Page 19: of Maritime Reporter Magazine (December 2020)

speeds on its surface thus generating of BF 4-6 (i.e an average 20kn wind very high lift for a much smaller sur- speed) by 2 – 3 rotors on deck, or 3-4 face. The only limitation of perfor- wing sails or a 400m2 airborne Kite mance is the Kite parachute material system. strength. For a 170m, 28,000 dwt handysize

The Kite seems ideal for ships that cargo ship, this is a 30% fuel saving have crammed deck superstructures, in such above average conditions per cargo cranes or other operational limi- time used, and for an Aframax tanker tations. it is a 15%, all considering a stable

Despite being a newly adopted ap- speed of 12kn. All that for a total ca- plication there are about 15 ships in pex of $1-2.5 million, depending on waters today that run with wind as- the arrangement.

sisted propulsion systems, and more are contracted, thus expected to dou- Setting Up the System ble by 2022. Every such technology The key question here for assessing under certain wind conditions (speed the Annual energy yield of any system and direction) will deliver a propul- and con? guration and optimize the In- sion thrust (and power) spectrum for a vestment, is the ‘Time Used’. And this given ship and deck arrangement, ba- is directly depended on the how and sis the aerodynamic physics applied. when the operators will ? nally use the

Wind Propulsion Principles is a com-

Then, certain restrictions such as in- system on board. plete handbook dealing with all currently teraction effects, windage resistance, To integrate properly a wind propul- applied wind propulsion technologies on boundary layer alterations, hull heel sion technology on a ship, the most board, seen through the lenses of the and leeway generation and limits for suitable arrangement has to be studied aerodynamic and hydrodynamic effects, ships safety, rudder effect and propel- which will ? t on deck without inter- ship operations in weather, design imple- ler ef? ciency reduction, all will apply rupting cargo operations or pose other mentation and investment yield assess- aggregately on the theoretical ? gures operational obstacles (i.e. such as ments, so that a uni? ed roadmap for de- for the speci? c ship. bridge passage limitations), but also cision making is available to the shipping

It then depends on the utilization arranged in a way to work without community. of the system: the more it is used, the impairing the ship’s course keeping,

Find more info here: bit.ly/3g9JcTM higher the annual energy yields. The maneuvering abilities and stability utilization is dramatically improved limits.

by continuous voyage optimization This requires detailed performance and weather routing, where studies have shown that it can prediction analysis, naval architecture and engineering stud- raise the bene? ts by even an extra 40% in speci? c routes. ies which are recommended to be performed by wind propul-

From various projects assessed so far, considering differ- sion specialists even on feasibility level before any invest- ent ship types and arrangements, considering global wind ment decision on wind-assist propulsion is made.

statistics, frequent trading routes and average sailing speeds, To maximize the energy yield potential of deck ? tted wind it seems that wind propulsion systems can deliver a range propulsors beyond the ship’s existing hull seakeeping limita- of 5-8 tons/day fuel consumption savings per ship size, con- tions – since existing ships were not designed considering sidering a theoretical forward thrust force with all restrictive aerodynamics force of high magnitude and dynamics as input parameters as mentioned above factored in. If a ship has an values – it is possible to retro? t them with extra hull append- average speci? c fuel consumption of 200 gr/kWh for the ages such as extended bilge keels, stern ? ns or others, which main engine – which is a typical realistic consumption tak- are again a subject of engineering analysis.

ing into consideration engine margins, engine condition and For those ship owners and operators that wish to investigate fuel quality (we are talking about existing ships here, over 7 further the potential of wind-assisted propulsion, understand years old), a realistic propulsive ef? ciency of 0.6 and a sail- the working principles of the technologies, review the criteria ing speed of 12kn, this translates to a net forward delivered which need to be satis? ed and identify the factors to be con- thrust of abt 100kN – 165kN. sidered for both existing and newbuilding ship applications,

Such range of net forward thrust can be generated within the ? rst shipping Industry publication is available since the the proven statistically high global wind intensities range summer of 2020.

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