Offshore wind at Blyth

Renewable Energy 24 (2001) 545–551www.elsevier.nl/locate/renene

Offshore wind at Blyth

David Still *

AMEC Border Wind, Haugh Lane Industrial Estate, Hexham, Northumberland, NE46 3PU, UK

Abstract

The UK’s first offshore wind farm will be built off the coast of Blyth, Northumberland, inJuly 2000. This paper describes the project and the process required to obtain the consents toallow this pioneering project to proceed. 2001 Elsevier Science Ltd. All rights reserved.

Keywords: Wind; Offshore; Planning; Consents

1. Offshore wind in the UK

Since the beginning of the modern wind energy era, which followed the oil crisisof the late 1970s, the installation of wind turbines offshore has regularly been con-sidered as different nations have formulated their wind energy programmes. Thearguments were, and still are, based on the notion that the potential of wind energyon land in densely populated countries is limited compared with total national energydemand, and that countries with relatively long coastlines could increase theirexploitable wind potential by installing wind turbines offshore.

1.1. Initial studies

Between 1977 and 1986 initial studies on the siting, technology and economicsof large-scale offshore wind turbine systems were carried out in the Netherlands,Sweden, the UK, Denmark and the USA.

* Tel.: +44-1434-601224; fax: +44-1434-601200.E-mail address: [email protected] (D. Still).

0960-1481/01/$ - see front matter 2001 Elsevier Science Ltd. All rights reserved.PII: S 09 60 -1481( 01 )0 0040-4

546 D. Still / Renewable Energy 24 (2001) 545–551

1.2. UK developments

In 1983/4 work was carried out by the Wind Energy Group for the Departmentof Energy to assess the economics of siting 100 m diameter, horizontal-axis windturbines offshore in a 2 GW array.

The main tasks of the study were the outline design of a 100 m diameter offshoreturbine rated at 6 MW, the costing of 320 machines of this design deployed in a 2GW array, and assessment of the cost of energy from such an array.

Based on these studies, the perception of offshore wind energy in the mid-1990sin the UK was that it would be too expensive to develop for a number of years.There were no special mechanisms in place for the development of offshore windfarms or even demonstration projects in the UK, and it was left to developers them-selves to use existing mechanisms for onshore wind farms to promote offshore sites.

In the fourth round of the Non-Fossil Fuel Obligation (NFFO) in 1997, twodevelopers succeeded in obtaining contracts to sell the electricity for proposed off-shore sites. One contract was awarded for 30 MW capacity at Gunfleet Sands in theThames Estuary and another was awarded to Border Wind for two 750 kW windturbines on the North Spit 1 km offshore at Blyth in Northumberland. After a longgestation period, the Blyth project has been expanded to two 2 MW turbines and isdue to be installed during 2000 as the first offshore wind farm in UK waters.

A number of organisations are actively developing large wind farms for sites off-shore of the UK and are awaiting the announcement of a support mechanism to pushthese sites forward.

1.3. Blyth Harbour wind farm — first UK semi-offshore wind farm

1.3.1. IntroductionNine 300 kW wind turbines were erected along an exposed pier at Blyth Harbour

in 1992. The pier is over 100 years old and protects the Port of Blyth from the sea.Seven of the turbines had to be erected using a floating crane as there is no vehicularaccess along the pier. Access for maintenance of the wind farm is carried out fromthe water. All communications for turbines to the control computer use radio modemlinks. Of interest for fully offshore wind farms are the results of corrosion monitor-ing, a review of problems during erection of the wind turbines and the reliability ofthe radio modem links. Extensive monitoring has been carried out both before andafter installation to examine any effects on the local bird population. The turbinesare within 300 m of a terrace of houses and three of the turbines are dual-speed toensure quiet operation during periods of light winds.

1.3.2. FoundationsThe most demanding aspect of the wind farm was the foundations for seven of

the turbines installed on the breakwater. The construction of the breakwater variesalong its length, but generally consists of mass concrete with a masonry- or rubble-filled core.

The ground conditions beneath the breakwater were determined by core drilling

547D. Still / Renewable Energy 24 (2001) 545–551

through the concrete and into the bedrock beneath at each of the wind turbinelocations. This established that while in some cases the breakwater was founded onbedrock, at other locations a layer of boulder clay, gravel or silt existed up to about1 m thick.

The foundation design adopted consisted of a series of underpinning piles (up to22 per foundation, each up to 15 m long), installed by drilling through the breakwaterand into the bedrock beneath, installing steel tubes and grouting up afterwards.Extending the steel tubes above the top of the breakwater enabled the reinforcedconcrete block foundation containing the anchor bolts for the wind turbines to becast on top of the breakwater and firmly attached to it.

Concrete for two of the foundations was pumped; for the remaining five, it wasferried across the river in skips. This required careful timetabling to allow for tidesand other shipping.

1.3.3. Grid connectionThe grid connection is into the local Northern Electric plc grid, 4 km from the

site. Unlike rural wind farms the grid in the area is very strong, with two coal-firedpower stations, and the east coast, National Grid link to Scotland within sight of thewind farm.

1.3.4. Wind turbine installationsThe major components were manufactured and assembled in Belgium. Shipping

was arranged direct to Blyth from Antwerp using a chartered ship. A slight delayoccurred during this process due to bad weather, which also affected the deliveryof the barge crane. The nacelles, blades and towers were unloaded on to the quaysideon the other side of the harbour. The turbines on the breakwater were erected byfloating crane moored in the harbour.

The floating crane was expensive to hire, so the installation was carefully plannedto minimise the hire period. When shipping permitted, the crane was in use on bothhigh tides each day. A couple of days were lost to bad weather. Three lifts werecancelled due to high winds and three lifts were abandoned due to waves of swell.At the peak, 50 people were working during this period. The installation occurredduring October and November, with typically nine hours available daylight. Withthe variation in tides, this meant that at times work was carried out under localfloodlights. With the swell factor, and the effect of transfer of load during the liftingprocess, it was necessary to devise a suitable method to allow the tower to settle onto the anchor bolts.

1.3.5. Costs and fundingThe project cost £3.2 million (wind turbines 58%; foundations 18%; installation

12%; grid/HV 6%; preformation costs 6%).

1.3.6. PerformanceThe wind farm started generation at the beginning of January 1993.The turbines are linked to a central computer in the Harbour Master’s Office by


radio links. These initially proved unreliable and more error checking had to beintroduced in the software. The turbine performance was not affected — just therecord keeping, as the turbine controllers in each machine perform all control func-tions.

The noise from the turbines has turned out to be slightly quieter than predicted,with the dual-speed turbines having a source noise level of 94 and 98 dB(A) in low-and high-speed modes, respectively, and the single-speed machines having a valueof 101 dB(A). The Environmental Health Officers of both councils are happy withthe schemes.

Visually the turbines have been well received. They have rapidly become part ofthe background, only being really noticeable on a sunny day from the beach. Thelinear arrangement is generally thought to be attractive.

The purple sandpipers were unaffected by the installation, using the roost besideone turbine even when the crane was alongside. They have taken advantage of theshelter provided by the high-voltage cable duct. As a result of this, additional woodenshelters have been provided for the birds when the wind is from the opposite direc-tion. Given the baseline data available, and given that there are over 100 species ofbirds seen in the vicinity of the wind farm, it was decided to expand the scope ofthe bird study and continue it with the support from the Department of Trade andIndustry’s (DTI’s) New and Renewables Programme.

The enhanced corrosion protection for the towers has proved to be effective, withno problem after 7 years of operation of the wind turbines sometimes in extreme seas.

2. The offshore wind energy resource

The offshore deployment of wind turbines offers a number of apparent advantagesfor the large-scale exploitation of wind energy.

2.1. The UK resource

By comparison with land-based wind farms, particularly in the UK and Europe,offshore areas have fewer restrictions and wind energy is less likely to be in conflictwith other activities. Whilst the restrictions on siting are more numerous than mightinitially be anticipated, they are unlikely to set a practical limit to the exploitationof offshore wind energy. The same cannot be said for land-based wind farms.

Looking at areas more than 5 km offshore and with water depths of between 10and 50 m (LAT), and considering the external and natural constraints, areas havebeen identified as being suitable for the location of wind turbines. The total areaidentified as “probable” was 21,750 km2, with a further “possible” area of 11,850km2. Some of these areas were relatively small, between 2 and 4 km2; however, over60% of the sites have an area of at least 30 km2 and account for 96% of the totalestimated resource.


2.1.1. Wind speedDue to the lack of physical obstructions and lower surface roughness of the sea,

average wind speeds offshore are expected to be higher than at most onshore areas.Upland areas on the west coast of the UK will, as a result of their topography, yieldhigher wind speeds. These, however, are by no means typical of the UK and whilstthey provide a significant resource, they are small compared with the offshore areas.

3. Siting permissions, consents and consultations for Blyth

3.1. Food and Environment Protection Act 1985 (FEPA)

A licence is required under this Act for deposit of substances and articles belowmean high water. This covers the structure and the cable. The Marine EnvironmentalProtection Division of the Ministry of Agriculture, Food and Fisheries (MAFF) isresponsible for issuing such licences. In considering an application, they considerprotection of the marine environment, the living resource which it supports, andinterference with other uses of the sea. The licence will cover site preparation, instal-lation, operation and decommissioning.

Organisations likely to be consulted by MAFF include:

� Fisheries Lab, Conwy (fish);� Fisheries Lab, Burnham on Crouch (water quality); and� Sea Fisheries Inspectorate (fishing).

3.2. Coast Protection Act 1949 (CPA)

Installation in tidal waters requires the consent of the Department of Environment,Transport and Regions [DETR — formerly the Department of Transport (DoT)]under S.34(1) of the CPA, as amended by the Merchant Shipping Act 1988 andextended by the Continental Shelf Act 1964. This act covers navigation, mark-ings, etc.

Organisations likely to be consulted by DETR are:

� Crown Estates;� Royal Yachting Association (RYA);� General Council of British Shipping;� British Motorship Owners’ Association;� MAFF;� Ministry of Defence (MOD);� Civil Aviation Authority (CAA);� Air Traffic Control or local airports;� Trinity House/Northern Lights Board; and� Local Ports Authority or Harbour Masters.


3.3. Transport and Works Act 1992 (TWA)

The Act enables the Secretary of State to make an order (i.e., grant consent) toworks which interfere with rights of navigation in waters up to the territorial limit(12 nautical miles from low water mark shown on Admiralty charts, 1 nauticalmile=1852 m). An order under the TWA establishes the developer’s rights and is adefence against nuisance claims from boat/ship owners and fishermen. This authorityof the Secretary of State cannot be exercised without reasonable consent of all partiesand the TWA process involves a lengthy consultation exercise and, potentially, aPublic Inquiry.

3.4. Planning permission

Planning permission is not required below low water level; however, the onshoreprotection of the submarine cable and any switchgear cubicle onshore will requirepermission from the local planning authority.

3.5. Crown Estates

Strictly, Crown Estates have no statutory authority, but are the “landowners” andtherefore a lease will need to be negotiated. The lease will include the submarinecable route up to high water. The cost of the lease may have to include for the lossof revenue if the wind farm is in a potential aggregate dredging area.

3.6. Oil and gas exploration

If a prospective site is in an area already licensed for oil and gas exploration, thennegotiations with the company or consortium that holds the licence will be necessary.It is not known if they have a right of veto or a right to charge a rent or fee.

3.7. Sand and gravel extraction

If a prospective site is an area already licensed by Crown Estates for dredging,agreement will be necessary with the licensee. It is unlikely that agreement will bereached at little cost.

4. Blyth offshore wind farm

Blyth will be the site of the UK’s first offshore wind farm. Two 2 MW windturbines will be installed in mean water depths of 8 m with a tidal range of 5 m.The turbines will be exposed to the harsh climate of the North Sea. At present theproject has the benefit of an NFFO power purchase contract and an EC Thermie£700,000 grant. All consents have been obtained. Bore holes have been drilled to


confirm the site geology and detailed foundation design will be completed by the endof September 1998. The wind turbines will be operational by the summer of 2000.

The wind farm will be owned by a project company — Blyth Offshore WindLimited. The shareholders in this company are PowerGen Renewables DevelopmentLimited, Shell Renewables, Nuon UK Limited and Border Wind Limited. BorderWind Limited is now wholly owned by AMEC Services Limited.

The turbines will be supplied by Vestas. The installation will be carried out byAMEC Marine with specialist drilling services from Seacore. The underwater cablelaying will be carried out by Global Marine Services. Project Management andEngineering will be carried out by Shell UK and AMEC Border Wind.

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Offshore wind at Blyth