When solar industry start-up Energy Innovations Inc. built its first products in China a few years ago, the company ran into a snag. Energy Innovations’ Sunflower concentrating photovoltaic system relies on proprietary fresnel lenses to focus sunlight onto small, triple-junction, silicon solar cells to efficiently produce electricity. Precise alignment between the lenses and the photovoltaic cells is key.“For production, we were relying on manual alignment techniques, and the yield was not very good,” says Bud Sherman, vice president of operations at the Pasadena, Calif.-based firm. “We could build product,” Sherman relates, “but you wouldn’t call it commercially successful.”The basic building blocks of the utility-grade Sunflower system are modules about three-feet square, each incorporating 30 solar cells that are about one foot away from the concentrating lenses. “The precisions with which you have to put the systems together are really, really tight,” Sherman observes.
Tight alignment
As Energy Innovations managers looked into the yield problem, they began to realize that the alignment task—with tolerances in the neighborhood of 0.005-0.01 inch—was not something that could be done with sufficient consistency by human operators. Research by the firm on manufacturing methods used for other precision optical products, such as cameras and projection TVs, suggested the use of robots instead. So Energy Innovations set out to automate the Sunflower production process.The company purchased a robot from its local Fanuc Robotics office, and found the Fanuc representative to be very helpful, says Sherman. “Between him and a few other people and our manufacturing engineer, we were able to get some of these very precise process steps working, using this one robot.” Then, late last year, the company engaged the robot vendor’s integration service—Fanuc Robotics Automation Systems Group, Rochester Hills, Mich.—for a design for manufacturability (DFM) study, and redesigned the Sunflower product for better manufacturability, while also designing the fully automated process by which it will be made. “So far, it’s been a very successful relationship with the integrator. They’ve given us a lot of suggestions that have improved the manufacturability of the product,” Sherman observes.The effort will culminate within the next few weeks when Energy Innovations begins constructing a new manufacturing line to build the redesigned Sunflower 3.0 product. The initial line will go in at a partner contract manufacturing site in California, with volume production to start “probably in the fourth quarter,” says Sherman. “This manufacturing line is conceived to be a manufacturing cell, with a capacity of 10 megawatts (MW) per year. As demand shows up in different parts of the world, we’ll put in as many manufacturing cells as we need to satisfy that demand.”
Robot tasks
Each 10 MW-capacity cell will occupy around 7,000 square feet of floor space and deploy about a dozen six-axis Fanuc robots. The robots will handle applications including precise placement of small parts and large structures, ultrasonic welding, sealant and adhesive dispensing, and automated screwdriving, along with loading and unloading tasks.By fully automating the manufacturing process, Energy Innovations expects to overcome the manual precision alignment problems encountered in its earlier production line. In the new manufacturing cell, “we’ll use the robots to move things into place and get the rough alignment to within maybe 0.015 inch, and then we have some final tooling that dials it in the rest of the way,” Sherman explains.For Energy Innovations, the robotic automation technology could prove to be a lifesaver. “I’ve been in manufacturing for a while, and I don’t believe that we could assemble this thing using operators and fixtures, the way that people normally do things,” Sherman says. “This thing has got to be put together with machines. The repeatability and accuracy are very important,” he adds, “and you’re just not going to get that with manual operators.”
Feature Article - Solar Manufacturing: A Sunny Forecast for RoboticsTo read the feature article relating to this story, go towww.automationworld.com/feature-5147
