Next October, a group of dedicated students from Cambridge University will travel to Australia in an attempt to win an arduous 3,000km marathon in a solar car with the equivalent power of a hairdryer.
The team behind the project is the 60-strong Cambridge University Eco Racing Team (CUER), which will be competing in the 2013 World Solar Challenge, the globe’s foremost solar endurance race which lasts for around four days. When E&T caught up with them, they were part way through constructing the vehicle’s carbon fibre monocoque chassis.
“We have quite a mix of individuals and a great team,” says Keno Mario-Ghae, team leader and a second year engineering student at Girton College, who explains CUER is made up of students from a variety of disciplines and is split into a technical half and a business half.
“Every time a challenge has arisen we’ve dealt with it and on the whole the project hasn’t slipped at all. Basically it takes up all of your hobby and going-out time.”
CUER was founded several years ago after the then undergraduate student, Martin McBrien, undertook an exchange year at the Massachusetts Institute of Technology (MIT) in the US and was involved in a solar car project. Since its formation in 2007, CUER has become one of the UK’s leading forces in solar vehicle development and McBrien is still involved with the team as a member of its advisory board.
The World Solar Challenge
For the World Solar Challenge, teams have to design and build a vehicle that will use the power of the sun to maintain an average speed of more than 80km/h in what is described as one of the harshest environments known to man. In 2009, CUER came fourteenth out of 26 in the race and although it returned in 2011, bush fires and bad weather meant only seven of the 37 entrants completed the race on solar power alone.
In June (2012) it believed it was well on the way to developing a winning vehicle for the 2013 event with its recumbent bike-style design when one year into the two-year preparation window the rules were changed dramatically. To make the challenge more relevant to the car manufacturing industry, the organisers said vehicles had to be four-wheeled and each wheel had to be at the corner of a rectangle.
Rising to the challenge
CUER, whose team members range from first years to PhD students and which includes several female engineers, quickly rose to the new challenge though.
“We took what we’d learned about aerodynamics from the two-wheel design,” says Mario-Ghae, adding: “There are two ways you can make a vehicle go faster: you can have a bigger engine or a more efficient car. The traditional approach is to go for a bigger engine and therefore a large table-top-looking solar car but we decided to go for the most efficient shape and maximise the solar performance of that shape.”
The result is the affectionately named Daphne, a highly aerodynamic teardrop shaped car based on a new concept for solar vehicles and weighing in at only 120kg. The team predicts it will be the lightest car to enter the World Solar Challenge.
“This means we can design innovative, energy-saving features that wouldn’t be practical in a heavier car,” says Mario-Ghae, who claims the car will be able to hit speeds in excess of 82km/h.
While the team doesn’t want to give too many secrets away, one of its potentially winning features is the innovative way CUER is embedding the solar panels within an aft-facing sun tracking plate that follows the trajectory of the sun and which can create a 20 per cent gain in power.
The race will cross 22 degrees of latitude so the team has created a modelling programme that will adjust the solar cells to maintain the optimum position at all times. Meanwhile, an in-built carbon-based suspension system reduces energy wastage and, because the motor is located in the hub of the wheel, there is no need for gears, chains or differentials that can account for losses in efficiency.
Mario-Ghae explains that the reason the design works so well and why it will be able to compete with much bigger teams in the event is through a decoupling of the aerodynamic and solar performance.
“They become independent so we can improve the aerodynamics without having an adverse effect on solar performance,” he says, adding that the biggest challenges for the team tend not to be technical ones. “The real challenge is convincing people your ideas are worth supporting.”
Raising funds and meeting deadlines
The project has received grateful support from organisations such as Jaguar Land Rover, ARM, Cambridge Precision and Schlumberger but it still welcomes help from others and continues to raise funds to complete Daphne’s build.
CUER’s next self-imposed deadline is June/July when it hopes to have Daphne ready for testing before working towards the climactic main event in October.
“We’ll get out there in advance of the race to get lots of mileage in,” says Mario-Ghae. “So then we won’t just understand how the technology works in these conditions but also ensure we understand how we can race well. And if everything goes well, we’ll do the race in three and a half days.”