Improving ship efficiency

Total ship efficiency

Improving total ship efficiency reduces lifecycle costs and emissions. By combining our knowledge of automation, machinery, propulsion and the control of them with an optimised ship design into a single integrated solution, a truly efficient ship operation can be achieved. From a long-term perspective, the potential for improving energy efficiency has been estimated to be 30-50%. This will be achieved by optimising component performance, ship design, waste heat recovery and the recovery of other losses, weather and voyage routing and by taking advantage of potential new technologies.
System integration enables further efficiency improvements, while customers benefit from having proven solutions from a single supplier. With lifecycle support, yards can better optimise their building schedules and owners get proven solutions that are easier to manage.

Engine efficiency improvements

The efficiency of Wärtsilä diesel and gas engines ranges between 42-52%, depending on the engine type. The peaking efficiency of 52% for the best engines is one of the highest efficiency ratings among existing prime movers. The improvement in efficiency is becoming more challenging as the emission requirements are getting increasingly stringent. Wärtsilä has several ongoing programmes targeting simultaneously to ensure the high efficiency of its engines, and to reduce engine emissions.

One key success factor in this field has been the development of integrated engine functionalities that enable low emissions and high engine efficiency. The air and fuel admissions are controlled by an automated system that provides optimal combustion under all operative conditions. Wärtsilä’s extensive experience in component design has led to the development of combustion chambers capable of withstanding higher cylinder pressures and temperatures. This contributes to engine efficiency directly and positively. The research and development of two-stage turbocharging is another important part of aiming to achieve our goals in environmentally sound solutions of engine fuel efficiency development. However, improving the efficiency of a single component does not necessarily guarantee the best overall outcome. In marine, more can be achieved through comprehensive ship design, system integration and machinery optimisation. Similarly, in power plant applications, by combining various technologies an overall efficiency rating of 90% is possible.

Heat recovery and energy conversion improvements

Utilisation of fuel energy can be further improved by using heat recovery concepts and secondary cycles. Steam-based combined cycles are applied widely in diesel engine applications and are expected to gain a foothold also in bigger gas engine plants. Further improvements can be expected by designing engines for secondary cycles.

Propeller efficiency upgrades

The propeller’s efficiency, amongst other parameters, is an important consideration for achieving economic sailing.

Fouling, surface roughening and leading edge damage to the propeller, when in service, can result in efficiency losses of 3-7%. Also, by replacing outdated existing propellers with new ones designed based on the latest knowledge, propeller designs and operating profile of the vessel, significant savings with short payback periods can be achieved.

For ships such as oil tankers and container vessels with annual fuel costs exceeding EUR 5 million, propulsion degradation can easily cost several hundred thousands of euros a year.

The results of ongoing projects investigating the efficiency loss of propellers in service will improve the performance based maintenance of a ship’s propeller and will thus increase the vessel’s overall efficiency throughout its lifecycle. Special attention is paid to the propeller- ship design integration, aiming at the optimization of the overall efficiency under real operational conditions. The new Wärtsilä OPTI propeller is very suitable on this respect. Wärtsilä provides several solutions such as EnergoproFin propeller cap with fins, Energopac rudders and HR nozzles that can also be retrofitted.