Innovation: ENEA patents self-cleaning technology for solar power mirrors

Researchers at the ENEA Portici Research Center (Naples) have patented a low-cost process to make self-cleaning solar mirrors without affecting their reflective properties, reducing the cost of the electricity generated and water consumption for cleaning operations.

 “The process allows to address a problem unsolved until now, thanks to a coating process reducing the wettability of the mirrors, i.e. the ability to come into contact with water, preserving their optical properties and possibly performing a protective function from erosion and corrosion", said project coordinator Anna Castaldo, researcher at the ENEA Energy and Thermal Storage Laboratory and author of the patent with Emilia Gambale and Giuseppe Vitiello.

Solar systems are generally located in semi-arid areas where the radiation is abundant and they get dirty with sand, dust, pollen and bird droppings; regular cleaning, essential to maintain efficiency, contributes a significant portion in the cost of the electricity generated, making water consumption one of the factors determining the profitability of the systems.

 “To overcome this problem we thought of changing the 'skin' of the solar mirrors using a very simple technique such as the low-pressure spray of a material from the automotive sector and a well-established supply chain like painting. In fact, like solar mirrors, cars are exposed to the elements, but are usually washed without this causing wear. Hence the idea of selecting some components of their paints with the suitable optical requirements, and using them to coat the mirrors", said Castaldo.

 “The line of products for which a change of intended use is proposed is already present on the market and the high volume of air at a low pressure spray technique, known as HVLP, is widely used as it is eco-sustainable, since it doesn’t present the problems given by polluting propellants. This means that there is a well-established industrial supply chain that implements it, such as that of automotive paints, and that the entire process can be easily used by interested companies", said Castaldo.

The invention is applicable in all those sectors, such as photovoltaics, anti-ice/frost and outdoor lighting, where modulation of wettability combined with transparency and resistance to bad weather is required.

The patent, which has a high technology transfer index on new mirrors (TRL 7-8), also covers the possibility of retrofitting, i.e. application on solar mirrors already installed.