Environmental Engineering Reference
In-Depth Information
pared and a more elaborate formula (Eq. 2) was selected, which was derived
from Finnish shipping data [25] and usually is referred to as the “Holtrop
equation”. The latter approach yielded slightly (8-16%) higher estimates of
the surface area for corresponding length classes compared to the Mam-Pec
model
D
)]
0.5
A
=
L
(2
D
+
W
)[
C
m
(0.53 + 0.63
C
b
-0.36(
C
m
- 0.5) - 0.0013(
L
/
(2)
In which:
A
= submersed ship area,
L
=lengthofship,
D
=depth,
W
=width,
C
M
= empirical factor (ranging from 0.95-0.98, taken in the ESD taken as
0.975) on how full-bodied the main arch of the ship is, and
C
B
= empirical
factor (ranging from 0.75-0.85, taken in the ESD as 0.8) on how full-bodied
the underwater volume of the ship is. The factors
C
M
and
C
B
are calculated
according to the formulas:
C
M
=
A
M
/
(
BD
)
(3)
C
B
=
V
d
/
(
LBD
)
(4)
In which:
A
M
is the area of the main arc of the ship, i.e. the area of the biggest
cross-section of the ship, which is in general in the middle of the ship, and
V
d
is the underwater volume of the ship (displacement).
On the basis of a statistical survey of paint-usage data in relation to ship
dimensions (DWT) from a large supplier for 300 ships and covering 9 of the
25 main Lloyds shipping categories, Van Hattum et al. [5] concluded that
predicting submersed surfaces with simple generic regression formulas may
result in deviations up to several 100% below or above actual measured sur-
face areas. As it is evident that the submersed surface estimation introduces
a large uncertainty in the emission estimation, it is recommended that in fu-
ture studies a more refined approach, based on statistical surveys is followed.
2.3
Shipping Intensity
Information on the shipping density, a third parameter in Eq. 1, can be ob-
tained from various sources, such as on-line port statistics from local port
authorities or branch organizations such as the International Association of
Ports and Harbours (IAPH), commercial suppliers (Lloyds Register Ltd), or
trade oriented studies [26]. Although traffic intensities and port arrivals are
monitored on a large scale in European waters, there still is no structured and
aggregated reporting system and especially estimations of traffic intensities
in open and coastal water may still have large uncertainties. Another prob-
lem is caused by the differences among harbors in reported dimensions and
shipping types, such as length, depth, dead-weight tonnage (DWT), gross ton-
nage (GRT
NT), compensated tonnage (CGT), cargo
landed, number of containers, or economic parameters, such as revenue tons.
/
GT), net tonnage (NRT
/
