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