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Section 4
Potential Implications
of New Technologies
4.1 Reduced Energy Use
Fuel consumption is reduced by eliminating unnecessary engine idling. Table 3 provides
data on (1) the energy used during engine idling when providing heating and (2) the energy
required for several alternatives to idling, including truck stop electrification. Note that the heater
and storage systems are not directly comparable with the other alternatives because they do not
provide the full range of services. Appendix B contains more detailed information about
emissions data, while Appendix A provides equipment and emissions data. About 10,650 Btu/h
is needed to keep the engine warm, which is done by warming the coolant, and an additional
~4,100 Btu/h is needed to provide cab/sleeper heating. Heating can be supplied by circulating the
coolant if it is being warmed or by providing a separate air heater. (The engine requires more
heat because it is not insulated.) These requirements are based on medium settings for the Espar
heating system. More heat is provided at higher settings with additional fuel consumption; other
units have similar capacities. Energy requirements can be reduced by better insulating the truck
and by using sunshades during daytime stops. Insufficient data were available to do a complete
analysis of cooling systems; therefore, most of the discussion here focuses on heating.
required for several alternatives to idling, including truck stop electrification. Note that the heater
and storage systems are not directly comparable with the other alternatives because they do not
provide the full range of services. Appendix B contains more detailed information about
emissions data, while Appendix A provides equipment and emissions data. About 10,650 Btu/h
is needed to keep the engine warm, which is done by warming the coolant, and an additional
~4,100 Btu/h is needed to provide cab/sleeper heating. Heating can be supplied by circulating the
coolant if it is being warmed or by providing a separate air heater. (The engine requires more
heat because it is not insulated.) These requirements are based on medium settings for the Espar
heating system. More heat is provided at higher settings with additional fuel consumption; other
units have similar capacities. Energy requirements can be reduced by better insulating the truck
and by using sunshades during daytime stops. Insufficient data were available to do a complete
analysis of cooling systems; therefore, most of the discussion here focuses on heating.
The idling fuel-use rate varies, depending on equipment load and engine speed. To avoid
engine wear due to low-speed idling, most truckers idle their engines at 1,000 rpm with some
load. The Truck Maintenance Council (TMC) suggests fuel flow rates for various loads and
engine speeds in its Recommended Practice Bulletin 1108. Diesel engine idling consumes about
one gallon of diesel fuel per hour when the truck's heating or air-conditioning system is operated
(for 5 brake horsepower load at 1,000 rpm; TMC 1995), or about 128,500 Btu/h (the newest
engines consume slightly less). Note that the engine is only about 11% efficient when used to
heat the cab/sleeper and the block (14,750 Btu/h output [cab/sleeper heater plus engine block
heater] divided by 128,500 Btu/h fuel consumption).
load. The Truck Maintenance Council (TMC) suggests fuel flow rates for various loads and
engine speeds in its Recommended Practice Bulletin 1108. Diesel engine idling consumes about
one gallon of diesel fuel per hour when the truck's heating or air-conditioning system is operated
(for 5 brake horsepower load at 1,000 rpm; TMC 1995), or about 128,500 Btu/h (the newest
engines consume slightly less). Note that the engine is only about 11% efficient when used to
heat the cab/sleeper and the block (14,750 Btu/h output [cab/sleeper heater plus engine block
heater] divided by 128,500 Btu/h fuel consumption).
The engine provides cab and engine block heating as a by-product of producing shaft work,
but a directly fired heater avoids the losses associated with the production of shaft work by
simply indirectly heating the air that enters the cab/sleeper area. A typical furnace efficiency is
80
simply indirectly heating the air that enters the cab/sleeper area. A typical furnace efficiency is
80
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85%. Therefore, the direct-fired heater for providing cab/sleeper and engine heat is extremely
efficient compared with engine idling or electric heating. Assuming that the battery energy
consumed during heater use must be supplied by the engine after restart, the energy requirement
is about 18,540 Btu/h, yielding an overall efficiency of 80%. Efficiency of the APUs is high as
well, because the engine is sized to meet electricity and heat requirements.
consumed during heater use must be supplied by the engine after restart, the energy requirement
is about 18,540 Btu/h, yielding an overall efficiency of 80%. Efficiency of the APUs is high as
well, because the engine is sized to meet electricity and heat requirements.
Data were not available to evaluate energy consumption by the storage systems. Product
literature states that thermal storage units require energy (~50 W) for operating fans and