TexSun is the newest completed car to be built by UTSVT. It was completed in the Spring of 2013 and took part in the FSGP 2013 held at the Circuit of the Americas in Austin, Texas. The car is currently undergoing further modifications in preparation for the FSGP 2014 and the ASC 2014, both of which will start in Austin, Texas.
We began work on TexSun’s design in the fall of 2010. Similar to the design of our previous car, the Samsung Solorean, most of TexSun’s design was completed using SolidWorks CAD software. As we went through the design process, we made several fundamental changes based on lessons we learned from the designs of our previous cars. A few major design changes relative to the Samsung Solorean include:
- General modularity of the design
- Adoption of an aluminum chassis
- Inclusion of a body with a detachable array
A major result of these changes was a reduction in the overall weight of the car. TexSun was completed with a weight of 350 pounds (without a driver), which is 250 pounds lighter than the Samsung Solorean.
In our previous cars, we used steel to construct the chassis. In contrast, TexSun was built with a tempered aluminum space frame chassis with an aerodynamic carbon fiber shell. The 6061 aluminum used for TexSun’s chassis is much lighter than steel and can meet the necessary strength requirements due to the TIG welding and heat treatment that was applied to the material by Alfe Heat Treating. In addition, the aluminum was quenched in a polymer glycol solution and set in sub-freezing temperatures for 24 hours to attain a degree of stress relief. The resources and expertise of one of our sponsors, Alfe Heat Treating, have been very beneficial in the development of our new chassis. For example, we were concerned that we might need to drill 1/16 inch holes throughout the chassis to alleviate quenching problems during heat treatment. However, after Alfe tested mock pieces of the chassis, we were able to avoid this issue.
TexSun’s solar panel arrays are located on its detachable wing that comprises the largest portion of the car. The array is made up of 3 smaller sub-arrays of silicon monocrystalline cells, which were manufactured by SunPower. The car includes two sub-arrays at the front end of the vehicle and a single sub-array at the rear of the vehicle.
The type and quality of the solar cells used for TexSun’s array was dependent on several factors. First, the American Solar Challenge has specific regulations regarding the materials that are allowed to be used. Second, the efficiency of each cell is crucial in order to optimize the performance of the car. Additionally, an important constraint is the cost of each cell. The cost of solar cells increases with efficiency, so there is a balance that we reached between the two factors. For the SunPower cells used in TexSun, each cell has a rated efficiency of 22.5%. With 390 cells across the three sub-arrays, TexSun’s total array area is 5.98 m2, which is within the limits (6 m2) set by the American Solar Challenge.
In addition to the solar cell arrays, a major part of TexSun is the battery pack and the required battery protection system (BPS) designed for the car. The batteries used in TexSun are lithium iron phosphate batteries manufactured by A123 Systems. Each cell has a capacity of 2.5 Ah and a nominal voltage of 3.3 V. The battery pack for TexSun was designed with 36 modules in series with each module including 14 battery cells. The batteries were placed in a flame-retardant box that the team created. In total, the batteries weigh approximately 38 kg.
[img src=http://utsvt.com/wp-content/flagallery/texsun/thumbs/thumbs_texsun-chassis-and-rear-suspension.jpg]Model of chassis and rear suspension
[img src=http://utsvt.com/wp-content/flagallery/texsun/thumbs/thumbs_chassis.jpg]Completed aluminum chassis
[img src=http://utsvt.com/wp-content/flagallery/texsun/thumbs/thumbs_body-plugs.jpg]Foam plugs for body shell
[img src=http://utsvt.com/wp-content/flagallery/texsun/thumbs/thumbs_all-plugs-at-yps.jpg]Foam plugs for body shell
[img src=http://utsvt.com/wp-content/flagallery/texsun/thumbs/thumbs_wing-plugs.jpg]Foam plugs for body shell
[img src=http://utsvt.com/wp-content/flagallery/texsun/thumbs/thumbs_upright-assembly.jpg]Model of front upright assembly