As useful as modern solar panel technology is in the human quest to switch to renewable energy, such panels cannot generate electricity at night.
Now, new research suggests it might be possible to design panels that can operate around the clock.
Under optimal conditions at night, these specially designed photovoltaic cells can generate up to a quarter of the energy they generate during the day, according to research.
To achieve this, thermal radiation elements are needed – devices that generate energy through radiation cooling when infrared or thermal radiation leaves the element and produces a small amount of energy in the process.
Thermo-radiation elements are already being tested in areas such as manufacturing and mechanical engineering where they are used to convert waste heat, such as the high temperatures generated by engines.
In the case of a solar panel at night, the use of such cells is the way to use this process.
“We thought if we take one of these devices, put it in a warm place and point it up to the sky,” says electrical engineer and computer scientist Jeremy Munday of the University of California at Davis.
To achieve this effect using infrared radiation, we need different types of materials for conventional solar panels, which tend to focus on visible light.
The next step is to figure out what combination of materials and electronics can create an effective panel that can use the night sky and its surroundings as a radiator.
“A typical solar cell generates energy by absorbing sunlight, which causes voltage and current to appear on the device,” says Munday. “In these new devices, light is emitted and current and voltage are going in the opposite direction, but you still generate energy.”
“You have to use different materials, but the physics is the same.”
According to the researchers' calculations, solar panels can produce up to 50 watts of electricity per square meter under ideal conditions.
This is an idea that is being explored by several research groups. Last year, we saw an experimental system created by scientists at Stanford University that also used the thermal imbalance between the night sky and the Earth to generate electricity from infrared radiation.
While there is a long way to go to properly scale this technology and apply it in practice, Mandei and his colleagues are currently developing prototypes, but it is a potentially relatively cheap and inexpensive way to keep solar panels operational 24 hours a day.
“Deep space offers an intriguing, low-temperature heat sink capable of providing power night and day through the intelligent use of photonics, optics and materials science,” the researchers conclude in their paper.
The study was published in ACS Photonics.
