It seems there has been a lot of interest in solar panels lately. Back in 2018, NACFE thought there was enough interest to warrant a deep dive into the subject and the result was our confidence report, Solar For Trucks and Trailers. The extra power available from the solar panel(s) can augment that coming from the engine alternator, maintaining the batteries at a higher average state of charge, extending battery life.
See also: Newest NACFE report finds all medium-duty box trucks electrifiable
The conclusions from that report are still valid.
Solar technology for trucks has progressed to the point where the panels on the market are flexible, thin, easily installed, and reliable. Some applications, like supporting the batteries for trailer telematics systems, are an excellent applications of the technology and should be strongly considered for future purchases. For other applications of solar technology, the cost versus benefits should be evaluated to see if it makes sense in the specific application.
Fuel savings are generally a very small part of the overall benefit that comes from a solar panel installation.
Solar panel installations need to be sized appropriately for their intended application.
There is limited evidence at this point from fleets that the payback from the investment in solar panels matches that claimed by the solar panel suppliers. Benefits fall into several categories, with the biggest benefits being from extending battery life and avoiding emergency roadside assistance for dead batteries.
One thing that I think would help speed the adoption of solar panels is if they were integrated into trucks and trailers rather than being add-on items. This has been done with solar panels on refrigeration units. Those panels are small—27 watts—and are there to help maintain the charge on the reefer engine starting battery and maintain the telematics system’s batteries.
The solar panel that mounts on the top of a trailer is a 50-watt unit and that is too small to provide anything other than a trickle charge for batteries. However, solar is still a great technology for trucks but we need to be careful that we don’t interpret it as being able to provide extra power for the propulsion of the vehicle or a lot of refrigeration of the cargo. And don't forget, with today’s lead acid batteries maintaining battery charge levels when the vehicle is stationary is very helpful for battery life.
As we move into a battery-electric future, I expect to see even more interest in solar panels as a way to extend the range of the batteries powering the vehicle. I expect to see more work done to make solar panels even more valuable to trucking because more fleets are expressing interest in them as a way to extend battery life and to use that free energy from the sun.
Michael Roeth has worked in the commercial vehicle industry for nearly 30 years, most recently as executive director of the North American Council for Freight Efficiency (NACFE). He serves on the second National Academy of Sciences Committee on Technologies and Approaches for Reducing the Fuel Consumption of Medium and Heavy-Duty Vehicles and has held various positions in engineering, quality, sales, and plant management with Navistar and Behr/Cummins.
