10
Table 2 Technology Options for Reducing Overnight Diesel Engine Idling
a
Technology
Function
Benefits
Drawbacks
Technology
Status
Direct-fired heater
Heating for
cab/sleeper and/or
engine.
cab/sleeper and/or
engine.
Can be used at any stop
for heating. Small and
lightweight.
for heating. Small and
lightweight.
Cannot provide cooling.
Requires battery power
and may be unreliable
when not equipped with
automatic engine starting.
Requires battery power
and may be unreliable
when not equipped with
automatic engine starting.
b
Commercial.
Auxiliary power unit
Heating and air-
conditioning of
cab/sleeper, heat
for engine, and
power for
auxiliaries.
conditioning of
cab/sleeper, heat
for engine, and
power for
auxiliaries.
Can be used at any stop
for heating, cooling, and
auxiliaries. Recovers
waste heat for space
heating. Serves as
survival system.
for heating, cooling, and
auxiliaries. Recovers
waste heat for space
heating. Serves as
survival system.
Heavier and larger than
direct-fired heater. May
require separate sleeper
air conditioner.
direct-fired heater. May
require separate sleeper
air conditioner.
Commercial.
Thermal storage
Heating and air-
conditioning for
cab/sleeper only.
conditioning for
cab/sleeper only.
Driver comfort.
Does not heat engine.
Requires relatively large
space for storage medium.
Performance dependent
on truck use.
Requires relatively large
space for storage medium.
Performance dependent
on truck use.
At or near-
commercial.
Commercial in other
applications.
commercial.
Commercial in other
applications.
Direct heat with thermal
storage cooling
storage cooling
Heating and air-
conditioning of
cab/sleeper and
heat for engine.
conditioning of
cab/sleeper and
heat for engine.
Can be used at any stop
for heating and cooling.
for heating and cooling.
Requires battery power.
Commercial.
Truck stop electrification
Provides electricity
for heating, air-
conditioning, and
auxiliaries.
for heating, air-
conditioning, and
auxiliaries.
Provides power for heating
and cooling and
auxiliaries.
and cooling and
auxiliaries.
Limited choice of over-
night location. Requires
separate sleeper air
conditioner and electrically
powered heater. Requires
infrastructure at the truck
stop.
night location. Requires
separate sleeper air
conditioner and electrically
powered heater. Requires
infrastructure at the truck
stop.
Not commercial.
Commercial in other
applications.
Commercial in other
applications.
a
Excludes timer devices.
b
A thermoelectric device is being developed by Hi-Z Technology that promises to reduce the need for battery power
(HiZ 1996).
(HiZ 1996).
References: Direct-fired heater: Espar (undated); Thermal storage: PCG (1995).
In addition, thermoelectric devices that reduce the battery power needed by direct-fired
heaters are in the research and development stage (HiZ 1996). HiZ Technology proposes to
modify its current-production 14-W and 24-W units for operation on direct-fired heaters.
Thermoelectric devices convert heat directly to electricity. They would be installed on the hot
end of the direct-fired heaters and provide some power for the cab/sleeper heater. However,
thermoelectric devices are not yet commercial and do not totally eliminate battery use.
modify its current-production 14-W and 24-W units for operation on direct-fired heaters.
Thermoelectric devices convert heat directly to electricity. They would be installed on the hot
end of the direct-fired heaters and provide some power for the cab/sleeper heater. However,
thermoelectric devices are not yet commercial and do not totally eliminate battery use.
Auxiliary power units (APUs) are mounted externally on the truck cab or sleeper and consist
of a small internal combustion engine (usually diesel) equipped with a generator and heat
recovery to provide electricity and heat (see Figure 4). For air-conditioning, an electrically
powered air-conditioner unit is normally installed in the sleeper area, although some units use the
recovery to provide electricity and heat (see Figure 4). For air-conditioning, an electrically
powered air-conditioner unit is normally installed in the sleeper area, although some units use the