Environment

How Low Can A New Solar Cell Go? Ask The US Air Force!

September 9th, 2020 by  


A couple of years ago, everyone was all excited about new solar cell technology that could result in costs as low as 20 cents per watt. Yes, 20 cents per watt. There was just one problem. The new device was developed by the Energy Department’s National Renewable Energy Lab, which needed a new investor to lead it across the Valley of Death that separates lab work from the shelves of your local hardware store. If you’re guessing that the US Air Force has just come to the rescue, run right out and buy yourself a cigar.

The USAF is pumping dollars into a new solar cell manufacturing system developed by NREL, which yields space-quality solar conversion efficiency at a down to Earth cost.

The Long Road To A New Solar Cell

The new solar cell first popped up on the CleanTechnica radar back in 2018, when NREL started talking up the idea of taking ultra-efficient, ultra-expensive III-V solar cells, and figuring out how to keep the efficiency up while bringing the cost down.

That’s literally, down to Earth. The III-V solar cell is a complicated gizmo reserved for space applications, and NREL was especially intrigued by its use for solar panels on the 2003 Mars rover. They figured the same thing could be done on your rooftop, if the price was right.

They zeroed in on the manufacturing process and decided to ditch the conventional method in favor of an elderly, underused technology called hydride vapor-phase epitaxy (HVPE).

How come nobody else thought of that? Well, HVPE was not on the top of many peoples’ minds for solar cell manufacturing in the 21st century. The technology had its heyday in the 20th century, up until the 1960s, when its seams began to show.

“Part of the reason people stopped using HPVE was because it did a really poor job of fabricating complex structures with multiple layers, and the whole process was a cumbersome routine of swapping layers and chemicals in and out of the same chamber,” CleanTechnica explained in a 2018 article on the topic.

Game on! The NREL team fixed that problem by redesigning the system to use two chambers instead of just one, which sped up the process considerably. The time frame for popping a III-V solar cell out of the oven went from 1-2 hours down to two minutes.

As for conversion efficiency, the new solar cell weighed in at 25.3%, pretty close to the 28.8% achieved by the Mars rover solar cell.

US Air Force To The Rescue!

NREL was so excited about its new HVPE system that they gave it a D for Dynamic. The new D-HVPE method is not the end of the story, though.

NREL was still working on a quick way to integrate aluminum into the system, which is needed to “grow” the two semiconductors in a III-V solar cell. They got that done by teaming up with the North Carolina firm Kyma Technologies.

So far, so good, except for that little thing about getting the lab work scaled up for commercial applications. Previously the work was funded through the Energy Department’s Solar Energy Technologies Office and its ARPA-E high risk, high reward funding agency.

To get to the next step, NREL called in for air support. Earlier this week the lab announced that the US Air Force Research Laboratory will play the angel and invest in a new reactor to make III-V solar cells. The pilot scale device will pump out solar cells that meet the industry standard of 6″ in diameter, a big step up from the 2″ size achieved by the lab-scale reactor.

Kyma will continue as partner and design the new reactor, and the New York firm Ceres Technologies will build it.

DOD Hearts New Solar Cell Technology

The implications for expanding the rooftop and building-integrated solar market are enormous, considering that low cost, high efficiency, and lightweight are all packed into one bundle. The new solar cell gives new hope for roofs, facades, and other building elements that can’t support conventional solar panels.

That 20 cents-per-watt mark is out of range, but the Department of Defense is eyeballing the new solar cell. The new pilot-scale reactor is aimed specifically at proving that the new III-V solar cell can provide renewable energy at a competitive cost in the context of DOD purposes.

That leaves us with the question of why DOD, through the USAF, is determined to push the US into a low cost renewable energy future even as the Commander-in-Chief* champions the cause of fossil fuels (well, except that coal has dropped off the list) and makes mincemeat out of global decarbonizaiton policy.

Why, indeed. There are any number of reasons why the US Armed Services, which have accumulated generations of innovation under their belts to achieve global domination, would be interested in the latest new cutting edge energy technology.

That basic foundational interest in new technology is fraught with another layer of urgency in the era of climate change. DOD has long recognized climate change as a disruptive threat, and not just because it disrupts food supplies, water resources, and entire populations.

Climate change also has a direct impact on military readiness, as it interferes with training opportunities due to excessive heat, dust, or rain.

The US Navy is particularly vulnerable to climate change, considering that its key facilities are under threat from rising sea levels. Not helping are the additional challenges of patrolling high seas that have been newly freed from ice and providing humanitarian aid to populations impacted by climate change.

USAF Pushes The New Solar Cell Envelope

The USAF has been front and center in the public eye as an early adopter of ground-mounted solar arrays, rooftop solar, and mobile solar systems during the Obama administration.

Those investments may have slowed under the current Commander-in-Chief, but the Air Force Research Laboratory has been humming behind the scenes.

In fact, over the past several years the lab has stepped up to a whole new level. During the Obama administration the lab supported a raft of Earth-based clean tech, from energy storage to quantum dots. Now they’re doing this thing called SSPIDR for “Space Solar Power Incremental Demonstrations and Research project.”

Based at Kirtland Air Force Base in New Mexico, SSPIDR is aimed at “developing space-based solar power transmission capability using high-efficiency solar cells to collect the sun’s energy, convert it to radio frequency, and beam it to earth.”

Got all that? Good! The idea of beaming solar energy down from outer space has been intriguing researchers for a few years now, but the DOD is more interested in the implications for national security.

“Energy is a strategic enabler and potential vulnerability for our nation and our Department of Defense. To ensure DOD mission success we must have the energy we need at the right place at the right time,” explains the Air Force.

“Providing uninterrupted, assured, and agile power to expeditionary forces operating in unimproved areas such as forward operating bases would provide an advantage to U.S. and allied forces,” they continue.

Interesting! DOD has been ringing the alarm bells over climate change and the need for more sustainable, portable energy for the past 10 years or so, and it seems that the current presidential administration has not dampened its eagerness to shepherd in the sparkling green future.

After all, presidents come and go…

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*Developing story.

Photo: “NREL researchers have pioneered a method of lower-cost manufacturing for extremely efficient III-V solar cells, such as the flexible gallium arsenide solar cell shown here, that have been too expensive to use anywhere but in space applications.” Photo by Dennis Schroeder, NREL 
 


 


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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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