Dan's Data letters #171Publication date: 24 July 2006.
Last modified 03-Jul-2012.
(Except of course, in this electric-Mini, the generator doesn't come out.)
Well, it's vaguely similar, except the numbers are all screwy.
It's not very technically difficult to make an electric car with these monstrous power and torque figures, but - to start with the least important problem - the absence of any mechanical brakes means you'd never be able to put the thing on the road legally in most nations. If an electrical cable fails, this thing has no brakes. Also, once the ultracapacitor's full, or if you exceed the 700 amp input current for it (easy to do when you're slowing a ton of metal from 60 miles an hour), virtually all of your braking energy has to be liberated as heat somewhere, which creates its own engineering challenges. The energy that makes plain disc brakes glow dull red in even a normal passenger car if it's braking down a long hill (which is why you should use engine braking as much as possible if you're doing that) has to be dumped somewhere else, which in this case presumably means fat resistors with air ducts to cool them.
For this reason, most electric cars have mechanical brakes, even if they've got a fancy regenerative system as well.
A more important problem is that this thing uses a moderately high power petrol two-stroke as its charge source. Or maybe not - it says two-stroke at the top and then, as a reader's now pointed out to me, two-cylinder four-stroke further down. If it really is a two-stroke then it can't be fuel efficient whatever way you slice it. Today's quiet and refined portable generators are all four-strokes, for very good reason; you use a two-stroke when you want lots of power from minimum weight and don't much care about leaving a trail of blue smoke. Whether two- or four-stroke, the engine in this car seems to be a small motorcycle powerplant, or something.
The numbers don't add up, either - the motor's rated at 15kW, but the generator it's driving is somehow able to make 20kW.
More numerical issues arise with the battery output power.
300 volts at 700 amps is 210 kilowatts. That's a lot, and it can be very briefly boosted by whatever's stored in the superultramegacapacitor bank, but that's not much more. The caps are allegedly good for another 350 volts at 700 amps, peak, with a capacity of 11 farads, which is huge for caps - it means 245kW. But only for 0.016 seconds. Since capacitor terminal voltage changes with charge state, a cap bank like this will actually only give you 245kW in the first instant, then fade away as the charge dissipates over a period rather longer than 0.016 seconds. You'll get the same amount of energy as you would if you got 245kW for 0.016 seconds, though.
Anyway, that's all you get. Given the very small capacity of the cap bank compared with the batteries (which is why even ultracaps aren't useful for real bulk energy storage), you've effectively got only 210kW to play with, which is 286 horsepower - and not at the wheels, either, though modern electric drive systems can be extremely efficient, so you'll probably end up with more power at the wheels than you would with a 210kW engine attached to a normal manual transmission.
So that total-power-in-excess-of-640hp thing has to be baloney, unless some of the other numbers are wrong.
The thing'll still go like stink, because of the huge any-speed torque of the electric motors. But the fact that it's got a mere 286hp to play with could explain why its top speed is a mere 240 kilometres an hour. A Mini that really did have F1-engine power levels would top out much, much faster - transmission, tyres, disused runway and testicular dimensions of the driver permitting, of course.
There's no mention of the speed at which the vehicle achieves its excellent range, either. The 70Ah battery discharging at its maximum 700A will, you'll be unsurprised to learn, run dry after six minutes. Running at top speed for that period of time will take you a big 24 kilometres, not the quoted 1500. As a matter of fact, even if you only cruise around at an average ten-kilowatt power level, you'll still run the battery flat in two hours, and will probably not have covered more than 100km, in real-world driving. Regenerative braking helps, but it doesn't help that much - how much fuel (two-stroke or otherwise) is this thing carrying with it, and how slowly are you expected to drive it?
I presume they stuck with the teeny generator because they didn't have room for anything else in the prototype, and I further presume the car can be plug-in charged. If it can't be, though, you'll probably find that the poor economy of a two-stroke in the first place, plus the further losses in the charging process, give this revolutionary breakthrough electric vehicle similar MPG figures to a plain old V8 sedan. Which you really might as well buy instead.
A big old muscle car isn't going to surprise you with a terrifyingly expensive battery change after a few years, for a start. That Mini could easily have $US14,000 worth of batteries in it.
(The batteries would be a great deal cheaper if they were lead acid, but that'd turn a 150-kilo-ish pack into a 700-kilo-ish one.)
The MDI Air Car seems like the kind of thing you would be interested in, so I was wondering have you heard anything about them?
The bottom line is, these guys claim they can make a car that goes a 100km for a cost of 1.5 Euros or less. And that car would be rather fast (135km/h), and autonomous (250km), and all is sweet and dandy.
The problem is - I smell a big fat rat! I mean, if everything is as they claim, then where's the hold-up? Could it be that this is no more than a simple hoax?
Please look into this, you da man!
Someone signing himself Joe Pesci
The MDI cars are the ones that usually come up in when people are talking about modern compressed-air cars, and they do indeed seem to be (compressed) vaporware.
There's nothing wrong with the concept of compressed air for automotive energy storage, though. It's been used as an adjunct to other propulsion systems as well; steam engines run fine on compressed air, for instance, so you can use a small air tank to move your steam car while the boiler's warming up. Compression brakes on trucks are also half of a compressed air power system - the racket a truck makes when it's compression braking is from the engine working as an air compressor, and I remember seeing a regenerative braking system that stored that air in a tank and reused it for acceleration.
The MDI system's a hybrid, too; on top of the reversible "moto-alternator" that gives the car regenerative braking and allows it to charge from electric power, there's supposed to be some kind of optional heater thing that gives the cars their long highway range.
Super-compressed air is a pretty decent energy storage system, and there's no technical reason why you can't safely store it in a vehicle. LPG-powered cars are safe, and ordinary petrol cars are carrying a huge amount of energy around in their fuel tank as well. Of course, if you screw up with a 400psi air tank, it is likely to be pretty dramatic; it's much harder to induce a gasoline vehicle to explode, outside the movies.
The down side of air energy storage is that the energy is not free - you need power to compress air. And the whole process is pretty miserably inefficient. Neither the compression nor the motor is setting any records for energy conservation, especially if you don't get clever about storing the heat of compression. But, as with electric cars, air cars let you move the pollution somewhere else, which is good. And unlike electric cars, air cars don't have any battery to wear out. Then again, charging batteries is inefficient, but electric motors are commonly something like three times as efficient as any air motor. Swings and roundabouts.
In the final analysis, there doesn't seem to be a lot that air cars can do that electric cars can't, and you can pretty easily charge an electric car anywhere that's got electricity. Air cars either need MDI's complex reversible compressor doodad, or a high pressure fill line; the dream of sneakily filling your car at the service station for free won't work too well, because free service station tyre-inflation compressors top out at about 150psi, and don't have much flow rate at that pressure, either. So you'd be standing there grinning cheesily at the gas station attendant for some time while you trickled enough air into your car to take you 20 miles down the road.
Air-only running costs for a machine with very good regenerative braking may indeed be very low, but it's not of course realistic to only look at what you're paying for "fuel", when other running costs for new and exciting vehicles are commonly much higher.
After this page went up, a reader pointed out that the MDI site's tests page took a test vehicle whose range was a not-very-useful 7.2 kilometres and, I'm trying not to say "inflated", the results to say their vehicles had a 242 kilometre range. They based this on claims that the vehicle they actually tested was not nearly as light and efficient and pumped full of air as the vehicle they, um, might build some day.
The tests page has unaccountably vanished from the MDI site now, but it's archived here.
These aren't fuel cells, in the sense of being a thing that accepts hydrogen or methanol or whatever and emits electricity. They're zinc air batteries, as have been used to power hearing aids for many moons.
Zinc-air batteries have some fuel-cell-like qualities, but are from a consumer's point of view just another non-rechargeable, non-refuelable battery. Except that after you break the seal, zinc-air batteries will be flat after three months, whether you use them or not.
(I also mention them at the end of this column.)
While these "Power Cartridge" things are small, light and neat, like the hearing aid batteries, they'll only charge your phone for slightly longer than a similar-sized pack containing three or four AA alkalines. Three C alkalines will give you more than twice as much charge time.
There are numerous "battery extender" products out there for phones and MP3 players and such - packs for disposable batteries, rechargeable packs, maybe even solar doodads. Pretty much all of them are better value for money than the "Power Cartridges". Unless you're climbing a mountain or being shot into space, the extra weight of one of the other devices is unlikely to bother you.
(And then there's this thing, which looks pretty neat, but of course is not yet for sale, just like every other fuel cell product that looks pretty neat.)
Go on - just imagine it!
Then, when you've finished imagining, could you tell me whether it actually makes any sense?
Oh yes, just imagine! Why, 400 billion silver ions would be 72 whole picograms of silver!
(Well, it ought to be, anyway. I used my child-like Excel skills far too much in the formulation of this answer, so I confidently expect someone to e-mail me with corrections in the near future.)
Or, to put it another way, if they had one gram of silver being nano-electrolysed into the washing at a rate of 400 billion ions per wash, that one gram would last for 13,957,175,284 washes. At one hour per wash cycle, that'd be 1,592,194 years.
The FAQ only claims that the plate will last for 2000 wash cycles, which suggests that it'd be better described as a "very thin plating on a quite small plate".
I'm not sure what the actual silver concentration you need to make a solution an effective germicide is, because my quick Google searches were severely contaminated by hordes of rapidly breeding colloidal silver quacks. I think it's around 100 parts per billion for "eventual" germ-killing. Let's assume that's all that's needed for the alleged "up to 30 days" antibacterial action.
100ppb of silver in water, further assuming that we're talking mass/mass here, means that you've got 0.1 milligrams of silver to each litre of water. But 0.1 milligrams of silver still contains 5.6*10^17 atoms.
Assuming the washing machine uses 50 litres of water per full wash, that'd be 2.8*10^19 ions actually needed. The error factor between that and the quoted 400 billion is therefore about 69,785,876. They're giving you a bit more than one seventy-millionth of the amount of silver they need to, to do the job they promise.
The heck of it is that even with today's rather high precious metal prices, silver still only costs about $US11.55 per troy ounce; a troy ounce is 31.1 grams. 0.1 milligrams of the stuff, therefore, is worth about 0.004 of a cent. A mere dollar worth of silver would provide for 26926 washes, more than 73 years of daily loads, if Samsung actually cared to do what they say in the ad.
But they don't. Unless some marketer's just gotten the wrong end of the stick and slipped about seven orders of magnitude, Samsung would appear to be lying to us.
The charger for my Black and Decker 14.4V Firestorm cordless drill has gone out. I didn't think it was possible for something so simple to break. So now I'm stuck in a really dumb situation. I hardly ever use the thing, but I bought it using the usual power tool rationale: While you hardly use it, it's indispensable when you need it. Except that now I hardly use it and when I need to I STILL can't use it.
I know that a replacement charger is only like $20 on eBay or something, but I cut the cord and it seems the only problem is that the listed voltage isn't getting from the wall wart to the cradle jobbie. Surely I can just make something out of a few coils of wire and attach it to the (still not burnt up) cradle. Would this be foolish?
The charger says it's supposed to put out 17.4V 210mA, but it sure isn't. Thanks for any stern warning you can offer.
If it's just a fractured wire, you can fix it. They usually fracture at the wall-wart end, so you just open it up, unsolder the wire, lop off a bit of cable until you're past the fracture, and solder it back on. Find instructions here.
If the wall wart itself isn't working, it might be a popped fuse, which is of course also easy to fix. Many modern AC adapters don't have fuses, but there really isn't much else in them to break but the cable.
Assuming the thing's actually toast, then buying a new $20 charger is the most economical option.
If you splash out some more dollars on a proper smart charger that can handle a 12-cell pack, though (14.4=12*1.2), you could easily hook that charger up to the drill-battery cradle when you need to, or to any other NiCd/NiMH battery you need to charge.
You can get very fancy chargers surprisingly cheaply these days. This, for instance, charges pretty much anything you care to name, and goes for under $US100. Like a lot of hobby chargers, it runs from 12VDC itself, so you can't just plug it into the wall, but as the above review mentions, you can run these chargers from an old PC PSU. 12V car battery chargers also work fine as power supplies for smarter chargers like this one.
Note that cordless tools seldom use fast-charge cells; don't use a charge rate that'll fill the cells faster than the stock charger did. Feel free to use a lower rate if you want the cells to be happier - the stock chargers often push the cells too hard.
Here in Long Island, NY, ads for the Power-Save 1200 are on TV. "Reduce electric usage by OPTIMIZING the power to each of you appliances!"
With a single box wired into the main circuit panel. Ha!
The Power-Save 1200 people even go on to say that the thing's a whole-house surge protector.
I was interested to see the "university study" (PDF) that allegedly confirms this gadget's effectiveness. It's from Santa Clara University, which is a real institution with a real engineering department, and the authors appear to be real people. But this study starts out reading like a rah-rah piece for the Power-Save, and then fails to actually support the claims made for the thing. If the study's to be believed then the Power-Save - or, at least, the device they tested - really is a power factor corrector of some kind (I've talked about them before, here and here). But since few (if any) countries bill household electricity consumers by power factor, that doesn't matter.
Household electricity meters, as I've mentioned before, ignore power factor very effectively. Swap out the old-style PF0.7 power supplies from your twelve computers for new shiny PF0.99 ones, or install a whole-house power factor corrector, and there'll be bugger all difference in the speed at which the little meter wheel goes around. You'll be doing your bit to reduce unnecessary load on the power grid, but you won't be saving any money.
The "study" doesn't mention this. Nor does it say anything about surge protection.
Hey, what about the DoE report (PDF)? Well, that says that "many utility companies" "usually" charge extra for bad power factor. That's true for commercial customers, but I've never heard of it happening for residential ones. It's possible, especially with modern electricity meters that no longer have the spinning disc, but as far as I know power companies usually just install their own capacitor banks in substations, rather than honk off their customers by billing them extra for something they don't even understand.
The DoE report is clearly labelled as being part of their "Motor Challenge" program. That's aimed at industry, not householders; it's talking about production lines, not washing machines. Once again, though, the Power-Save people don't go out of their way to point out that their supporting evidence is not in fact supporting them.
What else have they got? Um, some stuff about tax incentives for energy-efficient products "like the Power-Save 1200!" ...but not actually, you know, including the Power-Save 1200. Actually, the term "power factor" does not seem to be used anywhere on that site.
I wouldn't be surprised if the Power-Save people have some genuine testimonials, though. People who sell worthless fuel mileage improvers also have them.
(The people on alt.engineering.electrical found the Power-Save so uninteresting that they wandered off into a discussion of more straightforward scams after the first couple of posts. Here's another unimpressed commenter, talking about the Power-Save and an allegedly related device called the "KVAR Unit", the patent for which can be found here. If you just can't get enough of bogus power savers, I've blogged about different versions of them here, here, here, here and here!)
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Needless to say, I didn't sign up for a webinar, download a whitepaper or fill out an online form on the Topica site. Well, unless you count the "unsubscribe" form I foolishly filled out when I first received a message from these people telling me I'd just subscribed to blah blah blah. Hey, it looked like legitimate (for suitably small values of "legitimate") marketing crap to me; I presumed they actually had subscribed me by mistake, or at least weren't so elbow-suckingly stupid that although they'd subscribed me accidentally-on-purpose, they'd ignore clear evidence that I definitely didn't want to hear from them ever again.
Needless to say, Topica are in fact a bunch of mildly famous spammers, and they have a long history of taking no notice whatsoever of never-contact-me-for-any-reason requests, whether those requests are about mail from Topica themselves, or from their clients. After I filled out the unsubscribe form, I got a couple of other cheerful spams from them before Harry's turned up.
I don't think any of these people quite qualify as evil jackasses, but your opinion may differ. If you're feeling chatty, go ahead and call or e-mail Harry and talk to him about this, or anything else you like.
He'd do the same to you!