Sirius X25
The NWU Solar Car, Sirius X25 is the culmination of advanced technologies and innovation that sets a benchmark for South African solar car design. Named after the nearest star to earth’s solar system, Sirius (which shines 25 times brighter than Sol), this is one vehicle truly worthy of its name.
The NWU Sirius X25 incorporates several innovative features:
- A sleek profile which gives the vehicle aerodynamic drag better than the best sports cars in the world.
- Hand built from advanced composite materials, making it extremely light and strong.
- New material strength modelling techniques were developed as part of a research project and applied in the design of the solar car. The result is a super lightweight vehicle that does not compromise on safety.
How does a solar car work?
Sunlight is the only power source available to the car, which is harvested by a solar panel. State-of-the-art encapsulation captures every ray of sunlight whereafter high efficiency electric motors that are paired with dedicated motor controllers transfer the electric power into motion.
These motors are mounted directly in the hubs of the front wheel. The front wheel drive system and the finely balanced weight distribution of the car further increases on road dynamic stability by eliminating over steer.
A high energy density lithium-polymer battery is placed between the solar panel and the electric drive system and captures energy generated by the solar panel as well as energy recuperated during braking. A battery management system coordinates and manages all energy flowing from and to the battery, ensuring safe operating conditions at all times.
Structural Design
Pieter Brand, Masters student in Mechanical Engineering, was in charge of the structural design of the new solar car, Sirius X25. His main responsibility was to ensure that everything inside the car is safe and stable. This project is quite valuable for Pieter, not only because of the experience he gains, but also because it is the theme of his master’s degree.
Responsible person
Pieter’s main goal was to design the frame of the car in such a way that it would be as light as possible, in order to ensure that the car would be energy efficient, by using the right materials. Pieter explains that the car is built out of carbon fibre, which was applied layer upon layer, until it formed composites. His main focus was on reducing the weight of the car, as well as sustaining stability by using an a-symmetrical design. He was in charge of placing objects like the batteries in a place where it would enhance the car’s energy efficiency.
Challenges
Pieter’s biggest challenge was to keep the concepts of other parts of the car in mind when designing his part, because his designs would have to support other components and therefore has to be in line with the overall design strategy. This kind of project is quite time consuming, therefore one's social life also suffers the consequences.
In comparison to the Batmobile
Sirius X25 was approached differently (different materials were used more effectively and there was more attention to detail), based on experience gained by working on the Batmobile. In terms of weight, the new car was 100kg lighter than the Batmobile and almost three times as fast.
Competitive edge
The team was also bigger this year, seeing that the marketing team alone contained 6 people. There were also more people in charge of logistics; therefore the team efforts were focused, but at the same time cohesive.
Aerodynamic design
Armand Fourie, Masters Student in Mechanical Engineering, is in charge of the design of the new solar car. His main responsibility is to ensure that the car is as aerodynamic as possible. Armand was also involved in the aerodynamic design of the 2012 Batmobile that won the Sasol Solar Challenge.
What is the focus?
Armand is involved in the physical appearance of the car, as well as the strategic design thereof. In order to ensure that the car is built with the competition strategy kept in mind, he considers aerodynamics as the most important aspect of the design. He opted for an assemetric design combined a variety of wing profiles, in order to ensure optimal air flow, since a flatter object moves easily through the air. He also installed fairings around the wheels and built the canopy in such a way that it reduces drag force. His main goal is to design a car that consumes as little energy as possible.
How far is the design process
The mould of the chassis is done. The upper part of the car still needs to be cut, as well as the canopy, the fairings and the driver’s cabin.
What comes next
The mould of the chassis can now be used to start with the carbon fiber process. As soon as the chassis is built and assessed, the electrical components will be installed, which means that the car will be able to drive (using battery) while the other parts are still in progress This allows the effectivity of the chassis’ to be tested. As soon as the moulds of the upper parts of the car is finished, there will also follow a carbon fiber process and the parts will be put together. Then the solar panels will then be mounted.
Challenges
Reducing the coefficient of drag to a value where it is acceptable for energy efficient usage. Also to find a balance when putting all the different parts together, to ensure that the car as a whole will be energy efficient.
In comparison to the Batmobile
The drag of the new car will be about twice as good as the previous car. Armand expects the new car to be able to drive 4000km, which is a huge improvement on the Batmobile, which drove 1089km during the 2012 Sasol Solar Challene.
What to expect in the upcoming race
Armand is looking forward to the upcoming race and thinks it will be a fun competition, since the South African teams are pretty much on the same level. Armand expects good competition from KZN and is also looking forward to see how the foreign teams will perform.
Competitive edge
The team is quite small, therefore everyone is dependent on one another. Individuals aren’t just busy with their own tasks. The team therefore relies upon cohesion in terms of team work. The strategic planning also boosts the team performance.
Rivals
Tōkai is seen as the biggest rival, since they have quite some experience in competing in South Africa. They know the terrain, therefore they know what to expect and will come prepared. They also have a very expensive car.
Another victory?
There were rumors that we won the previous race by luck, because we were not in the same category as Tōkai. This time around we are in the same category, but since we have a better car this year, it might just be a close competition. Luckily they will not be driving at a dreadful pace of 30km per hour from Pretoria to Cape Town!