The shipping industry is transitioning towards reduced emissions and improved energy efficiency. Whether integrated in a novel design, or retrofitted, a solution supporting the transition should be the best compromise between operational needs, forming a good balance between cost and benefit.
Available energy sources and technologies represent challenges and opportunities for the ship owning companies. Ulstein operates in several aspects in reducing the carbon footprint of vessels.
Our multidisciplinary concept design teams are capable of in-depth studies to explore, develop and define systems and technical solutions on board vessels.
Typically, our concept design teams include the design disciplines naval architect, hydro dynamist, stability engineer, electro designer, machinery (marine systems) designer and structural designer, as well as mission equipment vendors and owner’s and mission process operator’s representatives. Organised this way, we are enabled to discuss not only the technical solutions, but also how to meet performance and safety objectives for the ship operations.
For energy utilisation, we look at efficient hull and propulsion systems.
A fuel-efficient hull should be a proper baseline for efficiency. It must be optimised for the customer’s requirements by in-house CFD analysis and verified by model tank tests. We collaborate with suppliers with regards to flow aligned appendage design, wake adapted propulsion and model test facilities.
Ulstein hybrid propulsion concept
The «Ulstein hybrid propulsion concept», nominated for the Green Ship Technology Award, combines higher efficiency and better performance at high loads and excellent fuel consumption at low loads. Hybrid propulsion is therefore the perfect match for the operational profile of AHTS vessels like the Olympic Zeus and the Olympic Hera. The concept combines the best properties of both DE (diesel electric) and DM (diesel mechanic) into one system. This includes DM attributes of higher efficiency and better performance at high loads, along with the DE trait of excellent fuel consumption at low loads. The system takes up less space and is less expensive than a large diesel-electric system.
"After a number of jobs, we've proven to the market that we in average can run the ship on 70% of the fuel of what a conventional diesel anchor handler can, and that we can save up to 70% in some modes compared to a conventional ship", says Olympic Subsea chief technical officer Runar Stave.
Direct drive electric propulsion
A direct drive electric propulsion will eliminate the need for a gearbox and will reduce mechanical losses, leading to a reduction of fuel and CO2 emissions.
Further improvement is possible by use of permanent magnet propulsion motor, which leads to increased power density, no copper losses in rotor, improved energy efficiency and a major annual reduction of fuel and CO2 emissions. It causes low noise levels and load/rpm.
Additionally, the choice of a rudder bulb system will lead to improved propulsive efficiency and manoeuvrability, and a large annual reduction of fuel consumption and emissions. There is also a potential reduction in required brake power.
For energy recovery, we primarily study the balance between available excess of and demand for thermal energy. This balance is varying over time. To harvest the excess energy and make it available where the demand is, it is necessary to engineer functionality into an energy recovery system.
An example of a waste energy power generation of 150 kW will lead to a fuel reduction of approx. 290 tonnes and approx. 930 tonnes CO2.
Ship auxiliary systems
Auxiliary systems count in energy efficiency.
One example is chilled water compressors, where centrifugal compressors with variable rpm can lead to an improvement of COP (Coefficient Of Power) by approx. 80% at part load.
Also, evaporators, which use recovered heat as energy source, can produce fresh water as well as re-using water for technical purposes.
Rack cooling systems can be combined with variable speed pumps and a chilled water coil in rack cooling systems directly cooled by sea water.
As for frequency converters, the variable speed electric motors are used to match variations in load demand on main propulsion and thrusters, seawater cooling pumps, engine room fans, central and local AC units.
An extensive use of LED lighting, used in floodlights and in general lighting in accommodation and the technical areas, can reduce fuel consumption and CO2 emissions.
An alternative energy source can be solar energy, which has a huge potential depending on available area or size of ship, as well as geographical location. Solar energy should preferably be combined with batteries.
Batteries - for peak shaving, spinning reserve and power regeneration
Often, batteries are implemented as part of a hybrid solution in an existing vessel. Battery systems can store recovered energy and solar energy. They can supply energy when peak loads occur in ship operations, otherwise being handled by the increased use of the diesel engines. Peak shaving means that an energy storage system supports fast load fluctuations on behalf of a large power generator set. Spinning reserve means that an energy storage system acts as a standby power and energy source, reducing the required minimum number of online power generator sets. Power regeneration, or energy recapture, can be gained for example from crane operations.
The time delay which occurs when starting up a diesel engine is diminished when using power from a battery pack. The battery charges when there is power available and is ready to deliver energy instantly whenever needed. The use of batteries leads to reduced fuel consumption and emissions, while reduced use of the engine leads to lowered maintenance and service costs.
The efficiency gain is depending on the system design. The planning of the system requires a thorough understanding of the vessel’s technical system and operational profile.
Ulstein carries out multiple studies, one of which is feasibility studies. A feasibility study provides the insight for selecting the best solution towards CAPEX, OPEX and environmental impact.
See example on how Ulstein carries out an energy storage feasibility study.
Ulstein can be your partner to reduce your vessels’ carbon footprint
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