Solar Car Shell Design

Allison Bedwinek, Douglas Simmons, Sheldon Low, and Laura Sullivan

ME 43A Fall 2004

Project Goals

• Design a shell for solar car– Overall aerodynamically superior car

• Low rolling resistance• Low coefficient of drag

– Incorporate solar panels• Meets voltage/current requirements from Electrical

Engineering team

– Lightweight, yet strong• Material selection

– Compete in the North American Solar Challenge• July 2005 race from Austin, TX to Calgary, AB, Canada

Major Specifications

• Rayce Regulations– Overall dimensions– Safety

• Cockpit ventilation• Driver Egress

– Visibility

• Nerd Girls– Frame– Solar panels– Drive train

Carbon Fiber Composites

• Carbon Fiber is a form of graphite in long thin ribbons.

• The fibers are used to reinforce polymers.

• Carbon fiber composites are used for everything

http://www.geocities.com/CapeCanaveral/1320/

Carbon Fiber Construction

• A plug is made of the desired car shape, and a mold is then built off of that.

• Carbon Fiber Tissue is placed in the molds while still flexible. • These molds are then pressurized and heated. The Resin in

the Tissue then adheres to the carbon fiber ribbons to form one solid composite in the desired shape.

www.secart.com

Research

• University of Missouri-Rolla– 2003 winning solar car

• Common Solar Car Features– Thin and streamline– Low to the ground– Unobtrusive

windshield and canopy– Wheel fairings

www.prin.edu/solar/home.phpsolar42.umr.eduwww.americansolarchallenge.org/

Aerodynamics

• Drag– Total area– Sharp Corners– Turbulent Flow– Curve

Discontinuities

Conservation of Momentum

http://ocw.mit.edu/ans7870/16/16.unified/propulsionS04/UnifiedPropulsion2/UnifiedPropulsion2.htm

Aerodynamics

• External Force: Pressure

– Cross Sectional Area

– Upward and Downward Pressure

www.gmecca.com/byorc/dtipsaerodynamics.html#Drag

Preliminary Considerations

• Car Frame

• Wheel Fairings– Turning radius of car– Only on back wheels

• Solar Panels– 1.038 m x .527 m (2)– 1.559 m x .798 m (4)

Design of Shell

• Flat Surface Area for Cells

• Flat Sides with Fillets• Leading and Trailing

Edges• Curved Underbelly

Flow Analysis With Canopy

Dynamic Viscosity: μ=1.5 X 10^-5 N*s/m^2

Pmax=264.876 Pa Umax=35.786 m/s

Air Velocity: U∞= 20 m/s

Air Density: ρ=1.29 kg/m^3

Pressure

Streamlines

Velocity

Flow Analysis of Sides

Dynamic Viscosity: μ=1.5 X 10^-5 N*s/m^2

Pmax=155.613 Pa Umax=29.868 m/s

Air Velocity: U∞= 20 m/s

Air Density: ρ=1.29 kg/m^3

Pressure

Streamlines

Velocity

Updates

• New solar panel layout– Customized modules of SunPower Corp cells built by SunWize– Significantly lighter and thinner

• F16 windshield canopy• More aerodynamic design

Updates

• Working with Secart LLC of Bethel, CT, a carbon composites engineering firm

• Mold construction is the most labor intensive step

• Plugs will be created from 3D models

• Next month, begin construction of molds

• Two versions of shell– 1st version – create door, add brackets

Acknowledgements

• American Solar Challenge

• Nerd Girls

• James Seeley, Secart LLC

• Prof Karen Panetta, Electrical Engineering

• Prof James O’Leary, Mechanical Engineering

• Matthew Heller and Rick Colombo, EE consultants for Nerd Girls