Super Capacitors

True, if the medium separating the plates has dielectric constant ε=1.
When the dielectric constant is larger than 1, the field E confined between the plates (and thus the potential difference, V) is reduced by a factor 1/ε, and thus the capacitance C=Q/V is increased by a factor of ε. This is one secret of how to beef up a capacitor: Increase the dielectric constant of the insulating material. Hence the barium titanate experiments that were being done a few years ago; I don't know if that avenue of research went anywhere useful in the end.

The other trick to beefing up a capacitor is to decrease the spacing between the plates while increasing their effective area. This is where modern nanotechnology comes in- processes and techniques we simply didn't have until the last few years.

I suspect that what EEStor has done is a combination of the above techniques. But they let so little information out that I don't know for sure how their ultracapacitor is built.

True. A capacitor's voltage-time discharge curve cannot be constant, very much unlike that of a battery. Making effective use of ultracapacitors for storing significant amounts of energy would require significant advances in DC voltage regulation.

 

Lets wait and see what they come out with. I'm curious as to how much power they are going to supply and over what time. At 9$ one could maybe buy a few and cruise all day long

 

Matt, do you think it is possible that eestor actually have made a significant breakthrough? Maybe the secrecy is part of their reaction to having done something so significant(or insignificant for that matter)?
I imagine there would be a herd of thieves after them IF they had succeeded....

 

I think they're just being really, really careful to make sure their device is performing the way they want it to, and that their patents are in line, before they let anything slip. Many a tech firm has been killed when information became public too early, the media pounced, and a frenzy of stock activity, over-inflated 3rd-party predictions, and general chaos drove the stock sky high and then straight into the ground.

The engineering challenges that would have to be overcome to get a viable ultracapacitor are now fairly well-defined, and I would expect anyone trying to work through them would be very careful about what information got out- due not only to potential competitors, but also because of the risk of the firm being bought up and hidden away by larger companies who would have something to lose if it were to work. One need only look at how closely Chevron (through Cobasys) guards the patent on the NiMH battery technology to see why EEStor would be a bit paranoid.

 

A datasheet of an existing Ultracapacitor can be found on the Maxwell website, http://www.maxwell.com/ultracapacitors/products/modules bpak0020-15v.asp

This is a real, existing product, more or less comparable with a LA battery: it has 6 cells and up to 15 VDC working voltage. With this advanced technology, Maxwell states the power to weight ratio as 3.25 Watt-hours /kg. A small car battery rated at 50 AH packs 600 watt-hours, so to reach the same storage capacity with these Ultracaps, approx. 20 kg. of these will be required.
The car battery is still the winner, with approx. 12 kg, but the gap is less than I would have guessed.

Maxwell is not very confident that the Ultracap will perform as well as the data-sheet promises: no warranties of any kind, not suitable for life support devices or critcal systems etc. But the target is set at 500.000 cycles, exceeding that of the best rechargeable batteries with at least 2 decimals. And the cycle test is done at only half the working voltage and with constant charge/discharge current.
Moreover, for the type BPAK0052 P015 B02, clearly a commercial product, a leakage current of 50 mA is considered acceptable. Translated into plain English this means that the capacitor must be under continuous charge, otherwise it will be empty when needed.

Summary: an interesting development, but far from perfect. And a very negative aspect of this technology is that this product is of the electrolytic type, so there is a liquid inside that may leak out or evaporate if the seal is less than perfect, if the temperature limits are exceeded or a cell is charged above 2.5 volts.

If the secret EEstor capacitor is twice as good as this one, it is still a lousy power source for a vehicle; it must be 10 times as good and even
then there is the problem of the unstable output voltage requiring lots of electronics before it can be used to power an electric motor.

 

hmmm.... Just did some research using the links posted earlier in this thread. Here's some info (claims) from a patent EESTOR recently aquired. You can read the ultracapacitors.org writeup on it here: http://www.ultracapacitors.org/ultracapacitors.org-blog/eestor-issued-new-patent-on-the-eesu.html

Unfortunately, nobody knows of any working prototype of this technology
Anywise, I'll attach a chart that they included in their patent documentation, I LOVE how american inventors have taken to making statements of "facts" related to their patents' capabilities when no working protos exist...rofl!

 

Thanks for all the input! Very exciting to contemplate that MAYBE somebody has a real breakthru. Makes me want to take another look at doing a small electric cat or tri. What if it is really true? Imagine the possibilities...

 

Here's the link to the entire patent, if anyone's interested:
http://www.pat2pdf.org/patents/pat7466536.pdf
It was just issued on Dec. 19.

That clarifies a few things. Firstly, the claim of 52.22 kWh energy storage: This appears to be a calculated value, given that the capacitance of the device is claimed as 30.693 F (sounds like the right ballpark for an ultracapacitor this size, if rather more precise than manufacturing tolerances would allow) and its maximum operating voltage is 3500 V (again, reasonable in theory, but that introduces some practical problems.)

The patent also clarifies how the device is built and how it works. Unfortunately, it is written in engineers' legalese; if you're familiar with the language, though, the patent answers a lot of questions. To summarize, it is a lightweight, high-voltage, high-permittivity parallel plate capacitor. (They claim a permittivity of 19,861 for their composition-modified barium titanate dielectric- absolutely astounding, if they can do it reliably.)

A promising technology, yes. Car applications- for sure, especially for capturing regenerative-braking energy, or as a short-term buffer for electric-drive vehicles with a small gas generator (ie, Chevy Volt et al). To use it as the sole energy storage device may prove a bit more challenging, although not impossible; an efficient and economical way of safely regulating a source that varies from a few hundred to 3500 V DC will be necessary. It may also see use as a buffer system for wind/solar installations, or as a backup supply in houses, businesses, etc.

 

The S-C will serve as a short term buffer in conjunction with a battery and reduce the design requirements of the battery which should improve performance and costs in that area.

There a 1.5F, 3V capacitor available back when I took an interest in capacitor performance, around 1979, but that was a tiny thing (1" dia) mounted on a circuit board. It was a ceramic capacitor and therefore bipolar.

The increase in capacitance is not much but the S-C's much greater size and weight, but the improvement in the operating voltage is dramatic and that increases stored energy in proportion to the square. An electrolytic capacitor stack back in the 70's with similar capacity would have weighed around 2.5 tonnes.

 

The patent text describes an inexpensive way to manufacture multi-layer ceramic capacitors. These devices are not new, they exist several decades already, and so does barium titanate, which sounds like a salt but in fact is a complex oxide.

The 3.5 Kv working voltage is unusually high for this type of capacitor, but that is probably because the industry does not need caps for such voltages. With lower voltage, i.e. 50 volts the devices are cheaper and smaller.

Practical use as power storage device is something I cannot judge: as far as I know there are no reliable low cost MOSFET's that could be used for a switching power supply in the 10 Kilowatt range. But given time, that may change. Planning this technology for a soon to be released electric car seems a bit premature to me.

 

A MOSFET that can handle tens of kilowatts at 3.5 kV, at a price that would let you put it in a mass-market car.... that would be impressive indeed.

The ZENN car is already on sale in a few places, but is not street legal in many jurisdictions because it can't keep up with 60+ km/h traffic. Perhaps they have something in their R&D lab that will be able to control the EEStor capacitor....

As I've mentioned before, 3rd-party bloggers with lots of interest but somewhat less technical knowledge have been blowing things out of proportion somewhat. Charging the EEStor capacitor in 5 minutes may be theoretically possible, but no sane electrician is going to install the requisite thousand-kilowatt, 3.5 kV power feed, transformer and charge controller in a homeowner's garage.

 

dam interesting thread kids

 

Actually, looking at their chart from the patent, it would be a VERY viable energy source (with no batteries) for an elec. car, as long as you could regulate the voltage. If you believe the claims in the chart it's lighter, smaller, faster charging, and has a slower energy dissipation rate than any curr. battery technology...though the cost would most likely be astronomical at the moment.

I also ran a quick equation for their (3-6 minute) charging time, it worked out to 522.2-1044.4KW @ 3.5KV ... I'll PASS on having that monstrous powerline anywhere on my property....anyone happen to know the flowrate of the bare high-tension treble wires?

Also, won't 3.5KV bridge about a foot (.28M) of air at 1 atmosphere & 70% humidity??? doesn't sound like a very safe thing to have in your car where "backyard mechanics" would be getting electrocuted left & right by it!

 

A typical transmission line in the 115 to 350 kV range would likely have a summer thermal ampacity rating (ie, the maximum you can put through it on a hot day without overheating the lines) somewhere in the range of 800 to 4000 amperes. Depends on the particular conductors being used, of course.

Mechanics (and firefighters) are already somewhat scared of the batteries in current hybrid cars, and rightly so. A whole new level of training is required for anyone planning to work on high-power electrics.

 

OK, so if I'm doing my math right, you're saying that (on a hot day) these high-tension lines can carry between 92MW-1400MW
In essence, this tells me that our current power grid has room for, say, 85K-1M of these capacitors per state...assuming all other power usage was stopped completely...and for an "average" car with a respectable range of at least 300mi, we're talking about what, 4 capacitors/car? Obviously, our power grid would need a LOT of work before eny form of electric car for the masses is possible!!

LOL, for some reason I'm having flashbacks to 2003....whole eastern 1/3 of the US was without power because of an overheated high-tension line in OH starting a "cascade effect" and blowing out substations across the map!