[Gravityloss]

1 watt of led light would require 1 Newton at 1 meters per second. Assuming 100 kg is the highest practicable mass, so that's 1000 Newtons -> 1/1000 m/s for each watt. Assuming a height of 2 meters, you could operate a very dim 2 watt led light for 17 minutes. I think that's not practical.

[jameshart]

Or, using the numbers provided for this actual product which exists, rather than a spherical LED on a frictionless plane, we raise a 12kg mass 1.8m and get a 0.1W LED light for 20 minutes. Do you think THAT's practical?

[Retric]

0.1W LED light is as bright as one of those clip on book reading lights, they only look bright in pictures. It's not quite useless, but you can build a 0.1w for 12 hour solar light with a 12' cord for ~2$ making the whole thing a joke.

[Gravityloss]

Ok, I confess to not reading the article, I was just reacting to the comment. That actually starts making a lot of sense.

[CyberDildonics]

You can use it to read and it is free.

[imaginenore]

It's not free. It's a very inefficient way of converting food to human energy to humans lifting weights that in turn power the lights.

If this is targeted at very poor people, food isn't cheap for them.

[Gravityloss]

If you think about the methods of farming worldwide etc, they also use a lot of human labor etc because there's not enough sophisticated industry to run everything on solar charged battery powered robot tractors... So you have to accept a local optimum.

Reading for half an hour per day could have large payoff, compared to reading very little ever, because it's too dark.

[CyberDildonics]

Neither is kerosene. Many people reply based on their gut feeling, but that doesn't mean it lines up with reality. A chocolate chip cookie has enough energy for a person to go jogging for 20 minutes. No one is going to starve to death by lifting a weight every 20 minutes for a few hours at night. They might be able to lift themselves out of poverty if they stop paying for kerosene and read (or learn to read) in the time that they aren't working, which is likely at night.

[kragen]

The energy involved here is between one and two grains of rice.