Sustainable Ship Technology

Modern shipyard aerial view and communication network concept. Logistics. INDUSTRY 4.0. Factory automation.

By Eggo Bracker, Madelaine Engelbrecht, Florian Meier, Michael Palocz-Andresen and Paul Pozzi

Some 90 percent of world trade takes place by sea. Due to the operation of ships that burn heavy fuel oil, which contains significantly more sulphur and other pollutants than other fuels, the ships emit gases, pollute the air and influence the climate1. This paper illustrates possible new shipping propulsion systems and presents alternative versions of future shipping. Figure 1 overviews the structure of the report.

figure 1


Merchant ships using heavy fuel oil (HFO) and marine diesel oil (MDO) are responsible for about 3 per cent of global CO2 emissions. In 2015, these emissions amounted to about 932 million tons. For comparison, the emissions from Germany in 2017 totalled 905 million tons. In the exhaust gases of these ships are numerous substances that affect the environment, health, and climate. In particular, HFO exhaust gases contain sulphur oxide, particulate matter, including soot particles, nitrogen oxides, and heavy metals, in addition to CO2, contributing to acidification and eutrophication of the ocean2.

In the future, due to the acidification of the oceans, the pH of the water will decrease. The falling pH of the water will change the living conditions of a range of marine life3. This change could have a major impact on the biodiversity of the world’s oceans. Sulphur emission control areas (SECA) have been established to reduce and control the impact of sulphur. Within these areas, emissions are limited to 0.10 per cent; outside them, up to 0.50 per cent. For comparison, the limit allowed in fuel for road transport in the EU is 0.001 per cent2. Figure 2 presents the main sources of pollution due to ships.

Figure 2

Modern vessels run on LNG or LPG (liquefied natural / petroleum gas). Merchant and cruise liner vessels running on LNG have become more and more popular. LNG owes this success to several reasons. For example, it contains very little sulphur. These ships also emit a much lower quantity of nitrogen oxides while the engines are running. However, in some lean gas-air mixtures, the low emission of nitrogen oxides turns into the disadvantage that some unburned methane is emitted.

The number of LNG-fuelled ships will increase in the coming years. In the first step, the sulphur emission control areas mentioned above are another reason why ships with LNG will be more common in the future, especially within these areas4. LNG/LPG have great potential to reduce emissions that are harmful to health, the climate, and the environment. They emit hardly any sulphur oxide, particulate matter, or heavy metals5. However, there are also problems with LNG as a fuel, so that it could be only a first step towards zero carbon.

Risk of Methane Leakage

The risk associated with using an LNG-fuelled commercial vessel is methane slip. This ‘‘slip’’ refers to the leakage of methane during the production, delivery, storage and use of LNG as a result of careless and improper handling6. There are various marine engine technologies that can use LNG, including dual-fuel (LPDF) engines with low-pressure injection, four-stroke medium-speed engines and LPDF two-stroke, slow-speed engines.

This article does not discuss the exact technical background of each technology. This comparison only seeks to clarify to what extent and under which technologies methane slip occurs. The term refers to the fact that each of the engines mentioned above emits unburned methane. This methane is produced mainly by lean mixtures and incomplete combustion, and by fuel that collects in the combustion chamber during compression. Mixtures injected at low pressure have a significantly higher slip compared with high-pressure injection systems. The following table illustrates this once again, showing the slip associated with the various engine types4.

Table 1

All these points, the emissions as well as methane slip and much more, need to be included in research into new propulsion technologies and are already being taken into account in existing projects to make shipping more sustainable and environmentally friendly. One of these research areas deals with ship propulsion by solar energy.

Prospective Solar Energy

Solar power is characterised as theoretically serving as an infinite source of energy, especially when the sun is shining bright. Solar energy has the great advantage of causing extremely low noise and exhaust emissions during usage and it is emission-free when used optimally and to the highest technological standards. Solar energy has relatively low maintenance requirements, which keeps costs lower in the long term than other technologies6.

Possible Barriers to Solar Energy

Solar technology, especially in shipping, has disadvantages that should not be underestimated. One of the biggest problems of solar technology is the initial costs, which are very high in two regards. First, if solar energy is to meet the huge demand for electricity, it needs a lot of space, hence a lot of high-quality solar panels. This is expensive. Second, there is the simple fact that no electricity can be generated if there is no sunshine6. This means that, in the end, a proven energy source must be used in a complementary manner to guarantee an energy supply 24/7.

Open Questions

How far solar power can be used to make trade shipping more sustainable has been the subject of research for some time7. The research is particularly concerned with the question of space for the possible installation of solar panels on a vessel, possible costs, actual energy balances and the technical lifetime of the complex technology. All this in the context of the strongest weather conditions or influences of nature.

One of the main ideas currently is to use solar energy in addition to another source of energy, to avoid total dependence on only one. But how exactly could solar electrical energy be generated on a merchant ship?

The Use of Solar Energy in Trade Shipping

One popular idea here is to have many solar panels installed in a large scale on the deck of the ship, taking the energy harvesting potential to the limit. Any free area could or should be used. An example was the first solar hybrid ship, in 2008, with 328 solar panels on the deck, but they were able to generate only a small amount of energy (up to 40 kWh)8. A success, but not an alternative to existing propulsion technologies capable of shipping several thousand tons of goods around the world in a relatively short time.

In the years that followed, research in the field of solar energy related to shipping grew and engineers continued to use the idea of large-scale panel installations on the deck (with the goods being carried inside the vessel) and further developed the panels in their technical capabilities in order to make them usable for higher energy production.

The Combination of Solar and Wind Energy

One logical option is the idea of having many wind-mobile solar panels standing upright like sails on the deck of the ship, which can use both sun and wind, storing the energy in batteries (“fast chargers”9). This arrangement can provide energy when weather conditions prevent a full power supply10. An example of what such a ship might look like is shown in Fig. 3.

Fig. 3

The challenge is to develop sustainable batteries with simultaneous high storage capability. The idea is made more feasible by an IT algorithm that permanently extrapolates the energy yield of the solar panels and the sail alignment and releases possible additional energy sources11.

Wind Energy

Using wind energy in merchant shipping has a few advantages over conventional ship propulsion. Energy generated from wind is inexhaustible compared to fossil resources, such as oil. In addition, the exclusive use of wind energy does not produce any emissions. However, an engine must be available on wind-powered vessels for calm conditions and to navigate in a harbour. Mankind has thousands of years of experience in sailing, which can be used for the development of wind-driven ships. Another advantage of wind energy is the cost savings. Wind is freely available and very little money needs to be spent on further fuel for harbour navigation12. Many of these benefits also reduce the impact on nature. In particular, the reduced emissions from lower fuel usage contribute to a gentler form of merchant shipping.

Despite these advantages, wind energy has received barely any attention in the shipping industry in recent decades. Hence, when we think of wind power in shipping, images of old sailing ships come immediately to mind.

But the effective use of wind could look completely different, so, in 2020, a whole new type of sailing ship was proposed. Their sails are more like aeroplane wings and are about 80 metres high. It is possibly the tallest ship in the world, with a height of around 105 meters above the waterline. But, due to the telescopic construction of the wing-sails, they can be retracted to a height of approximately 45 meters above the waterline. This is necessary in order to pass under bridges or for stormy and windy areas, to reduce the resultant forces. Although a motor would be used to reach ports and to move forward in calm conditions, 90 per cent of the emissions of normal ships could be saved.

The recently presented ship was designed for a capacity of about 7,000 cars. Compared to actual container vessels, it has a low capacity and would need to be upscaled13. What such ships may look like is shown in figure 4. If this type of ship is brought to reality, it will make shipping much more environmentally friendly.

figure 4

Simply Retrofitting Conventional Ships

Another simple way to use wind energy in conventional shipping is with so-called kites. This is an innovative wing using the forces of wind energy so as to be capable of towing commercial vessels. The kites reach a flying altitude of 200 to 300 metres, with the position, height, and speed of the kite being automatically controlled so as to give the vessel the best thrust in every situation. It uses wind as a free energy source, which allows it to reduce the power requirements of the main engines. The kite can achieve a 20 per cent improvement in fuel consumption and significantly reduce pollutant emissions.

Installation is possible as an addition on any vessel. The simple, modular design allows an installation within the time frame of a regular port call. The kites have gone through a strong safety process for being flown, deployed, operated and retracted completely automatically. In addition, the kites analyse a wealth of complex data in real time and autonomously adapt to prevailing conditions to optimise the vessel’s performance, while ensuring maximum safety. Safety on board is ensured by secured take-off and landing software14. Due to the easy and quick implementation on any vessel, as many vessels as possible should be retrofitted with a kite if there are no (additional) alternatives to conventional HFO-burning vessels. (See figure 5.)

figure 5

Hydrogen Energy

The advantage of hydrogen-powered vessels is that they can be operated with no emissions. These vessels emit only water vapour. However, it is important to note that not all hydrogen production is completely emission-free. Wind energy plays an important role in the production of sustainable hydrogen. Green electricity powers electrolysis and produces hydrogen, which is then stored and used as fuel in the ship, as shown schematically in figure 6. There are different methods for using hydrogen.

figure 6

Currently, the best solution for hydrogen-powered ocean-going vessels is a combination of green hydrogen generated from wind energy supplying fuel cells and buffer batteries. This solution is already used in short-distance sea shipping. Today’s container ships theoretically offer the space needed to install such a combination in their hulls, as shown in figure 7.

The problem is not space, but power. Large ships can generate their auxiliary power requirements via the fuel cells15, but, with the solution described above, it should be possible to control the entire propulsion system in the future. The next step to ensure this is to build fuel cell power plants for ships. These power plants would have to generate high power in the megawatt range. As a comparison, the vessel MSC Gülsün’s combustion engine has an output of 75 MW, which is 101,972 hp. Currently, fuel cell stack outputs of about 3 MW are being discussed16.

figure 7

Production of Synthetic Methanol from Hydrogen

A completely new idea that should be considered in mobility in connection with hydrogen is synthetically produced methanol. This offers advantages over pure hydrogen as an energy source. The disadvantages can be summarised in that hydrogen-powered ships still have the problem that not enough energy can be generated on board to fully supply today’s container ships. An interesting option would be methanol produced by electrolysis, which has much more energy density than hydrogen alone. Gas power is a well known configuration in ships today, and the engine technology just needs a little adaptation and implementation.

Furthermore, synthetic methanol can be produced from green hydrogen and CO2 captured from industry and green electricity. Each ton of methanol could yield 1.4 tons of CO2 reprocessed17 either from CO2 capture and separation from the exhaust gases, or filtered and enriched out of the ambient air.

Assessment of the Options

To provide an overview, table 2 compares all four propulsion systems, evaluated based on emissions, costs, implementation, state of research and the capacities of the ships.

table 2

Summary of the Current Situation

The present situation of merchant shipping is characterised by its use of fossil fuels. These fuels have an enormous impact on the environment, climate, and people. It is not only the CO2 emissions that make these ships unsustainable. There are also many other substances in the exhaust gases. This leads to acidification of the oceans and a reduction in the diversity of species. The decreasing pH value of the water will sooner or later change the living conditions of many aquatic life forms.

Ships powered by LNG are also enjoying enormous popularity for this very reason. Ships that run on it emit only small amounts of sulphur and nitrogen oxides. It is precisely because of the introduction of sulphur control areas that LNG is becoming popular as a fuel. LNG will help to reduce the impact on health and the climate, and cut environmentally harmful emissions. But there is another major factor in play: methane.

Outlook for the Three Options for More Sustainable Commercial Shipping

As we have mentioned, the sun is an infinite source of energy. It has low noise and exhaust emissions, as well as low maintenance requirements. The biggest challenges at present are the high initial costs and sensitive technology and the question of energy generation when there is no sunshine.

One possible solution that we have pointed out was that solar panels can also act as wind sails, combining wind and solar energy. An energy mix with traditional energy resources should not be ruled out here.

Hydrogen-powered ships are emission-free, due to the use of green hydrogen, since the only thing this waterborne transport would emit would be water vapour. In the context of large container ships, hydrogen poses a problem. The systems with fuel cells and buffer batteries planned for this purpose do not provide enough energy to operate them permanently, similarly to solar and wind energy. Now, fuel cell stacks of about 3 MW of power are being discussed, which would be just enough to meet the vessels’ auxiliary power requirements. The largest container ships have an output of 75 MW. Research in this area will show whether hydrogen will eventually become a real alternative for commercial shipping. Here, too, mixed technology with other energy sources cannot be ruled out entirely.

In conclusion, the most promising solution could be a combination of solar and wind energy to increase the effectiveness of the options, since it is already possible to equip large commercial vessels with these technologies. This makes it possible to reduce emissions that are harmful to the environment and the climate. The future will show which of the presented technologies will have the greatest impact on merchant shipping, if, indeed, it will be any of them.

The situation needs a change of direction. The ever-larger and more powerful engines currently in use have a strong impact on life as we will live it in the future. The increasingly depleted resources of fuel are factors that can be counteracted by a rethinking of the
drive technologies.


The authors would like to thank Prof. Maik Adomßent for years of support for the above seminar series in the complementary studies at the Leuphana University Lüneburg, Germany.

This article was originally published in The European Financial Review 22 April 2022. It can be accessed here:

About the Authors

Eggo Bracker

Eggo Bracker studied material sciences and mechatronics, working with marine research institutes and expeditions on research vessels alongside his studies. He worked as a graduate engineer in R&D departments of different companies in the machinery, aviation, defence and ship automation sectors for several years, followed by a decade of technical sales and project management in ship automation / data recording in supplying Asian shipyards. Since 2018, he works for Thales Naval and, since 2013, he has been an interdisciplinary guest lecturer for Leuphana University.

Madelaine Engelbrecht

Madelaine Engelbrecht completed an apprenticeship as a hearing care professional. She also earned her master’s degree in hearing care in 2013 and worked as a speciality store manager for five years before beginning graduate studies at Leuphana University in 2019. She is studying environmental science as a major, and political science as a minor.

Florian Meier

Florian Meier completed an apprenticeship as an optician and gained some practical experience in business, crafts and sales, before starting his studies in industrial engineering. During his studies he participated in a study of the state of Lower Saxony, which was dedicated to the healthy development of parks and gardens. This study was successfully completed with the LandPark Lauenbrück.

Michael Palocz-Andresen

Michael Palocz-Andresen has been working as a full professor for Sustainable Mobility since 2018, supported by the DAAD at the TEC Insitituto Tecnológico y de Estudios Superiores in Mexico. He was a full professor at the University West Hungary until 2017. Currently, he is a guest professor at the TU Budapest, the Leuphana University Lüneburg, and at the Shanghai Jiao Tong University. He is a Humboldt scientist and instructor of the SAE International in the USA.

Paul Pozzi

Paul Pozzi started his bachelor studies in political science as a major and philosophy as a minor at Leuphana University Lüneburg in 2019. He is a local politician for the Christian Democratic Union in Hamburg and for the Young Union Hamburg, where he sits on the Hamburg state executive board. In parallel, Pozzi works as a freelance public affairs assistant. Environmental issues, as well as safety issues, are the focus of his activities in both occupations.


The views expressed in this article are those of the authors and do not necessarily reflect the views or policies of The World Financial Review.