The team of researchers from the Ocean University of China in Qingdao and Yunnan Normal University in Kunming have devised the method using a highly efficient dye-sensitized solar cell, coated with a thin film of graphene, on a transparent backing of indium tin oxide and plastic.
The technology works on the fact that rainwater isn’t pure: the droplets contain positively-charged salt ions of sodium, calcium and ammonia. When raindrops sits on top of a layer of graphene, it creates a ‘pseudocapacitor’, and the potential energy difference between the two layers is strong enough to generate an electric current.
Graphene, known as wonder material is extracted from graphite, the material used in pencils. Back in 2013, one micrometer-sized flake of graphene costed more than $1,000, which made graphene one of the most expensive materials on Earth. However, prices are now down approximately $0.10 per gram.
However, the new ‘all-weather’ solar cell is still on a proof-of-concept stage. The primary challenge for the researchers is the relatively low concentrations of salt ions in rainwater compared to the salt solutions prepared in the lab, making it difficult for the panel to produce large quantities of electricity.
These newly designed solar panels could provide a boost to solar cell technology which currently only works when there is ample sunlight. In regions where climate is dominated by clouds and rain, an all-weather solar panel could provide a clean form of energy that is not possible with existing technology.
