Salter's duck
Encyclopedia
Salter's duck, also known as the nodding duck or by its official name the Edinburgh duck, is a device that converts wave power
into electricity. The wave impact induces rotation of gyroscope
s located inside a pear-shaped "duck", and an electrical generator
converts this rotation into electricity with an overall efficiency of up to 90%. The Salter's duck was invented by Stephen Salter
in response to the oil shortage in the 1970s and was one of the earliest generator designs proposed to the Wave Energy program in the United Kingdom
. The funding for the project was cut off in the early 1980s after oil prices rebounded and the UK government moved away from alternative energy sources. Upon its return to the venue in the early 2000s, Salter's duck has since gone into production and use.
, Salter set about creating a source of alternative energy
. The idea for creating Salter's duck came about from his studies on a lavatory cistern while at Edinburgh University. He invented Salter's duck in 1974 and attempted to make it the main device of choice for the Wave Energy program in the United Kingdom
. A prototype attempt to use the device was constructed in 1976 off Dores Beach
. It was to be used to "provide some 20 kw of power". It was modified slightly from the original design and Coventry University, which helped with the design, went on to utilize a separate type that was called the Sea Clam.
However, because of the 1980s oil glut
, the perceived need for immediate alternative energy sources declined and, in 1982, the Wave Energy program was disbanded. This ended the hope of having Salter's duck become a mainstay in the alternative energy campaign. After later investigation, it was discovered that the Energy Technology Support Unit's cost determinations had mis-estimated the cost of building Salter's duck by more than double the actual cost. The Energy Technology Support Unit was set up in 1974 as an agency on behalf of the Department of Energy; though its function was to manage research programmes on renewable energy
and energy conservation, it was operated by the United Kingdom Atomic Energy Authority
. Cost considerations based on the findings were among the main factors in the duck's not being put into widespread production under the Wave Energy program in the late 1970s. The other major factor was that a consulting firm tasked with distributing government grants passed over the 9.5 million pounds that had been allocated to Salter's research and the improvement of Salter's duck, so the funds were never actually granted to Salter and his group. From this revelation and with the increase in research into alternative energy in the 2000s, Salter's duck has begun to be used as a part of wave energy research in the United Kingdom.
, with materials from Ready Made Concrete and Insituform. The final design worked by having 20 to 30 ducks connected together by the jointed spine, with each duck moving with the waves that hit it and transferring the energy of the impact to "six to ten pumps" for each duck. The pear shape of the ducks have them facing the waves due to the decided orientation of their spine so that they rock and turn over when a wave hits them. This causes four gyroscopes inside to move back and forth, creating hydraulic energy that is transferred to a turbine or generator.
The use of a lowercase r in this formula indicates the back radius of the ducks. They also had to test for the incidence energy (R) given off by a submerged surface (s), the formula of which is,
In this formula, the v stands for body velocity and the u for unperturbed fluid velocity perpendicular to the surface. With this, they were able to then use the final formula that tested for the absorption efficiency, eta
(n),
The use of these three formulas allowed Swift-Hook to determine that Salter's duck is able to convert "90% of the wave energy into mechanical energy". However, this percentage was when the duck was tested in a laboratory. In varying types of realistic conditions, the efficiency of the duck varies wildly and often drops to around 50%, as ducks are more often used in rough weather in order to convert enough wave power. Conversely, ducks are not useful in calm weather, as the waves would not have enough energy for there to be any efficiency in converting it.
Wave power
Wave power is the transport of energy by ocean surface waves, and the capture of that energy to do useful work — for example, electricity generation, water desalination, or the pumping of water...
into electricity. The wave impact induces rotation of gyroscope
Gyroscope
A gyroscope is a device for measuring or maintaining orientation, based on the principles of angular momentum. In essence, a mechanical gyroscope is a spinning wheel or disk whose axle is free to take any orientation...
s located inside a pear-shaped "duck", and 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...
converts this rotation into electricity with an overall efficiency of up to 90%. The Salter's duck was invented by Stephen Salter
Stephen Salter
Stephen Hugh Salter is Emeritus Professor of Engineering Design at the University of Edinburgh and inventor of the eponymous Salter duck wave energy device...
in response to the oil shortage in the 1970s and was one of the earliest generator designs proposed to the Wave Energy program in the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
. The funding for the project was cut off in the early 1980s after oil prices rebounded and the UK government moved away from alternative energy sources. Upon its return to the venue in the early 2000s, Salter's duck has since gone into production and use.
History
As a result of the 1973 oil crisis1973 oil crisis
The 1973 oil crisis started in October 1973, when the members of Organization of Arab Petroleum Exporting Countries or the OAPEC proclaimed an oil embargo. This was "in response to the U.S. decision to re-supply the Israeli military" during the Yom Kippur war. It lasted until March 1974. With the...
, Salter set about creating a source of alternative energy
Alternative energy
Alternative energy is an umbrella term that refers to any source of usable energy intended to replace fuel sources without the undesired consequences of the replaced fuels....
. The idea for creating Salter's duck came about from his studies on a lavatory cistern while at Edinburgh University. He invented Salter's duck in 1974 and attempted to make it the main device of choice for the Wave Energy program in the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
. A prototype attempt to use the device was constructed in 1976 off Dores Beach
Dores
Dores is a village located on the south shore of Loch Ness, 10 km south west of the city of Inverness, in the Highland council area of Scotland.The annual RockNess music festival takes place in fields to the north of the village....
. It was to be used to "provide some 20 kw of power". It was modified slightly from the original design and Coventry University, which helped with the design, went on to utilize a separate type that was called the Sea Clam.
However, because of the 1980s oil glut
1980s oil glut
The 1980s oil glut was a serious surplus of crude oil caused by falling demand following the 1970s Energy Crisis. The world price of oil, which had peaked in 1980 at over US$35 per barrel , fell in 1986 from $27 to below $10...
, the perceived need for immediate alternative energy sources declined and, in 1982, the Wave Energy program was disbanded. This ended the hope of having Salter's duck become a mainstay in the alternative energy campaign. After later investigation, it was discovered that the Energy Technology Support Unit's cost determinations had mis-estimated the cost of building Salter's duck by more than double the actual cost. The Energy Technology Support Unit was set up in 1974 as an agency on behalf of the Department of Energy; though its function was to manage research programmes on renewable energy
Renewable energy
Renewable energy is energy which comes from natural resources such as sunlight, wind, rain, tides, and geothermal heat, which are renewable . About 16% of global final energy consumption comes from renewables, with 10% coming from traditional biomass, which is mainly used for heating, and 3.4% from...
and energy conservation, it was operated by the United Kingdom Atomic Energy Authority
United Kingdom Atomic Energy Authority
The United Kingdom Atomic Energy Authority is a UK government research organisation responsible for the development of nuclear fusion power. It is an executive non-departmental public body of the Department for Business, Innovation and Skills and was formerly chaired by Lady Barbara Judge CBE...
. Cost considerations based on the findings were among the main factors in the duck's not being put into widespread production under the Wave Energy program in the late 1970s. The other major factor was that a consulting firm tasked with distributing government grants passed over the 9.5 million pounds that had been allocated to Salter's research and the improvement of Salter's duck, so the funds were never actually granted to Salter and his group. From this revelation and with the increase in research into alternative energy in the 2000s, Salter's duck has begun to be used as a part of wave energy research in the United Kingdom.
Design
The original prototype of Salter's duck was made of "a string of floating vanes of rudimentary duck cross-sections linked through a central spine". The string itself had 12 ducks attached to it that were "50 cm wide mounted on a spine 27 cm in diameter and 6 m long." It was made at Coventry UniversityCoventry University
Coventry University is a post-1992 university in Coventry, West Midlands, England. Under the terms of the Further and Higher Education Act of 1992, the institution's name was changed from Coventry Polytechnic to Coventry University...
, with materials from Ready Made Concrete and Insituform. The final design worked by having 20 to 30 ducks connected together by the jointed spine, with each duck moving with the waves that hit it and transferring the energy of the impact to "six to ten pumps" for each duck. The pear shape of the ducks have them facing the waves due to the decided orientation of their spine so that they rock and turn over when a wave hits them. This causes four gyroscopes inside to move back and forth, creating hydraulic energy that is transferred to a turbine or generator.
Energy efficiency
In order to determine the efficiency of energy output from Salter's duck, in 1975, scientist Swift-Hook and others ran a series of tests. The optimum range of the ducks was determined according to the formula,The use of a lowercase r in this formula indicates the back radius of the ducks. They also had to test for the incidence energy (R) given off by a submerged surface (s), the formula of which is,
In this formula, the v stands for body velocity and the u for unperturbed fluid velocity perpendicular to the surface. With this, they were able to then use the final formula that tested for the absorption efficiency, eta
ETA
ETA , an acronym for Euskadi Ta Askatasuna is an armed Basque nationalist and separatist organization. The group was founded in 1959 and has since evolved from a group promoting traditional Basque culture to a paramilitary group with the goal of gaining independence for the Greater Basque Country...
(n),
The use of these three formulas allowed Swift-Hook to determine that Salter's duck is able to convert "90% of the wave energy into mechanical energy". However, this percentage was when the duck was tested in a laboratory. In varying types of realistic conditions, the efficiency of the duck varies wildly and often drops to around 50%, as ducks are more often used in rough weather in order to convert enough wave power. Conversely, ducks are not useful in calm weather, as the waves would not have enough energy for there to be any efficiency in converting it.