Zenn Electric Car
The amount of energy that can be stored in a capacitor is determined by the formula:
E = (C * V2) / 2
E = Energy in Joules
C = Capacitance in Farads
V = Voltage
Being able to increase the voltage improves the storage capacity exponentially as the voltage increases. For example, conventional capacitors operating at 2.7 volts would require 45 million farads of capacitance to hold the equivalent of one gallon of gasoline (12.7 KWH). At 400 volts (a number I picked for comparison purposes only), a capacitor would only need 560 farads of capacitance. (EEStor actually hopes to get 3.5KV which would only require 7.3 farads.)
The production of these new capacitors has been delayed; my guess being that they are running into engineering problems trying to bring this technology from the lab to commercial scale production. When they are produced, Zenn Motor Company is planning on using them to power their all-electric vehicle. [I actually saw a Zenn all-electric car on the way to work today. Was in the city and I assume this car was running on lead-acid batteries.]
Assuming that supplies of this new capacitor may be limited, or that the capacitor may not be as inexpensive as EEStor expects, the best value-add for this technology will be for use in gasoline electric hybrid vehicles. A gas electric hybrid vehicle will typically get between 20% and 30% better fuel economy than a comparable gas only vehicle. It gains this advantage by using an energy storage device like a battery or capacitor, to smooth out the power flow from the engine and to recover the energy from braking. An engine that doesn’t need to provide bursts of power for accelerating can be smaller and can be tuned to only run in its most efficient power range. You don’t need a lot of capacity to perform this type of energy buffering. My guess is that about 300 Watt Hours (wh) would be sufficient. That’s the energy equivalent of about 3 ounces of gasoline or enough power to drive a 40 mpg car about 1 mile. This obviously would not work as a plug-in hybrid, but the technology could turn a 30 mpg car into a 40 mpg car.
Why not just use a 300 WH battery? The problem with a battery of that size is that it probably would not be able to produce sufficient current to drive the car. A battery has limitations on how fast it can charge and discharge. Because a battery changes chemical composition, it can degrade after too many cycles and start to loose its ability to hold a charge. A battery can also be very sensitive to temperature. You need a large size battery to be able to provide enough current to provide acceptable acceleration.
None of these should be problems for a capacitor. Because it is a solid state device, it should charge and discharge very fast. Because there is no chemical change, it should have a virtually unlimited number of cycles and should not be very sensitive to temperature. That means the capacitor buffering device can be relatively small.
A capacitor could also be used with a battery pack for plug-in electric hybrids (if battery storage is cheaper per wh). The battery in this car would not have to be as capable because it would only be used to recharge the capacitor. Charging the capacitor could be done at any power level, much in the same way a camera flash uses a capacitor to build up a charge from the battery. The battery in a camera can not produce enough current to provide the burst of power for the flash so it builds up current in a capacitor that is discharged to produce the flash. In this mode the battery provides an electrical assist to the car in a similar manner that the battery in a Toyota Prius provides a mechanical assist to the car.
|
At 40 MPG |
|
|
|
Trip Distance |
Miles Per Gallon |
% Commuting |
|
5 |
infinite |
10% |
|
10 |
80 |
10% |
|
15 |
60 |
10% |
|
20 |
53 |
10% |
|
30 |
48 |
20% |
|
40 |
46 |
18% |
|
50 |
44 |
7% |
|
60 |
44 |
5% |
|
70 |
43 |
3% |
|
80 |
43 |
|
|
90 |
42 |
|
|
100 |
42 |
8% |
|
Average Commuting MPG |
52 |
*8% Assumes all Commuting over 70 miles averages 100 |
If the capacitor (or capacitor/battery combination) becomes slightly larger, say 1.6 Kwh of capacity, then a plug-in hybrid becomes practical. At 1.6 Kwh, a 40 mpg car will be able to travel 5 miles on a charge. If all the trips are 5 miles or less then the car would never have to burn any gasoline. If longer distances are traveled the effective mpg is still enhanced. Based on average commuting distances (10% numbers are my estimated breakdown of a single number for comparative purposes) then 52 mpg could be achieved compared to 40 mpg for a non-plug-in hybrid. [This chart is only to show the greatly increased fuel economy based on even a small storage device and doesn’t reflect any actual car that I know about.] The key point here is that the first small 300 Kwh storage device adds more value per device than each incremental storage device added.
If you could charge the car at intermediate points, then fuel economy would improve even more. The capacitor has the advantage of being able to store its charge very quickly. I could easily picture grocery stores, offering free, quick charges to their customers. Just like selling milk below cost to get shoppers in the store. 1.6 Kwh of electricity would be only 16 cents at 10 cents per Kwh.
Notice that the most benefit from the energy storage device is from the first 300 wh of storage. This improves the car’s mpg from 30 to 40 (assuming a 30% improvement) by going to a hybrid. The next 970 wh of storage improves it another 30% to 52 mpg on average. If EEStor’s device turns out to be more expensive than they are anticipating, it would still have a tremendous value add to hybrid car technology as a small device. You would achieve overall better fleet fuel economy for 211 cars each with 300 wh devices than one all-electric car with one 64 Kwh storage device. General Motors could use this device in their Chevy Volt.
This is the type of technological development that might qualify for the type of program that John McCain suggested should earn a $300 million prize. I would suggest that the government might offer tax credits on the purchase of hybrid electric, plug-in hybrid electric and pure electric cars as a way of stimulating demand. (John McCain also suggested a $5,000 tax credit to US Automakers for every zero-carbon emission car they sell.) Our automakers are going to need help if we expect them to make the financial investments in new, low carbon emission vehicles. Tax Credits might do more good than just offering a one-time prize.
I wish EEStor the best of luck in getting their new storage device into production. This is technology that could fundamentally change how cars are designed, significantly reduce our dependence on foreign oil, and improve global warming.
Comments
In an interview with EEstor CEO Richard Weirs and Lockheed Marting Clearly states the ultracapacitor will meet the original patent specs of 10 times lead acid battery
Weirs
"Go back and read what Lockheed Martin said about this. I think that's very exciting. They said two things. They said it works. And they didn't say it works with this or that caveat.... they just said it works."
Lockeed
Are you confident that their technology will offer a greater amount of energy and power density than batteries?
Yes, and at a fraction of the cost.
Do their caps hold 10x the energy at 1/10th the weight of a lead acid battery?
Yes.
Weirs
"And second, they said it could ramp up into a high volume production environment"
lockheed
Is there a production plan for 2008?
Yes for EEStor. Their approach is when they start manufacturing these batteries, not just the cells, but also the package assembly, they will be in production. If you can get a visit to EEStor they’ll show you their process and everything they’ve got in place to support that. Assuming that everything comes together in terms of tests and qualifications and that sort of thing, they will be ready to ramp up very quickly, because of the nature if the architecture and scalability of what they are doing.
http://bariumtitanate.blogspot.com/2008/05/how-fast-can-you-partner-part-2.html
http://gm-volt.com/2008/01/10/lockheed-martin-signs-agreement-with-eestor/
This makes two articles in a row in which Ryden has embarrassed himself by his ignorance of his subject matter. Calling the EEStor device "a capacitor" is not correct. Nor is his belief that it will only be used in hybrids. If Ryden were current on developemnt, he would know that the EESU's are slated solely for BEVs, NOT, repeat NOT
hybrids. They are o be used by ZENN Motors for their City Zenn, a 3100 pound car that will be produced by an unnamed OEM specifically to use this battery. Those lead acid ZENNs he mentioned have nothing to do with the cityZENN. That car is schedule for late 2009. Before that occurs, ZENN and EEStor will partnership on conversion business for fleet vehicles (taxis, postal delivery vehicles, etc.) which, as I should point out, do NOT produce plug-in hybrids, but BEVs. Ryden, if your bosses insist upon assigning you jobs concerning electric propulsion, hwo about coming up to speed and stop publishing this junk? This article totally sucks. Pure BS.
Kerry - First off the EEStor "Electrical Energy Storage Unit" (EESU) is a capacitor.
Second, I did not say that their storage device would only be used in Hybrids. I was making an economic case that their storage device would add more economic value as a small device in many hybrids than one large device in an all-electric car. If this device works as projected, I believe that the venture capitalists will look at putting this device into the most profitable markets available to them. My speculation is they will find this in the hybrid car market. They might be constrained by a supply deal with Zenn, but I do not know. Any deal can be modified if the economic incentives are large enough.
This article is nonsense. Eestor's EESU is not intended to be used in gas electric hybrids. Or even plug-in electric hybrids. Just pure electric vehicles. And in the conversion of internal combustion engined vehicles into electric ones.
Forget the arguments about whether this device is to be used in one application exclusively or in multiple applications, it's mostly baloney because of the hype and contention that this could make hybrid cars "a reality". Ever heard of a Prius? The author is living in the 1990s.
Oh, and also baloney because of the comparison to lead-acid batteries which are no one's idea of what should be in an electric or hybrid vehicle. All current hybrids use either nickel-metal hydride (NiMH) or lithium-ion (Li-Ion) batteries, as do the better pure electric vehicles.
A better capacitor could be useful to **improve** hybrids, and could be useful for pure electric vehicles as well. ANY good energy-storage technology can be applied to pure EVs, conventional hybrids, and plug-in hybrids, either alone or in combination with another storage technology (such as batteries) with complementary characteristics. A business that limits itself to just one market will probably not prosper.
If this new EEStor technology really holds more total energy than current NiMH or Li-Ion batteries for the same (or less) weight, volume, and cost, then it could be used as the sole energy-storage device in **all** forms of electric, conventional hybrid, and plug-in hybrid vehicles. If it turns out not to be quite the miracle it's touted as, it may still be useful in a "hybrid storage" configuration in which the capacitor provides surge capacity for power output or regenerative capture of energy while an advanced battery handles the bulk energy storage.
Oh, forgot to point out another area where the author is living in the 1990s: tax credits. He "suggests" them. Duh. They've been around for years, for EVs and conventional hybrids. (There aren't any commercial plug-in hybrids yet so that's moot, but they will almost certainly get tax credits too.
The credits for conventional hybrids are expiring because the market for them is already growing rapidly -- people are buying them even without tax credits, though other incentives also help, like the privilege the past few years of using the "HOV" (carpool) lanes coming into DC for a faster commute.
I believe that incentive may eventually expire too, because there are so many conventional hybrids that there's starting to be a backlash. (The Virginia exemptions on highways leading onto DC were supposed to expire July 1, 2007, but were extended for a year to this July 1, and were just extended again to July 1, 2009.) The incentives only apply to the most fuel-efficient hybrids, not to what Detroit likes to call "mild hybrids".
The same incentive may eventually apply only to the next generation, like plug-in hybrids. (You only really need to incentivize the leading edge technologies.)
Actually, I would say that if EESTOR is real, that hybrids is the worse use for this. Pure EVs would be surperior. Why should you carry around loads more weight when 400 lbs and 1ft cubed can take your car 300-500 miles? Even more important, is that it take the SAME LENGTH OF TIME for a "fill up". By going with a hybrid, you carry around not just mostly usless weight, but you are adding loads more pollution, maintence, and taking up a great deal more room. ALl in all, if we have licked the energy density issue, than the ICE should die.
Do some more math please people. To give a 6 minute charge to this invention would require another capacitor to accumulate the energy over time, then discharge into the "Back to the future" EESTOR "flux capacitor' I don't want to mess with the potential flashover!
What EEStor most likely has is an improved capacitor...even a 2 to 1 improvement is significant in the electronics industry. If EEStor sold the rights for electirc vehicles and military power sources and used the money to buy equipment to make capacitors, they really lost nothing and gained a factory to make good capacitors. The way the claims were written in the US patent don't make sense until one realizes that the claims are written to attract money. Would their investors really allow them to give away so much for so little? The EV business part of the story unfortunately does not make sense much to the disappointment of myself and others who believed it...at least for a while.
Is the device you are discussing this?
http://www.yesa.com.cn/pages.asp?id=4
YESA makes LiFePO4 batteries that are well repected in the electric bike community. I'm about to buy one for my ebike but if I can come up with the appropriate configuration to use supercapacitors, I'll give it a try. Note that the J2R7108B is rated for 1000F at 2.7V...
sschnelz: The capacitor I was talking about is being developed by EESTOR, not the one you are referencing. The yesa capacitor will not have enough power for your electric bike. Doing some quick math:
1000 * 2.7 * 2.7 / 2 = 3.645 Joules.
3.645 Joules / 3,5000,000 Joules per KWH = 0.001 KWH or 1 watt hour. That's about the same power in 1/2 of a AA battery.
The EESTOR capacitor stores power at 3500 volts. EESTOR is in development with this device, but have not yet proven it can be made commercially. I hope they are successful as it would cause a technological inflection point in the development of hybrid electric and electric cars, amybe even bicycles.
I have seen very few electric bikes and was expecting they would be more popular. Have you had a good experience with yours?
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