Fleet management, logistics and incentives
5.23 Reductions in scheduled speed (i.e., accepting longer
voyage periods) will enhance efficiency although it will result in more ships
being required. Nevertheless, there is a trade-off between freight rates and
fuel cost: with lower freight rates and higher fuel prices, it may be more
advantageous to reduce speed.
Generally speaking, efficiency improves when we concentrate
cargoes in larger ships as much as possible. Obviously, larger ships that are
not fully loaded are not efficient when they do sail. Smaller ships, on the
other hand, end up having higher net
energy efficiency for being able to fill
their cargo hold to capacity and having access to more ports and cargo types,
[7].
Voyage optimization
5.29 Voyage optimization can be achieved by:
.1 choosing optimal routes to avoid adverse weather and
current conditions will minimize energy consumption (weather routeing);
.3 ballast optimization – preventing unnecessary ballast
use. Attaining optimal ballast may sometimes be difficult since it also affects
the safety and comfort of the crew; and
.4 trim optimization – determining and operating at the
proper trim.
5.31 Weather routeing can bring substantial savings for
ships on particular navigational courses. Certain types of weather routeing
systems, performance monitoring systems and technical support systems and other
procedures can be used to help attain optimal voyage performance.
Energy management
There are certain cargoes, such as special crude oils,
bitumen, heavy fuel oils, etc., that need heating.
The heat required may partly be provided by producing steam
or using exhaust heat. However, in many instances an extra steam boiler is
required to supply enough steam. Steam from exhaust gas is usually sufficient
to heat the heavy fuel oil used on most vessels; in port, however, steam from
an auxiliary boiler may be required.
5.35 It is often feasible to decrease energy use on board by
achieving more conscious and optimal operation of ship systems. Examples of
measures to under taken include:
.1 avoiding unnecessary use of energy;
.2 avoiding parallel running of electrical generators;
.3 optimizing steam plants (tankers);
.4 optimizing the fuel clarifier/separator;
.5 optimizing HVAC operation on board;
.6 cleaning heat exchangers and the economiser; and
.7 detecting and repairing leakages in boilers and
compressed-air systems, etc.
A lot of savings may be achieved by upgrading automation and
process control, for example, automatic temperature control, flow control
(automatic speed control of pumps and fans) and automatic lights. The potential
for attaining energy-savings using energy-management measures is hard to
determine, since that depends on the ship’s previous operational efficiency and
on the contribution of auxiliary power use in the overall energy scheme. A 10%
savings on auxiliary power may be a practical target for many vessels. This
amounts to about 1 to 2% of the total fuel consumption, depending on actual
conditions.
5.37 Optimal maintenance and tuning up of main engines.
5.38 Maintaining a clean hull and propeller is vital in
achieving fuel efficiency.
Selecting more effective hull coatings.
16. Reducing navigational for ships is often seen as a
“quick win” in terms of reducing carbon emissions from vessels.
Recent studies reveal that many abatement technologies are
available, and cost-effective, such as:
- Slide
valves reduce NO2 on slow-speed engines by 20%, very inexpensive, fit easily
and are cost-effective.
- In-engine
controls could reduce new engine NO2 by 30%.
- Selective
Catalytic Reduction cuts NO2 by 90%.
- Water
Injection/Humid Air Motor cuts NO2 by 50%/75%.
- Scrubbing
by sea-water cuts SO2 by 75%.