Comments on: Gravity powered lights, cheaper than solar

By: Yotam Ariel

Yotam Ariel — Mon, 17 Dec 2012 02:30:00 +0000

Actually, I didn’t :-)
(sorry.. well, maybe the guys will read my comment..)

By: First Last

First Last — Sat, 15 Dec 2012 10:05:00 +0000

No, I just think they’re as equally incapable of literally becoming NiMH batteries as the rest of us.

By: Michael Smith

Michael Smith — Sat, 15 Dec 2012 09:52:00 +0000

Sorry but I think thats a little bit condescending. Are the users of this device necessarily better at understanding 19th century technology than 20th century technology?

By: First Last

First Last — Sat, 15 Dec 2012 09:41:00 +0000

You’d be surprised – and more importantly, an owner/community can be taught to repair and maintain a mechanical system themselves. They can’t be taught to be batteries.

By: Itsumishi

Itsumishi — Sat, 15 Dec 2012 01:14:00 +0000

You realise this is a random Blog and isn’t actually affiliated with the project right?

By: Ito Kagehisa

Ito Kagehisa — Sat, 15 Dec 2012 00:40:00 +0000

Not necessarily; it depends on build quality. I have a thirty year old electric tractor (DC) and a 1959 table saw (AC) with the original motors; they’ve both been in constant use and still work fine. The DC motor has had several brush replacements. A good electric motor or generator will outlast any small battery by decades. If it’s brushless, even longer. And you can replace low speed motor bearings with indigenous materials – the arbor vitae bearings in big Francis turbines have been known to last a hundred years in heavy use.

Now, BIG batteries can last as long as a good electric motor, but you won’t want a half-ton iron chlorine cell in your shanty.

By: Ito Kagehisa

Ito Kagehisa — Sat, 15 Dec 2012 00:36:00 +0000

Well, for one thing NiMH batteries can’t be fixed by poor people. Neither can LEDs or solar panels, but those are both significantly more robust. But then again PV sucks hard during dust storms, and blizzards, and week-long rains; you can keep a sandbag and dynamo indoors and not have to expose yourself to harsh weather.

By: Ito Kagehisa

Ito Kagehisa — Sat, 15 Dec 2012 00:29:00 +0000

You’re made of awesome.

By: Ito Kagehisa

Ito Kagehisa — Sat, 15 Dec 2012 00:27:00 +0000

If you think a metal spring is not significantly complex and fragile compared to a sandbag, well, I deeply admire your smelting, casting, forging, and heat-treating skills. If you think a nonmetallic spring would last longer and work better than a sandbag, I have to disagree.

By: Ito Kagehisa

Ito Kagehisa — Sat, 15 Dec 2012 00:23:00 +0000

Hmm, interesting point on the mushiness. If you didn’t tune it right, it might feel like stepping in mud or sand. But I wouldn’t worry about lack of thresholds – if you can’t make something that would work with a couple of sticks and some string, you won’t be able to feed yourself anyway. Don’t assume the poor are stupid.

By: Tony Philipsson

Tony Philipsson — Fri, 14 Dec 2012 23:08:00 +0000

Nothing you can do, can get extra free energy.

There are already pulleys/gears in it.
Only thing you can do is double the weight so it will double the time/or watt as you will be doubling the gear ratio in response.
But energy put in (by lifting the bag) is the energy you get out.

By: ddh819

ddh819 — Fri, 14 Dec 2012 18:08:00 +0000

there are fans that work like this too, right?

By: Michael Crumpton

Michael Crumpton — Fri, 14 Dec 2012 02:46:00 +0000

Essentially you would be replicating an old style bike generator. If you have ever played with one of those, you would see the drag from the generator slows the wheel to a stop in less than a minute. Even if you added weights to store more power and made the generator drag half as much, it is unlikely that the light would last over a few minutes.

By: Michael Crumpton

Michael Crumpton — Fri, 14 Dec 2012 01:52:00 +0000

I would be willing to bet that you have never used one of these spring wound devices. If you had you would know how unpleasant these devices to charge. I would much rather move a 20lb weight every half hour (which would take about 5 seconds), than to endlessly crank one of those emergency flashlights, not to mention dealing with the handles breaking which has happened to both of the ones I have owned.

By: Michael Crumpton

Michael Crumpton — Fri, 14 Dec 2012 01:44:00 +0000

I was thinking a rocking chair or foot operated treadle would be a good way to incrementally lift the weight (on some kind of ratchet arrangement, assuming the supporting “cable” was a loop.

By: TripleE78

TripleE78 — Thu, 13 Dec 2012 20:17:00 +0000

Holy hell, OTR ranting about hipsters has gone national, not just local. Mind. Blown.

By: cjporkchop

cjporkchop — Thu, 13 Dec 2012 19:15:00 +0000

IIRC they mentioned a peripheral “reading light.” I assumed it would be something like the wired flashlight, to focus light on a smaller area.

By: jgs

jgs — Thu, 13 Dec 2012 19:04:00 +0000

For that matter, using a couple of pulleys you can do as you describe, with the present LED-collocated-with-dynamo unit. And that way you don’t have to run wires to extend the electrical power to where you need — just a rope to extend the mechanical power.

By: CLamb

CLamb — Thu, 13 Dec 2012 18:24:00 +0000

The generator portion can be mounted as high as a human can manage to put it. It can be hung from a tree limb 10m up or from a rock outcropping. It just requires that the LED not be co-located with the generator.

By: jgs

jgs — Thu, 13 Dec 2012 16:26:00 +0000

Two things about this: First, look at the video if you haven’t. The target “market” probably doesn’t HAVE door thresholds per se, they’ve got openings in their hut walls. Second, “no additional … exertion” isn’t strictly true. If it were, you’d have invented perpetual motion. Your “free energy” door threshold will be mushier and absorb some of the spring you’d otherwise have in your step. Whatever energy it delivers to the device, it saps from your step. I wouldn’t be surprised if people started unconsciously avoiding stepping on such a device.

By: Ito Kagehisa

Ito Kagehisa — Thu, 13 Dec 2012 16:15:00 +0000

Yes, I agree. In fact you could rig up your door thresholds so that stepping on them would pull the weight up a notch. A very simple and robust mechanical linkage would suffice. At that point, there’s no extra work being done by a human – they are walking through the doorway as an otherwise unrelated activity, and the force of gravity acting on the human body is driving the mechanism, and no additional food need be consumed or exertion made by the human to power the light.

By: jgs

jgs — Thu, 13 Dec 2012 16:11:00 +0000

I think a number of commenters are missing the point that the standard to beat here isn’t a 60W incandescent bulb, it’s a kerosene lantern. I wonder if many of them have actually tried to read by the light of such a lantern. I have. A 60W bulb, it ain’t.

Perfect is the enemy of good.

By: Diogenes

Diogenes — Thu, 13 Dec 2012 14:11:00 +0000

Who said otherwise?

By: Ray Perkins

Ray Perkins — Thu, 13 Dec 2012 12:16:00 +0000

I have an old one made of Bakelite that must be 50 years old – worked perfectly until I dropped it! My new one lasted about a year before the batteries died, so I tossed it.

By: Antinous / Moderator

Antinous / Moderator — Thu, 13 Dec 2012 09:10:00 +0000

I’m in the age group and I need more light than I used to, but nowhere near double.

Your anecdote notwithstanding, an average 50 year-old needs twice the light.

By: Justin Le

Justin Le — Thu, 13 Dec 2012 07:24:00 +0000

This is actually different from wind-up and muscle-powered. Wind-up uses mechanical potential energy stored in the chemical bonds in springs; traditional batteries use potential energy stored in chemical configurations in batteries. This light uses the potential energy stored in an object’s position in the gravitational field of the Earth. This is similar to a water turbine at a dam or a water wheel in a river.

Yes you might need to use muscle energy to “charge” the gravitational “capacitor” (which stores gravitational energy and releases it slowly the same way an electrical capacitor does), but you could charge it any way you like…with a battery-powered motor or a combustion engine if you want. Whatever form of energy (“muscle”, battery, chemical) you use to charge your gravitational capacitor eventually you are storing things in a gravity battery and using gravitational potential energy to generate power.

By: Itsumishi

Itsumishi — Thu, 13 Dec 2012 07:13:00 +0000

Did you watch the video? It addressed your statements directly

PV cells will only gather power during daylight hours, limited by cloud cover, etc and have no opportunity for recharging without sunlight. They also cost more than any part in this system. Batteries wear out, and require replacement every few years. They’re also relatively expensive.

By: Itsumishi

Itsumishi — Thu, 13 Dec 2012 07:09:00 +0000

The hemp example is terrible. Hemp used to be a cheap and well used crop. Then it was made illegal virtually everywhere, now growing hemp is highly restricted and as a result, demand outstrips supply. If hemp was perfectly legal to grow you’d expect hemp goods to be far cheaper.

By: Itsumishi

Itsumishi — Thu, 13 Dec 2012 06:59:00 +0000

Advantage: lifting something heavy for two seconds takes considerably less time than extracting the equivalent amount of energy from a wind up device.

Also:
1) Its not hard to support 10kg from above.
2) If you’re getting a back injury from lifting 10kg then you’re lifting wrong.
3) A spring is still capable of falling on you. (That point is just for giggles).

By: Diogenes

Diogenes — Thu, 13 Dec 2012 06:08:00 +0000

Maybe, but grandfather clocks have the same kind of moving parts, and they seem to run for an awfully long time.