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GravityLight: Generate light with gravity

gravitylight.org

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Re: GravityLight: Generate light with gravity

#61

Post by Gravityloss »

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.

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.

Re: GravityLight: Generate light with gravity

#62

Post by kbenson »

ris wrote: post #58

I implore people to support something far more practical like http://www.solar-aid.org/ than this. Solar lights are many times more thermodynamically efficient, cheaper to make, smaller and much more robust (no moving parts!). This "lifting weights" thing is a silly gimmick. A lifted weight stores a miniscule amount of energy compared to a battery that's been charged by the sun.

Don't both have their places? There are benefits to having a power source that is a) not dependent on a resource that is not available at all times and b) does not require a charging period.

It's sort of like people in the late 19th century saying you shouldn't support the development of automobiles, because boats are much more efficient way to move cargo. While true, it does nothing to address the fact that in some cases the use of a boat makes no sense, such as transporting to a land-locked location.

Re: GravityLight: Generate light with gravity

#63

Post by SideburnsOfDoom »

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…

> 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.

Fire stays where it's put? No. The problems with flames involve toxic gasses poisoning people and the occasional building on fire. That's really not consistent with the idea that "flame stays where its put"

Re: GravityLight: Generate light with gravity

#64

Post by ris »

kbenson wrote: post #62
ris wrote: post #58

I implore people to support something far more practical like http://www.solar-aid.org/ than this. Solar lights are many times more thermodynamically efficient, cheaper to make, smaller and much more robust (no moving parts!). This "lifting weights" thing is a silly gimmick. A lifted weight stores a miniscule amount of energy compared to a battery that's been charged by the sun.

Don't both have their places? There are benefits to having a power source that is a) not dependent on a resource that is not available at all times and b) does not require a charging period. It's sort of like people in the late 19th century saying you shouldn't support the development of automobiles, because boats are much more efficient way to move cargo. While true, it does nothing to address the fact that in some…

"Don't both have their places?"

It's more that this "invention" has been bouncing around for a while and gets an unwarranted amount of attention for the amount of energy it can provide. Weird to think, but solar isn't "sexy" in the same way.

Re: GravityLight: Generate light with gravity

#65

Post by fla »

aidenn0 wrote: post #55
fla wrote: post #38

Earlier quoted context omitted.

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.

My automatic watch contains an electronic circuit, so I'm not sure what your point is.

Interesting. What is the circuit for ?

Are you sure it's not powered by a standard watch battery ?

Re: GravityLight: Generate light with gravity

#66

Post by kbenson »

ris wrote: post #64
kbenson wrote: post #62

Earlier quoted context omitted.

Don't both have their places? There are benefits to having a power source that is a) not dependent on a resource that is not available at all times and b) does not require a charging period. It's sort of like people in the late 19th century saying you shouldn't support the development of automobiles, because boats are much more efficient way to move cargo. While true, it does nothing to address the fact that in some…

"Don't both have their places?" It's more that this "invention" has been bouncing around for a while and gets an unwarranted amount of attention for the amount of energy it can provide. Weird to think, but solar isn't "sexy" in the same way.

Maybe that "unwarranted amount of attention" is because it has a different set of requirement for use than solar which makes it particularly attractive. Considering only the energy efficiency and not how it could or would actually be used by the target consumers seems shortsighted to me. It may yield a the most efficient product, but it may not yield the most effective product.

Re: GravityLight: Generate light with gravity

#67

Post by makomk »

lyschoening wrote: post #60
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…

The key here is that this method does not require a battery. In practice though I am skeptical that this contraption would live much longer than a rechargeable battery combined with something more versatile such as a hand crank.

For comparison, that's in roughly the same ballpark as the amount of energy one of the tiny, cheap rechargable batteries in a dollar-store solar light can store. Potential energy just isn't all that viable.

Re: GravityLight: Generate light with gravity

#68

Post by mattgrice »

fla wrote: post #38
Vexs wrote: post #18

Earlier quoted context omitted.

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.

Seiko Kinetic watches are quartz watches that are powered by movement. That's 30 year old technology.

Re: GravityLight: Generate light with gravity

#70

Post by scott_s »

avian wrote: post #43
Confusion wrote: post #39

Earlier quoted context omitted.

The fusion persists because gravity forces hydrogen sufficiently close together.

By that logic my car is powered by steel, because that's what keeps the fuel-air mixture sufficiently close together.

Close, but not quite. The steel of your engine did not cause your engine to exist. But gravitational collapse of interstellar gas is the process that formed the sun. So, in that sense, gravity comes before the fusion.
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