More and more hybrid applications are introduced in the maritime industry. The reason for the invasion of the hybrids is the drop of the batteries prices. Not only the price has been dropped but also weight and volume has been reduced significantly, and this is something that will continue in the future as the technology evolves.

But, it is not only the energy storage prices; there are also other things that have been improved over the years, like the weight and the volume.

So, what is a hybrid system? A hybrid system is a combination of engines, batteries, power drives, alternative power sources like fuel cells, for example, and everything is managed by the EMS, which is the Energy Management System.

Most people, when they say hybrid system, they think of a system that can switch from engine to battery, and relate it with the zero-emission concept, which is perfectly okay, this is quite true. But, this is not only that.

With the zero emission concept, you can work the engine or the battery, so you can switch of the engine and work your propulsion plan with the battery and enter in a sensitive area, so you have zero emission.

But, what about working your battery in parallel with your engine and see what improvement we can have.

In Wartsila we believe that there are a lot of functionalities that a hybrid system can have. I will focus on two functionalities, which are less OPEX and better efficiency.

How we design a hybrid system

We like to be as much as realistic, as possible. In order to design a hybrid system, we take raw data from the vessel and then through machine learning and simulation tools, we define an integrated solution upon the customer’s needs.

Let me present you two real case studies.

Case study 1

Concerning an LNG carrier with mechanical propulsion. It has 2x2 stroke engines and 2x FOO propellers and also has 4 auxiliary engines for the electrical propulsion.

This study can be applied to any common vessel like VLCC, bulk carrier or container vessel, because as mentioned above it’s about a mechanical propulsion system.

What we did is to monitor the vessel’s route and record all the load, every time the load of the propulsion engines and the auxiliary generators. And it took us about six months to record all these data, speaking about 16 million data.

So, we create the operating profile. On the graph below, the blue line is the propulsion load and the orange one is the hotel load.

Of course we focus on the auxiliary engine operations.

We distinguish four different phases:

  1. Sailing ballast
  2. Sailing laden
  3. Discharging
  4. Loading

In that way you can see how the auxiliary engines are working and what is the load of each one.

Then, we try to change the conventional configuration. The conventional configuration is 2x2 engines and 4 auxiliary gensets.

So, we came up with the optimum configuration, which is to remove one auxiliary engine and replace it with a battery. And the battery’s size is about 1Mwh/hour.


We can work one auxiliary engine less. What we have seen is that in most cases we’re working with two engines, for example in the sailing, ballast phase, because of the fear that something is wrong with one engine and we didn’t want to overload one engine, for safety reasons.

But, by having a battery we can work only with one engine, in a better fuel efficiency area, in higher load, and having also a battery helping this load.

This is also happening in the sailing load phase and also in the unloading phase.

The good thing is that we eliminate the blackout fear. Having a battery all the time, even if we are having a total failure of one engine, we have the battery that takes care of all the load; there is no problem of having a black out.

Also, we have optimum efficiency of the engine because we are operating the auxiliary engine close to 80-90% of the load and in this way we have the better specific fuel oil consumption, because we are dealing with LNG engines.

Peak Shaving

Imagine that you have an engine and we have the load. The load is always fluctuating. Any fluctuation of the load is going to the engine. Now, if you have a combination of engine and battery, then the engine can work with steady load and all the fluctuation of the load can be absorbed from the battery.

This can give us a stable engine load and optimum fuel consumption.

The results showed that we can achieve the reduction of fuel consumption about 3.3% and the running hours can be reduced by 24%. The latter is very important because we are operating less engines.

If we add all these together, maintenance, LNG, lube oil, everything, this comes to a reduction of 4% for the opex.

In other words that means:

  • 600 tons/year LNG saving
  • 9000 rhs/year less
  • Less than 2 years payback

Case Study 2

This case study is about a vessel that has electrical propulsion. In this case we have an LNG carrier with 4 diesel engines that are working as generators.

We again recorded the vessel’s routes and came up with the operating profile.

As mentioned above, the current configuration is electrical propulsion with 4 engines, and we find that the optimum configuration could be to add 2 battery packs, each one with 1MW hour.


Following the same analysis with the first case study, we can achieve about 8% less OPEX

In other words:

  • 1700 tones/year LNG savings
  • 8200 rhs/year less
  • Less than 3 years payback

So, the hybrid feature overview is not only saving OPEX, but many other things, such as:

  • Stable engine lead
  • Increased safety
  • Instant response
  • Load ramp management
  • Optimum fuel consumption
  • Less running hours
  • Reduced maintenance
  • Reduced emissions

This is an edited vesrion of Mr. Giannis Moraitaki's presentation during the GREEN4SEA Forum Athens 2020.

You may view his presentation herebelow


The views expressed in this article are solely those of the author and do not necessarily represent those of SAFETY4SEA and are for information sharing and discussion purposes only.

Giannis MoraitakisSenior Business and Sales Development Manager, Wärtsilä

Giannis Moraitakis has studied Marine Engineering in the Hellenic Naval Academy. He continued his studies in the National Technical University of Athens in the School of Electrical Engineering & Computer science and later he received his master’s degree in Electrical Engineering from the Naval Postgraduate School of USA. He has served for 29 years as an officer in the Hellenic Navy, in various positions onboard ships and later in shore assignments as an engineer and electronic officer.  In 2014, he ended his career in the Navy with the rank of Commodore and worked as a technical manager in the NEARCHOS ship-management company. He joined Wartsila in 2018 in the position of Senior Business and Sales Development Manager.