Diatribes of Jay

This is a blog of essays on public policy. It shuns ideology and applies facts, logic and math to economic, social and political problems. It has a subject-matter index, a list of recent posts, and permalinks at the ends of posts. Comments are moderated and may take time to appear. Note: Profile updated 4/7/12

23 February 2015

Variable-Range and Variable-Performance Cars

[For the Apple angle on this post, click here.]

Why is the average car capable of driving between 250 and 450 miles without refueling? The average driver’s daily mileage is nowhere near that high.

Before Chevy approved its electric Volt for production, GM did a lot of market research. It found that the Volt’s rated electric-only range, about 40 miles, was enough for the daily commutes of a majority of American drivers.

Add a few miles for shopping and taking the kids to piano and swimming lessons, and most drivers might need a daily range of some 60 miles at most. For my own odd location—between Santa Fe and Albuquerque but closer to Santa Fe—I might need to be in a “sweep spot” in range, about 100 miles. That’s it.

So why do virtually all consumers buy and drive cars with from four to nine times the range they need?

There are two easy answers. First, in gasoline cars increasing range requires only a bigger gas tank, which adds negligibly to the capital cost of the car.

Second, people like having the security of extra range. They never know when they might take a long car trip. And a bigger range lets drivers go farther and longer before filling up.

So we have myriads of drivers running around day to day in cars, SUVs and light trucks with ranges that they need or use only a few times a year, if ever.

The engineering and efficiency of this practice make no sense. Carrying around unneeded gasoline as a routine matter increases the car’s weight and mass (inertia). It makes the car more sluggish, i.e., slower to accelerate. And it decreases gas mileage.

Does the extra gas give the car any better performance? No. Gasoline is gasoline. So any engineer with an eye to efficiency, let alone perfectionism, should tear his or her hair out at the very thought of big gas tanks and excessive range.

Drivers could get a little better performance and gas mileage simply by keeping their gas tanks only partly full—just enough for their daily needs, plus a 20% safety margin. For most drivers, that would mean keeping their tanks about one-quarter full.

So why don’t they? Well, fueling every day would be inconvenient and time-wasting. And because the energy-density of gasoline is high, they wouldn’t save that much in fuel cost anyway. What busy worker or home-maker wants to spend precious time and mental energy worrying, every day, about how full the gas tank is?

Enter electric cars. They are a whole new animal. They alter, dramatically, every one of the factors that got us to this inefficient place with gasoline-driven cars. Let’s analyze.

First, look at price. Bigger gas tanks add negligibly to the price of a gasoline car. Not so electric-cars’ batteries. In electric cars, the batteries are the single most expensive system, both to supply and to maintain. They are also the heaviest and most massive single system, by far.

What’s the difference between a Tesla Model S and a Nissan Leaf? Mostly range and performance. The minimum range of a Model S is about 265 miles, as compared to the Leaf’s 73. So the Tesla’s batteries have to have 265/73 = 3.63 times the capacity of the Leaf’s. If we assume that Nissan and its battery suppliers have roughly the same technology as Tesla, that means the Tesla’s batteries mass and cost over 3.5 times as much as the Leaf’s.

Let’s suppose the Leaf’s batteries cost $10,000. Then the Model S’ batteries would cost roughly 3.5 times as much, or $35,000—half the car’s sticker price. If Tesla dropped the mileage to 73 miles and used only the Leaf’s $10,000 batteries, you could have all the Model S’ elegance and high technology for $10,000 (the reduced price of the smaller batteries), plus $35,000 (the price of the rest of the car), for a total of $45,000. That’s still in luxury-car territory, but at least not in extreme luxury-car territory. (All these prices are before any federal or state subsidies for electric cars.)

Note that the battery-price difference, $35,000 - $10,000 = $25,000, is way more than the price of a larger gas tank.

Once you have a bigger battery, it doesn’t matter whether you fill it up all the way or only partly. Electrons don’t mass or weigh much. So you would save little or nothing, in performance or efficiency, by not “filling up.”

As for convenience, electric cars beat gasoline cars hands down. Consumers like long-range gasoline cars because they don’t like having to go to gas stations frequently, especially at night or in freezing weather. But suppose you could “gas up” in your own garage, every time you come home, as electric cars let you do. Then all you’d need is a spouse (or mother or father) kind enough to remind you gently, “Dear, did you plug the car in and close the garage door?”

What about the battery’s mass or weight? Remember Newton’s second law of motion, F = ma? The acceleration a of anything, including a car, under a force F is inversely proportional to its mass, m.

So as the mass of the battery increases, the acceleration for a given force decreases, and with it the car’s performance. Big batteries slow cars down. But if the battery’s peak current (which generates the force) is proportional to its mass, the rise in battery mass produces an increase in peak current and therefore performance, due to a bigger F.

These two effects don’t precisely cancel each other. The inertia-caused decrease in performance with increasing battery mass is inversely proportional to the mass of the whole car, which is bigger than the mass of the battery. But the change in peak current—and therefore the increase in force (and performance) that it causes—is directly proportional to the increase in battery mass alone. That increase is larger than the corresponding decrease in performance from the car’s increase in total mass because the mass of the battery alone is smaller.

So, perhaps non-intuitively, an electric car gains performance with increasing battery size, despite the increase in total mass and inertia and therefore a decrease in energy efficiency. This is the main reason why the Tesla Model S can go from zero to sixty miles per hour in 4.2 seconds, while the Leaf (or Volt) can’t.

If Tesla produced a 73-mile-range car, it could sell it for around $45,000. It might have better performance than the Leaf, but it would hardly match the Model S’ performance.

Something very like this is probably how Tesla plans to offer its low-priced “people’s sedan” some time in 2017. But the same strategy is much more versatile. Tesla could offer a range of cars having the Model S’ elegance and high technology, but with a wide range of mileages, performances and price tags, all using the same basic mechanical platform.

This analysis leads to a much more important conclusion. The nature of electric cars and the laws of physics suggest that there’s no need for permanently long-range electric cars, or for permanently high-performance ones, except for showoff drivers.

Remember Tesla’s online battery-swap video of a couple of years ago? There was Elon Musk, watching a Model S drive out on a specially-prepared stage. When the car reached stage center, a trap-door mechanism below the stage started popping the battery pack’s screws, lowering the presumably spent battery pack, and replacing it with a fully charged one.

As this was going on, a TV screen behind Musk and the Tesla showed a driver pulling up to a gas pump to fill up. The Tesla drove off the stage with a fully-charged replacement battery in 93 seconds, before the gas guzzler could fill up.

If you can replace a big, mostly-discharged battery with a fully-charged big one in 93 seconds, you can certainly replace the big one with a small one—or vice versa—in the same amount of time. All you need is batteries with enclosures and plugs of standardized size and shape. (Their mass or weight, and internal size, would of course vary with their range/performance.)

Want a cheap electric car? Buy the low-range one and charge it in your garage.

Want to go on a long electric trip? Drop by your neighborhood Tesla dealer or authorized service station and replace your small battery, temporarily, with a higher-capacity rented one, just for that trip.

Want to impress a pretty girl with head-snapping acceleration? Do the same. Then, after you’ve got her, switch back to a more moderate, lower-range, lower-performance and cheaper battery.

You pay for only the battery you use and for the time you use it. At other time, you’re not driving around with extra mass, wasting energy. And you can convert your car for the long trip, or into an impressive performance machine, in 93 seconds. A lot easier than swapping a gasoline engine, no?

Do you begin to see how important Tesla’s Nevada “Gigafactory” for batteries will be? It can make different sizes of batteries for different models/ranges of the same car. It can make batteries for quick battery swaps: no long waits required. It can let a single car platform have a range of mileages and performances. But Tesla’s batteries will go far beyond cars. The Gigagfactory can make batteries for smoothing the intermittency of solar and wind power, whether for individual off-grid homes or for utilities. It can make batteries for remote off-grid electronic and electrical installations, including cell-phone towers, microwave repeaters, radar stations and emergency warning systems.

How many months before the Gigafactory is running at full capacity? My guess is between nine and twenty-four. Remember, at 3 miles per kilowatt hour (the Leaf’s and Volt’s rated mileage), driving an electric car costs just 60% (at the nationwide average residential electrical rate for 2013) of what it costs to drive a 30 MPG car on gasoline, even at $2.10 a gallon. This saving comes regardless of any subsidies for electric cars; and it’s much smaller than your per-mile saving when you charge your car from your own solar array.

The iCar?

For over a week, Bloomberg.com has been posting “exclusive” stories about Apple’s plans to get into the car business. One recent story had a provocative headline: “Apple Wants to Start Producing Cars as Soon as 2020.”

Bloomberg.com proffers three kinds of evidence for these plans. The first is alleged “leaks” by secretive, anonymous sources. The second is accusations (and an upcoming lawsuit) over Apple allegedly “stealing” employees away from Tesla and from Waltham-Mass.-based battery maker A123 Systems LLC. The third bit of evidence is Apple’s huge cash hoard of $178 billion, which is currently increasing at about 10% per year, and pressure from shareholders to do something with it or give it to them.

As most Apple fans and shareholders know, Apple is as secretive about its new-product plans as any American public company. It’s almost as relentless in pursuing leaks and leakers as the President was in pursuing Edward Snowden. So it’s entirely possible, although not a sure thing, that these rare leaks are, to use a double negative, “not unauthorized.”

Why would Apple want to spill the beans? I can think of only two reasons: disinformation and planting a marker.

Apple may actually not be going into cars at all, but into high-tech, high-power batteries to make renewable energy non-intermittent and more usable. Such a foray would be entirely consistent with Apple’s recent investment of $850 million in solar energy.

Alternatively, Apple may be trying to scare away other new entrants from the electric-car business, or give them an incentive to sell out when the time is right. For reasons described in an old post, Apple is probably not at all scared of anyone from Detroit. The few good people there it can hire away, and the rest would only slow things down.

Long before its threatened bankruptcy and bailout, GM ignited the current-electric car craze by announcing the Volt. That was eight years ago. I gave GM kudos for that bit of innovation—the first real innovation in autos to come out of Detroit since Chrysler’s “hemi” cylinder head in the 1960s. Detroit had done a lot of prototyping and market testing, but it had missed small, fuel efficient cars, the Wankel engine and hyrbids.

In the end, all you really need to know about “innovation” in Detroit is that GM felt it could not make or sell the Volt without a gasoline engine. So no, if Apple is not spreading disinformation, any deliberate or tolerated leak is hardly aimed at keeping Detroit out of the market.

It could be aimed at Tesla—an attempt to dry up new investment. Or it could be aimed at keeping the nascent electric-car market a virtually duopoly, with savvy foreign suppliers like Nissan-Renault nibbling around the edges.

Assuming that Apple is aiming at cars, and not batteries, what are its prospects? Tesla already has proved that you don’t need many traditional mechanical engineers, let alone those from Detroit, to make a first-class car.

As it turned out, doing that was a lot easier than Detroiters taunted and than sleepy auto-industry analysts expected. The main reason is Detroit’s dirty little secret: it no longer makes much of the cars it sells itself. It designs the bodies and styles, does gross mechanical engineering on the chassis, suspension, and assembly, and then orders many of the most critical parts from suppliers. Things like bearings, brakes, hydraulic parts, and key parts of engines all come from firms other than car makers.

But that’s not all. As I’ve noted earlier, an electric car is a whole new animal. It doesn’t have, among other things: (1) any internal-combustion engine, (2) an ignition system, (3) an exhaust system, (4) an engine-cooling system (because electric motors don’t waste energy as heat), (5) a transmission (because electric motors provide constant torque throughout a wide range of RPM), (6) an afterburner or exhaust-purifying system (because electric cars produce no exhaust), or (7) a gas tank or fuel-injection system.

In other words, most of the complex Rube-Goldberg systems that the mechanical and combustion engineers in Detroit design or buy from suppliers won’t be in any cars that Apple makes. On the other hand, Apple’s cars will have several things that Detroit has rarely or never designed or made, including: (1) electric motors, (2) high-power, solid-state current controllers, (3) regenerative breaking systems (which recharge the battery smoothly when the car slows down or brakes), and (4) all the whiz-bang driver-oriented consumers electronics for which Apple is famous and for which Detroit has gotten uniformly abysmal reviews.

So if Apple is truly aiming at cars and not at batteries, its planting a marker makes perfect sense. It may be telling investors and foreign car makers, “don’t mess with us unless you’ve got $178 billion (and counting) to spend and have a track record of superb consumer-oriented innovation.” It may be telling talented engineers in Detroit to start thinking about relocating to a region with cities that work, far better weather, higher salaries, and opportunities that will knock their socks off. And it may be telling Tesla and Elon Musk to look to their laurels.

As I noted in an earlier post, even Musk can fail to grasp fully how much a new animal electric cars can be. The post just above explains one two possible reasons: variable range and variable performance. An earlier post explains some lesser, but still interesting, potential innovations.

Now that Detroit has survived, barely, let the real innovation and competition in personal transport begin!



Post a Comment

Links to this post:

Create a Link

<< Home