Slashdot Mirror
Gravity Lamp Grabs Green Prize
eldavojohn writes "A lamp powered by gravity has won the second prize at the Greener Gadgets Conference in NYC. From the article, "The light output will be 600-800 lumens — roughly equal to a 40-watt incandescent bulb over a period of four hours. To "turn on" the lamp, the user moves weights from the bottom to the top of the lamp. An hour glass-like mechanism is turned over and the weights are placed in the mass sled near the top of the lamp. The sled begins its gentle glide back down and, within a few seconds, the LEDs come on and light the lamp ... Moulton estimates that Gravia's mechanisms will last more than 200 years, if used eight hours a day, 365 days a year." The article contains links to the patents and the designer/inventor Clay Moulton's site." I think my laptop would require a slightly larger weight to pull this off.
Say what?!? Why on earth would they tell you that?
This is slashdot, we have articles here, not thinly disguised advertisements.
At the bottom of the
How about a clock?
i'm going to use the light from this lamp to power my photovoltaic weight lifting machine.
Will it still be cool to light up your lamp with gravity, when there's no gravity left and people are spinning right off the planet into outerspace? I guess it will eliminate the greenhouse gas issue by allowing the atmosphere to disappear when there's no more gravity left - but unfortunately it will also not allow people to live (the ones that are still on the planet after the other ones spun off into space as noted earlier)
But what will we do after peak gravity?
You don't know the difference between a lamp and a clock?
One tells time, the other emits light. I thought that was fairly obvious.
Slashdot: Playing Favorites Since 1997
Duh! Because it's a *light* powered by weights!
No sig for you!!
I am Jack's complete lack of surprise.
I've already started looking into buying "gravity offsets" and trying to use as much rope, glue, velcro, and static cling as possible.
I like basketball!!1!
I can't really see why a small electric motor couldn't be incorporated into the design to do this, surely it would be much more convenient?
how long before the home gym captures energy for your home.
:-)
Never
Humans can not produce large amounts of sustained output power, even when exercising. A "healthy human" can probably push out 300W for about 20 minutes before they collapse from exhaustion. Even if you can convert all of that to electricity and store it for later use at something like 50% efficiency (which would be staggeringly high), you're only talking about 0.05kWh of usable energy. You could do much better if you were willing to exercise at much lower intensity for much much longer periods of time (but who would do that just to light a minuscule handful of light bulbs). But you're really not going to ever get usable amounts of power out of your daily exercise routine.
22.6 Kg x 1m x 9.8 m/s^2 / 4 hours = 0.015W if conversion is 100% efficient (which it won't be)
The red led on the front of your modem requires around this amount so the glow will be feable. To get the equivalent of a filament 40W bulb requires around 10W so the system is only around a factor of 1000 out.
wot no sig
Yup, they say it emits 600-800 lumens.
Given that LEDs emit about 100 lumens/watt, that's say, 6 watts, * 4 hours = 86,400 joules They claim it's about 2m high.
Plugging those two values into the gravitational potential energy calculator at http://hyperphysics.phy-astr.gsu.edu/Hbase/gpot.html gives a weight of about 5000kg, slightly above the claimed 22kg...
For the average male, yes. But this is slashdot. One only needs the strength of a wet noodle to post here, and actual exercise is frowned upon. As is leaving the basement for fresh air and/or a little sun.
120 characters for a sig? That's bloody useless.
You sir, are correct.
.....3.8 lumens. A candle is ...13 lumens. So it's about a third of a candle. An ideal light source is ~680 lumens/watt would be 13 lumens, or a candle.
There's 50lbs of weight that fall about 4ft, if I'm reading the diagrams right. That's 200 ft-lbs. Which comes out to... hmm... 0.075 watt-hours. Over 4 hours that means 0.019 watts continuous power. From memory really good blue LEDs are around 200 lumens/watt so
To get ~700 lumen light at 200 lumen/watt would require 3.5 watts of power, over 4 hours is 14 watt-hours or 3700 ft-lbs. Over 4ft of fall that amounts to 925 lbs. My goodness, that is a group effort.
I've been on slashdot so long I'm starting to get out of touch with the cool stuff if it ain't on slashdot.
so why has he not actually built the thing?
because it cant be made. You have a better chance at making cold fusion work or a perpetual motion machine than making this lamp do what was claimed.
first, there is no way for them to make enough energy even assuming 100% conversion to generate the electricity needed to power even 1 led for enough light to match that of a book light, many others here have covered this fact already..
Secondly the designer made HUGE mistakes in assumption is is a fact being missed by everyone else here debunking it.. Led's when rated in lumens are rated in their very narrow beam pattern, when you fire it into a lens/reflector to disperse the light to get an area lighting effect that his lamp is going for the lumens drop logarithmically. to go from the 15Deg beam pattern the LED's lumen output is measured at to a 270 degree pattern you will lose about 80% of the lumen output level.
So to get The claimed output, the device needs to generate a SHITLOAD more power, or increase the weight to be near 900 pounds or only operate for a few seconds at a time.
In other words, it does not work, cant work, and will never work. I think the guy is waiting for the laws of physics to be broken for his lamp to work.
I have been working with a company that designs LED lighting systems and most everyone get's confused because ratings on LED's are all over the road and not measured the same way as other lamp technologies.
This lamp if it used CFL lamps would have a far better chance at makign the claimed Lumen output than with LED's led's are still far-far less efficient than CFL lamps when it comes to area light output in beam widths wider than 20 degrees.
Do not look at laser with remaining good eye.