Wind technologies for cleaner shipping

A large ongoing EU project demonstrates that the expansion of direct wind propulsion technologies for ships will be an important and impactful step towards cleaner shipping.

On a global scale, 80 to 90% of cargo is transported by ships. Ship¬ping therefore underpins the ever-increasing global trade. However, this high transport share also comes at a price, and while it is the most efficient means of transporting goods over long distances it still burns around 7 million barrels of oil every day – three to four times the oil exports of Kuwait – and generates CO2 emissions comparable with those of Germany or the whole of South America.

Shipping thus contributes signifi¬cantly to global warming and air pollution that endangers health. If shipping was a nation, it would be the sixth largest polluter in the world. The CO₂ emissions from shipping will grow significantly in parallel with the expected growth in the sector unless further actions are taken. The most important step towards cleaner shipping is to make shipping even more energy efficient. The development and use of cleaner fuels such as electricity (batteries and shore power) and electro-fuels is one essential course of action.

Operational measures, such as slower speed, better design and maintenance, etc., are further essential steps, and by combining efficiency technologies shipping can become even more energy efficient. However, another alternative that delivers propulsive energy very efficiently straight to the ship is to install sails, as wind technologies provide free non-polluting propulsion for the lifetime of the ship. For thousands of years, wind was the main technique used for ship propulsion, which is why ships are said to be “sailing” when they are at sea. Large commercial ships do not generally use sails any longer. Instead, they use oil. Hence, these ships do not “sail” – they pollute. Wind technologies provide the ship with free non-polluting energy directly at sea without investments in fuel infrastructure, and these technologies are increasingly available today.

Wind as green propulsion is more efficient than any green fuel, since the energy losses from generating, transmitting, converting, bunkering the fuel, and then delivering that power through the propulsion train to the propeller, accounting for up to 90% of the energy first produced. Meaning for every 1 kW of power to the propeller, 10 kW must be produced by a wind turbine or solar panel. Fuel savings from wind technologies retrofitted on existing large cargo or passenger ships are expected to be between 5 and 25% depending on ship size, type, speed, route and weather conditions, etc., as well as the type, size and number of wind technologies applied.

However, these numbers are based on a ship that still operates as a motorship, without making any changes to optimise wind use. For new ships, where wind technologies are further developed and fully integrated on vessels that are designed to use wind propulsion, fuel savings are expected to be well above 30%, and far greater when deployed on windier routes and operated more as a sailing ship. These facts led the EU to set up the Wind Assisted Ship Propulsion (WASP) project through the Interreg North Sea Europe programme. WASP has thoroughly investigated the potential of wind for ship propulsion, performing several real-life experiments by retrofitting different wind technologies on different ship types, operated as wind-assisted motor vessels. In the project, Flettner rotors, suction wings, and a rigid wing sail system are being modelled and tested on ferries and small cargo ships in the North Sea region.

Results from Scandlines ferry Copenhagen have been validated by WASP partner SSPA, and WASP sea trials confirm the potential for an annual average net fuel saving of around 4% with just one Flettner rotor. The Rörd Braren bulk carrier Annika Braren also has a Flettner rotor installed. WASP sea trial results confirm the potential for an annual average net fuel saving of 0.6–1 kg of fuel per nautical mile. She primarily sails North Sea and Baltic Sea routes. Boomsma Shipping’s general cargo vessel Frisian Sea also operates mostly on North Sea and Baltic Sea routes and test trials confirm a potential for an average yearly fuel saving of 0.6–0.8 kg per nautical mile. All results are route-dependent and are regularly updated on the project webpage:

Technologies that reduce fuel consumption will:

1. Reduce emissions of air and climate pollutants from the existing and future fleet.

2. Reduce the price gap between fossilfuelled ships and zero-emission shipping.

3. Reduce the investments and time needed for decarbonising shipping.

However, various market barriers (lack of information, a conservative industry, business structures, externalities, focus on short-term profit, etc.) slow down the rate of implementation of wind technologies. The related health and climate benefits thus remain unrealised. By externalising these costs and exploiting other indirect subsidies, the true costs of fossil fuels are masked. The barriers can be overcome by introducing flag- and technology-neutral regulations at IMO, EU, na¬tional and/or regional level. Furthermore, wind technologies for ships need to be further optimised, integrated, upscaled and standardised, and be manufactured in significant numbers to lower costs and improve efficiency and power, just as we have seen in the wind turbine industry over the last 30 years. With these measures to support wind propulsion systems, they will be ready to radically contribute to cleaner shipping in the coming decade.

Kåre Press-Kristensen & Tanja Willumsen, Green Transition Denmark

Gavin Allwright, International Windship Association


Ship name: Copenhagen
Type: RoPax Ferry
Vessel data: LOA 169 m; max beam: 25.4 m; 24,000 GT
Wind system installation: 5 m dia. and 30 m tall Flettner rotor (installed 2020).
Expected average annual fuel savings: 4%
Company: Scandlines
Ship name: Annika Braren
Type: Bulk carrier
Vessel data: LOA 86.93 m; max beam: 15 m; 5,023 DWT
Wind system installation: 3 m dia. and 18 m tall Flettner rotor (installed 2021).
Expected average annual fuel savings: 2–4% depending on route
Company: Rörd Braren Bereederungs-GmbH & Co. KG
Ship name: Frisian Sea
Type: General Cargo
Vessel data: LOA 118.19 m; max beam: 13.43 m; 6,477 DWT
Wind system installation: 2 x 11 m tall suction wings (installed 2021)
Expected average annual fuel savings: 2–4% depending on route
Company: Boomsma Shipping



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