Trans RINA, Vol 156, Part B2, Intl J Small Craft Tech, Jul-Dec 2014 t has a 121 distribution where µ is the unknown true tt n
mean vessel efficiency. We reject 0
deviation 0203. n 1,
H if t 1.721.
Using the data, we obtained the sample s
Since tt , we can reject 0 1.102,1.278 . standard , and the test statistic t = 4.46. H . Therefore the sample
mean will be greater than 1.0 kg/L. The possible range of sample mean is
Since the sample mean is within the confidence interval, the estimated total fuel use of long-line vessels was then calculated to be approximately 0.75 ML.
The upper and lower values of the confidence interval are used to calculate the estimated total fuel consumption for long-line vessels as summarised in Table 8.
Table 8: Estimated Fuel Use By SESSF Long-line Fleet Confidence Interval
Vessel
Efficiency (kg/L)
Lower Value 1.102 Upper Value 1.278
Estimated Fleet Fuel Use (ML)
0.81 0.70
From the data gathered from the operator questionnaire, the time and engine load for each vessel operation was determined and compiled as shown in Table 9.
From Table 9, we can see that the setting and retrieval of the fishing gear takes up a large portion of the time
during a fishing trip for a scalefish vessel, as opposed to being on anchor or mooring as is the case with a rock- lobster vessel. This is because the vessels use different fishing methods, such as trawling or automated long- lining, and they also land much more catch due to the lower value per kg of the catch landed. To further investigate the best
options for reducing diesel
consumption of these vessels, an energy breakdown of the systems aboard each vessel was investigated as shown in Figure 7 and Figure 8 respectively.
From Figure 7 and Figure 8, we can again see that a majority of the energy used goes to powering the prime mover to propel the vessel. However, in comparison to a southern rock-lobster vessel, there are larger auxiliary engine loads due to running larger refrigeration systems, ice makers and fishing-gear systems, such as warp winches and net drums.
5.
ENERGY EFFICIENCY IMPROVEMENT OPTIONS
From the energy breakdowns of the southern rock-lobster and SESSF vessels, the main sources of energy losses identified in the surveyed vessels are:
heat losses from prime mover and auxiliary engines;
propeller efficiency losses; additional appendage drag due to poorly aligned bilge keels and keel cooling units; and additional drag due to flat-plate rudders.
Table 9: Scalefish Vessel Typical Engine Loads during Different Vessel Operations Vessel Operation
Steaming to fishing grounds Setting of fishing gear Retrieval of fishing gear
Steaming between fishing locations
Vessel at anchor or Mooring
Time Spent (hrs)
10-24 3
10 2-3
Speed (knots)
7-9 6
0-3 7-9
Froude Number (on LWL)
Propulsion Engine Loads (% of Max RPM)
0.29-0.31 75-80 0.25
0-0.13 0.29-0.31
50-60 50-60 75-80
Rarely occurs 0 0 0
Auxiliary Engine Loads (% of Max RPM)
0-50
50-70 50-70 50-70 0-10
Estimated Fuel use (L/h)
20-50 20-40 20-40 20-50 3-15
©2014: The Royal Institution of Naval Architects
B-63
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