A classic image of solar panels shows rows of deep blue rectangles, glinting in the sunshine. However, in reality solar panels are exposed to whatever comes down from the sky – 365 days a year, often for 25 years or more.
Depending on where the panels are installed, this could mean they’ll just be sprinkled with rain from time to time. Or it could mean they’re pounded by storms, hail, snow, high winds and freezing temperatures. And let’s not forget hot temperatures from the sun!
So, how do you protect solar panels from decades of exposure to the weather? ExxonMobil’s solution is to bake them in our ethylene vinyl acetate (EVA) resin – Escorene Ultra – specially developed for solar panels.
A solar panel is made up of several layers, like a deck of cards. At the heart of the panel are the photovoltaic cells. Made from wafer thin sheets of silicon, these delicate cells turn sunlight into electricity. But for photovoltaic cells to work they need to be sealed in and protected from the weather.
Many of the components in a panel are conducting electricity, so first and foremost Escorene Ultra keeps them dry. For panels with working lives of over 25 years, Escorene also had to be durable.
To strengthen the panels, the resin was designed to have adhesive qualities. During manufacturing, the panel is baked in a vacuum oven, causing the resin to stick the layers of the panel together and seal the photovoltaic cells in.
To make sure as much sunlight as possible passes through the protective shell into the photovoltaic cells, Escorene Ultra had to combine being durable and strong with being highly transparent. “That’s where our technology comes into the picture,” says Linda van den Bossche, global advisor on polymer film at ExxonMobil’s Antwerp Polymers Plant. “The specific design of the polymer molecules and the level and type of comonomer resulted in a very high clarity product.”
ExxonMobil has been manufacturing ethylene vinyl acetate copolymers since 1979, and first developed Escorene for use in solar panels in the 1990s. The resin’s durability has withstood the test of time – and the weather. “The use of Escorene EVA as an encapsulant sheet is a proven technology,” says Linda. “It has been demonstrated over the real life of a panel – that’s more than 25 years.”
“Due to the low light absorption and minimal layer interference reflectance of Escorene Ultra, there is minimal solar light loss, and thus energy loss,” explains Michael De Ketele, process engineering and quality assurance section head at the plant.
“So while the photovoltaic cells are protected from the weather, the sunlight still shines in.”