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Credit: Kevin Bullis and Technology Review

Last August I wrote about the typical 50% waste created when wire saws are used to slice silicon ingots into PV-suitable wafers, and research being conducted in Germany to lower that waste.

Now 1366 Technologies, according to a story and video by Technology Review’s Kevin Bullis, is saying it might be able eliminate all saw waste, apparently by directly manufacturing each wafer from molten silicon. 1366 showed off their technology at the recent pre-ARPA-E Summit Innovation Showcase.

Although always happy to see basic PV science breakthroughs, 1366 has always proclaimed that its route to success in the industry is through process and manufacturing innovation. To put a finer point on this, 1366 says the cost of its PV units will reach parity with coal power in a decade.

According to Bullis, credit for the direct-wafer process invention goes to Emanuel Sachs, a professor at MIT who co-founded the company and is behind of portfolio of PV innovations. The company likens the potential for this new innovation to the shift from handcrafting glass windows to use of float-glass manufacturing.

While only small low-efficiency demonstrator wafers have been created so far, ARPA-E apparently likes what it sees and has given the company $4 million to continue this work. Read the whole article and watch the video (an interview with CEO and 1366 co-founder Frank van Mierlo at the showcase).

For more information on 1366 Technologies, see:

Cutting PV costs, Part 1: New busbars, ‘fingers’ to cut costs by 20%?

Cutting PV costs, Part 2: Process improvements versus science breakthroughs

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Credit: 1366 Technologies

Yesterday we posted a Technology Review video interview with Emanuel Sachs (1366 Technologies’ chief technology officer and professor of mechanical engineering at MIT) in which he and Craig Lund (1366’s director of business development) discuss some of the new technologies the company is incorporating into PV panels.

Sachs did what I think is a very important and (shorter) follow-up video in which he argues that 1) creating efficiencies on the materials processing and manufacturing side of photovoltaics is currently playing a bigger role than scientific discoveries in getting solar power to the point where it is competitive with traditional energy sources, and 2) at the point of parity, battery/energy storage technology becomes the dominant concern.

Sachs says, basically, that at any given point, when a PV panel is manufactured it is an amalgam of several recent processing advances, and the current development of photovoltaics is akin to the stages that occurred with microelectronics.

“Today’s silicon device uses lots of lots of different innovations that have taken place. A company doesn’t need to invent the entire process sequence. They can grab what it needs and then, maybe, add something special that will distinguish them in the process space. . . This is a breakthrough in scale of production. That’s what PV is about because you have to cover huge portions of the earth’s surface . . . These are breakthroughs, too. These are breakthroughs in manufacturing and production. People in this country are not accustomed to thinking of these as breakthroughs. Other parts of the world have a very different view because they understand where the money is made . . . It’s fine to pursue [science breakthroughs] but don’t misunderstand what we already have.” [emphasis added]

That’s a pretty profound argument that really challenges those of us who tend to be obsessive about the science innovations versus improving the details related to how the feedstock is prepared and the then brought together as a panel.

I thought the chart in the video would be useful to look at, and Craig Lund kindly provided the version that appears above. Click on the image to enlarge it.

ADDING: I later checked with Lund regarding Sachs’ view about where the trend indicated in the chart was heading. He informed me that Sachs believes the accumulation of manufacturing innovations will continue to drive down the cost of crystalline silicon PV until 2025 when the cost of solar generated electricity will be significantly cheaper than coal.

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Technology Review has a video (24 min.) of a recent interview with Emanuel Sachs, 1366 Technologies’ chief technology officer and professor of mechanical engineering at MIT. He explains the physics of solar cells and how 1366 is using the techniques described below to try to make them more efficient. (Note, there is a brief sponsor video that runs first.)

This Lexington, Mass., solar startup claims to have developed three processes that can be incorporated into existing solar cell manufacturing lines to improve cell efficiency. According to the company, these technologies can be used to produce multicrystalline solar cells that are 18 percent more efficient at converting sunlight into electricity, and about 20 percent cheaper.

The current industry standard for such solar cells is 15 percent to 16 percent, according to Joonki Song, a partner with Photon Consulting, based in Boston

An accompanying Technology Review article describes the new technologies:

In a normal silicon solar cell, electrons generated in the silicon must make their way out of the material to produce an electrical current, traveling first to the top layer of the silicon and then along this layer to narrow silver lines called “fingers.” The fingers then conduct the electrons to the busbars, two or three prominent silver bands seen on the surface of most silicon solar cells. These bands shade the silicon under them, reducing the amount of light the cells can absorb.

The first new process developed by 1366 Technologies produces grooved busbars that prevent light from being reflected out of a solar panel. Instead, the grooves cause light to be redirected along the glass on top of solar panels. That light can then be absorbed by unshaded areas of the solar cell.

The second process improves the cell’s electron-conducting fingers. Although these silver lines are much narrower than the busbars, there are many more of them on a solar cell, and together they shade a significant portion of the silicon. Sachs developed a process for making much narrower lines without sacrificing their conductivity. Instead of using conventional screen-printing technology, his process involves etching troughs into the surface of the silicon and depositing silver particles into the troughs. Metal is then added to these particles via electroplating to build up the fingers. The trough keeps the lines narrow but allows the silver to be stacked relatively high, maintaining conductivity. Typically busbars and fingers shade 9 percent of a cell surface, 1366 Technologies says, but with the company’s new processes, this shading can be reduced to 2 percent. Others have developed techniques for reducing shading, but these have been expensive.

The third process decreases the amount of light reflected off the surface of the cell’s silicon by texturing its surface. This is an approach that’s been taken by others, but the texturing is done in a very regular pattern that creates less surface area than other approaches. Surface area is a problem in solar cells, because electrons are often trapped at the surface of materials, Sachs says.

1366's special grooved busbar ribbons can reflect light within a PV unit. Credit: 1366 Technologies.

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