After several decades of on-again, off-again growth spurts, solar energy is maturing in the United States. That’s good news for domestic manufacturers of photovoltaic (PV) cells and solar panels. In fact, during the past two years, at least a dozen companies have launched or announced new assembly plants in different parts of the country.
More solar capacity was added to the grid in 2019 than any other energy source. The United States now has more than 77 gigawatts of PV capacity installed, which is approximately 3 percent of all electricity generation. And, according to the Solar Energy Industries Association (SEIA), 40 percent of all new electric generating capacity additions in the U.S. are now sun powered.
Despite that recent growth, the solar energy industry endured a rough patch between 2012 and 2016. During that stretch, nearly 30 U.S. manufacturers were forced to shut their doors when intense competition from Asian firms flooded the market with low-cost products.
To address the issue, in early 2018, the Trump administration announced a 30 percent tariff on solar panels imported into the United States. That strategic move has prompted many firms to once-again assemble solar modules domestically.
“The solar industry is in a strong position to become the leading source of new energy generation this decade,” says Abigail Ross Hopper, president and CEO of SEIA. “Costs have fallen by 70 percent since 2010, making both rooftop and utility-scale solar generation competitive with other forms of electricity generation.”
That’s having a ripple effect on both residential and commercial solar panel demand. Earlier this year, California enacted a law that requires solar panels on all new homes built in the state. In addition, sustainable roofs are now required in other parts of the country, such as New York City.
Manufacturers across the country have also been attracted to the benefits of solar power. For example, General Motors recently announced that its 8-millionsquare- foot assembly plant in Spring Hill, TN, will be powered by 100 percent solar energy beginning in late 2022.
General Motors leads all U.S carmakers in solar panel deployment. The company has pledged to go 100 percent renewable by 2050, with solar and wind power sharing most of the load.
By 2030, all of GM’s U.S. factories will run on renewable energy. So far, GM has installed more than 11 megawatts worth of solar panels at more than a dozen domestic plants. That includes an 850-kilowatt system at its assembly plant in Bowling Green, KY.
Earlier this year, SEIA announced an aggressive goal that calls for solar power to reach 20 percent of all U.S. electricity generation by 2030. In fact, the organization dubbed the 2020s the Solar+ Decade.
“To get there, the industry will need to deploy nearly 400 gigawatts of solar in the next 10 years,” claims Hopper. “Installations at that scale will require an unprecedented amount of manufacturing, from cells and modules to racking and inverters.”
Made in the USA
The vast majority of solar modules are currently built in Asia, close to wafer, cell and glass supply chains. But, things are starting to change.
“We have crossed the threshold to where solar is now more efficient and cost-competitive than ever,” says Robert Margolis, senior energy analyst at the National Renewable Energy Laboratory. “Domestic production has increased significantly in the past two years. In particular, we have seen an increase in module assembly. There will continue to be a lot of growth in the industry, because most local manufacturing is still ramping up.”
While some assembly plants are located in sunny states, such as California and Georgia, they can also be found in northern Minnesota and northern Ohio. And, those operations vary from small to large facilities.
On one hand, there’s Solaria Corp. Although the Silicon Valley-based company operates high-volume assembly lines in South Korea, it maintains a modest facility in Fremont, CA. The 15,000-square-foot plant primarily focuses on new products and production processes.
That’s where engineers developed the Solaria PowerXT, one of the most advanced solar panels on the market today. A patented cell design, advanced panel architecture and innovative assembly techniques enable greater than 20 percent efficiency with no visible circuitry.
“Our product design and manufacturing process is unique,” says Suvi Sharma, director of Solaria. “The traditional way you make solar panels is to take square silicon solar cells that are strung together with soldered wires that result in a variety of unsightly silver lines.
“We do things differently by slicing solar cells into narrow strips before they’re inserted into modules,” explains Sharma. “We slightly overlap these strips like shingles on a roof. By doing that, we’re able to pack more cells in, which results in very little dead space.
“However, it requires a different assembly process, because we attach the strips together with electrically conductive adhesive,” Sharma points out. “Using adhesive greatly reduces the thermal and mechanical stresses in the cell, resulting in lower material tension.”
Like most solar panel manufacturers today, Solaria depends heavily on automation to boost throughput, maintain consistency and improve quality.
“Processes such as solar cell cutting, material handling, stringing and adhesive bonding are highly automated,” explains Sharma. “Automation is also used for end-of-line testing of electrical power (checking parameters such as current voltage and watt peak rating) and electroluminescence (checking quality issues, such as cracks inside the cells).”
One of the newest solar module factories in the U.S. is also one of the largest. Last fall, South Korea-based Hanwha Q Cells opened a $200 million facility in Dalton, GA.
The company claims the 300,000-squarefoot automated plant has the capacity to produce enough solar panels each year to generate as much peak power as the Hoover Dam.
“[The] state-of-the-art-facility uses automated module assembly equipment that permits continuous product flow,” says Markus Fischer, vice president of R&D at Hanwha Q Cells GmbH. “Cell manufacturing uses more semiconductor- or PCB-like production equipment, such as thermal processing tools and inline wet chemical process tools.
“Transport of the cells is done on belt conveyors and between the different tools with automated guided vehicles,” explains Fischer. “For solar module assembly, the main tools used are infrared soldering of strings and cross connectors. Vacuum grippers are used to move cell strings and cell matrix.”
Assembly Challenges
Continuous innovations in wafers, cells and module technology is boosting solar power output without proportionally increasing manufacturing costs. However, sun-powered devices pose numerous assembly challenges for engineers.
“PV Modules have a large area, are lightweight and require gentle handling to prevent damage,” says Camilo Orjuela, regional sales manager at Bosch Rexroth Corp. “The modules are not perfectly flat and typically travel down an assembly line directly on conveyors. In some instances, carriers are used in up-stream processes.
“Unique challenges include accurate positioning of the bus bar stringing, as well as lay-up processes,” explains Orjuela. “Modules also have to be handled by conveyors that will not mark the glass nor deposit any oily materials.”
“Solar energy manufacturers look for highly reliable components, conveyors and process equipment,” adds Mark Ziencina, regional sales manager at Bosch Rexroth. “Due to high production volumes and limited margins, overall equipment effectiveness is of utmost importance.”
To address those challenges, many manufacturers have invested in robotics and other state-of-the-art automation.
"Automation is critical to solar panel manufacturing, because the components require precise alignment and high precision,” says Chris Blanchette, executive director for global accounts at FANUC America Corp. “More than 75 percent of the production process can be automated.
“Today, there’s still a huge opportunity for growth and a need for many different types of robots,” Blanchette points out. “Delta and SCARA machines are popular for wafer handling, while large six-axis robots are ideal for handling frames, glass panels and modules.”
Advanced Automation
Another Korean manufacturer that opened a U.S. solar panel factory last year is LG Electronics. Its $28 million facility in Huntsville, AL, mass-produces a variety of 60- and 72-cell NeON 2 solar panels that are popular with homeowners.
“Many of our processes are automated, from the loading of parts to the packaging of finished goods,” says John Taylor, senior vice president of LG Electronics USA. “Advanced automation processes and robotics help us maximize productivity and minimize deviations to assure the highest quality.
“Some of the most challenging steps are related to the tabbing and lamination processes,” adds Taylor. “Tabbing involves the placement of cells along with soldering wires and cells. It’s a precise process related to the location of each cell, energization and condition of soldering. Lamination is the important process that makes solid modules by combining main parts at high temperatures.”
Automation also plays a key role at Heliene Solar Inc. The Canadian company operates a plant in Mountain Iron, MN, that uses minimal human interaction on its assembly lines to ensure quality. The plant has the capacity to produce 1,200 solar modules per day.
“[We have] dedicated ourselves to developing the most robotized systems in the industry,” claims Martin Pochtaruk, president of Heliene. “[We also have] some of the newest equipment in the industry.”
The 30,000-square-foot plant is located on reclaimed land near U.S. Steel’s Minntac iron ore mining operation. It recently ramped up to 24/7 operation to meet growing demand for its 36-, 60-, 72- and 96-cell solar modules. It’s also in the process of adding a second assembly line at a new facility in Mountain Iron that it hopes to have in operation by early next year.
“Robots are used extensively for handling components such as monocrystalline and polycrystalline cells,” says Pochtaruk. “They are more than 114 microns thin and extremely fragile. Each cell measures 156 by 156 millimeters.”
According to Pochtaruk, automation is also used for soldering strings of cells together. Heliene uses automated stringer machines that feature built-in vision inspection systems. The machines can solder up to 2,100 cells per hour via extremely small pads (roughly 1 by 0.7 millimeters) on the front and rear of the cells.
“The challenge here is to position nine narrow ribbons accurately onto the pads at high speed,” notes Pochtaruk. “The laying precision of the ribbon handling, the exact positioning of the cell on the transport system, and the patented hold-down technology of the stringers ensure that this requirement for precision is reliably met.
“Right now, we are doing five bus-bar cells, which is the most common technology,” adds Pochtaruk. “However, we [plan to use] larger cells and up to nine bus bars toward mid-2022.”
The largest solar energy manufacturer in the United States, First Solar Inc., recently expanded its footprint even further. In addition to facilities in Malaysia and Vietnam, it has plants near Toledo, OH, that produce thin-film PV modules. First Solar’s products are developed in California and Ohio, and are unlike the bulk of the PV products available today.
“This differentiation primarily boils down to the fact that our technology does not contain crystalline silicon, but instead relies on an advanced semiconductor called CadTel,” says Mike Koralewski, senior vice president of manufacturing at First Solar. "Each of our modules includes a layer of semiconductor that is 3 percent of the thickness of a human hair and less than 2 percent the width of a conventional silicon cell.
“Our [production] processes look very different from what you would see at a company that manufactures silicon panels,” explains Koralewski. “For one, it allows us to manufacture end-to-end under one roof, while the silicon industry requires multiple steps and a complex, sometimes opaque supply chain.
“This sets us apart from many of our competitors because it offers our customers unparalleled traceability and transparency,” Koralewski points out. “It also means that while our competitors take several days to finish a panel, we go from glass to module in just 4.5 hours, with a carbon footprint that is six times lower than an average crystalline silicon panel.
"We have two factories in Ohio that together form the largest solar manufacturing footprint in the Western Hemisphere," claims Koralewski. "Our factory in Perrysburg has produced multiple variants of our thin film technology. It is currently a hybrid site that facilitates both R&D and operations on the manufacturing lines in a very controlled format. It is the home of most global manufacturing support functions, and we use it as a test location and initial process development site for all improvements that are then cascaded to the other facilities."
To keep up with growing demand, First Solar recently opened a state-of-the-art $400 million facility in Lake Township, OH. The 1 million-square-foot plant mass-produces its popular Series 6 solar panels.
"We operate a continuous flow line with ID traceability, which enables process lineage and routing capabilities," explains Koralewski. "Additionally, the use of sister tools allows us to configure our process flow through specific toolsets. Importantly, in the spirit of continuous innovation and improvement, we have built-in experimental capabilities, which enables us to optimize our product through normal line mixing and duplicate process legs.
"Our global manufacturing footprint follows a copy-exact philosophy, which means that all factories have the same critical tools, process controls and configurations are fingerprinted," adds Koralewski. "This ensures that learning and improvements take place across the global fleet. All of the changes are managed and controlled through our global change management processes to ensure we get the same results [globally] as we improve our processes.
“Our process is fully automated from glass load to module unload,” says Koralewski. “There are specific areas where a manual interface is needed for loading and unloading of materials, but all of the assets, the inline buffer management and material flow are all automated. It is key to ensuring alignment across the lines and ensuring the most productive material flow.”
