OSU Solar Vehicle Team

SVT

Solar Vehicle TeamOregon State University

Background Information – Solar Cars

• Solar panels directly on car

• Completely enclosed system– No external energy input

• Aux. battery pack to store excess energy for later usage

• Solar cars mainly seen in two events– North American Solar Challenge (NASC)– World Solar Challenge (WSC)

Solar Car Races: NASC and WSC

• World Solar Challenge– 3000 km race from Darwin

to Adelaide– 10 day race

• North American Solar Challenge– 2400 mile race from Dallas,

TX to Calgary, Canada• Highway format

– Highway speeds, traffic– Must be street legal (auto

insurance, plates, VIN, etc) WSC

Solar Car Races: NASC and WSC

• Fastest cars in World Solar Challenge can go faster than 142 kph

• Top 2 to 3 vehicles can sustain posted speeds throughout race

NASC 2008

Solar Array and Batteries

• 6 m2 or 9 m2 solar array surface area allowed

• Generates around 1800W (2.4 HP) peak with triple junction GaAs

• Batteries only store 5 kWH (1.34 HP for 5 hrs)

• How is propulsion possible? Triple junction GaAs cell [2]

Forces and Power Balance

Pin = small, maximized

Pout = small, maximized

Fdrag minimized

Design Goals

• Efficient power input

• Efficient power usage

• Low aerodynamic drag

• Low mass

Efficient Power Input – Best Cars

• > 26% efficient, triple junction GaAs array on fastest cars

• > 98% efficiency electronics

• High efficiency Li-Ion/LiFePO4 for charging and discharging.

• Concentrators used on Univ. of Michigan car

U of M solar car evening charging with concentrator sub-array

Lowering drag

• Reduced weight– Carbon fiber– Aluminum/Titanium chassis– Most cars weigh 200 to

300kg• Better areo

– Cd of .21– .741 m2 cross sectional

area– Cd * A = .156– CFD/wind tunnel testing– Attention to detail – fillets,

ridges

2010 OSU Solar Car in wind tunnel

OSU Solar Vehicle Team

• OSU’s first solar vehicle – First car in Northwest– $50,000 budget vs. $2.4

million of U. of Mich.– 16.4% efficient cells– Brushed DC motor, 94%

efficient peak (linearly decreasing to 0 as RPMs drop)

– Fiberglass body– First titanium chassis in

NASC history– LiFePO4 battery pack– 15th out of 24 entrants

OSU Solar Vehicle Team (cont’d)

• 2010 OSU Solar Car: Odyssey – 17.4% minimum efficiency

mono-crystalline SolarWorld solar array

– Optimized prepreg carbon fiber body

– Ti-425 titanium chassis and suspension

– 95% efficient NGM PMAC wheel motor

– 0.21 Cd drag, 0.74 m2 frontal area

– Goal for top 5 cars in 2010 NASC

– Anticipated speeds• 45-50 mph cruising• 85 mph top speed

Odyssey Solidworks Schematics

Case Study: Body Design Process

• Customer need:– Maximum solar

surface area with minimum drag

• Problem definition & specifications– Body must fit within a

box that’s 1.8m x 1.6m x 5 meters and hold solar array

Body Design Continued

• Data and information collection– Looked at over 30 vehicles from 1989 to

now– Consulted books and experts

• Evaluation of design and selection of optimal design– Ran computational fluid dynamics on more

than 100 separate designs– Tested two best designs by 3D printing at

EECS and using wind tunnel in Rogers

Body CFD

Body Wind Tunnel Testing

Implementation of Design

• Implementation of design– Carbon fiber composite fabrication

Making the Car

• Phase 1: Making the chassis, suspension, steering, body, wheels

• Phase 2: Making the power electronics, attaching motor, batteries

• Phase 3: Attach solar cells

How You Can Help

• Help out with design and construction

• Attend construction meetings– Meeting times will go out in emails, but will

typically be Tuesday, Thursday, Friday and Saturdays.

– Sign up by emailing osusvt@gmail.com

• Visit our website at: http://oregonstate.edu/groups/solar