There are a number of fascinating new developments in the world of solar photovoltaic cells, which represent major shifts from the usual crystalline silicon cell based on semiconductor technology, which supplies as much as 80% of the market today (referring to wafers sliced from large single crystal or polycrystalline ingots). Here is a quick overview. Much more information exists on most of these topics.
Evergreen has one of most mature of the new approaches, and is now a growing public company (symbol ESLR), ramping up production of its unique string ribbon Silicon cell. The Evergreen cell is fully equivalent on a functional basis, but is considerably than the ingot slice method. Evergreen anticipates sales of $6-9 million in 2003. The website does a good job explaining the whole story. http://www.evergreensolar.com/
Solar Grade Silicon
In March, Solar Grade Silicon LLC announced full production of polycrystalline silicon at its new plant in Washington, the first ever plant dedicated wholly to producing feedstock for the solar industry. They supply the purified silicon that is then melted and made into single crystals, i.e. in large ingots, or Evergreen’s ribbon. In the past, solar cell makers relied on scraps from the semiconductor industry, which won’t be sufficient to handle the growth in the PV industry.
Spheral (ATS Automation)
In one of the stranger sagas of solar, you may recall that in 1995, Texas Instruments finally gave up on a major development program to develop “Spheral” solar cells, an effort they’d devoted many years and many dollars to (with considerable support from DOE). Spheral technology comprises thousands of tiny silicon spheres, bonded between thin flexible aluminum foil substrates to form solar cells, which are then assembled into lightweight flexible modules. TI’s goal was to develop a manufacturing process that would drive PV costs to $2/watt. Ontario Hydro Technologies acquired the technology, set up manufacturing in Toronto, and sold some systems, but in 1997, reorganizations and a return to basics led them to sell it off. Apparently dormant since then, in July 2002 ATS Automation announced it had acquired the technology, set up a subsidiary, and was scaling up production with plans to be in commercial production this year. The Canadian government put in nearly $30 Million. The jury is out on this one. For the story, go to: http://www.spheralsolar.com/
Commercially produced thin film PV falls into 3 general categories, Cadium Telluride, Amorphous Silicon, and CIGS (Cu(In,Ga)Se2). The first two technologies are struggling, with BP’s notable exit last November from both. CIGS is having instances of some apparent success and continuing development efforts, and enjoys strong support at NREL, a true believer. There are production facilities doing CIGS as well as innumerable development efforts around the world to make it cheaper and more efficient. CIGS has the unique feature of becoming more efficient as it ages.
Global, partly owned Unisource, the parent of Tucson Electric, is selling thin film CIGS modules to the military, commercial and recreational markets. One product is a blanket a soldier can unfold on the ground. Current production capacity is 2.3 MW per year, and they’re fundraising to expand to 7.5 MW. http://www.globalsolar.com
Among the new entrants, Raycom is a startup in Silicon Valley, led by veterans of thin film coating for disk drives and optical filters. They believe their experience (and existing equipment) will enable them to avoid the long and painful development cycles that have traditionally characterized the solar PV industry, and be in production in less than 2 years. Their secret is “dual-rotary magnetron sputtering” a patented process that has already proven effective in high volume manufacturing. Cost targets are under $1 per watt. They also have brought a fresh eye to the formulation of CIGS, and see ways to make it without cadmium, which is highly toxic. Raycom produced their first working cells in a matter of months. They are in the midst of fundraising. One might observe that this is a rare instance where someone comes to PV from manufacturing instead of science. Normally, people develop PV technology in the lab and then endeavor to become manufacturers. This time it’s the other way around. [To see the magetron sputtering technology, go to:
Contact David Pearce 408-456-5706, email@example.com
Konarka has attracted a great deal of attention and sizable VC participation (funding round Oct 02) with promises of a way to commercialize the “Gratzel” cell, which Dr. Michael Grätzel developed and subsequently patented in the 1990’s. The core of the technology consists of nanometer-scale crystals of TiO2 semiconductor coated with light-absorbing dye and embedded in an electrolyte between the front and back electrical contacts. Photons are absorbed by the dye, liberating an electron which escapes via the TiO2 to the external circuit. The electron returns on the other side of the cell, and is restores another dye molecule. The jury is out on this one, whether it’ll happen quickly as the company and its investors hope, or will there be a long road ahead. One of the biggest issues since this idea was first tried has been the stability of the organic dyes. http://www.konarkatech.com/
For a good discussion of dye-sensitized cells, see this pdf:
This Palo Alto based company has a long list of goals for its nanotechnology, ranging from chemical/biological sensors, to electronics and photovoltaics, based on formulations of nanowires, nanotubes, and nanoparticles. Their idea for PV is reportedly to embed nanorods of photosensitive material in a polymer electrolyte, on a principle not unlike Konarka’s. On April 24, they announced an amazing $30 Million VC funding. You have to wonder about this one, i.e. if the nano-hype has taken over, and how successful they’ll be about solar as compared with the other areas.
The technology was originally developed at Lawrence Berkeley Lab:
Also Palo Alto based, this one is in stealth mode. The basic idea is similar to Nanosys, but they are focused only on solar. They also incorporate technology licensed from Sandia for nano-self-assembly to align the nanorods perpendicular to the surface, which is supposed to make a big difference in the efficiency. (Nanosys’s nanorods are said to be randomly oriented in clumps.) NanoSolar has some very famous investors, who are maintaining an extremely low profile.
Solaicx is a new spinout from SRI International, and has a way to make polycrystalline silicon cell material in a continuous process atmospheric-pressure furnace. Their presentations and materials tell very little about what they have, making it pretty hard to judge.
This is a very unusual concentrator story involving the use of variable “graded” index glass optics. The work started in the mid 80’s. Solaria Corporation was formed in 1998 by the founders and former management from LightPath Technologies, Inc., Albuquerque, New Mexico. Solaria holds the exclusive license from LightPath to use its proprietary GRADIUM® optics in the field of solar energy. http://www.solaria.com/
** These companies presented at the Cleantech Venture Forum in San Francisco, April 30.