Scientists Create 230% Efficient LED Bulbs

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 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, CFLs and even conventional LEDs all generate the same waste heat to varying (albeit much smaller) degrees but none has ever reached 100 per cent 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]

Image: Kristina Postnikova / Shutterstock

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    Sounds related to that recent development in laser cooling ... can't wait for the day this trivialises global warming. We'll just emit the heat away as light. Future looks brighter already.

      I see what you did there.

    I really hope someone checks their results, because you can't get more energy out of something than you put in. Unless the semiconductor is losing mass due to nuclear activity, and that mass gets released as energy. Even so, that would be in the gamma ray spectrum, not the visible spectrum.

      Yeah, something of a misleading title - it definitely has to obey conservation of energy. If you get more than 100% efficiency you're not comparing the right inputs/outputs. The explanation mentioned in the article is "The device also reacts to ambient heat in the room to increase its efficiency and power the bulb" (while they're measuring efficiency as output light power / input electrical power instead of output light power / total input power), which is pretty surprising if correct.

        Sounds a little sus, (checks that it is not April 1), I guess if true, the extra 39 picowatts of energy must be coming from ambient heat.

          Yep basically. It's not unbelievable/impossible or anything, but quite surprising (hence it being newsworthy!).

          You'd get similar numbers from a heat pump if you calculated it as heat out power / electrical nput power since that's ignoring the ambient heat input power.

            Problem is being in the picowatt range you'll need billions of them to light a small room!


              You would also notice that as you increase the number of bulbs required to light the small room, you would also have to increase the size of the room to accommodate the bulbs, and subsequently increase the number of bulbs to light the room, and so on, ad infinitum.

              I believe the greatest efficiency would achieved as the size of the room and the number of bulbs approaches 0

              This is true, but there a many many more applications for LEDs than lighting a room. For example, this could lead to better screens with a higher pixel density and colour ratios, or making reflective sheets out of them into light fittings, or making LEDs so cheap to manufacture that they can cover car interiors and electronics.
              Only limited by one's imagination.

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