Norway wants to expand what is already the world's largest vertical rooftop solar power system. 

After a successful launch in May, the installation on the country's national football stadium "is going to be at least doubled - in the first run," the head of technical operations at Oslo's Ullevaal stadium Espen Aasen told CGTN.

Currently, more than 1,200 vertical solar panels cover a quarter of the national football stadium. "The motivation is for the environment," Aasen adds.

And for now the results are promising. In summer, the panels generated about a third of the stadium's energy needs - a share that is set to increase this winter when the system fully unfolds its potential.

"With this installation here we generate more energy during the winter time which is highly valuable, it's when the energy is more expensive and more needed here in Norway," says project builder Trygve Mongstad.

Mongstad, the founder and CEO at Over Easy Solar, adds that the vertical and bifacial solar panels on the stadium achieve a higher output not only when getting energy from the low-lying winter sun but also at certain times on a summer's day.

"We basically have too much solar energy in the middle of the day in summer time. And vertical panels - they generate more in the morning and in the evening," Mongstad says.

It would make sense that solar panels generate the most electricity in summer. But this is actually not the case as panels tend to overheat – meaning the higher the air temperature, the less voltage generated. 

But while the sun might not be hot in the winter, it does still shine, meaning one solution is to adapt panels to stand vertically to catch the rays.

Whenever excess solar energy is produced, it is usually exported to other areas or goes to waste. To counteract this trend, Trygve Mongstad's solar technology company has been developing its off-peak power solutions featuring silicon heterojunction cells - a new generation of solar cells that have proved more efficient in energy conversion than previous cells.

"We're collaborating very closely with some Chinese companies now," Mongstad told CGTN. "Basically because this cell technology is the best for vertical bifacial solar installations."

It's hoped the expansion of the stadium roof project will soon be given the go ahead. Meanwhile, Mongstad's concept of vertical solar panels armed with Chinese technology is gaining popularity abroad – with several buildings requesting their own versions of rooftop solar fields.