Efficiency—the rate that solar cells or modules convert sunlight into electricity—has always been an important metric for manufacturers. But improving it has become a greater emphasis these days, and factory equipment manufacturers have responded with R&D efforts to deliver better tools. Applied Materials on Wednesday unveiled a new set of equipment under its Baccini brand that it said will enable customers to lower production costs and use advanced technologies to boost cell efficiencies.
The new line is called Baccini Pegaso, and it covers equipment for screen printing metal lines (commonly silver), a dryer, defect inspection, and testing and sorting silicon solar cells. The metal lines serve as the highways that conduct and transport the electrons out of the cells. Printing them with precision is important to makes sure they don’t cover up the cell surface that should be exposed to the sun to generate electricity.
The Santa Clara, Calif., company already sells Baccini-branded tools for these steps. In fact, Applied claims to be the top supplier of screen printing systems and says about 75 percent of the silicon solar cells made today come from its Baccini equipment. But Pegaso is the next-generation system which, unlike other Baccini lines, comes with dual lanes – instead of a single track – for screen-printing silicon wafers. Two lines of wafers can move through the printing process at the same time, a design that aims to reduce the downtime when equipment has to remain idle for maintenance. The equipment also comes with inspection equipment that can look for defects and make adjustments quickly to correct any mistakes.
The results are varying degrees of improvement from other Baccini lines and from competitors’ offerings, Applied executives said. Pegaso, for example, can reduce wafer breakage rate to 0.15 percent, which exceeds the 0.2 percent from the Baccini Soft Line. Pegaso’s breakage rate is two times better than competitors’ tools, said Jim Cushing, senior director of global product marketing for Applied’s solar business. The same advantage for the accuracy of aligning the metal lines on the silicon wafers, he added. Pegaso achieves an alignment accuracy of 8 microns.
The printing precision and alignment rates are important for manufacturers who are working on new screen-printing processes that require printing more than one layer of materials to improve the efficiency of the metal grid to move the electrons around. Most of the solar cells made today still rely on the conventional process of printing the silver lines once, Cushing said.
But the industry may move away from that if manufacturers are able to use more novel approaches, such as selective emitters, in large-volume production. If screen-printing involves depositing materials multiple times, then the production line will need multiple printers. Applied designed Pegaso to make it easier for manufactures to add and configure their equipment. This flexibility isn’t as easily achieved with previous Baccini lines. One challenge involves integrating new software with older software when adding a new piece of equipment, Cushing said.
Enabling solar cell manufactures to use newer processes means improving the efficiency of the cells, Cushing said. Pegaso itself can reduce production costs by increasing the production rate (with its dual-track design) while minimizing printing defects and the amount of idling time for repairs and maintenance.
Using Pegaso can cut screen-printing costs by 5 percent, Cushing said. Screen-printing accounts for 10-14 percent of the cell manufacturing process, including the cost of wafers, Cushing added. Three customers have been using Pegaso, including Gintech Energy in Taiwan.
Pressure to cut manufacturing costs and improve efficiencies is greater than ever before. Whereas in the past, manufactures tended to focus more on building factories and finding ways to boost the production rates, they now put more emphasis on research-and-development work to bump up efficiencies. Doing so not only cuts manufacturing costs for solar cells and therefore the panels as well, but also cuts installation costs.
A solar panel’s efficiency is correlated with its dimensions and the amount of power it can generate. Manufacturers measure their production costs in terms of cost per watt. So if they can produce more efficient panels without incurring too much additional costs, then they can lower the cost per watt.
More efficient panels also helps to reduce installation costs because installers don’t need to use as many solar panels to build a solar electric array to meet whatever solar electricity production capacity they are striving for. Cushing noted that Europe, the largest solar energy market, has recently tweaked its incentives to favor smaller, rooftop solar systems. That change has increased demand for more efficient solar panels.
"We need to continue with scaling and cost reduction, but we have to couple efficiency with that," Cushing said.
Despite reports about solar manufacturers producing more panels than the market can handle over the past year, cells with higher efficiencies remain a hot commodity, Cushing said. “Our customers can’t sell the higher efficient cells fast enough,” he said. Higher efficient cells are those that can convert more than 17.5 percent of the sunlight that hits them into electricity, he added.
Other solar factory equipment makers also are investing in new technologies to help customers improve cell efficiencies. New Hampshire-based GT Advanced Technologies last week announced a $60 million purchase of Confluence Solar in order to offer machines that can produce silicon ingots that promise to deliver more efficient cells at lower costs. GT's CEO, Tom Guitterez, also pointed out that manufacturers are paying more atttention to sunlight-to-electricity efficienicies these days.
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