The sun's rays are soaked up by solar technology to cause a voltage. Some materials can run in reverse, producing power when they heat up in the night sky.
A team of engineers in Australia have demonstrated the theory in action, using the kind of technology commonly found in night-vision goggles to generate power.
The prototype only produces a small amount of power, and is unlikely to become a competitive source of renewable power on its own, but it could harness the small amount of energy provided by solar cells cooling after a long, hot day.
Humans have developed an artificial process in order to convert the sun's energy into electricity, according to a physicist from the University of New South Wales.
In that sense, the thermoradiative process is similar; we are redirecting energy from a warm Earth into the cold Universe.
By setting atoms in any material that is moving with heat, you are forcing their electrons to generate waves of low-energy radiation.
This electron-shimmy has the potential to kick off a slow current of electricity. The only thing needed is a one-way electron traffic signal.
The combination of elements makes a diode able to shuffle electrons down the street as it slowly loses its heat to a cooler environment.
The mercury cadmium telluride is used in this case. It is well understood that the ability to absorb mid- and long-range IR light and turn it into a current is already used in devices that detect it.
What hasn't been clear is how this particular trick might be used as a power source.
The power density of 2.26 watt per square meter was generated by one of the tested MCT photovoltaic detectors, which was warm to around 20 degrees Celsius.
It is not enough to boil a jug of water for coffee. You would probably need enough panels to cover a few blocks.
It is still very early days in the field, and there is potential for the technology to develop significantly further in the future.
The demonstration we have with the thermoradiative diode is very low power. Ned Ekins-Daukes, the study's lead researcher, says one of the challenges was actually detecting it.
The theory says it is possible for this technology to produce about a tenth of the power of a solar cell.
It might be worth the effort to make more typical photovoltaic networks so that they continue to top up batteries long after the sun sets.
Engineers have entertained the idea of using the planet's cooling as a source of low-energy radiation for a while now. Different methods have different results.
We can come up with a suite of technologies capable of wringing every drop of power out of just about any kind of waste heat by testing the limits of each and fine- tuning their abilities.
This technology could potentially harvest that energy and remove the need for batteries in certain devices, according to Ekins-Daukes.
That isn't something where conventional solar power would be a viable option.
The research was published in a journal.
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