You know when I started really getting into science? It’s when a high school chemistry teacher chucked a big chunk of the curriculum and taught us practical math instead: how to use the power of estimation to get ballpark estimates of various phenomena. It really woke me up to the power of simple arithmetic and reason.
So here’s a really good example. A couple of people have been raising money to build a gravity powered lamp Just raise a bag full of dirt and let it slowly drop, and the power generated will drive a small reading light, or can be used to recharge batteries, they claim. It’s the same principle that drove my grandparents’ cuckoo clock; every morning they’d pull a chain to raise the weights, and over the course of the day they’d slowly descend, making the whole mechanism tick.
Which immediately made me suspicious — that’s all that pound or two of counterweights did, was make a precisely designed and balanced delicate clock mechanism work. You can really get that much energy, to generate a useable amount of light, with such a trivial amount of input? And then I saw the video, where they raise the weight and the light instantly comes on brightly, with no detectable descent of the weight. This can’t be true, I thought.
But then I read this site, where they whip out the metaphorical envelope and scribble some quick calculations, that same estimation technique my high school teacher showed us how to use. Nope, can’t work. None of the numbers make any sense.
They also highlight one of the creator’s comments:
With hand-cranked devices, it might require three minutes of turning a handle for half-an-hour’s return. With this amount of effort required from the consumer, it’s often not seen as a particularly attractive trade-off. The GravityLight just needs three seconds of lifting for 30 minutes’ return.
Think about that. Somehow, a quick lift of a 10kg weight is now energetically equivalent to three minutes of hard exertion. It does not compute.
I suspect their demo unit has a nice little slot for a 9V battery. And for that they’ve received $280,000. Now that’s the kind of return from input that really violates the laws of nature.
OK, I’m going to back off on the implication of fraud. The commenters say that it would produce some minuscule amount of light; the question is whether it would be sufficient to be at all useful. It’s possible their only crime is exaggeration.
Math is telling me that 3 seconds of lifting will get less than 3 seconds of return.
You know, I’ve been having a tough job finding a job lately. Now sure, I can come up with all sorts of crazy schemes that plenty of people would fall for and probably throw lots of money at, but for some reason that just doesn’t sit so well with me. Hm, any ‘professional debunker’ positions available? ;)
Actually, I suppose that’s only half-jesting… Is it possible to make a decent living debunking fraudsters? I’m not a particularly noteworthy blogger or public speaker or anything like that, but surely there’s some sort of consultant/researcher spot somewhere…? Surely there must be some financial incentive to help me avoid a life of (moral) crime!
(Don’t worry: for now the threat of being quoted in Comic Sans is more than sufficient incentive ;) Back to hunting for a real job…)
They didn’t built it for people who can do math. They built it for people who can’t (i.e. suckers).
I try to persuade my students that math has power to grapple with reality, but too many of them prefer to try to memorize algorithms and turn cranks to get results that might be correct but don’t mean anything to anyone. Thanks for this practical example of crank-busting!
MATH! It just works!
PZ, the article you linked to indicate that 10 lux (they messed up their units) is insufficient for basic tasks. The stated goal of the project is as a replacement for kerosene lamps (the burning of which has numerous detrimental health effects), which according to this
http://evanmills.lbl.gov/pubs/pdf/offgrid-lighting.pdf
have 1 to 6 lux. This is obviously not great light, but apparently it’s sufficient.
So, using weight of 10 kg lifted a distance of 1.5 m, I calculate the output as ~80 mW over thirty minutes.
Does that sound about right?
Math is telling me that 3 seconds of lifting will get less than 3 seconds of return.
It’s not quite THAT simple–mechanical clocks work.
But you’ll never get back the full energy expended in the three seconds of lifting, during the time before the weight reaches the end of its travel.
No, math is not telling you that.
Actually, reading their blurb, they are part of the ‘deciwatt’ project, which means that the proposed project would work at an output level of 0.1 watt (see http://deciwatt.org). Which is not nearly enough light to do anything by our standards, however, in light output it is comparable to the kerosene lamp that they want to replace. So they are *not* total scammers, it’s just that they conveniently forget to mention how dim the light is.
A kerosene lamp you can put right on your workplace, using the light closeby. This contraption almost by definition needs to be up by the ceiling at say 6 feet
Some more mathemagics: light intensity declines by the square of the distance. Therefore, at the same absolute brightness, the gravity light thingy at 6 feet, with a table at a (generous) 3 feet, is 9 times dimmer at the table surface.
In short, the GravityLight works, but is too dim to work by. It will light up a room comparably to a kerosene light, though. If that’s what’s needed, the GravityLight does the job
In short: PZ, you’re wrong, it does compute.
I wonder if anyone has ever made a treadmill that’s hooked up to a generator. Sure it won’t produce much electricity but at least you could feel like you’re doing SOMETHING while you run around going no where.
It would appear to me that the basic principle is sound. I’m fairly strong, I could lift a fifty kilo weight more than a metre off the ground. If that was attached to a cable or rack and pinion mechanism, I’m sure that with the correct gearing, it could run some high intensity LEDs for an hour or so. If the system uses an alternator that does not use batteries but powers the light directly, it will be much more efficient, than those wind up torches.
A quick calculation suggests it’s bunk. For a 10 kg mass lifted 1 meter (~3 feet), the gravitational potential energy available is about 100 Joule. Released over 30 minutes and with perfect conversion to electricity, that is about 1/18th of a Watt. A typical flashlight bulb is rated at maybe 1 Watt. It would not run a flashlight bulb for 30 minutes. It might do it for 2 minutes.
One way or another, it isn’t very realistic.
A couple of years ago some people were demonstrating a gizmo that was supposed to harvest the ambient RF signals in your home or office (emissions from your wireless network, etc.) to recharge your cell phone battery. The story made it onto the CNET news web site (I think they were doing demos at CES or some such trade show.). It didn’t take much math to prove that it was totally impractical — it would take months to gather enough energy this way to charge a cell phone battery once — but some believed it anyway. Now, years later, there’s no sign of the product ever hitting the market. No surprise.
If AnthonyK is correct that it works out at 80mW over 30 minutes for 10KG it probably would work
A single standard superbright LED (not a Cree type, just your bog standard 5mm job) will draw about 30mA at around 2V so 80mW sounds like just over what’d be needed.
You’d get vastly more light from a candle though, I’m not sure it’d be enough to be useful at all. if you’ve used one of those keyring torches that have a single LED with a CR2032 coin cell, it’ll be about that effective.
Also, LEDs have a switch on voltage, below that you get nothing, above it you get light so it would appear to come on suddenly, it’s not like a filament bulb where you’ll get a dim light slowly fading up
80mW for 10kg is about right. That is sufficient power to operate two small white LEDs at a current that will yield a very long lifetime. They would be quite capable of producing light comparable to a small kerosene lamp, though it can be quite difficult to emulate a “large” source like a flame with a point source LED without incurring a lot of loss. I don’t think there is anything fake about the amount of light shown in the photos.
I tend to use spreadsheets instead of napkins, partly because I know where to find them when I want them, and partly because they travel by email better. I recently did this to try to confirm if my client’s customer understood they would need at least 72 square metres of solar array. I was afraid they had never done the napkin calcs and didn’t know the implications, but they had and they did.
One important factor that needs to be understood in the case of mechanical clocks is the miniscule amount of energy they need. Small, delicately machined pieces in a low friction situation need very little energy to move them. That’s one reason why those who repair antique clocks and watches [or make them] are rare.
From the world of ergonomics and exercise physiology: What the average human can generate with a bicycle ergometer is an output of ~100W. [for comparison, world class bicyclists can sustain `400W for a few minutes when climbing mountains] Accomplishing this burns on the order of 10 Kcal/min and because of the inefficiency of human metabolism will leave a large puddle of sweat on the floor if it is done for an hour. One may need only 1/10 that much to produce enough light with an efficient lighting system, but it’s still continuous energy production.
Compare that to the effort that it takes to lift 5 kg over your head once.
there is another aspect of the stated problem supplying in this case light to “third world” countries that is seldom thought of that is the initial cost and the maintenance costs after “purchase”.
If by some amazing engineering as in this case you could build some clockwork that could indeed generate a useable electrical output what would such a device cost to produce and maintain. They often end up the equivalent of executive office toys if they are ever built at all.
uncle frogy
Well, that quote failed.
An estimation test question I had was if you are on a ship over the deepest part of the ocean and dropped a bowling ball overboard, how long would it take to reach the bottom. There is no right answer, show your work.
That figure is a bit out of date. Cree reaches LED industry milestone with 200 lumen-per-watt LEDYou’ll have to spot them a power of two.
I think this is going off track: you skip from 80 mW to equal to small kerosene lamp without any actual calculations. My calculations, which were generous –I gave gravity 10 m/s– say 55 mW. I’m going to go and check if this isn’t bullshit, but my instincts say it is. An 80 mW laser would make one bright point of light… but spread over 4Pi str, you would illuminate nothing… you would have one bright LED that you can look at but not read by.
Right, but the intent is that they wouldn’t have to use consumables like candles, or kerosene.
….10 m/s^2, forgot the ^2.
They’re estimating the cost at under $5 per unit.
As for maintenance, yes, that’s an issue. But this isn’t a steam engine. My house is full of doodads that need no maintenance.
Basically: a dim bulb for dimbulbs.
Conceptually, a generator for this application could be quite simple. The input power is very well defined and the load is almost as well defined. The generator would probably be driven through a gear train from a shaft that turns very slowly with the falling mass. Because the load is essentially fixed, it could serve quite well as a “governor” for the system. To avoid using brushes on the generator, a rectifier would be required. Great care would be necessary to minimize the losses in the mechanical system and the rectifier. It shouldn’t be terribly difficult to achieve an operating life of 20 or 30 calendar years (assuming a few hours per day of operation).
I once designed the electronics for a generator operated by an air motor. “What if the load is reduced”, I asked. “Oh, no problem, the speed of the air motor won’t rise by much.” HA! You put in enough gas flow to generate 300 watts at 30 volts and take away the load, the system will happily try to generate 300 watts at several hundred volts. Frictional losses in the air motor become pretty much the only load. Wheeee! Then they ignored my instructions and ran a system without a load. All the little paper bits from the capacitor winding were kind of cool. They gave a very clear indication of the direction from which the blast came. Blowed up good! Blowed up real good!
The good thing about it is that it does involve lifting a considerable weight a significant distance, using many more–and stronger–arm muscles, instead of what hand-cranked lights require.
But there’s no question that it couldn’t provide much light for long, and is it really worth the expense for a light around as bright as a kerosene lamp?
Is it better than a tritium-powered light, for instance? Wouldn’t solar power and batteries, with a more substantial hbled light, be better in the end?
Glen Davidson
After reading the comments I do realize my summation was not entirely accurate. I was merely in a gleeful rush to share a rather pedestrian quip.
Meh.
I work under LED light quite a bit. Usually a single 20 ma, but one that is focused and only a few feet away. I remember visiting that same off-grid-lighting site to reference luminosity of candles and oil lamps when I was designing some multi-purpose “practicals” for live theater (Pirahna-based flicker circuits I was hoping could stand in for lanterns and similar). So I have a ballpark sense of how much battery power is necessary to produce useful work light.
I also use a hand-cranked flashlight frequently. And the downside to those is that, even with decent (and expensive) batteries, you have to crank at frequent intervals. And cranking is not very efficient use of muscle power. And that also gives me a bit of a feeling for the relative power of human sweat versus electrical energy. (Even more informative was pedaling through a couple songs at the bicycle-powered stage!)
Enough so that was my first reaction, too. “Gravity? Right. Not going to be an 80w equivalent, then!”
The issue here is not so much power densities and efficiencies, but structural and cultural. Batteries work, but they are expensive both in absolute and environmental terms. Hand-cranking isn’t useful when you are trying to work with your hands, and flashlights or task lights probably require a lot of re-arranging of the work spaces and typical habits.
That said, this described gravity light sounds fiddly, fragile, possibly noisy, and from an individual standpoint has no clear advantage over the light sources they’ve been using all their lives. So that’s going to be the hard sell — getting something like that adopted.
From the link: The goal is to provide clean, efficient light for the 1.5 billion human beings on this planet who still do not have reliable access to electricity and use kerosene-powered lamps. According to Riddiford and Reeves, the use of kerosene results in vastly higher cancer rates due to smoke inhalation, and 2.5 million burn victims due to dropped or jostled lamps every year in India alone. Not to mention the cost: 10 percent to 20 percent of a household’s income in the developing world can go to fuel for lighting.
Non-consumable and combustible light sources have clear advantages.
I’ve stayed in African houses without electricity. Kerosene provides light, fuel for cooking, and heating water for bathing and washing. People aren’t lighting their houses like we light our houses. They’re using fairly dim light that throws shadows everywhere. If this light does work, even if the light isn’t comparable to a standard LED bulb, it would be a vast improvement over kerosene or candles.
I find the weakest link in these devices isn’t the mechanics, but the battery or storage cell that it uses to hold the power at a specific voltage. I have more than several mechanical lighting devices that would work better if they had used a simpler set of capacitors and a physical switch instead of a leaky lithium button.
Yeah, they’re at the edge of mechanical energy to light conversion currently possible, but you can always make math that says something is impossible. The Ollie is ‘impossible’ until you realize it isn’t.
Don’t need to do calculations. I’m quite familiar with how much light a small kerosene lamp produces and how much light LEDs produce.
I just when off to my dungeon, selected one of the perhaps two thousand LEDs I have on hand, took it into my darkroom and lit it up with 5mA from my trusty ancient Beckman DMM. Total input power 13.9mW. At even 30mW that LED would be very unpleasant to look at directly. With the LED pointed at a white wall, I could easily read a label near the opposite wall – total distance for LED to label about 1.5 metres. Just to be very clear, that is with the light reflected off of a wall, not directly from the LED. It certainly isn’t enough light to read by comfortably for any length of time, but I could probably cook by it, especially after several minutes of adaptation.
The reason the analysis in PZ’s link comes to the wrong conclusion is that it makes a wrong assumption.
For some reason I am reminded of Trevor Baylis’s wind-up radio. Widely derided especially by potential manufacturers, it now sells by the million! Note that it uses a spring rather than a battery and, in later models, a solar panel in addition.
http://en.wikipedia.org/wiki/Trevor_Baylis
@18 naturalcynic – My dad always had antique clocks and guns in various stages of restoration. He often called me to his repair bench to show me some fiendishly clever way the clock maker had created a super-efficient mechanism so a falling weight would run the clock for a long time. (I thought it was normal for kids’ parents to do this, but now I realize I was just lucky).
I propose a generator to install on the seat under the person reading or working. A pair of self-expanding bladders and some valves would provide a steady stream of compressed air as the user shifted from butt-cheek to butt-cheek. Magnetic induction built into the fart-noise transducer would provide precious electricity which would shock a mouse in a small treadmill, causing him to run and turn a small rotary generator and charge a capacitor to light the LED lamp. Maybe I could get a Kickstarter going…
Lumens anybody? They are the unit of brightness. Shouldn’t somebody be doing the wattage -> lumens conversion?
I think the issue in the original claim that was most dubious was that somehow 3 seconds of lifting could produce the same amount of work as three minutes of cranking.
Lumens have been discussed in this thread already, but nobody’s stopping you from doing those calculations.
I doubt it, because while most of those are crap, I got one as a freebie from some company that takes just one of those batteries and will light up an entire room brightly.
The light does dim by probably 50% after about 45 minutes of use though.
But with a new battery the thing brightly lights up a whole section of our yard. Pretty amazing.
LED efficiencies are still increasing, too.
Having been through the calculations on a number of other blogs, here are my figures:
Light output for a kerosene lamp (without mantle) seems to be in the range 20 to 35 lumens (equivalent to a 2-3 watt incandescent bulb). Best figures for white LEDs range from 160 to 200 lumens per watt for devices advertised for sale, with 250 lumens per watt claimed in the laboratory (the theoretical limit is 250-300 for “white” light so this isn’t likely to go much higher).
So the lowest useful power is 80mW giving 20 lumens at 250 lumens/W; this is the most favourable number. A more realistic number is 200mW giving 36 lumens at 180 lumens/W.
10kg lifted 2 meters would generate 200mW for 16 minutes or 80mW for 41 minutes at perfect efficiency (or 12 / 30 minutes at 75%).
By comparison, a 10cm by 10cm solar panel can generate at least 10kJ to 50kJ per day depending on latitude, weather, etc. 10kJ is enough to run a 700mW light (126 to 175 lumens) for 4 hours.
How much for the battery to store the energy?
This is actually an interesting engineering problem. I have sitting here at my desk a small(1HP) permanent magnet motor that we use as a joy buzzer for the new people. It is a typical 460V unit but If you just kick the shaft you get less than 100V out of it. Typically around 10V-30V. But, more than enough to light up an LED.
Now suppose you lift a 100kG weight with a hoist system like a crank operate block and tackle. How high would you have lift it and how much could you power with it?
I wonder if I laid my hands on a 50HP PM motor if I could do better. The real trick is figuring out the mechanical side of it but, it might not be a bad idea for people that are off the grid.
According to LightingAfrica.org
http://www.lightingafrica.org/component/docman/doc_download/103-50-ways-to-end-kerosne-lighting-reep.html
(Note, pdf document).
The kersene lamp they’re trying to replace has a light output of 10 lumen.
Which is… pretty much what the article PZ linked to claim the system could generate.
Some of the geeks at candlepowerforums might be interesting to ask about this.
I’m not a scientist which is why I take “theoretical limits” with a grain of salt when it comes to tech, seeing as I can remember when 300kbps modems were the fastest available and the “theoretical limit” for transmitting binary information over standard phone lines was 900kbps.
Just a few years later my 1200kbps modem was made obsolete by the new 2400kbps modems.
Which were replaced by 4800kbps and then 5600kbps.
(when I say “since I am not a scientist” it’s not a dismissal of scientists, it’s an admission that I dunno WTF I’m talking about.)
evilDoug #17
I prefer the backs of envelopes. I’m a traditionalist.
(plus I just messed up the whole kbps thing)
Who wants to fund my kickstarter project to produce envelopes with cheap, solar-powered spreadsheets on the back of them?
@11 Alverant,
The most famous device for turning human muscle power into useful electricity was Alf Traeger’s pedal powered wireless set, invented in 1927 to allow remote stations to communicate for medical assistance with the Royal Flying Doctor Service.
http://www.samemory.sa.gov.au/site/page.cfm?u=267
It all depends on how valuable your electrical power is.
.
As for lighting, a single bright white LED is indeed able to light a room at 70mW or less, so long as you don’t want to read a fine print novel. It depends on what you are used to.
17 years ago I bought some of the first 5mm white LEDs at $$$ each, connected 2 of them to a small plug pack for lighting the basement. I don’t turn them off. They are still going, and provide just enough light to negotiate the passage. If they ever blow up I might get a new single one, it’ll be brighter and a lot cheaper!.
Plastic soda bottles become light source https://www.youtube.com/watch?v=kHTD_RX3J2I
(During the day).
Watch that video, which discusses a daytime light source and how important that is, and then consider what this solution could do for the same families.
And if one of these lamps is not enough to read with, well perhaps two. And consider generation two of these products. And generation three.
Then consider what happens to your day when you have a power outage after dark.
Over the years I’ve done numerous calculations to show that something can be done and perhaps almost as many calculations to show that something *couldn’t* be done. With Rossi’s claim of cold fusion for example, I showed how Rossi’s claims (energy produced, length of demonstration, etc) match up beautifully with firing his apparatus by burning hydrogen from a small cylinder – so it was likely that Rossi was indeed measuring heat correctly but he was lying about where that heat came from. It’s also possible that Rossi simply made up numbers which match the burning of hydrogen, but that would be one hell of a coincidence.
In addition to the outright impossible, calculations sometimes show that something *might* be possible (theoretically possible but real world interferences or state of technology may prevent the creation of a useful product) in which case you simply have to shell out the money and do the experiments. Then of course there are the “definitely possible with current technology” calculations but people still manage to cock things up and not build a usable product.
Most bike lights I’ve used have a single 0.1 watt LED (1 watt LED bulbs are called “super bright” bulbs.) This is plenty bright for most tasks and is a legitimate alternative where there is no electricity. I regularly use a single LED as the sole source of light on camping trips — and happily read by it, play cards, knit…
If it is meant for use while seated at a table they could use a treadle to power it.
The goal cost at under $5 per unit. does that include the clockwork, 2 meter high stand, wiring and leds to supply the usable light. the electronics could be SMT but the clockwork and generator would have to be sizable in comparison and more robust, precision and durable than a cheap wind up toy.
I would like to see that without some external subsidy.
uncle frogy
“If it is meant for use while seated at a table they could use a treadle to power it.”
Oddly enough I figure that Generation 4 uses a long circle of rope and a spring and does away with the stone.
Re bowling ball dropped in the deepest ocean:
Numbers all guesstimated/remembered poorly off the top of my head:
SG of a bowling ball- 1.2
Deepest ocean: 5 miles, roughly 8.5 kilometers
quick mental FBD gives downward acceleration of g(1/SG-1), or roughly .2g
kinematics: x=x0+V0x+.5at^2, which simplifies to x=.5at^2
t=sqrt(2x/a)
t=sqrt(2*85000m/1.96m/s^2)=approx sqrt(85000s^2)=approx 300 seconds.
Drag forces might have something to say about that one, though.
10 lumens is very low for any kind of lamp – a single candle can do more than that. (The traditional “standard candle” is about 12.3 lumens.)
I am a huge fan of back of the envelope calculations. But often they are only good enough to get you to within an order of magnitude or so of the truth. In this particular case there are some subtleties involved and I think that margin of error is too big to definitively refute this concept. If you look around the internet you can find many technology geeks battering each other over the head with their slide rules and coming to different conclusions about this project. My intuition suggests that by following one thread and declaring that to be definitive proof that this is a hoax PZ has made a rather embarrassing and possibly quite offensive mistake. I could be wrong but I hope not. It would be great if this is a simple and practical technology that improves lives in poor countries.
You could make this thing with a recycled stepper motor off a trashed printer, there must be millions of these going to land fill otherwise. No need to put new parts in the light system.
And a kerosene lamp would be turned down to the minimum setting, fuel being expensive, you would conserve it any way you can.
@Andrew G
The reason they’re trying to replace kerosene lamp is to remove something they have to buy over and over again to fuel (in the case of kerosene lamp, fuel).
Replacing one fuel with another arguably just as expensive fuel sort of defeat that purpose.
For how much 10 lumens helps, try a key-chain light in a pitch-black room (preferably in room without window, or rooms where you don’t get “light pollution” from street light).
@billforsternz
#57
People do make mistakes, and in truth when I first read about it my first thought is “This is bullshit.”
Funny enough, it was math (the one PZ linked to) that lead me to the conclusion of “Huh, this might work.”
One must note the GOAL of the project, which is essentially create a light source that’s at least 10 lumen bright (enough to replace kerosene lamp) for 30 minutes.
The article PZ linked to did make some bad assumptions, such as:
“Using a table of standard required illuminance levels we find that reading and writing high quaility books requires at least 500 lux.”
Project goal is to replace Kerosene lamp, which outputs just 10 lumen according to the LightingAfrica.org document I posted in comment previously. The goal is not to provide sufficient light to read books.
“While gravity lights might sound like a good idea, by doing some basic calculations we can find that they simply don’t store enough energy to be useful in real-world scenarios.”
So… being able to find your way around your own house isn’t useful?
“It is important to remember that, for equally efficient systems, there’s no shortcut for the amount of energy needed as input. If you input the energy faster, it just requires more power (shorter, more intense effort). If it takes 1/60th of the time, you will need 60 times the power.”
Perhaps the creator is referencing to the possible “fact” (someone with knowledge or study on human physiology please correct me if I’m wrong) that it’s more effort to crank a handle at high rate of speed versus lifting a heavy object once. Granted, 3 minutes of hand-cranking could probably give you a fairly bright flash-light for half an hour versus the dim ambient light the GravityLight would produce.
PZ, you might want to retract that implication of fraud at the end (the stuff about the 9V battery), because if the numerous commenters in this thread are correct, the lamp should be able to do what its makers claim it does (put out about a candle’s worth of light for about 30 minutes). It’s not right to accuse someone of fraud unless it’s quite obvious that they are pulling a scam, and based on what I’ve read, I’m not convinced this is a scam.
I’m not saying I’d give any money to these guys–I’m still not convince they’re legit. But I also don’t think any of the links you provided are sufficient proof that any fraud has taken place. In fact, the napkin-math article seems to confirm that this lamp could provide the roughly the same light as a candle.
“It is important to remember that, for equally efficient systems, there’s no shortcut for the amount of energy needed as input. If you input the energy faster, it just requires more power (shorter, more intense effort). If it takes 1/60th of the time, you will need 60 times the power.”
Perhaps the creator is referencing to the possible “fact” (someone with knowledge or study on human physiology please correct me if I’m wrong) that it’s more effort to crank a handle at high rate of speed versus lifting a heavy object once. Granted, 3 minutes of hand-cranking could probably give you a fairly bright flash-light for half an hour versus the dim ambient light the GravityLight would produce.”
The “input the energy faster” was just stupid stupid misunderstanding of what was being said.
They weren’t saying 3 seconds of lifting was some mechanical energy equivalent of 3 minutes of winding, they were saying 3 minutes of winding is boring, and no one knows what 3 minutes is anyway, but simply lifting this bag in 3 seconds, like most humans would take would replace the 3 minute boring winding.
“PZ, you might want to retract that implication of fraud at the end (the stuff about the 9V battery), because if the numerous commenters in this thread are correct, the lamp should be able to do what its makers claim it does (put out about a candle’s worth of light for about 30 minutes). It’s not right to accuse someone of fraud unless it’s quite obvious that they are pulling a scam, and based on what I’ve read, I’m not convinced this is a scam.”
PZ should not have convinced them of fraud in the first place. His analysis was poor and he relied on an intermediary site he could not vouch for, but did. Talk about hubris.
Says the guy who just dropped a load of crap in another thread, then ran off when both his numbers and reasoning were shown to be bogus?
@olivercrangle
#63
Well, people make mistake, and PZ does operate from a disadvantage here (in terms of subject matter).
1. He’s a biologist, not an engineer.
2. The site he choose as a source made several incomplete/erroneous assumption (the most important of which is what amount of light is considered “useful”).
A further pitfall is that the article did list an example of an actual fraud (that similar system can create sufficient bright light). It is natural to assume that anyone claiming similar system is committing a fraud.
Unfortunately, in this case it’s like claiming someone inventing a hand-shovel that can shovel a pot-ful of dirt in thirty minutes a fraud because someone else claimed they made a hand-shovel that can level a mountain in thirty minutes. Two completely different specification using the same idea.
I have a fairly high confidence that PZ will update this post with the needed corrections.
@carlie
I would agree the olivercrangle just want a way to jab at PZ. But I do have to say the PZ may have dropped the ball with this post.
People do make mistake.
Pah! Envelopes is for bidness types. Engineers use napkins.
Somewhere I have some Burr-Brown (an important manufacturer of analog integrated circuits, now part of Texas Instruments) napkins that are pre-printed with a grid for drawing graphs.
Or PZ will on occasion put up a post just to generate an argument against the post. In this case, a text-book example of the horde showing that the idea isn’t so far fetched, and supplying actual evidence (note OC, you never did provide evidence, ergo you’re still a fuckwitted misogynist idjit) to show concept has minimal validity.
It is not inconceivable to me that 3 seconds of heavy lifting is at least in the ballpark of 3 minutes of winding. Winding uses primarily the small fine motor skill muscles. Heavy lifting will use the back, the butt, the legs, the big powerful muscles. Big muscles v fine motor muscles suggests more than one order of magnitude. 3 minutes v 3 seconds is less than two orders of magnitude. I’d concede there is still likely a gap, but maybe not a huge enough gap to prevent generating some useful output for half an hour. That’s going to be the extent of my back of the envelope analysis, I am not qualified to be any more definitive than that.
I am also hopeful that PZ will modify his position and withdraw the accusation of fraud unless a much more substantive debunking emerges.
rickdesper #36
This wasn’t the claim. The claim was that they could produce comparable illumination. You assume that the two mechanisms are equally efficient at converting human muscle work into illumination.
Tsk. What I’m seeing here — I admit that I didn’t read all of the comments; I skipped about the last 5 — is what I’ve seen on every other forum which discusses this:
A bunch of westerners who are on the grid, claiming that this idea is bad because it can’t possibly generate the same amount of light as they are used to getting.
On the last forum I saw this discussed, someone dismissed it because, using the current “best commonly available” LEDs you could only get 20-25 lumens for that amount of power. Well, so what? A candle, as someone has pointed out already, is less than 15 — and a candle is omnidirectional, where LEDs are narrowly directional (omnidirectional LED bulbs use mirrors and lenses to spread the light out). So if we assume 20 lumens, but focussed on an area that is, oh, say a quarter of directional space that a candle covers, then we’re really talking about a task light which is as good as something like 5 candles. Switched into an omnidirectional formation, that’s still better than a single candle, possibly as good as two.
Our own ancestors, up until the advent of gas in the mid-to-late 1800s, were lucky if they were able to use 2 candles at once. It didn’t stop them from doing things after dark — including reading and household work like knitting. (And no, they didn’t go to bed immediately when the sun went down. People used to stay up until 10 and 11 at night; go read Boswell or Pepys.) We have been spoiled by gas, incandescent bulbs, fluorescence, and high-wattage LED technology. If our ancestors were around, they would think the light from this thing was amazing.
In addition to this, candles are a nuisance as a primary light source. (Cheap, low-tech manufacturing of candles, as you would be likely to get in the third world, produces candles which burn quickly and have to have their wicks trimmed to avoid guttering.) So is kerosene, which is dangerous for reasons other than smoke — a surprising number of people are burned to death by kerosene fires each year.
TL;DR version: if you think this is a waste, you have “first-world problems”.
Also: PZ, you were just belittling people who stepped out of their discipline to criticize things they didn’t understand. You’re a biologist, and this is a problem in physics and mechanics, with a little bit of sociology alongside. PZ-cian, heal thyself!
Yes, that is definitely fucking irksome. From the ‘skeptical’ link in the OP:
Thankfully, Africans and Indians must be able to echolocate, because they most certainly do basic (and even complex) tasks with only 10 lumens.
As with any calculation, whether envelope-back or Cray, garbage in, garbage out.
Before reading this thread, I poked around on the ‘tubes enough to convince myself that it really could work for the purposes specified. I am glad to see that others reached the same conclusion.
Dr. Myers and his trusted source appear to be Wrong on this, and to tag the post ‘Bad Science” and, much worse, ‘Crime‘ is unconscionably hubristic and (IANAMFL) quite possibly libelous.
(Long past experience here suggests that no apology or correction will be forthcoming; I’d love to be pleasantly surprised though.)
I have to admit that like PZ, I was initially skeptical of the claim. But, as I thought about the problem while getting the Redhead prepared for the day, the horde was responding with real data about what I was thinking. Which included going from an incandescent bulb to a highly efficient LED, which lowered the power requirements dramatically. So I see how a back-of-the-envelope calculation might seem erroneous.
@Nerd of Redhead
His intention is as what you claimed is a bit… dubious when you considered his ending statement.
“I suspect their demo unit has a nice little slot for a 9V battery. And for that they’ve received $280,000. Now that’s the kind of return from input that really violates the laws of nature.”
Plus the tag of Crime…
That would explain the ‘videogames can never be art’ post.
well didnt go to the referenced link but a gravity drop of X weight over X feet could use stepped gears to spin a bearingless flywheel for a decent period of time. Flywheel having brushes to create small amounts of elelectricity to power a small light. The mechanics would be cheap, the high end frictionless flywheel would be expensive.
“Says the guy who just dropped a load of crap in another thread, then ran off when both his numbers and reasoning were shown to be bogus?”
Says the guy who was talking to people that were spouting wrong numbers, showed no concept of reality, wrote for several hours, and then yes, had dinner, job, and life.
Now, if you want to pay me to type to you idiots all day long, THEN you can tell me how many messages I owe you.
And further, when people spend all day at these idiot fests and respond, we have people complain that someone is stalking the thread, or monopolizing it.
Run off? Read through that thread again and figure out how much time I gave to people with no intention of arguing honestly.
“I would agree the olivercrangle just want a way to jab at PZ. But I do have to say the PZ may have dropped the ball with this post.”
See, that’s illogical.
I can tell your motives with action A are bad, but I know my motives with the identical action A are good.
That way leads illogic, madness, and the hyper partisan bullshit that consumes this blog.
Of course it isn’t. We can and do impute motive based on an individual’s history, and similar, if not identical actions can have differing motives.
Having said that, and being familiar with you on this blog, I read your comments on this thread as sincere, rather than looking for a jab.
@Nerd of Redhead
Funny enough, the back-of-the-envelope calculation is correct. It’s just that the answer is mis-interpreted (kind of like how someone can grossly misinterpret fossil records as support for creationism).
In this case it’s like:
Erroneous: “10 lux has no practical purpose.”
Stated Project Goal: “10 lumen is sufficient to replace existing kerosene lamp, which has 10 lumen output.”
Plus: “10 lumen is sufficiently useful for finding your way around the house.”
Another wrong assumption the linked article is that he’s calculating illuminance based on 1 meter square area (when you read by flash-light, do you pull away the light until it covers 1 meter square, or do you keep it close enough to light the whole book?).
In the video promoting the project, they showed the ability to switch the output to a handheld flash-light. Using 10 lumen again, to achieve the 500 lux required illuminance, the light needs to be focused on about 200 square centimeter area for it to have 500 lux. Assume the area is a circle (from a flashlight, so likely to be a circle), it gives a circle with radius of 8 cm or a diameter of 16 cm.
A circle of light 16 cm across is pretty good if you want to read a book.
Damn, this project is looking pretty good.
The only misgiving I have is about the durability of the product (how long can that thing last?).
What a strange definition of illogical. I’ve never seen that one before.
Um… I think you’re talking about a static generator, which generate static by friction.
Or you’re talking about a kind of “magic trick” generator that uses the earth’s magnetic field (as oppose to a permanent magnet or a self-excitation field coil).
It would be extremely inefficient to generate power as you described.
You could also you know, leave. That would be pleasantly surprising
wtf, Ing?
That would you, the abject loser.
That was you from the get-go MRA LOSER. You had no evidence other that your poor anecdotes, making it all about YOU-YOU-YOU. We made it about reality, where your ego and intellect showed you were a fuckwitted evidenceless MRA idjit. It was never about you…..
Fixed that for you abject loser. It is never about you, but rather about reality. Get real, and lose the ego…
87 comments, and only one pointing out that this is not “math”, its physics (plus a bit of multiplication/division). As an ex-physicist, I almost feel insulted. I have no idea about power requirements for reading lights (1 Watt? 10 Watts?), but if you use power=work per second, work=force x distance, where force=mass x g (9.8m/s**2) and stick to MKS (metres, kilograms, seconds, joules, watts, etc) it’s fairly straightforward.
For 100W and 30 minutes, you would have to lift your 10 kg 1800 metres. Good workout! If you need 1Watt, lift 18 metres. If 0.2 Watts is enough, then its 3.6 metres (about 12 feet).
Lifting 10kg up one meter requires 100 Joule. 100 Joule, released over half an hour or 30*60 seconds, gives you 0.055 watt or 55 milliwatt. There are indicator LEDs with a power consumption as low as 30mW but LEDs that can be used to replace a candle typically have an efficacy of 50lm/W at 1-2 W, drive circuit loss taken into account. A candle emitting one candela gives roughly 12lm. A candle emits light uniformly in all directions. LED light can be focused.
So, if you have an LED working in the mW range with a similar efficacy as current high power LEDs, and do a good job at focusing the light, this could actually work. But how on earth do they build a generator with a sufficient efficacy?
There’s a reason for that
Doesn’t the working prototype have specs available?
I don’t think its just 1 meter, could be 2~3 meters (so that gives power output of 0.1 ~ 0.15).
Converting power from mechanical to electrical, I believe, tend to be fairly good efficiency-wise (need to find source, but for hydro-electric generation I believe it’s something along the line of >90% efficiency).
Not sure about small motors.
From my understanding, LEDs are actually more efficient at lower power. High powered LED tend to be less efficient if they need to draw more current (for LED, higher current = less efficient. Plus higher temperature = low efficiency).
@90: The reason being that you get your history of science from stick-figure cartoons? Brilliant. Every one of the statements (maybe not the first one. I have no idea or interest) in the cartoon is idiotic. Mathematics is an invaluable tool used by most scientific disciplines.
Hey everyone look at Rob Gringjanis here. He apparently wants everyone to know that he’s an idiot.
@WharGarbl
I don’t see that I suggested anywhere that candles would be a replacement. I am pointing out that even by the standards of kerosene lamps, 10 lumens is very, very small.
Rob Grigjanis
joke
/jōk/
Noun
A thing that someone says to cause amusement or laughter, esp. a story with a funny punchline.
Bloody biologists trying to do physics!
*golf clap*
@95: At least you could follow the excellent example of chigau and spell my name correctly. Idle invective is one thing, rudeness is just rude.
I’ll get right on that Rod Ringjanis
WharGarbl #83
http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=5589783&url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F5577387%2F5588047%2F05589783.pdf%3Farnumber%3D5589783
ooers! magik!
You’re a hoot, Ing.
Rob Grigjanis
bite me
—-
Ing
copy paste
Why thank you Bob Griggonis
And by “very, very small”, you mean “more or less exactly the same”. Or maybe you mean “I haven’t looked up how much light the kerosene lamps being discussed actually produce”. Either way, way to go.
There was this atempt http://www.museumofhoaxes.com/hoax/weblog/comments/gravity_lamp
Rob Grigjanis:
Oh, do fuck off, dear chap. You couldn’t even bother to use Ing’s nym, you rude assclown. Where in the hell do you get off attempting to sniffily lecture someone else? Oh, and just so you know – typos happen (I know, unthinkable!) and some people are dyslexic, so spelling can be a problem. Rather makes you out to be an idle, rude idiot who can’t be bothered to think at all.
I wonder if the author of this post (who has not earned the privilege from me for me to even bother expending the energy to mention his name) realizes that the artist of that stick figure cartoon is a mathematician, and that the punchline of most of the jokes in that cartoon are based on math?
Bloody fuckwitted idjit trying to be funny…NOT. Try shutting the fuck up to show real intelligence….
The number messages you owe us is negative. You need to go back and ERASE the last several hundred messages you’ve typed so far, or write new ones repudiating each one of those in turn.
A fund could probably be arranged to pay you for that.
Maybe even enough to make up for all that child support you so love to complain about.
Hey, I thought we were supposed to all be PZ’s sockpuppets, who never disagree with him on anything.
You mean Bilbo Gringyjeans?
Amphiox:
Oh, I’m sure the pompous puffball would bluster something along the lines of No True Mathematician. The author of said post is a special cupcake, one with smegmarmalade icing.
@108: You couldn’t even bother to use Ing’s nym, you rude assclown.
I love Rational Inquiry blogs. They’re so…rational. Funny, Ing never used my nym, sorry real name, in answering any of my comments. Does that make him a rude assclown too? Rhetorical question.
@Rob Gringjanis
Sorry I never used your real name, Rib Grogjons
I, too, have questions about longevity (I’m a little sensitive to that – many of the things I design have lifetime targets of 100 000 hours when operated continuously [and here I am, formally a biologist making a living designing industrial electronics – that’s a Rubus idaeus to you, Lachie])
This is where is would be good to pass the
envelopenapkin to an experienced mechanical engineer. Even at that, this is pretty specialized – there aren’t great numbers of mechanical devices where the power out is so low (especially relative to input torque) and efficiency is so critical. Most MEs should be able to do the calc’s, but to expect them to have a good “feel” for all of the magnitudes might be a bit much.I suspect it isn’t a great challenge to come up with a workable system that is low in cost and would deliver 20000 hours of operating life with little or no maintenance (cheap brushless DC fans will run for 10-30k hours). Anthony K might be able to comment on how many hours a day such a device would likely be used. If it ran for 6 hours a day, a 20kHr life would work out to about 9 calendar years. The electronics might be expected to last 20 years (I previously mentioned a need for a rectifier and its influence on efficiency – you don’t actually need one – two inverse-parallel connected LEDs will run happily from AC, which means the electronics amount to almost nothing).
My daughter build for a science fair at school a small wind power turbine out of an electric motor which was used in an ink jet printer, so not even a purpose build dynamo, two rechargeable batteries to store excess power and a single (red) LED.
That LED required a low amount of power and also seemed to suddenly come on when pointing the turbine into the wind.
I can totally see how a slowly descending 10kg bag of sand can keep a fly-wheel spinning fast enough for a very light dynamo to power a small LED.
Also when we think of light we think of enough of it to light a stadium.
In Africa even a very dim LED can give enough light to at least find your way to the loo in the middle of the night.
Personally, I’m joyous at seeing longtime and valued Coyote Crossing commenter Rob Grigjanis show up here. I think the horde would do well not to run him off, providing he survives the initial scarification-hazing.
Chris:
Not being such a rude ass would have helped, to say the least.
Are you kidding, Chris? I love hordes, and scarification. And I’ll accept politeness lessons from Caine any day.
If I had to pick the “rude assclown” from the last 30 comments above, it wouldn’t be this Rob guy. In fact, he wouldn’t make the top 3.
For future reference, the non-rude response to “you spelled my name wrong” is “sorry about that”.
@Chas
Except he didn’t say that. He said
As jumping on a typo because of course why not.
And yet again your reading comprehension plummets when it involves certain people here.
Ing, I apologize for jumping on a typo in response to your “He apparently wants everyone to know that he’s an idiot.”
Want to call it quits now?
>
The name to me sounds Lithuanian or Greek. As someone with such a name, I understand being tetchy about people who can’t be bothered to spell an uncommon name properly.
Once was a typo. But teasing him about it is inappropriate.
And PZ, the light may be minuscule by our standards. Think of what people are using now.
It’s not intended to be a brighter source. It’s intended to be a cheaper, safer alternative.
@Rob
There now we’ve back tracked it all the way to the prime dullard.
Why? Because someone vouched for him? Sorry I’ll lay off the golden boys. He was rude I was rude back. My fault now I guess because of reasons.
@Anthony : The name to me sounds Lithuanian or Greek
Nobody ever guesses Latvian, except, occasionally, other Latvians.
Some of our most valued long-term commenters here have been through much worse.
Rob Grigjanis:
Thanks for the ‘jumping on a typo’ apology. Welcome to the shark tank, Rob.
@Ing “Sorry I’ll lay off the golden boys”
Christ, I’m no golden boy. I can, and no doubt will, be an arsehole sometimes. I’m just not sure what you took offense at. I said it was physics, you pointed at a cartoon, I said the statements in the cartoon were idiotic. They’re especially idiotic because some scientists actually make them. What am I missing?
No, Ing, I appreciate that. He was rude about the XKCD.
And I’m guilty of the very thing I was talking about. Sorry. Bad Lithuanian here.
@Rob
Well lets see you insulted me for the cartoon missing the actual point of the cartoon and acted like an ass.
@Ing:
Wow, classy. He actually gave you a direct, formal apology, and you found a way to gratuitously insult him yet again. Congrats on actually escalating the rudeness so much that even your fellow commenters on a board which is usually fairly harsh and unwelcoming are starting to notice and call you on it. [Peter Cook Voice] That must be some sort of a record. [/Peter Cook Voice]
Yeah, okay, he’s a somewhat humorless person who felt moved to comment on a cartoon he didn’t understand, and he complained about you getting his name wrong (in a message, incidentally, which was just a massive insult from you to him — he gave you a pass on that, but you were apparently too busy thinking up new ways to be rude to notice). How terrible. It’s obviously totally okay for you to go off on him for failing to understand the point of an XKCD cartoon as though he were an MRA or a white supremacist or something. After all, people who don’t get every single XKCD are all horrible. Let’s declare war on Bill Bickel!
Lighten up. It’s one thing to scream at people who totally ignore PZ’s point, or who aren’t reading all the comments before jumping in, or who come here expecting fistbumps from dudebros for defending rohypnol, but not everything needs to be yelled at.
(And yes, I’m aware that the Usual Suspects are probably going to jump on me for daring to criticize one of them. That’s okay.)
@Ing
I apologize. I was an ass @94.
thank you. I apologize
@The Vicar : he’s a somewhat humorless person who felt moved to comment on a cartoon he didn’t understand
Hey, now that’s an insult!
@Rob
hey how about a formal truce to agree that the Vicar is an arse?
@Ing
What, out of the frying pan into the fire? Not a chance. Anyway, he/she referenced Peter Cook, so he/she can’t be a complete arse. I’ll accept the formal truce unconditionally.
Considering that the goal is to replace kerosene lamp (which isn’t that bright, as stated in the LightingAfrica.org document, around 10 lumen). The fact that they’re using it means it’s useful to them in one way or another. The project simply want to replace it with an equivalent light source that has the following advantage:
1. Cheaper (single $5 investment means no more need to purchase fuel to fuel the kerosene lamp).
2. Healthier (no carbon monoxide/noxious fume).
3. Safer (no risk of starting fire. Granted that may be replaced by risk of getting hit by a 10 kg bag).
As for usefulness of a 10 lumen light, you can actually try it out! As far as I know, most key-chain’/key-ring flashlights outputs around 10 lumen. Imagine a situation at night where you literally have no artificial light source in-door, 10 lumen light will enable you to do a lot of stuffs.
Not sure if you do camping, but if you do and camp someplace fire away from city light pollution, you’ll find that 10 lumen of light is very useful.
I whole-heartedly agree. Their Indiegogo page did mention kerosene lamp, but didn’t mention the fact that the lamp they’re replacing is fairly dim in the first place. The photograph also lend an appearance that the LED light is much brighter than it should be (10 lumen LED does look that bright if you look almost directly at it).
On the other hand, they’re trying to get funding, a bit of exaggeration is probably par for course for project like this (although they probably went… a bit overboard on that).
I use a much-lower-than 10 lumens oil lamp for my nightlight when the power is out. Of course, I have a nice, glass and steel enclosure for it and it’s in a room that’s mostly inflammable (tile and drywall) and lights the hall and toilet, an area not much smaller than the average African hut.
PZ would have impressed more, and perhaps saved himself a bit of egg on his face, if he’d dome the maths himself, to prove it’s a scam. E=mgh, P=E*F/t. m = mass = 10kg, g=9.81 as any fule kno, h=1.6. t = 1800 seconds, F = fiddle factor for efficiency, say 0.85. So 10*9.81*1.5*0.85/1800 = 0.07W to one decimal place. That’s not a lot, but a white LED has a forward voltage of about 3.5V typically, so 0.07W is 20mA through that LED. That’s way above keyfob torch level, and though I can’t compare it with the lamps currently in use, I recenly did a design with a white indicator LED running at three times that, and you can’t look directly at it in a brightly lit room, let alone at night in a village remote from light pollution, and I’ve had to cut the current by a factor of 10 to avoid lawsuits from blinded service techies.
As for the objection that you can draw the fossil fuel lamp close, but not the LED one, well it’s not at all beyond human ingenuity to put the actual LED on a couple of metres of cable, or a bit of storage in so you can do say half a dozen drops during the day with the LED off, and (allowing for battery efficiency) get two hours of light at night without a dangling weight. And all with no need to trek 50 miles to get kerosene, or pay fancy prices to some middleman.
Do the maths properly, look at the real need, which isn’t like some people’s western assumptions, and it’s a perfectly sound (though also totally non- commercial) project. Hence the need to raise money. PZ has somewhat betrayed his own principles- by not being skeptical of his own assumptions- and some of the rest of you have responded likewise- by not being skeptical of the article.
I call on PZ to withdraw, apologise, and donate to the project.
@captainahags
I think that the Bowling ball falling through water over a long distance is not approximated well by a free fall with reduced acceleration. It will reach a constant velocity very quickly. With a CW ~ 0.1, an ball with radius 10cm and much denser than water, I get 5 meters/second as the velocity. For 12 km, thats about 40 minutes.
The two scenes of African children are from this video:
http://www.youtube.com/watch?v=AmtvcJZKXrw
but don’t seem to be credited.
GravityLight’s video -> Devin Super Tramp’s video
0:45 -> 0:37
0:05 -> 0:44
First off, let’s clear one misunderstanding: what they call kerosene lamp in the lightingafrica document is just makeshift oil-lamp – a jar or tin with wick put into it. you don’t even have to put kerosene in it. Any flammable liquid is used. Expected light out of that indeed would be in the 10 lumens range. What we usually call kerosene lamp (and what lightingafrica document call “hurricane kerosene lamp”) emits more light – they give 30 lumens number, which is about right.
Now, back to the gravity lamp – my concerns would be not with the brightness (which would be low anyway and I’m not sure about efficiency, especially if we use multiple LEDs, as single LED would not be that useful taking into account that it emits rather directional light, and in the supposed setting I wouldn’t count on reflected light much), but the practicality of such device. Ten kilograms is a lot. Especially hanging it at two meters above doesn’t sound like safe and convenient arrangement. We are talkin two-three gallons here (for you Americans), hanging above your head. Not something I would like to have around children. Also you would had to have a rather solid hardpoint to hang it on, or a stable and rather sizable stand. Doesn’t sound that convienient.
Second concern would be wear. This is quite a lot of load, and whatever you use as a mechanical component, it would have to be released/rewinded at least once every half an hour. If it’s chain, it’s heavy by itself (an bulky) and not that cheap. If it’s rope, at this load wear would take the toll rather quickly. You need to replace them. And I’m not sure any rope would do, as it’s parameters would be rather important for mechanics to work correctly. Also – again – convenience matters – you have to stop whatever you are doing, rewinch the rope/chain and lift up these two gallon-sized water jars above your head. Every half and hour. To get as much light, as a small wick lamp.
Personally, I find it very improbable that gravity lamp could ever be made more practical and cost-effective than alternatives. Simple solar-panel LED light could outperform it in both convenience and cost-effect. And, most probably, also initial unit price.
A solar-panel LED light requires a solar panel, a rechargeable battery, and an LED, while this light requires only an LED and some stuff you either have around the (African) house or can get at the local store. That kind of thing can make a big difference when you live in these very remote areas and when you have no hard cash income. Would it be enough to make the lamp practicable? No idea.
Solar powered phones are already being deployed in many rural areas in Africa, so solar technology is not something unknown there.
You guys are mangling people’s names as a stupid joke? Stop that. That’s a slymepit move.
Well puppygod, you can criticise the engineering all you like, but bad engineering isn’t fraud (even if that imputation was sort-of withdrawn). Argument from personal disbelief is no better coming from skeptics than from creationists. Safety? Quality of attachment. Wear? I suppose they never thought of that one! Load bearing supports? Africans have only been constructing huts for about 25000 years, so they probably haven’t worked out how to build a strong one yet, one that will support the weight of a child (even if African children are often somewhat lighter than our own). Solar panels? The designers have probably never heard of them so didn’t consider them as an option. Like Trevor Baylis and his infamous wind-up radio.
You can legitimately criticise any given project on many grounds, but the premise of the article was that it could be shown as patently fraudulent (at least in its presentation) by a simple high- school order-of-magnitude calculation. And PZ failed to add that the answer is only correct if you have some idea of the science involved, which in this case he clearly hadn’t. His blunder is the similar to that of the infamous Dr Dionysius Lardner, who predicted that Brunel’s Atlantic- crossing steamship, the Great Western, would fail:
As the project of making the voyage directly from New York to Liverpool, it was perfectly chimerical, and they might as well talk of making the voyage from New York to the moon… 2,080 miles is the longest run that a steamer could encounter – at the end of that distance she would require a relay of coals.
The rest is History of Engineering.
OK, I’ll bite (but only the back of an envelope).
I recently bought a solar lamp from Ikea. (Link here: Sunnan) It is pretty damn cool and has got me interested in the maths of it. So I went looking and dug up some specs. (Link here.)
It consists of a small solar panel and a (triple) LED lamp that supplies well enough light to read by. And for each sold item one would be donated to a poor family without electricity.
Basically: LED draws 200mA , multiplied by voltage 3.6V gives 720 milliWatt
Then check potential energy available (say): 10kg * 9.81 m/s^2 * 2m = 196.1 J= 0.05448 Whr
So over half an hour we have: 0.10896 W
and this is about 1/7 th of what would be required (without allowing for losses).
In principle this could work, but would perhaps need more of a weight to drive it and doesn’t give much bang for buck as compared to a solar light.
Also, the human powered alternative has the advantage of being portable, contains a radio, a torch and a siren. And is cheap.
Usefull site for calculating this stuff and … well anything: WolframAlpha
@theophontes
#150
You are aware that there are many LED designs, some of which can draw very low current and still emit light (I believe some can draw as low as 2 mA and still emit light).
In short, for this purpose, there’s a negligible lower bound on the amount of current an LED need to start emitting light. So the only thing that would matter is to compute the lumen output.
Some better low power LED (those draws in the 10s of mA range) can approach 100 lumen/watt efficiency.
And as many calculated before, the current draw across a 3.5V white LED at 0.1 W is around 28 mA, more than enough current to power a low power LED.
Using 100 lumen/watt, this gives 10 lumen of illumination, which is comparable to the makeshift kerosene lamps it’s attempting to replace.
the engineering may work out that the device may work but not for $5 a piece.
there are already solar powered led lights that are take up little space and are available.
some have talked about salvaged stepper motors maybe freeish or very low cost but the labor handling them is not free neither is transportation in all points of the supply chain.
sounds like a NASA proof of concept device to me but not a $5 workable tech. a gravity powered generator sounds intriguing but a practical device for the third world bush?
how did that $100 laptop work out?
uncle frogy
Phew. Problem solved, Africans.
@ Anthony K
Radi-aid.
I would really like to expand this initiative to those poor ‘Merkins.
@ WharGarbl
You linky, me happy.
You understood this much?
(Hey, I don’t think the concept is crap, I just think it is a little “ahead of its time”(aka: “skyhooks”))
I’ve got an old space heater or two I can send to Tromso.
Hitler ate sugar.
Less snarky clarification: the name mangling and that is not what I think is the worst of slyme pit. There’s a difference between over reacting to someone over reacting to a typo and nettleing on it with intentional garbling and calling someone Rebecca Tw@tson.
theophontes, if you are questioning whether there are LEDs that will emit light at 2mA, I can assure you that there are lots of them. What they can’t do is emit very much light. Light output is more or less linear with current over a reasonably wide range.
If you want to look at a typical data sheet, search for
Cree C503B-WAN
If you want to get some idea of what sort of LEDs are available
digikey.com
is a good place to start (though rather daunting; in one subcategory they have over 15 thousand items)
A link to get you started
@149 jacksprocket
Whats your point, exactly? ’cause you spectacularly missed to make one.
I never said anything about fraud. I pointed out that I’m sceptical towards their stated goal (supplanting kerosene lamps in Africa) because of some real engineering problem which have to be solved if gravity lamp is to outperform already available alternatives (check the lightingafrica document linked by WharGarbl in 42 for some numbers – it’s very enlightening, if you excuse me unintentional pun). You just handwaved them in a ridiculous way. Why don’t you handwave problems with kerosene lamps? Cost of fuel? I suppose they never thought of that one! Smoke inhalation? Quality of ventilation. Risk of fire? Africans have only been controlling fire for about 1000000 years, so they probably haven’t worked out how to build a safe one yet. /sarcasm.
Um a kerosene lamp is a bigger fire hazard than say an LED light, it has nothing to do with being African. And there’s the idea of the cost of fuel, a renewable one would be a great boon.
Batteries a bit weak point with the solar solutions. They are expensive and don’t last forever. Looking at different ways to store an consume potential energy is a good idea, even if you think this is a stupid idea.
…And yeah, oil lamps are always going to be a fire hazard. No matter how well you build them.
@Crissa
Yeah the solution to oil lamp fire hazard was to find a replacement for them. which is what this is trying.
puppygod: fraud was the word used by PZ in the article when he partially withdrew (from this statement I think: I suspect their demo unit has a nice little slot for a 9V battery.). I didn’t handwave either the engineering problems of the LED lamp away, much less those of kerosene: I merely pointed out that such problems are likely to have been thought of already and addressed. And in many societies where weather allows it, fire has often been kept away from the house as a result of a million years’ experience.
It’s interesting (or more likely, inevitable) that evilDoug was looking at a Cree LED- I was looking at one just now, following the trail from the Farnell website- that’s a UK equivalent of DigiKey. The Cree XTE series LEDs, which are designed to operate at typically 350mA, only have a forward drop of 2.5V at low currents, which increases our current availability to 28mA for our 0.07W. At 350mA, it produces 130lm at 85C, but 149 at 25C – the temperature of the African night is hopefully closer to the latter and we are scarcely going to raise it with our feeble current. At 28mA we can already hope for 12lm, clearing the 10lm barrier, but it’s actually rather better than that, as the light output is actually slightly more efficient at low currents.
The devil in a design such as this will always be in designing in, and maintaining though operational life, enough mechanical and electrical robustness so that efficiency will not fall enough to drive output below the margin. Tough on a tight budget. The alternative may well be plains littered with decaying toxic nickel- cadmium batteries from cheap, but short-lived and dim, solar lights of the sort we can buy in pound shops.
Hey, all. Long time, no type.
I now have a new career as an international sales rep for the electronic component disti mentioned above by evilDoug. I heard an NPR story about this gravity light a few days ago and was intrigued.
I’m considering a proposal to have our in-house design team take a look at the numbers to see if it is viable. If the maths work out, it might be something that my company would be interested in sponsoring. Sure, there will be limitations to such a device. Can it be better than kerosene? It’s possible, even likely. Though IANAEE.
Looking ahead 20 years, it can’t be a bad thing for an entire generation of kids in an emerging economy to have done their homework by the light of a device that has my company’s logo on it. (They’ll get a lesson in product placement while they do their plutification tables.)
Having worked at this job for @ 2 years, I have seen customers buy parts for all kinds of crazy applications (Remote control foot warmers powered by thin lithium batteries embedded in an insole, controlled by a key fob that you can keep in your pocket.) A gravity powered light source does not seem out of the realm of possibility, considering the LED technology that has emerged over the last decade or so.
Elroy! *pouncehug of ferocity* Hey, it’s great to read you – glad to hear you’re employed and things are going well.
@theophontes (坏蛋) #155
Here’s an example of one.
http://dl.ledtronics.com/pdf/Dsdc0634.pdf
Or if you want more.
http://www.ledtronics.com/products.aspx?page=18#0,-1
Look under discrete white LED. You’ll note that many said 20 mA, that is the maximum continuous forward current allowed (the maximum current you can push through the LED continuously without burning it out). Go into the specs, you will see that many of them can be driven by as low as 2 mA.
Thanks, Caine.
Yes, life is good again. I’ve traded sawdust for electrons. Electrons are smaller, but they don’t itch as much when you get them down your shirt collar.
I look forward to reading all y’all more often now that I’m back on the grid.
yo, Elwood!
Thanks again for that thing, man. Many many hours of enjoyment.
-TAFKA Sven DiMilo
SvenChas DiMiloPeterson,
There is more where that came from. It will take some time for me to collate, concatenate, etc. We should take this OT over to the Thunderdome, though I do not have a lot of time to elaborate ATM.
@puppygod #145:
Solar has drawbacks which make it tricksy in some situations. A solar-powered light has to be charged during the day — and we’re not talking about people who live in western-style houses where they necessarily have windows to supply light indoors during the day. It also necessarily contains a bunch of components which are, again necessarily, fairly toxic to the environment to manufacture and dispose. (As far as I know, nobody has come up with a non-toxic battery yet, let alone a non-toxic rechargeable battery.)
Constructing a building so as to be sturdy enough to hang up a couple of Megagrams of weight on the wall, though, is relatively speaking very easy. And a gravity-powered light would work even if you forgot to charge it during the day (or were too ill, or the weather had been so bad you couldn’t leave the device outside, or whatever). And since it would be practically all mechanical, rather than electronic, if it broke you might even be able to fix it (or get someone in your immediate area to do so).
As for the question of longevity which has been raised repeatedly: dunno. These days, so much stuff is manufactured with no expectation of longevity that it’s kind of a toss-up. But mechanical clocks manufactured in previous centuries can, with regular maintenance, be made to work continuously. If that can’t be done with modern manufacturing, then it is a strong suggestion that — to borrow the words of Robert Benchley — our civilization has been a failure.
Of course it can be done with modern manufacturing. It can be done easily.
But the doing does require some degree of additional investment of resources. Resources which oft-times people decide they would rather not spend. Planned obsolescence as it were.
For example, those mechanical clocks made centuries ago were produced by individual skilled craftsmen. They were masterworks, essentially. (Those clocks made back then that were not at that high standard of craftsmanship, which likely did exist, obviously broke and were thrown away or had their parts recycled long ago).
Similarly produced custom craftwork today will last similarly long. But for mass produced objects, tolerances are deliberately set lower so that more can be made faster and cheaper.
For example:
http://www.nytimes.com/2012/01/03/science/in-play-off-between-old-and-new-violins-stradivarius-lags.html?_r=0
There is no discernable difference in quality between the best modern violins and the famous ancient Stradivarius.
But there are lots of mass produced modern violins around right now that are no where near that level of quality. And there would have been many (if fewer, lacking mass production) such lower tier violins during the time the Strads were made. But those older lower tier violins are not treasured or kept or maintained or saved, so we don’t have them around anymore.
@Amphiox:
As it happens, I own a long-case clock which has cheap works which were mass-produced (of this I am sure) sometime around a century ago (I believe — it certainly dates back at least 7 decades at the very minimum; there may be a date somewhere on the works but I’m not taking them apart to check). At the present moment, it is not working, but this is because the works and face were first allowed to sit unused for a decade and then stored improperly in a box in a dusty garage for about 5 years, and are now gummed up and dirty. With cleaning, it would almost certainly work again. (In fact, it technically “works” now, in the sense that the gears all mesh and the hands move properly. The dirt just makes it require more force than the weights provide, so that it stops within half an hour despite having the better part of a day’s worth of weight left.) It was working perfectly well before that, and had at least a decade of continuous operation within the last 25 years to my certain knowledge. So the tolerances for mass-produced stuff clearly aren’t an obstacle to reliable clockwork in the long term.
The question is: can modern mass-produced gears, probably made of crummy plastic using processes which have yields with 25+% defective output, if the cheap stuff you see on store shelves is any indication, hold up as well as the mass-produced metal of a century ago? That’s where the real problem lies.
Even the poorest of countries have access to a thick and steady stream of discarded cellphone batteries that are still plenty good for a 0.1W light, so battery access and cost is probably not a huge problem as long as we’re talking one or two lamps/batteries per family.
The obvious problem is that stuff has a tendency to end up in nature, or more likely, and worse, at the edge of town. But it’s not my call as a privileged westerner who’s virtually never had less than a kilowatt worth of virtually free lighting at my disposal to decide if getting a bare minimum amount of light in exchange for ground contamination is an acceptable trade. That’s for the local community to decide.
More reading and I still hold my original opinion. As a light, fine. As a mechanical contraption, could be made pretty simple (but might not be). The trick is getting it adopted. Most of the drawbacks of the existing lights are either longer-term or have been adapted to. Fire? Our family is careful, not like those families that have accidents. Cost? We have enough to get oil this week. We don’t have enough to buy a more efficient light. Long-term illness? The family is sick (and broke) NOW. And so forth. You are trying to replace something that is understood and supported with something that has unknowns. And I’m not making like the great white father here; I make exactly the same choices for exactly the same reasons all the time.
Assuming the things work over the long term, can be distributed cheaply, and can be repaired locally, I see no reason why something like this wouldn’t begin to permeate. Slowly at first.
And just because it is fun? My top-of-the-head design is to put the weight on a cord, wrap that around a drum, use a dirt-simple reduction gear to the generator. Which is spinning a permanent magnet inside a loop of wire (no brushes; the electrical end never moves). Might need to add paddles to the rotor to make a simple air-governer. No battery, no rectification — just shove AC out to the LED. Need some series resistance, probably, if the coil doesn’t have enough.
SWAG methodology says total system losses (mechanical, heat via the series resistor, etc.) are well above 90%. And, me, I’d err for a smaller weight (like, a gallon jug filled with water) lasting for a shorter time. And with luck you’d end up with a quarter to half a candle (heck — I’ve lit scenes for the stage with a candle — a candle is actually a lot of light under the right conditions!)
I think we’re missing a whole lot of information about what Africans/Indians want, would adopt, and need. I know the spiel is that, well, they’re used to kerosene lights, so why do they need something brighter? You know, except to read, learn, do homework, whatever we take for granted and what is basically necessary to really succeed in a modern economy (presumably the goal, at least long-term).
But maybe there are good enough (considering the limitations of physics) options for those who are literate and who are interested in getting their kids educated, and this is just for those who can’t or won’t read more than what can be read during daylight hours. I don’t know, though. It really won’t do to just suppose they’re going to do fine with low lighting levels, however, when, presumably, improving learning opportunities–which likely would be most easily met after dark, at least if good lighting exists–would require more than just maintaining current lighting levels.
The fact is that most significant improvements in lighting in America involved increasing lighting levels, most likely an important consideration in adopting gas, then electricity. Would just getting the same level of lighting, even if with improvements in cost and health, really be likely to be adopted? Maybe, but they might not like the white light of LEDs (I assume that for efficiency it’s cooler, rather than warmer, color), and it could be considered a nuisance to lift the weight every half hour or so, compared with a kerosene light that pretty much requires nothing after lighting, except for eventually quenching it.
It doesn’t seem like it’s going to cost too much to try marketing it, in any case, but I don’t think that we should suppose that low lighting levels are really sufficient for people who should be increasingly educated (I don’t know if those pushing this light do suppose this, of course), nor that they necessarily will prefer it for some claimed health benefits (do they mostly believe such claims, or not?), and not necessarily even for economic reasons, without any increase in lighting levels. I don’t mind anyone giving it a try, yet I wouldn’t be too sure that it’s what they either want or need.
Glen Davidson
Those hand-cranked flash lights – are they things like this one? Because that beast gives astonishing amounts of light over astonishing amounts of time for very little winding up. Over here it’s sold for approximately half of 5$. (And using it as a night-light – for internal and external application – is pretty much what I use mine for. Not reading so much, though it works for that.) Warning: do not look directly into the light!
Wouldn’t work for me if it were stationary.
Beginning to see why physicists make lots of jokes about biologists. This is just grade 12 2nd-tier science class!
10 kg (22 lbs) falling 2 metres (that’s how high a normal person can lift 10kg) generates 196.2 joules of energy, which will light a 200-watt bulb for nearly 1 whole second, or 10 1-watt LED bulbs for nearly 20 seconds but at (very) roughly 10 times the efficiency in terms of lumens of light produced, so equivalent to a 100-watt incandescent bulb for 20 seconds.
20 seconds? Hope that book has short chapters! Meanwhile, the school I went to had this stuff covered by grade 10. And we covered estimation too (physics class), but it was in the curriculum!
Worth adding that the diff. between hand-cranked weights and a coiled spring is that the the weight system provides constant force (and therefore constant power) while a spring system loses force proportionately as it unwinds.
I’ve gone a long way on the light of a single candle—once all the way across a large yard to the out-house, with the candle back in the house in a window. I’ve also heard first-hand accounts of the night vision of folks who are accustomed (American Peace Corps volunteer groping through the African night hears running footsteps, then something like, “Hi, Amy! Nice dress. Love your hair!” and more sound of running).
The developers do not emphasize how dim the light is, but I don’t see them hiding that in their vid. They maybe just realize that most folks with money to donate are not going to believe that life can be conducted in such low light. They do show that a directional light can be connected, and maybe they will build one to include in the pack for reading.
I saw this light a few weeks back, mostly because the “Gravity-Powered” bit caught my eye. It is not powered by gravity. As for hoisting the weight, I’ve experiences with both lifting and cranking, and I can sling a bag of potatoes overhead a damn lot faster than I could reel it up with a little hand crank—I have no argument with their claim that hoisting is much more efficient.
As for efficiency in the device, a smoothly descending weight has advantages over the brutal manipulation of a crank. I’d do it a little different, and I wonder how long that belt will stay smooth enough to feed properly, but again, I do not doubt it will work. I don’t think it’s going to be easy to find a clear drop for the weight, but it won’t be any worse than keeping flammables away from a lantern.
Their goal is to replace a kerosene lantern, not a floodlight.
I’ve done some work with introducing new technology into developing nations, and I see some of the same things here that we encountered. The light does what it does, and people that don’t need it won’t get one. It won’t solve everyone’s lighting problems, but I’ll bet the number of people who need one will far outnumber the supply of lights.
People in developing nations have just as much right to buy interesting gadgets as the rest of us. If the developers are flat-out lying, I’ll be first to kick their asses, but I don’t see that they are supplying a bad product. If the customers don’t test the thing … well, it isn’t that much different than the snake-oil and religion rip-offs that we already decry. And if you don’t like the looks of it, don’t donate to the project—I am not sending them money, but I don’t have any.
I see a product that looks like it will be of help to a great many people, being offered on the open market. It’s new and different, which I know confuses a lot of people, but which doesn’t make it bad or wrong. This, to me, is one of the cases where I think PZ jumped too fast, and a lot of folks followed him—it doesn’t happen often, but it disturbs me when it does.
@timanthony, #179:
How nice that you read all the other comments, and saw that the points you were raising have already been addressed, usually several times, and that the LED bulbs in this are going to be using substantially less than 1 Watt.
Oh, wait, you didn’t do that. Ing, can you come back? We have a legitimate target for your hostility now.
(Notkieran here: I can’t seem to get back in with my old account any more)
If someone has already mentioned this I apologise, but the Light Up the World foundation (link below) has been focused on replacing kerosene lamps and similar with self-powered LED lights for a very long time now. They started with foot generators and rechargeable batteries, but I think they’ve moved on.
http://lutw.org/
Silicon PV cells aren’t especially hazardous as far as I know. (CIGS thin-film may be more of a problem for disposal, but you want to recycle those for the metals. CdTe is hazardous enough to pose problems.)
And for apps of this scale, a supercap may be an adequate replacement for a battery, and those are typically made from carbon – not known for its toxicity. (Nor do they require a corrosive or toxic electrolyte.)
200w incandescent is 3600 lumens… 10 1w LED lamps is like 2000+ lumens. That’s really bright. My headlamp on my bicycle, which can throw a beam a 1/4 mile, is only 300 lumens. The standard 60w equivalent is 800 lumens. My reading lamp is significantly fewer, probably under fifty.
They’re aiming for a basic start. Something to get tasks done rather than not in pitch dark. I’d rather a lamp that worked forever than having a flame over my head.
And only Americans seem to care about the color of their light; and I find that dubious enough at the number of crappy street lamps we have that are that horrible brown tinge. That they whine about the yellow color of lamps… Ugh. My sister wishes LED lamps were shinier, because their bulbs are plastic and incandescents are glass. There’s a difference.
@ evilDoug | WharGarbl
Thanks for linkies.
@ khms
like this one Quite an amazing little device. It will also charge cellphones.
[toxic batteries]
Have a deposit on the batteries. Anything with a value will not simply be tossed.
Or as Andrew G. suggests, we could go with supercapacitor torches, that will be good for 50,000 charges.