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Thursday, July 20, 2006

This High-Performance EV Will Smoke You! - Here Comes the Tesla Roadster

Ask Detroit about batteries for electric vehicles and they'll probably tell you they're just not ready yet. But hey, what the heck does Detroit know about batteries, anyway?!

That's what Silicon Valley electrical engineer Martin Eberhard asked himself when he found out he couldn't buy a sports car that delivered both good mileage and snappy performance. It seems that fuel economy and high performance are mutually exclusive, at least for in the internal combustion engine world. After a little research on alternatives, Eberhard found out that electric vehicles can deliver both efficiency and performance.

The only problem: nobody's making them.

What's a boy to do? Well, if you're an electrical engineer with experience eaking every last drop of power out of lithium-ion batteries to maximize runtime on electrical gadgets - and you've got the backing of backing of some of Silicon Valley's big names - you simply go ahead and found Silicon Valley's first real auto company - Tesla Motors - and design your own high-performance EV: the Tesla Roadster.

Eberhard's central concept in founding Tesla Motors, back in July 2003, is that there is no need to reinvent the battery, particularly for a product with a small initial market. Eberhard simply adopted the lithium-ion technology used in laptops and harnessed the momentum of the computer industry. Let Dell, HP, and the rest of the sprawling PC business, with their billions of R&D dollars, do the hard work of extending battery life and driving down prices. He'd piggyback on their innovations.

Meanwhile, automakers had been doing their own R&D, dismantling some of the biggest barriers to entering the business. To lower production costs, the Big Three had outsourced much of their parts manufacturing over the past 25 years. An upstart like Tesla Motors can now buy just about everything it needs to mass-produce a car from independent suppliers. A fledgling electric car company had other advantages, too: Tighter emissions standards have raised the cost of developing gas-powered cars, and buyers of low-emission vehicles are lured by big tax breaks.

So, after pounding the pavement and securing some venture capital from several tech industry notables - PayPal cofounder Elon Musk, Google's Larry Page and Sergey Brin, and ex-eBay chief Jeff Skoll all chipped in to fund Tesla Motors - Eberhard went to work securing contracts for parts and manufacturing with established businesses - including British sports car manufacturer, Lotus.

Since most of the folks filling cubicles in Tesla Motors' new offices in San Carolos, California, were dotcom - not Detroit - veterans, Eberhard ensured he'd cover everything he didn't know about car manufacturing - which was just about everything - by hiring engineers and executives away from Lotus. (Eventually, he lured so many Lotus employees that the British company insisted he sign a no-poaching agreement or it wouldn't build the car!)

For the past three years, Tesla Motors ran in stealth mode. Because electric cars had failed so visibly in the late '90s, the company knew it faced a tough marketing challenge, and Eberhard didn't want to show the world something half-baked. If Tesla was to succeed, it would need to present a fully realized, radically different approach. Luckily, there was little threat of car spies ruining the surprise. "Silicon Valley is a great place to run a secret car company," Eberhard says. "Nobody expected something to sprout up in Northern California, so no one came looking."

The result of all those years of stealthy work: the Tesla Roadster, a lithium-ion battery powered sportscar featuring a 248 hp (185 kW) electric motor that takes the light-weight roadster from 0 to 60 in under four seconds. The Roadster has a top speed of 130 mph and - thanks largely to it's lightweight and aerodynamic design - has a range of 250 miles off it's array of 6,831 off-the-shelf lithium-ion cells. When connected to a special 220-volt, 70-amp outlet, recharging takes about three and a half hours.

The Roadster's 3-phase, four-pole motor uses a low resistance “squirrel cage” with large copper end rings. This design allows the rotor to develop high current flows and torque, with low resistance losses. The use of a small air gap allows tight inductive coupling which, combined with low loss magnetic materials, enables the development of high torque at high rpm. Together, these factors allow the induction of large currents, even at high rpm, producing much flatter power and efficiency curves from approximately 2,000 rpm to 12,000 rpm. The motor redlines at 13,500 rpm allowing the car to run at 70 mph in first gear! The car has only two gears, plus reverse.

Tesla Motors will be selling the car for $80,000-100,000 - in the range of a Porsche 911 Carrera S.

Of course, an expensive two-seater isn't going to have much effect on an industry that sells 17 million automobiles in the US each year. As Wired Magazine points out, "Sure, every VC will have to get one, and George Clooney will probably be seen piloting one down Sunset Boulevard. But selling a few thousand cars won't help Eberhard build a dominant 21st-century car company."

That's why Eberhard is already preparing a four-seater sedan, codenamed White Star, which could hit streets as early as 2008. Of course, the sedan won't be as lightweight or aerodynamic as the Roadster, so we might expect it's range to drop significantly. Eberhard's response: maybe with today's tech. But battery power is improving steadily, he points out, and several companies say they may soon double battery life. By the time the sedan comes out, he says, batteries will be ready to deliver: "We're going to ride that technology curve all the way home."

In a white paper (The 21st Century Electric Car) published on the Tesla Motors website, the company calculates explores the 'well-to-wheel' and 'tank-to-wheel' efficiencies of their Roadster compared to competitors - both for in the fuel economy and high performance worlds.

According to the White Paper, the tank-to-wheel - or vehicle fueling and operation - energy efficiency of the Roadster is 2.18 km/MJ, or the equivalent of 135 mpg.

Assuming electricity supplied from a combined-cycle natural-gas-fired generator, and accounting for transmissions losses over the grid leads them to calculate the “well-to-wheel” - or full fuel cycle - efficiency of the Roadster to be 1.14 km/MJ - double the efficiency of the Toyota Prius!

Tesla then tackles the question of hydrogen fuel-cell vehicles (FCV), deriving a theoretical efficiency for an FCV fueled with hydrogen produced by steam methane reforming of 0.85 km/MJ - better than gasoline cars, but 32% worse than Tesla's Roadster.

And as Tesla points out, real fuel-cell cars do not perform nearly this well:

...The best fuel-cell demonstration car measured by the EPA is the Honda FCX, which gets about 49 miles per kilogram of hydrogen, equal to 80.5 kilometers per kilogram. We know that the energy content of hydrogen is 141.9 MJ/kg, so we can calculate the vehicle efficiency to be 80.5 km/kg / 141.9 MJ/kg = 0.57 km/MJ.

...When we calculate the well-to-wheel energy efficiency of this Honda experimental car, we get 0.57 km/MJ x 61% = 0.35 km/MJ, not even as good as the ordinary diesel Volkswagen Jetta, let alone the gasoline-powered Honda Civic VX or the Honda Insight hybrid car.

However, some proponents of hydrogen fuel cells argue that it would be better to produce hydrogen through electrolysis of water. The well-to-tank efficiency of hydrogen made through electrolysis is only about 22%, and the well-to-wheel energy efficiency of our theoretical fuel-cell car would be 2.78 km/MJ x 50% x 22% = 0.30 km/MJ, and the well-to-wheel energy efficiency of the Honda FCX would be 0.57 km/MJ x 22% = 0.12 km/MJ, even less efficient than a Porsche Turbo.


  • Tesla Motors website - lot's of pictures of the Roadster and more info here.

  • Tesla Motors White Paper: The 21st Century Electric Car

  • Wired article: Battery-Fueled Car Will Smoke You - July 19th, 2006. - there's more pictures here too.

  • Green Car Congress article: Tesla Reveals High-Profile Electric Roadster; Calculates EV is More than 3x as Efficient (WTW) as Fuel Cell Vehicle

  • Well, this oughta give us all something to drool over, anyway. And it will hopefully go a good way towards dispelling any myths about sacrificing performance for efficiency...

    [A hat tip to EV World]


    Anonymous said...

    Although I am enthusiastic about this pure EV, I think the range will severely limit the interest. Because constant speed/load diesel generators are so much more efficient than variable speed/load auto engines, how would a pure hybrid stack up? The on board engine/generator would be used only for recharging batteries and therefore (theretically) would be much more fuel efficient and cleaner then a variable speed/load engine...

    Jesse Jenkins said...

    I don't know, Mike. With a range of 250 miles, I don't think folks will be too hesitant to buy this guy. I mean, consider the kinds of folks buying a $100k pure electric roadster anyway. Their not the type who are concerned much about practility, and certainly already have another car (or two or three).

    As for the hybrid, I'd like to see one of them too.

    I keep hearing that single speed diesel gen-sets are far more efficient than variable speed engines, and we all know that electric drives are more efficient than a standard transmission... but if that's the case, then why aren't all of our cars using electric motors powered by diesel or gasoline gen-sets? Seems like there's got to be something we're missing here, or every car on the road would have an electric drive and a ICE generator.

    Anyone have any insight here? I'd love to figure this one out.

    Unknown said...

    Big boring companies are run by big boring people.

    American car companies are enormous institutions designed to eliminate risk and any ideas that haven't already been done before.

    Andy's 1st maxim of organizational analysis: Just because it would make sense to do something a certain way is not enough reason to presume it actually IS being done that way.