Um, please read the entire previous thread before dismissing this as a hoax. As you can see from a number of posts that I and others made there, the light is comparable to a kerosene lamp, which is what it's intended to replace. It is not, of course, comparable to the kind of light we in developed countries are used to, but that's not what it's intended for.
How many people can lift 30kg 2 meters up? How about doing it continuously?
You're also forgetting that it require human energy to power it, which requires food, which is usually more expensive than batteries or gasoline or kerosine.
Lifting 30 kg 2 meters requires about 600 Joules. If it takes 10 seconds to do it, using some kind of pulley arrangement, that's 60 Watts, which is not a strenuous level of effort for a human.
How about doing it continuously?
One 10-second lift every 30 minutes is not "continuously". Also, it would only have to be done when light was needed, i.e., during non-daylight hours when people were not asleep.
it require human energy to power it, which requires food
Humans require food whether they're lifting ballast to power lights or not. How much additional food would they require, if we assume that the entire energy required for the lights is added on (i.e., none of it gets shifted from other forms of exercise)? Let's see.
Suppose the light is in use for 4 hours a day; that means the weight gets lifted 8 times, for a total energy of 4800 Joules. One food calorie (which is actually a kilocalorie) is 4180 Joules. So we're talking less than 1.2 calories per day. What's that, an extra pellet or two of rice?
Because if you used a sufficient number to light a room you would have to hire people to lift the weights continuously, and if you have to to that, it would be far more efficient if you hired them to generate electricity using a pedal powered generator, because that is still the most efficient way to transform human labor into electricity.
Come to think of it, pedalling for the time it takes to lift the weight and charge a supercap that will them provide electricity to the LED might still be better.
[Edit: Lets do the math: 100W effective for 30 seconds gives you 3000J electrical energy stored in the cap, drained over 3600 second provides an average of 830mW for an hour.]
Like others have said, this is in no way a replacement for a pedal-powered generator, nor is it a replacement for a standing lamp. It's for folks in developing countries who would gladly trade lifting a pound or two of weight for 30 minutes of dim light.
Be cynical about the math, sure, but if the math works, don't assume technology is useless because it doesn't have a place in a 25 year old's San Francisco apartment.
A pound of two? We are talking about 50 pounds, every 30 minutes, for very dim lighting.
It's not being cynical to say "It doesn't work". Cynical would be to dismiss it without even checking. We gave it a full consideration, ran the numbers, and realized: It doesn't, and Can not, work.
The numbers don't show that; that's your subjective judgment based on the numbers. But the judgment that matters is not yours, but that of the potential users. It's up to them to decide whether this is better for them than a kerosene lamp.
