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New Wind propulsion concepts and technologies to enable Wind-assisted Commercial ships and tankers navigating the seas

Marine propulsion is the mechanism or system used to generate thrust to move a ship or boat across water. The Navy and industry are investing in propulsion technologies that offer the potential to improve future naval ship designs. The goals of the current and planned technology development efforts are to improve affordability, power density, efficiency, and satisfy the energy demands of future mission systems. New generations of ship must meet new challenges, particularly in terms of energy efficiency, reliability and environmental impacts.

 

Wind propulsion technologies are emerging as one option which can help cut fuel costs significantly, make vessels compliant with existing and impending emission regulations and create energy security and long-term resilience in a volatile market. Over a period of centuries and even into the 20th century, wind driven vessels carried trade between nations. While paddles and sails are still used on some smaller boats, most modern ships are propelled by mechanical systems consisting of an electric motor or engine turning a propeller, or less frequently, in pump-jets, an impeller.

 

Modern wind- assisted propulsion technology differs from conventional sails in terms of efficiency, smaller windage area, and automatic control systems. New technologies leverage wind thrust and automatic control systems to optimize thrust force generation, adapting to wind conditions.

 

The IWSA said that an EU commissioned report has outlined the potential wind propulsion market by 2030, which could amount to 3,700 to 10,700 installed systems on bulkers and tankers, associated with approx. 3.5 to 7.5 Mt CO2 savings.

Wing driven ship concepts

Modern commercial vessels incur many times the weight of earlier generation wind-driven ships and require many times the propulsive power. The combination of environmental exhaust emissions regulations and fuel prices have prompted introduction of wind assisted vessel propulsion involving sails, kite sails, bladed horizontal-axis turbines and vertical-axis Magnus rotors. The power requirements of large commercial ships require future innovative breakthroughs in the variation and physical size of wind propulsion technology.

 

Wing Sail

As a result of rising oil prices in the 1980s the US government commissioned a study on the economic feasibility of using wind assisted propulsion to reduce the fuel consumption of ships in the US Merchant Marine. This study considered five different designs and concluded that with current technology the design that offered the greatest benefit would be the “Wing Sail Concept.” The “Wing Sail Concept” would largely be an automated system of large rectangular solid sails supported by cylindrical masts. These would be symmetrical sails which would allow a minimal amount of handling to maintain the sail orientation for different wind angles, however this design was at the expense of increased efficiency. A small freighter was outfitted with this system to evaluate its actual fuel gains with the result that it was estimated to save between 15–25% of the vessel’s fuel. Despite the positive findings of this study, the “Wing Sail Concept” failed to catch on and is not currently found on any commercial ships.

Wingsail » Green Marine Concepts BV

Kite sail

The kite sail concept has recently received a lot of interest. This rig consists of flying a gigantic kite from the bow of a ship using the traction developed by the kite to assist in pulling the ship through the water. Other concepts that have been explored were designed to have the kite rig alternately pull out and retract on a reel driving a generator. The kite used in this setup is similar to the kites used by recreational kiteboarders on a much larger scale. This design also allows users to expand its scale by flying multiple kites in a stacked arrangement.

Nothing found for Web Giant Kite Sail Will Pull Eco Boat Across The Atlantic | Boat, Kite sailing, Sailing

 

The idea of using kites is currently the most popular form of wind-assisted propulsion on commercial ships, largely due to the low cost of retrofitting the system to existing ships with minimal interference with existing structures. This system also allows a large amount of automation using computer controls to determine the ideal kite angle and position. Using a kite allows the capture of wind at greater altitudes where wind speed is higher and more consistent. This system has seen use on several ships recently with the most notable being MS Beluga Skysails, a merchant ship chartered by the US Military Sealift Command to evaluate the claims of efficiency and the feasibility of fitting this system to other ships.

TECHNOLOGY | SKYSAILS YACHT

Mega-size Kite Sails

Catamaran mounted super-sails that provide downwind propulsion would be mounted high above the water, allowing for installation of fold-up mega-size kite sails at lower elevation. Drones may be required to assist in launching such kite sails, larger versions of existing technology, where kite sail towing cables would be secured to the catamaran which in turn would be secured to the ships main hull in a manner to prevent catamaran pitching. Upon arrival outside the destination port, drones may assist in retracting and folding the kite sail for it to be placed into storage.

Skysails - Plus - Top 10 Green Ship Designs – gCaptain

Kite sails secured to each side of the hull would convert higher altitude energy from faster blowing crosswinds into propulsive force. However, mega-size kite sails main application would be to provide propulsion while sailing parallel to trade winds. The use of a bi-directional catamaran that couples to either ship bow or stern and includes mega-size kite sails, super-size sails and mega-size Flettner rotors would allow wind energy to assist in the propulsion of container ships where deck mounted sails would be impractical. Container ships would require an alternative wind power technology.

 

Forward Super Sails

The 20th century saw many innovative developments in textiles and fabric that included lightweight, ultra-strong, UV-resistant fabric such as Kevlar, nylon, rayon, glass fiber, carbon fiber and numerous other materials that could be used as sail material for boats. Combining development in materials/fabric technology with developments in frameless para-cell kites and kites that could be pumped with air pressure resulted in the appearance of rugged kites capable of withstanding severe wind buffeting. Such developments made possible the emergence of kites capable of towing a boat in severe weather conditions and propelling a boat using energy from severe crosswinds.

 

Modern freight ships are built to greater length and beam than earlier wind driven commercial ships. Several modern fabrics can offer higher tensile strength and even greater long-term endurance than earlier generation sail fabrics. Ships that bypass sailing under bridges may carry an extreme height of cable stabilized mast capable of securing a super-size sail system to be deployed when sailing parallel to trade winds. It could involve a width of 500-feet (150-m) with maximum height secured close to 200-m or 660-feet above sea level. It could be deployed in addition to airborne kite-sails.

 

Flettner Rotor

The third design considered is the Flettner Rotor. This is a large cylinder mounted upright on a ship’s deck and mechanically spun. The effect of this spinning area in contact with the wind flowing around it creates a thrust effect that is used to propel the ship. Flettner Rotors were invented in the 1920s and have seen limited use since then.

 

It was during the 1980’s that Canadian physics professor Dr. Brad Blackford built a small windmill powered boat capable of sailing into a headwind at great speed than sail-driven boats of comparable size. He eventually built a boat capable of sailing directly into a headwind at a speed of 8-knots. Ships assisted with vertical-axis Flettner rotor propulsion have also proven capable of sailing directly into a headwind, the rotors driving electrical generators to activate electrically driven propellers. Flettner rotors are an example of a growing wind propulsion trend in the industry, with  many  new vessels outfitted with rotors.

 

In 2010 a 10,000 dwt cargo ship was equipped with four Flettner Rotors to evaluate their role in increasing fuel efficiency. Since then, several Cargo Ships and a passenger ferry have been equipped with rotors. Recent examples include : “Viking Line has installed a Norsepower rotor sail unit on the cruise ferry Viking Grace, making her the world’s only working passenger vessel with a modernized Flettner rotor. ”  “Energy Technologies Institute and Shell, Norsepower installed two of its rotor sails aboard the LR2 tanker Maersk Pelican in August 2018”

 

In April 2018, cruise ferry M/S Viking Grace became the world’s first passenger ship equipped with a rotor sail, a vertical spinning cylinder that harnessed wind power to propel a ship. The  rotor installed on board Viking Grace is expected to slash the vessel’s fuel consumption and reduce carbon emissions by up to 900 metric tons annually. “Norsepower’s mission is to reduce the environmental impact of shipping by providing efficient, easy to use and reliable auxiliary wind propulsion for ships. Auxiliary wind propulsion is one of the key technologies for shipping to achieve the demanding fuel and emissions reduction requirements,” said Tuomas Riski, CEO, Norsepower.

 

 

Flettner Rotor Exceeds Expectations

The only parameter of the Flettner Rotor requiring control is the speed of the rotor’s rotation, so this method of wind propulsion requires very little operator input. In comparison to kite sails, Flettner rotors often offer considerable efficiency gains when compared to the size of a sail or kite vs. size of the rotor and prevailing wind conditions.

 

PDF] THE USE OF FLETTNER ROTORS IN EFFICIENT SHIP DESIGN | Semantic Scholar

Rotor Airfoils

Deck mounted airfoils have proven effective as vessel wind power propulsion technology capable of converting wind energy from crosswinds and diagonally approaching headwinds. Airplane hobbyists have built scale model airplanes that replace wings with transverse-axis Flettner rotors and still fly, also incorporating Flettner rotors into the upper wing surface. In maritime propulsion, a Flettner rotor installed into an airfoil sail prevents stalling on the downwind surface, increasing pressure difference between upwind and downwind sides and increasing propulsive force. Ships that do not need to pass under bridges could sail with extreme height of rotor-airfoil sails.

 

Staircase Airfoil

An aircraft hobbyist built a model plane with slatted, stepped or staircase wing configuration to allow low speed flight without stalling. The stepped wing is able to maintain very low air pressure on the equivalent of the wing upper surface at low flight speeds. When installed vertically on a boat deck, the stepped wing airfoil would maintain low air pressure on the downwind or shadow side, providing a large difference in air pressure between windward and downwind surfaces. For boat propulsion, being able to invert a staircase airfoil would offer greater versatility in terms of wind direction.

 

Mega-Scale Wind Technology

The propulsive power requirements of commercial ships involve massive amounts of power, such as 25,000 to 35,000-horsepower. At the present time, the largest 3-bladed wind turbines develop 12,000kW or just over 16,000-Hp. Severe winds have caused the structural collapse of wind turbine towers. As a result, ship pitching and rolling could cause destruction of the tower of a mobile super-size horizontal-axis wind turbine. There may be scope to develop mega-scale vertical-axis wind turbines such as Magnus (Flettner) rotors on floating platforms and capable of withstanding severe ocean wave imposed dynamic structural loadings.

 

A pair of mega-size Magnus rotors mounted on a bidirectional catamaran may be coupled to the stern of a commercial ship. The catamaran twin hulls may be spaced 100-m or 300-feet apart, with the Magnus rotors extending up to 200-m above the twin hull platform. Torque reaction control arms secured to the ship’s hull would minimize catamaran pitching. Magnus rotors would drive electrical generators that would supply power to electric motors installed inside the ship and drive propellers. Such wind technology could propel ships sailing westbound across the North Atlantic from Europe to North America.

 

Future research could explore the possibility of installing ultra-tall masts on bi-directional twin-hull catamaran units to be coupled to a ship’s bow area at multiple elevations and points so as to minimize or eliminate pitching movements. The same catamaran hull could also carry Flettner rotors to be deployed when the same end is coupled to a ship’s stern, with ship sailing into a headwind. Ship bow and stern would include identical couplings for the catamaran, with forward mega-sails deployed while sailing downwind. The catamaran would be attached to and detached from a ship outside of the port terminal area.

 

Future research into wind powered ship propulsion would likely focus on developing much larger scale wind turbines capable of sailing ships directly into headwinds. Due to space restrictions at port and comparatively low roadway bridges at several ports, separate floating platforms would carry mega-scale wind turbines. In some cases, the wind turbines would generate electric power to sustain operation of the ship propeller(s), in which case the ship would tow the turbine platform. Special levers would connect to the ship hull to minimize pitching of the turbine platform.Ocean waves would impose mechanical stresses on mobile towers carrying horizontal-axis wind turbines, thereby limiting turbine diameter. Future research would determine the maximum size of ocean going 3-bladed wind turbine and maximum size of vessel. Such research would also determine the maximum size of Magnus (Flettner) rotors carried aboard separate catamaran platforms, turbine power capability and maximum size of ship to be powered by such technology. There would likely be scope to use lightweight, high-strength material in the construction of future mega-scale mobile wind turbines.

 

 

Challenges for Wind propulsion Adoption

Many innovative wind propulsion technology concepts have been and are being developed for commercial shipping. However, none of the technologies has reached market maturity yet. A study, commissioned by DG Climate Action, that  focuses on the direct utilisation of wind for the propulsion of commercial ships in the form of wind-assisted shipping.

 

The study found that Multitude of barriers that currently prevent the further development and uptake of wind propulsion technologies for ships; three key barriers thereby stand out:

  • (Trusted) information on the performance, operability, safety, durability, and economic implications of the wind propulsion technologies.
  • Access to capital for the development of wind propulsion technologies, especially for building and testing of full scale demonstrators.
  • Incentives to improve energy efficiency/reduce CO2 emissions of ships.

These key barriers are interrelated in different ways, with the most crucial interaction being a chicken-and-egg problem between the first and second key barrier. In order to breach this chicken-and-egg problem, we see the development of a standardized method to assess wind propulsion technologies combined with test cases to develop this assessment method as the most important starting point for overcoming the barriers.

 

In order to determine the savings potentials, models have been developed for the different wind propulsion technologies. The models have been used to determine the technologies’ power savings for six sample ships across AIS-recorded voyage profiles and for sample routes, differentiating two speed regimes respectively.

 

The results indicate that the considered technologies can have significant savings potentials. More in specific, for the sample ships and selected wind propulsion technology dimensions, savings are found to be comparable for Flettner rotors and wingsails (5-18% in high speed scenario), with relative savings on the larger ships exceeding those on the smaller ships, especially for bulk carriers.

 

For towing kites relative savings (1-9% in high speed scenario) are, compared to rotors and wingsails, higher for smaller vessels and lower for larger vessels; relative savings are lowest for wind turbines (1-2% in high speed scenario). An important finding is that absolute savings are larger at the higher voyage speed for the wingsail and the rotor for all ship types considered.

 

Should some wind propulsion technologies for ships reach marketability in 2020, the maximum market potential for bulk carriers, tankers and container vessels is estimated to add up to around 3,700-10,700 installed systems until 2030, including both retrofits and installations on newbuilds, depending on the bunker fuel price, the speed of the vessels, and the discount rate applied. The use of these wind propulsion systems would then lead to CO2 savings of around 3.5-7.5 Mt CO2 in 2030 and the wind propulsion sector would then be good for around 6,500-8,000 direct and around 8,500-10,000 indirect jobs. The study has been jointly carried out by CE Delft, Tyndall Centre for Climate Change Research, Fraunhofer ISI, and Chalmers University of Technology.

 

This report was compiled in 2016-17 prior to much of the SOx regulation uptake and over a year before the IMO GHG initial strategy adoption. As it currently stands, there are a number of ready for market wind-assist technology providers in the retrofit market, with an increasing number of retrofit installations of proven rotor technology and test rigs and a growing number of other retrofit technologies and newbuild designs are in late stage R&D or moving towards sea trials.

 

 

New Wind power Concepts and technologies

At the most recognisable end of the wind-assist spectrum are innovations in soft sail systems. The increasing sophistication of automation and route optimisation systems have revived interest in seafaring’s original power source, and there are now a growing number of examples of larger vessels using smart soft sails alongside auxiliary propulsion systems. In one notable development, French naval architect VPLP recently unveiled a design for a 121 metre long roll-on/roll-off (RORO) vessel that will be used to transport components of the Ariane 6 rocket from Europe to Guiana. The ship’s main propulsion system (a dual fuel LNG MDO engine) will be assisted by four Oceanwings; fully automated wing-sails which are each supported by a 30m high mast and measuring a total of 363 square meters.

 

At the most recognisable end of the wind-assist spectrum are innovations in so sail systems. The increasing sophistication of automation and route optimisation systems have revived interest in seafaring’s original power source, and there are now a growing number of examples of larger vessels using smart so sails alongside auxiliary propulsion systems. In one notable development, French naval architect VPLP recently unveiled a design for a 121 metre long roll-on/roll-o (RORO) vessel that will be used to transport components of the Ariane 6 rocket from Europe to Guiana. The ship’s main propulsion system (a dual fuel NG MDO engine) will be assisted by four Oceanwings; fully automated wing-sails which are each supported by a 30m high mast and measuring a total of 363 square meters.

 

There is also growing interest in the use of rigid hard sails, which are sometimes preferred over so sails because of the potential for  incorporating dierent aerodynamic structures or even photovoltaic coatings. As with so sail innovations, there are numerous ongoing initiatives in this area exploring the application of the technology to vessels of various dierent sizes. In one recent development, Japanese rms Mitsui OSK lines and Oshima shipbuilding received Approval In Principle from marine classication body ClassNK to build a 100,000 DWT bulk carrier equipped with a telescopic hard sail system that the group claims could reduce fuel usage by as much as 8 per cent.

 

Whilst the ability to automate, deploy new materials, and use data to optimise performance is breathing fresh life into the use of traditional sails, they do come with some signicant challenges as they are scaled up in size. Not only do they take up large amounts of deck space (valuable real-estate in the commercial shipping sector) but they can also induce a signicant amount of heeling (or tipping from side to side) in the vessel.

 

One concept that potentially gets around this problem is an innovative device known as a suction wing, a deck mounted vertical foil claimed to provide considerably more power per square metre than a normal sail at a fraction of the height. Based on technology originally pioneered by marine explorer and conservationist Jacques Cousteau, these systems use a powered suction device mounted within the wing to suck in the boundary layer around the foil and increase its propulsive eciency.

 

One of the key players here is Netherlands rm Econowind, whose so-called Ventifoil technology – a non-rotating wing with vents and a powered internal fan – can either be retroed to the deck of a vessel, or deployed within containers that are added and removed as and when required.

 

Commercial tankers using sail power to navigate the seas could be the wave of the future.

Norsepower Oy Ltd, a Finnish engineering and technology company  announced in March the installation and testing of Flettner rotor sails onboard a Maersk Tankers vessel. The project, which will be the first installation of wind-powered energy technology on a product tanker vessel, would provide insights into fuel savings and operational experience.

 

Maersk Tankers will supply a 109,647 ton Long Range 2 product tanker, which will be retrofitted with two 98 feet tall by 16 feet in diameter Norsepower Rotor Sails. The design would look like narrow smoke stacks. Combined, these are expected to reduce average fuel consumption on typical global shipping routes by 7-10 percent.

 

The Norsepower Rotor Sail is a modernized version of the Flettner rotor — a spinning cylinder using the Magnus effect to harness wind power to propel a ship. Each Rotor Sail is made using the latest intelligent lightweight composite sandwich materials. When wind conditions are favorable, the main engines can be throttled back, providing a net fuel cost and emission savings, while not impacting scheduling.

 

Norsepower’s Rotor Sails may not already be installed on the 20,000 applicable vessels in the global fleet, but we have a proven commercial product that could reduce emissions by 10 to 15% per ship,” Mr Riski continued. Tuomas Riski, CEO of Norsepower, said in a release: “As an abundant and free renewable energy, wind power has a role to play in supporting the shipping industry to reduce its fuel consumption and meet impending carbon reduction targets.”

 

He explained that this does not limit the reductions that could be made by those ships, as multiple technologies sit happily alongside Rotor Sails, like hydrodynamic hull optimisation, heat recovery, and alternative fuels.

 

 

Demonstration Projects Seeks to Validate Wind Rotor Technology

A Norsepower Rotor Sail was installed in May 2020 on Scandlines’ ferry the Copenhagen, which operates between Rostock, Germany and Gedser, Denmark. The 21-ton steel foundation for the Rotor Sail was put aboard the vessel during at shipyard visit in November 2019. The 30 meter (98 foot) rotor with a 5 meter diameter (16 foot), which weighs 42 tons, was installed on the vessel during a normal overnight stay in Rostock while the vessel was in operation.

 

“We were able to complete almost everything within the limited time of just a few hours,” commented Captain Alan Bach of the Copenhagen. “This was key as we are operating on a 24/7 basis, every loss of service or revenue is naturally critical for ferry operations.” This is the fourth vessel installation completed by Norsepower under the pilot project. They point out that the Norsepower Rotor Sail Solution can be installed on new vessels or retrofitted on existing ships. It is a modernized version of the Flettner rotor, a spinning cylinder that uses the Magnus effect to harness wind power to thrust a ship.

 

Installed as part of the EU Green Deal that aims to lower pollution and carbon levels across Europe, this is seen as a highly visible demonstration of the technology due to the fact it is a ferry transporting passengers across the Baltic. According to Scandlines, the rotor is drawing a lot of attention and questions from passengers about the technology. The Copenhagen is already one of the world’s most energy-efficient ferries. It was built with hydrodynamic hull optimization and a hybrid-electric propulsion system with battery-powered energy storage. The rotor system is expected to deliver on average between a four to five percent fuel savings, corresponding to the same amount of CO2, and in optimal wind conditions can produce more than a 20 percent savings for vessels.

 

As the installation aboard the Copenhagen is a pilot project for WASP, they will be carefully monitoring the equipment seeking to validate the equipment and its performance. “We are very happy that the system is fully automated and we’re expecting little in the way of technical problems,” reported Scandlines COO Michael Guldmann Petersen. “The last month of operations has been quite smooth and we see that continuing throughout the test period. We’re expecting a four to five percent reduction in CO2 emissions, which is not an insignificant amount, and if everything goes well, we are considering further installations in the future.” While the test has just commenced, everyone involved points out that wind propulsion technologies are a very visible statement from a shipping company about their commitment to decarbonize their vessels. It is believed that it can provide a significant contribution towards the IMO’s target to cut by half greenhouse gas emission from the maritime industry by 2050.

 

Lloyds Register’s Craddock, though broadly positive about the role that could be played by wind assist systems, warned that there is still a long way to go. “ Wind technologies are generally acknowledged as a credible energy saving technology that could be applied to merchant shipping and reduce carbon emissions for certain ship types and sailing routes,” he said. “However, since wind technologies are generally at a low level of technology readiness, there is a cautious interest by most of the market, with some of the larger charterers directly investing in technology development programs and pilot projects. As more technology demonstration pilot projects are successfully completed raising condence in the technology, and new build contracts are placed specifying these technologies, payback periods will drop and there will be a steady increase in the uptake of the technology.”

 

UK-based Windship Technology announced in Sep 2021 that its patented triple-wing rig has received ‘Approval in Principle’ (AiP) status from shipping classification society DNV.

This significant milestone in the company’s history is the result of years of design iteration work combined with the use of cutting-edge CFD to refine the wings before extensive wind tunnel testing and analysis by independent third parties. Each wing has trailing edge flaps that allow for optimisation of the motive force produced for a variety of incident wind angles and, crucially, allow the rigs to produce the highest power density of any current wind-powered solution. With three rigs set, they can produce all the power required to sail an 80,000dwt ship on the main long transoceanic routes.

 

Windship Technology is developing not only rigs but also an overall solution for Zero Emission shipping. The design starts with the rigs, constructed from composite materials to reduce weight at height, and goes further with an incorporated diesel electric drive featuring a full carbon capture system that dramatically reduces fossil fuel consumption whilst eliminating NOx, SOx and particulate matter and zero CO2.

 

The wings deployed on vessels are located on a steel cruciform base which provides the intersection with the ship and also house the lifting and lowering mechanism – especially important for port access and bridge height clearance. The rigs can be lowered either fore and aft or over the ship’s side as required for loading and unloading operations. Whilst underway, the rigs are automatically controlled, rotating to gain the greatest motive advantage from the available wind power.

 

 

 

References and Resources also include:

http://www.motorship.com/news101/engines-and-propulsion/wind-as-a-viable-future-propulsion-technology

https://www.maritime-executive.com/article/demonstration-projects-seeks-to-validate-wind-rotor-technology

https://www.maritime-executive.com/article/project-unites-wind-propulsion-and-hydrogen-generation-to-create-fuel

https://www.theengineer.co.uk/wind-ships-marine-propulsion/

https://shipinsight.com/articles/windship-technology-gets-dnv-aip-for-wind-propulsion-system/

About Rajesh Uppal

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