Tag Archives: efficiency

Dow Kills CIGS Solar Shingles

The mega-merger between Dow and DuPont has already shaken out an under-performing product line:  Powerhouse(TM) solar singles. As reported at PVTech, over 100 jobs in Milpitas, California and in Midland, Michigan will be lost along with the production line that assembles the copper-indium-gallium-sulfide (CIGS) cells into thin-film Building-Integrated PhotoVoltaic (BIPV) rooftop shingles. BIPV markets are very slow to grow due to inherent risk-aversion in considering new building materials, and it has been difficult to cobble together sufficient consumer demand for upgrades to existing roofs to support a profitable business. Dow had offered a 20-year product warranty and optional financing to try to move the market.

(Source: Dow)

(Source: Dow)

“We’re looking at this one product that could generate $5 billion in revenue by 2015 and $10 billion by 2020,” Jane Palmieri, managing director of Dow Solar Solutions, told Reuters in a 2009 interview. Dow had used CIGS cells from Global Solar for a first-generation of the product line, and then acquired NuvoSun in 2013 to own it’s own thin-film CIGS manufacturing technology in anticipation of booming demand for large solar shingles with integrated internal electronics and easy rooftop installation.

When comparing the benefits of different PV product offerings, one factor dominates the decision:  all PV installations are area-constrained, and rooftops are extreme examples. The cost of the panel hardware is typically only ~25% of the complete installed system, with Balance Of System (BOS) costs for electronics and installation and financing and permits and non-recurring engineering (NRE). CIGS BIPV may cost less than silicon BIPV, but reduced conversion efficiency means less power can be produced from the roof and when you “do the math” it is always more profitable to use the most efficient PV possible.

Eric Wesoff at GreenTechMedia reported on the status of the thin-film CIGS PV segment of the industry last August when TSMC finally decided to cut losses and shutdown it’s CIGS pilot line. Wesoff reports that over US$2B in Venture Capital investments in CIGS companies has been written-off in the last decade, and that Solar Frontier is the only company selling market competitive CIGS panels with profit.

It is worth noting that the market for solar shingles had been poisoned by pathetic products from UniSolar leaving a severely negative impression on consumers. UniSolar was part of the Energy Conversion Devices portfolio of shell-companies that went bankrupt in 2012, and the UniSolar solar shingles had 6-8% cell efficiency using amorphous-silicon (a-Si) and no integration with electronics such that a hole had to be drilled through the roof for each shingle to connect to a micro-inverter (leading to extreme installation costs and an inherently leaky roof). So unfortunately, Dow faced a severe up-hill-battle in the roofing market to fight against a negative impression of all solar shingles.


Nakamura on blue light history and future

Nobel Laureate Shuji Nakamura provided the keynote address to the attendees at the 57th annual Electronic Materials Conference held this week in Columbus, Ohio. His talk on “The History and Developments of InGaN-based LEDs and Laser Diodes” informed and entertained the audience of materials researchers, particularly since he followed first-principles of materials science and his natural inspiration to create the world’s first commercially viable blue LEDs over 20 years ago.
Nakamura-sensei is now legendary for showing excellent GaN-based blue LED functionality in an era when ZnSe was the main material explored by almost all scientists in the world due to six orders of magnitude superior defectivity level for the latter material (due to near zero lattice mismatch between ZnSe and GaAs, instead of the extreme mismatch between GaN and sapphire). In the 57th EMC keynote, he confessed that the only reason he began work on GaN was that almost everyone else was ignoring it so he could easily get papers published on the way to earning a Ph.D., and he initially had no plans to try to create a blue LED with the material.
However, when he bought a new MOCVD reactor to grow GaN on sapphire substrates he found the capabilities of the tool to be lacking so he began daily hardware modifications and test runs, and after some months began to get surprisingly strong data. Soon his group at Nichia was reporting world record GaN optoelectronic properties, and had developed both n- and p-type GaN. However, from first principles it was known that a double-heterojunction (DH) structure would allow for band-gap and hence wavelength tuning, so he then developed the world’s first useful InGaN MOCVD process and by 1993 was able to issue a press release claiming 1000 mcd LED output. “Indium gallium nitride is the most important material, but the Nobel committee didn’t say anything about Indium gallium nitride,” reminded Nakamura.
Most of the rest of the story is well known by now, including his precedent-setting lawsuit with Nichia, move to UCSB, and founding of Soraa.
Nakamura’s vision for the the future of blue (and through integration with phosphors “white”) light can be summed up as LEDs are good but lasers are better. Relatively speaking, with lasers the current density can by many times higher, and BMW and Audi have prototype laser headlamps that can reach 2-3x farther down the road compared to the best lamps today. The challenges today are to improve efficiency and cost. Efficiency for blue LEDs are now 50-60% while lasers are only ~30%. Also, blue laser production cost is now ~10x higher than that for blue LEDs.