increased uptime which directly contributes to revenue generation. Last but not the least, replacing lead-acid batteries with ultracapacitors allows limiting the use of lead and other dangerous materials.


The number of wind turbines is growing at a fast pace, and the traditional lead-acid and hydraulic pitch control solutions have not kept up with the development. We have seen a big spike in the interest for ultracapacitors recently on both the grid side and renewable energy production, and, in addition to this agreement with this market leader, Skeleton is working with several companies in the sector. This cooperation for increasing the uptime of wind parks is Skeleton’s yet another contribution to increasing the penetration of renewable energy in our fight against climate change.