
GravityLight: Generate light with gravity - dimitrideag
http://gravitylight.org/gravitylight
======
mabbo
There's a lot of reasons why this is cool, but I'm skeptical about it's aims
to get rid of kerosene lamps.

Kerosene lamps are made with garbage. They can be replaced in minutes if
there's a problem. Fuel costs are high, yes, but capital costs and maintenance
are low. Those matter.

To really make this a long term win, you need to make it indestructible and
easy to repair with on-hand parts. I hope they can do that.

~~~
metasean
It looks like they are trying to make them in a locally sustainable manner...

>We're doing this in our approach to distributing GravityLight

>We are partnering with local networks of people earning a living by selling
products such as GravityLight, rather than disrupting local markets and jobs
with free giveaways.

>We're doing this in our manufacturing strategy

>We aim to create jobs and skills in the regions where GravityLight will be
sold, firstly by establishing an assembly line in Kenya.

from [http://gravitylight.org/our-approach-3/](http://gravitylight.org/our-
approach-3/)

\---

And it looks like they've already run into robustness issues, but they weren't
due to cheap plastic components, and it looks like they've modified the system
to deal with them...

>GL01 had a protection mechanism that clearly indicated an overload with a red
light, and helped reduce damage to the gear teeth by allowing it to run more
swiftly, but this did not make it indestructible. An entirely novel way of
protecting the system has been designed for GL02. It will allow an overloaded
bag to descend to the ground in a safe and controlled manner, repeatedly.

>GL02 suspends the bag from a pulley, which reduces the strain on the cord and
the gearing. This also decreases the loading on the drive system and permits a
smaller gearbox ratio, which helps to improve efficiency.

from [http://gravitylight.org/coming-soon-
gl02/](http://gravitylight.org/coming-soon-gl02/)

------
ris
I implore people to support something far more practical like
[http://www.solar-aid.org/](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.

~~~
kbenson
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.

~~~
ris
"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.

~~~
scott_s
"D'oh, we forgot to charge our solar light earlier today."

"No worries, we'll just use the gravity light for now."

That scenario seems reasonable to me. The point is not the amount of energy
the technique provides. The point is the utility people get out of it. And I
see a place for both; GravityLight _and_ Solar Aid seem like great projects.

~~~
aplummer
I think they would be good in a mine safe room or something, no need to ever
replace batteries right. There are a bunch of cases you might not have a
charged light.

------
achr2
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 would require raising that weight well over 127 times.

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

~~~
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.

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manveru
Here's what people said about it 3 years ago:
[https://news.ycombinator.com/item?id=4889266](https://news.ycombinator.com/item?id=4889266)

~~~
scribscrob
It's amazing the amount of people who immediately cry hoax. Someone raised a
good point about taking money from locals and bringing it to
Europe/America/China, but clearly this isn't breaking the law of physics.

~~~
blacksmith_tb
The original OLPC attempted to ship a pull-cord generator. Trevor Bayliss, of
Freeplay radio fame, proposed a generator based on hoisting a weight on a
branch of a tree. The principle is sound. As for taking money from locals, I
would be surprised if kerosene was produced locally... and even if it was,
this is a one-time expense, versus an ongoing outlay.

~~~
eggie
I worked at OLPC. We didn't ship any kinetic charging systems as the most
reliable ones had a mean time to failure on the order of ~three full charges.
The scheme was cute and captured the imagination of people in the developed
west but is fundamentally unsound due to the cost of high precision, reliable
manual chargers and their miniscule power output. In addition to yielding only
several full charges before the $50 charging unit failed, each charge would
require tens of thousands of revolutions of a hand crank. As wonderful as the
laptop was I think it would be a very strange thing for a child to do when
they could easily play with something more immediate.

In practice most of the laptops are charged like other laptops--- from
national power grids. Those that aren't are charged from diesel generators and
solar power.

------
montecarl
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.

~~~
tdaltonc
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.

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

~~~
mdturnerphys
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 :)

~~~
dear
So by your logic fossil fuel is solar energy.

~~~
benihana
It is. Except for geothermal energy brought on by radioactive decay, all
energy on earth originally comes from the sun. Fossil fuel is sunlight that
was absorbed by plants which then either decomposed into fuel over millions of
years, or were eaten by animals which later decomposed into fuel over millions
of years. Our cars are powered by very old, stored sunlight.

~~~
zebra
And radioactive elements come from long dead suns, so all energy on earth
originally comes from A sun.

~~~
CodeWriter23
You are now qualified to take a job as an oil company or nuclear energy
lobbyist.

------
jpeterson
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.

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

~~~
fla
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.

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

~~~
fla
I stand corrected

------
biot
Perhaps a bit of a novelty given the rechargeable battery argument others have
mentioned. I imagine distributing a bunch of these with batteries and having a
central dynamo-powered recharging station that gets shared throughout a
community would be even more practical.

The first thing that came to mind when I saw that it lasts 20 minutes would be
to use it as a pomodoro timer. Code for 20 minutes, then be forced to take a
break, stand up, lift the weight, etc. You get a micro-workout as a small
bonus. Again, it's a novelty but sort of a cool one at that.

------
jackdawjack
I was rather hoping this would be a hawking radiation method, i.e. actually
generating light using gravity

~~~
chinpokomon
You and I both. This isn't even carbon neutral. I mean technically this is
burning carbon molecules.

~~~
Vendan
burning carbon molecules sourced from photosynthesis. Carbon positive, but the
fuel generation is carbon negative, so it balances out.

------
Orinocco
Loads of great social tech ideas including this one on Social Tech Guide
([http://socialtech.org.uk/](http://socialtech.org.uk/)), nominations are open
for new ones at the moment if you come across any more..

~~~
carapace
Why downvote this? Seems legit.

------
brannon
A 12kg weight hanging 6 feet in the air seems a little dangerous to me.
Definitely less dangerous than a kerosene lamp, but I'd be worried about
poorly attached weights falling if someone bumps their head on it.

~~~
ricardobeat
Do you own a TV? It's certainly way more dangerous than that.

------
bcg1
This is wonderful. I plan to buy at least one for emergencies, and also to
help make them cheaper for others.

~~~
IshKebab
A battery powered LED torch is far superior for emergencies. The only reason
you'd really want to use this is if you _really_ can't afford a solar-
rechargable battery. (But for some reason can afford this, which I'd expect to
be more expensive.)

~~~
giarc
Although that might be true, battery powered flashlights/torches suffer from
the problem of leaky batteries. I've tried to use many flashlights that don't
work, only to find the batteries have started to leak acid and ruined the
flashlight. Sure, one should check the batteries every year or so, but who
really does that? I'm not saying the gravitylight is a good replacement, just
that battery powered flashlights do have some drawbacks.

~~~
libria
This is what lithium primaries are for; they don't leak.

~~~
Vexs
And before anyone jumps in and says "lithium batteries self discharge!" Yes,
yes they do. But it's really, really small. It discharges quickly initially,
but then tapers off to about 1% per month.

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dnautics
12kg * 10 m/s^2 * 1 m = 120j. Best 100 w equivalent led is 18 watts, 120j/18w
< 10s. Let's say optimistically a next gen led gets 10x efficiency (this might
violate laws of physics), you're buying one minute of good light per 1 m lift.

------
electic
For those interested on exactly how to set one up and how it works, there is a
great Vimeo video outlining installation and operation:

[https://vimeo.com/128802766](https://vimeo.com/128802766)

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nirai
what is the deep difference between this mechanism and a simple spring / coil?

~~~
yconst
Precisely the same question I have as well. Especially given that the energy
you could store in a spring or coil could be much more, and you are not
limited by one's lifting capacity or maximum height. Anyone have an idea?

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hanoz
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 decent battery plus solar
doesn't knock this into a cocked hat.

~~~
beardicus
> 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

This says nothing of light output. If you want light, and most of kerosene's
output is heat, your energy calculation is not helpful.

> 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

This seems like an incredibly contrived "problem". What's the liability?
Somebody may bump into a somewhat heavy object that is moving downwards at a
barely perceptible clip? Somebody may tweak their back lifting the weight?
That seems lower risk than my housing burning down with me in it.

~~~
hanoz
Okay, okay, you are right of course, the light efficiency is very different,
although the heat may not be an altogether unwanted by-product in many cases.
There are also more efficient ways of getting light from petroleum than
sticking a wick in it. But if you do want the benefits of LEDs, there are
better ways of getting the energy than lifting sacks to the ceiling. It's
still 180 meters for a pair of AA rechargeables.

I genuinely don't think the hazards are at all contrived, and range from the
grave if unlikely to the mild but virtually certain. You are surely going to
knock your head on this massive hovering, albeit reasonably well lit, object
on a regular basis, and it might not be as soft and rounded as the
illustration. On the floor, in dark mode, you'll be tripping over it, which
doesn't always end comically. Reasonable precautions not withstanding it's not
impossible that it could crush or smother something beneath it even at its
snail's pace, but more likely it could come down hard through overloading,
wear or misuse. It's really not something I'd want in a family home.

It is a nice idea and obviously of the very best intentions but I'm afraid
it's simply misguided and efforts would be far better directed towards battery
plus solar. Sorry.

~~~
prewett
I would say the hazards of this device sure beat the hazards of kerosene lamps
(fire, mostly). [1] lists a series of accidents with kerosene lamps in a three
year period in a small town. I think a horse kicking over a kerosene lantern
started one of the big Chicago fires. There's even a possibility that a
kerosene lamp caused a deadly fire in modern USA [2]. And I'm guessing that
fire would be a serious problem in small, dense areas such as the slums (not
intended pejoratively) in the third world nations that are likely to have the
most use for this.

Solar plus battery might be better than this, but this looks like a whole lot
better than a kerosene lamp.

[1]
[http://www.thelampworks.com/lw_lamp_accidents.htm](http://www.thelampworks.com/lw_lamp_accidents.htm)

[2] [http://www.chicoer.com/20120322/kerosene-lamp-may-have-
cause...](http://www.chicoer.com/20120322/kerosene-lamp-may-have-caused-
deadly-browns-valley-fire)

------
userbinator
It looks quite a bit more plausible than the specs in
[http://www.howtospotapsychopath.com/2008/03/03/stop-press-
pi...](http://www.howtospotapsychopath.com/2008/03/03/stop-press-pixie-dust-
unsuitable-for-household-lighting/) , but based on my experience with things
like shake/crank torches, the light output would have to be really low to last
as long as they claim it does.

------
mhb
Doing Good Better -
[http://marginalrevolution.com/marginalrevolution/2015/07/doi...](http://marginalrevolution.com/marginalrevolution/2015/07/doing-
good-better.html)

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jheriko
these look interesting... but like all things like this i wonder what the
actual costs are of lifting the weight is?

