Oweninny Wind Farm. Oweninny Power Ltd. Environmental Impact Statement. Chapter 4. Alternatives

Transcription

1 Oweninny Power Ltd. Chapter 4 Alternatives Copyright ESB International Limited, all rights reserved.

2 Table of Contents 4. ALTERNATIVES Alternative Electricity Generation Benefits of Renewable Energy Project Context Scenario Worldwide Irish Scenario Other Renewable Energy Resources Role and Benefits of Wind Energy ALTERNATIVE SITES Context Site Suitability Wind Speed Size and Topography of Site Other Factors Renewable Energy Strategy Previous Assessments of Site Suitability Mayo County Council An Bord Pleanála Summary ALTERNATIVE CONFIGURATIONS AND LAYOUTS General Approach Alternative turbine heights Approved and Proposed Layout Approved Layout Development of Proposed Layout Field Survey influence on the design Scoping Exercise influence on design Communication signal corridors Impact of Trees Final wind farm design Micrositing Proposed Arrangement Other Components Electrical Substation Meteorological Masts kv overhead Transmission Lines Summary Planning (Wind Energy) Guidelines 4.18 List of Tables Table 4-1: Global Deployment of Wind Power Table 4-2: Fuel Mix for All-Ireland Electricity Generation Alternatives ii

3 Table 4-3: Planning Applications for Wind Farms Republic of Ireland Table 4-4: Wind Classification Table 4-5: Wind turbine locations identified by IPCC as potential issues Table 4-6: Suitability of 110 kv Ovehead line route Table 4-7: Evaluation of potential Line Routes from Substation 1 against Assessment Criteria Table 4-8: Evaluation of potential Line Routes from Substation 2 against Assessment Criteria List of Figures Figure 4-1: Trend in Wind Turbine Sizes Figure 4-2: Growth of Wind Energy in Ireland Figure 4-3: Average wind velocity at hub height across the EU Figure 4-4: Oweninny Initial Constraints Map Figure 4-5: Planning approved and proposed wind farm layout Figure 4-6: Proposed wind farm layout issued for Scoping Report Figure 4-7: Communication signal corridors with final proposed layout Figure 4-8: Final Constraints Map Figure 4-9: Alternative 110 kv Overhead Line Routes Alternatives iii

4 4. ALTERNATIVES All alternatives that are considered should be capable of successfully achieving the objectives of the development within a reasonable period of time, taking into account economic, social, environmental and technological factors Alternative Electricity Generation Benefits of Renewable Energy In the short-medium term at least, current and future demand for electricity generation capacity in Ireland will remain predominantly supplied by fossil fuel plants. However, renewable and alternative sources of power will play an increasingly important role in meeting power needs in the future. The development of renewable sources of energy is in line with EU and Government policies, which have strong public support. Onshore wind power is recognised as one of the most promising renewable energy sources for electricity generation in Ireland. Wind energy currently represents by far the most significant viable option for electricity generation from renewables. This is also evident in Grid 25, EirGrid s strategy for the balanced and sustainable development of Ireland s transmission system, between now and The strategy will facilitate independent power production and renewables helping to secure Ireland s energy needs into the future. An independent study 1 of the Irish public s attitude towards the development of wind energy indicated a high level of support for developing more sources of renewable energy in Ireland, making it the preferred option among energy policies considered within the study. Ireland s dependence on a finite supply of imported fossil fuels raises questions over the security of supply in future years as reserves of fossil fuels are depleted or costs rise significantly. This brings the need for locally generated renewable energy sharply into focus. The main benefits of developing alternative energy sources are seen as reducing air emissions from burning fossil fuel with consequent climate change effects as well as complying with international agreements on limiting such emissions. The utilisation of indigenous resources is also considered of primary importance. The above are now reflected in Ireland s energy policy and it is evident that the renewable energy sector is strongly supported by Government policy Project Context Wind power has become an important source of energy worldwide, mainly due to the following: environmental considerations; the search for energy alternatives and for a reduction in energy dependence; and the increasing costs of oil and other fossil fuels. The evolution of modern wind turbines is a story of engineering and scientific skill, coupled with a strong entrepreneurial spirit. In the last 20 years, turbines have increased 1 Attitudes Towards the Development of Wind Farms in Ireland, SEI (now SEAI), 2003 Alternatives 4.1

5 in size by a factor of 13 (from 300 kw to 4,000 kw and beyond), the cost of energy produced has reduced by a factor of more than five and the industry has moved from an idealistic fringe activity to an acknowledged component of the power generation industry. At the same time, the engineering base and computational tools have developed to match machine size and volume Scenario Worldwide As shown in Figure 4-1 rapid developments in technology have lead to turbines of up to 4,500 kw capacity now being available worldwide. The deployment of larger wind turbines is reflected in countries having well established wind energy networks, where new, more efficient and higher rating turbines are replacing older turbines. There is also a general industry trend to equip turbines with increasingly larger rotors. Worldwide wind generating capacity stood at approximately 282GW in 2012 with this capacity in 2012 representing a ten-fold increase over the intervening decade. Worldwide growth is shown in Table 4.1. Table 4-1: Global Deployment of Wind Power Year Installed Capacity (MW) 74,100 93, , , , , ,000 Annual Growth 25.4% 26.7% 28.1% 31.9% 24.5% 20.2% 18.5% 9, 616 MW of new wind energy was installed in the EU in 2011 represented an investment of 12.6 billion. The EU moved from 0.09% wind contribution of electrical demand in 2000 to 6.3% in In Germany, the country with the most installed wind generating capacity at 29,100 MW, approximately 7.5% of its electricity was supplied from wind power in 2011, while Spain in second place with over 21,700 MW of capacity generated nearly 16% of its electricity from wind. Denmark s wind capacity met almost 26% of its electricity needs in 2011, the largest share in any country. Roscoe Wind Farm in Texas, USA is the world s largest with 627 wind turbines and a total installed capacity of 780 MW. Whitelee Wind Farm located on Eaglesham Moor near Glasgow in Scotland is Europe s largest at 534 MW (target completion date February 2013) Irish Scenario Ireland s first commercial wind farm at Bellacorick, Co. Mayo is now more than 20 years old and there has been sustained growth since then in the deployment of wind power in Ireland. Growth over the past decade is shown in Figure 4-2. EirGrid, the Irish transmission grid operator, has reported that the installed wind capacity in Ireland was 1,637 MW at end December 2012 with a further 451 MW installed in Northern Ireland (SONI) giving a total installed capacity of 2,088 MW on the island. 2 The highest recorded wind power output peaked on 18 th December 2012 with a total of 1,864 MW on an all island basis, sufficient to provide electricity to some 932,000 homes. 2 EirGrid and SONI Operations 2012, All Island Wind and Fuel Mix Summary Report, Alternatives 4.2

6 The Irish target for the renewable energy share of gross electricity consumption is 40% by 2020, estimated as being equivalent to about 5,100 MW of installed wind energy capacity. In December 2012, Ireland and Northern Ireland jointly had approximately 2,088 MW of installed renewable energy capacity, enough renewable generation to contribute to 15% of overall electricity demand. At particular time intervals, wind has produced enough power to meet 50% of electricity on the island. The share of electricity generated in the Republic of Ireland (RoI) from renewable energy sources (RES-E) in 2011 was 17.6%. Wind energy accounted for over 13% of all electricity generation in 2011, hydro accounted for 2.6% and the remaining 2% was from bio-energy sources (mainly biomass co-firing and landfill gas). Wind power installed generating capacity reached 1,637 MW in CO 2 avoided through renewable energy use increased by 267% (6.7% per annum on average) over the period 1990 to 2010 reaching 2.8 Mt CO 2 in 2010 and provisionally 3.6 Mt CO 2 in Wind energy use gave rise to the largest avoidance of emissions in 2010 (60%) followed by solid biomass and hydro. The fuel mix for electricity supplied to the All-Island electricity market in 2011 is presented in Table 4.2. These represent the latest published figures from the CER 4. The fuel-mix of suppliers in Ireland is calculated as required by Regulation 25 of S.I. No. 60 of 2005 which transposes Article 3.6 of Directive 2003/54/EC. Table 4-2: Fuel Mix for All-Ireland Electricity Generation 2011 Fuel Coal Gas EU Fossil Peat Other Renewables Contribution 16% 56% 3% 6% 3% 17% Ireland has an abundant wind energy resource and almost the entire country has either an excellent or very good wind energy resource, as indicated in Figure 4-3. Ireland has the potential to generate the cheapest wind energy in the whole of Europe. Apart from a small area in the south of France, only Ireland, Denmark and Scotland have substantial areas of land where the wind speeds at 50 m above ground level, on open plains, are above 7.5 m/s. However, Denmark is relatively flat, and so derives minimal benefits from the enhanced wind speeds on hilltop sites. Wind farm capacity factors in the range 30-36%, or above, may be expected in Ireland. At Oweninny the capacity factor is predicted to be in the range 30 to 35%. Mayo County Council was a leader in the establishment of the Mayo Energy Agency in 1998 and has been supporting it ever since. The Agency s aim is to support the development of sustainable energy in Co. Mayo and beyond Other Renewable Energy Resources Wind is the world s fastest growing source of energy. Other renewable energy resources include hydro, solar, biomass, tidal, wave and geothermal. Hydro - There are no further suitable large and medium-sized impoundment hydro generation resources that could be developed in Ireland based on natural rivers and 3 EirGrid, All Island Wind and Fuel Mix Summary report Fuel Mix Disclosure and CO 2 Emissions 2011, Commission for Energy Regulation, April 2013 Alternatives 4.3

7 lakes. While a number of small such resources remain, it is not possible that their development could ever present anything other than a minor increase in power generation capacity. Pumped storage such as that operated by the ESB at Turlough Hill and as proposed at Glinsk mountain in North Mayo could offer storage capacity for both renewable and conventional energy during off peak periods but are not themselves primary power producers. Solar - Solar power may be used in either direct heating applications or direct conversion of radiation to electricity by the use of photo-voltaic cells. However, for large applications, its costs remain very high. Feasibility studies continue in areas of high insolation and it would be reasonable to expect commercial development for significant energy outputs to occur first in such areas. This has not yet happened and at present solar power is not a serious option for significant electricity generation in Ireland. Biomass - Biomass energy can be obtained from the combustion of any organic material that is grown and harvested on a regular basis. Suitable materials include forestry and saw mill waste and specially grown short rotation forestry. Edenderry Power Station, owned by Bord na Móna, is already co-firing biomass with peat and is targeting having a 30% co-firing rate by A proposal by Mayo Renewable Power exists to build a 50 MW (net) biomass High Efficiency CHP plant located on the former Asahi site in Killala, Co. Mayo. When developed it would be Ireland s largest independent biomass power plant. In operation, this plant would propose to use virgin biomass (i.e. untreated and uncontaminated clean wood and willow). The fuel would be supplied from a variety of sources including locally grown willow, spruce from local forestry and forestry thinnings along with imported supplies. Tidal - The generation of electricity from tidal power has been under assessment for more than 50 years and various schemes are proposed from time to time. ESB International, which is part of the ESB group of companies, is an investor in a pioneering energy project that installed the world s first commercial scale tidal power generating device, Seagen, in Strangford Lough, Northern Ireland. Locations with naturally high tidal ranges are required and those available in Ireland are generally 2-4m, which is considered modest. Such schemes are highly capital intensive and further developments at Irish locations will await successful operational data from this pilot installation. The Department of Communications Energy and Natural Resources Ocean Renewable Energy Development Plan (OREDP) identifies zones around Ireland suitable for ocean energy. The plan indicates that the tidal resource is very limited in contrast to wind and wave 5. Wave - There has been considerable research on wave power and several wave energy test sites have been constructed internationally, e.g. the European Marine Energy Centre (EMEC) in the Orkneys. To obtain appreciable power outputs, installation in the most active and open sea areas is needed. These areas present very challenging environments to structures and to mechanical and electrical equipment and significant testing of devices at differing scales is required before commercial scale developments can occur. Prototype wave energy converters have been deployed in Scotland, Spain, Portugal and Ireland (Pelamis, Oyster, Wavebob and Ocean buoy for example) for short duration periods. However, to date, wave power has not been demonstrated to be technically feasible or commercially viable on a large scale. ESB has worked closely with 5 Draft Ocean Renewable Energy Development Plan Alternatives 4.4

8 the ocean energy team in the Sustainable Energy Authority of Ireland (SEAI) and the Marine Institute to develop a full scale wave energy test site off the west coast of Ireland at Belmullet in. Termed the Atlantic Marine Energy Test Site (AMETS) it will provide a grid connected wave energy converter test facility for full scale devices. The foreshore lease for this facility is expected to be granted in Significant research continues as evidenced by the extent of interest at the recent International Conference on Ocean Energy 2012 (ICOE) hosted by SEAI in the Convention Centre in Dublin. The ESBI Ocean Energy Group is also active in this field, through the Westwave Project - a proposal to develop a pilot wave energy array off the west coast of Ireland 7. While test installations are being further deployed and wave energy converter testing continues, it is not expected to contribute significantly to power generation in the immediate future. Geothermal - Geothermal power is exploited in many locations throughout the world, where reservoirs of hot or superheated water exist beneath the earth's surface. Most of these systems are installed at locations having reservoirs of water at temperatures in excess of 100 C. Such high temperature reservoirs have only recently been identified in Ireland and commercial exploitation of these resources is still at the concept stage Role and Benefits of Wind Energy Climate change, security of electricity supply, and price stability are amongst the factors supporting the main rationale underpinning the need for renewables. The case for renewable energy development in Ireland is heightened by the high dependency on fossil fuel sources for primary energy consumption. More than 88% of Ireland s total energy requirement is still supplied in the form of fossil fuel. In Ireland, wind energy, because of its developed technology and the large resource available, is seen as making the most significant contribution to renewable energy developments. Ireland has a large offshore and onshore wind resource. Onshore wind is only effectively constrained by the amount of non-firm power the National Grid can accept. This picture will undoubtedly change with the development of Grid 25 by EirGrid post Both onshore and offshore wind farms will have roles to play in renewable energy developments. Offshore wind farms remain considerably more expensive to construct than their onshore equivalents with average capital costs of installation being greater by a factor of more than two, and have higher average operating costs by a factor of approximately 50% 8, due to the obvious difficulties of access for maintenance, etc. In time, problems associated with offshore wind will be solved. However, a need to develop wind farms at suitable onshore sites remains. Wind is the world s fastest growing source of energy. In terms of available technology, it is one of a few viable renewable energy sources currently available in Ireland. This, rather than being a disadvantage, plays to the country s strengths, as it has some of the highest mean average wind speeds in Western Europe. Wind power provides more benefits than just affordable clean energy. The prices of windgenerated electricity are stable and not subject to the price volatility of fossil fuels. Additionally, since it is inexhaustible, wind offers long-term energy security that electricity Renewables 2012 Global Status Report; REN21 Renewable Energy Policy Network Alternatives 4.5

9 derived from non-renewable fossil fuels cannot. A frequent misunderstanding related to wind is the implication of its variability. In fact, with modern meteorology, wind is very predictable over the time scales relevant for balancing the electricity system. It is also important to distinguish between capacity and production. Capacity is the amount of installed power in a region, and is measured in MW. Production is how much energy is produced by that capacity, and is measured in MWh. While wind power does not replace an equal amount of fossil-fuel capacity, it does replace production for every MWh that is produced by a wind turbine, one MWh is not produced by another generator. The carbon penalty for having additional conventional plant on reserve duty to compensate for the variability of wind (which is in any case usually predictable) is very small. Increasing the proportion of wind power in the electricity system does not require greater back-up capacity, as is often believed, but it does slightly increase the cost. The greater the proportion of wind on the grid the lower its capacity value and the lower the quantities of conventional technology it displaces. Nevertheless it continues to reduce carbon emissions ALTERNATIVE SITES Context The criteria applied in determining site suitability for wind energy development include wind resource, established and future land use, environmental conservation designations, ease of access, proximity to electricity grid and ease of site development. A number of siting criteria are applied. These are generic in nature but are intended to be flexible in relation to location of a proposed project, i.e. the acceptability of scale and type of development is dependent on location and land use characteristics of the area. The general criteria for sites considered suitable for wind farm development are as follows: Estimated wind speed of at least m/s at hub heights up to 100m Proximity to a connection point with the national electricity grid. Reasonable road access. Terrain and ground conditions suitable for construction. Low potential for electromagnetic interference. Sufficient distance from residences to minimise amenity impacts. In pursuit of ESB s policy on renewable sources of energy, its companies engaged in wind energy development have identified and evaluated many sites in different counties throughout Ireland for their suitability for wind energy development. Some of the wind energy projects for which planning applications have been made over the past number of years and which are additional to Oweninny are identified in Table 4.3. Alternatives 4.6

10 Table 4-3: Planning Applications for Wind Farms Republic of Ireland Location Republic of Ireland Ballinvully, Co. Mayo Boolynagleragh, Co. Clare Bradlieve, Co. Donegal Cappawhite, Co. Tipperary Castlepook, Co. Cork Coolberrin, Co. Monaghan Croaghbrack, Co. Donegal Garvagh Glebe, Co. Leitrim Grousemount, Co. Kerry High Street, Co. Clare Moanmore, Co Clare Moneypoint, Co. Clare Raheenleagh, Co. Wicklow Rossacurra, Co. Carlow Tullynahaw, Co. Roscommon Woodhouse, Co. Waterford Grouselodge, Co. Limerick Location Northern Ireland Carrickatane, Co. Derry Clunahill, Co. Tyrone Crockdun, Co. Tyrone Eglish, Co. Derry Gortmonly, Co Derry Meenakeeran, Co. Tyrone A key component of Bord na Móna s corporate strategy is to actively diversify into renewable energy particularly into wind energy generation development. It was involved in developing Ireland s first commercial wind farm at Bellacorick in 1992 and is the majority shareholder in this farm since It continues to operate and maintain this farm as it has done since its commissioning. Bord na Móna is currently constructing two wind farms in the Midland region with installed capacities of 80 MW and 40 MW. The sites for these farms consist of cutaway and cutover peatland and site conditions, both of the peat and underlying soils, are similar to those at Oweninny. The turbines being installed in both sites are 3 MW capacity and have blade tip heights of 150m. Bord na Móna has other sites with significant electricity generating capacity in the grid connection application process and with its landbank of some 80,000 ha has identified further sites that can contribute to either the domestic electricity market for renewable energy or the emerging export market. These sites are spread in particular throughout the midland counties where the majority of the Bord na Móna landholding is located Site Suitability Wind Speed Wind speed, on which the power achieved is highly dependent, is critical to the viability of wind farm developments. The power available from the wind is a function of the cube of the wind speed. All other things being equal, a turbine at a site with an average wind speed of 5 m/s will produce nearly twice as much power as a turbine at a location where the wind averages 4 m/s. Doubling the wind speed increases the power output eightfold, Alternatives 4.7

11 whereas doubling the turbine site area only doubles the power. In this regard, the windiness of the site is a key development parameter. Wind classes determine which turbine is suitable for the normal wind conditions of a particular site. These are mainly defined by the average annual wind speed (measured at the turbine s hub height), the speed of extreme gusts that could occur over 50 years, and how much turbulence there is at the wind site. The three wind classes for wind turbines, are defined by an International Electrotechnical Commission standard (IEC), and correspond to high, medium and low wind. Table 4-4: Wind Classification Turbine Class IEC I IEC II IEC III Annual average wind speed 10 m/s High Wind 8.5 m/s Medium Wind 7.5 m/s Low Wind Extreme 50-year gust 70 m/s 59.5 m/s 52.5 m/s Turbulence Classes A 18% A 18% A 18% Monitoring of wind speed has shown that long-term wind speeds at Oweninny classify the site as falling within IEC Class II at a high level. Thus, subject to adequate turbine height, an economically viable wind farm is feasible at this site Size and Topography of Site The site must be of sufficient size to accommodate a wind energy development that is commercially viable to the developer. A large open site is required for the siting of wind turbines and wind turbines require sufficient distance between each other to ensure that the blades of one operating turbine will not interfere aerodynamically with the wind take of adjacent turbines. In addition, proximity of residences in the context of protection of residential amenities is a significant factor in site selection. At Oweninny, turbines are a minimum of 1 km from any residence. The local topography at any wind farm site should be such that the wind that crosses the site does not become overly turbulent. The site at Oweninny is suitable on grounds of its size and local topography Other Factors The other favourable characteristics of the Oweninny site in relation to wind energy generation include the following: Ground Conditions: The ground conditions are suitable for civil engineering construction. Established and Future Land Use: The site is already the location for the country s first commercial wind farm. Furthermore it also already has planning permission for a wind farm layout of 180 wind turbines. The land comprises cutover and cutaway bog with some areas undergoing rehabilitation to enhance ecology on the site. Existing land uses will not be affected and the proposed development will not compromise alternative future land uses. Environmental Impacts: While some minor impacts are inevitable, the construction of a Alternatives 4.8

12 wind energy project is fully compatible with the existing heavily modified environment at the site. The site has also been designated for wind energy development in the Mayo County Council Renewable Energy Strategy Renewable Energy Strategy The site is designated as Priority Area for wind energy development in the Mayo Renewable Energy Strategy Previous Assessments of Site Suitability The Planning Permission granted on appeal by An Bord Pleanála indicates that this site is suitable for wind energy development Mayo County Council The Planning Consent on the previous application (Planning Register Reference P01/2542) noted as follows: Having regard to: a. National Policy with regard to development of sustainable energy sources; b. The general suitability of the site for a wind powered electricity generating facility due to the wind resource available; c. The nature and extent of existing land use and the proposed re-use of industrialised peat workings; d. The Guidelines for Windfarm Development published by the DoEHLG, September 1996, e. The nature of the landscape; f. The proximity of a number of European sites as defined in the Planning and Development act 2000 and g. The need to ensure adequate separation distance of the proposed turbines from any inhabited dwelling. It is considered that, subject to compliance with the conditions set out in the Second Schedule, the proposed development would not be unduly detrimental to the area, would not adversely affect the integrity of European Sites in the vicinity, would not seriously injure the visual amenities in the area, would not seriously injure the amenities or values of residential properties or farms in the vicinity or be otherwise contrary to the proper planning and development of the area An Bord Pleanála The Inspector s Report on the previous application (An Bord Pleanála Reference R ) recommended as follows: Having regard to: a. The national policy with regard to development of sustainable energy sources; b. The guidelines issued by the Department of the Environment, Heritage and Local Government in 1996 on Windfarm Development c. the nature of the landscape; Alternatives 4.9

13 d. the location of suitable ESB apparatus for power connection e. the available infrastructure associated with the existing windfarm and f. the separation distance of the proposed turbines from any inhabited dwelling. It is considered that, subject to compliance with the conditions set out in the Second Schedule, the proposed development would not seriously injure the visual amenities or landscape character of the area, would not seriously injure the amenities or property values of residential properties or farms in the vicinity, would not be prejudicial to public health or be otherwise contrary to the proper planning and development of the area. The Inspector s assessment was upheld by the Board Summary The site at Oweninny is a suitable site for wind energy development and is designated within the Mayo Renewable Energy Strategy as a Priority Area for wind energy development ALTERNATIVE CONFIGURATIONS AND LAYOUTS General Approach The objective of the development is to maximise the sustainable wind energy capture of what is a very suitable site for wind energy development without causing significant adverse environmental impacts. Wind turbine technology offers a range of power ratings from a few kilowatts (kw) up to several Megawatts (MW or thousands of kw). The possibility of installing a larger number of these smaller turbines exists as the site holds planning permission for a wind farm development comprising 180 wind turbines of a size that would produce between 1.5 and 2.5 MW each. However, it is believed that an arrangement of a greater number of smaller capacity machines offers no significant advantages in visual impact terms and that visual impact is minimised by installing larger but fewer wind turbines. From an aesthetic point of view, larger wind turbines offer an advantage in the landscape because they generally have lower rotational speed than smaller turbines. Large turbines therefore do not attract the eye in the way that faster-moving objects generally do. Wind turbines have generally grown taller and more powerful. Rapid developments in technology have lead to turbines of up to 7.5 MW capacity (Enercon -126) now being commercially available. The deployment of larger wind turbines is also reflected in countries, such as Denmark, that have well established wind energy networks. New, more efficient and higher rating turbines are replacing older turbines. There is also an industry trend to equip turbines with increasingly larger rotors, e.g. Siemens have developed a 3.6 MW turbine with 120m rotor diameter and a 6MW turbine with 150m rotor diameter for offshore wind farms. Turbines of approximately MW capacity as proposed are now readily available and many manufacturers are now offering turbines of this size. They are intrinsically more efficient than smaller machines and are usually able to deliver electricity at lower cost. This is because the costs of foundations, access tracks, electrical grid connection plus a number of components in the turbine, e.g. electronic control systems, are largely independent of the size of machine. Key advantages are as follows: Alternatives 4.10

14 The minimum number of turbines is deployed to generate the highest energy output. The minimum development footprint is required as fewer turbines need to be deployed to fulfil grid connection capacity. A development of lower capacity would be wasteful of resources at a site capable of sustaining a project of the proposed size with minimal increased impact on the local environment Alternative turbine heights Different turbine heights have also been assessed as part of the landscape and visual impact assessment, see Chapter 11. Four Zone of Theoretical Visibility (ZTV) maps were produced and used as a tool to compare the visual effects of two different turbine height options within the study area. The following turbine dimensions were compared: 120m hub height 176m blade tip height and 100 hub height 150 blade tip height Very little difference between these two options in terms of the extent of visibility was observed. The larger turbines will appear slightly taller than the smaller turbines in short to middle distance views within a radius of up to 15km from the wind farm site. The taller turbine option will result in slightly more areas experiencing visibility of the wind farm in middle and long distance views to the east, north and west of the wind farm site. Therefore in conclusion, the taller turbine option results in slightly more areas experiencing visibility of the wind farm. However, where views are available, there would be no significant difference in the visual effects of the two options that were assessed. Similarly, there is no significant difference in the landscape effects of the two assessed turbine height options Approved and Proposed Layout Approved Layout The arrangement of the turbines on the site initially envisaged a development comprising 210 wind turbines in a fixed grid layout and this was the basis for the application for Planning Permission (Ref.01/2542) to Mayo County Council in This layout arose from consideration of a number of criteria, as follows: Existing linear uniform drainage network on the site Land ownership boundaries and locations of residences within the surrounding area, Critical spacing and accepted good design practice, taking into account site topography, predicted wind speeds and prevailing wind direction, wind turbulence and wake effects of one turbine on another. The turbines must be a minimum distance apart and this accounted for the extent of the land area required to accommodate the number of turbines of the size and type proposed. Spacing of turbines takes into account the direction of the prevailing wind, Alternatives 4.11

15 which is from the quadrant south-west through north-west. There are different separation requirements in relation to the alignment of turbines with a greater separation being necessary in the direction of the prevailing wind as opposed to perpendicular to it. The layout adopted represented a compromise between the above factors, taking into account the necessary separation of turbines to minimise energy losses through wind shadowing of upwind turbines. Ecology, noise and shadow flicker were also assessed and were primary considerations in turbine siting. This lead to a layout comprising 210 turbines, subsequently reduced to 180 turbines, which was the basis on which planning permission was granted on appeal by An Bord Pleanála Development of Proposed Layout The proposed layout of 112 wind turbines in a non uniform pattern was arrived at following an extensive consultation phase and taking into account the constraints identified as a result of the previous planning process on the site. Initial modelling indicated a wind farm layout that would accommodate 117 larger wind turbines. A constraints map (see Figure 4-4) was prepared showing set back distances from site boundaries and ecological features and this was subsequently used in the modelling of the wind farm to determine an initial optimum layout for wind energy capture. The initial constraints map was based on consideration of the planning history of the site. A revised layout comprising 112 wind turbines was developed based on the following Planning history at Oweninny and the conditions of permission (Ref PL ) Minimum distance of 1,000 m from wind turbines to the nearest occupied dwelling Minimum distance of 100m from wind turbines to the Oweninny River, the Owenmore River and their primary tributaries on the ground, Minimum distance of 100m from wind turbines to designated SAC, SPA, NHA and pnha area Minimum distance of 100m from wind turbines to the site boundary Initial consultations with local stakeholders and Mayo County Council Technical advances in wind turbine technology that have seen larger turbines becoming the industry standard. Analysis of site specific wind data to determine the wind rose for the site and consideration of the prevailing wind direction based on four temporary meteorological masts on the site Noise modelling to ensure compliance with a noise level of 43 db LA 90 at the nearest noise sensitive receptor, see Chapter 7. Site visits by the project team. Historical bird monitoring on the site by the ecological team Alternatives 4.12

16 Field Survey influence on the design Ecological, Noise, Cultural Heritage and geotechnical assessments were also undertaken at all structure sites to identify additional constraints on the ground. These included: Results of avifauna surveys undertaken at the site. Results of habitat surveys undertaken on site Result of the hydrogeology study on the Bellacorick Iron Flush as requested by NPWS Results of geotechnical investigations and field testing that determined peat depths and bearing capacity within the site. Cultural Heritage evaluations on site Five wind turbines were omitted from the original design of 117 wind turbines. Three of these were located north of Lough Dahybaun and were omitted due to the presence of winter roosts for Hen Harrier (see Section 6 Ecology). A further two wind turbines were omitted for geotechnical reasons. Geotechnical investigation and ecological assessment of access track routes also resulted in minor realignment of these routes to areas of lower peat depth and to avoid wet ground. Proposals were refined on an iterative basis to ensure that areas of deeper peat were avoided and the layout was progressively modified to identify final locations of turbines, access tracks substation, O&M building and Visitor Centre locations Figure 4-5 shows the original planning approved layout of 180 wind turbines and the modelled layout proposed at the scoping stage of the development. This initial layout of the wind farm has evolved by taking account of various constraints as they arose during the design. This layout of 112 wind turbines formed the basis of a scoping exercise to key stakeholders and the public to obtain their views and identify any issues of concern Scoping Exercise influence on design A Scoping Report indicating the draft layout comprising 112 wind turbines issued to statutory bodies and stakeholders and was also made available on the project website (see Section 1). Its purpose was to elucidate any constraints or issues which should be taken into account in the wind farm design. Key consultation with Mayo County council, Inland Fisheries Ireland, NPWS, An Taisce and the Irish Peatland Conservation Council were held. The proposed layout provided in the Scoping Report is shown in Figure 4-6. Comments received from stakeholders led to some minor modifications of the proposed layout with respect to some turbine locations. For example the Irish Peatland Conservation Council (IPCC) raised issues with respect to the proximity of turbines to bog remnants and water courses as per Table 4.5. Relocation was identified as necessary to minimise potential significant impacts on bog remnants, flush areas on the site and at one petrifying spring location. Alternatives 4.13

17 Table 4-5: Wind turbine locations identified by IPCC as potential issues IPPC Turbine and issue Distance to Bog Remnant /River (Approx) m T1 Beside remnant 17 T11 Beside remnant/river 66 T16 Beside remnant 21 T18 Beside remnant/river 8 T20 Beside remnant/river 39 T22 Beside remnant/river 45 T32 Beside river 380 T34 Beside remnant/river 7 T42 Beside remnant 24 T52 Beside remnant/river 53 T57 Beside remnant/corridor 23 T86 Beside remnant/river 0 T106 Beside remnant 20 T110 Beside remnant 7 T100 Beside remnant 18 A number of wind turbines were relocated by up to 50m as a result of consultation with the Irish Peatland Conservation Council and following ecological assessment at the turbine and crane hardstand footprints Communication signal corridors Consultation with communication signal providers identified the communication signal corridors across the site. Where turbines were identified within a communication corridor buffer zone they were relocated outside this zone, see Figure Impact of Trees Forest plantation dominates in a small number of areas within the site and keyhole felling will be required at 10 turbine locations to facilitate construction. A hub height up to 120m will significantly reduce the effects of forest plantation on turbine energy yield at potentially affected locations. Turbine hub heights and rotor diameters are particularly crucial for forest areas, because the wind profile in a m wide layer of air directly above the tree tops is massively influenced by the trees acting as obstacles to the wind. This zone is characterised by Alternatives 4.14

18 considerable turbulence and relatively low wind speeds, and is therefore less suitable for profitable exploitation of wind energy. Above this zone, at heights of between 30 m and 60 m, the influence of the trees becomes increasingly negligible. Wind speeds rise while turbulence decreases. Modern wind turbines with hub heights of up to 120 m, which have recently become the standard for such applications, now extend into these high-wind, low-turbulence, layers of air above the tops of the trees. A suitable height for the turbine towers at Oweninny is dependent on a number of factors, as follows: Heights of trees at the time of felling in commercial forestry in Ireland depends on a wide variety of site specific and commercial factors, but generally they may be at an average height of about 20 m. The forestry at Oweninny comprises stands of various ages and heights. With variable rates of growth throughout the site, not all of the forestry at the site will reach full maturity and full height over the projected lifetime of the wind farm. The candidate wind turbines under consideration for deployment at Oweninny will have a rotor blade diameter in the approximate range of m, which represent industry standards. It is evident that wind turbines with a tower height of up to 120 m provide a realistic and viable arrangement for a wind farm at this site Final wind farm design The final wind farm design was arrived at taking into account the set back distances constraints identified at the Oweninny site see Figure 4-8., field survey work to identify further ecological, cultural heritage and geotechnical constraints and in response to issues raised through consultation with key stakeholders, public consultation, the scoping exercise and consideration of potential cumulative effects with other potential wind farm developments in the area. This resulted in the wind farm layout as described in Chapter Micrositing As noted in the DoEHLG Planning Guidelines 2006 (Section 7.3), the precise locations of some turbines may need to be modified as a result of detailed geotechnical investigations. Should this arise full details will be provided to An Bord Pleánala for approval before commencement of construction. Any minor changes to the layout will take full account of the self-imposed constraints regarding minimisation of impacts and set back distances from dwellings, protected areas, streams and rivers and ecologically sensitive areas on the site Proposed Arrangement Other Components Electrical Substation The locations of the electrical substations 1 and 2 were chosen in the context of an optimum location in respect of the expected method of grid connection. This was balanced by the requirement to minimise the amount of 110 kv overhead line to connect the substations to the existing Bellacorick 110 kv station, taking account of separation Alternatives 4.15

19 distances from wind turbines and underground cabling needed to connect the turbines to them. The physical orientation of the Electrical Substation 1 and 2 was also considered in respect of the various possibilities for grid connection, resulting in a layout agreed with EirGrid. The locations for electrical transformer stations 3 and 4 were optimised based on wind turbine layout, however, the final connection route of these two substations to the grid will only be known following completion of the EirGrid Grid West project and associated planning process Meteorological Masts The eight permanent masts were positioned to provide representative data from different parts of the site, taking into account the direction of the prevailing wind. Given the size of the site (50 km 2 ) eight meteorological masts are required to adequately monitor the wind resource across the site. Individual locations for each were chosen to minimise the distance between the mast and the most remote turbines from it. Positioning also took account of proximity to the nearest mast to avoid wind turbulence effects kv overhead Transmission Lines Initially four 110kV overhead line route options between the existing Bellacorick 110kV station and the proposed four new electrical substations in the Oweninny wind farm development were considered. However, as the exact location of the network connection point for phase 3 of Oweninny will not be known until the EirGrid Grid West study is completed and planning permission obtained only the overhead lines route options to Bellacorick for Electrical Substations 1 and 2 have been fully assessed. The following constraints criteria were considered in the identification of route options: Large scale objects such as mountain ranges, large lakes, towns etc., which would obstruct line routing and will thus give a broad indication of likely route options SACs are protected sites under the EU Habitats Directive SPAs are protected sites under the EU Birds Directive NHAs are legally protected from damage under the Wildlife Amendment Act (2000) Ecological features on the ground as identified by the project ecologist The existing transmission and distribution line networks (400kV to 38kV). The line termination points i.e. the start and end point of the line may already be fixed by existing substations. Where this is not the case the new substation site location should be determined from alternative sites taking account of possible environmental impact. A study of the Local Authority Development Plan to identify protected views, scenic and tourist routes, protected landscape categories and areas of high amenity. A study of the plan should also reveal policies and planning guidelines that refer to electrical infrastructure within the county. Alternatives 4.16

20 Archaeological Sites identified from the Sites & Monuments Records (SMR), Department of Environment, Heritage and Local Government (DEHLG) and based on site visits by the project archaeologist. Local landscape impact Two route options (1a and 1b) from electrical substation 1 and four route options (2a, 2b, 2c and 2d) for the overhead line route from electrical substation 2 to Bellacorick and were assessed, see Figure 4-9. Based on the criteria route options were categorised as being Most Suitable, Suitable or Least Suitable as set out in Table 4-6. Table 4-6: Suitability of 110 kv Ovehead line route Code Suitability Most Suitable. From initial review, this line route best avoids all constraints identified. Suitable. From initial review, this line route is somewhat less preferred, as some effects on identified constraints may occur. Least Suitable. From initial review, this line route is the least preferred of the options, as some direct effects on identified constraints are likely to occur. For electrical substation 1 both line routes 1a and 1b were assessed as being viable options, see Table 4-7. However, line route 1a crosses larger sections of bog remnants and also runs close to a water course which adds additional complexity to construction in this area. Line route 1b crosses only one narrow section of bog remnant. This makes line route 1b the more preferable option. Approximately 1.5 km from Bellacorick 110kV station line route 1b would terminate on a cable interface mast and will be cabled underground to the substation to minimise potential potential visual impact on neighbouring dwellings. Table 4-7: Evaluation of potential Line Routes from Substation 1 against Assessment Criteria. Evaluation Criteria Line Route 1a Line Route 1b Ecology Landscape Geology/Water Settlements Cultural Heritage Infrastructure/Utilities For electrical substation 2, line route 2a is the preferred route in terms of the assessment criteria, see Table 4-8 below. This line route was deemed the most suitable as the line is Alternatives 4.17

21 located behind the wind turbines and it is the furthest option from the settlements on the Srahnakilly road. Approximately 1 km from Bellacorick 110kV station Line Route 2 would terminate on a cable interface mast to minimise visual impact potential. Line Route 2b is also a viable option and appears to be a similar option to 2a. It crosses one narrow section of bog remnant. However it does run closer to the settlements on the Srahnakilly Road and for this reason is less preferable. Line Route 2c and 2d are similar options. They would be the least preferred options as they cross wider sections of bog remnants and some water bodies that would cause access difficulties. Line Route 2c and 2d also run in close proximity to the Srahnakilly Road. Table 4-8: Evaluation of potential Line Routes from Substation 2 against Assessment Criteria. Evaluation Criteria Line Route 2a Line Route 2b Line Route 2c Line Route 2d Ecology Landscape Geology/Water Settlements Cultural Heritage Infrastructure/Utilities The most suitable line route to the existing 110 kv substation at Bellacorick identified for substation 1 is route 1a and identified for electrical substation 2 is route 2a. Both line routes terminate 1.5 km and 1 km from the Bellacorick substation where they will be cabled undergrounded to minimise visual impact potential in the area, a cause for concern raised by local people Summary The layout of the wind farm components has evolved by taking account of various constraints as they arose during the design. Eliminating the Lough Dahybaun area from the development footprint enhances protection of fauna and protection of roost areas for hen harrier. At the same time, the wind turbines and access tracks will occupy an even smaller proportion of the overall lands at the site than in the currently permitted development and the remainder will be available for existing or other uses. The proposal represents the most sympathetic arrangement feasible for a wind energy development of 112 turbines on this site taking account of the constraints applying Planning (Wind Energy) Guidelines The Department of Environment, Heritage and Local Government s (DoEHLG s) Planning Guidelines 2006 (Section 6.9) notes that landscape character types provide a useful Alternatives 4.18

22 basis for practical application of siting and design guidelines in relation to wind energy development. In that context six landscape character types were selected to represent most situations, as follows: Mountain moorland, hilly and flat farmland, flat peatland, transitional marginal land, urban / industrial, and coast. Flat peatland is the landscape character type that best describes the site at Oweninny The siting and design guidance for flat peatland address the issues of Location, Spatial extent, Spacing, Layout, Height and Cumulative effect. The characteristics of the revised proposal for Oweninny are in line with the Guidelines. Alternatives 4.19

23 Figure 4-1: Trend in Wind Turbine Sizes Growth of Wind Energy in Ireland 1,800 1, Insatlled capacity (MW) 1,400 1,200 1, Year Figure 4-2: Growth of Wind Energy in Ireland Alternatives 4.20

24 Figure 4-3: Average wind velocity at hub height across the EU. (Extracted from Europe s onshore and off shore wind energy potential. An assessment of economic and environmental constraints. European Environment Agency 2009). Alternatives 4.21

25 Figure 4-4: Oweninny Initial Constraints Map Alternatives 4.22

26 Figure 4-5: Planning approved and proposed wind farm layout Alternatives 4.23

27 Figure 4-6: Proposed wind farm layout issued for Scoping Report Alternatives 4.24

28 Figure 4-7: Communication signal corridors with final proposed layout Alternatives 4.25

29 Figure 4-8: Final Constraints Map Alternatives 4.26

30 Oweninny Wind Farm Figure 4-9: Alternative 110 kv Overhead Line Routes Alternatives 4.27