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Cambridge University's sun-tracking solar car targets World Solar Challenge crown

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July 9, 2013

Resolution is a departure from the “tabletop” look of most other solar cars

Resolution is a departure from the “tabletop” look of most other solar cars

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A group of engineering students from the University of Cambridge is hoping to become the first British team to take home the World Solar Challenge crown with a new solar car dubbed "Resolution." The vehicle, which the team claims "rewrites the rulebook for green vehicles," features solar panels that will move to track the sun as it makes the 3,000 km (1,864 mi) journey across the Australian outback from Darwin to Adelaide.

Resolution's unique design was unveiled on July 5 at the Millbrook Race Track, near Bedford, England. Like the mirrors at concentrated solar power (CSP) plants, it features moving panels that track the path of the sun across the sky, allowing the vehicle to maximize power collection throughout a race.

The solar panels are embedded within an aft-facing tracking plate that follows the sun's trajectory, moving the panels so they are optimally positioning to catch some rays. The Eco-Racing team estimates this will give the car 20 percent more power than it would have with traditional paneling.

Traditionally, solar cars have been impeded by an issue of balance between aerodynamics and solar performance. Like most engineering, a compromise was made where the highest efficiency peaked.

"That's how [solar cars have] been designed for the past 10 years, and that's why they all tend to look the same," explains Keno Mario-Ghae, team manager for Cambridge University Eco-Racing.

Unlike the tabletop design that most previous entries in the Word Solar Challenge have adopted, Resolution has a teardrop shape that houses the tracking plate structure under a canopy. This vehicle design is more aerodynamic, with no compromise between aerodynamics and solar performance because the shape houses the solar panel system, rather than the system being a part of the vehicle structure.

Last year, the World Solar Challenge altered its rules with a stipulation that required cars to adopt a more conventional design than previous years. Though the Resolution doesn't quite have the appearance of an SUV, the design is certainly closer to common road cars than past entries.

The tiny cockpit features on-board telemetry, which gauges traffic, weather, and driving style to create an "intelligent cruise control" that will advise the team on the best practices to optimize efficiency during the race. Locating the motor in the hub of the wheel also allowed the team to eliminate the need for gears, chains and differentials.

With a footprint of less than 5 m (16.4 ft) in length, 0.8 m (2.6 ft) wide, and 1.1 m (3.6 ft) high, the Resolution's driver can't be any taller than 1.6 m (5 ft 3 in). The team says that these dimensions are deliberate concessions for the sake of making the vehicle as fast and efficient as possible (they are trying to win the race, after all). It seems to be working, as the 120 kg (264 lb) vehicle can reach a top speed of nearly 140 km/h (87 mph) while running on about the same amount of power as a hair dryer.

Whether the Resolution can deliver the Cambridge University Eco-Racing crown will be revealed at the 2013 World Solar Challenge in Australia that runs from October 6 to 13.

The video below gives a brief overview of Resolution's journey from conception to completion.

Source: University of Cambridge

9 Comments

They won't win. To many compromises in the design. The teardrop shape is reducing the solar tracking efficiency at the rear panels. The cockpit is shadowing the front panels if the sun is in front. The transparent canopy adds a supplemental reflection surface reducing the PV panels power. The double wheel rear axis is also reducing the tracking efficiency of a set of panels, a single wheel axle would have alleviated a little the problem.

ClauS
9th July, 2013 @ 02:29 am PDT

It will flip over. I have a Sinner Mango velomobile that is 76 cm wide and has a much lower centre of gravity. In fast corners around 40 km/h it has the tendency to lift a wheel, so I always have to break before I turn. It needs a much wider distance between left and right wheels.

Cas Tuyn
9th July, 2013 @ 07:21 am PDT

Note to clau_sav.

Darwin to Adeliade is going south. Being in the southern hemisphere, the suns shines from the north, and so the cockpit will not shadow the cells.

I wish them well. It is nice to see someone trying to build a better mousetrap, rather than a better coffee table.

Bruce H. Anderson
9th July, 2013 @ 10:00 am PDT

This adds a lot of complexity and thus weight. While they were at it I hope the added a gyro stabilizer.

Eventually somebody is going to add a thermal capture system and kick tail.

Slowburn
9th July, 2013 @ 04:18 pm PDT

clau_sav:

The compromises were forced on them by rule changes. The reflective canopy has an offsetting aerodynamic benefit. I've read 4 wheels are more efficient than 3.

The motor in wheel is most efficient. I want to see the competition first but I like everything I see, and would bet they might win.

Don Duncan
9th July, 2013 @ 04:22 pm PDT

The shell appears to be completely sealed with little or no air flowing through. I just wonder have the team taken into account the temperatures they are likely to encounter during the event, and whether the transparent shell will act as a greenhouse, heating the PV panels? As panels heat up, their efficiency drops, so it may be necessary to have a scoop at the front to allow air to move over the panels (and rider?) and cool them.

joeblake
9th July, 2013 @ 05:57 pm PDT

A preview of one of this year's solar race competitors. 140 km/hr on a hair-dryer's power!

Ricky Hall
9th July, 2013 @ 07:09 pm PDT

To address some of the comments on this article, all designs require compromise. Our design focuses on decoupling the aerodynamics of the vehicle from the solar performance. Whilst some light is reflected by the canopy, the design of this has been optimised to transmit the maximum amount of light, without disrupting the airflow over the vehicle.

As for the other points, the regulations for the 2013 WSC require 4 wheels, and therefore all the entrants are in the same position on this front.

We have considered the thermal issues caused by the enclosed cells. The airflow through the car is carefully managed to control the cell temperatures, and we are using a type of solar cell that is not badly affected by heat.

The stability of the vehicle has been tested already, and we have found it to be more than adequate for the challenges we will face in Australia.

We have an ask an engineer section on our website (http://www.cuer.co.uk/ask-an-engineer/) where you can find answers to any questions you may have about our design.

Sean True
10th July, 2013 @ 03:46 pm PDT

I assume the gains from having the panels incident to the sun out weigh the cost of driving the motors and having overall less area to put solar cells on the exterior? Depending on how many turns are in the track, the motors may have to move more often.

I know from personal experience you lose around ~30% at a ~45° incidence angle.

dink
18th July, 2013 @ 12:44 pm PDT
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