As efficient as our solar panels are when the sky is clear, they turn out to be practically useless once the first drops of rain fall. This could soon change thanks to a hybrid cell capable of harvesting the energy of sunlight and raindrops.
A hybrid cell capable of harvesting energy from raindrops? The key component of the system is a triboelectric nanogenerator (or TENG), a device that creates an electrical charge from the friction of two materials – as with static electricity. TENGs can draw energy from car tire friction on the road, clothes rubbing against each other, or in this case the rolling motion of raindrops on a solar panel. The idea here is be to make keep our photovoltaic panels working in all weathers.
While the idea of using TENGs is not completely new, the challenge has been to develop a system that is neither too complex nor too cumbersome. Here, two polymer layers were used to form a TENG over a photovoltaic cell. Using standard DVD fingerprints, researchers at Soochow University in China added grooves to a polymer to improve its energy efficiency. In the tests, the textured polymer layers acted as a mutual electrode for the TENG and the underlying solar panel, driving the energy between the two devices as the raindrops hit.
The extra layers being transparent, sunlight could still be captured. Another advantage: the TENG protects the solar cell by acting as a watertight barrier preventing water from entering the silicon. The surface of the electrode also considerably suppresses unwanted reflection of light.
Thus, by attaching a transparent nanogenerator to a silicon solar cell, researchers have designed a compact device that captures solar energy in sunny conditions, but also the mechanical energy of raindrops falling from the sky. The next challenge will be to increase the amount of electricity generated to consider commercial use. Remember that it also rains at night. So, one day, we could run solar farms 24 hours a day, whatever the weather, adding a huge boost to the potential of renewable energies.