Windmill ship
Encyclopedia
A windmill ship, wind energy conversion system ship or wind energy harvester ship propels itself by use of a windmill
to drive a propeller
.
They use wind power
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, as they do not rely on the Magnus effect
for propulsion.
s, or they are hydrofoil
s. 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 supplemental force to conventional sails or other propulsion systems.
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
(e.g. 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.
Windmill
A windmill is a machine which converts the energy of wind into rotational energy by means of vanes called sails or blades. Originally windmills were developed for milling grain for food production. In the course of history the windmill was adapted to many other industrial uses. An important...
to drive a propeller
Propeller
A propeller is a type of fan that transmits power by converting rotational motion into thrust. A pressure difference is produced between the forward and rear surfaces of the airfoil-shaped blade, and a fluid is accelerated behind the blade. Propeller dynamics can be modeled by both Bernoulli's...
.
They use wind power
Wind power
Wind power is the conversion of wind energy into a useful form of energy, such as using wind turbines to make electricity, windmills for mechanical power, windpumps for water pumping or drainage, or sails to propel ships....
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, as they do not rely on the Magnus effect
Magnus effect
The Magnus effect is the phenomenon whereby a spinning object flying in a fluid creates a whirlpool of fluid around itself, and experiences a force perpendicular to the line of motion...
for propulsion.
Points of sail
Because a windmill can rotate 360° into the wind, no matter what direction the ship is facing, a windmill ship can sail in any direction. In fact, because the power produced depends almost entirely on the apparent wind, they can produce the most power sailing directly upwind Conventional sailing vessels are restricted to sailing downwind, or with limited ability to sail upwind according to the design of their sails.Types
Several types can be made; these include windmill-only ships as well as hybrid ships which store wind power from the windmill 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 multihullMultihull
A multihull is a ship, vessel, craft or boat with more than one hull.-Description:Multihulls include: Proas, which have two differently shaped or sized hulls with lateral symmetry; catamarans, which have two hulls with longitudinal symmetry; and trimarans, which have a main hull in the center and...
s, or they are hydrofoil
Hydrofoil
A hydrofoil is a foil which operates in water. They are similar in appearance and purpose to airfoils.Hydrofoils can be artificial, such as the rudder or keel on a boat, the diving planes on a submarine, a surfboard fin, or occur naturally, as with fish fins, the flippers of aquatic mammals, the...
s. 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 supplemental force to conventional sails or other propulsion systems.
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
Vertical axis wind turbine
Vertical-axis wind turbines are a type of wind turbine where the main rotor shaft is set vertically and the main components are located at the base of the turbine...
(e.g. Savonius turbines
Savonius wind turbine
Savonius wind turbines are a type of vertical-axis wind turbine , used for converting the force of the wind into torque on a rotating shaft...
) 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.
Current ships
Few windmill ships have been built to date; these include:- Jim Bates' Te whaka
- Lindsay Olen's Thrippence
- Peter Worsley's windmill-driven boat
- Jim Wilkinson's Revelation 2