08.30.11Brendan Andrews, Vice President - Sales, Ioxus, Inc.

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To get a glimpse of the future of energy generation, take a trip along the coast of China, or travel the country's interiors. Increasingly, the landscape is dotted with wind turbines, which capture and store energy straight from the elements. The rise of wind-generated energy in China and throughout the world comes as the industry solves one of the thorniest problems in environmentally based energy generation: storage. In order to create consistent, reliable stores of energy, wind turbines have relied on battery-driven systems, which have created other challenges. Today, the use of ultracapacitors is solving the problems that have plagued wind power and setting the stage for continued, rapid growth in the market.

The Wind Turbine and the Problem of Consistency

Wind turbines employ three rotor blades that feed into generators to create electricity. The pitch of these blades can be adjusted on the fly to respond to current conditions and to optimize power output. That variability creates opportunity for wind turbines to maximize the elements to create clean energy, but this changeability also creates waste, since the energy storage systems frequently used are sized to meet the highest possible power demands, even if those rates only occur briefly and sporadically.

When wind turbines employ batteries to store energy for emergency power supply, several issues emerge:

• Batteries struggle under moments of high peak power.

• Batteries perform poorly in low temperatures.

• The operating life of a battery is extremely limited in extreme conditions.
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• Frequent replacement of batteries creates potentially dangerous situations for engineers and maintenance crews.

• 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 -- now in use in 14,000 wind power installations and planned for inclusion in scores of new windmills -- alleviate the above concerns. These components are clearing the way for more widespread, cleaner energy production and storage. Consider the following:

• Ultracapacitors have higher functionality, with porous electrodes that enable significant charge accumulation and high energy release rates.

• Ultracapacitors have a longer lifespan, completing millions of charge and discharge cycles with limited degradation. While the replacement period for batteries is between two and four years, the expectation for ultra capacitor lifespan is more than 10 years. This contributes to a safety and maintenance issue, since wind turbine installations can be difficult to reach and service, especially under threatening weather conditions.

• Ultracapacitors have a far wider temperature tolerance, operating optimally at -40C to 65C.

• Ultracapacitors dwarf the cycling capability of batteries, delivering more than a million cycles to a battery's 10,000 to 50,000.

• The price of ultracapacitors has fallen 99 percent in the past decade, whereas batteries have dropped only 30 to 40 percent.

Wind Turbine Market Set To Grow

China's growing use of wind power signals a shift that will become evident across Asia and throughout the world. With some of the most difficult questions of energy storage and reliable power delivery solved by the advent of ultracapacitors, wind power is poised for significant global growth. While windmill installations worldwide were stagnant during the past two years, that is about to change. Estimates for new installed capacity between the periods of 2010 and 2015 suggest a rebound in growth with new cumulative installations of 236 GW. Assuming an average turbine size of 2 MW translates to 118,000 newly installed turbines through 2015.

The demand for ultracapacitors is growing in parallel with the call for more wind turbines. These components are enabling wind generation with the long-lasting, cost-effective and reliable energy storage solutions for which the market has been waiting.

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Reader's Comments

Date	Comment
Len Gould 9.7.11	Both in this article and on your website, you need to learn the difference between a Farad (F) and a microFarad (uF). A Farad is a HUGE unit of capacitance, and will most certainly not fit into any of the package sizes advertised on your website.
Len Gould 9.7.11	Things have no doubt changed some since my days in electronics, but I recall 100 microFarad 12VDC electrolytic capacitors being a chunky handfull and a chunky price. Farad-size 1000VDC grid power factor correction units were a heavy lift for a healthy tradseman. Definition: 1 Farad is that unit of capacitance which will flow (accept or release) 1 Coulomb of charge (1 amp for 1 second) per volt of potential difference across its terminals. To store the 8 hour output of a 2 MW wind turbine in capacitors rated 100 V would require 2000 x 3600 x 8 = 57,600,000 Farads of capacitance, plus a great deal of costly electronics designed to adjust the 100 to 0 volt DC output of the capacitors to the required constant DC input of the inverters, or substitue a 10x increase in capacitance to maintain the output voltage at +- 10% more cheaply.
Len Gould 9.7.11	math error. should read "To store the 8 hour output of a 2 MW wind turbine in capacitors rated 100 V would require 20,000 x 3600 x 8 = 576,000,000 Farads of capacitance,"
jiangtao he 9.7.11	Something misunderstood in the article? Actually, the ultracap you found in wind turbine is mainly for blade pitching, not for storage of energy generated by wind turbine. Hope this helps.
Jim Beyer 9.9.11	I'm holding a U-cap in my hand right now. It's about the size of a D-cell, and rated at 350 Farads at 2.5 volts. Ultra-caps work with a different technology than regular capacitors. Something about a different way of doing the dielectric, which allows the plates to be much closer together. They are much denser (energetically) than electrolytics.
Don Hirschberg 9.12.11	I would like to see the many orders of magnitude apparent discrepancy between Len’s hefty 100 MICRO Farad capacitor and Jim’s 350 farad capacitor about the size of a D-cell. (I’m so ignorant about capacitors that I still think of them as little thingees to put across switches on a bread board circuit or in an ignition system.)
Don Hirschberg 9.13.11	Doesn’t Len’s (corrected) arithmetic pretty much kill off the idea of large scale energy storage using capacitors? Or am I missing something? Something big.
Jim Beyer 9.13.11	Don, As Jiantao He indicated, this is just for the momentary burst of power needed to adjust blade pitch, not long-term storage in general. Ultra caps are based on a different technology. No one was talking about using capacitors (ultra or otherwise) for output power storage from wind farms. The use cited is a great application for u-caps as they are more reliable and last more cycles than batteries. A possible use for u-caps for energy storage would be electric vehicles. If you could carry enough to store the energy of an accleration/deceleration event (i.e., bringing the car from 0 to 40 mph and from 40 mph to 0) then you'd eliminate lots of wear/tear on the battery pack, which could allow for a smaller pack, deeper cycling, etc. U-caps also have better power sourcing and sinking than batteries, so you can accelerate easier and can receive more power from a strong breaking event.
Don Hirschberg 9.14.11	Jim Thanks for the explanation. But: You say, “No one was talking about using capacitors (ultra or otherwise) for output power storage from wind farms.” Well I am deceived. If we are only talking about the energy storage needed to, say, adjust propeller pitches then I am indeed deceived. Are not wind farms connected to some kind of grid? Do they need capacitors to keep the lights on?
Jim Beyer 9.14.11	Hi Don, I'm assuming the preferred design for a wind turbine is not to be dependent on a working grid to operate. Imagine the complexities of shutting a farm off from the grid and then restarting it. You'd need separate linkages (one for using and one for sourcing power), to say the least. Another minor point is that it looks like these are short high current events, which might be minor disruptions to the grid (needing more local reactance, perhaps) and possibly several events in sync if the wind shifts on a large farms with several hundred turbines. I can see how a better overall design would be to just have a small battery or u-cap to handle the load. I think some large generators/motors have their own local capacitance sometimes.
Don Hirschberg 9.15.11	OK Jim, thanks for the education but just how do capacitors do for wind farms what standby generators have been doing for hospitals for decades? To build your large wind farms in remote places would still require railroads and/or substantial roads nearby. Seems to me there would be a need for a large quantity of concrete for example. And if it is in a really remote location a village for people to live in during construction. Don’t these turbines turn into the wind as other windmills and sailing ships have always done without an outside source of energy?
Jim Beyer 9.15.11	Hi Don, I'm not sure I understand your question. I am (safely) assuming that the power need for blade pitch adjustment is a tiny burst; maybe a few kilowatts for a second or so. No more than that. I don't see how this relates to a standby generator. A totally different need. More like the large caps used in DC power supplies to even out the AC input. To your second question, yes they do.

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