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The Manchester Bobber’s inventive features utilise the rise and fall (or ‘bobbing’) of the water surface. This movement transmits energy, which is then extracted by the power take-off unit to drive a generator and produce energy. Although harnessing the energy from the bobbing motion of the sea is not a new idea, the Manchester Bobber is particularly innovative because it is the hydrodynamics of the float employed by the Manchester Bobber that provides the vital connection to generating electricity. The vision is to have an array of Bobbers working together to generate electricity.
: "Energy from the sea may be extracted in many ways and harnessing the energy from the bobbing motion of the sea is not a new idea. It is the hydrodynamics of the float employed by the Manchester Bobber that provides the vital connection to generating electricity." -- Peter Stanby
The major components and the principle of operation are shown where, for clarity, the components are not drawn to the same relative scale. A floating mass rises and falls under the action of waves in the water and this causes a pulley and its shaft to oscillate. A counterweight controls tension in the suspending medium over the pulley and the pulley shaft is connected to an output shaft through a freewheel clutch. As the float descends, the pulley speed attempts to exceed the output speed causing the clutch to engage and accelerating the entire shaft system. At maximum speed the clutch disengages, allowing the output shaft to continue its forward rotation whilst the pulley decelerates and reverses during ascent of the float. Whilst the clutch is disengaged, the output shaft continues to rotate due to the inertia of a flywheel but decelerates due to energy extraction (i.e. the power output). A gearbox is used to increase the output shaft speed hence reducing the size of flywheel and generator required to produce a given output power. The generator will be a conventional robust induction machine operating at varying speeds and interfaced to the grid through well developed solid-state power conditioning equipment.
All Energy Conference - Gavin Harper Discusses Tidal Power with attendees of the All Energy Conference in Aberdeen Scotland Start the Machester Bobber Interview at .54 Minutes. (YouTube Aug 19, 2007)
The commercial vision is to deploy a number of platforms, each of which supports a closely spaced array of bobbing floats (between 25 and 50) that generate electricity through independent generators. Each of the generators will be rated at 500kW so a platform will be rated at approximately 12MW and will provide an average annual output of 4MW. Initially, platforms will be deployed in water depths of between 20 to 40 metres. Commercialisation of the technology is being driven by the Manchester Bobber Company Ltd and nine industrial partners.
Phase 3 has two parallel streams (3a and 3b). The Manchester Bobber team has secured grant funding for phase 3a (1:70th array optimisation and modelling) and is now in the process of seeking funds and industrial support for Phase 3b of the commercial development.
Phase 3a focuses on optimising and refining the design team's understanding of how bobbers interact when installed in a closely spaced array. Experimental studies have been conducted at 1:70th scale to measure the response and power capture of each float within an array due to a range of incident waves. Measurements indicate that the average response and output of each float is sensitive to its position within the array indicating that interactions are significant. Although interactions reduce the output of some Bobbers, the output of other floats is increased. Significantly, the net output from an array is often greater than the net output from the same number of bobbers in isolation. Further studies are in progress to optimise net output, confirm these array interaction findings at larger scale and assess design loads and stresses. Tests in severe seas and extreme waves have led to the evolution of a patented float design which extends the operational range of the Bobber and improves survivability. These findings feed directly into the partner companies' design for a fall scale prototype.
Phase 3b aims to bring together a consortium of industrial partners with the relevant expertise and commercial funding partners with the commitment to undertake full scale prototype testing. A team of nine industrial partners has been developed each with complementary expertise. This partnership forms the foundations for future commercialisation of the technology and rewards early industrial sponsors with exclusivity during future commercialisation contracts. The purpose of phase 3b is to:
Design and fabricate a full scale float and full scale drive train
Deploy the float and drivetrain in open sea conditions
Test in open sea conditions
Develop designs for commercial deployments
Phase 2 the second tranche of Carbon Trust funding has enabled the Manchester Bobber partners to carry out a 6 month programme of work:
Design, manufacture and test a 1/10th scale model of the Manchester Bobber (NaREC- Blyth during Sept. ‘05)
Design and cost conceptual designs (fixed bed and floating) for a full scale array platform. Work carried out by Royal Haskoning and Carillion (formerly Mowlem plc), respectively.
Determine projected costs for the generation of electricity via a full scale array.
Further development and validation of the computational model including random and regular wave patterns.
Outputs from Phase 2
Predictable scale up from 100th to 10th scale
Refined computational model
Based on full scale platform design cost estimates and extrapolated modelling of the bobbers electrical outputs using the refined computational model gives confidence in a cost competitive technology
Predicted average output of a full scale bobber is very encouraging
1. Cost estimates (±20%) includes platform fabrication, 25 floats, drive train, installation, decommission, foundation prep, soil investigation, planning consent, licenses.
2. Cost estimates do not take into account friction losses in present design or economies of scale.
Phase 1 the initial testing of the wave energy device commenced in Jan.’04 with a 12 month Carbon Trust award. Design, development and testing of a 1/100th scale working device in parallel with the development of a computational model were successfully completed. At the same time UMIP implemented protection of the intellectual property and assisted in a second round of Carbon Trust funding. This has subsequently been awarded in collaboration with project partners Mowlem plc (acquired by Carillion) and Royal Haskoning. Work commences on the 6 month phase 2 from June’05.
The major innovative and attractive features of the system are:
Power output can be constant over a wave cycle as a result of the energy storing properties of the simple, low-technology flywheel. No other cost effective and reliable alternative exists for smoothing the high power outputs that occur due to irregular wave loading.
An array of floats will be disposed on a common platform. Each float will have an independent power take-off hence, whilst one drive is being serviced the remaining floats in the array will continue to supply electricity to the grid.
Safe mode is achieved in extreme conditions (>10m significant wave height) via the ability to rapidly flood each float to achieve total submersion and allow the float to rest safely on the sea bed.
Only the passive and inert float comes into contact with the water. All vulnerable mechanical and electrical components are housed in a protected environment above the crest of storm waves.
All mechanical and electrical components are available from well- established suppliers and require minimal development.
High reliability is expected due to the track-record of component developers and the above-sea location of the drivetrain. In particular, unlike many wave schemes, the design does not incorporate novel components and does not require immersion of critical components.
Device will respond to waves from any direction with minimal adjustment. However, net output will change depending on wave direction and depending on the spread of the wave field.
Maintenance and/or repair is greatly eased by the accessibility of components.
(a) Resonance can be used successfully to enhance the heaving motion. The float will have a natural resonant bobbing (heaving) frequency which will be designed, through choice of mass and shape, to suit the prevailing wave climate and so improve the energy capture characteristics. A patented design enables efficient adjustment of individual float response and allows operation to continue during relatively severe wave conditions.
(b) A computer simulation has been developed which gives very good agreement with observed behaviour when the system is delivering an output power. The simulation has been verified by tests on 1/100th and 1/10th scale prototypes indicating that the hydrodynamics and mechanical dynamics are understood and can be satisfactorily modelled.
(c) A method of guidance of the float has been devised that maintains stable vertical oscillation of the float without rubbing or rolling contacts. This is a low cost system which also reduces structural loading.
(d) Optimum design of float shape and system masses is being refined with funding in place.
(e) Power capability is proportional to approximately the cube of the float dimension but a limit is imposed by typical wave characteristics. A full scale platform will support an array of 25 floats and their power-take-off trains, each with a rating of 500kW so that the platform will act as an offshore power station with a total rating of over 12.5MW. Modelling predicts that the annual average from such a platform will be greater than about 5MW.
Offshore Power Generation.
John Loughhead, Executive Director, UK Energy Research Centre: John Loughhead’s professional career has been predominantly in industrial research and development for the electronics and electrical power industries, including advanced, high power industrial gas turbines, new energy conversion systems, spacecraft thermal management, electrical and materials development for electricity generation and transmission equipment, and electronic control systems.
Nick Jenkins, Professor of Electrical Energy and Power Systems: Nick Jenkins joined the University of Manchester in 1992 and was appointed Professor of Electrical Energy and Power Systems in 1998. His previous career included 14 years industrial experience, of which 5 years were in developing countries. He has worked for Wind Energy Group, BP Solar and Ewbank and Partners on both conventional and renewable power systems. His present research interests include renewable energy, distributed generation and high power electronic systems.
Peter Stansby: Peter Stansby’s research interests involve the development of a coastal processes simulator. Environmental flows: tidal flows pollution dispersion sediment transport. Coastal hydrodynamics: wave mechanics surf zone processes flooding. Shallow-water hydrodynamics: numerical model development flooding dam breaks. Offshore hydrodynamics: wave forces flow-induced vibrations slam forces. Numerical modelling and experimental verification of above areas.
UMIP: Manchester Bobber Gains National Recognition -The Bobber Company Ltd and its wave power generator, Manchester Bobber, were announced joint winners of the Marine Energy Award at the 2007 Rushlight Awards. (Trading Markets Dec. 11, 2007)
Bobbing - The Manchester (UK) Bobber, a patented new wave energy device, passed Phase One in January 2005, testing of 1/100th scale working model. The commercial vision is to deploy a number of platforms, each of which supports a closely spaced array of bobbing floats (between 25 and 50) that generate electricity through independent generators. Each of the generators will be rated at 500kW so a platform will be rated at approximately 12MW and will provide an average annual output of 4MW. (PESN Oct. 6, 2005)
Unique Manchester - The Manchester Bobber project, which has received Carbon Trust funding, was showcased at the New & Renewable Energy Centre (NaREC) in Blyth, Northumberland, last month (September). The design, development and testing of the device has been carried out at the university led by Professor Peter Stansby and Dr Alan Williamson. (4ecotips Oct 6, 2005)
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