Thursday, February 16, 2006

On the Delay / Cash Needs of Solar Cell Startups Miasole and Others

re SiliconBeat's 2/15 post on Solar Power Startups Taking More Cash & Time

hmm... well this gets interesting. Most anything BUT silicon for solar cells comes with all kinds of baggage - higher costs, more complex (and even speculative) chemistry, real risks in RESEARCH that properly are not typical of a good startup's product focused mission.

I think a few famous VCs have voiced that startups are best not R&D outfits, but really lets leave it at startups not properly being speculative materials research outfits. Basic novel materials development, due to its typical long gestation cycle, is best an Academic R&D endeavor funded by the government.

For all the disparaging of silicon, like in any process endeavor, Silicon photovoltaics are easiest to develop incrementally at lower risk due to well known materials properties and modest processing costs. Excessive risks of alternative PV materials are to be viewed warily or at least skeptically, as the costs of startup failure are substantive, unless you have the golden parachute.

I am not proposing here that garden variety silicon wafer cells are worth the time of day to start a firm, but I am firm a believer in the probability that a silicon material based PV startup will have a better chance of "Crossing the Chasm" and surviving.

CONT'D - click READ MORE.... for the full scoop.

CIGS cells which are made quite successfully in the lab are mostly still too expensive to fabricate at competitive costs unless you have the skills from the ETH Zurich labs where they have figured out how to get CIGS on polymer film substrates at efficiency of around 13%, which is pretty darn good. Hard panel processing of CIGS - whether on rigid boards or flex steel, is not a value proposition, nor compelling market entre longer term.

And specifically Miasole's CIGS (Copper Indium Gallium Selenide) (originally) using a stainless web, roll to roll processed substrate, is fraught with materials and processing challenges. They sputter the multiple CIGS layers and likely heat, as all have to do for optimal CIGS activation - and in a large stainless flex substrate, there are both thermal non-uniformities and probable high TCE thermal expansion mismatch - creating challenges for adhesion of the sputtered film and potential for cracking. Not to mention that the web feed for roll to roll has to be optimally designed for both web transport and avoiding cracking of the sputter deposited CIGS.

Now there are a few more subtleties involved - Miasole's earlier long gone web site showed both a novel in house designed rotating tubular sputter cathode (for optimal materials utilization in sputtering) and the need to do laser scribing and pneumatic shear cutting of the web to make tiles for voltage cascading. Quite novel, but each has its own artifacts to take due care with. I think their patents also describe some of this...

Typical industrial laser scribing is done with YAG ~1um wavelength Q-switched lasers to ablate or cut a thin film. The thermally conducting steel is going to heat sink the YAG power and not help with clean layer ablating, desireable for good electrical isolation after laser cutting, at least with a YAG. You can use an "athermal" Excimer laser ( shorter wavelength and much faster pulses ) but at much greater capital expense and slower throughput.

Shear cutting the sputter CIGS on flex stainless steel is possibly going to induce edge damage to the CIGS layers - either CIGS cracking in vicinity of the shear cut of the metal, or possibly shorting the CIGS layer at the point of shear ( as they showed it in their older web site, but did not describe the technical issues to implementation) . Moreover if one wanted to clear the CIGS layer away from the point of metal cut / shear to before the shear cut, to minimize these effects of damage to the CIGS, it will be more costly laser processing, with the same issue of the laser cell shaping they claim they use.

Now another comment re Miasole, the custom novel sputter cathode design they said would reduce costs, is a fairly complex cathode, and not available off the shelf from a vendor. Designing your own novel sputter cathode is not what you want to spend any time on initially, until the rest of the process works to produce a reliable manufacturing process. Any diversion of any effort away from fast prove in of a new cigs / substrate / manufacturing flow, to acheive needed relaibility, yield and stable device characteristics, is a distraction in the realm or priorities for a solar cell startup in development. I suspect this was underestimated, and while the cathode technology is cool, it is not critical path for shipping a product. FOCUS FOCUS FOCUS...( ie keep your horse blinders on the main goal, to not stray from the path well travelled)

The recent Iowa Thin Film Technology - an excellent a-Si on wide web polyimide film, is partly derived from prior a-Si R&D work, and seems to have perfected production scale a-Si on roll to roll, in larger capacity than ever seen before. Marvelous practical advance done on production scale web processing, end to end roll to roll apparently, which is the real challenge for cost reduction. And shipping in volume - you guessed it - using silicon materials.

I'd also point out that SunPower has perfected the astounding art of cost effective high efficiency (20%) single crystal cells and done so with exquisite engineering over many many years of expert work of Dr. Swanson.

Another innovation success in silicon is Evergreen Technology, whose core manufacturing technology - Edge Fed String Growth ( of poly xtal silicon ) is a very decent advance in low cost silicon, that is partially derived from a comparable but less efficient process out of Schott Solar, modified by Prof. Sachs of MIT to be more efficient in poly use and require simpler strip cutting rather than complex cutting of the hollow Hex drawn shape from Schott. Evergreen is ramping thin silicon cells now in a new $30m 2nd production plant, and still improving their machine technology.

I am not disparaging the efforts of Konarka, but I will definitely say that despite the obviously stellar scientific and management team, it is unclear if they are really advancing both cell efficiency and product lifetimes to commercially viable levels in the novel polymer technology (with Evident's R&D phase wavelength convertors).

Same can be said with Nanosys's CdSe branched tetrapod nanocrystal based cells. Will these ever get enough efficiency to warrant the effort and speculative capital being put into the Solar PV effort at Nanosys (in a reasonable amount of time)?

( 7pm Friday feb 17th ....entry for Nanosolar is previously incorrect re polymer web - and they are using "relatively conventional" CIGS materials but in a rather novel ink dispense on roll to roll .... more to follow later this weekend - pointed out by Jeff Kaplan) ......
And yet another novel materials foray is by NanoSolar with their ink based CIGS photovoltaics on roll to roll inexpensive unnamed ?metal web ( not stainless which is the typical CIGS substrate ). Has Nanosolar attained the needed reliability and conversion efficency? Apparently the case. Their process is a novel ink dispersion of CIGS, which is more conventionally sputtered, but this at least starts with decently understood PV conversion metallurgy..and their likely metallic web material is apparently considerably elss expensive than stainless ( per their released info )- so they both eliminate costly sputtering and are using a much cheaper substrate than the conventional stainless used most typically with CIGS cells. A curiously innovative and seemingly good effort. [ ANOTHER NOTABLE point is that Nanosolar states on their web site > that they are not presently accepting new capital ! This is a hopeful indication that they have likely made excellent progress !! ]

The jaded fellow I am, from 22yrs of real process engineering (not merely some fancy academic lab) says that basic science breakthroughs are not properly the domain of startups unless you have an unusual balance of team science, production process expertise ( not turn the crank mfg) and extremely rare fluid team problem solving that occurs faster than can be managed "conventionally" or predictably.. One has to be very fleet on one's ( team's) feet intellectually, to make rapid breakthroughs in the context of cost effective manufacturing with new unproven materials.

Had either Konarka's or Nanosys' PV efforts had benchmarked at reasonable 10+% conversion efficiency, - all for product worthy lifetime, reliability and yield, previously in the academic setting where originally persued, then it would be acceptable risk for a startup to launch production and then push beyond 10% efficiency threshold at Konarka and Nanosys concurrent with manufacturing. Miasole's challenges lay only in the yield and reliability I would gather and not likely in cell efficiency.

There are exceptions to this skeptical realism, but examples of basic research success in materials, in a time and cash flow critical startup environment are rare, mostly because management of breakthroughs in basic technology is a fine and rare art, and even rarer at startups, and even rarer in basic materials innovations.
( See Gargini's wise words for R&D )

enough said.


Anonymous Matt Marshall said...

Thanks for the informative overview, Mark. Look forward to reading more of your blog!

10:59 AM  
Blogger Jeff Worth said...

Very interesting blog Mark. Do you do consulting work or would you perhaps consider permanent employment?

8:18 AM  

Post a Comment

Links to this post:

Create a Link

<< Home

Enter your email address:

Delivered by FeedBurner

Subscribe to Wendmans Views on Nanotech by Email