Not all tracking systems need acres of land. All Earth Renewables offers an alternative to rooftops for those doing residential and small C&I work. Now on its Generation 4 Solar Tracker, AllEarth is building on the strengths and history of the first three generations. Here is what’s changed:
Structure
Made from a single-piece steel tubular axle for a sleeker look and lower part count, the biggest change is in the move from hydraulics to electrical motion actuators for tilt and yaw. “This eliminates dealing with hydraulic fluid,” according to mechanical engineer Tim Hoopes. “The electrically driven Planetary Gear Motors have a helical first stage to minimize noise for smooth and quiet operation.”
For yaw, power to the motor is ramped up and down by a pulse width modulation (PWM) algorithm in the control system to minimize impact loading for smooth operation and long life. Hoopes says this is also more energy efficient with all controls and operation using less than 1 percent of the energy production.
A custom linear actuator is used to achieve the tilt motion. The actuator design uses a large diameter ACME threaded rod for column strength.
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“We have married the strength of the hydraulic cylinder with the reliability of electric drives,” Hoopes says. “The motor is the same as the yaw system for a low part count, and a tilt feedback sensor allows for greater positional accuracy.”
Gen 4 also has continuous operation during a grid power outage. It will always go into wind hold (high wind speed shutdown where the tracker goes flat to survive hurricane force winds) since all controls are run off the 24-volt DC battery backup. The batteries are charged from the tracker PV modules with redundant chargers on two PV strings.
The inverter is mounted lower down on the mast for improved accessibility and wiring. Gen 4 also allows installation of the inverter in locations away from the tracker, which is cool when using a larger three-phase string inverter for combining two to three trackers.
Software
For Generation 3, AllEarth Renewables used a modular approach on the circuit board designs for easier installation and removal in the unlikely event of a board failure. According to Seth Maciejowski, embedded systems engineer, on the internet gateway they use a “call in only” architecture that makes installation on most customers’ networks simple and avoids complicated TCP/IP configuration.
“The fourth generation tracker integrates the communications functions into the tracker using cellular and WiFi technology to put more performance and debugging information into the hands of customers and dealers, and it more closely ties systems to our BRIGHT solar monitoring solution,” Maciejowski says. “We’ve moved to a quieter electric drive system for both yaw and tilt actuators to provide variable speed operation and battery backup for grid outages and off grid applications. Through proprietary hardware, we are able to measure DC string power directly, which will be included in the data stream provided to the BRIGHT solar monitoring solution.”
— Solar Builder magazine
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