The World's #1 Renewable Energy Network for News, Information, and Companies.

Boosting Solar Cells with Nanowires

Solar module makers are struggling even as cost points are at a bare minimum (and arguably unsustainably so) — and yet lower prices persist, especially in lower-end crystalline silicon (c-Si) modules. However, there is still improvement to be made in efficiency, says Dave Epstein, CEO of Sol Voltaics. More efficient panels can both be sold at higher prices and installed with fewer panels to reduce the cost profile of an entire project. The economics improves for everyone.

"We are exiting the era of cost reduction," he said, "and entering the era of efficiency." 

Research began more than a decade ago at Lund University in Sweden, and is now being launched as a startup: technology that selectively adds gallium-arsenide (GaAs) nanowires to solar panels, boosting their efficiency by up to 25 percent, the company claims. That improvement directly translates to better output and lower prices, improving the economics for the module manufacturers. It also reduces total installed costs by 15-20 percent (fewer panels with increased efficiency, even if they cost a little more), which improves the economics for everyone, Epstein said.

A solar module with 17 percent efficiency at $0.60/W, with Sol Voltaics' technology, could transform into a 22 percent efficiency module costing $0.75/W, according to the company. In the field, that turns a 100-MW installation into a 125-MW installation.

Nanomaterial additions to solar substrates typically have been produced through an epitaxial process, slowly grown in a furnace as crystals either in place on a substrate or separated and sorted separately in a batch process, neither cost-effective nor scalable. The company's Aerotaxy process suspends the active materials in carrier gas streams in a reactor, where precise control of temperature, pressure, flow rates, and mix causes them to grow much faster than epitaxial processes, and with reliable size and consistency (around 1-2 μm tall). They are then suspended and stored in a liquid. That liquid, called SolInk, is deposited onto the solar silicon substrate via an inkjet-type process, followed by a polymer layer and transparent conductive oxide (TCO) layer.

One trick to solve is managing the nanowire alignment. Two methods can be applied to solve that, Epstein noted: one is an electric field, another is chemical self-assembly. Coyly, he said "both have yielded promising results, but we have our direction."

The result is what the company and Lund University described in a Science paper earlier this year: an effect called "wave-concentrated PV," where the nanowires capture and concentrate lower-frequency light waves — a separate active layer, each acting as a separate solar cell. (GaAs is already used in much higher-efficiency cells for niche applications where cost isn't the key differentiator, such as satellites.) Longer-wavelength light goes through the transparent conductive oxide (TCO) layer to be converted by the silicon. They showed (and the Fraunhofer Institute confirmed) that indium phosphide (InP) nanowires covering just 12 percent of the substrate surface produced a solar cell with 13.8 percent efficiency. Epstein says the ideal coverage range is between 10-15 percent, with 12 percent the initial sweetspot; "somewhere above 15 percent you get diminishing returns," he said.

For module manufacturers, all they'll need is "a couple of pieces of equipment" that are "rather inexpensive," for deposition and the TCO layer, adding only a penny or two in capital expense to the line, Epstein said.

Others have tried to apply nanoparticles (nanotubes, nanowires, quantum dots), but not with active layers, Epstein said. "People know there's a use for them, but so far nobody has been able to crack how to make them cost-effective," he said. "Honestly there's been great research, but it's far from commercializable."

The company has raised $11 million to date from private investors including Industrifonden, Foundation Asset Management of Sweden, Teknoinvest, Provider, Nano Future Invest and Scatec Energy of Norway; it's also received public funding from others including the European Union, Vinnova, and Nordic Innovation Center. The company says it will raise $10-$20 million this year.

This year Sol Voltaics wants to continue to work the Aerotaxy process and pilot equipment. Next year the plan is to develop production-quality equipment scalable to a 100-MW machine, and tie up with a module manufacturer (or more), and partner with an equipment manufacturer familiar with making tools for solar PV manufacturing. By 2015 the company hopes to have a module-maker customer in pilot production, delivering them to market in small (~10 MW) quantities. Full-scale production is planned for 2016, defined as one or more 100-MW lines running their equipment.

RELATED ARTICLES

Intersolar Europe 2015: Spirits Up, Stats Down

William P. Hirshman, Contributor Intersolar Europe, billed at the world’s leading exhibition for the solar industry, is indeed big. But Intersolar Europe 2015, one of five Intersolar-branded gatherings around the globe each year, was not as large as the an...
US Capitol

Republicans and Democrats Back Bill to Level the Playing Field for Renewable Energy

Vince Font, Contributing Editor U.S. Senators Chris Coons and Jerry Moran are leading a bipartisan effort to reintroduce tax code legislation aimed at leveling the playing field for renewable energy investment. The Master Limited Partnerships Parity Act w...
Solar thermal desalination

Solar Thermal Desalination Now Underway in Water-hungry California

Susan Kraemer, Correspondent Regional droughts are being exacerbated by climate change, which is mostly caused by what is tasked with bailing them out — fossil fuels. Israel, Australia, and now southern California have all turned to expensive energy-gu...
Memo pad on table

IRS Issues Solar Tax Equity Memo Stating the Obvious

David Burton and Richard Page, Akin Gump On Friday, the IRS issued a heavily redacted Chief Counsel Advice (“CCA”) memorandum, that addresses the intersection of solar investment tax credit partnership flip transactions and the wind production tax credit part...
Jim is Contributing Editor for RenewableEnergyWorld.com, covering the solar and wind beats. He previously was associate editor for Solid State Technology and Photovoltaics World, and has covered semiconductor manufacturing and related industries, ...

CURRENT MAGAZINE ISSUE

Volume 18, Issue 3
1505REW_C11

STAY CONNECTED

To register for our free
e-Newsletters, subscribe today:

SOCIAL ACTIVITY

Tweet the Editors! @megcichon @jennrunyon

FEATURED PARTNERS



EVENTS

SAP for Utilities

The SAP for Utilities conference is the most comprehensive SAP for Utili...

Training: Preparing for Rule 21 - SPI 2015

What: Rule 21 Training When: September 16th @ 4:30-5:30pm Wher...

Training: NEC 2014, AFDI, & Rapid Shutdown - SPI 2015

What: NEC 2014, AFDI, & Rapid Shutdown When: September 15t...

COMPANY BLOGS

Don't Fear The C-Suite

A lot of people are uncomfortable selling to the C-Suite (Chief Financia...

Solar Power Helps Detroit Community Light Streets

Residents of Highland Park, a city almost surrounded by Detroit, receive...

How to Survive the Solar ITC’s Expiration

The Solar ITC is set to expire at midnight on December 31, 2016. That se...

NEWSLETTERS

Renewable Energy: Subscribe Now

Solar Energy: Subscribe Now

Wind Energy: Subscribe Now

Geothermal Energy: Subscribe Now

Bioenergy: Subscribe Now  

 

FEATURED PARTNERS