A new report has laid out the challenges that lie along the path of decarbonizing the transport of temperature-controlled freight.
The North American Council for Freight Efficiency (NACFE) said there are both operational and cost hurdles while highlighting the benefits in a report titled Decarbonizing Truck and Trailer Refrigeration – Zero-Emission Temperature Control in Trucking.
“Electric is the future,” Mike Roeth, NACFE’s executive director said during a press briefing. He noted that electric motors and batteries are mature technology and is confident in the electrification process.
Fresh produce and other perishable foods, pharmaceuticals, electronics, plants, and flowers are sensitive to temperature. Other products, such as dairy products, chocolate/candy, eggs, meats, fish, frozen foods, paints, and other chemicals, require temperature control during shipping.
15% of straight trucks and trailers
About 15% of the straight trucks and trailers built are refrigerated using a transport refrigeration unit (TRU), according to the report.
TRUs create cold or warm air, which is then pumped into a box that needs to be at a certain temperature to protect its contents. There are several ways to do this, but diesel fuel has been the primary energy source for powering TRUs for the past century.
The primary way to eliminate emissions from TRUs is to replace the diesel-fueled ICE driving the compressor with an electric motor. These so-called electric transport refrigeration units, or eTRUs, are generally powered by either the traction battery when installed on an electric straight truck chassis or by dedicated batteries when installed on a trailer.
Benefits of eTRUs compared to conventional TRUs include fuel cost savings, noise reduction, and maintenance savings.
Rob Graff, NACFE’s senior technical advisor and the report’s lead author, noted that fleets can save money when they plug the eTRU into shore power as it is cheaper, especially for trailers parked at a facility. He admitted there are capital costs to install charging infrastructure.
Regulations driving transformation
Regulations are also driving the transformation. California Air Resource Board (CARB) regulations require that all self-powered TRUs on all straight trucks be zero—emission—which almost certainly means electric—by 2030. As part of the broader movement toward truck electrification, non-regulatory factors also expand interest in electric TRUs (eTRUs).
This can be a large challenge as today’s diesel eTRUs run off the diesel truck’s engine or from dedicated engines integrated into the TRUs. These have long run times for when the vehicles are in motion or sitting at warehouses or stores to be loaded or unloaded.
Truck drivers will have to perform their duties differently with eTRUs. Because the batteries powering an eTRU require time to recharge, they will need to time that charging with mandated driver rest periods. An electric truck operator is likely to have to charge the eTRU battery separately from the truck itself.
If they are fueling a diesel truck, the operator will likely need to charge the batteries for the eTRU at a different location. Also, the driver is likely to be given the responsibility for ensuring the eTRU is plugged into shore power at the loading dock or in the yard and to ensure that the plug is removed and properly stored before driving
There also are a variety of cost challenges associated with moving to eTRUs. These include the initial purchase price, which is higher than that of a diesel-powered TRU. In addition, there is the cost of the electric charging infrastructure needed to support the battery-electric eTRU units as well as the cost of a shore power connection.
Shore power availability
These include equipment availability, availability of electricity for shore power, on-the-road charging appropriate for charging eTRU batteries, the need for emergency backup power, and regulatory challenges.
A battery-powered eTRU attached to either a box truck or to a reefer trailer hauled by a diesel tractor needs to be charged. NACFE is not aware of any diesel fueling station set up to charge eTRU battery systems, the report said.
The report found that new refrigeration units have been developed to run with zero emissions using electricity. These include all-electric units, some with significant battery storage, systems that accept plug-in shore power as a source, and hybrid units that run primarily on electricity but have diesel or other powertrains to support long run times.
Allied solutions are emerging to support eTRUs, including increased insulation or incorporating cold plates into the truck or trailer bodies, and solar or axle-mounted generators to deliver more power to the batteries.
‘Cleaner’ solutions compete for resources
The report found that moving and delivering refrigerated goods with zero or significantly lower emissions while maintain quality is a large challenge. “Although independent of electric truck propulsion units, these ‘cleaner’ solutions compete for resources, but also benefit from developments, such as improved battery size, weight and cost. Delivering reliable, durable and cost-effective solutions quickly has many challenges,” the report said.
Researchers found that activities are underway to plan for and harmonize connectors and power requirements for charging electric trucks and eTRU batteries and providing shore power when electric reefers are parked or idling.
The broad efforts being made to provide charging infrastructure for electric trucks should be expanded to incorporate the requirements of electric transport refrigeration units, the report suggested.
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