Green Ships

Support Vessel Hodor Catamaran with Airbus H145 helicopter at stern
Hodor Catamaran, built by Astilleros Armón – photo courtesy of Clint Jenkins

Ships of the Future

Imagine the Clippers that sailed the world trade routes during the late 19th century. Built for speed to meet the demand for faster delivery of tea from China and passengers to the Far East, in competition with our European “allies”. How much carbon dioxide did they produce? Negligible, compared with modern container and cargo ships that produce up to 3% of all greenhouse gas emissions and contribute to acid rain. We must now look to the green ships of the future.

Another Oil Spill

We have just witnessed a massive volcanic eruption in Tonga that caused a tanker unloading crude oil at a refinery over 6,000 miles away in Lima, Peru to spill 6,000 barrels of oil into the sea creating an ecological disaster.

Why are we transporting vast amounts of crude oil around the world? Remember the Amoco Cadiz, the Atlantic Express and the Gulf of Mexico spills, to name but a few? The largest spills have released tens of millions of gallons of oil and have resulted in fouled coastlines, polluted fisheries, dead and injured wildlife, and lost tourism revenue.

The Roadmap to Greener Ships

It is accepted we need to reverse the ever-ascending dependence on fossil fuels since the Industrial Revolution. Let’s consider how to achieve this for ships. The Clippers of the past depended on sails as their propulsion to “clip through the wind”. Smarter sails and new forms of propulsion are a possible solution. How else can we use the environment that ships operate in to make them greener? The water and the sun. Do we need new technologies or old concepts modernised? Let’s explore each of these options and how the shipbuilding industry is rising to the challenge to revolutionise our future maritime transport. 

Smart Sails that Don’t Flap

Have you heard of the Magnus effect? It is the force exerted on a rapidly spinning object moving through air or another fluid in a direction that is at an angle to the axis of spin. Simple really. Use sails that spin and don’t flap. It’s called a Flettner rotor and you can find how it works here.

Naos Design of Italy are working on fitting eight different ship types with a pivoting, foldable hard wing: and Wallenius Marine of Sweden, in partnership with Alfa Laval, expect their Oceanbird fully wind powered vessel, capable of reducing emissions by 90%, will be sailing in 2025.

Michelin of France have engineered wind sail mobility (WISAMO) inflatable sails for leisure boats to freighters.

Take the sail off the ship and it becomes a kite. A 500 square metre, deployable “Seawings” kite is now being trialled on the 154-foot cargo ship Ville de Bordeaux that carries aeroplane parts across the Atlantic. If successful, French company Airseas will develop a 1 000 square metre version. How often does a ship follow the course of the wind?

A kite towing an ocean freighter: Seawing on the Ville de Bourdeaux by Airseas
Seawing on the Ville de Bourdeaux by Airseas – photo copyright © Airseas

Electric Propulsion for Ships

The Royal Navy’s new aircraft carriers, HMS Queen Elizabeth and HMS Prince of Wales, use integrated electric propulsion. That is two gas turbine and four diesel engine generator sets producing three-phase electricity for four energy efficient electric propulsion motors to turn the 6.7 metre diameter, 33 tonne propellers, as well as supply the ship’s low voltage supply. But can we use different sources to power the motors, such as solar or alternative fuels?

Planet Solar of Switzerland’s 115-foot, 100-tonne catamaran, fitted with 537 square metres of solar panels has completed a world circumnavigation trip with no fuel. But relies on battery storage. Torqueeda of Germany has developed 80HP, flat design, lithium-ion batteries but much still needs to be done on battery design. 

Alternative Fuels

Deen Shipping & Marine’s 6 100-tonne chemical tanker MTS Argonon is powered by 80% liquified natural gas and 20% diesel oil. This reduces CO2 emissions by 20 to 25%. But the LNG requires storage tanks as does hydrogen needed by fuel cells. Fuel cells work like batteries, but they do not run down or need recharging. They produce electricity and heat if fuel, like hydrogen, is supplied. Hydrogen has been seen as a fuel of the future for all vehicles for a long time, but it must be produced from sustainable sources to make it viable as this video explains:

Sea water is H2O so producing hydrogen from water by electrolysis is an option. New technologies using sustainable solar and wind power are promising but further research and development is needed. Namibia has large areas with continuous access to solar and wind power and an extensive coastline. Given sufficient investment, Namibia can become a leading player in developing hydrogen as the fuel of the future. See Energy Observer world’s first hydrogen powered boat at

Future Ships May Fly

Cars run on a flat surface; trains run on rails. Water is 784 times denser than air. The drag on the hull of a ship is like driving a car up a 45-degree slope. Let’s take the hull out of the water. It’s been tried with ships up to frigate size.

In 1969, the US Navy started trials of a 310-tonne experimental warship “Plainview” with hydrofoils that achieved 40 knots. But there was one big problem: it takes a humongous amount of energy to get a big ship’s bow out of the water. The Soviets tried another approach in 1987 with the Ekranoplan. Although it looked like a plane it was classified as a ship as it developed its lift from “ground effect” by flying over the sea at no more than 20 feet. 

A-90 Orlyonok at the Museum of the Navy, Moscow
A-90 Orlyonok at the Museum of the Navy, Moscow – Mike1979 Russia; licensed under CC BY-SA 3.0

With smaller craft, hydroplanes are already revolutionising smaller sports and leisure boats. I may expand on this in a future article on technology advances for recreational boats.


Hovercraft, another approach to using ground effect, was invented by British engineer Christopher Cockerel. In 1961, the United Kingdom set up the Interservice Hovercraft Trials Unit (IHTU) based at RNAS Lee-on-Solent (HMS Daedalus), now the site of the Hovercraft Museum, near Portsmouth, while I was there during my engineering apprenticeship.

They were trialled for their potential use as armed amphibious craft and deployed briefly in Borneo. We could have used a few in the Falklands War in 1982! In commercial service, they were used as cross channel ferries and are still operational as the fastest Isle of Wight ferry route across the Solent. It is now the world’s only year-round passenger hovercraft service.

Multihull Vessels

Multihull vessels such as Catamarans and Trimarans have narrow beam multiple hulls that have good wave-piercing properties. Their speed is not limited by the drag created by monohulls’ bow wave and wake. Mega Catamarans over 100 feet in length can achieve top speeds of 40 knots.

The current largest in the world is ‘Hodor’ at 217 feet. It is a support vessel that shadows its owner’s super yacht to carry other watercraft such as jet skis and dinghies and a helicopter (who would be without one?). So far, multihulls have only been used commercially as passenger ferries and in the tourist industry. 

MV Hodor Catamaran support vessel from above
MV Hodor Catamaran support vessel from above – photo courtesy of Clint Jenkins

In 1998, I retired from the RN as Senior Naval Aviation Adviser at the Defence Evaluation & Research Agency, Farnborough, and joined them for eight years after their transition to become the QinetiQ Group Plc. In 2000, they took delivery of RV Triton, a 2 236 tonne, 318 feet long warship technology demonstrator trimaran from Vosper Thornycroft.

It was used for an extensive period of trials and proved the concept was structurally sound in sea state seven and was a viable design option for a future RN surface combatant. It was also the first trimaran to conduct trials of operating a helicopter. In January 2005, Triton was sold to Gardline Marine Sciences, who used it for hydrographic surveys and, in January 2007, contracted it to the Australian Customs Service for border protection services.

Research Vessel Triton, showing trimaran form
Research Vessel Triton, showing trimaran form

Artificial Intelligence and Automation

Yes, this has a place in future green ships too. In September last year the Mayflower Autonomous Ship AI research trimaran sailed from Plymouth without any crew onboard for trials in the Atlantic. It is driven by solar powered electric motors and has a suite of sensors and computer control with machine learning and automation software to ensure that decisions are safe and in-line with collision regulations.

Imagine a cargo ship that has no crew to take hostage, and alarm systems that prevent pirates taking control. Mayflower will conduct further trials this Spring. You can learn more about it and follow its future progress at Mayflower Autonomous Ship.


Green ships of the future may use a combination of the technologies described above to reduce their greenhouse emissions in a sustainable way. A deeper study of the subject is available at Marine Insight.

But should we not also question why we are transporting vast quantities of crude oil, aircraft parts and all manner of trade, even refrigerated fresh produce, over vast distances of the globe? Can we not ensure the bulk of our trade is with our local neighbours in a tariff free environment?