How VIRO helps Solar Team Twente towards victory

The World Solar Challenge is a competition for solar cars. The 3000-kilometre race goes right through Australia; from Darwin to Adelaide. This battle between student-built sustainable solar cars stimulates innovation in the field of sustainable transport and energy and thus contributes to a better world of tomorrow. Because the organisation of the World Solar Challenge changes the rules every year, fields of innovation are redirected at every edition.

VIRO has developed a “tool” with which Solar Team Twente can accurately measure how the car’s solar panel performs at different angles towards the sun. The top of the solar car, containing the solar panels, can be hung in the testing frame after which it can be set at different angles using an actuator. The panel’s performance can then be measured at that particular angle. A logging device is attached to the frame and saves all measurements.

The frame can be used to determine the most efficient angle at which the panel needs to be positioned towards the sun during the nine charging stops. The necessary measurements are made in Darwin because the conditions there best match the racing conditions. By doing these tests before the race, the driver of the car only needs to position the panel at the predefined angle at each stop. How it will all go in practice cannot be predicted with certainty, since many factors affect the situation, including the weather.

We talked with Marijn, member of Solar Team Twente, and Gertjan, project manager at VIRO to find out more about their collaboration. Marijn is responsible for the strategy of Solar Team Twente. It is his job to predict the behaviour of the car most accurately, so that he and his team can make the best design decisions. According to Marijn and Gertjan, time constraints were the biggest challenge during the project. “The used technology is not that complicated,” says Gertjan. Gertjan emphasises that he particularly likes to be able to help Solar Team Twente.

According to Marijn en Gertjan, the new testing frame will make a significant difference. The team had a frame before, but it could be improved significantly. Also, the solar cells used in this year’s solar car are much smaller, resulting in a smaller solar panel deck. A different frame was needed. Marijn noticed the need and potential and thought it would be a great project to which VIRO can significantly contribute. The two could not quantify the difference the frame will make in the end, but every minute and millimetre counts in the race.

For Solar Team Twente, this is their first automated frame that works. The automated frame they had a few years ago broke while testing. Ever since the panel had to be held by a member during testing. To prevent this from happening again, Solar Team Twente and VIRO have now provided a back-up plan. Gertjan shows us some rods with rotary knobs, with which the angle can be adjusted manually in the unlikely event that the actuator does not work in Australia. The team expects to be able to make a good estimation of the car’s behaviour during the race with the new frame, because of the improved accuracy compared to manual adjustment and the automatic measurement logging.

Every square centimetre on the RED E is used. In previous editions, there was an empty space between the rounded corners of the solar panels. This year, Solar Team Twente has chosen to overlap the panels, resulting in no more empty spaces. Due to the choice for a new type of cells, the car is a lot smaller than previous editions. According to Marijn, it is difficult to balance between maximising aerodynamics and making optimum use of the space to install solar panels. A more aerodynamic design is one that has as little air resistance as possible and is, therefore, smaller and more curved. However, solar panels cannot bend much and space is needed to place as many panels as possible. Solar Team Twente has developed a model to balance these factors and make a good decision. It was ultimately decided to install a new type of small but efficient solar cells, making the car smaller and therefore more aerodynamic.

The data measured during the race will make an important contribution to subsequent editions of the World Solar Challenge. Solar Team Twente expects the VIRO testing frame to help make better choices during the next edition. The results that are ultimately measured in practice during the race can be compared to what the team’s model predicted. With these results, the model can be refined so that better predictions can be made in the future. The team is confident about their decisions, but according to Marijn, assumption should never be made. “We have expectations about how the new panels will behave, but there is never certainty in reality.” Perhaps more light is reflected at a certain angle so that the panel converts less light into energy. All practical information is invaluable for the next race. Anyway, let's focus on this year's race first.

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