Regular readers of ExtremeTech know that battery tech always seems to be standing just at the base of a mountain of progress, but can never quite start the climb. There are always new advancements, but never ones that seem like they’ll be put into consumer products anytime soon. So, it may be time to look for alternative power sources for mobile devices, perhaps a solar-powered smartphone screen.

Let’s face it, there is a lot of new and awesome battery technology on the horizon, but almost all advances seem to stay right on that horizon, out of reach of the general consumer. Meanwhile, solar power, though underutilized by society, has been around and kicking for quite some time. However, we haven’t harnessed it in the vast majority of devices — our phones and tablets use lithium-ion batteries, our Wiimotes use standard AAs, and we plug our laptops into a wall. Startup SunPartner Group, located in France, wants to change all that, and aims to attach a smartphone screen that collects solar power and delivers it to the phone. In fact, a transparent overlay has already been developed and is currently undergoing testing.

SunPartner isn’t the first tech company to step outside one sunny day, look up, and figure there has to be a way to use the Sun. In 2009, Samsung released a phone equipped with solar cells called the Samsung Crest Solar. It wasn’t a smartphone, and was actually considered a budget phone due to its low price of around $60. The phone was released in India, and was reportedly able to provide around 5-10 minutes of talk time power from around an hour sun.

The phone didn’t quite take off, in large part due to the solar cells being placed on the back of the phone. This meant that when sitting outside at a restaurant or cafe, for example, users had to place the phone face down on a table, missing their alerts. By placing the solar cells into a transparent screen, SunPartner has figured out how to allow people to use their phones while they are harnessing the power of the sun, rather than having to place them face down on a table and miss juicy texts and alerts.

You might think SunPartner would have to use transparent solar cells to accomplish this feat, but the company has found another solution. In its overlay, it alternates thin-film solar cells and standard transparent film. Rather than looking like a horizontal striped shirt, though, SunPartner employs the uses of small lenses that essentially bounce the image from underneath the opaque solar cells and help the image spread across the entirety of the screen. The lenses are also used to help focus the solar rays toward to the solar cells. At the moment, the prototype screens are around 82% transparent, with a transparency of 90% predicted for the future.

Currently, the tech is so cheap that it only adds a cost of around $2.30 per phone, and if used properly — leaving your phone face up on a table during a sunny day rather than in your pocket — can extend the life of a smartphone by around 20%, and can maintain its charge while idle in the sun. While 20% won’t change the world or free up electrical outlets at coffee shops, that would be the first real, major increase consumers will have received in a seemingly endless amount of years.

The overlays are estimated to hit the market sometime next year, with recognizable names like Nokia to incorporate the tech into its devices.

Now read: IBM Research uses supercomputer tech to “harness the energy of 2,000 suns”