Transport refrigeration system batteries are increasingly being tapped to power additional electronics such as telematics devices, fuel-level sensors, interior trailer lighting and other accessories. Because these accessories can continue to draw power – sometimes up to a few amps per hour – while the refrigeration unit is off, the reefer battery might not have enough charge to start the engine if the unit has not been operated for some time. That could mean an expensive jump-start, and it also means trailers drop off of asset-tracking systems.

But solar power options are coming to the rescue for some fleets.

K&J Trucking started testing Thermo King’s ThermoLite solar panels four years ago on five trailers. After two years, the Sioux Falls, South Dakota-based refrigerated fleet liked the results well enough to spec them on a new trailer order replacing half its trailer fleet. By that point the return on investment was clear, according to Maintenance Manager Lou Charette.

“The solar option works well for us on the reefer end, because trailers get into places [where they shouldn’t], and with tracking devices they tend to drain batteries in a two-to three-week period,” he says. “A trailer shouldn’t sit that long, but they do, it’s as simple as that. With this, the battery is constantly ready.

“It makes it so we can spot the trailer at any time, because if the battery goes dead, the GPS tracking goes out.” The solar option also eliminates middle-of-the-night service calls for jump-starting, “and any service call starts at $300 these days.”

In addition, battery life has been significantly extended.

Thermo King’s ThermoLite solar panel solution was developed to provide an alternative power source to both refrigerated and dry van fleets and offset battery drain from parasitic loads. It allows Thermo King’s TracKing or other telematics systems to monitor assets over long periods of time, even when the refrigeration unit is off and the trailer’s untethered from the tractor.

Carrier Transicold also offers a solar power solution. Its Thin Film Flexible Solar Panels are specifically designed to maintain the refrigeration unit’s battery charge. They can be installed on the roofs of trailers and truck bodies chilled by Carrier Transicold or other systems.

“Without solar panels, the traditional way to maintain battery charge would be to start up and run the TRU periodically, even when not in service, to make sure the battery is being kept charged by the unit’s generator,” notes Carrier's Jason Forman, sales & marketing manager, Truck Trailer, Performance Parts. “That, of course, burns extra fuel and can tie up manpower.”

He says Carrier Transicold’s solar panels, unlike some other solar-powered solutions, do not require direct sunlight. “Their amorphous silicon solar cell technology performs reliably even in low- and indirect-lighting conditions. As long as there is daylight, they will generate a charge, and that includes on cloudy days.”

In addition to Thermo King and Carrier, there are some other companies offering broader-based solar panel products that they say can be used for truck or trailer refrigeration among other uses. For instance, eNow offers a broader-purpose solar panel system it calls eCharge, which can be used on tractor or trailer. And Purkeys has a product called Solar Bolt. Installed on the roof of a trailer, it provides a constant charge to electrical accessories such as liftgate batteries and reefers. There also are options to use solar power for stand-alone trailer tracking/telematics systems.

“We’ve seen interest in solar technology from fleets of all sizes,” Carrier’s Forman says, “but the first applications to embrace it are rail operations, where unattended operation is the norm, and long-distance haulers that have invested in systems to optimize efficiencies and performance, which includes reliable power for starting. Fleets also appreciate the worry-free, automatic nature of solar charging.”

Learn more about solar power in the September issue of Heavy Duty Trucking.