Solar Junction Does it Again, Sets New CPV Efficiency Record

Vince Font, Contributing Editor
October 18, 2012 | 40 Comments

World records are broken every day, some to more fanfare than others. While earlier this week the eyes of the world were watching daredevil Felix Baumgartner's 24-mile skydive from the edge of space, a San Jose-based solar energy company called Solar Junction was busy breaking another kind of record.

As a company that specializes in the development of high efficiency multi-junction solar energy cells for the CPV (concentrated photovoltaic) market, Solar Junction is no stranger to breaking through previously established barriers and setting new records. Especially when those records are their own. In April of 2011, the company set a new standard for the energy efficiency of commercial-ready production solar cells, reaching 43.5 percent efficiency at 418 suns. Their new world record, announced on October 15 and verified by the National Renewable Energy Laboratory (NREL), brings that new standard up a significant notch, establishing 44 percent efficiency at 947 suns.

Solar Junction’s multi-junction cells are used in CPV solar panels, which focus concentrated sunlight onto the cells through the use of special optics. “CPV is different from standard flat-plate solar,” says Jeff Allen, VP of Business Development at Solar Junction. “Think of a magnifying glass. Basically, you have a very high performance solar cell that sits at the focal point of these focusing optics. The solar cell converts the photon flux into electrons, and power.”

The company’s trend of record breaking is welcome news in an industry that has lately hit a plateau in improvement, according to Allen. “Up until about five years ago, multi-junctions were running at about a one percent clip in terms of annual efficiency improvements,” Allen says. “Because the maturation of the three-junction technology was occurring, and because there was a lack of clarity about how to get to higher efficiency, that one percent per year diminished drastically over the last three to five years from the current technology providers.”

Allen says Solar Junction’s latest accomplishment, fueled by its proprietary Adjustable Spectrum Lattice Matched materials, is a sign that the sky’s the limit with respect to the capacity of CPV technology and the multi-junction cells that are integral to its efficient operation. “Flat-plate silicon type solar cells have largely met their physics limits in terms of increasing efficiency,” Allen says, “whereas multi-junction solar cells have not. You can actually add additional junctions to increase the efficiency over the coming years.”

2012 has been a period of exciting growth for Solar Junction, which has seen the formation of several key partnerships and the receipt of an esteemed government grant. Earlier in the year, Solar Junction announced separate partnerships with semiconductor company IQE, which has a facility in Bethlehem, Pennsylvania, and solar module manufacturer Semprius, which recently opened its first solar module production facility in Henderson, North Carolina. In addition, Solar Junction was named one of three recipients of the highly sought after SUNPATH grant from the Department of Energy, which has resulted in the company commissioning a 6” production fabrication facility in Sunnyvale, California. Allen predicts between 30 and 50 new jobs will be created at the company’s forthcoming Sunnyvale location.

“The nice thing is,” Allen says, “is that as capacity expands for us, that drives employment in North Carolina, it drives employment in Pennsylvania, and in California.”

Lead image: Red arrow via Shutterstock

40 Comments

Gerry Wootton
October 22, 2012

The good news about this story is that people can get excited over good-old-fashioned incremental engineering. That's technology that is close to practical use. Even simple systems such as solar panels do not hinge on one element so incremental improvement is supported by a myriad of other established technologies. PV is still in the throes of incremental improvement. Efficiency tends to have the greatest cost-benefit since the cost of capacity ($/W) is inversely proportional to efficiency. As some point out, efficiency also buys down BOS costs so classic $/Wp price comparison is inexact - there is extra value in increased module efficiency. One example problem is module cover glass: one may use clearer glass with AR coat to improve efficiency; but, we had to wait years for high quality glass with durable ARC to be commercially available at a sufficiently low price. This was delayed by concurrent declines in module BOM cost. On the other hand, as optical gains multiply cell efficiency, increasing cell efficiency helped make 'better' glass 'affordable'. But there are more gains to be had from glazing and encapsulant - this story continues.
Note: materials cost is a function of supply and demand - new applications create low initial demand and must somehow build volume to drive a new material to the 'right' cost. This is a big problem for CPV as there is little standardization of anything among manufacturers (as we can see from the above discussion of optical systems): basically, CPV doesn't have economy of scale working for it. A breakpoint for solar glass occured when it went from special run to mainstream production.
A third point: existing production has sunk costs tied to a process and a cost model that may have not yet achieved ROI. Changes with cost impact may have to wait and then change disrupts continuous production (a cost in itself). Plan B, starting from scratch, is also costly (reflected in incumbent's sunk costs) and risky (recent history).