Unraveling the mystery of the "perpetual motion machine": LED technology with a power conversion efficiency of 230%

According to recent reports from the US media, researchers at the Massachusetts Institute of Technology (MIT) have used a socket conversion device to enable light-emitting diodes (LEDs) to release more optical power than the electrical power they consume, with a power conversion efficiency of over 100%.

The principle of LED light emission is to convert electrical energy into light. Currently, one of the biggest obstacles to designing bright and efficient LED lights is that increasing the output power of LED lights will cause their efficiency to decrease. However, researchers at MIT explained that their research results greatly reduced the external voltage. According to calculations, when the voltage is reduced to half, the input power is reduced by 4 times, while the light power emitted remains the same as the voltage and is also half. In other words, when the output power decreases, the LED luminescence rate increases.

In their experiments, the researchers reduced the input power of the LED to just 30 picowatts and measured an output of 69 picowatts of light, an efficiency of 230 percent. The same physics applies to any LED: electrons and holes have a certain probability of producing photons under an applied voltage. Rather than trying to increase that probability, as other studies have done, the researchers used the small amount of waste heat generated by the vibrations of the atomic lattice in the device to generate more electricity.

This process of using waste heat to emit light allows the LED to cool slightly, operating like a thermoelectric cooler. While at room temperature, the cooling is not enough to provide practical temperatures, it could potentially be used to design lamps that don't generate heat. When used as a heat pump, the device could help solid-state cooling applications and even power generators.

In theory, this low-voltage strategy can generate arbitrarily efficient photons at low voltages, and the researchers hope that the technique will provide a new way to test the limits of energy-efficient electromagnetic communications. While scientifically interesting, the approach will not immediately lead to the commercialization of ultra-efficient LEDs, as the demonstration project only produced small amounts of light with very low input power.

First, let me explain everyone's confusion about the "perpetual motion machine". An engineer from an English website gave the following interpretation: No perpetual motion machine is created here. The article failed to mention the real reason why the LED can exceed 100% efficiency. Here is why:

It’s nice research， but it’s sort of “cheating” in an honest way. Efficiency mentioned here is how much electricity is converted into light by this LED. Let’s say， you inject 10 electrons， and they turn into 8 photons which escaped the LED， so you get a 80% efficient LED. The 2 missing electrons are “wasted”。 So， in order to get to 100% efficiency and beyond， you find another way to make up for those 2 missing electrons. MIT team used the well-known thermoelectric effect which converts heat to electricity， which in return makes up for those “wasted” electrons. As a result， this LED has over 100% efficiency. You now see why they choose to do the experiment as very low voltage， because low voltage means less electrons injects， so fewer “wasted” electrons you need to make up.

Therefore， the over 100% efficiency is kinda of “cheating” in an honest way. What’s supplying this ultra low voltage LED electrons are not electricity alone， but also ambient temperature in form of thermo energy. The quoted efficiency in this article is a ratio between photon generated by TWO sources of energy and input from ONE source of energy. Of course， the efficiency can be much higher than 100%.

It’s that simple， but I do not in anyway wish to undermine the importance of this research. It’s good work. I just don’t wish others who does not have background on this specific topic to misunderstood the importance and message of this research work.

In order to help engineers better understand this technical report, we have found some English reports for your reference:

Scientists Create 230-Percent 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 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 bulb‘s 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.

MIT Researchers Create LED Light That Exceeds 100-Percent Efficiency

Light bulbs have always been pretty inefficient， even those that have a rep for using less juice， like LEDs. Because of the energy conversion process， they consume more energy than they actually need to illuminate. But what if we told you that there was a light bulb out there， just waiting to be invented， that could produce more energy than it consumes？ A group of researchers at MIT have figured out how to develop LED lights that wildly eclipse the efficiency of any other bulb. In fact， they successfully tested a LED light with an efficiency of 230 percent！

The key to increasing the power conversion efficiency， according to MIT researcher Parthiban Santhanam and his co-authors， is to decrease the applied voltage. When the voltage is halved， the input power is decreased by a factor of four. （The inverse is also true — the brighter LED lights are， the less efficient they become.） In effect， if you decrease the input power enough， the LED’s efficiency can increase to more than 100 percent， thus achieving what’s known as “unity efficiency.” When that happens， the light bulb will produce as much or more energy than it takes to power it， giving you the ultimate bang for your buck.

The only problem？ As you may have guessed， significantly lowering the input power creates a very weak LED bulb. In their tests， the MIT researchers succeeded in generating about 70 picowatts of light from 30 picowatts of energy — an efficiency of 230 percent！ That’s a remarkable achievement， but still a miniscule amount of light. For now， there really isn’t any practical application for a super-efficient 70-picowatt bulb， but according to PhysOrg， the researchers hope the breakthrough could open the door to new advances in energy-efficiency electromagnetic communication.

Read more： MIT Researchers Create More Than 100-Percent Efficient LED Light | Inhabitat - Sustainable Design Innovation， Eco Architecture， Green Building