PTO / PTI - Hybrid propulsion system

Normally – in case of propulsion - hybrid is considered a merge of electrical and mechanical source of rotating energy. In case of power production, it is a merge of different types of power sources.

Hybrid propulsion system provides a very good basis for operating ship at optimum performance. This needs to be carefully designed to match the required operational profile. It is also good to understand real requirements correctly:

  • When defining the operational profile, is the definition based on the need or based on the existing technical systems capabilities in retrofit projects?
  • How to treat mode transfer situations during the operation? Maybe definition of current operations is based on the operational limitations that are currently existing rather than on actual needs.


For electrical system provider, like ABB Marine, understanding the word “Hybrid” correctly is a vital input. As with ABB’s multiple options to choose from, the operator may have more limited expectations regarding the same word. Therefore, patient design evaluation on the concept selection is recommended at very early stage. Especially the ratio of

Electrical power available  ⁄

                        mechanical power installed

is crucial for the success of the vessel concept. In case electrical power is available only in certain conditions or in case it is limited below commonly used operational situations, the hybrid concept may fail from its targets.


Balancing according to operational profile is important design step:

  • Increasing the electrical power component improves the operational flexibility of whole concept.
  • Reducing the mechanical power component too much, may reduce the benefits of direct power transfer to propeller.
  • There are no ready-made answers of what the correct ratio is. This needs to be evaluated case-by-case.



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