The World's Most Efficient Cars

By Roland Piquepaille

Like every year, this is the season for the Shell Eco-Marathon annual fuel-economy competition. Last week, the hydrogen-powered Swiss PAC-Car II broke a new record, using 1.02 gram of hydrogen to finish the race. This is the equivalent of 5,385 kilometers per liter of gasoline. For users of other units, this translates to a whopping 15,210 miles per British gallon or 12,670 miles per U.S. gallon. And this week, the British Ech2o car will attempt to break this record. Its designers say that this car, also hydrogen-powered, "can travel on less electricity than it takes to power a light bulb." It will be driven by a 13-year old experienced go-kart driver." Read more...

Let's start with the PAC-Car II, designed at ETH Zürich (Swiss Federal Institute of Technology Zurich). After breaking the world record for fuel efficiency, ETH Zürich published this news release on June 28, 2005.

ETH Zurich set itself a goal to construct a vehicle that used as little fuel as possible and provided the highest possible fuel efficiency. So they gave the so-called PAC-Car a fuel cell that produces electrical energy from hydrogen and drives two electric motors. The only "emission" from PAC-Car is pure water. The car is lightweight, weighing in at only about 30 kilograms.
And, PAC-Car has now achieved its goal: it finished the course at the Shell Eco-Marathon taking place on the Michelin test track at Ladoux, France, using only 1.02 grams of hydrogen. This converts to about 5385 kilometres per litre of petrol, a new world record in economical fuel consumption. This means that PAC-Car would only use eight litres to drive around the globe.

Below is an image of the PAC-Car II in Zürich on May 10, 2005 (Credit: ETH Zürich). And here is a link to a larger version (2.37 MB).

The PAC-Car II in Zürich

And this is a picture of the PAC-Car II during the Shell Eco-marathon in Nogaro on May 21, 2005 (Credit: ETH Zürich) with a link to a larger version (418 KB).

The PAC-Car II during the Shell Eco-marathon in 2005

You'll find tons of other photographs in the different galleries available from this page.

And for more information, please visit this technical section.

The following paragraphs come from the Aerodynamics page.

PAC-Car II is equipped with 3 wheels; the single rear wheel is powered and steered, and the front wheels have a camber angle of -8°.
This solution allows the reduction of the frontal surface area because the room needed to steer the wheels is not needed. Some experiments on a test bench have shown that this camber angle does not provide too much rolling resistance.

[Note: for those of you not familiar with the notion of "camber," here is an explanation provided by the Ford Motor Company in this glossary: "Camber is the relative tilt of the wheels, usually slightly inward at the top edge, as viewed from the front of the vehicle. Camber is set to optimize handling and tire wear Front and rear wheels must also be aligned with respect to each other."]

You'll find also more details about the fuel cell system on the Powertrain and Control page.

The fuel cell, a by-product of the PowerPac project, is of the PEM type (Proton Exchange Membrane) and benefits from an embedded auto humidifying area specially designed by PSI. The stack efficiency is exceptional, close to 70%.

Now, let's move to the British challenger, described by CNN on July 5, 2005, in a short article, "Eco-car more efficient than light bulb."

The Ech2o car is built by the BOC Group, a British gas firm, which issued a news release on July 4, 2005.

The BOC Ech2o has been designed with a simple goal to demonstrate fuel efficiency. But unlike most other eco-marathon vehicles that run on petrol or diesel, the BOC Ech2o's driving force comes from electricity, created in a hydrogen fuel cell.
The car could travel around the world on less than the equivalent of two gallons of petrol, using 25 watts -- a fraction of the power a light bulb uses.
It could also be the most efficient vehicle ever to move on wheels and, as its only emission is water, the car heralds a new age of clean virtually silent road travel, according to experts.

And why did the company choose such a young driver to try to break this fuel efficiency world record?

The BOC Ech2o car, driven by Jack Dex, 13, of Southam College, Warwickshire, will attempt to break the world fuel efficiency record of over 10,000 miles per gallon next week, during the Shell Eco Marathon at Rockingham Raceway in the Midlands.
The youngster was chosen because he is small and light enough to control the vehicle, without weighing it down -- and because of his experience as a junior TKM Kart driver.

Will he break the record? Check the news near the end of the week.

Sources: Various news releases and web sites

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