In the world of technological innovation batteries have been a poor performer for many years, with their evolution and improvement lagging wildly behind the progress of the devices they power. The best commercially viable solution we currently have, in terms of energy density, are lithium. This battery technology is toxic and therefore horrible for the environment when batteries are disposed of, takes time to charge and suffers from long term degradation even when not used (yes that rumor about keeping lithium batteries partly discharged in your fridge to prolong their life is true!)
However things may be beginning to change with several new improvements appearing in recent weeks. One that really caught my attention was talk about the granting of Patent #7,466,536 to EEStor (http://www.pat2pdf.org/patents/pat7466536.pdf). There are two things that are really interesting about this. The first is that the patent describes a technology which, if it comes to fruition, will be massive in terms of battery powered everything, and particularly battery powered vehicles. The second is that EEStor, a Texas based company in the states, is venture capital funded by Kleiner Perkins Caulfield & Byers who are one of the more successful venture capital companies in Silicon Valley. They have financed little companies called Google, Amazon, AOL, Netscape etc. Venture capital is of course a high risk business, but these guys have a a good record of getting it right when it comes to new groundbreaking technologies and companies. If more evidence of their credibility is needed, Lockheed-Martin, the largest aerospace contractor in the USA, apparantely has an exclusive contract with them for military and aerospace applications.
So what’s an ultra capacitor, or even a capacitor. Capacitors store electrical charge measured in farads. In current day capacitor terms a farad is actually too large so typical capacitor values tend to be specified in microfarads (uF, millionths of a farad, ) and below. Capacitors also have a voltage rating, which is the maximum voltage the capacitors insulator (dielectric) can withstand before it starts to fail. They are used in pretty much every electronic device for many different functions and they typically comprise of two or more conductive plates with a very thin insulator (dielectric) in between. Pretty simple stuff and one of the fundamental electronic components. What makes ultra capacitors special is that they use new designs and materials to achieve massive energy storage increases. This is a field where that regularly touted term ‘nanotechnology’ is actively at work, creating new materials that remove the hurdles ultra capacitor designers need to get past.
The thing that would make capacitors really useful for mobile devices is that you can charge them extremely quickly, they can hold their charge for long periods of time and there is no chemical lifetime or degradation as they are used. The other thing that makes them especially useful for electric vehicles is that when accelerating you need to provide a motor with extremely large amounts of energy very quickly and capacitors are ideal for this. In simple terms, if they can be made to work they could be the perfect solution to mobile energy storage and could obsolete our nasty chemical batteries.
When you look at making capacitors ultra, for high energy storage applications, the thing you really need is to make the voltage you give them as high as possible. This is because the energy stored by a capacitor is the capacitance multiplied by the square of the voltage. This means that as you increase the voltage the energy stored goes up by the square of that voltage.
What EEStor claim to have created is a 31 farad (farad, not micro farad!) ultracapacitor that is significantly more dense than lithium-ion in terms of its energy density. It weighs a lot less but it stores the same amount of power. Their prototype apparently stores around the same 52 kilowatt hours of energy that the Tesla Roadster lithium based batteries store:
but you can charge it in a few seconds. To do this they use 3500V to get the massive squared energy storage benefits from the voltage.
One of the issues of this incredible recharging rate is that you need to have an extremely large power source available locally to be able to provide it. Well that problem could be simply solved by having a second ultra capacitor trickle charging from the local mains supply, at night when energy is cheapest, ready to deliver a full charge to a vehicle when it needs it.
This is just one company working on ultra capacitor technology and there are several other big players. There are also some experts who say ultracapacitors will never be realized or that the voltages involved will cause too many issues to be practical. However the fact that there is a company of this pedigree claiming to have already passed many of the technological challenges is very exciting news and this major step forward in mobile power is starting to get a lot more credibility as a viable solution in the near future.
And if you need a bit of proof about the capabilities of ultra capacitors take a look at this new super / ultra capacitor powered screwdriver by Coleman. It charges in 90 seconds and by all accounts actually works as advertised:
OK so the advert is ultra cheesy, but a cordless power tool with no nasty chemicals to dispose of, no limited lifetime and a massive leap in usefullness to the user compared to a typical electric screwdriver. Let’s hope the full potential of this technology can be realized.
