Since 1985, the Shell Eco Marathon has pitched teams of students against each other in an attempt to see who can travel the furthest using the energy from one liter of fuel (or its equivalent). Teams compete by running at 15 mph (24 km/h) over 6.3 miles (10 km), and the cars that use the least fuel, electricity or alternative propulsion method are crowned winners in their class.

It's a simple premise which belies a complex mix of design and engineering challenges. From left-field materials to low-slung, bullet designs, here's a look at some of the more interesting competitors from Eco Marathon events around the world.

Toulouse Ingénerie Multidisciplinarie

Toulouse Multidisciplinary Engineering school has ignored more traditional lightweight materials like carbon fiber and aluminum, instead using resin-coated silk to create its bullet-style body.

The major drawback to using the layered-silk method is how fiddly it is. Just a single particle of dust can disrupt the weave of the silk fabric, but on the other hand, its use results is a body that weighs just 13 kg (28.7 lb).

Thanks to this super-light body, the TIM 07 weighs just 67 kg (147.7 lb) in total.

Nanyang Technological University

The NTU Venture 8 is Singapore's first 3D-printed concept car, and has a solar power system working in tandem with batteries to power its electric motor.

Built around a carbon fiber shell, the NV8's body is made up of 150 individual panels that took three months to print and assemble. The silicon solar cells on the roof are sliced into strips with a high-speed saw, then wired up to form a module.

Although that might sound like a complex procedure, it was the best way for the team to get the cells to conform to the car's shape, and evidence of how hard teams are working to make these clever engineering solutions work on their fuel-saving creations.

Laval University

Laval University's Alerion Supermileage showed its worth at this year's Eco Marathon event in Detroit, where it managed to achieve the equivalent of 1,099 km (682.9 mi) per liter of fuel on a track.

This remarkable economy comes from a combination of low weight and an incredible drag coefficient of just 0.072. Tipping the scales at just 96 kg (211.64 lb), the car's carbon fiber monocoque is shifted by a 1.95 hp (1.45 kW) Briggs & Stratton motor attached to the single rear wheel.

La Joliviere

La Joliviere's entry makes Laval University's 1,099 km/liter car look a bit thirsty, having achieved a crazy 2551.8 km/liter (1585.6 mi) in last year's Rotterdam Eco Marathon.

Rather than competing with gasoline powered cars the Microjoule gets its power from compressed natural gas, but a petrol-powered version of the car holds the all-time record at a scarcely believable 3,771 km/liter (2,343.2 mi).

Aston University

Look away now if you're not comfortable with Ikea furniture, because Aston University's creation, which competed in 2012, is a flat-pack car. Made of a combination of sustainable wood and cardboard, even the tires are made of an eco-friendly bio-resin infused with hessian fibers.

The car (if you can call it that) is hydrogen powered, and can be flat-packed after use for easy shipping and storage. All up, it weighs 170 kg (374.8 lb), and can eke out the equivalent of 50 mpg (4.7 l/100 km).

The next running of the Shell Eco Marathon will take place in London, starting on June 30.

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