Laddermill
Encyclopedia
A Laddermill is a hypothetical airborne wind turbine
consisting of a long string or loop of power kite
s.
The loop or string of kites (the "ladder") would be launched in the air by the lifting force of the kites, until it is fully unrolled, and the top reaches a height determined by designers and operators; some designers have considered heights of about 30,000 feet (9144 meters), but the concept is not height-dependent. The laddermill method may use one endless loop, two-endless loops, or more such loops.
is one of the fastest-growing power sources in the world. The bulk of this growth has been in the form of conventional, three-bladed, horizontal-axis wind turbine
s, with vertical axis wind turbine
s accounting for a small remainder. Converting the kinetic energy of the wind into useful electricity requires converting the linear horizontal motion of wind into the rotational motion of a shaft in an electrical generator
. In every case this requires some method of maintaining a static force against the motion of the wind, to keep the wind-collection apparatus from simply blowing away. Conventional wind turbines accomplish this by mounting rotors rigidly on towers, relatively close to the ground. This arrangement works reliably, but is relatively expensive, requires large amounts of structural material, and cannot tap the much stronger winds often present at higher altitudes.
Humans have flown kites for thousands of years. Kites can readily fly to great heights. Over the years this has led several inventors to propose various schemes for using kites to convert the linear horizontal motion of wind into rotational motion which can drive an electrical generator. As of 2008, few such schemes have even reached the working prototype stage, and none have reached commercial operation. However, progress in enabling technologies such as the computer control of power kite
s may someday lead to practical airborne wind turbines of the aerodynamic variety.
In a 2007 "road map" report on renewable energy adopted by the European Parliament
, laddermill technology was listed among various "promising and challenging" new energy sources into which revenue from emissions trading
could be reinvested. http://www.euractiv.com/en/energy/renewables-parliament-wants-binding-sectoral-targets/article-167085
A "rotating loop" "LadderMill" project is designed and developed by the Dutch ex astronaut
and Physicist
Wubbo Ockels
.
As quoted from his website:http://www.ockels.nl/
Airborne wind turbine
An airborne wind turbine is a design concept for a wind turbine that is supported in the air without a tower. Airborne wind turbines may operate in low or high altitudes; they are part of a wider class of airborne wind energy systems addressed by high-altitude wind power...
consisting of a long string or loop of power kite
Power kite
A power kite or traction kite is a large kite designed to provide significant pull to the user.They come in three main forms: foils, leading edge inflatables and supported leading edge. There are also rigid-framed kites and soft single skin kites. There are several different control systems used...
s.
The loop or string of kites (the "ladder") would be launched in the air by the lifting force of the kites, until it is fully unrolled, and the top reaches a height determined by designers and operators; some designers have considered heights of about 30,000 feet (9144 meters), but the concept is not height-dependent. The laddermill method may use one endless loop, two-endless loops, or more such loops.
Introduction
As of 2008, wind powerWind 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....
is one of the fastest-growing power sources in the world. The bulk of this growth has been in the form of conventional, three-bladed, horizontal-axis wind turbine
Wind turbine
A wind turbine is a device that converts kinetic energy from the wind into mechanical energy. If the mechanical energy is used to produce electricity, the device may be called a wind generator or wind charger. If the mechanical energy is used to drive machinery, such as for grinding grain or...
s, with vertical axis wind turbine
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...
s accounting for a small remainder. Converting the kinetic energy of the wind into useful electricity requires converting the linear horizontal motion of wind into the rotational motion of a shaft in an electrical generator
Electrical generator
In electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. A generator forces electric charge to flow through an external electrical circuit. It is analogous to a water pump, which causes water to flow...
. In every case this requires some method of maintaining a static force against the motion of the wind, to keep the wind-collection apparatus from simply blowing away. Conventional wind turbines accomplish this by mounting rotors rigidly on towers, relatively close to the ground. This arrangement works reliably, but is relatively expensive, requires large amounts of structural material, and cannot tap the much stronger winds often present at higher altitudes.
Humans have flown kites for thousands of years. Kites can readily fly to great heights. Over the years this has led several inventors to propose various schemes for using kites to convert the linear horizontal motion of wind into rotational motion which can drive an electrical generator. As of 2008, few such schemes have even reached the working prototype stage, and none have reached commercial operation. However, progress in enabling technologies such as the computer control of power kite
Power kite
A power kite or traction kite is a large kite designed to provide significant pull to the user.They come in three main forms: foils, leading edge inflatables and supported leading edge. There are also rigid-framed kites and soft single skin kites. There are several different control systems used...
s may someday lead to practical airborne wind turbines of the aerodynamic variety.
In a 2007 "road map" report on renewable energy adopted by the European Parliament
European Parliament
The European Parliament is the directly elected parliamentary institution of the European Union . Together with the Council of the European Union and the Commission, it exercises the legislative function of the EU and it has been described as one of the most powerful legislatures in the world...
, laddermill technology was listed among various "promising and challenging" new energy sources into which revenue from emissions trading
Emissions trading
Emissions trading is a market-based approach used to control pollution by providing economic incentives for achieving reductions in the emissions of pollutants....
could be reinvested. http://www.euractiv.com/en/energy/renewables-parliament-wants-binding-sectoral-targets/article-167085
Operating modes
There are currently two operating modes considered:- The kites pull up the long string on which they are tethered, and the resulting energy is then used to drive an electric generator. When the end of the string is reached the pull force of the kites is reduced by changing the angle of attackAngle of attackAngle of attack is a term used in fluid dynamics to describe the angle between a reference line on a lifting body and the vector representing the relative motion between the lifting body and the fluid through which it is moving...
of the kites "wing shape", and the string is then rewound with the electric generator acting as a motor, or by other means. If the string is reduced to its minimum length the next energy generating cycle is started by restoring the angle of attack of the kites to maximum lift. - Kites on one side of a wire loop generate lift while the ones on the other side do not because the angle of attack of the kites "wing shape" changes when the kite passes the top of the loop. So the kites pull up only one end of an endless loop, causing the loop to start to rotate, and the resulting released energy is then used to drive an electric generator.
A "rotating loop" "LadderMill" project is designed and developed by the Dutch ex astronaut
Astronaut
An astronaut or cosmonaut is a person trained by a human spaceflight program to command, pilot, or serve as a crew member of a spacecraft....
and Physicist
Physicist
A physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter is made to the behavior of the material Universe as a whole...
Wubbo Ockels
Wubbo Ockels
Prof. Dr. Wubbo Johannes Ockels is a Dutch physicist and a former ESA astronaut. In 1985 he participated in a flight on a space shuttle , making him the first Dutch citizen in space. He was not the first Dutch-born astronaut, as he is preceded by the naturalized American Lodewijk van den Berg, who...
.
As quoted from his website:http://www.ockels.nl/
The LadderMill is the response to the challenge for exploiting the gigantic energy source contained in the airspace up to high altitudes of 10 km. The concept has been developed with the aim to convert wind energy at altitude in electricity on the ground in an environmental and cost effective manner.
Timeline
- 1977 April 3, 1977, invention declared. On September 21, 1979, Douglas Selsam notarized his kite-lifted endless chain of airfoils HAWP system, generic type that would later show in Dutch astronaut Wubbo Ockels' device called LadderMill described in a patent of 1997. Douglas Selsam conceived his Auto-oriented Wind Harnessing Buoyant Aerial Tramway on April 3, 1977. On the Selsam notarized disclosure of invention was placed a date of Sept. 20, while the notary placed the final signing on Sept. 21, 1979. notes and drawings.
External links
- The laddermill website of Wubbo Ockels.
- Website of the Delft University of TechnologyDelft University of TechnologyDelft University of Technology , also known as TU Delft, is the largest and oldest Dutch public technical university, located in Delft, Netherlands...
explaining the principle of the LadderMill project. - paper "Design and Construction of a 4 kW Groundstation for the Laddermill".
- Giant kites to tap power of the high wind Alok Jha, The Guardian, Sunday August 3, 2008