A couple of green entrepreneurs in South Korea are aiming to make solar power beautiful enough for the everyday smartphone user. The people at Yolk, a solar design startup in Seoul launched in January this year, have been working on making a portable solar charger as thin, powerful, and aesthetically appealing as possible.

Their newest product, Solar Paper, fits snugly between the pages of a notebook. It claims to pack the most punch for its size, with its power output on a sunny day even matching that of a wall charger. Yolk says Solar Paper is 85 percent smaller and 75 percent lighter than its closest competitor, and weighs 4 ounces compared to its rival’s full 1 pound.

Yolk was created by 31-year-old Korean designer Chang Sung-un, who won Red Dot and IF awards during her MFA studies in object design at the top-echelon Art Institute of Chicago in the US. She chose the name for her solar power brand to recall the yellow of eggs, which you can cook sunny side up (get it?). The startup’s other explanation is that yolk provides energy to fetuses, so metaphor choice is yours. The startup exists within Chang’s larger design company, Nolla, founded in 2012.

Chang, the startup’s co-founder and CEO, says Solar Paper fundamentally represents Yolk’s goals for synergy between technology and design – beyond good looks, design needs to be functional. She saw that other portable solar chargers are mainly targeted to outdoor activities like camping, but they lacked that pristine chic befitting everyday use by an urbanite.

She saw that the solar power segment was still a red ocean with low entry barriers, but design was still lacking. “Solar tech is a niche market now, but I saw potential and felt design can do something,” she tells. “I wanted to see what kind of impact I could make on the world.”

Yolk has fans among backpacking enthusiasts in North America and Australia, the technologically curious in Asia, and the environmentally conscious in Germany. But Chang wants to show electronics users everywhere that solar power is “not just for tech geeks or outdoor people” – it can be relevant even in their daily lives.

The gadget is sure to catch on with outdoor activity lovers who are already keen on solar technology and would appreciate the lightweight portability, but she wants to embrace all smartphone users: “With the right design and right portability, it can be something that solves the problem for the majority of people who suffer battery issues […] I think this project will not affect the way people use smartphones, but that it will be a start for people to think solar energy can be used in their everyday life. That’s my wish.”

How it works

The user experience is simple: Connect up to four panels together by their magnets, hook the device to the main panel with a USB cable, and track the power current level on the main panel’s small LCD screen, which boasts 95 percent accuracy. It can charge anything with a USB cable, from GoPros, external batteries, and walkie-talkies to smartphones and even iPads. It claims to have the top efficiency of its size segment, so 20.8 to 22.8 percent of sunlight hitting the panel gets churned into usable juice. Industry standards are around 11 to 15 percent efficient.

Solar Paper is packaged in sets of two (5W), three (7.5W), and four (10W) panels (and a six-panel 15W set possibly in the works), with the two-panel set folding up to 9 cm x 19 cm x 1.1 cm. Yolk claims the two-panel, 5-watt charger should fully charge an iPhone 6 or Galaxy S3 in 2.5 hours on a sunny day, and more panels mean a quicker charging time.

The magnets on each corner let the panels stick to each other as well as to metal objects like poles and tables, and Yolk says it also helps reduce wear and tear compared to other materials after folding and unfolding the panels multiple times. Users can string the included silicon ring connectors through the holes in each corner of the panels to hang them on a backpack.

Another perk is an “auto-comparison technology” feature, which Yolk claims is the first of its kind. Smart devices stop taking in power if the current is too low, which would happen any time the sun is blocked like when it hides behind a cloud. Solar Paper monitors the energy level and automatically resumes powering up without you having to replug the USB cable.

Similarly, when it’s way too sunny out, the temperature sensor embedded in the panels will limit or cut the incoming current to protect the printed circuit board.

Solar Paper takes a page from Yolk’s debut charger Solarade, a simple panel launched last year that comes with a nifty stick that helps the users gauge the sun’s position so they can place the panel at the best angle. With its success of more than 1,000 backers on Kickstarter, Chang says it was insightful for the team to see that users with zero tech knowledge could still figure it out and love the product – enough that many have followed on to their next product. Using the same sturdy, lightweight FR4 fiberglass material of Solarade, the Yolk team then focused on making the product sleek and portable, teching it up with the small LCD screen. They presented the new, thinner prototype – dubbed Solar Page – at CES earlier this year as a hole-punched insert to diary planners, and later tweaked it to be a standalone to appeal to the masses. Voila, Solar Paper.

The material isn’t flexible, but it’s coated with a protective film to weather drops and scrapes. It’s also IP64-grade water-resistant, meaning it’s dust-proof and splash-proof. Backed by a limited six-month manufacturing warranty, Solar Paper is designed to last five years under good care, compared to similarly sized products that lose their mojo after just three months.

One caveat is that Solar Paper doesn’t bode well for conducting power in wintry or rainy weather, nor does it absorb artificial light indoors well enough to charge a smartphone. Be aware that it is not fully waterproof – not that you should be trying to charge electronics in the rain — and while the panels are weather-resistant, the USB port is susceptible to corrosion. Yolk says it’s currently seeking a more robust USB solution, but for now users will have to be careful.

Also, you should not keep your electronic device in extreme direct sunlight, but Solar Paper can’t help you there – you’ll just have to put it under the panels or another object as it charges.