Every time someone writes a diary about the latest electric car or battery technology, someone makes a comment about how easy it'll be to own an electric vehicle.
How we'll be able to plug them in, and in 10 minutes you'll have a fully charged vehicle, ready to drive 250 miles in comfort and style.
Bollocks!
There are several problems here, and I'll address them as best as I can in logical steps. There are advantages/drawbacks with electric vehicles, and the way our electric grid will need to be massively modified to permit them to become more than a microscopic amount of the vehicular fleet.
To give you an idea of the scope of the problem, consider that the engine power derived when someone floors the gas on their Accord or Camry V6 is roughly the same as the average electrical power used by all of the houses in a town of roughly 1000 people. Even the Prius' gas engine could do a small village of several hundred. If you added up all of the cumulative power derived by the vehicles in the US on a given rush hour, it would more than likely be greater than that used by all of the households in America at that time.
First, a little theory. You get a car, put a battery in it, charge the battery and run it.
Simple, no?
Modern cars average about 1500 kilograms. That's about 3300 pounds, or a typical American family of four. (Sorry, that's was a Clarkson joke waiting to happen.) Most cars zoom about at highway speeds consuming (at a quiescent state) about 15 to 20 horsepower, or to convert it to an easier unit of measure between 10,000 and 13,0000 watts.
The average home in America consumes a shade under 8100 kilowatt hours of electricity per year. A typical year is 8760 hours (not including leap years; people do not use any electricity on the leap day) so on average we use just under 1 kilowatt of power.
Most households have 120 volt service. Your standard outlet is a "5-15" socket capable of providing 15 amps of current. Going back to my last diary, you'll remember that power is the cross product of current and voltage, so each outlet in your house is capable of delivering no more than 1800 Watts. The odds are that each outlet is attached to a circuit breaker that is capable of no more than this, or maybe one that is able to provide 20 or 30 amps. There is a basic reason for this- the wires going from your master circuit breaker box to your outlet are probably 12 or 14 gauge wire (for practical purposes, the "gauge" of a wire describes how many wires would span exactly one inch, so fourteen 14 gauge wires pressed together would be one inch thick, and 1/14th of an inch wide) and according to UL or ANSI specifications these wires should not carry more than 25 or 20 amps over distances.
So we have established that your typical car needs 10,000 to 13,000 watts to maintain a highway speed of roughly 60 miles per hour. This is a very convenient number to use because it is exactly a mile a minute, which makes these equations easier to understand and get the feel for them. But more importantly it is very nearly 100 kilometers per hour, which is another frequently used figure of merit. Each mile driven will require 12,000 watt/hours divided by 60 miles/hour, or about 200 watts.
Using that hypothetical "car" whose actual specifications are not too far south of the Tesla, in order to achieve a 240 miles range a vehicle would require 4 hours worth of charge, accelerate very rarely (regenerative braking is very inefficient, capturing a small fraction of the energy used in accelerating a car to speed) and drive pretty much in a straight line.
Taking any curves would reduce the range, but failing to do so may reduce both the vehicle's and the owner's life expectancy. When a vehicle takes a turn, it translates some of its speed in one direction to the new direction, but it loses some to friction.
You can't turn the radio on- even at a relatively low volume your car stereo uses about 20 watts. So in 4 hours, that's 80 watt/hours of energy, or about 4 tenths of a mile. Trivial, I know, but suppose you have to do more than simply turning on the radio...
If it rains, your tires will lose traction. This is a small fraction, but it might account for a few percent, maybe 5 or 6 fewer miles range. Even worse will be the effect your headlamps have on your car- some really bright headlights use as much as 200 watts. For argument's sake, lets call it 100... that will increase your car's load by about 1.5%. Not much I know, but you've just lost four miles.
But what if it is cold, or too hot??? A typical car heater draws its heat directly from the radiator, essentially stealing heat from a source that is designed to eliminate heat. You're almost getting something for nothing here, and in fact if your car is overheating due to excessive load turning on the heater is the first way to eliminate some of the problem. But if you need to generate heat in an electric vehicle, the only way to do that is through resistive heating elements. For a reasonably sized vehicle, that'll be at 500 watts. So on our hypothetical foggy, rainy, cold night we've gone from 12,000 watts/hour to 12,600. On your hypothetical 250 mile ride, you've just lost power 5 miles from home. Hope you are on a busy road, because its a cold and rainy night!
But what if it is a hot and rainy day? A typical automotive AC can use 3000 watts, or a staggering 25% of the vehicle's engine output at quiescent speeds. Combine that with the headlights and the stereo and soon you'll find that the maximum range has shrunk from 250 miles, to a shade over 200 miles.
The main drawback for electric vehicles has always been the rather dramatic recharge time, versus the relatively short time required for fossil-fuel vehicles, or hydrogen. That hypothetical 250 mile vehicle needs no more than 5 minutes to refuel, even if that fuel is CNG or hydrogen. But unless we can overcome some spectacular infrastructural hurdles, you can't do that in an electric vehicle in less than several hours. To speed this up, I'll do it as a bullet-list, and I'll replace "watts" with the industry standard kilovolt-amps, or "KVA".
- Standard home plug max capacity 1.8KVA = charging time 32 hours.
- Home charger max capacity: 20KVA = charging time ~3 hours.
- Street-based high power charger max capacity 50KVA = charging time 75 minutes.
Remember what I'd said about the average home using (on average) less than 1000 watts? Most of our houses are wired for no more than 100 Amp service, or 12KVA. Some homes have "two-phase" service, which is for all practical purposes twice this amount Our 20KVA charger would just about max out your home. And your house is connected to a transformer on the street, which provides power from your local utility to your home. Power is transferred to this transformer at a much higher voltage than what you are using, and is then "stepped-down" to reduce the amount of power lost between the power plant and your home. Most transformers are in the 10 - 100 KVA range, and supply a dozen or so homes. A very large pole transformer is 75KVA; if everyone charged their cars at the same time (let's say, after coming home from work) that dozen homes would use more than 4 times the absolute maximum available!
Right now, all of the homes in America use a bit more than 100,000,000 KVA.
Let me state this in a way that many can understand- to switch to an 10% electric fleet we'd have to completely and totally renovate the entire US electrical distribution system. If you replaced 10% of all cars on the road today with electric cars, and charged 20% of them at any given time, those five million vehicles would use as much electricity as all of our residential homes COMBINED.
And that is if we use three-hour charging rates, not "ultrafast" chargers.
There are still a few more problems. The best conversion equipment out there today creates losses of at least 10%. Your 20KVA charger would create 2KVA of heat, the equivalent of two medium sized space heaters. And the connectors required to pass that much juice would be significant, you'd need about a square inch of contact space, and massive plugs. Now most high current home plugs are not designed to be connected for several thousand times in their lifetime, they are really designed for only a few hundred "in and out" cycles. And they cost a few tens of dollars each- not really that significant when compared to a $30,000 vehicle, but it is another added cost. The charging station itself would cost a few thousand dollars, and you'd need an electrician and probably a dry wall guy to install it. Again, not very significant but you're starting to talk money here.
Pumping amps into a battery requires very high current semiconductors to rapidly adjust for charging load. You need to reduce the charge dramatically near the end, to a "trickle" charge or else you risk damaging the battery. This isn't as efficient as simply turning on the taps full blast. This isn't a technological challenge, we've got more than enough thyristors around, but they aren't 100% efficient, and they aren't cheap. It is critical that the battery, charging circuit, switching circuitry and connectors are all working well, or else you will generate excessive heat which has the potential of significantly reducing battery life. And bear this too in mind- when they say a battery is good for x charge and discharge cycles, is that at 25°C, 75% relative humidity and standing still, or is that for a vehicle whose engine compartment might be 80°C and -40°, is subjected to serious accelerations from almost all angles, and under widely varying loads?
There are other issues, such as efficiencies of scale, which might actually work in ways contrary to what people think. Adopting a specific battery technology to a large degree would increase the cost of its raw materials significantly, which would not only increase the cost of the battery, but of secondary devices which utilize the same elements.
Someone here is bound to say "but wait, this new battery claims to be able to charge in 10 minutes!" Sure you can charge the battery in 10 minutes, but there's about 2 or 3 THOUSAND of those batteries in the car. In order to charge a 250-mile capable EV in 10 minutes, you would need to deliver roughly 60,000 watt/hours of energy in 10 minutes, for an average load of 360,000 watts. That would require, at nominal household voltage, 3,000 amps. There aren't many wires in industry today that could contain all of that current! Do you know the cables they use to drape the decks of suspension bridges to the main cable? Well that's a good idea of the wire you'd need, and you'd need two of them. And that transformer on the pole; well you'd need to have one 5 times larger than that just for your car to charge. This isn't about "new technology", but about the practical applications of the laws of physics, and it frankly amazes and astonishes me that people (who think they are actually well-informed) don't understand this.
Now one proposal is to redesign the batteries to be rapidly retrofitted to the car. You take a discharged battery, pull it out, and install a freshly charged one in a few minutes. The mechanics of rapid removal and installation of a 300 pound battery is a technological challenge to say the least, but I think the bigger problem is economics. First of all, you'd need to have a fresh battery available for each customer. So for all practical purposes, for weekends where people might want to joyride their vehicles, you might need to have a replacement for perhaps 20% of the entire fleet. Who is going to pay for these batteries? And more to the point, who owns them?
If the stations own them, then they would have to have a significant amount of money invested with a very slow rate of return. Naturally each individual customer would have to "pay" for this, which would dramatically increase the cost of a refuel. Instead of paying for the $2 worth of juice, and the $5 for labor (calculated at a reasonable $60/hour mechanics rate, which is about half the current amount), you'd have to pay for that prorated share of the battery's life, plus interest. If the battery would cost $10,000, and it could be recharged 2500 times, you'd have to pay $4 for each refuel to amortize it, as well as a nominal "profit" for the shop owner, perhaps an additional $4. So now for each $2 of electricity you're installing, you've now got to pay $2+$5+$4+$4!
This also requires standardization, something automobile manufacturers aren't that willing to provide. What is the use of R&D, if you then give away your results to everyone? This would require heavy licensing fees, with the "victorious" design company receiving royalties for each battery manufactured. Do you see Ford and GM (or Honda and Toyota, BMW/MB/Audi, etc...) entering into an agreement, or do you see them trying to compete for each customer individually? And how to you influence Chinese companies who have a miserable history of IP abuse to pay a royalty? Would we soon see knock-off batteries with a tiny fraction of the life expectancy on the black market? How do you prevent the theft of a multi-thousand dollar battery that is designed for very easy removal? The legal and economic ramifications are major.
Now bear in mind that each battery you "return" will not be empty, unless you push your car into the service station. Even if you go for broke, and go until you have less than 10% of the juice in it when you replace, you will still be paying the same amount as if you had 0%. Unless there are a significant amount of stations available, each with a large amount of stockpiled replacement batteries, you can't take a significant trip without the risk of running out.
Where on earth is the incentive for owning an electric vehicle?
I really think (as do the people from BBC's Top Gear, the world's most influential automobile television show and magazine) the future is in rapidly recharged fuel cell vehicles, or perhaps hydrogen. While these technologies have the potential to be more expensive than battery operated vehicles, they also have the advantage of immediate recharge. Fuel cells have the mechanical advantages of batteries, and their only exhaust is water vapor. Hydrogen has a disadvantage in that it has a tendency to leak (thought I'd say "explode", didn't you?) a percent or two each day. H2 is the smallest, lightest molecule in the universe. There is no seal perfect enough to prevent leakage. But rechargeable batteries do self-discharge as well, but they take longer.
I don't want to come off sounding all "doom and gloom", but I see more potential problems here than advantages. Electric vehicles will have a market presence, and will occupy a significant niche but I can't see them having a very dramatic effect on the market, for at least a generation. And by the time they reach prime-time, I think they'll be surpassed by other systems which do not have to pay the recharge time penalty.
Note: It was suggested that I use the "energizing America" tag. I'm not sure this really fits, but gotta keep the customers satisfied.