Ultracapacitor Energy Storage on the Grid

Amazing how slowly the technology development work on the grid is moving, isn’t it? In California, we are faced with a 33% Renewable Portfolio Standard (RPS) requirement by 2020. The industry still has not adopted a solid answer to the imposition these renewable resources, such as solar and wind, will place on the stability of the supply to the grid and the reaction of the grid to it, even though one does currently exist. It is well known that intermittency from renewables, caused by everyday occurrences such as constantly fluctuating wind velocity and clouds passing over solar arrays, will pose serious challenges in grid operation and will drive the demand for stabilizing influences.

Ultracapacitors, or supercapacitors as they’re sometimes called, provide one stabilizing influence. Solar “firming” (using stored energy to smooth solar system output) is a prime application ready for ultracapacitor energy storage stabilization. The high variability and unpredictable nature of the solar outputs make a solar farm a perfect environment for ultracapacitor energy storage. “Solar is growing so fast it is going to overtake everything,” said Federal Energy Regulatory Commission (FERC) Chairman Jon Wellinghoff in a recent interview.

While it may not take over everything, considering the source of this quote, it is likely rooted in reality and speaking to the continued growth and proliferation of solar technology. With solar comes the need for solar firming. The value proposition — including power performance, reliability, lifetime, and operating temperature range — of ultracapacitors make for a system which is perfectly suited for the demanding grid environment.

It is unfortunate that appropriate decision making is often slowed by special interests, lack of information, politics, and more. If the true story was told, and clear minds were evaluating that story, ultracapacitors would be firming renewables’ output into the grid in a big way today. The answer to the question is already here, but the people asking the questions are distracted, which slows down progress. There are a few progressive individuals out there who get it. Those champions are ahead of the rest in addressing the relatively manageable problem of instability and renewables.

What will it take to overcome grid operational challenges?

14 comments on “Ultracapacitor Energy Storage on the Grid

  1. RedDerek
    March 19, 2014

    There are other storage devices out there as well. Batteries, but there is an environmental cost and life expectancy. I also remember reading about the high-speed inertial devices as well; these pose their own set of risks.

  2. Davidled
    March 19, 2014

    I think that ultracapacitor stores the energy in an electric field, while battery stores the energy chemically. Therefore, when charging and discharging it, there is no limitation for total cycles. Ultracapacitor would be last long.  Ultracapacitor would provide better performance than battery in some application.

  3. Netcrawl
    March 19, 2014

    @Daej, Its a promising piece of technology, it not just charge faster than battery it also last longer, they last longer because they don't suffer the physical tool in charging and discharging that wear down the batteries, batteries wear out because their chemicals lose potency over time. 


  4. Netcrawl
    March 20, 2014

    @Daej supercapacitors have key advantages, they can provide high power and be used in millions of cycles, they don't overheat. And then there's another one, their performance is more predictable and their materials are more reliable and less vulnerable to temperature changes. 


  5. eafpres
    March 20, 2014

    Hi Mike–thanks for the article; it prompted me to go look at your products.  I took a look at the specs of your 75V Wind Engery storage model.  If I'm reading this correctly, it stores 73W*h of energy.  At 75V, I would need 6 car batteries in series.  But if I did that, a rough estimate is 5400W*h, or nearly 75 times the stored energy.  I realized that the other variables of a super cap like rapid charge/discharge, etc. are more suited to the application, but it seems like the specific energy is pretty low.

  6. MAEverett
    March 24, 2014

    Hello Blaine,

    Thank you very much for your comment.  The specific energy of ultracapacitors is quite low compared to battery energy storage devices. Compared to electrolytic capacitors however, their energy is quite high.  So it depends on your frame of reference whether they have low or high energy. But you did specifically mention batteries so I knew what you meant and you are correct. The true value of the ultracapacitors comes at the hand of their extraordinary power capability (more thn 12kW/kg power density) their extremely long cycle life, of many 100,000's cycles up to 1M or more depending on the use model and the application, and their low temperature performance, nearly room temperature like at -40C. These are all areas where batteries of any kind suffer while ultracapacitors excel. Therfore we spend a lot of time at Maxwell Technologies Inc talking about and showing the benefits of the two technologies together, with ultracapacitors carrying the power demand and the batteries carrying the energy demand, application components of which show up in most all energy/power  delivery applications. And ultracapacitors work equally well with any type of battery, not just LIB's but PbAcid and other types.  When using ultracapacitors for their inherent strengths there is nothing better. So when in the market for high power from seconds to a small number of minutes, think of ultracapacitors. When needing sustained energy on the order of minutes to hours, think of batteries. And for applications which have high power demand and sustained energy requirements, think of them both.

    Thanks again for the comments.


  7. eafpres
    March 24, 2014

    Hi Mike–thanks for your feedback.  I had an Aha! while reading your comments.  I have seen some hybrid battery/ultra-capacitor offerings on the market.  The way you put it in context it makes sense to me now.

    Here's an interesting hybrid application (warning–this is the antithesis of green).  I used to have a turbo-charged sports car.  I did a lot of upgrades myself, it was great fun.  A nice combination of thinking through the engineering with a fun kick in the pants after implementing.  For very short durations, a relatively large bank of ultra-capacitors, having the nice power to weight ratio you mentioned, could be used to power an electric motor-driven compressor and increase the boost.  Similar to hitting that NOS button, the numbers seem favorable to do this, but it would require a fair amount of work to implement.

  8. MAEverett
    March 25, 2014

    Hi Blaine,

    You will probably be interested to know that what you are describing is currently a very active area for exploration by virtually all automotive OEM's today, around the globe. E-turbo is an enabling technology to allow reduction in ICE size and still retain power performance in todays green vehicles that are being regulated to emit fewer carbon emissions and still meet the demands of consumers. No one likes to give up anything so acceleration and overall performance is always going to drive automotive technology while the regulations drive more economy of fuel and stricter emissions standards. So you are actually spot on with this application and it is considered green in the senese that it is coupled to higher vehicle fuel efficiency. Very perceptive on your part. Ultracapacitors and batteries are in hot competition for this space but if I had to lay money on it, ultracapacitors will win out given that this application is tailor made for their strenghts, short term, high power as you pointed out.

    Keep thinking, and you will come up with dozens if not hundreds of more applications for ultracapcitors. Our lives are driven by the consumption of energy both high rate and low rate, and for that reason, ultracapacitors as well as batteries figure prominantly in the future.


  9. Sachin
    March 30, 2014

    Batteries would have been ideal as storage devices for any renewable energy source except for the problems of limited life expectancy given the fact that they store energy chemically. Ultra capacitors, on the other hand, do not store any energy chemically and with the repetitive charge-discharge process they can accommodate a practically unlimited number of cycles thereby eliminating the life expectancy problem so, in my opinion, they are definitely the way forward.

  10. geek
    March 30, 2014

    “Ultra capacitors, on the other hand, do not store any energy chemically and with the repetitive charge-discharge process they can accommodate a practically unlimited number of cycles thereby eliminating the life expectancy problem so, in my opinion, they are definitely the way forward.”

    @SachinEE: I think because of the fact that the Ultracapacitors do not store energy chemically, the charging process is likely to be higher as well. This itself will have a lot of benefits to offer as one of the major problem with chemical batteries is their slow charging time.

  11. geek
    March 30, 2014

    “And for applications which have high power demand and sustained energy requirements, think of them both.”

    @MAEverett: I'm not sure if it's entirely relevant, but the closest analogy to compare batteries and ultracapacitors that I can come up with is the difference between RAM and Harddrive in a computer. The former is faster but has limited storage capacity and is volatile, the latter is slower but with higher capacity and more permanent. What do you think?

  12. geek
    March 30, 2014

    Interesting post, Mike. What do you have to say about the cost factor of ultracapacitors in terms of ther initial cost and operational costs (if any)? I believe cost should be a major factor which will determine how well any technology is likely to thrive in the market.

  13. chirshadblog
    March 30, 2014

    @tzubair: Yes cost is a major factor but we should not focus only on cost. If the returns are high then the cost factor can be overlooked but it all depends on what sort of a decision the management is willing to take here.  

  14. Sachin
    March 31, 2014

    @Mike, this piece presents some interesting ideas and though none of it is new, the manner in which you put it across is very insightful. I particularly love the last part; we already have the answers to these problems but politics, administrative bottlenecks and self interests still stand in the way of achieving stability in renewable.

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