Harnessing the power of the wind to supplement thrust developed by ships’ engines is now a key focus as shipping’s decarbonisation process becomes more pressing. Traditionally viewed with benign scepticism by shipping folk based on wind variance and the practical challenges of putting sails on cargo ships, today’s smart wind propulsion systems are rapidly climbing the decarbonisation agenda, both for new and existing vessels. A wide range of projects are at various stages of development, and LR is involved in many of them.

There are many concepts: from soft sails to hard sails; from wings and foils to kites. And if membership of the sector’s London-based trade body, the International Windship Association, is anything to go by, interest is surging forward. Over the past five years, its membership has grown from around 10 to more than 100. What has almost certainly helped to propagate this rapid development is shipping’s digital transformation, enabling real-time sensoring, accurate measurement, performance monitoring, and robust ship-shore connectivity.

Spectre of ETS adds urgency

Growing environmental concerns are providing another boost to the fledgling sector. Rarely a day goes by without mention of shipping’s carbon footprint and the slow progress in reducing it. The latest salvo launched at the maritime sector, without which world trade would grind to a halt, is the European Plan to include the global shipping business in its Emissions Trading Scheme (ETS) from 2022. The move is a further warning of what may happen if shipping doesn’t get a move on, environmentally.

Shipping economist Dr Martin Stopford pointed out recently that about half of shipping’s carbon emissions between now and 2050 will be generated by cargo ships that are already on the water today. Describing shipping’s 61,000-odd existing cargo vessels as a “real-time laboratory for developing and trialling new technology”, he pointed out that older ships have less capital tied up in them and therefore they are more suitable candidates for experimentation. Wind power retrofits are a great example.

Sailing more slowly is less of an issue for a fully written-down ship. And, Stopford said, just as shipowners continuously retrofitted boilers, engines and other machinery in the switch from sail to steam two centuries ago, so today’s owners should be testing carbon-reducing technologies, including wind power, in reverse.

Wind is free… except it’s not

Of course, the wind doesn’t blow all the time, but when it does, it’s free, and provides spectacular results. On some sea routes, wind is very reliable and potentially large energy savings are possible. But systems are expensive and the question of who foots the up-front bill is a constant constraint. However, creative thinking and new business models are making the up-front investment more affordable.

Some proactive charterers have shown a willingness to support projects with post-installation charter contracts, but as in other decarbonisation initiatives, more collaboration is necessary. Wind propulsion experts point out that proven technologies could face a rapidly expanding retrofit market as the IMO prepares to introduce its Energy Efficiency Existing Ship Index (EEXI) in 2023. Efficiency gains will be essential to to meet this requirement and with potential carbon levies on the horizon as well, the return on investment will improve.

One possible impact of the pandemic, according to LR’s Ship Performance Manager, Dr Chris Craddock, is that newbuilding plans are postponed or cancelled, existing ships are kept for longer, and more capital is freed up for performance improvements and carbon emission reductions. This process must, in any case, become a feature of shipping if there is any chance of meeting the IMO’s 2030 carbon reduction target and later its 2050 ambitions.

Only some of the concepts are likely to gain traction, but sails of one kind or another have already been installed on various cargo vessels. Modern-day development of the Flettner rotor, a cylindrical “spinning” sail developed by German engineer Anton Flettner, is being pursued by at least two companies, including Helsinki-based Norsepower and London-based Anemoi (see below).

LR verifies post-installation fuel savings

The wind propulsion sector was given a high-profile boost when Denmark’s Maersk Tankers decided to install two Norsepower Rotor Sails on its 109,647dwt Aframax products tanker, Maersk Pelican. The before-and-after results of the two-sail installation were independently tested and verified by LR and savings of 8.2% were clocked over the 12 months following the 2018 installation.

The two 30m-high, 5m-diameter Rotor Sails are types of Flettner rotors and use the Magnus effect to create forward thrust. LR’s Ship Performance team is continuing to monitor the tanker’s performance.

Helsinki-based Norsepower is a front-runner, with installations on four vessels: Viking Lines’ LNG-powered Viking Grace (Stockholm – Turku), Scandlines’ MV Copenhagen (Rostock – Gedser) and MV Estraden, a roro vessel owned by Finland’s Bore Line. Later this year, Norsepower will be retrofitting two 35m by 5m tiltable Rotor Sails on board the SC Connector, a ro-ro operating in the North Sea, which could achieve fuel savings of up to 25%, it is claimed. These will be the first tiltable Rotor Sail installations, a design initiative to counter air draught constraints.

Despite such installations, Norsepower CEO Tuomas Riski remains a realist. “Our technology is clever, but it’s not cheap,” he says. “Although our Rotor Sails were successfully installed on board the MV Copenhagen in just a few hours, this followed months of meticulous planning and, of course, design and manufacture of the sails themselves. Even before this, we knew we had to find a way of helping owners to fund the capital expense.

New pricing model

“Now, we can offer our Rotor Sails under the ‘Technology as a Service’ banner. This means that the upfront cost of the kit is replaced by a monthly fee based on the actual fuel that is saved. We believe this is a fair and equitable arrangement and should prove popular with ship operators who pay for their own fuel.”

Since the wind blows more steadily and strongly in some regions than others, the savings possible from shipboard installations vary widely. This was one of the factors that has led to the development of LR’s Flettner rotor simulator, a means by which the relative benefits for a certain ship type on a particular route can be estimated.

A recent project supported by the Wind Assisted Ship Propulsion (WASP) project and European funding has involved the installation of eConowind’s Ventifoil system on the 3,600dwt general cargo ship, MV Ankie, at Royal Niestern Sander shipyard in the Netherlands. The LR-classed vessel completed her first wind-assisted voyage this year, sailing from Delfzijl to Hamburg, then to Norway and back to Rotterdam. Fuel savings were projected to be about one tonne per day on the small cargo vessel.

In another initiative, LR has carried out computational fluid dynamics analysis for Windship Technology, of which ex-Concordia Maritime Managing Director and Chairman of Intertanko, Lars Carlsson, is a director. The widely patented Windship system creates additional forward thrust with a vertical rig comprising a three-wing set of foils 35-45 metres high. Windship’s technology is targeting the tanker, bulk carrier and ferry sectors. It has been tested in Southampton University’s wind tunnel and has had aerodynamic performance optimisation undertaken by flow analysis experts Cape Horn Engineering, in Portsmouth, UK. Windship claims that its wind-power system is the most powerful set-up so far. Combined with other energy saving initiatives and slow steaming, the company says it has the potential to cut fuel consumption and emissions by up to 80%.

“Over the past few months Windship Technology have taken a holistic view to a complete ship solution and have further enhanced their Windship rig system to include a new drive train and hull form. This has resulted in an 80% reduction in fuel consumption and the world’s first 100% net zero carbon vessel.” Simon Rogers, Director, Windship.

Anemoi’s spinning sail

London-based Anemoi, a specialist in harnessing wind power for commercial ships, has developed a range of patented Deployment Systems based on the Flettner rotor concept, which uses the Magnus effect to generate forward thrust from cylindrical sails that spin. Supported by LR in design services and plan approvals, the Anemoi Rotor Sails have been developed for all vessel sectors and wide-ranging operational conditions.

A first Anemoi system was installed at the company’s shore-based facility in 2014. This prototype Rotor Sail is used continuously in a coordinated test programme, providing data to optimise the technology. Research and development has involved scale model and wind tunnel tests.

The sails are based on three distinct arrangements and can yield fuel and emission savings of 5%-30%, the company claims. The first arrangement is a fixed installation, attached to the ship’s deck in one position. The second version is a folding system, allowing the sails to be lowered from vertical to horizontal for vessels with operational constraints, including port operations and air draught restrictions. A third, rail-mounted set-up allows the sails to be moved horizontally or longitudinally about the deck on arrival in port so there is no impact on cargo-handling operations.

The rail-mounted system, which consists of four rotors, was installed on the geared 64,000 dwt ultramax bulk carrier, mv Afros, in 2018 (pictured above). The vessel, owned by Piraeus-based Blue Planet Shipping, has since won a range of awards, including the ‘Ship of the Year’ at Lloyd’s List’s Greek Shipping Awards in 2018, and the 2019 Green4Sea ‘Dry Bulk Operator Award’.

Kim Diederichsen, Anemoi CEO, says: “This is a truly green technology which requires very little input from the crew. Maintenance costs are low, despite the Rotor Sails having a life span of 20+ years. We believe the technology will be integral in the shift towards sustainable shipping, a process which is accelerating as the maritime industry tackles the decarbonisation challenge.

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