Tuesday, October 28, 2014

Building One of the World’s Most Efficient Electric Cars

Tecplot 360 EX helps Stanford University students optimize design of solar-powered car to compete in the Australian Outback’s World Solar Challenge

The sun shines down upon the immense Australian Outback like nowhere else, drenching the land in solar energy that begs to be tapped. Where better to stage the World Solar Challenge, a design competition established to find the world’s most efficient solar-electric car? Every two years, some of the brightest student minds from leading universities around the world, and even some corporate competitors, gather in Australia’s Outback with solar-powered cars they’ve designed and built from the ground up to vie for the champion’s title. This brutally competitive five-day, cross-continental solar race begins in the Northern Territory city of Darwin and runs more than 3,000 kilometers (1,864 miles) south to Adelaide in South Australia.

“We’re operating with very tight design constraints,” says Guillermo Gomez, team lead for the Stanford Solar Car Project. “We can use no more than six square meters of solar panels, for instance. The solar car has to be a fully-functional vehicle, too, with a suspension, brakes, room for a driver, and so forth. The only two ways we can achieve any real design advantage is through a good power management strategy and an aggressively-shaped aerodynamic design.”

Stanford Solar Car 2013

Stanford Solar Car Project finished fourth in the world at the 2013 World Solar Challenge with this solar-powered car. The car has a carbon-fiber body and is powered by energy from the sun that’s collected by six square meters of solar panels and stored in a battery pack as electricity.

The Stanford Solar Car Project, which finished fourth in the world at the 2013 competition, is a non-profit organization run entirely by students at Stanford University. They have built nine generations of award-winning solar-powered vehicles since 1989, and are presently designing their entry for the 2015 competition. With previous World Solar Challenge winners averaging between 79.67 and 90.7 km/h (49.5 and 56.36 mph) over the course of the race, it’s safe to say that the aerodynamic designs for these solar-powered vehicles are already very finely-tuned. Squeezing a little more efficiency out of the car’s design requires increasingly-powerful and sophisticated tools.

CFD Analysis Helps Students Effect Significant Changes in Design

Fairing Reveal

Tecplot 360 EX image showing pressure and airflow around the leading edge of the car’s main airfoil and right fairing.

“We could improve the battery only so much, so aerodynamics are where we know we can realize the most improvement,” says Gomez. “We had some ideas about what we wanted to do with the body to optimize performance, but needed to test them. That’s when we started collaborating with the SU2 team at Stanford to better integrate more advanced Computational Fluid Dynamics (CFD) into the design process.”

One key design challenge was optimizing the vehicle’s body for the wide and constant range of cross winds in the Australian Outback. The Stanford team not only had to optimize the body for airflow moving over the vehicle as it moved forward, but also needed to consider how winds might push the side of the body and the wheels from a select range of angles.

Optimizing for frontal drag at 25 meters per second and a range of cross winds, the Stanford team ran their CFD analyses using SU2, the open-source CFD solver code developed in the Aerospace Design Lab at Stanford’s Department of Aeronautics and Astronautics, meshed the car bodies with Pointwise software, and visualized results with Tecplot 360 EX with SZL Technology.

“These three tools integrate so well together that it was easy to set up, run, export, and visualize the data, which was 10 to 15 million cells in size,” says Gomez. “The resulting visuals have been really impressive and very appealing. Of greatest importance, though, the CFD analysis has helped us make significant changes to the body design that should help us compete more effectively.”

There’s still quite a bit of work and testing to be done, and the final design will not be unveiled until the summer of 2015, but Gomez promises that the end result will be a beautiful, aerodynamically-optimized solar-powered car that should give their competitors a run for their money in the Outback.

Leading Edge

Close-up showing pressure and airflow around the main airfoil’s leading edge.

Trailing Edge

Pressure and airflow around the trailing edge of the car’s main body airfoil and the rear of the fairing.


Future Applications

The primary objective of the Stanford Solar Car Project is to provide students with valuable hands-on engineering, technical, and business experience while also serving to help raise community awareness of the power of solar-electric energy. But the technologies being developed today also promise to lead to more efficient electric cars in the future, and if history can tell us anything about the future, it may lead to many uses not yet imagined.

Stanford Solar Car Project  |  Tecplot 360  |  Pointwise  | Standford SU2

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