User:Ccarrick/Power Generation
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The power generation talk during one of the Wednesday sessions of the Global Country Conference was helpful in gaining a sense of the current challenges for generating power for the XO. Take home messages are 1) human power generation is viable only if it can be sustained for 2 hrs or more, 2) grassroots options provide a lot of flexibility but are very location specific and 3) multi-battery chargers are incredibly helpful for charging XOs. Notes taken from the talk are below:
How much power does the XO consume?
- Depends on state of XO
- Charging
- Max draw of 17 W
- Not Charging
- 1 W idle
- 4-7 W Average
- 9 W peak, when using camera
Charging
- Laptop off
- 1 hr 47 min at best
- Laptop on
- 2 hrs 30 min
Battery good for 2000 cycles Off Grid Charging Options
- Solar Panel
- Durable amorphous silicon panels that can be rolled, though not the most efficient
- 5 W Panel
- Charges with laptop off in 5 hrs 15 min
- Not intended as a primary shipping device
- 7 W Panel
- Charges with laptop off in 3 hrs 45 min
- 10 W Panel
- Charges with laptop off in 2 hrs 40 min
- Can be made into a solar blanket which folds into a compact shape as well, though this option is more expensive
- 60 W Solar blanket
- Charging times highly dependent on weather
- Charging times not linear- Doubling wattage doesn’t halve charge time since battery can only charge so quickly
- Weza
- Foot pedal
- 30 W output
- Charges 2 batteries in 2 hrs using a 7ah lead acid battery
- Costs $160- $200+
- Crank
- 22 W, requires 2 hrs of constant cranking
- Not viable until Gen 2
- Grassroots efforts
- Cow power- Arjun in charge of this
- Wind, water, pedal, treadle
- Freeplay currently working on water generator
Human Power Generation
- Requires at least 1 hr and 47 min to charge a laptop
- Can transfer power to a separate battery to recharge more than one laptop battery at a time
Multi-Battery Charger
- Prototype available, hoping to get price below $300
- 300 W AC
- Charges 15 batteries in 2 hrs
- 120 W DC
- Requires 10-28 V input
- Charges 8 batteries in 2 hrs
- Can direct connect two 60 W solar blankets to charge batteries
Battery life
- 4 hrs during normal use
- 14-16 hrs in sleep mode
Helpful information for implementing power generation at a location
- Climate & geography of area
- Natural resources available
- How many schools/kids/kids per class
- Reliability of grid
- Expected laptop usage