The desire to find a less expensive way to generate electricity from the sun has spawned research into almost as many solar energy processes as there are ways to mispronounce "photovoltaics," the technology's proper name.
The familiar round, single-crystal silicon wafers will continue to dominate the market for many years, largely because of their "tremendous momentum" in the marketplace, according to Paul Maycock, former photovoltaics chief of the Department of Energy and now a private consultant in the field with his own company, Photovoltaic Energy Systems Inc., of Alexandria.
However, increasing attention is being drawn to a host of other basic materials, such as polycrystalline silicon, noncrystalline silicon, and various combinations of cadmium, sulfur, tellurium, gallium, arsenic, aluminum and other elements.
It is the companies dealing with these that are now grabbing most of the headlines, although certainly not all the sales. At the recent annual meeting of the American Solar Energy Society here, two American companies gave their competitors and the public the first look at commercial or near-commercial photovoltaic cells from these unconventional materials.
Chronar Corp. of Princeton, N.J., which pioneered the liquid crystal digital wristwatch, has become the first U.S. firm to accept orders for thin-film solar cells made of noncrystalline or amorphous silicon. Unlike the cells made by industry leaders such as Solarex Corp. of Rockville, and ARCO Solar Inc. of Chatsworth, Calif., Chronar's product uses a raw material that is far less expensive than ARCO's ultra-pure single-crystal silicon or Solarex's somewhat less-pure "poly."
Chronar is delving into a market that until recently had been left largely to Japanese firms such as Sanyo and Fuji, which are concentrating on such peripheral areas as solar-powered watches and calculators. However, the American firm says it is now ready to take orders for arrays of panels large enough to power an isolated appliance or run an entire home, or even generate electricity to feed into a utility grid. It also has reached a tentative agreement with investors in Morocco for such a deal.
The price of photovoltaic modules has plunged from $150 per peak watt in 1974 to $7-to-10 today. (A peak watt is the measurement of power produced by a solar cell aimed at the sun directly overhead on a cloudless day.)
Now, Chronar president Zoltan Kiss has been promoting his cells at prices 10 to 15 percent below those of his established competitors and as low as $3 per peak watt for single orders of millions of watts, with delivery in 1985 or 1986.
In general, costs will be brought down by increasing efficiencies of converting sunlight to electricity so fewer panels are needed for a given task, by finding cheaper raw materials, by moving from batch processing to continuous operation, and by automating as many steps as possible. Talking about the "big breakthrough" is highly misleading because progress comes only in tiny steps stretched out over years, or as Maycock puts it, through the "breakthrough of the month."
Another American firm, Energy Conversion Devices (ECD) of Troy, Mich., has been working with a different amorphous silicon process for several years and has announced a string of increasingly more impressive efficiency achievements, but only with chips of cells too small for marketing.
While its cells are probably more efficient than Chronar's (ECD won't say for sure), they are not up to the level of crystalline silicon models and ECD is still in the planning stages for commercial production. In recent weeks, company president Stanford Ovshinsky announced an agreement with Sharp Corp. of Japan to open a factory near Osaka to make the cells--at first for internal use, then for calculators and finally for power modules when production efficiencies reach 7 percent.
Other companies, such as Mobil-Tyco Solar Energy Corp., of Waltham, Mass., are also engaged in silicon work. But Mobil-Tyco has developed a way to produce so-called "thick-film" ribbons of polycrystalline silicon of 100 feet in length or more, rather than the one-at-a-time, even if automated, process of Solarex and ARCO Solar. (That individual cell production technique has not prevented ARCO Solar from beginning to assemble the world's first one-megawatt array, which it will own and operate in selling power to Southern California Edison Co.)
Meanwhile, some firms are by-passing silicon altogether. Also making a debut at the Houston exposition was Ametek Corp., of Paoli, Pa. Even though it makes the conventional single-crystal silicon wafers for other solar companies' cells, Ametek is most excited about its new cadmium-telluride cells, the first such material to emerge from the laboratory.
Ametek chose cadmium-telluride because it believes higher efficiencies are possible with the alloy. As early as a year ago, the company said modest production runs produced cells rated at 5 to 6 percent, while individual test cells were measured at 8 to 9 percent, and the company says it will eventually attain production runs at 18 percent.
These firms are only some of the ones that are in or nearing the market. Behind them come such industry giants as Texas Instruments (which is working under a $14 million DOE contract to develop a unique cell that employs photovoltaic beads the size of grains of sand) and Shell Oil, which is developing a cadmium-sulfide cell and is also working with ECD.
Lesser levels of activity have also been shown by General Electric, Westinghouse and Honeywell. And Thermocell Ltd., a new firm in Broomfield, Colo., is investigating the possibility of using thin-film work performed at DOE's Solar Energy Research Institute in Golden, Colo., by mounting cells on a collapsible window shade that would double as an insulating shutter.