Solar Panels for Trucks and Trailers, the Time has Come

July 2, 2018

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While solar panels have been used for decades to produce power for residential and commercial buildings, their application in the trucking industry is much more recent. The good news is that solar panels for trucks have been able to capitalize on the reduced costs and increased efficiency that were gained in residential and commercial application of solar panels.

Solar panels for trucks capitalize on reduced costs and increased efficiency gained in residential and commercial applications, the solar technology for trucks provides solar panels that are flexible, thin, easily installed and reliable.

As a result, some fleets have begun using solar including several who participated in the North American Council for Freight Efficiency’s Run on Less, cross-country road show last fall where trucks averaged 10.1 MPG.

NACFE recently released a Confidence Report on the use of solar technology on both tractors and trailers to help fleets determine if solar panels make sense in their application.

When evaluating whether solar panel systems are a good choice, fleets need to consider the following factors:

  • System installed cost.
  • Panel rating vs. physical size. In some cases, the area to mount the solar panel may be limited.
  • Is the fleet’s battery replacement rate excessive?
  • Is the number of roadside assistance calls to jump start or replace batteries high?
  • Area of the country that the vehicle predominantly operates in.
Solar Panels on Trucks Supports Battery HVAC Systems, Hotel Loads

Creature comforts have become more important than ever given the current driver shortage. This includes auxiliary climate control systems like cabin heating, ventilation and air conditioning, which are now common in sleeper tractors and even some day cabs.

Battery HVAC systems have become popular as a result of anti-idling and noise ordinances. Solar helps extend the runtime of battery HVAC systems.

Battery HVAC systems have become popular as a result of anti-idling and noise ordinances across the country. However, historically, many battery HVAC systems have not been able to provide enough cooling capacity for long rest periods or when operating in very hot temperatures. Solar can help with this issue because it can extend the runtime of battery HVAC systems. The idea here is not just to help the HVAC system make it further through the rest period before the engine has to be started, but also to reduce the load on the alternator the next driving period, resulting in a small amount of fuel savings. In addition, due to less battery deep cycling, solar may be able to extend battery life. Another benefit of having solar connected to the truck batteries is that it potentially reduces, if not eliminates, costly roadside assistance calls for dead batteries. A properly wired and managed solar system is able to trickle charge the truck’s batteries, ensuring they maintain a minimum voltage, whether over a 10-hour rest period or a 34-hour restart.

Another application of solar for tractors is to help power hotel loads for sleeper tractors without a battery HVAC. As electric devices and appliances become more popular and more expected in cabs, these items can place an enormous load on the truck’s electrical system. Examples of devices that contribute to hotel loads include refrigerators, TVs, coffee pots, microwave ovens, laptop computers, CPAP machines, cell phone chargers and DVD players. These devices can draw from 10 to 1,200 watts or more. A solar panel mounted on the tractor can provide a small but constant current to the batteries, helping ensure there is enough power to support hotel loads and keep the truck’s batteries charged.

With any technology, there are challenges. With solar those include initial system cost and installation, variable results based on geographic location, weather, etc., trade cycle of tractor, unclear residual value, not portable from truck to truck.

Trailers Benefit from Solar Panels too

An issue that frequently occurs on trailers with liftgates and other loads is that the voltage drop caused by electrical resistance in the long wire lengths and connections is high enough that sufficient current is not available to the trailer batteries to charge them at a reasonably fast rate. When this happens, the batteries can run out of capacity before the end of a shift and result in the need for emergency roadside assistance to replace or jump-start the batteries.

A solar panel and charge converter mounted on the trailer to supplement the current that is coming from the tractor for battery charging can solve this problem. As long as the sun is shining, the solar panel can provide a small but constant current to the trailer batteries that will supplement any power that is coming from the tractor or refrigeration unit alternator.

A common use of solar on trailers are for liftgate telematics and refrigeration unit support. The extra power available from the solar panel can augment that coming from the engine alternator and ultimately maintain the liftgate batteries at a higher average state of charge.

In addition, if a trailer has small electrical loads like a telematics system, then a small solar panel that ensures that the system will have virtually 100% availability for trailer location and other related data makes a great deal of sense.

Refrigeration unit manufacturers and aftermarket suppliers are now selling small solar panels that can be mounted on the unit or on top of the trailer to help maintain the state of charge of the battery, especially when the unit is turned off. These solar panels are essentially automatic trickle chargers that supply a small current to the battery any time the sun is shining. In these third instances, the solar panels will not provide nearly the full amount of power necessary to run these devices, but their supplementary power can be quite helpful to the overall operation of the trailer.

A common use of solar panels on trailers is to supplement the current coming from the tractor battery to support liftgate operations, liftgate telematics and refrigeration unit support.

The Confidence Report reached four key conclusions about the use of solar on tractors and trailers.

  1. 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 application 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.
  2. Fuel savings are generally a very small part of the overall benefit that comes from a solar panel installation.
  3. Solar panel installations need to be sized appropriately for their intended application. For example, the size of a solar panel to support a battery HVAC system on a tractor might be limited by the area available on the tractor fairing, whereas a solar panel to support a refrigeration unit only needs to be large enough to provide a small trickle charge to the refrigeration unit starting battery.
  4. There is not yet hard evidence from fleets that the payback from the investment in solar panels matches that claimed by the solar panel suppliers. NACFE has verified that the benefits fall in several categories with the biggest benefits being from extending battery life and avoiding emergency roadside assistance for dead batteries. Many fleet users are happy with the investment they made and intend to continue to use solar panels in the future

If you have not already looked into adding solar to your tractor or trailer, now is a good time to seriously consider investing in it.