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The development and operation of the 9.0 MW taff ely wind farm in south wales
Renewable Energy, Vol.5, Part I, pp. 668--674, 1994 Elsevier Science Lid Printed in Great Britain 0960-1481/94 $7.00-1-0.00
Pergamon
THE DEVELOPMENT AND OPERATION OF THE 9.0 MW TAFF ELY WIND FARM IN SOUTH WALES I.D. PARKER Generation Business, East Midlands Electricity plc, Caythorpe, Nottingham, NG14 7EB, UK
ABSTRACT The Taft Ely wind farm represents one of the first projects to be established in the UK on a commercial basis. The paper outlines the development issues and indicates the operational factors that are relevant to the site.
KEYWORDS Wind, renewable, energy,
PROJECT DEVELOPMENT
The
]~'oiect
The wind farm is a joint venture development between Perma Energy, based in Milton Keynes and East Midlands Electricity whose Head Office is in Nottingham. Initial work on the project was undertaken by Perma Energy following their discussions with the two Welsh hill farmers on whose land the wind farm is located. East Midlands Electricity joined with Perma Energy to contribute additional development skills and to enlarge their investment activities in renewable energy projects. The project consists of twenty 450kW turbines which were supplied and installed by Nortank who are one of the larger Danish wind turbine manufacturers and operate under a marketing agreement with Thyssen. The site is well suited to wind farm development and is located on two adjacent ridges near to the town of Gilfach Goch in Mid Glamorgan, South Wales. The higher of the ridges extends to approximately 280m above sea level with the other being approximately 100m lower on average. There is good exposure to wind in all directions and, in general, the site is well rounded which has the benefit of limiting the possibility of separation of the wind flow. There is, however, a steep slope at the south eastern comer which could cause this effect. The site is illustrated in Figure 1.
668
669
Fig. 1.
Taft Ely Wind Farm
Evaluation and Design The essential first step was to install wind monitoring equipment in order to measure actual wind speeds and then to con'clam these with historicalmeteorological data fi'om local weather stations in order that a long term projection of annual mean wind speed could be obtained. A 30m anemometer mast was erected for a twelve month period and data collected on the ten minute wind speed and direction, gust wind speed and standard deviation.
In order that investment decisions are well based it is of the upmost importance that the greatest dcgrcc of certainty is obtained from the analysis of the wind speed data collected. With energy capture from a wind turbine being proportional to the cube of the wind speed there is significant scope for poorly researched wind farm sites to underpcrform. Consultants wcrc retained to analyse the wind speed data and to translate this into a wind farm layout which would optimist the layout of the turbines in order to maximisc energy capture. The data was translated into a long term annual mean wind speed using the technique of correlation of the sitedata with that from a local meteorological station and then utilising the historical station information to project a long term figure for the site. This exercise highlighted the difficultyof obtaining soundly based data from metcorogical stations which could be used with confidence. Generally this is not gathered in sufficientdetail and with the necessary accuracy for this type of analysis and the geographical sitingof the stations can make correlation with the wind farm mast a difficult exercise. Two meteorological stations at Rhoosc and Mumbles Head wcrc utilised and an acceptable long term projection obtained. Once the long term wind spe.~l for the sitohad bccn established, existing wind farm models wore utilised to produce a turbine layout which optimised the turbine positioning in order to minimisc losses duc to wake effects and maximise energy capture.
670 THE PLANNING PROCESS The project was one of the first in the UK to apply for and obtain planning permission. As one of the initial projects it did not attract the high level of general interest that has subsequently been associated with more recent planning applications and led to the need for a relatively largo number of public enquiries prior to planning permission being obtained. A good degree of general consultation was undertaken and potential issues of concern on such matters as the possible effect on television reception dealt with in a detailed way. Conditional planning consent was given in July 1991 subject to certain provisions, with full consent granted in February 1993.
COMMERCIAL ISSUES The Non Fossil Fuel Obligation The generation of electricity in the UK is dominated by the fossil fuels with particular use of coal for many years and the more recent development of significant capacity of natural gas fired combined cycle plants. In addition the nuclear industry currently provides approximately 21% of requirements. The UK is fortunate in having the ready availability of these fuels and has not needed to develop renewable energy sources in order to meet short term energy pressures. Research and development of renewable energy technologies has however been taking place in a structured way with Government and European support. This whole process has been given additional momentum as a result of the recognition of environmental pressure and the Government has a target for the introduction of 1500 MW of renewable energy generation by the year 2000. This is driven by the basic wish to encourage sustainable development and is an important part of the UK commitment towards the target for carbon dioxide reduction. The Non Fossil Fuel Obligation is the mechanism operated through the Department of Trade and Industry and the regulatory authority ( Office of Eleclricity Regulation ) which provides structured support for renewable energy. The reasoning behind the subsidy arrangements is that they exist to provide transitional support during the period in which renewable energy technology develops towards a position where it can provide sustainable energy on a competitive basis with fossil fuels. The Taft Ely wind farm successfully secured a contract under the second round of the Non Fossil Fuel Obligation and it receives income of 11 pence per kWh (at 1992 price levels) for each unit of electricity generated up to the end of 1998. Beyond this period income levels will be significantly reduced and will be typically equal to the traded price of fossil fuel electricity which is currently approximately 2.4 pence per kWh.
Financial Structure The capital cost of the project has boon approximately £9.5M which is typical for projects of this type in the UK. The make up of this figure between the various components is indicated in Figure 2. Funds for construction have been secured on a project financed basis with the main debt being provided by Hambros and Bayerische Vereins Banks. East Midlands Electricity and Pe~ma Energy subscribed the majority of the equity as owners of the project with a further tranche of debt coming in the form of subordinated loans from two participating contractors.
671 Development and Financing
Civils
Pro ect Management
Electrical
Turbine Supply and Erection
Fig. 2.
A significant difficulty arose during the financing phase as a result of the withdrawal of the UK from the European Exchange Rate Mechanism and the subsequent fall in the pound against the DM in which the turbines were priced. This was successfully overcome but is an inevitable issue as a result of the absence of a diverse home based wind turbine industry.
Contractual Arrangements Construction was undertaken under a multi contract structure with the major contract being the one with Nordtank for turbine supply and erection. A local Welsh civil contractor completed the roads, turbine foundations and control building with East Midlands Elcclficityinstallingthe on site electricalequipment. Elec~icity is exported to the local 33 kV network and a new 3kin overhead line connection was installed by South Wales Electricity. Project Managernent was provided by Elsamprojekt from Dc~mark on the basis of the experience resulting from the Danish wind farm programmes of previous years.
CONSTRUCTION PHASE
Construction began in March 1993 on the basis of a 35 week programme which was successfully completed with turbine commissioning beginning in late July and project takeover on Ist October. Weather conditions were fortunately favourable which was particularly important in enabling good early progress to be made on access roads and foundations. The hilly nature of the site would have caused some difficulty if wet conditions had existed. For the majority of projects of this type this probably means that construction should be programmed for the su...... ~r months which is also beneficial for cash flow reasons with the higher annual wind speed period immediately following commissioning.
672
PROJECT OPERATION Energy Production Full operation began in September 1993 and subsexlUent performance has remained generally on target to date. Given the wide variability of wind patterns, the level of monthly generation against anticipated budgetary levels will only emerge over a number of years. Figure 3 indicates the actual monthly generation levels since commissioning in percentage terms compared to the expectations based on typical annual wind speed dislribution patterns. 200
150
Energy Output
100
(%) 50
Oct
Nov
Dec
Jan
Feb
Mar
Fig. 3.
Turbine availability leeds have so far exceeded the target level of 95%, although it should be noted that this figure is based on the time during which the wind speed is actually between cut in and cut out figures ( 4.5 - 25 m/s~ ). No significant loss of performance time has occurred due to equipment failure apart from 30 turbine days when the blade tips of a rotor on each of two turbines was sU'uck by lighming in December and had to be replaced.
Public Acceptance It has been possible to assess the reaction of the public on two separate occasions. The wind farm is located in an area which is relatively well populated. Approximately 15,000 people live within 5kin in a number of communities of which the largest are Gilfach Goch and Tonyrefail. Given the location of the wind farm on a hill top site the majority of these people will see the site on a regular basis either from their homes or whilst travelling locally. An open day for the benefit of the local population was held during November 1993 when approximately 700 adults and children attended. They had the opportunity to walk around the site as well as talk to the project developers. An informal questionnaire completed on the day gave a positive picture of attitudes towards the project and to wind farms in gen='al. This is summarised in Figure 4.
673
% OF ADULTS WHO THOUGHT :-
%
WINDPOWER A VERY GOOD IDEA
86
TURBINES MAKE SCENERY MORE INTERESTING
50
TURBINES SPOIL THE SCENERY
12
WINDFARM QUIETER THAN EXPECTED
90
.
Fig. 4. A further more soundly based assessment was obtained in February 1994 when a public attitude survey was commissioned from a market research organisation. This also showed a generally positive response from those who had an opinion on the issue. It is perhaps surprising that, when there has been such widespread comment on the recent development of wind farms, that approximately 50*6 of the community in an area which lives close to a site had no particular opinion of the project in either way.
FUTURE INVESTIGATION
Rotor Desi~n The rotor design of the Nordtank 450kW turbines used on the site is of a stall regulated type where energy from the wind at higher wind speeds is shed through an increasing stall effect. As part of a development exercise Nordtank together with blade manufacturer, LM Glasfiber and Scioteeh is undertaking a project on one of the turbines in order to assess the opportunity for enhanced energy capture as a result of change of shape. This project is supported under the European funded Thermie progtannne and involves the incorporation of new knowledge about the aerodynamics of such blades in terms of litL drag and stall. The new blades will have a more desirable lift to drag ratio and a twist distribution which should allow stall to occur more widely over the area of the blade as the stall condition arises. The new 19m blades will replace the existing 17m units after approximately one year of operation and instrumentation will enable the change in energy capture as well as the revised loadings on the gearbox and transmission system to be assessed.
Dynamic Load M.easur~ent An early concern in the development of the project was the possibility of accelerated fatigue wear due to the relatively close spacing of the turbines and the topography of the site. An assesment of the dynamic loading cycles in conjunction with the design characteristics of the turbine indicated that this would not be a problem, The site does, however remain of interest as far as evaluation of these effects, particularly in comparison to those experienced by a wind farm located in a flat terrain, As result, the site is being utilised as part of a European funded Joule H study in which the UK participant is Ganad Hassan. Structural and wind speed data will be collected over an extended period and utili~l in a study in which data from other wind farms throughout Europe located in differing terrains will also be gathered.
674 The objectives of the study include the identification of the differences in loading experienced by turbines in differing terrains leading to the preparation of guidelines for the design loads in wind farms in general.
CONCLUSIONS The Taft Ely wind farm is one of the firstbatch of such projects to be established in the UK. The development and operational experience so far has enabled new knowledge of many aspects associated with this technology to be obtained. These include the many social and mchnical matters as well as the essential economic issues which have to come together if projects of this type are to contribute a significant proportion of future energy needs.
Pergamon
THE DEVELOPMENT AND OPERATION OF THE 9.0 MW TAFF ELY WIND FARM IN SOUTH WALES I.D. PARKER Generation Business, East Midlands Electricity plc, Caythorpe, Nottingham, NG14 7EB, UK
ABSTRACT The Taft Ely wind farm represents one of the first projects to be established in the UK on a commercial basis. The paper outlines the development issues and indicates the operational factors that are relevant to the site.
KEYWORDS Wind, renewable, energy,
PROJECT DEVELOPMENT
The
]~'oiect
The wind farm is a joint venture development between Perma Energy, based in Milton Keynes and East Midlands Electricity whose Head Office is in Nottingham. Initial work on the project was undertaken by Perma Energy following their discussions with the two Welsh hill farmers on whose land the wind farm is located. East Midlands Electricity joined with Perma Energy to contribute additional development skills and to enlarge their investment activities in renewable energy projects. The project consists of twenty 450kW turbines which were supplied and installed by Nortank who are one of the larger Danish wind turbine manufacturers and operate under a marketing agreement with Thyssen. The site is well suited to wind farm development and is located on two adjacent ridges near to the town of Gilfach Goch in Mid Glamorgan, South Wales. The higher of the ridges extends to approximately 280m above sea level with the other being approximately 100m lower on average. There is good exposure to wind in all directions and, in general, the site is well rounded which has the benefit of limiting the possibility of separation of the wind flow. There is, however, a steep slope at the south eastern comer which could cause this effect. The site is illustrated in Figure 1.
668
669
Fig. 1.
Taft Ely Wind Farm
Evaluation and Design The essential first step was to install wind monitoring equipment in order to measure actual wind speeds and then to con'clam these with historicalmeteorological data fi'om local weather stations in order that a long term projection of annual mean wind speed could be obtained. A 30m anemometer mast was erected for a twelve month period and data collected on the ten minute wind speed and direction, gust wind speed and standard deviation.
In order that investment decisions are well based it is of the upmost importance that the greatest dcgrcc of certainty is obtained from the analysis of the wind speed data collected. With energy capture from a wind turbine being proportional to the cube of the wind speed there is significant scope for poorly researched wind farm sites to underpcrform. Consultants wcrc retained to analyse the wind speed data and to translate this into a wind farm layout which would optimist the layout of the turbines in order to maximisc energy capture. The data was translated into a long term annual mean wind speed using the technique of correlation of the sitedata with that from a local meteorological station and then utilising the historical station information to project a long term figure for the site. This exercise highlighted the difficultyof obtaining soundly based data from metcorogical stations which could be used with confidence. Generally this is not gathered in sufficientdetail and with the necessary accuracy for this type of analysis and the geographical sitingof the stations can make correlation with the wind farm mast a difficult exercise. Two meteorological stations at Rhoosc and Mumbles Head wcrc utilised and an acceptable long term projection obtained. Once the long term wind spe.~l for the sitohad bccn established, existing wind farm models wore utilised to produce a turbine layout which optimised the turbine positioning in order to minimisc losses duc to wake effects and maximise energy capture.
670 THE PLANNING PROCESS The project was one of the first in the UK to apply for and obtain planning permission. As one of the initial projects it did not attract the high level of general interest that has subsequently been associated with more recent planning applications and led to the need for a relatively largo number of public enquiries prior to planning permission being obtained. A good degree of general consultation was undertaken and potential issues of concern on such matters as the possible effect on television reception dealt with in a detailed way. Conditional planning consent was given in July 1991 subject to certain provisions, with full consent granted in February 1993.
COMMERCIAL ISSUES The Non Fossil Fuel Obligation The generation of electricity in the UK is dominated by the fossil fuels with particular use of coal for many years and the more recent development of significant capacity of natural gas fired combined cycle plants. In addition the nuclear industry currently provides approximately 21% of requirements. The UK is fortunate in having the ready availability of these fuels and has not needed to develop renewable energy sources in order to meet short term energy pressures. Research and development of renewable energy technologies has however been taking place in a structured way with Government and European support. This whole process has been given additional momentum as a result of the recognition of environmental pressure and the Government has a target for the introduction of 1500 MW of renewable energy generation by the year 2000. This is driven by the basic wish to encourage sustainable development and is an important part of the UK commitment towards the target for carbon dioxide reduction. The Non Fossil Fuel Obligation is the mechanism operated through the Department of Trade and Industry and the regulatory authority ( Office of Eleclricity Regulation ) which provides structured support for renewable energy. The reasoning behind the subsidy arrangements is that they exist to provide transitional support during the period in which renewable energy technology develops towards a position where it can provide sustainable energy on a competitive basis with fossil fuels. The Taft Ely wind farm successfully secured a contract under the second round of the Non Fossil Fuel Obligation and it receives income of 11 pence per kWh (at 1992 price levels) for each unit of electricity generated up to the end of 1998. Beyond this period income levels will be significantly reduced and will be typically equal to the traded price of fossil fuel electricity which is currently approximately 2.4 pence per kWh.
Financial Structure The capital cost of the project has boon approximately £9.5M which is typical for projects of this type in the UK. The make up of this figure between the various components is indicated in Figure 2. Funds for construction have been secured on a project financed basis with the main debt being provided by Hambros and Bayerische Vereins Banks. East Midlands Electricity and Pe~ma Energy subscribed the majority of the equity as owners of the project with a further tranche of debt coming in the form of subordinated loans from two participating contractors.
671 Development and Financing
Civils
Pro ect Management
Electrical
Turbine Supply and Erection
Fig. 2.
A significant difficulty arose during the financing phase as a result of the withdrawal of the UK from the European Exchange Rate Mechanism and the subsequent fall in the pound against the DM in which the turbines were priced. This was successfully overcome but is an inevitable issue as a result of the absence of a diverse home based wind turbine industry.
Contractual Arrangements Construction was undertaken under a multi contract structure with the major contract being the one with Nordtank for turbine supply and erection. A local Welsh civil contractor completed the roads, turbine foundations and control building with East Midlands Elcclficityinstallingthe on site electricalequipment. Elec~icity is exported to the local 33 kV network and a new 3kin overhead line connection was installed by South Wales Electricity. Project Managernent was provided by Elsamprojekt from Dc~mark on the basis of the experience resulting from the Danish wind farm programmes of previous years.
CONSTRUCTION PHASE
Construction began in March 1993 on the basis of a 35 week programme which was successfully completed with turbine commissioning beginning in late July and project takeover on Ist October. Weather conditions were fortunately favourable which was particularly important in enabling good early progress to be made on access roads and foundations. The hilly nature of the site would have caused some difficulty if wet conditions had existed. For the majority of projects of this type this probably means that construction should be programmed for the su...... ~r months which is also beneficial for cash flow reasons with the higher annual wind speed period immediately following commissioning.
672
PROJECT OPERATION Energy Production Full operation began in September 1993 and subsexlUent performance has remained generally on target to date. Given the wide variability of wind patterns, the level of monthly generation against anticipated budgetary levels will only emerge over a number of years. Figure 3 indicates the actual monthly generation levels since commissioning in percentage terms compared to the expectations based on typical annual wind speed dislribution patterns. 200
150
Energy Output
100
(%) 50
Oct
Nov
Dec
Jan
Feb
Mar
Fig. 3.
Turbine availability leeds have so far exceeded the target level of 95%, although it should be noted that this figure is based on the time during which the wind speed is actually between cut in and cut out figures ( 4.5 - 25 m/s~ ). No significant loss of performance time has occurred due to equipment failure apart from 30 turbine days when the blade tips of a rotor on each of two turbines was sU'uck by lighming in December and had to be replaced.
Public Acceptance It has been possible to assess the reaction of the public on two separate occasions. The wind farm is located in an area which is relatively well populated. Approximately 15,000 people live within 5kin in a number of communities of which the largest are Gilfach Goch and Tonyrefail. Given the location of the wind farm on a hill top site the majority of these people will see the site on a regular basis either from their homes or whilst travelling locally. An open day for the benefit of the local population was held during November 1993 when approximately 700 adults and children attended. They had the opportunity to walk around the site as well as talk to the project developers. An informal questionnaire completed on the day gave a positive picture of attitudes towards the project and to wind farms in gen='al. This is summarised in Figure 4.
673
% OF ADULTS WHO THOUGHT :-
%
WINDPOWER A VERY GOOD IDEA
86
TURBINES MAKE SCENERY MORE INTERESTING
50
TURBINES SPOIL THE SCENERY
12
WINDFARM QUIETER THAN EXPECTED
90
.
Fig. 4. A further more soundly based assessment was obtained in February 1994 when a public attitude survey was commissioned from a market research organisation. This also showed a generally positive response from those who had an opinion on the issue. It is perhaps surprising that, when there has been such widespread comment on the recent development of wind farms, that approximately 50*6 of the community in an area which lives close to a site had no particular opinion of the project in either way.
FUTURE INVESTIGATION
Rotor Desi~n The rotor design of the Nordtank 450kW turbines used on the site is of a stall regulated type where energy from the wind at higher wind speeds is shed through an increasing stall effect. As part of a development exercise Nordtank together with blade manufacturer, LM Glasfiber and Scioteeh is undertaking a project on one of the turbines in order to assess the opportunity for enhanced energy capture as a result of change of shape. This project is supported under the European funded Thermie progtannne and involves the incorporation of new knowledge about the aerodynamics of such blades in terms of litL drag and stall. The new blades will have a more desirable lift to drag ratio and a twist distribution which should allow stall to occur more widely over the area of the blade as the stall condition arises. The new 19m blades will replace the existing 17m units after approximately one year of operation and instrumentation will enable the change in energy capture as well as the revised loadings on the gearbox and transmission system to be assessed.
Dynamic Load M.easur~ent An early concern in the development of the project was the possibility of accelerated fatigue wear due to the relatively close spacing of the turbines and the topography of the site. An assesment of the dynamic loading cycles in conjunction with the design characteristics of the turbine indicated that this would not be a problem, The site does, however remain of interest as far as evaluation of these effects, particularly in comparison to those experienced by a wind farm located in a flat terrain, As result, the site is being utilised as part of a European funded Joule H study in which the UK participant is Ganad Hassan. Structural and wind speed data will be collected over an extended period and utili~l in a study in which data from other wind farms throughout Europe located in differing terrains will also be gathered.
674 The objectives of the study include the identification of the differences in loading experienced by turbines in differing terrains leading to the preparation of guidelines for the design loads in wind farms in general.
CONCLUSIONS The Taft Ely wind farm is one of the firstbatch of such projects to be established in the UK. The development and operational experience so far has enabled new knowledge of many aspects associated with this technology to be obtained. These include the many social and mchnical matters as well as the essential economic issues which have to come together if projects of this type are to contribute a significant proportion of future energy needs.