How low battery can you go? | University of Oxford
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How low battery can you go?

Pete Wilton

With batteries still struggling to pack the same power as petrol one of the great challenges for electric vehicles is extending their range.

A team led by researchers at Oxford University's Department of Engineering Science and The Oxford Martin School has been pushing the boundaries of what such machines can do with their prototype electric vehicle PEGGIE.

The PEGGIE crew had a successful debut at last year's Shell Eco-marathon Europe competition, a showcase for ultra energy-efficient vehicles built by student teams, and entered this year's event in Rotterdam on 19 May.

The Oxford team won the Technical Innovation Award ahead of nearly 200 other teams from across Europe for a series of innovations:

This year the car sported a photovoltaic array of 130 individual cells which continually reconfigure themselves for maximum efficiency, improving efficiency by over 5%: the team compare it to getting rid of your car's gearbox and instead having an engine that continually rebuilds itself so that its performance is optimised for the vehicle's speed and torque requirements at all times.

Not only does PEGGIE's design enable regenerative braking – recovering energy during braking – and free-wheeling but it also features a 'smart' clutch that electronically synchronises the speed and position of the clutch teeth and controls how they engage. Because this design minimises the forces at work inside the clutch the entire drivetrain can be built from smaller and lighter teeth, gears, and actuators.

To help the driver adopt the most efficient driving style possible she gets a handy Android app to refer to on a mobile handset attached to the controls. The app delivers a colourful map plotting torque along one axis and speed along another – rather like playing a computer game the aim is to drive keeping the crosshairs in the map's 'green zone' which indicates the most efficient style.

The Oxford team also improved PEGGIE's range by over 50% on last year, delivering a performance of 564 km/kWh (the equivalent of Oxford to Minsk on a pint of petrol) coming seventh in the solar electric class, an improvement on last year's twelfth place.

'The Shell Eco-Marathon was a fantastic, if at times traumatic, experience,' said Pete Armstrong, Team Technical Manager. 'It was an honour to be awarded the technical innovation prize, we were very impressed by other vehicles who had developed a range of exciting ideas and techniques in areas such as real-time throttle control and 3D printed components that could be swapped out quickly.

'We owe our result this year to the inspiration drawn from other teams when we debuted last year. Although there is a very competitive atmosphere, the overriding experience is one where hundreds of teams help each other out in the face of all the inevitable challenges that arise, exchange ideas and try to have fun in the process.'

If you are interested in getting involved in the PEGGIE team email robert.camilleri@eng.ox.ac.uk For sponsorship opportunities email nicole.miranda@eng.ox.ac.uk