Power Generation Notes

These are notes compiled from the peripherals mailing list

Power options

• Bicycle
  • Dynamo (output typically 12V, 6W)
    • Put 3 in parallel, Ouput 12V ~18W, might not be enough voltage to charge XO
    • Put 2 in series, Output 24V ~12W, high end of XO’s input
  • Alternator
    • Are expensive in Peru, costs $300 approx for Korean “Tico” (Javier Comment on OLPC Peripherals list)
    • Could be built from scratch- copper wire and magnets that are imported
    • Low rpm alternators are likely needed for bicycle generator allowing power output as low as 60 rpm
      • For a custom made alternator, lower rpms can be achieved by increasing the wire in the alternator, but this will also decrease the overall power output
    • Alternators could possibly be bought cheaply in US and shipped to other countries where it's more expensive (Caryl Comment on OLPC Peripherals list)
• Wind
  • Typically need a tower about 2.5 times higher than nearest building or tree ~30 ft typically
  • Vertical axis wind turbines- Savonius, Darius wind turbines
    • http://www.appropedia.org/Energy_from_the_wind
    • http://www.appropedia.org/Category:Wind_power

Storage

• Battery
  • Can use a rechargeable battery for charge storage
  • Need a full wave bridge rectifier- (Richard Smith Comment on OLPC Peripherals list)
  • Chance of deep cycling LA car battery, typically don’t want to drain charge below 50%
  • Need a charging protection circuit, don’t output more than 14.5 V- (Nick Foster Comment on OLPC Peripherals list)

Could charge a battery and then discharge to the XO- no need for a ultra-capacitor or flywheel, but there are additional power losses

• • Car battery- 12V output, circuitry to cut off, 35A for $100
  • Need to charge XO at 1.5A and 12V for 2 hrs

Estimated Costs for Implementation (Josh Seal Comment on OLPC Peripherals list)

• Personal Solar: $20 per XO (Variable effectiveness and difficult for a

classroom environment)

• Classroom Solar: $35 per XO (Assuming peak efficiency - Roof solar with charge controllers and power distribution)
• Classroom Wind: $15 per XO (Assuming peak efficiency - Wind Turbine

tower outside school - variable output - Wind power generates the cube of velocity)

• Hand Crank: $15 per XO
• Cow Power: $13.75 per XO (35A Alternator ($300) + Gearing ($150) +

Batt ($100) = $550 for 40 XO)