A shiny silver robot zips along a track at a county jail in Dublin, California, and stops beside a set of solar panels propped up by a giant arm. The robot latches onto the base of the arm and turns it slowly, tilting the face of the panels like flowers to the sun. By angling the solar panels just so, the robot helps the panels catch more rays and produce more energy.
This robot, about the size of a microwave oven, is the brainchild of QBotix, a three-year-old company based in Silicon Valley that unveiled its creation last year. While tilting solar panels to track the sun's movement isn't a new concept, QBotix has come up with a novel approach that makes use of advances in robotics technology made over the past two decades. If the idea proves successful, it could lead to cheaper renewable energy and more efficient use of land for big solar installations.
Such innovations are important if solar electricity is to achieve costs comparable to power generated by fossil fuels such as coal and natural gas. And in a time when many solar plants are being built or planned for remote desert regions, where sunlight and broad swaths of undeveloped land are abundant, robotics offer a way to minimize the need for on-site workers to clean, repair and monitor solar panels and tracking equipment.
Construction of a large-scale solar power plant today typically requires armies of workers to dig ditches, pour concrete, remove trees, weld beams, and distribute materials, among other tasks. Once a project gets up and running, plant operators usually employ people to clean the panels using a hose and giant squeegee, or heavy machinery equipped with a mechanical arm for spraying and wiping. Other workers are needed to repair or replace problematic panels and parts, and solar plant operators sometimes hire pilots to fly over their arrays and snap infrared images to spot cracks, short-circuits, and other malfunctions that cause a panel to heat up. Tilting solar panels to track the sun is accomplished, if at all, by means of hundreds of costly motors and tons of steel.
QBotix's design, deployed at five pilot sites in California, Arizona and Japan, sends robots zipping along an elevated monorail constructed alongside rows of solar panels. Each battery-powered bot is programmed to adjust more than one thousand panels in a carefully choreographed sequence, tilting each panel in its assigned flock by 10 degrees every 40 minutes to keep pace with the sun’s arc. When its battery charge runs low, the robot maneuvers itself to a charging point atop the monorail, and plugs in.
"You want to produce as much as energy from the solar panels as possible because that energy is your revenue," says Wasiq Bokhari, founder and CEO of QBotix. Utilities are often willing to pay a premium for renewable power delivered during times of high demand, such as the mid-afternoon, in large part because of ambitious renewable energy mandates by state or local governments. These efforts to reduce carbon emissions have fueled a boom in solar plant development, particularly in western states such as California, where utilities must increase the amount of renewable electricity in their supplies to 33 percent by 2020.
In a conventional solar farm, panels in the Northern Hemisphere are permanently positioned to face south (in the Southern Angle, north-facing panels capture more sun). But with this design, known as “fixed-tilt,” panels face the sun directly for only a few hours each day.
To squeeze more electricity out of each panel, large solar project developers in recent years have begun adding a system of motors, sensors, and other gear to the steel structure that props up each solar panel. This system, called a tracker, helps to increase energy output by automatically rotating panels to keep them oriented to the sun’s rays.
Trackers, however, are expensive. Each tracker has its own motor and gear to rotate a set of several panels. They function best on a level surface, so uneven ground must be graded. This adds cost and can impact the environment in a way that makes it more difficult to secure permits. And only the priciest systems tilt panels on two axes—east-west and north-south—enabling maximum sun exposure during all seasons. (Lower-cost versions tilt panels only east-west.) As a result, conventional tracking systems force project owners to choose between investing extra time and money to generate additional energy, or opting for a less costly system that will generate less revenue.
Robots can offer a happy medium, providing the lower price of a single-axis tracker system with the higher energy output of a premium dual-axis system. “Traditional dual-axis trackers require more motors and steel,” says Randy Wu, general manager of development at Trina Solar, a solar panel maker and project developer that plans to offer QBotix’s technology as an option in the plants it builds for investors. “QBotix’s approach is very different,” he adds, because one QBotix robot can do the work of hundreds of dual-axis trackers. The design eliminates the need to install a field of motors and the elevated rail makes grading unnecessary. “They control the environment by putting robotics on a rail," says Geoffrey Kinsey, director of photovoltaic technologies at the Boston-based Fraunhofer Center for Sustainable Energy Systems.