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Calsol Solar Team Produced Optimized Design Using Simulation

CalSol Solar Vehicle Team, UC Berkeley, is a student-run organization that designs, builds, tests, and races solar vehicles capable of traveling at highway speeds. Through participation in solar races and alternative energy as well as community outreach events, the team also aims to raise awareness of solar energy while focusing on the engineering challenges inherent in solar vehicle technology.

Calsol Solar Vehicle Team

In order to be a competitive vehicle team, an aerodynamic vehicle design and good battery cooling systems are very important.

ANSYS has been used extensively to determine the most optimal shape for our one seater, challenger class solar vehicle. Conducting flow simulations on the outer carbon fiber shell of our design allowed us to create the most aerodynamic shape given the other design constraints of the vehicle like the solar cell placement and optimal curvature for the cells, and the dimensional requirements specified in the competition rule book.

 Simulation of shell aerodynamics for our solar vehicle, Zephyr

Aerodynamic efficiency of the shell of the vehicle, while very important, is not the only area of design that has benefited from ANSYS simulation.

As our solar vehicles are all electric, the power from the solar cells is stored in 420 lithium ion batteries. While these batteries are fairly durable and work quite well under normal conditions, there is a cut off temperature above which it is unsafe to charge the batteries. To ensure that we never reach this cutoff temperature and have to stop charging the batteries, ventilation in our battery system is very important.

Simulation of battery box ventilation

During our most recent competition, the Formula Sun Grand Prix 2015 held in Austin Texas at the Circuit of the Americas, the outside temperature reached 100 F during the competition. Needless to say, this significantly hindered our battery ventilation system and we had difficulties keeping our battery system cool enough to continue charging without exceeding the safe charge temperature for the batteries.

This past semester, ANSYS was used extensively to improve our battery ventilation system for the vehicle. The simulations have been very beneficial in providing feedback for our different designs without having to use time, energy and money to build prototypes of each design to test, and significantly accelerated our design process. This coming summer, CalSol will be racing our improved vehicle in the American Solar Challenge, a cross country race from Ohio to South Dakota against other solar vehicle teams.

Zephyr at the Circuit of the Americas starting line for FSGP 2015

In the coming year, we look forward to begin development on our ninth generation vehicle, a 2-4 seater ‘Cruiser Class’ solar vehicle. ANSYS will be used a great deal in designing and optimizing the aerodynamic shell of this new vehicle and the results of the simulation will impact the rest of design of the new vehicle as we strive to find the perfect balance between our aerodynamic efficiency and functionality of the vehicle.

To learn more about CalSol, visit our website, find us on Facebook and Twitter, or check out our photo stream!