If you organize a 1-on-1 with this person, then fill in the timeslot and your name in the table below.

Presentation Slides

Question 1: Interfacing solar array with larger/heavier vehicle than standard cruisier

Requirements for integrating solar to power major vehicular functions of a regular car

• Small frontal CRA

• Light

• Driving under 75mph

Bottom line: Not enough power for drivetrain

Question 2: For someone new in this environment, how to immerse yourself with solar tech

• Solar car design team

• PV Education.org

  • Solar Cell Operation

• Keep up with the industry and the news in it

• Work with different people in different fields

• Think about how your skills can integrate with other people in the field to achieve vision

Question 3: Sunpower solar project - (one of the projects she is working on )

• Use conductive adhesive to stick the panels.

• Laser cut strips

• Shingle panels together

Question 4: Biggest areas for innovation in solar array

Monocrystalline is current standard e.g:Topcon etc (getting around 23% power efficiency)

Biggest areas of innovation then since max theoretical power efficiency is 29% would be:

• Cost down

• Using the module area better for the solar panels

Question 5: Keeping solar array clean and efficient during race

• Make sure electronics are potted or protected in a water resistant enclosure

  • Make everything assuming that things will be completely soaked

  • Get waterproof heat shrink

  • RTV PV-804 (have to use special acetate-free rtv)

  • Have a hole underneath driver so person is not sitting in a puddle haha

  • Front sheets could use fluorinated polymers

    • use deionised water and microfibre to clean and keep it cool

Question 6: PCB Debugging

• Highly recommend external IR camera

  • Inspect everything you make in IR

  • Observe your solar array when it is in the sun using IR; you could detect hot cells or broken parallel pathways or other issues

  • Ask FLIR for donation if possible : ) (if we don’t have one already)

Open

Good for small resolution but the Fox and Hound is fine for automotive wiring

• Really great for troubleshooting

Open

Feb 26

Question 7: Is Silicon still competitive when so many teams are using GaAs?

• Depends on the rules

• GaAs is thicker, SunPower has copper on the back and is a little more resistant

• Looking at regs -

• Smart diodes - TI smart diodes - Gochermann was laminating them into the arrays of other teams for bypass diodes

  • 25mV drop - FETs and ideal diode controller in one package

• What is your team good at - can tradeoff in other areas to make this better

• 2008, (2010), 2012 and 2013 went well

• Wh per mile for each speed - see if other teams are willing to share info?

• Single person 3-wheel cars is ~3/4 of power loss for

  • Berkeley is really nice

  • Stanford

  • Minnesota

  • Are all really nice to talk to

•  

Question 8: Testing the array

• Each module - do curve tracing - tilted towards the sun, preferably between 10 and 2.

• Oregon they just couldn’t test the array

• Good to have an irradiance meter - use a reference cell

• Electoluminesce - 1200nm or 1170nm

  • Can’t see them with camera of FLIR IR camera either

  • Working on making one out of a Raspberry

• Monosilicon cells will generally crack on

  • point crack will look like an X

  • Copper on back side - sunpower cells

  • Gray ish areas - voltage differences

  • RPi HQ Camera - EL with a raspberry pi

    • Remove the IR filter

  • Power supply into cell - + to +, - to -

    • Put approx Voc and 1/2 or 1 Isc into the array - votlage must be above the VoC

    • Current will affect the exposure time

    • Exactly what components to purchase in the presentation tomorrow

      • Add in a visible light filter

  • Just call FLIR for an IR camera - $200 for a FLIR One

    • FLIR module in a cell phone

    • Even a crappy one on hand is so much better

• At Intel

  • Old Caterpillar cell phone had a FLIR camera

    • Turned it off immediately and fixed backwards component

•  

Question 9: Copper on the back of SunPower cells

• Interdigitated - one top of each other

• Front contact cells- silver frit material

  • SEM images show that these are not crystalline metal - they crack super easily

  • Back contact - aluminum frit material

Silver FRIT - glass and silver mixed together

Copper on the Sunpower cells is a solid matter

A lot of metal compared to the rest of the industry

Copper instead of silver - can get away with it due to a complicated layering

In lines on the back side - PN junction

White backsheet - reflects stray light back

Question 10: Cell characteristics for reliability

Module design, not just electrical geometry

Front sheets - we don’t really need to worry

Are the solder joints good? Will they last through the race?

EL and IR works really well.

You made an ideal design - now what’s going to happen in the real world - performance analysis and expected

Power trackers - buck is higher efficiency

GaAs - tiny bodies with too many different angles

katherine.han@sunpowercorp.com