Wind and sun

Wind and sun:

Renewable energy sources

5.39 Renewable energy can be utilized directly on board ships (by using solar, wave and wind energy) or energy can be generated on-land and converted and stored in an energy carrier to produce energy, such as electricity from batteries.

Wind power, onboard use

5.40 Wind power can be harnessed in many ways and used as the motive power for ships, for example by:

.1 Conventional sails;

.2 Solid wing sails;

.3 Kites; and

.4 Flettner-type rotors.

5.41 These systems have varying properties. Wind conditions vary depending on location; hence, certain regions have greater potential for wind power use and as routes than others. This study showed that the potential for wind energy was better in the North Atlantic and North Pacific than in the South Pacific. Fuel reductions were slightly higher at faster speeds.

However, in terms of percentages, the fuel savings were higher at lower speeds, due to the reduced total demand for propulsion power. In percentage terms, savings were typically about 5% at 15 knots, increasing to about 20% at 10 knots.

5.42 Present-day exposure to these technologies on board large vessels is limited, and modelling data are, therefore, hard to confirm. However, wind-assisted energy appears to have good prospects for saving fuel in the short and long run.

5.4 Solar and wind energy could also add to reduced CO₂ emissions; but as a auxiliary source of energy rather than a single source. Propulsion using nuclear energy has been effectively operated in navy ships.

Solar power, onboard use

5.43 Present solar-cell technology is enough to address a mere portion of the auxiliary energy needs of a tanker, even though the whole deck space were installed with photovoltaic cells.

Obviously, during certain periods and in certain places, solar energy will be more than sufficient and the auxiliary power requirements could be supplied. Furthermore, since solar energy is not continuously available (e.g., at night), backup supply would be required. Hence, solar power seems to be of interest generally as a supplementary source of energy. With available technology, only a small percentage of savings on the total energy requirements can be realized, even with wide use of solar energy.

Moreover, currents price levels and efficiency put solar energy within the bottom end of the cost-effectiveness list [9].

Wave power, onboard use

5.44 This involves concepts for harnessing wave energy and/or vessel motion. For instance, gyro-based internal systems and wavefoils for external systems, stern flaps or relative motion between multiple hulled-vessels (such as trimarans) can augment a vessel’s power needs. These systems are highly complex and technical, not highly energy-efficient and are not considered potential sources of auxiliary energy.

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Energy saving by operations

Fleet management, logistics and incentives

5.22 Energy efficiency can be enhanced by utilizing the appropriate ships in a transport system.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].

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.

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%.

Reducing the emission of GHG (Engineering)

Reducing the emission of GHG (Engineering)

Depending on which organization we are talking about, there are varying technical and operational procedures required to reduce the emission of GHG. The International Council on Clean Transportation released a long list of recommendations that would reduce the GHG emission (Appendix I), while IMO through the Marine Environment Protection Committee (MEPC) identified different classifications for the same purpose.

On April 9, 2009, the MEPC released its second IMO GHG Study. In the study, MEPC identified four categories of options to reduce ships emissions, namely:

·         Improving energy efficiency, that is, burning less fuel to attain the same output by optimizing the design and operation.

·         Exploring renewable energy sources (sun and wind).

·         Using emission-reduction technologies (chemical conversion, capture and storage)

·         Using fuels that produce less emissions (natural gas and bio-fuels)

Improving energy efficiency through boiler design and operation

Optimizing ship design

The design technology is categorized as short to medium term; it has to be inputted during construction of new ships. However, some of these optimization steps can be applied to existing ships. Each new vessel’s design specifications, such as ship’s size and the targeted speed, are considered the main hurdle toward achieving the optimal energy efficiency for the ship. Furthermore, some ports and rivers may impose limitations on the ship’s draught which further reduces its efficiency.

Optimizing the hull and superstructure

Even if the ship’s hull and its superstructure may cause minimal resistance, there still exist areas for more optimization for attaining higher efficiency. Design optimization on the hull and superstructure minimizes air resistance and drifting, especially for large container ships which have huge superstructures. The latest technology to reduce the hull’s frictional surface resistance is through the use of the air-bubble system which involves blowing air bubbles underneath the ship’s hull, thus improving fuel-use efficiency.

Optimizing the Power systems

This technology requires recycling the energy from the exhaust system through the use of power turbines. This energy can be utilized to drive a motor to generate electricity and also to support the main engine. The recovered energy can augment 10% to the total power. Likewise, Diesel-electric propulsion systems allow design flexibility that will result in energy saving.

Optimizing the propulsion systems

Increase in the propulsion power by using propeller vanes, contra-rotating propellers and ducts can significantly improve the energy efficiency. In like manner, using high-efficiency and asymmetric rudders can help optimize propulsion.

Operational efficiencies

Operational improvements, such as enhanced weather routing, optimized trim and ballasting, better main and auxiliary engine maintenance and tuning, hull and propeller cleaning, speeding up ship unloading and slower steaming, can significantly affect the ship’s emissions. The IMO has estimated that a speed reduction of merely 10% across the global fleet by 2010 would result in more than 23% decrease in emissions.