How solar-charged HVAC keeps trucking cool

How solar-charged HVAC keeps trucking cool
Mike Roeth
Tue, 08/11/2020 - 00:01

When most businesspeople travel for their jobs, they retire to their hotel room at the end of the day. However, when long-haul truck drivers are finished with their work, they move to the back of their truck cab into what is called the sleeper compartment.

Long-haul, over-the-road truck drivers typically are out on the road anywhere from one to three weeks at a time, delivering the goods we need for our daily lives. Most drivers spend their off-duty time in the sleeper compartments of their trucks, sometimes keeping the truck idling to get power and to cool or heat their space. This idling creates a significant amount of increased emissions, noise and wear on the main engine.

To reduce fuel consumption — which by extension decreases emissions — trucking fleets are using auxiliary electric battery HVAC (heating, ventilation and air conditioning) units in combination with solar panels installed on truck roofs.

Idling to keep cool

Providing an acceptable environment to rest and work is critical. Most important, drivers need access to heating and cooling for their comfort and health. In addition, there is the need for electric power for entertainment, completion of necessary work-related paperwork, cooking, etc. While all these so called "hotel" loads consume energy, the biggest energy draw has been the vehicle’s air conditioning system.

Historically, drivers’ power needs were supplied by idling their vehicles’ 400 plus horsepower engine. It was common for trucks to have 50 percent idle time during the summer, meaning if they drove for 11 hours, the truck would idle for 11 hours while the driver was not driving. That amounts to over 2,000 hours per year of non-driving idling, which is costly and loud and generates emissions, and which can nearly completely be removed.

Reducing idling time

The trucking industry has made amazing progress in lowering emissions from these hoteling loads and today long-haul trucks typically have a small unit known as a battery HVAC or electric auxiliary power unit (APU) installed either at the factory when the truck is produced or added later once the fleet takes ownership of the vehicle.

These battery-powered units have allowed fleets to significantly reduce their idle time. However, as the effects of climate change have caused higher temperatures, the battery HVAC systems are not powerful enough for long amounts of time. These systems have enough power to make it through a driver’s mandated 30-minute rest break after up to 11 hours of driving. However, they often can’t make it through the 10 consecutive hours of off-duty time mandated after 11 hours of driving.

Battery-powered units have allowed fleets to significantly reduce idle time. But as the effects of climate change cause higher temperatures, the battery...