Hybrid propulsion means a lot of things to many people, but flexibility and efficiency are key
“The problem with hybrid,” the salesman said, “is that it’s neither one thing nor the other.” A statement of the bleeding obvious, perhaps, but also a good point. Efficiency is not normally found in changing modes. Think of heat losses from a generator or the forces encountered by a hull at the interface between air and water. Whether thermodynamically or hydrodynamically, switching between media is not ideal.
There is an argument that hybrid is an in-between solution, caught between the age of diesel power and the emerging era of electric propulsion, representing the best of neither. In fact, the salesman quoted above was not a diesel devotee, as you may have imagined, but a representative of a global electro-industrial group. Hybrid propulsion will never last, he suggested, when the shipping world wakes up to full electrification.
But there must be a transition between the two worlds, and there is a lot to learn on the way – including where exactly we are going. If the long-term future is indeed electric, for all ships, then hybridisation is a step in the right direction. Purely electric vessels remain a distant ideal in most sectors.
If the internal combustion engine is the way forward for deepsea shipping, as many argue, there will be a long period before we find zero-carbon fuels to power those engines. Hybridisation will help vessels to reduce their greenhouse gas emissions in the interim. There are other benefits too. Peak shaving with batteries means gas engines can be run at a constant load – minimising knocking and misfiring – while efficient use of electrical power can reduce the cargo space lost to gas fuel tanks.
In another way, the very concept of hybridisation has helped marine engineers to think differently about propulsion, bringing advantages of its own. Earlier this week German propulsion specialist Schottel made a seemingly innocuous leap of logic when it announced a new ‘mechanical hybrid’ propulsion concept. The simple arrangement cleverly identifies that the electric element is not essential to many of the benefits of hybrid propulsion – namely the flexibility to operate more efficiently in several modes. That flexibility does not demand diesel-electric capability, but it may never have emerged without it.
There is an English idiom for when something is neither one thing nor another (the implication being that it may not be as good as either); neither fish nor fowl. As Schottel’s new concept shows, hybrid propulsion is not necessarily a choice between diesel and electric propulsion. Instead, it signifies a flexibility that contributes to operational efficiency. It is neither fishy nor foul, but an important step towards cleaner, more efficient future propulsion.
What do you think? Is the future battery powered? Will diesel never die? Does hybrid have to mean electric? Please send your comments to firstname.lastname@example.org