Shipping has great potential to reduce its environmental impact through new and modified propulsion technologies – but there is no single or simple answer that will meet every need or that can be applied to every type of vessel.
Instead, says a report by an expert working group at the Royal Academy of Engineering, further work is needed in two directions:
- to adapt current technologies from the maritime industries and elsewhere to broader application in different types of ship
- to research and develop innovative technologies specifically for maritime propulsion.
The Royal Academy of Engineering working party of more than 20 eminent engineering experts, led by John Carlton FREng, Professor of Marine Engineering at City University London, made a comprehensive survey of current and potential future marine propulsion systems, measuring them against the twin but related objectives of energy efficiency and environmental sustainability. Options investigated included greater use of LNG (liquefied natural gas) in current power units, battery and alternative fuel technologies, and nuclear-powered ships.
Professor Carlton said there was no obvious single “winner” in terms of technology in the medium to long term, and that operational issues were also an important contributor to power choices. “We know that larger ships are more carbon-efficient than smaller ships and that slower ship speeds effectively reduce emissions,” he said. “But fitting smaller engines in large ships may increase the risk of being under-powered in bad weather. Often there is significant benefit in simple operational measures: good seamanship in steering around bad weather for instance, or good housekeeping in minimising on-board energy consumption.”
The working party identified a range of short-, medium- and long-term ship propulsion options:
- In the short term and with current propulsion units, LNG is a known technology with standards already in place, and is cheaper and cleaner than diesel, but requires a global infrastructure. Gas turbines are a niche and the fuel is expensive, while renewables such as wind and solar may have application as auxiliary sources of power.
- In the medium and long term, biofuels and synthetic fuels are potential direct replacements for current fuels, but more needs to be done on the practicalities of storage, handling and environmental impact. Fuel cells of varying kinds offer promise, but require infrastructure investment and technological development to meet shipboard power requirements. Shipborne nuclear power has been used in naval ships, but for merchant shipping there would need to be changes in design, building and operational methods. Current battery technology may be restricted as a prime mover to smaller ships, but offers potential as an auxiliary power source.
Further ahead, the report says that hydrogen could be an option for marine propulsion, but there are significant infrastructure issues as well as technology issues to be overcome.
The Royal Academy of Engineering working party says that research and funding is needed to take some of the ideas forward, and broader “techno-economic” work is also needed to identify realistic targets in terms of emissions from the shipping industry.
The report is intended as a technical aid to the shipping industry which is under pressure internationally to improve its environmental record and increase efficiency. Sir John Parker, President of the Royal Academy of Engineering and himself formerly identified closely with the UK shipbuilding industry, said the report was both broad in its application and informed by the expertise that the working party had assembled.
Sir John said: “Shipping is vital to the world economy. It is a critical part of international import and export markets and supports the global distribution of goods. As for all industries, concerns about climate change require the reduction of greenhouse gas emissions from the shipping sector. This entails higher fuel prices for low sulphur fuels. It means that the industry must prepare for the new future and investigate alternative, more economic ship propulsion systems.”
Future Ship Powering Options: Exploring alternative methods of ship propulsion is available here.