back to article Brit inventors' GRAVITY POWERED LIGHT ships out after just 1 year

The British-designed Deciwatt gravity-powered lamp is now in production and shipping, a year after the project went public. It was conceived by Martin Riddiford and Jim Reeves of industrial design outfit Therefore, which is best known for clever mechanical designs including the Psion computer keyboard. Therefore invited The …

COMMENTS

This topic is closed for new posts.
  1. James Hughes 1

    Some while back I did wonder whether lifting up big weights is a useful energy storage mechanism - for example, use solar/wind while its there to lift a bloody great bit block of concrete, then use the potential energy during the night. But the weight you need to lift to get any decent storage is much too large to make it useful.

    Ok at this small scale where you are powering low power LED's, not so good as a general purpose storage mechanism. Shame really.

    1. Martijn Otto

      That's already being done actually, with water: Pumped-storage hydroelectricity.

      1. Paul Hovnanian Silver badge

        For pumped storage, you need water. Even though you can pump it back up, there will be system losses. Water is scarce in many third world countries. Rocks are plentiful.

        1. Anonymous Coward
          Anonymous Coward

          "For pumped storage, you need water. Even though you can pump it back up, there will be system losses. Water is scarce in many third world countries. Rocks are plentiful."

          That really wasn't the point of the the OP !

      2. Wzrd1

        My Cuckoo clock has been doing this very thing for decades.

        Well, save for generating electricity, but adding that function in would be trivial.

        Extra! Extra! Read all about it! Clockwork reinvented!

    2. stu 4

      Hydro in scotland

      "Some while back I did wonder whether lifting up big weights is a useful energy storage mechanism - for example, use solar/wind while its there to lift a bloody great bit block of concrete, then use the potential energy during the night. But the weight you need to lift to get any decent storage is much too large to make it useful."

      Several hydro powers in scotland do exactly that - Cruachan for example as covered by El Reg:

      http://www.theregister.co.uk/2013/07/23/reg_man_delves_deep_to_find_the_power/

    3. Annihilator
      Boffin

      They do

      Pumped-storage hydroeletric does pretty much what you say - they pump water up into a higher reservoir during low-demand periods, and release it on demand or during peak periods. There are at least two that I know of in the UK (one in Scotland, one in Wales) and act as Grid reserves

      http://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity

    4. kmac499

      Hydraulic accumulators

      In days gone by one relatively small central steam engine would puff away forcing water into a vertical hydraulic ram with a huge (several tons ) weight on top of it. The stored potential energy could then be released far quicker in bursts to operate such things as hotel lifts ( London Hydraulic Power company) or dockside cranes..

      1. James Hughes 1

        Re: Hydraulic accumulators

        Yes, aware of the hydro schemes, I was wondering really how small they could get and still be useful. The answer is not very.

        And thanks for the hydraulic accumulator stuff- IIRC this is what William Armstrong (of Cragside and hydroelectricity invented - nice link up there)- that's a good biography for those interested in that sort of thing.

      2. Suricou Raven

        Re: Hydraulic accumulators

        Think bigger.

        Tower bridge.

        It's run off a modern electric pump system now, of course. But before that, it was lifted by exactly the mechanism you describe. There's a museum near one end where they still have the equipment on display.

  2. James 51 Silver badge

    Am I the only person who saw this and thought mobile/night light for the kids?

    The psion keyboard, particularly in the 5mx was very clever. Nice to see this one working out.

    1. Robert Ramsay

      I saw it and read "Gravity powered light ships" which is WAY more exciting.

      1. Michael Habel Silver badge
        Alien

        I read [it] the exact same way... And, here I was hoping to get my Ticket from Virgin Galactic to take me to Alpha Centauri. I wanted to check up on some of those Galactic Council planing orders... Just in case!

  3. Vladimir Plouzhnikov

    Reinvented cuckoo clock

    And "a proprietary electricity-generating device"

    Aka "dynamo" :-)

    1. gazthejourno (Written by Reg staff)

      Re: Reinvented cuckoo clock

      It almost definitely is, but without knowing for sure it's a bit presumptuous for us to say so.

    2. Anonymous Coward
      Anonymous Coward

      Re: Reinvented cuckoo clock

      Clearly there will be a spinning magnet of some sort in a coil of some sort, but I suspect that the "proprietary" word will actually refer to the method by which the mechanics work to stop the weight plummeting to the ground and to compensate for different weights hung from the device, while still producing the same output voltage.

      1. Anonymous Coward
        Anonymous Coward

        Re: Reinvented cuckoo clock

        The "proprietary" word probably refers to a governor which have been around in one form or another for at least 250 years in the west and perhaps even longer in China.

    3. VeganVegan

      Re: Reinvented cuckoo clock

      My thoughts exactly.

      I wonder why they went for the descending weight method, versus a coiled spring that you crank to tighten up, like the old fashion wound-up clocks (& toys). With a mechanical regulator, the dynamo could be spun at a reasonably constant speed to generate juice.

      1. John Brown (no body) Silver badge

        Re: Reinvented cuckoo clock

        "I wonder why they went for the descending weight method, versus a coiled spring"

        I suspect because you can just lift the weight up and re-attach it in a fe seconds rather than spending 10minutes winding a spring backup. Also, both the weight/bag and the rope are easily replaced. A heavy duty coiled steel spring not so much.

        1. Don Jefe
          Boffin

          Re: Reinvented cuckoo clock

          Springs are expensive in production environments.

          Not just the springs themselves, but you've got to have at least two attachment points which means molded parts or drilled holes and they are probably the most difficult parts to deal with on a production line.

          Throughput can decrease 5x per unit easily if the spring is very small or has any sort of force. A one pound coil spring is an absolute bear to deal with. The only workarounds are custom spring setting devices but that means at least one person loading the device or ordering prebuilt custom sub-assemblies. So at a minimum you've doubled the labor required as well as taken on tooling costs and line speed is still slow or your parts cost has just skyrocketed.

          If springs can be avoided in production it is usually best to do so. Especially in cost sensitive products.

    4. Intractable Potsherd Silver badge

      Re: Reinvented cuckoo clock

      Well, the belt and hook look "proprietary". When either break - which the belt will, sooner or later - it isn't going to be easy to cobble something together from stuff easily found in the places that form the market for the gadget. The tolerances (hole centres, thickness of belt) and materials performance (deformation etc) appear to be important. It isn't obvious how the belt would be changed in the field, either. I hate to be cynical about this, but it looks as if the manufacturers have made sure there will be a steady revenue for spare-parts.

      1. imanidiot Silver badge

        Re: Reinvented cuckoo clock

        This was my thought as well. Why not just use a standard timing belt? Cheap, mass produced, made to take a beating, available everywhere, and you could use an old worn one that can no longer do service in a car.

      2. Don Jefe

        Re: Reinvented cuckoo clock

        There's less than zero money to be made in spare parts for a unit that sells for $10. It would actually be cheaper to give them a complete replacement unit than deal with scalable spares.

        If you're dependent on parts for profit it means you have to stock not just parts for production but parts for spares as well, it's a second business. While not quite doubling, you're adding at least a 30% cost to your overhead as well as the costs of logistics and warehouse personnel. The spares inventory has a far higher value because it can't be used in production but you've already paid for it so its very existence costs money. On top of that the costs of shipping the part would exceed the price of the complete unit.

        You can do OK on parts and subassemblies for expensive and complex systems, like cars, that have high volumes of production so inventory doesn't get as stale. But with cheap products, like this lamp, the costs of spare parts are higher than the complete unit. It simply doesn't make any sense to do spares on an item like this.

  4. a well wisher
    Thumb Up

    What a brilliant idea ....

    Truly a 'lightbulb' moment !

  5. alain williams Silver badge

    Brilliant appropriate technology

    I hope that they do well.

  6. Andy The Hat Silver badge

    Stupid question but how does the power storage and delivery compare to whats-his-thingies clockwork stuff?

    1. Steve Evans

      Very little I would guess except for the energy storage and recharge method.

      Once the energy is "stored" either in a coiled spring or a weight high off the ground, its release will be governed by a few gears and a governor wheel (basically a gear with big fins on it). Couple this regulated rotational speed to a dynamo and you have power until the stored energy runs out.

      To my mind it's not exactly innovative, in fact it's verging on the Apple level of obvious, but hey, if nobody else has built one, good luck to them.

      I'm sure they'd be able to get dozens of patents from the US patent office.

      1. Anonymous Coward
        Anonymous Coward

        I doubt it would be governed by a spinning fan type of govenor as it will be quite wasteful of energy and wouldn't react to different weights. Were I to design this I'd use something like a torque converter.

        1. John Sturdy
          Boffin

          or regulate it electronically?

          Might it be possible to regulate the mechanical resistance of the dynamo by adjusting the electrical load attached to it (like is done for regenerative braking)?

        2. Paul Hovnanian Silver badge

          "Were I to design this I'd use something like a torque converter."

          Better yet, a DC to DC voltage converter. You tweak the conversion ratio to keep the generator running at a peak efficiency point while providing constant output current (to an LED array) or constant voltage (to charge a battery). The firmware, once developed, is much cheaper per unit than knocking off copies of a mechanical device. The microcontrollers can be had for pennies apiece.

      2. Kevin McMurtrie Silver badge

        Electronic governor

        Spring powered devices have been around for years and there's no mechanical governor wasting energy. A switching power supply is used with an inverted feedback loop. When there's too much output power, the switching power supply increases the output more. This burdens the spring/weight so that it slows down and produces less energy. When the output is low, it decreases the load and the spring/weight speeds up. Of course it's not very stable but one more layer of power conditioning is trivial when you're in the milliwatt range.

  7. kmac499

    Brilliant ...

    I look foward to a suspended scheme, like for coffee.. Quite appopriate really considering the basic pinciple of a suspended weight...

    If one of these enables a kid to read and learn after hours it's worth every penny..

  8. Anonymous Coward
    Anonymous Coward

    Nice try

    Although I'm sceptical about the balance of cost, input and output. Even with LED's, 0.1W doesn't go far, and I can see people deciding that 13c a day is an acceptable price for light rather than have the lights keep going out every twenty minutes.

    We already have LED torches that already claim to deliver 1W for 20 minutes from one minute winding a tiny crank, and in some cases integrating a small PV panel. Admittedly that's sixy seconds effort, not the three seconds to lift the weight, on the other hand it's ten times the light output. I can't help thinking that a better solution would be something the size of a gas lantern, using the wind up torch tech scaled up with a larger crank and capacitors, so giving perhaps an hours light at 1W from one to two minutes of winding. Smaller, more portable, closer in form and function to the lights they are intended to replace.

    1. Anonymous Coward
      Anonymous Coward

      Re: Nice try

      The deluxe version powers a light bulb all night. It comes with a really long rope and you hoist it up to a pole sticking out of the top of your roof.

      The non eye-sore version comes with a really long rope with a bucket onthe end. You dangle it down a well. If you need less power, butto last longer, you use the bucket only half full.

      :)

      1. Martin Budden

        Re: Nice try

        There should also be a hammock version: your own weight powers a light for you to read your bed-time story.

    2. Anonymous Coward
      Anonymous Coward

      Re: Nice try

      13c a day is a lot of money when you live on $1-2 a day.

      1. Anonymous Coward
        Anonymous Coward

        Re: Nice try

        "13c a day is a lot of money when you live on $1-2 a day."

        Yes, but it's a two year cash pay back, and when money's short the discount rate rises disproportionately. That won't be how the target market express it, but it's the same principle that sees poor people paying 1,000% APR on payday loans in this country, or higher rates to loan sharks around the world.

        That's why the inventors discuss lease type schemes, but the harsh reality is that this is too expensive for what will be a pitifully low light output. Many of the prospective users will also be buying kersoene for cooking, so why buy a one candle power device that you have to fart around with every twenty minutes when you've still got to buy kersene, you've already invested in a kersoene lamp that gives better light for longer, and the time value of the money means more like a three to four year pay-back?

        If you look at energy efficiency schemes in the UK, people are hugely reluctant to invest in things that save them money, even when they do pay back. Take GU10 halogen bulbs - in a well used room replacing these with LEDs will give you a payback of about one to two years. Despite the fact that nobody is offering savers a 50-100% interest rate, most people are still buying and using halogens. Or look at the humungous flop that Green Deal has been. Even the health and safety benefits are of little appeal. In the developed countries the benefits seem logical and obvious. But in countries with high infant mortality, non-existent health care, roads like something out of Death Race 2000, and subsistence living subject to famine (ignoring unrest and civil wars), the H&S benefits of an LED lamp over a kersosene lamp count for nothing.

        The problem here, is that the device offers inferior performance to that which it is supposed to replace, and requires a significant investment. Innovation has to do things better or cheaper, or both, and I'm afraid I don't think the inventors set their sights high enough. Everybody would like this to be cheap and effective, in reality it is neither, and the sum that gives a net benefit only works when you aren't seeing things from the perspective of the intended users.

        1. Alan_Peery

          Waiting for much brighter LEDs

          I keep buying halogens because I want the lumens, even though it's clear the LED path would pay off quite nicely.

          Any tips on where to buy GU10 LEDs that are dimmer capable *and* of roughly similar light output to the halogens?

          1. Chemist

            Re: Waiting for much brighter LEDs

            Any tips on where to buy GU10 LEDs that are dimmer capable *and* of roughly similar light output to the halogens?

            Try http://www.ultraleds.co.uk/

          2. Dan Paul

            Re: Waiting for much brighter LEDs

            Like here?

            http://catalog.gelighting.com/lamp/led-lamps/led-energy-smart-directional/f=led-energy-smart-gu10-dimmable

        2. Anonymous Coward
          Anonymous Coward

          Re: Nice try

          It's a 2 MONTH payback period. 2 Years was the nice round number quoted which gives you $100 -- which is also a nice number, but far higher than the actual $10 cost quoted.

          I agree that part of the article was poorly conceived.

  9. Hairy Spod

    interesting but...

    This looks like a good idea and I'm sure that there must be one, but could someone please tell me what's the advantage of this over existing wind up devices is?

    1. Paul Hovnanian Silver badge

      Re: interesting but...

      Hand cranked generators typically require (almost) continuous low level work input. This scheme requires an occasional high level work input and no attention between times. Wind up devices fall between these two cases.

  10. Chris Miller

    Clever use of technology, which is what developing countries really need. There's a company in our village that uses solar to charge off-the-shelf battery systems. With some clever monitoring and computer systems, they get enough power to light a small village (allowing kids to study at night, without using kerosene lamps that cause huge numbers of fires) and run a fridge to keep vaccines cool. If battery power runs low, the computers dim/turn off the lights to keep the fridge running. They go round installing these kits in remote African villages - real genius.

  11. JDX Gold badge

    Charging phones/radios

    I'm confused how 0.1W is any use for charging anything?

    Otherwise it's a neat idea although even for lighting 0.1W seems very low indeed... what is a very efficient .1W buld equivalent to in old-fashioned bulbage?

    If 20lb is a problem to lift, a simple block & tackle would be a low-tech solution.

    1. Anonymous Coward
      Anonymous Coward

      Re: Charging phones/radios

      "what is a very efficient .1W buld equivalent to in old-fashioned bulbage?"

      For a good LED the bulb is about 4-5x more efficient than a halogen bulb (eg for a GU10 you're talking about a 5W bulb being equivalent to a 35W halogen). Then a halogen bulb rated for 1,000 hours will be about thirty per cent better than a simple incandescent filament, so say 6x all in. So from that comparison we're talking about 0.1W LED being equivalent to say 0.6W in old money.

      Another way of looking at it is to consider that you'd get about 10-15 lumens from a DC 0.1W LED light. A traditional 60W bulb gives 800 lumens, which (on a linear basis) implies a similar half to one watt.

      Put in more obvious terms, we're talking about one candle power of illumination.

    2. Chemist

      Re: Charging phones/radios

      "what is a very efficient .1W buld equivalent to in old-fashioned bulbage?"

      ~~1W - I've just replaced 300W of QH lighting with 27W worth of LEDs.

    3. moiety

      Re: Charging phones/radios

      The version for the US market will -of course- have a powerful electric motor to lift the weight for you.

      :)

  12. Anomalous Cowshed

    What happened...

    What happened to those hand-cranked or hand-squeezed torches?

    They cost far less than this - indeed they were being given away as promotional gifts by companies - are far less cumbersome, and the way I see it, could achieve much the same outcome, if not better, with less hassle and outlay. I used to have one myself.

    Wouldn't something like that be more convenient than this latest amazing contraption with its secret converter of potential energy into electric energy? And why isn't it in widespread use / or is it?

    1. Anonymous Coward
      Anonymous Coward

      Re: What happened...

      They may cost less, but they have poor quality plastic gears which break all the time. They are novelties really and require quite a bit of work to get them going, with this you hook up a weight and that's it. With had cranked torches it's 20mins of cranking to get a reasonable amount of charge.

      1. Alan_Peery

        Re: What happened...

        And your hands are immediately free other tasks. Food preparation, writing and study, holding cards, or whatever.

        On a social/anthropological note: Many of the places where this light would be most needed are still strongly separated along gender lines. You *might* see an effect where the males of the household consider hand cranked torches to be "womens work" and refuse to participate, but be willing to lift the weight bags.

  13. Anonymous Coward
    Anonymous Coward

    It's not gravity powered !

    It's a potential energy storage mechanism. Yer canne break the laws of thermodynamics, captain.

    1. Destroy All Monsters Silver badge
      Trollface

      Re: It's not gravity powered !

      ANd Larry Niven invented the "Gravity Drag" anyway - potential energy being transformed into heat in a magic device that gives a f*ck about the equivalence principle, thus allowing a spaceship to settle down lightly (which disturbingly would be like making it "massy but not light")

      1. Anonymous Coward
        Anonymous Coward

        Re: It's not gravity powered !

        DAM

        WTF are you rambling about ?

  14. Captain Scarlet Silver badge
    Paris Hilton

    wow thats actually a good idea

    If I had no power though I can't imagine lifting something heavy in the dark would be advisable, but then again I could get candles and burn my house down.

  15. Anonymous John

    Damn!

    I initially misread the headline and wondered when I would be able to travel on a gravity powered light ship.

  16. Zot

    It would be nice if you could put it on a wall.

    With that rounded back it looks like it has to be hung in a room, but the light is on one side. I don't like the design, but I wish them luck with the trial

  17. Pen-y-gors Silver badge

    Interesting idea

    Could it be adapted to have a small amount of battery storage so that instead of having to lift the weight every half hour the owner could just pull hard/turn a handle for five minutes to generate enough power to run several LEDs for several hours at a time? Would that increase the cost too much? And tack on a small solar panel to charge the battery during the day?

    Or is that all getting too complicated?

    1. armyknife

      Re: Interesting idea

      I think lifting a small weight occasionally is less 'effort' than winding something for 5 minutes.

      1. Anonymous Coward
        Anonymous Coward

        Re: Interesting idea

        "I think lifting a small weight occasionally is less 'effort' than winding something for 5 minutes."

        For the same energy ~=

        1. MrXavia

          Re: Interesting idea

          maybe the more obvious thing is that winding is an inefficient method of generating electricity from human movement... lifting a weight is more efficient and faster, seconds not minutes.

          The best idea would be a pedal generator, but costs would be higher, even if it did generate more power...

          Actually I would love a small under desk set of pedals that I could use during the day to generate power, I expect I could probably generate enough power to keep my whole system running during normal usage...

          my whole system drains less than 100 watts due to the highly efficient LED monitors and power saving modes.

        2. Piro

          Re: Interesting idea

          Of course, but when talking about human effort, energy calculations have nothing to do with it.

          Would you rather have sexual intercourse for 20 minutes or jog for 15?

  18. Anonymous Coward
    Anonymous Coward

    Stairs payback

    Every time i go down stairs I smart at the energy wasted, potential for work lost.

    Have an energy recovery platform on a fireman's pole, save wear on joints and keep the lights on.

    On steep hills build a vehicle braking system in that either generates energy at the time or lifts weight for later energy recovery and use.

    Would make Porlock self sufficient and reduce the smell of brake linings.

    1. Sonny Jim

      Re: Stairs payback

      As someone who used to live at the bottom of said hill, I wholeheartedly concur. Nothing quite like waking up to the smell of roasted coffee and burnt brakes :-)

    2. Don Jefe
      Joke

      Re: Stairs payback

      If you're that concerned about lost energy just throw yourself down the stairs. You too can take advantage of gravity.

  19. PatientOne

    They've got their business model wrong, obviously: They need to look at how they can provide the light to their target users at a price those people can afford. Perhaps selling it to the more wealthy countries (I can see uses for it in camp sites and trail shelters, for example, where there is no mains power), then use that money to subsidise sales to the poorer nations? Sure someone's thought of this before - with a wind up radio...

    1. Chris Evans

      business model wrong? No.

      "They need to look at how they can provide the light to their target users at a price those people can afford. Perhaps selling it to the more wealthy countries "

      In a way they've already done that with the money they've raised for the prototypes, Profitable sales in the Developed world would be a good market but I'm sure they would spreading themselves too thin if they were to do that now and it can't be relied on.

      "then use that money to subsidise sales to the poorer nations?" If appropriate charities within the relevant countries may chose to subsidise or even give away the units.

      I'm a bit reluctant to say give away (Thomas Paine: "What we obtain too cheap, we esteem too lightly:")

      I have a lot of friends who work or have worked in developing countries (Micro Enterprise etc) and they tell me anything given away is often broken, discarded or lost quickly.[1]

      Short term emergency relief is another matter.

      [1]I'm sure the same basic problem happens in this country to!

      1. Anonymous Coward
        Anonymous Coward

        Re: business model wrong? No.

        "(Thomas Paine: "What we obtain too cheap, we esteem too lightly:")"

        That's easy to say when you're already in the upper class, isn't it?

        1. Don Jefe

          Re: business model wrong? No.

          Sales offsets almost never work out on the ground. If you're dealing with a low margin item, as most offset programs are, the costs of controlling the costs and managing distribution almost always exceed the income.

          You're almost always better off reducing unit cost and distributing them in a traditional manner where savings scale and piggyback deals can be had.

        2. Alan_Peery

          Re: business model wrong? No.

          Tell me that you haven't seen this phenomenon in your self and family members. I have, and it's nothing related to class. On the negative side it's called the sunk cost fallacy, and the positive side we call it pride of ownership.

  20. Anonymous Coward
    Anonymous Coward

    Seems okay, but some sort of system where you turn it over when it stops (like an hour glass or egg timer) would be better IMHO. You'd need a lot of sand and a paddle wheel, but the watermill is an existing tried and tested design.

    Also, why not have a solar panel and battery to act as a buffer?

    1. Piro

      So, a hard to repair solar panel..

      ... and a toxic battery that will wear out, be heavy and costly, and need replacing is a good idea for the target market?

      Nonsense, pure nonsense. Their first design WAS to do exactly that, and then, like any sensible person, they realised that is basically handing a hopeless black box that will break down to people who cannot repair it or have it serviced easily.

      This way, unless it is abused, it will give service for an extraordinarily long time, with nothing but simple lifting motion required when light is needed.

      Adding parts adds complexity, cost, and repairbility issues - not to mention handing out tons of toxic batteries is not exactly a great idea in a poor region with no recycling capability.

      1. Kiwi Silver badge

        Re: So, a hard to repair solar panel..

        ... and a toxic battery that will wear out, be heavy and costly, and need replacing is a good idea for the target market?

        You do get that this unit requires someone to lift a bag weighing a hell of a lot more than several laptop batteries several times a night, right?

        Nonsense, pure nonsense. Their first design WAS to do exactly that, and then, like any sensible person, they realised that is basically handing a hopeless black box that will break down to people who cannot repair it or have it serviced easily.

        Last week I picked up a half a dozen solar powered garden lights. Cost a couple of bucks each, (maybe) give more light than these "gravity" units do, and they come on when it gets dark enough at about 8:30pm and are still giving strong light at 2am. I couldn't tell you the actual wattage involved but it's enough that $10 worth of these will reasonably light a large room (normal Western house). How long they'll perform to the same level for is another matter, the batteries will probably start to fail in a few years depending on how cheap/nasty they really are.

        Complexity? Solar panel, battery (admittedly nicad which was a bit of a surprise), wires, probably some basic voltage or charge regulation, and a plastic case. Oh, and a very complex mechanical part called a "switch". No gears, no belts and pulleys, and so much effort to run that a physically drained or disabled mother could get it to work.

        Oh, and servicing? As much as I like to recycle and re-use, I doubt I would bother. The power used in heating up the soldering iron would almost outweigh the cost of a replacement.

        This way, unless it is abused, it will give service for an extraordinarily long time, with nothing but simple lifting motion required when light is needed.

        Simple. Several times a night. A bag weighing what, 5-10kg? In areas perhaps where there could be a large number of weakened or disabled people who will struggle to do that as much as needed? Also it is a mechanical device that relies on suspended weight. I would expect that the materials used are the most re

        not to mention handing out tons of toxic batteries is not exactly a great idea in a poor region with no recycling capability.

        Batteries can be contain quite nasty chemicals. Not sure on the chemistry of capacitors but guess they're not much better. But plastics can be quite bad as well, although I guess/hope these people are using something relatively "green".

        That said, I do like the concept. Anything that is able to help people to a better life (while still being resource/pollution etc friendly) I am happy with. Just not sure about the work (energy) input and the light output.

  21. Anonymous Coward
    Anonymous Coward

    why don't they put one in orbit as it'll be endlessly falling and generating never ending power for your LEDs

    1. Shaha Alam
      Trollface

      or tie the heavy weight in a loop so that it keeps going round and delivering free perpetual energy.

  22. Steven Jones

    Practicality?

    Of course this thing isn't powered by gravity at all. It's a storage system using (gravitational) potential energy. It's actually powered by food calories. It would be interesting to know just what the thermodynamic efficiency of the whole cycle would be. That includes the efficiency of the device, the human body, the production and harvesting of food etc. Not great I expect.,

    Of course, the device only stores about 200 joules (about 800 joules per hour running "flat out"), so that's only about 1kcal per hour, so it's tiny amounts - but, then so is the power output. I can't help but think a small rechargeable battery and solar cells would be a better approach,

    nb,. just what sort of device can be recharged sensibly at 1/10th of a watt?

    1. Filippo
      Mushroom

      Re: Practicality?

      Technically, as food ultimately grows from sunlight, it's solar-powered. Then again, knowing how sunlight is made, it's actually nuclear-powered. On the other hand, knowing how stars are made, it turns out it *really is* gravity-powered. So the article was right after all!

      1. Anonymous Coward
        Thumb Up

        Re: Practicality?

        >Technically, as food ultimately grows from sunlight, it's solar-powered. Then again, knowing how sunlight is made, it's actually nuclear-powered. On the other hand, knowing how stars are made, it turns out it *really is* gravity-powered. So the article was right after all!

        Love it!

      2. Steven Jones

        Re: Practicality?

        In fact the energy source for stars during their main sequence (as the Sun most certainly is on) does not come from gravitational collapse to any significant effect, Indeed, Lord Kelvin, who was, of course, unaware of the existence of the existence of nuclear energy, calculated the age of the Sun based on the energy available from gravitational collapse during its formation and the known power emission rates of the Sun. He came up with a maximum age of 300 million years, with a most likely figure closer to 100 million years. Of course this is a far shorter time than what we now know to be the current age of the Sun (about 4.5bn years). Gravitational collapse did, of course, provide the power source for "igniting" the nuclear reaction at the Sun's core, but it isn't powering it as such. The Sun is in a position of dynamic equilibrium with the outward force resulting from processes caused nuclear reaction at it's core balancing the gravitational force trying to make it collapse.

        Thus gravity at this stage of the Sun's life is essentially a containing force, and not something which is powering anything on Earth to any substantial degree. There will be times later in the Sun's life cycle when gravitational collapse will come into play (for instance, to provide the energy source for "igniting" the helium-carbon reaction). However, the Earth will be long, long past the point where solar energy will be powering food plants.

        nb. from another reply, the direct charging of batteries using solar cells is vastly more efficient than the path from solar to plants to humans to muscle power to electrical generators. An Ni-Mh cell will typically hold about 4-5,000 joules, or about as much energy as could be stored by lifting 10Kg 40-50metres. Such a battery can be fully charged in a few hours in tropical sun using a small, cheap (20x20cm) solar panel. I think more can be gained by making battery and solar cell technology cheaper and more robust.

    2. Chemist

      Re: Practicality?

      "the device only stores about 200 joules "

      In fact that's only ~50 cals or in food terms 0.05 (big) Cals or ~~ 1/4000 pint of beer !

      Not sure what the efficiency of 'burning' food cals is but judging by how hot I get shifting my 80 kg up 1000m of mountainside it could be quite poor !

    3. Piro

      Re: Practicality?

      Goodness me, the human effort involved may not make this entirely "efficient", but that human energy is almost worthless to talk about.

      The kids running about for 2 minutes would probably use more energy, and they'd do that without gaining light.

      The human energy cost is obvious, but not important in any way. Better than giving them easily broken solar panels and toxic batteries.

  23. Anonymous Coward
    Anonymous Coward

    A clever use of energy transfer indeed

    Fueling a human with energy from food (which ultimately comes from solar energy), to allow them to overcome the force of gravity and transfer that energy into stored potential energy is a great way to return it as small amounts of energy over a period of time.

    As long as the process is efficient, and doesn't lose to much energy in friction or in inefficient LEDs, then this looks like a very good solution.

    Cheaper than solar + batteries, more consistently reliable than wind, more convenient and quicker to reload than wind-up + battery storage.

    I bloody love applied physics me!

  24. ubergeek

    In the Olden Days.....

    I'm sure it used to be "Swing a light and pull up a sandbag....."

  25. Ragarath
    Thumb Up

    Good Luck!

    Good luck to them, if it gets accepted in poorer parts of the world then it may save hundreds if not thousands of lives which can only be a good thing.

    Though as mentioned in the article, I hope they can set up a hire / purchase deal because although $10 is not much to us it is to some people.

  26. lorisarvendu
    Unhappy

    New Stardrive! Oh- no, wait...

    I genuinely misread that as "Gravity Powered Light Ships" and got all excited for a few seconds there.

  27. Tim99 Silver badge

    To much SciFi

    I must improve my brain. I was a fair bit into the first sentence before I realized that it was not about star-ships.

  28. Zmodem

    call up drew the salvage hunters and tell them where to pick one up

  29. Lottie
    Pint

    An interesting platform

    I guess as a prototype and proof of concept this is great, but it will surely need a little more oomph to be practical?

    I wonder if this could be used during the day to charge batteries so that in the evening the lights can use the stored power?

    Outside of the overseas application, this would be great as a kids nighlight that is easy to use whilst also being passively educational.

    1. Don Jefe

      Re: An interesting platform

      In darkness, a light burning at 1/10th of a watt is the brightest light of all.

      You've also got to remember that the bulk of the target users for this lamp actually do brutally exhausting things during the daylight hours so they don't go home like us at night and faff around with all the stuff that keeps us awake. They need a minimal amount of light to accomplish important, short duration tasks during the night. If they can get that light without setting the house on fire or losing a half days wages for oil then so much the better.

  30. Pypes

    Nice idea

    I just can't see it working. Kerosene lamps are surprisingly bright, even low-tech updraught / cold blast, never mind the pressurised mantle lamps, certainly brighter than a Watt or so of LED light. They also burn for ages, and they contribute significant heat to the room (may not be an advantage in some locations.)

    The prospect of a (relatively) expensive alternative that is inferior to the original in all aspects other than running cost is a bit like marketing 20 grand push bikes as a great alternative to driving a car.

    1. Mike Richards Silver badge

      Re: Nice idea

      Kerosene does give a good light, but as the article says, it is hazardous to use, the smoke alone is a killer even if it is used 'safely'. And it is very expensive. We might complain here about the price of petrol as oil prices go up, but for very poor people reliant on kerosene the rises have been crippling, which is on top of countries phasing out subsidies for kerosene as part of their economic reforms.

      Good luck to them with this project. As someone said above, if it means a kid can learn or just enjoy a book after dark, it's worth the money.

    2. Anonymous Coward
      Anonymous Coward

      Re: Nice idea

      "The prospect of a (relatively) expensive alternative that is inferior to the original in all aspects other than running cost is a bit like marketing 20 grand push bikes as a great alternative to driving a car."

      Easy. Market it like all inferior solutions: Let Greenpeace start harking on about global warming, and the need to save the planet. The locals won't be impressed, but DECC and DFID will start throwing money at it, and the cost will come down to only $12 a piece.......oh.

    3. Vladimir Plouzhnikov

      Re: Nice idea

      "Kerosene lamps are surprisingly bright... They also burn for ages, and they contribute significant heat to the room"

      Not to say smell nice as well!

    4. Anonymous Coward
      Anonymous Coward

      Re: Nice idea

      They release nasty combustion products and are prone to starting fires. Kerosene also costs quite a bit and needs to be stored.

      1. Anonymous Coward
        Anonymous Coward

        Re: Nice idea

        But what if people are using kerosene ANYWAY...to COOK? Or what else do they use to cook around there?

        1. KayKay

          Re: Nice idea

          Wood. Twigs. Dried grass. Dried animal dung.

    5. Mike Flex

      Re: Nice idea

      "never mind the pressurised mantle lamps"

      Oh, you definitely should mind the pressurised mantle lamps. You need to turn them on at arm's length with your head tipped back.

      Why? Because if you didn't get the pre-heating just right the little b*gg*rs will shoot out burning paraffin to, ooh, arms length. So a LED light you can turn on without barbequing your head is a handy thing to have.

    6. Brian Miller

      Re: Nice idea

      The Aladdin brand kerosene mantle lamp puts out something like 60W of light. I bought one, and when the power went out, oh is it great! My home looked like the power was on, but it was just a kerosene lamp. A standard wick lamp is quite a bit dimmer, though. Since I now live next door to the power company, the electricity rarely goes out.

      The best alternative to the lamp is the Uco candle lantern, and I've lit my living room with one of those hanging from the ceiling light and using the top reflector. However, it's slightly more expensive than the gravity-powered light.

      I can see this as a reasonable thing. Think of the alternatives: running a light off of a bicycle generator. The good generators are rather spendy, and that's for a first-world budget!

    7. Slacker@work

      Re: Nice idea

      Generally a good idea but personally I think this fits the bill better...

      http://www.biolitestove.com/

  31. Ugotta B. Kiddingme

    next step: scale it up a bit

    I hope this is so enormously successful that the next logical step - scaling it up to "household" or "village" models comes next. If this can be sold for $10, imagine what a theoretical $1000 model could do. Stout triangular A-frame to hold the heavier duty gizmo, removable pulley system to assist in hoisting 100Kg or more. Add an optional battery storage system and you could theoretically power a largish array of efficient LEDs for several hours, possibly even overnight.

    The cost could be subsidized by relief/charitable organizations working in the region and those of us fortunate to live move developed areas

    1. Zmodem

      Re: next step: scale it up a bit

      it will probably cost £200, and for that your could build one of my perpetual generators and power all of your main lights in your home 24/7

      1. Anonymous Coward
        Anonymous Coward

        Re: next step: scale it up a bit

        Yes, you appear to have not only solved humanity's most pressing problem, along with all its devastating side effects, but outdone hundreds of thousands of engineers and disproved almost all of modern physics, all in one fell swoop!

        And yet here you sit, commenting about it on El Reg.

        Let me guess: The oil companies have threatened you, right?

      2. Zmodem

        Re: next step: scale it up a bit

        you could get a kW dynamo, and at full RPM, a 12v power drill motor set to 3amp fuse would be using 36 watts to spin the axle which leaves 964 watts a minute to power everything

        1. Zmodem

          Re: next step: scale it up a bit

          you have 1000 watts, a average wind turbine dynamo needs 20 RPM to generate its maximum output, a power drill motor is excessive and on full power would have an average 500-800 RPM

          1000 watts / 20 RPM = 50 watts for every full 1 dynamo turn

          on startup recharges the battery in the loop, if solar power has`nt fully recharged the battery to be able to start the loop

          you run things off a buffered delayed loop and wait for the dynamo to be at its maximum RPM and output before you use any of the generated power

          you could happily run around mars for 10 years for the lifetime of the motor and coil, and have 10 kW on the next shuttle, or have 6MW wind farm turbine on cargo ocean ships

          if you have all the proper electrician skills and specs of the dynamo, you could probably make it 98% effecient with a motor made for the axle

          1. Zmodem

            Re: next step: scale it up a bit

            if your a proper electrician, you can get some etch board from maplin or RS online, and make your own regulator for give the motor enough watts for it to run at a constant 20 RPM, and dont need a seperate mains powered regulator

            power drill motors have enough torque to goto 10Kw turbine or more

          2. MrXavia

            @Zmodem, are you on medication?

            while I might think our laws of physics are wrong, and the 2nd law of thermodynamics (entropy of an isolated system never decreases) needs a tweak, there is no way I anyone with half a brain could think you can get something for nothing like that...

            (so, this 2nd law, is there a reason you cannot convert the energy of a bunch of hot atoms bouncing around into electrical energy without a cold area to heat up? Couldn't we just convert the blackbody radiation the same as we do with solar cells? it IS radiation and radiation is energy?)

            1. Zmodem

              Re: @Zmodem, are you on medication?

              theres no physics involved...

              the average wind turbine setup in your attic/loft/house includes :

              a turbine with a direct drive dynamo inside if it costs a few extra pounds,

              a battery to store generated electric

              an invertor which connects the battery to the mains grid of your house

              if the battery already contains some power, which can be charged using solar power, you use the current existing power to power the motor, and when the dynamo is at the minimum generating RPM the battery begins to recharge

              when the motor is running and the dynamo is spinning at its maximum generating RPM of 20, to generate the total watts per minute of full spin, the motor wont be using many watts, while the rest of the power goes to the mains grid

              1. Zmodem

                Re: @Zmodem, are you on medication?

                in reality you could have everything in a 10 litre bin and a cable going to a solar panel on your roof, an average house would need a 20kw generator

          3. Zmodem

            Re: next step: scale it up a bit

            if your a proper electrician, you can get some etch board from maplin or RS online, and make your own regulator for give the motor enough watts for it to run at a constant 20 RPM, and dont need a seperate mains powered regulator

            power drill motors have enough torque to goto 10Kw turbine or more

            the axle on the dynamo would also be either bigger or smaller then the spin ratio of the motor, so they would both be running at different RPM, so would never use more then your 36 watts going to the motor, to turn the direct drive dynamo on a wind turbine instead of using wind

  32. Destroy All Monsters Silver badge

    USD 10 sounds expensive

    Is this western fiat money level pricing?

  33. Heathroi

    It would certainly be appreciated by African insects.

  34. paulc

    you mean like this?

    http://www.gooutdoors.co.uk/hi-gear-12-led-wind-up-style-mini-camping-lantern-p143639?gclid=CPz29tmtmbsCFRLMtAodwmkAcg

    simple google search for wind up lantern

  35. All names Taken
    Paris Hilton

    <polite applause>

    well done chaps

    </polite applause>

  36. Anonymous Coward
    Anonymous Coward

    It's worth mentioning that from the target audience's perspective, that $10 cost is the equivalent of something like $800 or $1000 to most of us reading this. It's a Big F*cking Deal to be able to afford one of these.

    That's not to say that they haven't done a good job - but it does put some perspective on how well we live compared to most people in the world. I mean, when I want some extra light in my bedroom, I'll use the flash on my phone - the contract for which would cost more than the entire income of a lot of the people who might use this light. Buying the device outright is pretty much the same for someone in those circumstances as spending $150,000 for one of us; an absurdity.

    There isn't any easy solution to any of this, and I'm not writing it to rage against the horrible iniquity of it all - that's been done before - but it's worth remembering once in a while, if for no other reason than to give oneself a sense of perspective about one's own life.

    1. Kiwi Silver badge

      It's worth mentioning that from the target audience's perspective, that $10 cost is the equivalent of something like $800 or $1000 to most of us reading this.

      True, $10 to them is like a lot to us (I've supported kids overseas through certain organisations in the past - the piddly little sum I pay per week is more than both parents can earn working full time!).

      But I think one of the key things is that to us this is a trifling amount. A few thousand westerners spend an extra $10 at Christmas, a few thousand 3rd world families get cheap light.

      Not sure if that's their plan or not, but it's something I could consider (i would also make sure there isn't something better first).

  37. I sound like Peter Griffin!!

    You all forget something fundamentally important...

    I've first-hand experience of living in parts of the world (Africa, 3 countries) where the kerosene/paraffin lamps are used.. They're fairly bright and they are PORTABLE; you're talking about replacing a lighting technology that you can lend to someone so they can light up the way to the next village along in gusty conditions, or light up the way to the pit toilet outside..

    This won't solve that - it's a very good attempt though..

    Wind-up technology is better at the moment for a fair number of people...

  38. Andy The Hat Silver badge

    A boot note to this. What exactly has been invented? Every schoolkid does exactly this experiment using a mass, a motor/dynamo and a bulb or meter?

    1. Anonymous Coward
      Anonymous Coward

      Does every school kid make it save to use for someone completely inexperienced, practical to mass produce for a sale price of $10, and work for hours rather than a minute or two?

  39. Stevie Silver badge

    Bah!

    So, not really gravity powered then? That would be something that didn't need rewinding at all. More like glorified clockwork if you think about it. My mother-in-law has a case clock that works much the same way.

    As for the Proprietary Wonder Device, I'm going to go out on a limb and suggest it might be a vastly overdriven gearbox turning a conventional modern brushless motor wired as a generator and connected through various electronics to shape the juice to order.

    Replace the weights with a clockwork mechanism and we've seen it before.

  40. Sir Sham Cad

    Economies of scale

    I'm going to assume that the device turns the dynamo at a set speed within the given mass tolerances and it is this that determines the power output. This means the height the weight is lifted to, given a set speed, directly relates to the time that the power output can be sustained for.

    That output is not going to light a home or charge a mobile phone and it's priced fairly equivalently to a Dyson Fan which is a premium lifestyle product. It needs to have more pooerrr (read in a Jimmy Doohan accent).

    How about a large frame, maybe 30 feet high, with several of the dynamo/weight arrays along it with block-and-tackle as has been suggested by other commentards, giving (trusting my old schoolboy physics) a total power output if we link the dynamo arrays, Ptotal=(P1xn) where P1= power of one unit and n is the number of units, then we can provide 2.5 hours of useful Ptotal from not a lot more human effort (assuming more than one person helps with the lifting).

  41. David 45

    De ja vu

    Thought I'd seen this attempted quite a few years ago.

  42. Anonymous Coward
    Anonymous Coward

    Another vote for The Gravity Powered Light Ships, those I want to be told about!

  43. btrower

    Did anybody do the math?

    I am not sure I have the figures correct, but it looks like after 10 hours of use this puts out one thousandth of a KwH. Assuming they keep that fired up 10 hours a day 333 days a year, they will put out about 10 cents worth of electricity after three years. Given a thirty year service life this $10 generator would put out a dollar's worth of electricity. That does not include the cost of hiring someone to keep lifting the weight.

    Would it not be cheaper and more humane to simply sell them a couple of dollars worth of batteries?

    I am sure I must have slipped a decimal point somewhere, but everyone should know that heat energy and electrical energy are equivalent to enormous amounts of stored kinetic energy. Using humans to generate power is a really big step backward.

    1. MrXavia

      Re: Did anybody do the math?

      Good point!!!

      Maybe a better idea would be some kind of rudimentary battery that can be jury rigged with common materials?

      how about this (if the cost can be reduced to $5ish)

      http://technorati.com/technology/article/urine-powered-batteries-why-ill-never/

  44. Paul Hovnanian Silver badge

    Next step: Whip up a general purpose generator kit. Offer it with some interchangeable gears (think LEGO*). Let the locals or some NGO group find various input power sources and produce instructions install them. I recall seeing a low power generator running off a crank connected to a paddle in a creek that oscillated in an eddy current.

    *We'll need the obligatory Playmobil mockup for proof of concept.

  45. Zot

    A wind-up light is far better and lasts longer...

    6 LED lamp...

    "This practical lantern is simple to use as you simply need to wind up the torch for 1 minute to enjoy 25 minutes of light. It takes just 10 minutes of winding to fully charge the lantern, giving you 100 minutes of light and making it perfect for camping." :-

    http://www.blacks.co.uk/activities/108003-eurohike-6-led-lantern.html

    So... yeah, I don't get it.

  46. Dan Paul

    Hamster Wheel!

    Perhaps using a hamster wheel made from local materials, connected to a somewhat larger version of a generator set, they could use pack animals or even people to create greater amounts of electricity.

    Add cups or paddles to the outer rim of the hamsterwheel and you could have a reasonable waterwheel for power without animals.

    However, I believe that the inventors were trying to come up with a replacement for an oil lamp typically used in a hut, NOT trying to come up with a major power generating system.

    Give credit where it's due.

    1. Anonymous Coward
      Anonymous Coward

      Re: Hamster Wheel!

      Mmmmmm! Hamsters!

  47. kwhitefoot

    Sounds like another 'designer' not living in the real world.

    Here in Norway paraffin costs about a US dollar a litre and delivers about 9kWh per litre so if we can assume very roughly 25% conversion efficiency in some sort of thermoelectric converter and round a bit we get 2.5kWh per dollar so the device is worth 25kWh if it sells for USD10. At one deciwatt that is 250 hours before it breaks even. The question is: is 0.1W of light worth having.

    For a bit more you could buy a 1.5W @ 12V solar charger and a few nicads (source Maplin's website). Assuming we are talking about a warm country we can rely on say 5 hours of sunshine giving 7.5Wh per day, if the battries convert this at 25% we have roughly 2Wh per day for zero mechanical effort. If it is used for four hours in the evening that is 0.5W, five times the output for twice the price using off the shelf components that are getting steadily cheaper and are easily obtained all over the world and are maintanable by people who have only simple tools.

    Actually what bothers me most about the Deciwatt is the website and its utter lack of numerical information.

  48. kwhitefoot

    Oops, must stop posting late at night when tired, etc.

    Paraffin is 9kWhr per litre

    So at 25% efficiency we get roughly 2500Wh for a dollar or 25000 for the USD 10 this thing is expected to cost.

    So at a deciwatt we are talking about a quarter of a million hours before it pays back.

    Will it last that long?

    Aplogies in advance if I have dropped/added a few powers of ten again.

  49. OrsonX

    Version 2

    Wouldn't it be more efficient to attach the gear system directly to a dynamo and then harvest the electricity quickly using a capacitor? i.e., effectively wind-up but driven by weight? In this way you could spend 10 minutes lifting the weight a few times but then have electricity for a few hours.

  50. John X Public
    Boffin

    First World Hubris

    Rather than riding in to the village on your cool first world gadget to rescue the poor natives, how about adapting some technology to local conditions instead? Stick a dynamo on one of these and get a bit more than 0.1W plus a more continuous power feed:

    http://en.wikipedia.org/wiki/Horse_mill

    http://www.worldwideflood.com/ark/technology/ox_mill_small.jpg

    They are poor, not stupid.

  51. Anonymous Coward
    Anonymous Coward

    Nobel Peace Prize in 3..2..1..

    I think these guys should be nominated at least, this is a very clever piece of engineering that will help many poor children achieve their potential.

    Don't forget that many doctors in this country started out as poor children in South Africa, and many of them send a big chunk of their wages back home as an act of compassion.

  52. FunkyEric

    And there was I wondering what a "Gravity powered light ship" was.........

    Sounded really cool, too!

  53. David Glasgow

    Curse you headline writer!

    So this isn't about combining solar sails with a gravity converter to finally allow interstellar travel?

    Don't you know HOW OLD I AM? My time is running out, and I have been waiting so long.....

    Nice trick with a bag of rocks and an LED though.

  54. tojb

    Horse powered

    Reminds me of an old photo I saw of a bloke in a flat cap leading a shire horse connected to some pulleys, connected to some very big weights in a very high-roofed barn, connected to a genny to run the squire's newfangled galvanic illuminators.

  55. Anonymous Coward
    Anonymous Coward

    Crap...

    Why don't they just collect the gas from their crap? other countries do it in rural areas?

    In Rural China they do it, and use it to cook, its a tiny step up to use the gas to make light...

  56. Frankee Llonnygog

    Pet-power?

    Put a treat on the hoist, pet jumps on, hoist goes down, light lights up. Admittedly it'd have to be a fat pet...

  57. maladmin

    Built it with lego

    A while back I built a similar contraption out of lego to light up my (kids) lego city. Two big lego wheels with a drop of about a meter lit two LEDs for about 30 seconds, it took slightly longer to wind the mechanism back up. The lego motors were efficient enough that connecting two together allowed me to power a windmill somewhere across the table.

  58. Dylan Fahey

    Why proprietary?

    Why would you want to charge a poor person for a light, are we that greedy?

  59. Hey Nonny Nonny Mouse

    Prior art?

    Pretty sure Trevor Bayliss suggested something very similar in a pop science/documentary around the time his clockwork radio made him famous?

  60. Less work more output

    Thought bubble . . .

    What if a lead-acid battery was used as the weight . . ?

  61. Anonymous Coward
    Anonymous Coward

    Re. Thought bubble

    There's an idea.

    What about combining recycled 12V security batteries, recycled stepper motors with diodes, Joule Thief and cheap LED "strips" from demised LCD panels, available for nothing if you know who to ask :-)

    Someone should put some unemployed people to work making these, the fine soldering is useful experience and it beats sorting recycling or cleaning roads.

    A lot of the dead lead acids available locally are actually fine if left charging for weeks on a solar panel, the problem is high internal resistance due to one shorted cell not lack of capacity.

    PB-acid gels last a lot longer than their "official" life

    Source: The Hacker's Cookbook, 2013 edition :-)

This topic is closed for new posts.

Biting the hand that feeds IT © 1998–2019