Gravity lamp debunked

In a display of the awesomeness of the Internet, users of the website Slashdot have thoroughly debunked claims made by the inventor of the Gravia Gravity Lamp. The inventor claimed that the lamp could use a 50lb weight dropping five feet to power a 700 lumen LED for 4 hours.

But when the Slashdotters actually did the math, they discovered a few flaws. First, the inventor assumed 100% efficiency.

Much worse is that the Gravia guy seems to have put a decimal in the wrong place and ended up with completely erroneous numbers:

There's 50lbs of weight that fall about 4 feet, 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.

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 4 feet of fall that amounts to 925lbs. My goodness, that is a group effort.

It's sad news, but it is nonetheless the case. The inventor has admitted his mistake and offered the Greener Gadgets honor to the runner-up below him.

Really, this makes you appreciate how much work needs to be done even to power the lowest-wattage light bulbs. Sometimes, it's good to realize how really remarkable and efficient our current system is ... even if it comes at the cost of an idea that, at first glance, looked quite appealing.

Via Slashdot