Celtic Mist Technical Considerations

We must consider sea-keeping and particularly structural strain: deck buckling, torque on SRT800/SRT1600 mounting, and torque on mast from spinnaker in "steady state" testing: analysis below assuming a: 300m2 spinnaker; modeled with a point of sail: "running" (0° to downwind) in up to 25 knots winds; foil lift not accounted for, no figure- of-eight typical of kite sail maneuvers.

Michael Tyrrell of Arklow Marine Services suggested that the Celtic Mist would be ideal for this SRT turbine proof-of-concept, because it could tow the SRT800 or SRT1600 when under sail on any ordinary voyage and the only possible temporary addition to the Celtic Mist's deck equipment would be a roller on the sternpost to allow a cable to the anchor winch.

The SRT800 turbine is only 1.2m diameter and 1,200 kg weight, and Gizara calculates its drag at a maximum of 8.5 knots vessel velocity to be no more than 5kN. Of course, the turbine would not be developing anything like its full power, but it should be enough to produce useful data on the concept. It would not need to be brought inboard when not being used, as it could hang over the stern at sea, and be detached on return to port. The equipment for measuring the output of the turbine in relation to wind speed and sail area need not be on the deck at all.

According to Mr. Simon Berrow [[email protected]], Sent: 30 January 2013 17:17: "Regarding sailing and technical questions I will let Fiacc [ Cc: [email protected]; [email protected] ] respond…".

SRT800/SRT1600 Analysis http://www.schottel.de/news-events/news/news-detail/? tx_ttnews[tt_news]=113&cHash=2a6dc83c6dd932896be9595e054fe313

Type Inner diameter Rated power [mm] [kW] SRT 800 800 200 SRT 1600 1600 800

SRT800 specifications for Celtic Mist

SCHOTTEL Rim Thruster (SRT800) size:

Inner diameter 800 mm.

Outside diameter from appearance, outer housing width "looks to be" half the radius, thus 1.2m outside diameter is a reasonable mean estimate.

Celtic Mist Technical Considerations Page 1 of 3 Weight estimate by comparison to Totally Enclosed Fan Cooled (TEFC) extreme duty AC induction generator/motors: Toshiba, model A4004FLF4OM, 400 hp, 3909 lbs. http://ps.thomasnet.com/productsearch/itemdetail.html? cid=1078273&cncat=3332&cnprod=1033&cnitem=2480

Toshiba, model B5004FLG3BM, 500 hp, 4755 lbs. http://ps.thomasnet.com/productsearch/itemdetail.html? cid=1078273&cncat=3332&cnprod=1033&cnitem=2511

Therefore, approximately 10 pounds per rated horsepower or 0.006 kg/W

SRT800 Rated power: 200 kW: therefore approximately weighs 1200 kg

Assuming a 300m2 Spinnaker, http://www.intpowertechcorp.com/SRT_model.xls "Equations" tab cell B5="0.8", cell B8="300":

Celtic Mist (specified power needed to overcome drag @ 8.5 knots, the sole data point for vessel drag): 260995 W plus SRT800 power 21518 W (given by "mouse-over" the plot line from the Tab "Power (Vessel Velocity)") @ 8.5 knots vessel velocity, gives total power required = 282513 W.

Thus, working backwards -- "mouse-over" the plot line from the Tab "Power(Wind Speed)", a wind speed of 22.3 knots is required to attain 282513 W from a 300m2 sail.

The force on the 300m2 spinnaker at 22.3 knots wind speed is 24.7 kN ("Force (wind speed)" tab). The force on the SRT800 at 8.5 knots Vessel Velocity (from the "Force(Vessel Velocity)" tab), is 4921 N.

SRT1600 Specifications for Celtic Mist

SCHOTTEL Rim Thruster (SRT1600) size:

Inner diameter 1600 mm.

Outside diameter from appearance, outer housing width "looks to be" half the radius, thus 2.4m outside diameter is a reasonable mean estimate.

Weight estimate by comparison to Totally Enclosed Fan Cooled (TEFC) extreme duty AC induction generator/motors (as referenced above), approximately 10 pounds per rated horsepower or 0.006 kg/W

SRT1600 Rated power 800 kW: therefore approximately weighs 4800 kg

Celtic Mist Technical Considerations Page 2 of 3 Assuming 300m2 Spinnaker, http://www.intpowertechcorp.com/SRT_model.xls "Equations" tab cell B5="1.6", cell B8="300":

Celtic Mist (specified power needed to overcome drag @ 8.5 knots, the sole data point for vessel drag): 260995 W plus SRT1600 power 86072 W (given by "mouse-over" the plot line from the Tab "Power (Vessel Velocity)") @ 8.5 knots vessel velocity, gives total power required = 347067 W.

Thus, working backwards -- "mouse-over" the plot line from the Tab "Power(Wind Speed)", a wind speed of 23.9 knots is required to attain 347067 W from a 300m2 sail.

The force on the 300m2 spinnaker at 23.9 knots wind speed is 28.4 kN ("Force (wind speed)" tab). The force on the SRT1600 at 8.5 knots Vessel Velocity (from the "Force(Vessel Velocity)" tab), is 19684 N.

Comments: The SRT1600 generator would likely be operating far below its sweet spot, but that probably means a generator efficiency of 70-80% instead of 90+% (not to be confused with total turbine efficiency probably 35-40% instead of ~50%) at rated power... The advantage compared to the SRT800, is a greater range of discernible power output from the generator per wind speed for a given sailplan, thus affording a greater window of opportunity for testing.

Two factors reducing accuracy: the ideal model in this workbook presumes 100% efficiency of the spinnaker, and no lift created by the foil effect, as for instance "like a wing" for a fore-and-aft rigged vessel.

Questions:

 Celtic Mist: Sail Area? (guessed 300m2)

 What we desired, but have yet to see, is empirical data showing a continuous, approximately parabolic curve of power needed to overcome Celtic Mist’s drag per vessel velocity…Is this available?

 Sailplan: Does rigging provide for: Spinnaker? Kite Sail?

Test Plan:

 Open water testing itself will likely require reserving (3) two week periods, a total of six weeks of testing, in three different trials over a period of two years.

 Arklow Marine Services, Ireland to bid for docking/maintenance/modification to install SRT800/SRT1600 on the Celtic Mist (17m, c30 tonnes) for the (3) two week periods, a total of six weeks of testing over a two year period.

Celtic Mist Technical Considerations Page 3 of 3