NACFE Report: Guidance on a Cleaner, Greener Reefer Fleet
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The published its guidance report, “Decarbonizing Truck and Trailer Refrigeration: Zero-Emission Temperature Control in Trucking” on the growing availability of greener transport refrigeration units.
These are reefers that avoid the use of diesel engines or, in some cases, significantly reduce diesel emissions by enabling the use of shore power when the trailer is parked. Two types of units enable a diesel-powered reefer to switch over to shore power while parked at a warehouse or supermarket, and straight battery-electric units are available, too.
The report’s goal is to help fleets navigate the difficult task of reducing their carbon footprint. It also lays out challenges in the hope that the industry will solve some problems in unifying requirements, for example, charging station electrical connections.
As might be expected, the primary force behind the movement is requirements for this year that apply to any transport refrigeration units that operate in that state. The rules, which require increasing percentages of zero-emission reefers, may soon migrate to at least 15 additional states.
Baxter
California requires 30% of the units a fleet operates in that state to be zero-emission by the end of this year, 75% by 2027 and all units by 2029. A fleet that is unable to make the switch because of limited charging stations or equipment availability problems can apply for an extension.
But even for fleets not operating in California, marketing benefits can come from adopting low- or zero-emission technology. Some shippers may wish to lower their carbon footprint, and fleets can sell their services by lowering the carbon emissions of their reefers, thus helping their shippers make that claim. Also, any reefer that can run on shore power when parked helps to prevent local political pressure to move the warehouse to another location.
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The primary driver of these regs is the emissions of particulate, NOx, and noise that accompany reefers when they operate while sitting at warehouses or supermarkets in urban areas. That’s why some units can easily be hooked to shore power when they operate while parked.
It’s important to remember that some products such as frozen foods just need to be kept cold enough, while others, including electronics and drugs, need to be kept within a narrow temperature range. That means freezing prevention in Minnesota in winter, not just cooling. Potato chips are bagged with nitrogen under pressure to prevent breakage, which means they must be temperature-controlled if the box or trailer climbs into the mountains.
Possible Headwinds
The guidance report provides a comprehensive list of the challenges when adopting battery-electric or eTRUs (battery-electric truck refrigeration units) including:
• Battery capacity is a major consideration as sizing batteries properly for the actual operating mission is critical. Too big for the job means loss of payload since most refrigerated loads are weight-limited, while, obviously, running out of power before the load is delivered means spoilage.
• There will inevitably be a weight penalty because batteries and power electronics make an eTRU unit heavier than a diesel unit.
• Operators need to be trained to be extra careful about operating factors that drain the batteries such as unnecessary door openings and failing to plug into shore power whenever it’s available.
• Maintenance workers need to be trained to safely handle the much higher voltages used in eTRU units and to be extra vigilant about upkeep of items such as door seals, which greatly add to heat gain and loss when deteriorated.
Source: "Decarbonizing Truck and Trailer Refrigeration: Zero-Emission Temperature Control in Trucking”
Information about maximum and minimum temperature limits quickly becomes relevant to planning for the use of battery-electric units when range inevitably becomes a concern in either very hot or very cold weather, hence a chart showing what kinds of products must be shipped within the various temperature (and humidity) limits is in the report.
The report includes diagrams of how the various systems work, including one on how a conventional vapor-compression refrigeration system operates. The process involves a compressor in nearly all cases. The primary difference between the traditional diesel-powered TRU and a zero- or low-emission unit is how the compressor is powered — all use the same refrigerant cycle.
The report also deals with there being longhaul single-temperature loads and regional, multitemp loads that might include, for example, frozen meat in one part of the trailer and fresh vegetables in another. The additional complexity of multitemp units means that there are at present no multitemp eTRUs on the market.
The report does not distinguish between a standard mechanically driven compressor typical of conventional diesel units as well as standby units and the hermetic compressor used in hybrid units. The hermetic compressor eliminates the shaft seal required in standby units, which is a maintenance item.
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Standby units have a mechanical coupling that allows either the diesel or electric motor powered by the grid to turn the compressor shaft, which has a mechanical seal — a potential leak point and maintenance item. Hybrid units employ a hermetic compressor, which means that the compressor and the electric motor that powers it are both housed inside a sealed chamber. This not only eliminates the mechanical shaft seal, it also allows the cold suction gas coming from the evaporator to cool the motor that drives the compressor, making it more efficient. This minor omission suggests that when a fleet begins evaluating the various types of units it may purchase, a trained refrigeration mechanic from the maintenance staff should be involved in the decision making.
Readers should note that both standby and hybrid units use high-voltage AC current when parked and running off shore power, while some eTRUs have a separate system for charging and running while parked that use DC power.
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This brings us to two of the vitally important points made by the report. Shore power saves money and reduces the noise level substantially, in addition to reducing harmful emissions. Diesel reefer fuel costs about $2.60 per hour using just over a gallon of fuel. Powering the unit electrically uses about 8.1 kilowatt-hours with each hour costing about $1.01.
The noise level of a typical diesel unit versus one running on electricity is said to be about the difference between standing next to a power mower and holding a normal conversation, or about 87% less noisy.
The report includes much more information than can possibly be outlined here including a number of valuable charts and, at the end, a list of challenges that any fleet adopting new technology, and the entire industry, face. Studying it is essential for any fleet wishing to adopt technology that ultimately will help it navigate a future in which carbon emissions, harmful local emissions such as particulate and NOx, and noise emissions are an increasing focus for reefer units.
To access the report, go to https://NACFE.org
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