Electric Cars and Their Discontents

Electric Cars and Their Discontents 348

Posted by timothy on Friday July 21, 2006 @03:10PM from the discontent-is-necessary-for-progress dept.

The most hotly contested issue raised by yesterday's post about the lithium-ion battery-powered Tesla roadster is only tangentially related to the car itself; instead, it's the energy generation and storage required for electric cars more generally to operate. Read on for the Backslash summary of the conversation, including several of the comments that defined the conversation.

A typical comment about the global impact of switching from gasoline to electric cars on a wide scale comes from reader dbIII, who comments:

"Until something replaces Coal power plants as the main method of generating electricity, you're just replacing one evil for the other."

"With better battery storage it doesn't matter much where the electricity comes from and when - the car could be charging up with solar power in the carpark in the day or with wind when it is blowing, or off-peak when the base load stations are running as low as they can but no-one wants to use the electricity."

"Battery power isn't about saving energy anyway, it's often about shifting the pollution to a big facility that can handle it instead of having heavy pollution control equipment to move about. The first hybrid car I saw, back in 1987, embodied this principle and was designed to work at an underground mine. Above ground it ran on fuel, but below ground you wanted to minimize the air pollution as much as possible so it ran on batteries."

The continued existence of the earth as a habitable planet aside, what about the car itself, and in particular its power source?

Jah-Wren Ryel has a quibble with the terminology used the linked article, writing

"This car is not a true Tesla Car. If it were, it would have no batteries at all. Instead it would gets it energy from some kind of wireless source like microwave power transmission or even the Earth's magnetic field."

Many readers worried about exploding batteries; glowworm was "left wondering if this car is involved in an accident if the batteries will vent like the recent Slashdot articles suggest. Exploding Dells, fires on planes, and soon at an intersection near you... cars venting more flame than the Batmobile."

Reader nSinistrad_D provides reason to think such explosions are unlikely:

"Looks like the company that is manufacturing the batteries has replaced graphite with a 'Lithium Titanium Oxide' that they've tested and claim doesn't have the smoking, venting, or explosive problems of normal lithium ion batteries. Here is a link to a rather informative article about the battery technology that will be used in the Tesla. ... I mean, based on the stuff I've read about the founders of the company and a lot of the people who have invested in it (i.e. Elon Musk, Larry Page, Sergey Brin, etc.) I feel I'll wait and see before passing any judgement."

Reader artifex2004 is skeptical: "Here in Texas, where I suspect temperatures exceed battery design, I think this idea will bomb spectacularly. Seriously, though, Li-ion? I shudder to think of how those will get disposed of, eventually."

And Reader Moofie has a tongue-in-cheek solution if the batteries ever go critical: "Maybe you could design a clever little nozzle to get a boost from your on-fire battery packs. That'd be AWESOME."

It's not just safety, of course, that matters to drivers, but practicality for other reasons:

Reader iamlucky13 writes: "15 minutes on the charger might get you another 15-20 miles. And 220 volts at 70 amps is a pretty hefty 15 kilowatts, so to have a dozen cars sitting at the local McDonalds charging is going to be draining about 180 kW from their coinpurse. That is a serious amount of juice. Also, I'm skeptical that you'll be getting 250 miles at 70 mph. If I remember right, electric motor efficiency and power typically increase with load, but fall off with speed, which makes them awesome for say, a 0-60 run in 3 seconds, but marginal at best for high speed cruising. That 250 mile range estimate is probably at significantly lower speeds."

"Big rigs generally run around 5 mpg, but it varies quite a bit around that number depending on the truck, the load, and the speed. Few truckers drive at the most efficient speed because it increases the labor costs significantly."

"If you're suggesting running commercial trucks on electricity, forget it for the foreseeable future. It's definitely been considered. Not only is there the conflicting speed issues I mentioned above, but you run up against the energy density limitations of batteries fast. Assuming the numbers from the article are correct (I doubt it...something isn't quite adding up according to my gut) and unrealistically taking the charge/discharge at 100% efficiency, it's storing up 194 MJ. Gasoline holds about 120 MJ/gallon, so the 1000 pounds of batteries (according to the Tesla website) are equivalent to about 1.5 gallons of gas (6.3 pounds/gal). Divide that an efficiency of around 30% and you've got a 32:1 energy density ratio in favor of gasoline. For a truck to haul the equivalent of 150 gallons of fuel (actually diesel, not gas, but close enough), it would need about 30,000 pounds of batteries. But then you have to go farther and take into account that 2/3's of its cargo capacity has been replaced fuel, so you need to make 3 times the number of trips. And you've got a lot of trucks either sitting idle recharging or having their 30,000 pounds of batteries swapped out every few hundred miles."

"Obviously these are really rough numbers, but other engineers have already looked at the idea in more detail and rejected it."

"I'm not trash-talking the Tesla. It looks like a lot of fun, but like all sports cars, it's a toy and not a good comparison for commercial trucking. Most of a car's weight is itself, be it gas or electric. Most of a truck's weight is it's cargo."

"For the record, I think electric can work extremely well for short range commuting (5-10 miles on city streets), but if you travel far, you'll realistically be looking at gas."

As to the exact number of batteries in the car, reader wbean provides a good reason why it should be exactly 6831: "The motor is going to need a lot higher voltage than a laptop. This means that the batteries have to be organized in series/parallel banks. 6831 is a plausible number since it is 23 x 11 x 3 x 3 x 3. This gives you a lot of flexibility in arranging the banks. You could have 99 banks of 69 batteries in series, presumably giving you something like 345 volts. That sounds about right for a DC motor."

Of course, battery technology is the real crux of the issue; balancing safety, weight, volume and energy density is a tough problem, and as reader loose electron puts it,

"Whoever comes up with a significant advance in battery technology will . Li-Ion batteries have excellent amp-hour ratings for their size, but like all other batteries are still pretty limited."

"Acceleration/Torque for electric cars is not a problem. High performance capabilities are there if you want them. However, you are playing battery energy against performance against distance, and all electrics, or fuel-electric hybrids have been designed to be 'green' in their approach. (Any Hummer owners want an environmentally aware vehicle?)"

"Right now the weakest link in many electronic systems is the energy source. A good solution there and you can be a very wealthy person."

hotspotbloc suggests " a different type of hybrid," one with:

"enough batteries for ~50 miles.
a small (100cc) biodiesel engine running at a fixed and preset RPM connected to a small generator. The engine would be set to run at the peak of its power curve.
a small ~10L fuel tank
and
an AC charging circuit"

"This would allow the driver to run on electric most of the day and charge on the road when needed. One could also use a gasoline engine instead of biodiesel and still see big fuel operating savings since some wall recharging would take place. It would also greatly decrease the number of batteries needed."

"This is a really old idea. I saw something like this (on a much larger scale) on an USCG cutter (WLB-389) that was built in 1943. Two diesels -> two generators -> one electric motor. Worked great and it could double as a light ship."

Finally, several readers' comments focused on the merits of the particular electric car, rather than only as the embodiment of its constituent technologies.

fermion was one of a handful who talked about the car as a sportscar per se, writing:

"I would wager that this vehicle is more like a Lotus Elise, or a Corvette, or even a S2000, all of which can be had for under 50K. Any performance benefits over those sports cars can be attributed to the natural advantage of this car, namely that you can go from 0-60 without switching gears, and it is easier to get it perfectly balanced without an engine. Anyway, The true test of a sports cars, as opposed to just a fast car, is the handling, which was not mentioned in review. Without proper handling, it becomes a Mustang at 30K."

"Which is to say we are still in the same world, in which low volumes and other issues cause electric cars to be 50%-100$ higher than traditional cars. All that seems to have happened here is that an electric car has been targeted to the high end market and priced accordingly. It is kind of like taking the hummer, putting a cheap truck base on it, calling it an H2, and pretending that it still has the dubious value of the original."

"Oh well, I suppose if they can build a sedan for 35K I would be impressed. We would also have to look at maintenance cost of the vehicle, which would be dominated the battery replacement. A sports car car easily run 20 cents/mile in maintenance. Knowing that laptop batteries can only handle a couple hundred charge cycles, one can image where the long term maintenance cost could approach three or four time that amount."

"I wish we had electric cars. I think the technology is there, and the pricing could be reasonable. But even companies that could be using the electric car to revive themselves, for instance Mazda and Ford, still seem to be married to the antiquated internal combustion engine."

ChronosWS largely agreed with this, writing that "cars like the Porsche Carerra and the Bugatti Veyron (mentioned in a related article) are consummate sports cars -- they exemplify not only speed but styling, handling and quality expected of a car with their price tag. Cars such as the Corvette, especially the most recent incarnation, do so relatively inexpensively. But regardless, 0-60 acceleration is not the most important statistic, and often isn't an important statistic at all except to people who don't know better (I refer the undereducated to the more useful 0-100-0 or 0-150-0 tests, as well as relevant agility tests such as emergency lane change, slalom and skid pad.) Electric cars will be desirable when they meet the following conditions met [by] existing cars:"

"price (under 30k)
features (styling, interior, gizmos)
convenience (fueling in under 5 minutes)"

"This car does not appear to meet any of those."

Thanks to all the readers who took part in the conversation, in particular those quoted above.

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