Using copper instead of silver to create the electrical contact lines on solar panels is one of the in-vogue technologies these days, judging by a panel that devoted to commercializing this process at Intersolar in San Francisco this week.
The discussion focused on different approaches to lay down the copper grid, in particular those that deviate from the conventional screen printing method for creating the silver contact lines.
Why copper? The material is cheaper and more readily available compared to silver, which has been the industry choice for creating the grid that ferries electrons produced by the cells. Solar panel makers are understandably ultra sensitive to production costs nowadays, given the crazy drop of solar panel prices thanks to a glut of them over the past two and a half years.
Silver costs about 560 euros per kilogram, while copper can be had for 7 euros per kilogram, said Martijn Zwegers, solar product manager at the Netherlands-based Meco Equipment Engineers and a panel member.
Manufacturing costs for major Chinese companies plummeted by about 55 percent from the fourth quarter of 2010 to the same quarter in 2012, according to GTM Research.
If you think the copper idea isn't new, you are right. It's been bandied about for at least four decades, said Tom Surek, the panel moderator who started his own solar consulting service after retiring from his post as the PV program manager at the National Renewable Energy Laboratory. I wrote about Suntech Power's plan to use copper back in 2009 when the company was working on commercializing its Pluto technology.
Aside from Meco, the Intersolar panel featured equipment makers such as Meyer Burger (Roth & Rau) from Switzerland and First Solar. First Solar's recent acquisition of TetraSun surprised those who thought the Arizona thin film maker would invest in silicon-based technology.
TetraSun claims to have figured out how to make monocrystalline silicon cells at the cost of multicrystalline silicon cells. Though Adrian Turner, TetraSun's co-founder and now First Solar's director of silicon research and development, talked about the company's use of copper at the panel, Turner said TetraSun's core intellectual property in fact focuses more on techniques such as the use of cell surface passivation, which aims to protect the cells from environmental elements that could damage them.
Screen printing has been the conventional method of creating the electrical contact lines. With copper, factory tool makers have rolled out plating equipment, which can create thinner lines faster and at lower temperatures (750-800° Celsius v. 350-400° Celsius), Zwegers said. Meyer Burger, meanwhile, has developed what it branded SmartWire technology for creating the copper grid and launched the equipment for that earlier this year.
Both tool makers engineered their equipment for making bifacial cells, which enable electricity production on both sides of the cells. Sanyo, now part of Panasonic, is known for its bifacial cells that make use of crystalline silicon and amorphous silicon. TetraSun also has been developing bifacial cells. First Solar plans to start commercial shipment of silicon panels with TetraSun's technology next year and is currently working on building a 100-MW factory, which could be in the United States or Asia, Turner said.