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Introduction to New Developments in Wind Power Generation
The Crown Estate, a UK Government body controls the leasing of offshore areas suitable for windfarms. In the recent 3rd round these allocations have all been taken up by offshore windfarm companies.
The leases covered offshore areas from the North of Scotland, right down through the East and West coasts to the South coast of England. These allocations are all a lot further from the shallow waters of the coastline, so the latest technology of supporting the turbines in deep water will be used to install the much larger capacity wind turbines.
This article on renewable energy focuses on what’s new in wind power generation and wind generator research. We begin with an overview of a typical offshore large output wind turbine, followed by an examination of the latest technology used in the design of large capacity wind turbines.
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Overview of Wind Turbine Operation
As I have covered this subject thoroughly in a previous article on Offshore Wind Turbine Operation, I will just give a brief overview of wind turbine operation.
Basically, the turbines consist of a nose cone that houses the blades and a nacelle that houses the rest of the components. The blades drive a gearbox through a high tensile driveshaft, with the generator being driven by the output shaft from the gearbox.
Instruments on the nacelle tail transmit wind conditions to a controller which adjusts the yaw and blade pitch to suit the wind conditions, and the output power cable is run down the inside of the tower, and down into the seabed, from here it is joined to the other turbine cables. The main electrical cable is buried in the seabed silt and sand, making a landfall as close as possible to an onshore substation, and connected to the national grid. New Power transmission technology in the form of High Voltage Direct Current (HVDC) Substations has been successfully used offshore. The transmission of HVDC current as opposed to HVAC current is more efficient, with less loss of transmission power.
Some turbines are direct drive eliminating the need for a gearbox, but as we know, because the revolutions from the gearbox output are high, the physical size of the generator can be relatively small. Therefore a direct drive turbine would require a much larger generator (up to 12 feet diameter) because of the blade speed being transmitted to the generator being less than 20 RPM. However, Siemens have developed a new type of direct drive generator which operates on permanent magnets, which will operate at blade speed, and this will be examined in the next section.
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Latest Developments in Offshore Wind Turbines
Siemens have developed a 3MW wind turbine that is much lighter than a conventional one.
Their new turbine incorporates permanent magnets in the turbine generator, reducing the dimensions and weight of the generator and this combined with the elimination of a gearbox, is where the weight loss occurs.
The first prototype was installed in Denmark last year (2009)
Reference Web: Siemens - Direct drive turbines.
- General Electric
General Electric is currently developing a 4MW wind turbine model that should be in production by 2012 for use in offshore windfarms.
This new turbine will be 25% more efficient than a conventional 4MW turbine due to the innovative design of the blades coupled with a very efficient drive chain mechanism.
The new turbine will stand 300 feet high with a blade diameter of 360 feet.
Reference Web: GE - A very efficient 4MW offshore turbine from General electric.
Please see page 2 for types and sketches of floating support structures proposed for offshore wind turbines.
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Environmental Impact Assessment of Offshore Wind Farms There is a requirement by most governments for an offshore wind operator to carry out an environmental impact assessment of offshore wind farms. This is applicable to turbines mounted on a fixed bottom support or floating offshore wind turbine. The environmental impact assessment of offshore wind can take anything up to two years to complete and be accepted. It comprises of a technical review of the installation procedure, including the load-out barges number of heavy lifts, and the type of turbine support structure. Equally importantly the assessment includes an in-depth survey of the local marine life, their numbers, species and habitats along with the associated flora such as algae and other seaweeds. Finally the assessment must include a decommissioning procedure; how the whole unit is dismantled and shipped ashore at end of its useful life.
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Offshore Structures Used to Support Large Capacity Wind Turbines - Latest Technology
Currently the offshore windfarms are restricted mainly to operating in depths of 65 feet, due to the expense of utilizing the fixed steel platforms as used in the offshore oil and gas industry.
However, various offshore windfarm installation companies have recently procured leases to deep-water locations of 120 miles of the British coast. These locations vary in depths from 150 feet to 240 and the companies propose to use floating structures similar to the semisubmersible drilling rigs used offshore as well as modified steel jacket-type structures.
Reference Web: Floating Wind Turbines - deep water wind turbine floating supports structures.
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The latest Offshore Wind Turbine Development Projects
Last year two large capacity 5MW wind turbines were installed and are operating in deep water alongside the Beatrice oil and gas field in the Outer Moray Firth. These are currently the largest capacity wind turbines to be installed anywhere in the world and supply power at 33kV to the Beatrice Field Oil Production Platforms.
This field was unique for a number of reasons:
- First windfarm to participate in Distant Offshore Windfarms with no Visual Impact in Deepwaters ( DOWNVInD)
- The use of the world’s biggest wind turbine (5MW) in an offshore windfarm.
- Installing the turbines in 45m of water using a steel jacket structure for the first time.
- Assembly of all components ashore and floating out complete unit for installation to the offshore structure in one single lift operation.
Reference Web: Beatrice - largest wind turbines in operation
However, the latest round of Crown Estate offshore seabed leasing for wind turbine farms has enabled numerous UK companies to take up the offered leases. Among them are the following companies, some of whom have just been formed or amalgamated:
- Beatrice Offshore Windfarm.
SeaEnergy PLC (formerly Ramco Energy PLC), a New Scottish Offshore Renewable Energy Company, have recently announced their plans to develop a 920MW windfarm, under the name of Beatrice Offshore Windfarm that will be located adjacent to the two Beatrice demonstrator turbines in the Outer Morayfirth.
The windfarm will consist of 184 wind turbines of 5MW capacity that will be supported on conventional offshore oil platform steel jackets, piled into the ocean bed.
- Inch Cape Offshore Wind Farm
SeaEnergy have also applied to lease an area 10 miles of the East Coast of Scotland in the outer Tay Estuary.
This will be known as the Inch Cape Offshore Wind Farm and will have an output of 905MW from 181 wind turbines of 5MW capacity.
Both these fields will be subject to a Strategic Environmental Assessment (“SEA”), along with an environmental survey of local marine flora and fauna and an Environmental Impact Statement, which will take up to two years to complete.
Venture between Mitsubishi/Scottish and Southern Energy (SSE)
A newly formed Scottish venture between Mitsubishi and Scottish and Southern Energy (SSE) has led to the signing of an agreement to explore the range of offshore wind farms technology, along with carbon abatement and sequestration technology.
Mitsubishi, the giant electrical company, has just joined the offshore wind power companies in February this year, the Scottish government having invested £130,000,000 ($202,000,000) in the new technology ventures.
Reference Web: Mitsubishi - Offshore windfarm development venture between Mitsubishi and Scottish and Southern Energy
The company Able UK has announced £400,000,000 ($620,000,000) to build a Marine Energy Park on the Humber.
This will entail the construction of a tailor-made quayside facility for the construction, installation, and delivery of offshore wind turbines. The quays will be 1,630m long and have been developed in conjunction with major offshore wind companies who will hope to construct, ship and install 5000 wind turbines to Dogger, Hornsea, and Norfolk Bank by 2020, so the facility will be busy!
There are also plans to build a biomass plant at the Marine Energy Park to the latest technology, and during construction and operation the park will give a massive employment boost to people of the area.
Reference Web: Humber Park - Marine Energy Park.