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Sure, it's not as good as a cheap, reliable energy supply from a national grid but it might be an option for those off-grid... like rural rice farmers and testers during northern european winters ;-)
Others doubt the appeal of off-grid solutions. “The poor...want grid-based power like urban households that can run TV sets at the flick of a switch,” says Lydia Powell, senior fellow and energy expert at the New Delhi-based Observer Research Foundation.
miro_o-
it might be an option for those off-grid... like rural rice farmers
If you have enough sunshine to grow rice, you have enough to generate your 250Wh per day with Solar PV for well under the $100 target price of his bicycle, and you don't have to waste a couple of hours when you could otherwise be working to get it.
gbj_tester
In the target markets, people who are too poor to buy fuel are frequently also too poor to buy enough food, i.e. they are just about getting by in terms of calorie intake. If you ask them to provide 0.25kWh per day to power their lights, they would need about (0.25×1000×3600)/(4200×0.2×0.7)≈1500 Calories per day of extra food. The numbers in there are 0.2 for human efficiency and 0.7 for generator efficiency, there's nothing in there for drivetrain or battery/charger/inverter losses, so the real number will be quite a bit higher. If you're eating 1500 Calories a day because that's all you can afford, more than doubling your intake to get some electricity doesn't seem like either a priority project or even a sensible allocation of resources.
1500 Calories is about 1kg of rice, and you need a minimum of 776kJ of fuel to cook it to get your 900kJ of usable output.
Mains electricity costs about 5p for 250Wh in the UK, maybe a bit more in developing countries with lower population density. Best offers I can find on domestic quantities of rice at the moment are a bit under £1/kg here, even by the ton on the Indian wholesale market it only drops to about Rs2100/Qtl for the cheapest grade (called "Government Quality", which tells you all you need to know about Communism) equivalent to about 20p/kg