Light bulbs have always required more electricity than they need to produce light because the energy conversion process—changing electricity to light—was inefficient. But an MIT research team has just shown that an LED can actually give off more light than what it consumes in electricity.
Incandescent bulbs are the poster child of inefficient energy conversion. The devices heated a filament with an electrical current which not only produced light, but a lot of waste heat as well. Fluorescent bulbs, CFL's, and even conventional LED's all generate the same waste heat to varying (albeit much smaller) degrees but none has ever reached 100-percent efficiency—a mark known as "unity efficiency."
The team from MIT posited that while the bulbs energy requirements decrease at an exponential rate (halving the voltage reduces the input power by a factor of four), the lumen output would decrease linearly (halve the voltage and the lumens drop by half as well). This means that at some point, the amount of lumens the bulb is emitting would be more than the amount of energy spent—essentially "free" light.
Granted, this point occurs only when using minuscule amounts of electricity to power incredibly dim bulbs. In their experiments, the team was able to generate 69 picowatts of light from just 30 picowatts of energy. They did so by harnessing waste heat, which is caused by vibrations in the bulb's atomic lattice, to compensate for the losses in electrical power. The device also reacts to ambient heat in the room to increase its efficiency and power the bulb.
This process cools the bulb slightly and could eventually be employed to manufacture "cold" bulbs that don't generate any heat, only light. And, since the same physical mechanism from these tiny bulbs can be applied to any LED, they likely will be. [Physics via Physorg]
Source: gizmodo.comAdded: 6 March 2012