How Gravity-powered Floor Lamps Will Work

By: Julia Layton

Image courtesy of Clay Moulton

When you hear the phrase "alternative energy," chances are your mind goes to windmills and solar panels, or perhaps fields of corn. Few people think of human beings as a renewable energy source. But a new lamp design taps into just that idea.

It's not a new concept: Wind-up watches and clocks, and even hourglass-style timekeepers, have relied on humans as energy sources for many centuries. A person winds it up or flips it over, and the device has a renewed supply of potential energy with which to operate. Modern inventions like bicycle-powered blenders and kinetic battery chargers draw on energy stored in the human body, too.


Much like these designs, the gravity-powered lamp envisioned by Clay Moulton, a graduate student at Virginia Tech when his lamp won second place at the 2008 Greener Gadgets Design Competition, relies on people for power. In this case, the people don't wind a gear or pedal a bike; instead, they lift a series of weights back to their starting point. The Gravia lamp is powered by the falling motion of those weights, also known as gravity.

It's an interesting idea, using a (presumably) limitless resource like the pull of gravity to generate power. And while the Gravia lamp requires some advances in technology before it becomes a viable product, the concept is worth checking out. In this article, we'll get into the Gravia lamp and see what makes it glow, and we'll find out why a gravity-powered lamp may be an alternative-energy gadget to keep an eye out for.

Perhaps the most brilliant part of the Gravia design is its simplicity. Let's start by looking at the lamp's inner workings.

Gravity-powered Energy

Gravia lamp
Gravia lamp
Image courtesy of Clay Moulton

The idea of using the force of gravity to generate power has been around for some time. As far back as the 1970s, for instance, scientists were discussing the theoretical possibility of tapping into the gravitational pull of black holes to generate power [source: Time]. The idea was that if matter could be fired at a black hole from a safe distance (so the firing device wouldn't be sucked in), the extreme squeezing of that matter by the hole's gravity would make it hot enough to start a fusion reaction.

The Gravia lamp relies on a much simpler concept: Gravity pulls objects downward.


The lamp is a standing floor lamp, 58 inches (147 centimeters) tall and cylinder-shaped. Inside the cylinder, there are several basic parts involved in creating light: brass weights, a ball screw, a drive gear, a rotor, generator and a bunch of LEDs. Here's how the process works:

  1. A person attaches five 10-pound (4.5-kilogram) brass weights to a ball screw near the top of the lamp.
  2. The platform immediately starts dropping along the screw, which is aligned along the length of the lamp. As the platform makes its way down the screw, the screw spins. This converts the downward motion of gravity (acting on the weights) into the rotational motion needed to spin the gear near the bottom of the lamp.
  3. The spinning gear in turn spins a generator -- a rotor/stator assembly that converts the rotational motion into electricity.
  4. The electricity powers 10 LED bulbs, which light up and illuminate the acrylic housing of the lamp.

All of this happens over the course of four hours, and the LEDs, which light up a few seconds after the weights start to drop, remain on for that full period. They emit between 600 and 800 lumens, which is comparable to a typical 40-watt bulb [source: Dunn]. When the weights make it to the bottom of the lamp, the LEDs go out, and the person who started the chain of events has to input more power by moving the weights back up to the top of the screw.

Using gravity to light up LEDs is pretty amazing as it is. But the lamp has some benefits beyond being a conversation piece.

Benefits of Gravity-powered Floor Lamps

Any way you look at it, gravity as an energy source is hard to beat. It's free, it's in endless supply, and you don't have to import it, mine it, refine it or grow it. The very force that keeps you rooted to the ground could end up powering your house some day.

Since the Gravia lamp wouldn't plug into an outlet at all, it's about as "green" a gadget as you're going to find -- except maybe a solar-powered cell-phone charger or wind-powered tent lighting. The device is entirely self-contained, relying solely on human input to trigger the cycle that creates light. There's no outside energy required beyond that which goes into producing the lamp components in the first place.


And those components, according to the inventor, will never need to be replaced -- or at least not in a human lifetime. He estimates the lamp will work for 200 years [source: Dunn]. LED technology, on the other hand, is not quite to the point of the 200-year bulb. You'd have to buy new LEDs as they burn out. The state of that technology, in fact, is the reason why you can't actually go buy this lamp for your home.

In concept, the lamp is an award winner. In reality, it has a ways to go.

To generate enough power to light up those bulbs, the brass weights would have to weigh substantially more than a collective 50 pounds. They'd have to weigh about 2 tons (1.8 metric tons) -- a bit much for your typical human being to lift to the top of the lamp [source: Core77]. LEDs will have to become significantly more efficient before the Gravia lamp becomes a real possibility.

For more information on the Gravia lamp, gravity power and related topics, look over the links on the next page.

Lots More Information

Related HowStuffWorks Articles

  • Dunn, Collin. "Gravia: LED Lamp Lit by Gravity Lasts 200 Years, Never Plugs In." TreeHugger. Feb. 21, 2008.
  • GizMag. "The gravity powered floor lamp." Feb. 20, 2008.
  • Gravia. "Greener Gadgets Design Competition 2008." Core77.
  • Trulove, Susan. "Lamp lit by gravity wins Greener Gadget award." Virginia Tech News. Feb. 19, 2008.