On average, solar panels produce only about 10% of their summer output during the cold winter months. This is due to several factors. Winter days are shorter, with the sun rising later and setting earlier, leaving less time for panels to generate energy. The low angle of the winter sun, which often blinds drivers, also reduces the intensity of sunlight reaching the panels. Additionally, cloudy skies scatter sunlight, creating diffuse light that struggles to hit the solar panels at the optimal angle for energy production.
The vertical solution
Rebecca Saive, a researcher at the University of Twente, believes the solution lies in rethinking how and where we install solar panels. “We shouldn’t be putting solar panels at a tilt or even flat,” she says. “In winter, vertical installations can actually produce more energy.” In fact, placing solar panels on façades rather than or in addition to rooftops could be a game changer, especially in cities where space available space can be limited.
“Of course, the ideal situation is different for every house,” says Saive. But in general, with vertical solar panels, the winter yield increases more than the summer yield decreases. “We’re flattening the curve,” she explains. This method produces more energy when we need it the most. “To power your heat pump for example.”
Revolutionary Materials
But Saive’s vision goes beyond just changing the angle of solar panels. Her team is developing a material that changes how we harvest light. It’s received the complex name ‘Free-Space Luminescent Solar Concentrator’ or FSLSC for short. This material can absorb sunlight from all angles and redirect it to solar panels mounted elsewhere, such as fences or walls.
The material in action: the light only reflects in a certain direction. Viewed obliquely, this causes the red material to turn black.
It doesn’t matter whether the light comes from the high summer sun, the low winter sun, or light diffused by clouds. This new material captures photons from any angle and ensures they all leave the material at a specific, desired angle. “It ensures that the light reaches solar panels, even in less-than-ideal conditions.”
Creative applications for a brighter future
This technology is a smart and flexible way to use solar energy. It can be used in many places, like along roads, in greenhouses, on farms, or in cities. For example, tall buildings could bounce sunlight onto parking areas with solar panels. There are so many ways to make solar energy work better and look good, making it easier to use in lots of different settings.
In an article published together with Anne Rikhof, Shweta Pal, Leonie Horst and Jelle Westerhof, Saive shows how their material can help solar panels make more energy, especially in winter1. Vertical panels in combination with this material can capture light that would otherwise be wasted. It could boost winter energy production by up to 60% compared to normal solar panels. This makes solar panels more efficient in winter and makes sure they deliver a more consistent energy output year-round.
About Rebecca Saive
Rebecca Saive is a professor in applied physics in the Inorganic Materials Science Group. She started working at the University of Twente in January 2018. She is one of the Featured Scientists of the University of Twente. Her innovations also earned her a spot on MIT’s prestigious global list of Innovators Under 35 in 2020, a list that in previous years has boasted such names as Mark Zuckerberg and Nobel Prize winner Novoselov. She received an NWO-Vidi grant in 2020 and she is a steering committee member of SolarLab NL.
