Environmental Engineering Reference
In-Depth Information
In units that operate in chilling mode, precise control is important to transport products
such as meat and fruits. In this case, circulation fans are operated at full blast and the compres-
sor runs constantly, while temperature control is achieved by modulating refrigerant flow.
When transporting fruits and vegetables in containers without controlled atmospheres, carbon
dioxide and ethylene resulting from respiration need removal by renovation of air inside the
containers with external air, which increases the refrigeration load even more. Power con-
sumption in chilling mode can oscillate between 6 to 10 kW. When controlled atmospheres are
used, then a nitrogen generator is also a necessity. The typical combined power of a refrigera-
tion unit and nitrogen generator for a reefer rises to around 15 kW (Container Handbook,
2010). It is important to point out that all these power consumptions are typical, and they
depend on the insulation of the container, ambient temperature, sun exposure, and where the
reefer is located (upper deck or below deck of container ships).
In refrigerated trucks power requirements are around 11 kW for a distribution van and 23 kW for
a large trailer unit. The higher refrigeration powers are necessary to achieve a fast recovery every
time doors are opened. In terms of energy per amount of cargo and distance, the refrigeration part
of refrigerated trailer trucks has an energy intensity of around 0.18 MJ/ tonne km (Heap, 2003).
EMISSIONS FROM TRANSPORTATION
Emissions from transportation are more or less proportional to the energy intensity or each
mode. Table 13.5 presents energy intensities and emissions for different transportation sys-
tems. The reader can compare the more specific energy intensities presented in Table 13.5
with the typical ones shown in Figure 13.4.
Diesel-powered vehicles
Diesel is the fuel of choice for all cargo transportation with exception of planes that use jet fuel
(kerosene). Burning diesel in transportation vehicles is a direct mobile source of air emissions
with global, local, and regional scale impacts (see Chapter 8). In addition to carbon dioxide
Table 13.5
Energy intensity and emissions for different modes of transportation.*
Mode
Energy intensity
(MJ/tonne-kg)
Emissions (g/tonne-km)
Carbon
dioxide
Nitrogen
oxides
Volatile organic
compounds
Sulfur
dioxide
Aircraft
500 km
19.5
1420
4.33
0.65
0.42
1500 km
11.0
800
2.66
0.25
0.23
Truck
35 tonnes
a
1.34
100
1.20
0.05
0.03
20 tonnes
a
2.77
200
2.26
0.10
0.05
Train
Diesel
0.95
69
1.22
0.07
0.08
Electric
0.83
38
0.07
0.00
0.21
Barge
0.54
40
0.69
0.04
0.04
Coaster
b
Diesel
0.19
13
0.26
0.01
0.02
Fuel oil
0.17
12
0.32
0.01
0.24
*Compare these energy intensities with the ones from Figure 13.4.
a
Gross vehicle weight.
b
Coastal trading vessel with a shallow hull.
From Dings and Dijkstra, 1997, as cited in Bonnafous and Raux, 2003.
