Confronted with this backbreaking labor and a shortage of workers in the remote locations where projects are sited, Rosendin Senior Vice President David Lincoln wanted to see if some of this repetitious work could be automated. 

“I happened to be at a photovoltaic module manufacturer’s facility, and I saw the robot arm it had to move modules between pallets. It got me thinking: is there a way to mount a robotic arm on a small backhoe, or like a mini excavator?”

Lincoln worked with Rosendin’s internal R&D team on possible options, and they agreed there wasn’t anything on the market yet that could do everything he envisioned. But the idea of a factory-style robotic arm moving around a solar site brought them to ULC and its Robotic Roadworks and Excavation System. After a year-and-a-half of development, the two companies now have a solar installation robot up and running, and it’s been deployed on Rosendin solar projects across the country. 

“This was a completely manual process before,” says Ali Asmari, director of research and development at ULC Technologies. Solar panels are usually 3 ft by 6 ft but can be up to 4 ft by 8 ft, with mounting racks about 4 ft to 8 ft off the ground. “So what installers need to do is pick up [each] 100-lb panel onto their shoulders and put [it] onto the install rack, while balancing it with their shoulders to fasten the panel into place.” 

Asmari and his team looked at every task involved in placing and mounting the panels before coming up with their robotic approach. The basic robotic platform, a treaded robot with an articulated arm similar to the road excavation robot, has been adapted to several tasks. A robot with an arm capable of six degrees of movement uses a vacuum-based suction cup attachment to lift a panel from a stack into place on the mount rack. Then, human operators can confirm the panel is positioned properly and drive screws to secure it in place.

 

The autonomous robot can pick up and place solar panels using a vacuum suction attachment. Its electric motors are powered by batteries, which are recharged by an onboard diesel generator.
Photo courtesy Rosendin Electric

Two other robots serve as panel carriers, working in tandem to ensure there is always a fresh stack of panels for the picker robot to grab one. Typically panels are delivered on pallets to the end of each row of a solar installation by a skid steer, and workers had to carry them over uneven ground down the lane to install them. Now, the carrier robots can be loaded from the end of the row and bring the panels down as they are installed. Each panel carrier robot can carry 30 to 35 panels at a time.

The robots operate autonomously and work together as a team but wait for confirmation by human operators that a panel has been mounted before advancing. Each robot is preloaded with a KMZ map file of the project site and orients itself with GPS and Lidar, so it knows where the next panel needs to go without prompting.

This semi-autonomous workflow has led to massive productivity gains, says Asmari. “With the field trials we did, we achieved an install rate of under a minute per panel—one hour to install 60 panels. In a 10-hour shift we could install 600 panels.” By contrast, a traditional crew working in similar conditions was averaging 100 to 120 panels per 10-hour shift. Lincoln says in one particular trial the firm was able to get 350 panel modules in an eight-hour shift with only two human operators assisting.

The installation robot works with carrier robots that keep it supplied with solar panels to place as it moves down a row.
Photo courtesy Rosendin Electric

But it’s not just about improving efficiency. “As we started getting into it, we did the time motion studies and got a four-person crew down to a two-person crew, and the safety aspects of it were huge,” says Lincoln. He notes that 25% of the labor on solar photovoltaic projects is installing these heavy panel modules. “We looked at the safety issues, and strains and sprains were huge [for this workforce].” 

The robots themselves have been updated from ULC’s earlier roadway repair robot with entirely new navigation and GPS systems, as well as numerous sensors to ensure the multi-ton machines operate safely around human workers. The robots can also be operated manually via a corded controller, and all operators have hip-mounted emergency shut-off switches for them if needed.

Hardening the robots for the often rough solar installation sites took some time. The robots are able to withstand inclement weather and can navigate uneven terrain and plow through puddles and operate on up to a 30° incline. The issue of power on remote jobsites posed a challenge, and Asmari’s team settled on battery power to provide the power draw necessary for the robot’s DC electric motors to function, paired with onboard diesel generators to charge the batteries. 

With regular refueling like any other piece of construction equipment, Asmari says crews could theoretically work 24/7 if necessary. “Why not have the robots operate at night as well? We’re not limited by anything, just change out the operator crew at the end of the shift and set up proper lighting.”

With the successful trials and a return on investment in sight, Lincoln says Rosendin and ULC are now working to value engineer some robot components to get them ready for wider production. The most expensive sticking point is the drivetrain, which Lincoln says performs very well but could maybe work with a more widely available option. “We over-designed it a bit, but we’re light years ahead of anything else on the market,” he says.

Tests of the robotic system have show clear gains in efficiency, while removing human workers from some of the most physically strenuous work in solar photovoltaic installations.
Photo courtesy Rosendin Electric