Friday, July 5, 2013

Energy savings by operations

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%.

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