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