Solar Car Shell Design Allison Bedwinek, Douglas Simmons, Sheldon Low, and Laura Sullivan ME 43A...

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