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Published on April 29th, 2016 | by Tina Casey


Solar-Powered Drones, Coming Soon To A Sky Near You

April 29th, 2016 by  

The Intertubes have been buzzing with news that the company Alta Devices has hit the 31.6% mark for solar cell efficiency. That’s a new record for devices of its kind. What’s even more significant is that Alta’s improved power-to-weight ratio makes the new device ideal for airborne applications, including drones.

new solar cell efficiency record

The Perfect Solar Cell For Drones

According to Alta’s press materials, the new record applies to the company’s dual-junction technology, and the mark of 31.6% has been confirmed by NREL, the National Renewable Energy Laboratory, and has now updated its efficiency-records chart.

NREL has previously confirmed a number of other Alta records, including a conversion efficiency of 30.8% for a dual-junction solar cell in 2013.

Alta’s press materials don’t give away much in terms of pinpointing where the solar cell tech improvement took place. For both devices, the explanation is the same. The company took its foundational technology, a single-junction gallium arsenide solar cell, and built up from there:

The company’s new dual junction technology…implements a second junction (or layer) with Indium Gallium Phosphide (InGaP) as the absorber on top of the base cell. Because InGaP uses high-energy photons more efficiently, the new dual junction cell generates more electricity from the same amount of light than a single junction device.

For those of you new to the topic, gallium arsenide (GaAs) is the workhorse of the solar tech field, with a history that goes back to the 1970s. Alta favors the material for its moisture resistance and durability among other factors.

If you have any insider-y information about that mystery improvement, leave us a note in the comment thread. Meanwhile, if you ever wondered exactly how next-generation solar cells are fabricated, Alta has created an animated video that spells out its process and you can find it on YouTube under the title “How Alta Works.”

Drones Rule, Solar Drones Rule More

Compared to the previous record of 30.8%, Alta’s latest achievement of 31.6% may seem little to show for three years of work. However, that power-to-weight ratio makes a huge difference in the range of applications.

In a high-altitude, long-endurance drone, for example, Alta states that its thin-film solar material would need less than half the surface area of conventional thin-film solar material. It would also provide the same amount of power, and it would weigh only one-fourth as much.

That does free up a number of new design options. The obvious one would be to design smaller, lighter drones. Drones powered by the new Alta cells could also carry additional payload, batteries, or both.

Solar power combined with energy storage also provides drones with more air time, compared to drones that need ground time every few hours for recharging or refueling (check out the Army’s venture into thermoelectric drones for another option).

Alta isn’t the only company that has caught on to the possibilities. Earlier this year, The Guardian noticed that Google is deploying a solar-powered drone in its semi-secret James Bond-ishly titled Skybender project. Facebook is nipping at its heels in the solar-powered drone department. Both companies aim to use the drones as airborne wireless transmitters in promotion of universal Internet access.

In an email circulated a couple of days before the announcement, Alta also makes the case for using its new solar cell in manned (or woman-ed, as the case may be) aircraft as well:

…Alta’s breakthrough in the increased power to weight ratio could have enabled the widely discussed Solar Impulse airplane to add a second pilot, fly 10% faster, sustain a 50% better rate of climb, and fly 10 kilometers/6.2 miles higher.

In case you’re wondering what Solar Impulse is, that’s the groundbreaking aircraft powered exclusively by the electricity generated by on-board solar panels.

Solar Impulse was on a ’round the world flight last year when battery issues cropped up, forcing it to make an extended pit stop in Hawaii. The aircraft just resumed flight again last week. It made a three-day, zero-fuel flight to San Francisco, from whence it will continue on to the next leg of its journey.

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Image (screenshot) via Alta Devices. 

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About the Author

specializes in military and corporate sustainability, advanced technology, emerging materials, biofuels, and water and wastewater issues. Tina’s articles are reposted frequently on Reuters, Scientific American, and many other sites. Views expressed are her own. Follow her on Twitter @TinaMCasey and Google+.

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