User:Ccarrick/Power Generation

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