Future-proofing fleets with alternative propulsion and energy sources

Achieving sustainable transportation is one of the major pillars of the global energy transition. For maritime stakeholders, this means finding ways to limit ships’ carbon footprints, which currently account for 2.7% of global emissions^[1].

Ship owners in particular have an opportunity to future-proof their vessels by choosing the greener, cleaner, decarbonized technologies that can steer them to a zero-emissions future.

While clean fuels remain the centerpiece of many ship owners’ plans, alternative propulsion is a growing solution with long-term benefits. By replacing conventional propulsion with inherently carbon-free energy sources – such as wind, solar, nuclear and hydrogen – vessels can avoid or greatly reduce emissions throughout their lifecycle.

Testing wind-assisted propulsion

Shipping is heading back towards its roots with the rise of wind-assisted propulsion. Distinctly different from mechanical propulsion, wind-assisted technology comes in the form of rotating sails, kite sails and rigid sails installed onboard. While these are primarily used for large yachts today, marine stakeholders are looking to expand the application of sails to cargo and containerships in the near future.

For the moment, ships using sails for propulsion face two key challenges. The first is technical, as ships need to be fitted with weather routing technology that enables the vessel to change direction along with the wind. The second is regulatory: the International Maritime Organization (IMO) lacks rules and guidance for sail-assisted ships, and has yet to provide clear calculation and verification methods for assessing carbon reduction for the Energy Efficiency Design Index (EEDI).

Finding potential in hydrogen fuels cells

Fuel cells are another option being developed for alternative propulsion, with pilot projects being launched for large passenger ships.

Fuel cells are electrochemical cells that convert energy – from hydrogen or other hydrogen-carrier fuels – into electricity, enabling ships to run on electrical power without emitting harmful emissions or particulates. Other fuel cell types use diesel, methanol and methane directly as fuel, though this does not limit emissions to the same extent.

While this is an attractive option for ship owners, fuel cells are still in the early stages of being adapted for marine use and present several challenges. It is expensive both to outfit a ship with hydrogen fuel cells and to retrofit vessels that do not already use electric propulsion (e.g., containerships).

Hydrogen also presents safety and storage concerns: the flammable substance may be stored cryogenically, under high pressure or using alternative chemical storage techniques. Additionally, fuel cells have yet to be evaluated in the long-term, calling into question their reliability and ability to withstand sea conditions.

Surprising solutions: solar and nuclear

Solar power has long been a favorite solution for land-based projects, and the marine industry has taken notice of this carbon-free technology. Solar panels – which are cheap to produce and easy to install – are now being fitted onboard vessels, enabling ships to run on solar energy.

At this stage, however, there are some drawbacks, most notably around efficiency. Ships that run on solar energy have yet to achieve speeds beyond 5 knots, and vessels must have a secondary energy source available outside of daylight hours. While solar energy may be a workable solution for smaller and inland vessels, it will likely need to be combined with other onboard technologies for use on larger vessels.

Nuclear energy, meanwhile, is another lesser-known possibility for alternative propulsion, one that has already been used for naval and cargo ships. By placing a small nuclear reactor onboard, ships can run on electricity produced by the turbines, offering a carbon-free energy source.

While this is a strong solution from a sustainability perspective, nuclear-powered vessels come with many challenges. First, building and installing a reactor onboard is costly, requiring high CAPEX investments. Second, safety is a key concern for crewmembers, who need specific training to handle everyday operations. Finally, the uranium powering the reactor must be replaced every five years, making it a high-maintenance energy source.

To 2030 and beyond

When it comes to the energy transition, ship owners, operators and managers are doing more than looking for a solution – they want the solution. Marine stakeholders are thinking long-term, and the next big investment many will make in their fleets is meant to carry them to 2030 and beyond.

Bureau Veritas helps clients find the right alternative propulsion solution – the greenest, simplest, or most efficient – for their vessels. We have developed guidelines for fuel cell systems onboard commercial ships and are providing regulatory expertise and design assessment for the PacBoat project. Our experts are also participating in the development of several ships with sails, including the Ville de Bordeaux and the upcoming Canopée project.