Gravity Powered LED Floor Lamp
February 19th, 2008
Clay Moulton a Virginia tech student has designed a way to harness the power of a force that will never go away: gravity. The Gravia is an LED lamp that works by the force of a weight, sort of like a grandfather clock.
The Gravia lamp column glows when activated. The electricity is generated by the slow fall of a mass that spins a rotor. The resulting energy powers 10 high-output LEDs that fire into the acrylic lens, creating a diffuse light. The operation is silent and the housing is elegant and cord free – completely independent of electrical infrastructure.
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. With the sled gently gliding back down, within a few seconds, the LEDs come on and light the lamp, Moulton said. “It’s more complicated than flipping a switch but can be an acceptable, even enjoyable routine, like winding a beautiful clock or making good coffee
Via Coolest Gadgets
Posted in Future Tech
The conference organizer must feel pretty silly giving an award to such a bogus bit of design. 50 lbs lifted by 60″ in Earth’s gravity gives a total energy of 346 Joules, or .025 Watt over 4 hours (that’s 0.1 W-hr). The best LEDs available today produce 200 lumens / Watt. What this all means is that Clay’s Moulton’s Gravia will run for about 1 minute, not 4 hours.
I read at another web page that this was a contest for “future technologies,” i.e., things that could probably be built some time in the future. The projects in this contest won’t work today, and that was the point of the contest, to design for the future.
The lamp in question could not be built EVER, not now, not in the near future, never. At least not without the inclusion of a convenient method to break the laws of physics. DesignWithIntegrity’s calculation (assuming the maths are right, I didn’t check) clearly shows that the device would produce 25mW over the stated run-time. Being generous and quadrupling this number (ie a 200lb weight or a 1 hr runtime,) we get a light output of 68 lumens. That’s with 100% efficient LED! Note that the efficiency I’m referring to is quantum efficiency, not luminous efficiency. Also note that the LED would have to be 555nm, or green. A blue or white light source is inherently less luminously efficient.
Reference from onlineconversion.com
Re: Lumens / Watts
by Chris Ward on 12/13/05 at 14:17:17
Lumens and Watts are just photometric and radiometric terms for the same thing: optical power or flux. The only difference is that photometry (luminous power) takes into account human perception and accounts for the sensitivity of the eye to different colors. This can make it difficult to convert between the two unless you know the spectra of the bulb.
By definition, at the peak sensitivity of the eye (green 555nm) 1 Watt equals 680 lumens.
It would make the most sense to talk about lumens with a flashligh, because what you really care about is the perceived “brightness”, not the true optical power.
Chris
This information can be referenced on pg. 27 of “Optoelectronics”, Prentice Hall 1983
Great idea, now use a large tank of water for weight, (tap fillable), better and fewer LEDs,and don’t expect to light the universe. A small lamp at the top of a page will suffice for most reading needs.