Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

GravityLight: Generate light with gravity

gravitylight.org

Post reply on HN
Print view View original

31–40 of 132 posts

Re: GravityLight: Generate light with gravity

#31

Post by achr2 »

pavel_lishin wrote: post #28
achr2 wrote: post #27

Years ago there was a similar 'potential energy to electricity' buzz and I was initially quite excited. Then I did the math on how much energy is actually available (even at 100% efficiency) from such a scheme. Spoiler - it's minuscule. E = mass x 9.81 x height So a 10kg mass at 2 meters can (@ 100% efficiency) provide 196 joules of energy. A modern cell phone battery has about 25000 joules. To charge said phone woul…

But this isn't for charging a phone; it's for having light, right now.

I get it, I am just saying that there are a lot of ways to make a single LED light shine, potential energy from a weight is likely the least sensical.

Re: GravityLight: Generate light with gravity

#32

Post by haxiomic »

ajuc wrote: post #24

Nitpick, I know, but: it's not powered by gravity it's powered by human muscles, so in the end - by food.

I take your point, but the food ultimately gets its energy from the sun, which gets its energy from collapsing under gravity. I don't think there's a clear place to stop, but I'd say the name Gravity Light gets the idea across anyhow

Re: GravityLight: Generate light with gravity

#33

Post by mdturnerphys »

ajuc wrote: post #24

Nitpick, I know, but: it's not powered by gravity it's powered by human muscles, so in the end - by food.

If we're playing that game:

- Human muscles get energy from food.

- Food is or gets its energy from plants.

- Plants get energy from the Sun.

- The Sun's energy comes from gravity-forced fusion.

So gravity :)

Re: GravityLight: Generate light with gravity

#34

Post by leanthonyrn »

hanoz wrote: post #9

You need to lift a 10KG weight about 2 kilometres to get a teaspoon of kerosene's energy, so it's not a great replacement on that front, and having 10KG weights dangling around at variable points between ceiling and floor sounds if anything even more of a liability than a lamp with a naked flame, which does at least stay where its put. Sorry to be negative but it's difficult to conceive of a realistic scenario where…

Can't you suspend a bed wired to one of these to the ceiling? At night before you go to sleep climb the stairs and get into the potential energy elevated bed. Then in the morning, after the bed descends, you have enough reading light energy stored for the next night.

Re: GravityLight: Generate light with gravity

#35

Post by avian »

haxiomic wrote: post #32
ajuc wrote: post #24

Nitpick, I know, but: it's not powered by gravity it's powered by human muscles, so in the end - by food.

I take your point, but the food ultimately gets its energy from the sun, which gets its energy from collapsing under gravity. I don't think there's a clear place to stop, but I'd say the name Gravity Light gets the idea across anyhow

Sun is powered by fusion. Gravity just holds it together.

Re: GravityLight: Generate light with gravity

#36

Post by ajuc »

romaniv wrote: post #30
ajuc wrote: post #24

Nitpick, I know, but: it's not powered by gravity it's powered by human muscles, so in the end - by food.

I don't think it's a nitpick. I think this is a very important point. Is the hypothetical fuel more expensive than food?

LED is much more efficient than kerosene lamp, so I guess yes.

Re: GravityLight: Generate light with gravity

#37

Post by ajuc »

mdturnerphys wrote: post #33
ajuc wrote: post #24

Nitpick, I know, but: it's not powered by gravity it's powered by human muscles, so in the end - by food.

If we're playing that game: - Human muscles get energy from food. - Food is or gets its energy from plants. - Plants get energy from the Sun. - The Sun's energy comes from gravity-forced fusion. So gravity :)

Good point, but it's not the end. Fusion uses up energy put there by the Big Bang :)

Re: GravityLight: Generate light with gravity

#38

Post by fla »

Vexs wrote: post #18
jpeterson wrote: post #11

The basic idea here is actually a very old approach -- clocks have been powered this way for centuries. But it's very cool and refreshing to see a modern electrical spin on it.

Might be fun to make an electric clock that uses gravity, go full circle.

Rotor systems like in some automatic watches produce very little energy. Even at 100% efficiency it wouldn't be able to sustain an electronic circuit.

Edit: I was wrong. See below.

Re: GravityLight: Generate light with gravity

#39

Post by Confusion »

avian wrote: post #35
haxiomic wrote: post #32

Earlier quoted context omitted.

I take your point, but the food ultimately gets its energy from the sun, which gets its energy from collapsing under gravity. I don't think there's a clear place to stop, but I'd say the name Gravity Light gets the idea across anyhow

Sun is powered by fusion. Gravity just holds it together.

The fusion persists because gravity forces hydrogen sufficiently close together.

Re: GravityLight: Generate light with gravity

#40

Post by tdaltonc »

montecarl wrote: post #23

Its cool our energy problems are being solved in two directions at once. We are (slowly) making better energy storage and generation devices. At the same time many of our energy needs go down by the rapid decrease in energy needed to power the electronics. It would be cool to see a graph of the watts/lumen efficiency of light bulbs over the last 50 years and of the joules/operation of CPUs.

Manhour/lumen is the only measure I know of that captures all of the elements of economic growth and can be estimated for every culture and back to before the development of spoken language.
Post reply on HN