Solar Vehicles Part 1

Solar Powered Vehicles at Queen’s University Tom Simko Department of Mechanical Engineering Queen’s University Kingston, Ontario

PRESENTATION OUTLINE z Design of Main Parts: -Aerodynamics (Overall Shape) -Chassis & Materials -Solar Array -Battery Pack -Mechanical z

Image from: National Solar Observatory

Car Theory: Fundamentals

Racing -Race Strategy -American Race -Australian Race

Where does the Energy Go? Parasitic Parasitic 7% Losses 7% Aerodynamics Aerodynamic Drag 17% 17%

Motor Motor 5% 5%

Rolling

71%

Rolling Resistance 71%

Energy requirements at 25 km/hr Total: 211 watts

Where does the Energy Go? Motor 6% Rolling 28%

Parasitic 1%

Energy requirements at 90 km/hr Total: 2655 watts

Power Consumption Summary

Aerodynamic Drag 65%

Aero Drag increases with the cube of the car speed, V (i.e. Aero Drag ~ V3)

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AERODYNAMICS (SHAPE) z z

z

z

We want to minimize the air resistance (DRAG) because this slows down the car. This involves AERODYNAMIC STUDIES with computers or with wind tunnels to come up with an optimal design.

Aerodynamics

Overall shape should be: -Sleek, short and curved (like a wing). -The driver should be semi-lying to keep height to a minimum. Shape should not be too wing-like and aerodynamically efficient because the car could take off and FLY!!!

Queen’s Solar Vehicles

Aerodynamics Computer Modeling Results

Gemini (the 2003 Queen’s Solar Car) Canada’s first two-person solar vehicle

Queen’s Solar Vehicles Photo Credit: Stefano Paltera / American Solar Challenge

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Aerodynamics – Wheel Covers (Farings)

CHASSIS

The Cockpit

Chassis

The Chassis supports: z The

top aeroshell to which the solar cells are attached z The driver z The internal components such as the battery pack and motor z The suspension system (which is attached to the chassis)

Chassis: Two design options: z Tubular

space frame made from lightweight metals or alloys (e.g., Aluminum, Titanium)

z Integrated

one-part construction made from lightweight materials such as Fiberglass or even lighter and stronger composite structures such as: -Kevlar/NOMEX or -Carbon Fiber/NOMEX

Chassis – Tubular Space Frame Computer model for design analysis

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Chassis – Tubular Space Frame

Chassis – Integrated Construction Computer model for design analysis

Gemini Composites

U Michigan Composites

SOLAR CELL ARRAY

A Solar Photovoltaic Cell I

Light Top metal contact n-type region doped with Group V Element (surplus of electrons)

Load

Current

p-type region doped with Group III Element (deficit of electrons) electrons) Back metal contact

-Converts light into electricity -Essentially a specialized semiconductor: A Solar Cell consists of a Silicon wafer doped with impurities to create a junction. -Gallium Arsenide is also used as a substrate -Typical efficiencies are 14-22%. Record: 32% (triple junction). -A typical price: ~ $600 for a 75 watt Panel of Solar Cells!!!

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Solar Cell Array z Gemini

has 3450 cells that are normally used for satellites. Each cell produces 2.2 Volts.

z Cost:

About $100 000 !!!!

z VERY

fragile – Careful assembly is essential.

Solar Cell Applications

z 2500

Person Hours to assemble array.

Individual Solar Cells Array Construction: Step 1

Array Construction

Array Construction

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Array Construction: Step 2

Array Construction

Array Performance

BATTERY PACK

z About

2000 watt peak output.

z

Stores extra power not needed when the car is already travelling at optimal speed. This power is used later during bad weather or when climbing hills.

z

504 Lithium Polymer Battery Cells (similar to those used in palm pilots and computer laptops).

z

The battery pack stores 5.4 kWh (kilowatt hours).

z Holder

of the World Record for Solar Car Array Output: 1972 watts.

z Average

panel efficiency: 20-22%.

z Under

the midday sun, Gemini can cruise at 85km/h and still have enough extra power to charge the onboard battery pack.

Battery Pack

Battery Pack

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