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 MissouriRolla
– 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.php
solar42.umr.edu
www.americansolarchallenge.org/
Aerodynamics
Conservation of Momentum
• Drag
– Total area
– Sharp Corners
– Turbulent Flow
– Curve
Discontinuities
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
• Solar Panels
• Wheel Fairings
– 1.038 m x .527 m (2)
– Turning radius of car
– 1.559 m x .798 m (4)
– Only on back wheels
Design of Shell
• Flat Surface Area for
Cells
• Flat Sides with Fillets
• Leading and Trailing
Edges
• Curved Underbelly
Flow Analysis With Canopy
Air Density: ρ=1.29 kg/m^3
Streamlines
Air Velocity: U∞= 20 m/s
Dynamic Viscosity: μ=1.5 X 10^-5 N*s/m^2
Pressure
Pmax=264.876 Pa
Velocity
Umax=35.786 m/s
Flow Analysis of Sides
Air Density: ρ=1.29 kg/m^3
Streamlines
Air Velocity: U∞= 20 m/s
Dynamic Viscosity: μ=1.5 X 10^-5 N*s/m^2
Pressure
Pmax=155.613 Pa
Velocity
Umax=29.868 m/s
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
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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