Archive for May 2011
Islay’s LIMPET – generating electricity for the grid for over ten years
Wavepower is usually regarded as an infant, experimental technology yet on the island of Islay a shoreline wave energy converter has been generating power for the national grid since 2000. The Limpet (Land Installed Marine Powered Energy Transformer) uses an oscillating water column technology developed by Inverness-based developers Wavegen, a subsidiary of Voith Hydro.
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How an oscillating water column device works
The wave surge forces water into a chamber, where the oscillating water column created by the waves compresses the air column above it, causing rushes of air to be drive through the turbine.
The basic components of an OWC are no more than a chamber vented to the atmosphere and a turbine connected to a generator; the animation on the right shows these components in action:
The chamber of the LIMPET is an inclined concrete tube with its opening below the water level. As external wave action causes the water level in the chamber to oscillate, the variation in water level alternately compresses and decompresses the trapped air above, causing air to flow backwards and forwards through a pair of contra-rotating turbines.
Islay’s LIMPET is the world’s first commercial wave power device to be connected to the UK National Grid. Built in 2000, it is located at Claddach Farm on the Rhinns of Islay. The device was developed by Wavegen in cooperation with Queen’s University Belfast. The capacity of LIMPET is 500 kW. Availability levels now match other, more established renewables, and even traditional power plants, with 2010 figures running at 98%. The plant has accumulated over 60,000 grid connected generating hours, providing a wealth of data to optimise plant performance, and giving clients enormous confidence in long term reliability.
New undersea cables needed to get the power to the people!
The further North and West you go the more powerful the forces of wind and sea become round Scotland’s shores, with massive wind and wave resources available in the Western Isles and Shetland. The amount of power available is vastly greater than is required by these island communities, so where will it go? There is no way of delivering that power to the national grid until new high-voltage undersea cables (usually referrred to as interconnectors) are laid and installed.
The need for an interconnector to the Western Isles first arose when the giant Lewis windfarm was in the throes of the planning process back in 2004. The application was eventually rejected on environmental grounds in April 2008, and since then the interconnector has only been mentioned occasionally in passing. Now that a seabed lease has been granted for Aquamarine Power’s proposed wavepower project West of Lewis a new grid link to the mainland has once again become a priority.
In Shetland a new interconnector is a vital component in Viking Energy’s plans for a huge windfarm on the Shetland mainland. Sustainable Shetland are the main objectors to the interconnector, but by their own admission they object to the proposal because it is an integral part of the Viking Energy scheme. In practice a new interconnector woudl not be solely for the benefit of Viking, it woudl allow other renewable generators to link in to the national grid. This argument was strengthened with the recent award of a seabed lease to Aegir Wave Farm Ltd, who are planning a 10MW farm, with up to 26 Pelamis P2 “sea snake” energy converters installed somewhere between Burra and Fitful Head. Work could potentially start in 2013, but without an interconnector this project could not go ahead.
A subsea electricity cable linking Scotland to Norway would allow the import and export of electricity between the UK and Scandinavia. This would go a long way to helping to smooth out the variability inherent ion renewables, particularly wind. In February the First Minister announced the launch of a jointly-owned interconnector development company, NorthConnect – whose work will be supported with €50,000 from the Scottish European Green Energy Centre – as he addressed the Scottish Renewables-Scottish Enterprise offshore wind conference in Aberdeen. While a number of options are being explored, there is a technical preference for the shortest route, which would mean a landing point in the North East of Scotland.
Time is Pressing
Laying these interconnectors in not going to be cheap and the question as always is who is going to fund them. However, if the committment to these vital links is seen to be lacking it will discourage the many companies currently looking into investing in renewable projects in the islands. The Scottish government needs to reassure the industry that when the power comes onstream the cables wil be in place to deliver it to the grid.
New forecasting system goes on trial at National Grid
- Increasing wind capacity leads to need for more accurate forecasting of available wind generation
- Ability to plan for intermittency of wind generation
- New system will save carbon as less fossil fuel generation will be needed in reserve
A new wind power forecasting system is going on trial at National Grid, enabling better integration of wind generation in scheduling and operation of the electricity grid.
Under the new system, wind speed forecasts will be prepared initially for 34 locations in the UK. The forecasts are based on the speed of the wind, the size and height of the turbine and weather conditions predicted by multiple forecasts. Using the latest mathematical techniques, the best forecast will be chosen on the basis of recent performance.
The new system will be updated 4 times a day and will produce 12 forecasts per location. This will enable engineers to turn the medium term wind power forecast into power output forecasts. And as it gets closer to real time balancing of demand and generation, engineers in the Electricity National Control Centre will have more accurate data to make fine adjustments to expected output from wind farms.
Wind forecasting is critical to predicting the output from wind farms. With wind speeds of less than 4 metres per second (m/s) no power is generated. At about 16 m/s there is optimum output and most turbines cut out at about 26 m/s. At these very high wind speeds, generation can suddenly cut out, but better forecasting will help anticipate and track conditions.
Alan Smart, National Grid’s Energy Operations manager said:
“At the moment there is about 5 Gigawatts of installed wind generation in the UK and this is set to grow by about 2 Gigawatts a year for the next 5 years. Hence it’s becoming more important for us to be able to predict output within a quite narrow spectrum of weather conditions.
“As well as better indications of wind speed, we should also be able to more accurately predict wind direction and time of arrival of a weather system moving across the country Our ability to forecast will improve as we gather all this information and it becomes a growing database for future reference.”
Better forecasts of wind generation output will also help National Grid engineers plan more accurately how much other generation will need to be held in reserve to meet wind intermittency. This could cut carbon emissions as less fossil fuel generation will be needed. It will also help with scheduling decisions and planning outages.
Alan Smart added:
“Wind farms are going to be able to offer fast response services to the grid and the new forecasting system will help us integrate this important renewable resource in the best way “
The new system, which has been in development since September 2008, replaces the old “Windy Millar“ forecasting tool.
23 May 2011 – Joint press notice from DECC, National Grid and RIBA
“It’s crucial that we seek the most acceptable ways of accommodating infrastructure in our natural and urban landscapes. I hope the pylon design competition will ignite creative excitement, but also help the wider public understand the scale of the energy challenge ahead of us.” (Chris Huhne)
Architects, designers, engineers and students of these disciplines are being challenged to rethink one of the most crucial but controversial features of modern Britain: the electricity pylon.
A new competition has today been launched, run by the Royal Institute of British Architects (RIBA) for the Department of Energy and Climate Change (DECC) and National Grid, that calls for designs for a new generation of pylon.
There are more than 88,000 pylons in the UK, including 22,000 on National Grid’s main transmission network in England and Wales. These stand some 50 metres high, weigh around 30 tonnes and carry up to 400,000 volts of electricity over thousands of kilometres of some of the most exposed, weather-beaten parts of Britain. But the familiar steel lattice tower has barely changed since the 1920s.
As well as exploring the design of the pylon itself, the competition aims to explore the relationship between energy infrastructure and the environment within which it needs to be located. The challenge is to design a pylon that has the potential to deliver for future generations, whilst balancing the needs of local communities and preserving the beauty of the countryside.
Energy and Climate Change Secretary Chris Huhne said:
“The dual challenge of climate change and energy security puts us on the brink of a new energy construction age. The equivalent of twenty new power stations is needed by 2020, much more beyond that, and they’ll all need connecting to the grid.
“It’s crucial that we seek the most acceptable ways of accommodating infrastructure in our natural and urban landscapes. I hope the pylon design competition will ignite creative excitement, but also help the wider public understand the scale of the energy challenge ahead of us.”
National Grid’s Executive Director UK, Nick Winser said:
“Much of the new low-carbon generation is planned for remote or coastal areas, which means new infrastructure will be needed to get the electricity we need to our homes, businesses and vehicles. While underground connection will be a viable solution in some sensitive locations, new and replacement pylons will be needed and National Grid is equally keen to support the development of the most visually acceptable overhead solutions.
“The pylon as we know it has served the nation well, but new technologies and materials mean there may now be opportunities for new designs. National Grid is excited to be part of opening up this design challenge. We will give serious consideration to developing the winning design for use in future projects.”
Ruth Reed, President of the Royal Institute of British Architects (RIBA), said:
“Design has never been far from our energy network. The current pylon design was chosen by Sir Reginald Blomfield, a leading architect of his day back in 1927, but the familiar steel lattice tower design has barely changed since then.
“Architects, designers and engineers strive to improve the quality of our environments and our lives. This is a technically challenging but exciting competition, with the potential to improve our landscapes for decades to come, and I expect it to generate widespread interest.”
The competition closes on 12 July, with shortlisted candidates notified at the end of July. The shortlist will then have the opportunity to work with National Grid before submitting their final designs at the beginning of September. The designs will be open for the public to view and comment on via the competition website and also at an exhibition to be held at the V&A as part of London Design Festival (17-25 September). The judging panel will meet in October to choose an overall winner.
Chris Huhne will chair the judging panel, which will include Nick Winser, Director of the V&A Sir Mark Jones, architects Sir Nicholas Grimshaw and Bill Taylor, engineer Chris Wise, the journalist Jonathan Glancey and a senior representative from RIBA.
A prize fund of £10,000 will be shared amongst the winning candidates and National Grid will give consideration to developing the winning design for use in future projects.
The competition is now live and open for registration at www.ribapylondesign.com
Aberdeen group to carry out environmental assessment
Aberdeen based energy consultancy Xodus Group announced last week at the All-Energy conference and exhibition in Aberdeen that it will design and execute an environmental impact assessment (EIA) for Statoil for a possible demonstration project showcasing the world’s first floating offshore wind farm.
The Hywind turbine is based on the Hywind demonstrator prototype, which has been successfully tested by Statoil in Norway for over a year. Located 10 km offshore Karmøy, the prototype Hywind has a capacity of 2.3 MW. The demonstration stage has boosted knowledge about the operation of floating offshore turbines, and particularly the effects of wind and waves on the structure. An area off the North-east coast of Scotland will now be assessed as a potential candidate for the first pilot ‘park’ of up to five units.
Based on proven semi-submersible technology from the oil and gas industry, Hywind has been designed for deep, rough waters. The floating structure looks very like a conventional wind turbine, but the underwater base of the mast is filled with a ballast of water and rocks. The structure extends some 80 metres beneath the sea’s surface and is attached to the seabed by a three-point mooring. The environmental study, assessing the impacts a deployment of a Hywind Pilot Park may have, will start this summer.
James Ingram, Head of Low Carbon at Xodus Group said: “The Hywind project is unique, and we are delighted to be working with Statoil on this innovative technology. Our team of environmental experts will be carrying out a thorough assessment of the proposed development, in close cooperation with Statoil, to analyse any potential impacts. One of the main advantages of the floating structure is that the turbines do not need to be piled into the seabed, reducing its environmental impact.”