The answer is usually yes, but there is no one size fits all. Because whether it is an inland vessel, passenger vessel, tugboat, dredger or yacht, every vessel and its use are different and that requires a tailor-made approach.
But to start at the beginning: How many modes of propulsion are out there? What are the advantages of hybrid or electric propulsion? What should you take into account with hybrid and electric sailing? And finally, what does the hybrid and electric future look like for your vessel and for the maritime sector in general?
In this article, we take a closer look at all these questions and sit down with the hybrid/electric specialist at Caterpillar Marine: Marinus Jansen, Global Marine Technology Steward.
How many modes of propulsion are out there?
There are 3 modes of propulsion:
- mechanical propulsion – the energy needed to propel the vessel is provided by a diesel engine
- electric propulsion – an electric motor, using energy stored in batteries and/or fuel cells, propels the vessel
- mechanical and electrical propulsion – hybrid: the required energy is obtained from several sources, which can be 1. and 2., but that is not always the case
In this article, we focus on hybrid and electric sailing, because this, together with alternative fuels, will be an important step in the maritime energy transition.
What are the advantages of electric propulsion?
When you accelerate with a diesel engine, the speed increases and the propeller maintains contact with the water, which both you and those around you will hear and feel. With electric propulsion, the noise levels are low and there are hardly any vibrations because you build up power without the engines’ combustion firing events radiating into engine rooms and firing forces being driven into the vessel structure.
If the electrical energy is obtained from sustainable sources such as wind or Solar energy, you are environmentally friendly on several fronts by sailing electrically. No fossil fuels are used, no exhaust fumes are emitted and nature is not disturbed.
In addition, an electric vessel is pleasant to steer. That is also important, because the greater the ease of use, the greater the chance of a large-scale adoption of hybrid/electric sailing.
What are the advantages of hybrid propulsion?
If you use the hybrid electrical and mechanical combination, you enjoy the advantages of electric propulsion at low power & peak power and the power density and endurance advantages of a diesel engine.
This way, hybrid sailing becomes more environmentally friendly if instead of diesel, an alternative fuel such as green methanol or biodiesel is used for the average and high load power demands. Biodiesel and renewable diesel are drop-in fuel solutions that can be used today with most Caterpillar engines.
Green methanol can safely reduce greenhouse gas emissions to zero, while at the same time reducing other emissions, such as particulate matter and soot. Caterpillar is therefore investing in methanol engine technology.
Green methanol still contains carbon, but by using renewable sources, you keep the total carbon cycle very short. You remove just as much CO2 from the air during production as is released during combustion. For every new fuel, you have to look at the entire “carbon” chain to determine whether its use contributes to the reduction of greenhouse gases.
When is hybrid and electric sailing especially interesting?
Marinus Jansen, Global Marine Technology Steward at Caterpillar: “The question you have to ask yourself is: how much energy do I use at what power. The greater the difference between the average and maximum power demand from your vessel, the more interesting hybrid or electric becomes. In that case, you can use the available energy in a smarter way.”
“For example, using the energy stored in batteries. You can adjust the electrical system in such a way that the starting point is the average instead of the maximum consumption. By optimising the average energy efficiency, you save energy and fuel costs and limit the emission of greenhouse gases. In addition, there are many operational advantages to be gained, such as low noise and (temporarily) emission-free sailing.”
“But, as mentioned before, there is no one size fits all. A customer-back approach is needed where we support our customers on their sustainability journey and explore what’s best for their vessel and everyday situation. But to give you an example anyway: for an inland vessel that only needs a lot of power for a very short time to manoeuvre on part of the sailing route, electric sailing is a realistic, reliable and workable option.”
What should you take into account with hybrid and electric sailing?
“Right now, the relatively limited amount of energy in batteries limits the range of full electric sailing,” Marinus Jansen explains. “True, you can influence the total energy consumption with your sailing behaviour. For example, if you don’t let the use of the throttle exceed 80%, it’ll only saves a few kilometres per hour, while you save quite a bit of energy.”
“In addition, the purchase of a hybrid/electric system for your vessel, including batteries and a charger, is more expensive,” Marinus continues. “However, this is offset by (much) lower energy costs for electricity. And limiting emissions is a factor that is rightly becoming increasingly important.”
“It’s about the right balance: the investment must be in proportion to the savings. The extent to which this is the case depends on the type of vessel, how it’s used and what your objectives are regarding the energy transition and how much speed you want to achieve with it.”
An important question in this context is: what are the requirements stipulated by the industry for hybrid and electric technology?
Marinus Jansen: “For starters, fuel and energy consumption must be efficient and greenhouse gas and other emissions minimal. Hybrid and electrical systems must also be easy to install, maintain and use. Customers want the same ease of use and the support & service they have come to expect from Caterpillar and our dealers.”
“These new energy systems should last for many years and be supported by our dealers throughout the service life. This requires good control systems with increasingly better coordinated interaction between the different parts and components. After all, the customer needs a vessel that works for them and not the other way around.”
What does the future of hybrid and electric sailing look like?
“It is at least part of the sustainable future, as is apparent from everything we’ve discussed here, but also from the perspective of the Climate Agreement. How we have dealt with energy over the past century is simply not future proof. We have to (literally) change course.” Marinus mentions a number of aspects that are important for that future:
- Engine power
“Electric motors and propulsion engines can support and reinforce each other. For example, an electric motor generator in parallel with the motor can increase the speed more quickly. In the case of fully electric sailing, a generator set is still often installed, just to be on the safe side. It gives you peace and confidence, especially in unexpected situations or on a long voyage.”
- Communication is also a challenge
The energy transition is also a challenge in terms of communication. We use the same words, but mean something different. For example, an electrical engineer will interpret “load management” (regulating the demand for electrical power) differently than a mechanical engineer. These two different fields will grow closer and closer together, overlap and reinforce each other.”
Caterpillar has a long history of product innovation, emission reductions and adjusting its offerings to meet customer needs. “Our solutions help our customers meet their goals.” Also, when that means getting the electrical energy on the vessel using shoreside microgrid solutions to interface with new hybrid marine technologies. “Energy supply chains have to be developed, tested, accepted and implemented in a relatively short period of time.” Having the same company DNA and standards for machine reliability and product development, helps providing the same reliable products, service and support our customers are used to.
- Different mindset required
“In addition, the transition we’re going through also requires a different mindset. Always wanting to have a high power at your disposal is no longer necessary, because the digitisation in the maritime sector enables us to have a more precise look at how a vessel is deployed.”
Learning from other sectors
“We can learn a lot from electrical applications in other sectors. Examples include battery-powered mining vehicles, the new generation electric mini excavators and electrically powered wheel loaders, all of them by Caterpillar. Caterpillar has also supplied excellent hybrid applications for years now, such as the medium-sized dozer D6 XE and the hybrid excavator336F XE.”
The electric car industry is also developing rapidly. This sector also invests a lot in research into batteries with a shorter charging time and greater capacity.
These are mutually reinforcing processes, the user-friendly electrification of cars and industrial applications. The progress this yields is picked up for and by the maritime sector.
However, we should not think that all efficiency gains of hybrid and electric cars can also be realised in shipping. One example stems from the recovery of braking energy, something that is not possible in shipping at all. Hybrid technologies in marine applications must therefore yield efficiency improvements emissions reductions via intelligent use of onboard power and behavioral changes to vessel operating practices .
Hybrid sailing is an environmentally-friendly and realistic alternative
“In the short term, hybrid sailing is an environmentally-friendly and realistic alternative in the context of the maritime energy transition,” Marinus Jansen concludes. “It’s something that can already be done NOW, because it’s a mature technology. Hybrid solutions are therefore used more and more.”
“The Pacific6 aquaculture vessel is a good example. The vessel is equipped with a hybrid propulsion system and is powered by a Cat C18 propulsion engine, as a result of which it runs entirely on battery power when in use and when leaving and entering the port and it doesn’t emit any exhaust gases. This solution uses proven electrical components and power electronics from Caterpillar’s construction and mining product lines.”
If the underlying energy infrastructure and business models and legislation transform as quickly as technology, the alternative, environmentally-friendly energy supply can gain the upper hand more quickly. We are therefore looking forward to and are happy to contribute to meaningful and green hybrid/electric future for the maritime sector!
This article is shared by courtesy of Netherlands Maritime Technology – maritimetechnology.nl/en/ – The Netherlands Maritime Technology (NMT) trade association is the first port of call for and primary representative of the Dutch maritime technology sector.