High-performance energy conversion is crucial

How is the Gotland Horizon project progressing?

The design of the Gotland Horizon is rooted in our desire to continue offering a short crossing time without impacting negatively on the environment. We need to ensure relatively high speed and clean fuel, with as little demand for energy as possible. Minimising the energy demand requires an energy-efficient design and high-performance energy conversion. To solve this, we are developing a low-energy hull, minimising weight, reviewing consumers of energy and making operation and flows more efficient throughout the vessel.

We’re in close dialogue with many different suppliers and developers of equipment for the Gotland Horizon. There are two key aspects that we’re focusing on in particular. One is that the gas turbines must be able to run on 100 per cent hydrogen, and we have made a great deal of progress in this area, with new advances coming all the time. The second aspect is about ensuring access to and the infrastructure for hydrogen, and here we have several ongoing projects, including one with Uppsala University to secure a hydrogen supply for the ferry service by 2030.

Why will the ship be powered by a gas turbine?

The choice of technology varies hugely depending on the mode of transport and the transport needs. Electric motors combined with fuel cells, traditional piston engines or turbines for gas and liquid fuel are some of the examples usually considered. Different companies find solutions that suit them best. Where you have short distances with low energy demand, batteries can be suitable if the electricity generation is clean, while in locations with no gas infrastructure, fuels in liquid form may be preferable. Hydrogen requires large volumes or extreme cold and is difficult to transport, so its suitability depends on having a supply near the consumer.

Gas turbines are often seen as energy-intensive but, combined with a steam turbine, we can achieve a level of energy conversion that is equal to or even higher than a diesel engine. A gas turbine supported by a steam turbine in a combined cycle therefore has many advantages for the Gotland service and similar shipping needs. Using this system, we can achieve the same speeds as today, while also running on 100 per cent fossil-free gas – something most other technical options can’t match.

In addition, the gas turbine creates a better working environment, with lower vibrations and less spillage compared to oil-based fuels in the engine room.

What do you mean by a combined cycle?

A combined cycle means that we combine the gas turbines with a steam turbine. The steam turbine recovers residual energy from the gas turbine and generates electricity that helps to propel the ship forward. Putting this power unit on the ship increases the energy conversion rate from around 30 per cent (gas turbine alone) to 50 per cent.

Will the ship run on 100 per cent hydrogen?

Naturally, the ambition is for the Gotland Horizon to run only on hydrogen, but this depends on whether we have a suitable supply. The considerable fuel flexibility that we’ve built into our design means that the ship can also run on other fuel types, and even a blend of different gases or fuels. Biogas and hydrogen could be a good combination, for example.

Are there any disadvantages or challenges regarding the choice of hydrogen?

There are currently no production facilities for the large-scale production of hydrogen, which begs the question – will we be able to supply the ship with hydrogen? However, many of the projects under way are looking to answer that. One of these, a project led by Uppsala University, is focusing on developing and assessing system solutions for the use of hydrogen – produced using fossil-free electricity via electrolysis – as a fuel in a large-scale system for the Gotland ferry service.

In addition to the actual production, the infrastructure for the large-scale handling of hydrogen also needs to be developed. Right now, no one is making some of the components required.

What is the best thing about the Gotland Horizon’s technology?

One of the best things about the way we’ve developed the Gotland Horizon is the incredible degree of fuel flexibility. There is still some uncertainty about the future of fuel supplies in different markets, so we need to be prepared for different alternatives and flexible about different solutions. The Gotland Horizon is designed for hydrogen but the multi-fuel system allows her to run on several different fuels, in both liquid and gas form. This future-proofs the ship and allows us to push towards the climate transition irrespective of availability on the fuel market.

What is the next step in the project?

As I say, the fuel infrastructure is a key issue that involves some crucial choices. Intensive work is under way to develop the underlying research and secure production, supply and the right infrastructure for the fuel.

Gotland Horizon’s tech in brief

1. The gas turbine is driven by hydrogen and has a mechanical drivetrain to the ship’s gearbox
2. The hot gas from the gas turbine is piped through a steam boiler to create steam in the funnel
3. The steam in turn drives a steam turbine that is connected to a generator to produce electricity
4. The electricity powers an electric motor that is connected to the same gear system that is driven by the gas turbine
5. This combination of the electrical and the mechanical creates a drivetrain that is both flexible and efficient