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A windmill ship, wind energy conversion system ship or wind energy harvester ship propels itself by use of a wind turbine to drive a propeller.

They use wind power^[1] through a mechanical or electrical transmission to the propeller. Where transmission is electric, storage batteries may also be used to allow power generated at one time to be used for propulsion later on.

Windmill ships should not be confused with rotor ships, which instead rely on the Magnus effect for propulsion.

Points of sail

Equipped with a wind conversion device that can rotate 360° no matter in which direction the ship is heading, a windmill ship can sail in any direction.

It can move directly upwind, a point of sailing unachievable by other sailing craft. Here a wind turbine powers a water propeller. Because the power produced depends on the apparent wind strength, a large amount of power is transmitted to the propeller.^[2]^[3] In order to operate efficiently in the typically slow speed through the water, the propeller must be large enough to generate more upwind thrust than the combined downwind force of the wind turbine and the air and water resistances of the ship structure itself.

With the wind from the side, i.e. on a reach, the wind turbine's thrust pushes the ship sideways, which should therefor have a lateral surface such as a keel in order to reduce leeway. Thus equipped the wind turbine can be also be used in an autogyro mode. That is, no rotary power is transmitted and the wind turbine acts in the same manner as a static sail and the ships's speed could exceed wind speed in the same way as with many other sailing craft.

Sailing downwind, the apparent wind decreases the more the ship speeds up and at exactly the true wind speed, would drop to zero, so that the wind turbine can generate no power and also no thrust if used in the autogyro mode. Therefor windmill ships are limited to less than wind speed when travelling directly downwind, as with other sailing craft. Theoretically the wind turbine could be used instead as an air propeller and the water propeller as a water turbine. The direction of power is then reversed and such a windmill ship could accelerate through the region of zero apparent wind and exceed the wind speed directly downwind. As this requires both the air and water devices to be constructed differently than usual and extremely low water resistance from the hull, this has not been achieved so far with ships, but has been achieved with land yachts. These travel on wheels which offer very little resistance at high speeds compared to that of even the best hulls through water.

Types

Several types can be made; these include wind-turbine-only ships as well as hybrid ships which store wind power from the turbine when the ship does not need to be propelled. To reduce the energy required to propel the boat, windmill ships are often equipped with low-friction hull designs, such as multihulls, or they are hydrofoils. Boats without low-friction hulls or hydrofoils can be equipped with wind turbines, but often the force generated by the turbines alone is not sufficient to propel the craft. In this case, the turbines only provide supplemental force to conventional sails or other propulsion systems.

At present, research is ongoing and the best types of bladed rotors still need to be determined. For example, high horizontal axis windmills are proven to make the ship less stable. Therefore, vertical axis wind mills (e.g., Savonius turbines) are sometimes preferred.^[4] Also, the wind mill needs to be highly durable as marine environments tend to degrade windmills more quickly than what is common on land.^[5]^[6]

Current ships

Few windmill ships have been built to date; these include:^[7]

Jim Bates' Te whaka
Lindsay Olen's Thrippence
Peter Worsley's windmill-driven boat http://www.sailwings.net/rotaryhome.html
Jim Wilkinson's Revelation 2^[8]
Blackbird (wind-powered vehicle)

The film Waterworld starring Kevin Costner featured a trimaran powered by a vertical-axis Darrieus wind turbine.

References

^ Windmill sailboats
^ Windmill powered boats
^ Windmill ship video demonstrating sail points and boat specifics
^ Rotor sails schematic and model boat construction
^ Windmill ship research
^ Vertical axis windmill on windmill boat
^ Current windmill ships
^ "UK | Design puts boat in a spin". BBC News. 2001-08-24. Retrieved 2010-06-16.

[1] Windmill sailboats

[2] Windmill powered boats

[3] Windmill ship video demonstrating sail points and boat specifics

[4] Rotor sails schematic and model boat construction

[5] Windmill ship research

[6] Vertical axis windmill on windmill boat

[7] Current windmill ships

[8] "UK | Design puts boat in a spin". BBC News. 2001-08-24. Retrieved 2010-06-16.

[1]

[2]

[3]

[4]

[5]

[6]

[7]

[8]

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+{{unreliable sources|date=August 2012}}
-{{cleanup}}
+A '''windmill ship''', '''wind energy conversion system ship''' or '''wind energy harvester ship''' propels itself by use of a [[wind turbine]] to drive a [[propeller]].
-{{improve}}
-A '''windmill ship''' is a ship which moves itself by a windmill connected to the propeller. Windmill ships should not be confused with [[rotor ship]]s, as they do not rely on the [[Magnus effect]] for propulsion. Rather, like regular windmills they only use direct wind power.<ref>[http://www.treehugger.com/files/2007/02/windmill_sailbo.php Windmill sailboats]</ref> This direct windpower is mechanically transferred and not electrically (like with windturbines), allowing the force to be transferred to the propeller without conversion losses. In windmill hybrid boats, electrical conversion of the power is nonetheless done when the energy can not be used inmediatelly and needs to be stored.
+They use [[wind power]]<ref>[http://www.treehugger.com/files/2007/02/windmill_sailbo.php Windmill sailboats]</ref> through a mechanical or electrical transmission to the propeller. Where transmission is electric, storage batteries may also be used to allow power generated at one time to be used for propulsion later on.
+Windmill ships should not be confused with [[rotor ship]]s, which instead rely on the [[Magnus effect]] for propulsion.
 ==Points of sail==
-[[Image:Points of sail for windmill ship.JPG|thumb|right|150px]]
-Due to the fact that a windmill can rotate 360°, a windmill ship can <ref>[http://www.boatdesign.net/forums/projects-proposals/windmill-wind-turbine-powered-boats-how-many-out-there-they-viable-14182-4.html Windmill powered boats]</ref><ref>[http://www.youtube.com/watch?v=NNbNNSDljGI Windmill ship video demonstrating sail points and boat specifics]</ref>
+Equipped with a wind conversion device that can rotate 360° no matter in which direction the ship is heading, a windmill ship can sail in any direction.
-==Types==
-[[Image:Windmill (oxy)hydrogen hybrid ship.jpg|thumb|right|150px|A windmill/(oxy)hydrogen hybrid ship]]
+* It can move directly upwind, a point of sailing unachievable by other sailing craft. Here a wind turbine powers a water propeller. Because the power produced depends on the apparent wind strength, a large amount of power is transmitted to the propeller.<ref>[http://www.boatdesign.net/forums/projects-proposals/windmill-wind-turbine-powered-boats-how-many-out-there-they-viable-14182-4.html Windmill powered boats]</ref><ref>[https://www.youtube.com/watch?v=NNbNNSDljGI Windmill ship video demonstrating sail points and boat specifics]</ref> In order to operate efficiently in the typically slow speed through the water, the propeller must be large enough to generate more upwind thrust than the combined downwind force of the wind turbine and the air and water resistances of the ship structure itself.
-Several types can be made; these include windmill-only ships <ref>[http://gcaptain.com/maritime/blog/ocean-kites-top-10-green-ship-designs/ Windmill-only ship image]</ref>, windmill/rotorsail ships<ref>[http://books.google.com/books?id=eAAAAAAAMBAJ&pg=PA70&lpg=PA70&dq=rotor+sail&source=bl&ots=xSUYlMKaNc&sig=9GDzOSzqbYErnJySv1__h4TVxbc&hl=nl&ei=B5WrSqmQB9fajQe9qdj3Bw&sa=X&oi=book_result&ct=result&resnum=7#v=onepage&q=rotor%20sail&f=false Image of windmill/rotor sail hybrid ship]</ref> aswell as hybrid ships which store wind power from the windmill when the ship does not need to be propelled. Often the boats are equipped with low-friction hull designs (eg [[multihull]]s, ...) or they are foreseen of [[hydrofoil]]s, which reduces the energy required to propell the boat. Boats without low-friction hulls or hydrofoils can be equipped with windmills, but often the force generated by the windmills alone is not sufficient to propel the craft. In this case, the windmills only provide [[sail assist|supplemental force]] to the rotors. At present, research is still going on and the best types of bladed rotors still needs to be determined. For example, high horizontal axis wind mills are proven to make the ship less stable. Therefore, vertical axis wind mills (eg Savonius turbines, ...) are sometimes preferred. Also, the wind mill needs to be highly durable as marine environments tend to degrade windmills more quickly than what is common on land. <ref>[http://sciencelinks.jp/j-east/article/200117/000020011701A0501883.php Windmill ship research]</ref><ref>[http://www.bluenergy-ag.net/English/tech_wind.html Vertical axis windmill on windmill boat]</ref>
+* With the wind from the side, i.e. on a reach, the wind turbine's thrust pushes the ship sideways, which should therefor have a lateral surface such as a keel in order to reduce leeway. Thus equipped the wind turbine can be also be used in an autogyro mode. That is, no rotary power is transmitted and the wind turbine acts in the same manner as a static sail and the ships's speed could exceed wind speed in the same way as with many other sailing craft.
+* Sailing downwind, the apparent wind decreases the more the ship speeds up and at exactly the true wind speed, would drop to zero, so that the wind turbine can generate no power and also no thrust if used in the autogyro mode. Therefor windmill ships are limited to less than wind speed when travelling directly downwind, as with other sailing craft. Theoretically the wind turbine could be used instead as an air propeller and the water propeller as a water turbine. The direction of power is then reversed and such a windmill ship could accelerate through the region of zero apparent wind and exceed the wind speed directly downwind. As this requires both the air and water devices to be constructed differently than usual and extremely low water resistance from the hull, this has not been achieved so far with ships, but has been achieved with land yachts. These travel on wheels which offer very little resistance at high speeds compared to that of even the best hulls through water.
+== Types ==
+Several types can be made; these include wind-turbine-only ships as well as hybrid ships which store wind power from the turbine when the ship does not need to be propelled. To reduce the energy required to propel the boat, windmill ships are often equipped with low-friction hull designs, such as [[multihull]]s, or they are [[hydrofoil]]s. Boats without low-friction hulls or hydrofoils can be equipped with wind turbines, but often the force generated by the turbines alone is not sufficient to propel the craft. In this case, the turbines only provide [[sail assist|supplemental force]] to conventional sails or other propulsion systems.
+At present, research is ongoing and the best types of bladed rotors still need to be determined. For example, high horizontal axis windmills are proven to make the ship less stable. Therefore, [[Vertical axis wind turbine|vertical axis wind mills]] (e.g., [[Savonius wind turbine|Savonius turbines]]) are sometimes preferred.<ref>[https://books.google.com/books?id=DuMDAAAAMBAJ&pg=PA124 Rotor sails schematic and model boat construction]</ref> Also, the wind mill needs to be highly durable as marine environments tend to degrade windmills more quickly than what is common on land.<ref>[http://sciencelinks.jp/j-east/article/200117/000020011701A0501883.php Windmill ship research]</ref><ref>[http://www.bluenergy-ag.net/English/tech_wind.html Vertical axis windmill on windmill boat]</ref>
 ==Current ships==
-Few windmill ships have been built to date; these include <ref>[https://secure.seabreeze.com.au/forums/topic.asp?TOPIC_ID=49631 Current windmill ships]</ref>:
+Few windmill ships have been built to date; these include:<ref>[https://secure.seabreeze.com.au/forums/topic.asp?TOPIC_ID=49631 Current windmill ships]</ref>
 * Jim Bates' Te whaka
 * Lindsay Olen's Thrippence
-* Peter Worsley's windmill-driven boat
+* Peter Worsley's windmill-driven boat http://www.sailwings.net/rotaryhome.html
+* Jim Wilkinson's Revelation 2<ref>{{cite web|url=http://news.bbc.co.uk/2/hi/uk_news/1507825.stm |title=UK &#124; Design puts boat in a spin |publisher=BBC News |date=2001-08-24 |accessdate=2010-06-16}}</ref>
-* ?'s Revelation 2
+* [[Blackbird (wind-powered vehicle)|''Blackbird'' (wind-powered vehicle)]]
+The film ''[[Waterworld]]'' starring [[Kevin Costner]] featured a [[trimaran]] powered by a vertical-axis [[Darrieus wind turbine]].
+==See also==
+{{Portal|Renewable energy|Wind power}}
+* [[Wind-powered vehicle]]
 ==References==
-{{reflist}}
+{{Reflist}}
+{{DEFAULTSORT:Windmill Ship}}
+[[Category:Marine propulsion]]
+[[Category:Wind-powered vehicles]]
 [[Category:Boat types]]