Kevin Conway

Offshore Wind Energy in Ireland

Abstract

Throughout the last number of centuries, almost all the power that has been generated by humans has come from non-renewable sources. We are rapidly approaching the time when supplies of these resources will peak and therefore it is necessary to seek an alternative means of energy generation.

For many years, renewable energy has been seen as the replacement for fossil fuels. The aim of this report is to investigate offshore wind energy, a type of renewable energy, and determine if it is viable source of energy production in Ireland. It details the theory behind the generation of wind energy and examines Ireland's potential to so in the seas around its coastline. There is currently one offshore wind farm in Ireland however several more are planned, all on a scale comparable the world leaders in offshore wind energy generation.

The findings of the report show that Ireland's geographical location makes it a suitable candidate for the generation of wind energy, and that current trends show that such generation of energy can be economically viable.

Introduction

At present, the world has an over-reliance on non-renewable sources of energy such as coal and oil. Over the last century the earth’s fossil fuels have been used up quicker than they can be produced meaning that its supply has been greatly depleted. In 2009, 87% of the world’s total primary energy supply was derived from non-renewable sources [1]. We are now approaching the point at which supplies of fossil fuels will peak and then go into decline, meaning that dependency on these sources of energy is no longer a viable option.

This usage of non-renewable sources has a detrimental effect on the earth’s environment. Terms such as ‘global warming’ and ‘the greenhouse effect’ have been commonplace for many years in reference to the harmful effects of burning fossil fuels, yet it is only in the last decade and a half that governments around the world have sought to find a solution to the problem. Treaties and agreements such as the Kyoto Protocol which was adopted in 1997 have led us to a situation where an alternative to fossil fuels must be sought.

Figure 1. 2009 fuel shares in world total primary energy supply (TPES). [1]

Over the past number of decades, the percentage of the world’s total primary energy supply made up by renewable sources of energy has been increasing and it is becoming obvious that this is where out future energy supply must come from.

Renewable energy is energy which is provided by three main processes - nuclear fission in the sun, gravity and radioactive decay of the earth’s crust. From these three processes, all types of renewable energy (solar, wind, hydroelectric, biomass, geothermal) are derived. This type of energy causes little or no damage to the earth’s environment. In 2009, only 13% of the earths total primary energy supply was renewable. Figure 2 shows that of the largest source of renewable energy comes from biofuels, something that is made widespread use of in developing countries.

It is important to make use of renewable energy for a number of reasons. One of the most beneficial reasons is that renewable energy has very little impact on the environment when compared to fossil fuels. Combustion of fossil fuels releases gases such as carbon, nitrogen and sulphur into the environment, contributing to climate change and causing phenomena such as acid rain. Usage of renewable energy also creates employment in the regions where it is generated. Jobs can be created in the construction of power plants etc.,as well as in the everyday running and maintenance of them, something which is of great benefit to both the local and national economies. [2,3]

Figure 2: Breakdown of renewable energy section of 2009 world total primary energy supply [1]

Renewable Energy in Ireland

Overview

Ireland has a very high dependency on imported energy. In 2009, over 90% of Ireland’s energy was imported from other countries [1]. This can potentially be very dangerous as it leaves the country vulnerable to the uneven distribution of fossil fuels between countries, to natural disasters and even to the possibility of political or security issues interrupting its supply. Figure 3 shows that more than 50% of Ireland’s energy requirements come from oil and only 3.1% from renewables. Such a dependency is no longer viable, given that the point of peak oil is approaching and that the current economic and political climate is far from stable. Over the past number of years, the price of oil has continually risen due to wars and conflicts in various regions in the world and this trend is unlikely to change. Renewable energy has the potential to reduce our vulnerability to such events and increase the security of the country’s energy supply. Both the Irish government and the European Union have recognised this and have set targets with the aim of reducing our dependency on fossil fuels and increasing our use of renewable energy sources.

Figure 3: Ireland’s total primary energy requirements, 1990-2009 [4]

At the European Union’s energy summit held in 2007, the leaders of each country signed an agreement stating that their countries would source 20% of their energy requirements from renewable energy sources by 2020. As a result of this agreement, a EU Renewable energy directive 2009/28/EC has set out individual and legally binding targets for each member state in order to keep them on course to meet their targets. The target set out for Ireland was to have 16% of all energy consumed come from renewable sources by 2020.

Figure 3 shows that the main sources of renewable energy in Ireland are hydroelectric and wind. Hydroelectric power has been utilised in Ireland since the 1920s however wind energy was not introduced until the mid 1990s. Since then, its contribution to Ireland’s renewable energy supply has increased rapidly, to the point that it contributes almost as much as hydroelectric power.

Figure 4: Ireland’s renewable energy sources (1990-2009) [1]

Wind Energy

As shown in figure 5, Ireland has one of the best wind energy resources in europe and indeed the entire planet. This has been a major reason as to why wind energy has risen in prominence in the country. The current installed and grid connected wind capacity in Ireland is 2010.25 MW which will generate approximately 4,743,339 MWh per year, assuming that the electricity generation from wind generation is at 31% of its maximum capacity [5]. According to a report into residential energy consumption conducted by the Sustainable Energy Authority of Ireland in 2008, the average household consumes 5.591 MWh of electricity per year. This means that wind energy can account for the energy consumed by approximately 753,000 households each year. [6]

Figure 5: Wind resources at 50m above ground level for five different topographical conditions. 1) Sheltered terrain, 2) Open plain, 3) At a coast, 4) Open Sea and 5) Hills and ridges. [7]

Theory

The principal behind the generation of wind energy is a simple one. The wind’s energy is the kinetic energy of air particles in motion and is given by:

where m is the mass of the air and v is its velocity. This kinetic energy can be used to turn the blades of a wind turbine. The rotating turbine blades are then used to turn a generator which in turn converts the kinetic energy to electrical energy. The power available in the wind stream flowing across the rotor of a wind turbine is given by:

where ρa is the density of the air, AT is the cross-sectional area of the rotor and V is the velocity of the air stream. [8]

Figure 6: A section of the air stream moving towards a wind turbine [8]

As we can see from the above equations, the power available in the wind stream is greatly increases as a result of increasing wind speed. Wind speed is dependent on a number of factors:

Geography

Wind speed varies depending on location. It is particularly high around coastal areas due to sea breezes, as well as the temperature differential between the land and the surrounding water. Valleys are another area where wind speed is as act like a natural wind tunnel.

Height

The speed of the wind varies with it’s height above ground level. This is because friction between the air flow and the rough surface of the ground causes the flow to become turbulent, thus slowing it down. Therefore as we move higher above the ground, the wind speed increases because the air flow remains somewhat laminar in comparison to that at ground level.

Climate

A region’s climate also plays a part in the speed of the winds found in that location. Equatorial regions receive a large amount of solar radiation which heats the surrounding air, reducing its density in the process. This warm air rises and moves away from the equator. Figure 7 shows us that the regions with the greatest wind speed are located further away from the equator, mainly in coastal regions where the warm air is cooled by the sea and forced to sink closer to the land.

Figure 7: Annual global mean wind power at 50m above the surface [9]

As wind speed is such a critical factor, it is important that the turbines are located in areas where they are exposed to winds of high speed. Figure 8 Shows that the majority of Ireland’s wind energy is generated in counties which border the sea, indicating that the country’s coastline has much potential to be developed for wind farms.

Figure 8: Wind energy generation per county in Ireland [10]

Offshore Wind Energy

Overview

Figure 9: Distribution of the offshore wind in operation in the different countries at the beginning of the year 2011 [13]

Offshore Turbines

The most common type of offshore wind turbine is the horizontal axis turbine, normally with a large generating capacity. Offshore wind turbines are similar in appearance to their onshore counterparts. Both have their rotor shaft and electrical generator at the top of the tower, as well as a gear box which turns the slow rotation of the rotor blades into a quicker rotation which is more suitable to the generation of electricity. However there are several differences between the two types of turbine due to the difference in their operating conditions.

As they operate at sea, the towers which support the rotors and generators must be strengthened in order to cope with the force of the waves impacting against them and also to deal with the increased wind speed. Some of the components of the rotors, generators and gear box must also be modified to protect them from the sea spray and air. As well as these modifications, offshore wind turbines have automatic greasing systems which help to reduce the amount of maintenance needed, and also have heating and cooling systems which are used to maintain the temperature of the gear oil. [12]

The most significant difference between onshore and offshore turbines is with their foundations. Figure 10 Shows that there are three types of foundations that are used in the construction of offshore turbines.

Figure 10: Different types of offshore wind turbine foundation [16]

• Monopile Foundations

This type of foundation involves supporting the tower with a single pile which is driven into the seabed. This type of foundation causes minimal impact the environment due it’s single pile nature and is generally used in water depths of less than 30m. [12]

• Gravity Base Foundations

This involves the connection of a pile to a large mass, known as a gravity base,which rests upon the seabed. The function of the mass is to prevent motion of the tower in conditions of high sea or winds. The size of the gravity base can be increased or decreased to suit the design of the tower. [12]

• Tripod Foundations

Tripod foundations get their name as this method involves stabilising the tower to by pinning it to a number of smaller piles embedded into the seabed. Tripod foundations can be used in water depths of greater than 30m. [12]

Connection to the National Grid

Ireland’s national grid is controlled by Eirgrid, a state owned company. Eirgrid have recently embarked upon an extensive plan to develop and upgrade their electricity transmission network to deal with the country’s increasing energy demands. Figure 11 shows that the grid’s capacity has gone largely unchanged for the last 25 years, even though electricity demand has seen a growth of almost 150%. The Grid25 project aims to build 1,150 km of new power lines and upgrade 2,300 km of existing power lines which will double the current capacity of the grid, enabling Ireland to meet it’s renewable energy targets and helping to improve the security of the country’s energy supply. [17,18]

Figure 11: Electricity demand growth in Ireland 1985-2025 [17]

One of the main reasons for this grid upgrade is to cater for the significantly higher levels of renewable power generation that are planned for the future. A large number of the areas suitable for the construction of renewable energy projects are situated in areas where there have previously been no energy developments. Eirgrid has recognised that it will not be possible for Ireland to fully utilise the natural resources that were identified in the offshore renewable energy development plan unless the facilities to do so are put in place and has therefore accounted for this in the Grid25 project. [17]

In 2010, Eirgrid published the results of it’s Gate 3 Incremental Transfer Capability (ITC) program. The purpose of this program is to determine the amount of extra power that can be accommodated by the grid without surpassing it’s thermal limits [19]. The results of the program account for the current level of expansion of the grid as part of the Grid25 project. Figure 12 shows us that with the first 8 years of the program (2010-2017), a total of 601.5 MW of offshore wind is due to be connected to the grid with 364 MW coming from the Dublin Array offshore wind farm 237.5 MW coming form the Oriel offshore wind farm. [20]

Figure 12: Gate 3 ITC results relating to offshore wind [19]

Current Projects in Ireland

There currently four offshore wind projects in Ireland however none of these projects have so far secured both the foreshore lease required for a development that requires exclusive occupation of the foreshore, and grid connections required to proceed with the projects. [21]

Dublin Array

Dublin Array is an offshore wind development which is planned for the area around Dublin Bay. The project plans for 147 turbines to be constructed on the Kish and Bray sandbanks which are located 10 km off the coast of Dublin and Wicklow. The development has a potential installed capacity of up to 520 MW, 364 MW of which has already been granted a connection to the national grid through the Gate 3 ITC program. A foreshore lease has yet to be granted for the project however construction on the sites is planned to begin in 2014, with energy production intended to commence the following year. [22]

Oriel Wind farm

The Oriel wind farm is an offshore development planned for an area which is located 22 km off the coast of Dundalk in County Louth. Oriel Windfarm Ltd. intend to construct 55 turbines, with a maximum capacity of 330 MW and the potential to supply energy to 220,000 homes, making it the ninth largest power plant in the country. Once a foreshore lease has been obtained, construction of the farm is intended to take place in 5 phases, with 11 turbines constructed in each phase. These 5 phases would take place over a 5 year period creating approximately 490 jobs, 40 of which would become permanent operational and maintenance staff. As with the Dublin Array, the Oriel wind farm has been granted a connection to the national grid. [23,24]

Codling Wind Park

In 2005, a foreshore lease was granted for the construction of 220 offshore wind turbines and the accompanying structures on a shallow sand bank approximately 13 km off the coast of Greystones. The development has the potential to have up to 1,100 MW of installed capacity however it is currently awaiting a connection to the national grid before construction begins. [25]

Sceirde Wind Farm

The Sceirde Wind Farm is a planned 100 MW installed capacity development of twenty offshore wind turbines located approximately 2.8 km north-east of Sceirde Mór, an island which is 5 km off the Galway coastline. The project is due to receive a grid connection as part of the Gate 3 ITC program but it still awaiting a foreshore lease to be granted. [26]

Current Projects in Europe

Europe is the world leader in terms of offshore wind energy generation. As shown in figure 9, the United Kingdom has the largest installed capacity in Europe. The UK’s installed capacity is set to increase by more than 200% within the next year due to a number of projects which have been recently completed and others which are currently under construction. In comparison, the proposed offshore developments in Ireland compare favourably with those in the UK, considering the difference in populations. [27]

The Thanet Offshore Wind Farm was completed at a cost of £780 million, having begun construction in November 2008. The site consists of 100 wind turbines and has a total installed capacity of 300 MW, making it the largest offshore wind farm in the world. It is located located approximately 12 km off Foreness Point which is the most easterly point of Kent, and has the potential to supply energy for 200,000 homes. [28]

However Thanet will not hold the title of world’s largest wind farm for long as two larger installations are due to come online in 2012. The Greater Gabbard offshore wind farm is currently under construction 25 km off the coast of Suffolk. 140 wind turbines are to be installed, with a total capacity of 504 MW. As of November 2011, 83 of the turbines have been installed and have exported electricity in tests. It is expected that all turbines will have been installed by the end of 2012 and that the site will have the potential to power approximately 530,000 homes. [29, 30]

The London Array project is a wind farm which is currently under construction in the outer Thames Estuary. It consists of 175 wind turbines with a total capacity of 1 GW, which will make it twice as large as any other offshore wind farm in the world. When completed, the London Array will generate enough electricity to power on quarter of all off the homes in Greater London. [31]

Economic Benefits

Offshore wind in Ireland has developed more slowly than its onshore counter part and many have argued that this is due to higher initial capital costs deterring investors [32]. In 2008, the National Offshore Wind Association of Ireland commissioned Indecon International Economic Consultants to prepare a report analysing the costs and benefits of further offshore wind developments in Ireland.

Their report was based on a 1000 MW installation on the East coast of the country. Figures were calculated over a 15 year period commencing in 2012, as it was assumed that this was to be the likely start point for any such development. The findings of the report indicate that if recent trends in oil and other fossil fuel prices continue, then further offshore wind development will become economically viable. However in the unlikely event that the opposite were to happen and fuel prices were to fall, then they would be less economically viable and could fall below the break-even point. [32]

Figure 12: Breakdown of estimated overall net-cost benefit of 1,000 MW of additional offshore wind capacity (€m) [32]

Conclusion

The aim of this report was to investigate whether or not offshore renewable energy is a viable source of energy production for Ireland. From the information provided in the report, it is clear that it can be. There is a huge amount of wind resources available in Irish waters which until now, have gone largely untouched. Major developments have been planned which are on par with the largest offshore wind farms in the world, and the national grid is currently being upgraded in order to facilitate them.

With EU and Kyoto Protocol targets to be met in the near future, the potential to generate offshore wind energy needs to be exploited as much as possible. Not only would this type of energy generation help Ireland in achieving the targets set out for it, but it would also increase the security of its energy supply and help to reduce the country's dependency on fossil fuels.

References

[1] International Energy Agency, Renewables Information 2011, 2011

[2] http://www.seai.ie/Archive1/Files_Misc/REIOEnergyOverview.pdf (accessed 12^th November 2011)

[3] http://www.seai.ie/Archive1/Files_Misc/REIOREFactsheet.pdf (accessed 13^th November 2011)

[4] M. Howley et al., Energy in Ireland 1990-2009, Sustainable Energy Authority of Ireland, 2010

[5] http://www.iwea.com/index.cfm/page/faqs (Accessed 20^th November 2011)

[6] http://www.seai.ie/News_Events/Press_Releases/Energy_in_the_Residential_Sector_FNL.pdf (Accessed 16^th November 2011)

[7] http://www.windatlas.dk/Europe/EuropeanWindResource.html (Accessed 4^th December 2011)

[8] Sathyajith Mathew, Wind Energy: Fundamentals, Resource Analysis and Economics, 2006, pp 11-12.

[9] Q. Liu et al., Solar and wind energy resources and prediction, Journal of Renewable and Sustainable Energy, 1, 2009

[10] http://www.iwea.com/index.cfm/page/barchart

[11] Offshore Wind Energy Europe, [online], Ready to Power a Sustainable Europe, http://www.offshorewindenergy.org/ (Accessed 15^th November 2011)

[12] V.J. Kurian, C. Ganapathy, Monopile Foundations for Offshore Wind Turbines, 2007

[13] Esteban, M.D. et al., Why Offshore Wind Energy?, Renewable Energy, 36, (2011) p444-450

[14] http://site.ge-energy.com/about/press/en/2003_press/102803a.htm (Accessed December 12^th 2011)

[15] S. O’Sullivan, Study Identifies ‘Huge’ Offshore Potential, The Engineers Journal, 2011, 5, p300.

[16] http://offshorewind.net/Images/Foundations/TodaysFoundations.gif (Accessed 11th December 2011)

[17] http://www.eirgrid.com/media/Grid%2025.pdf, (Accessed 13^th November 2011)

[18] http://www.eirgridprojects.com/grid25/what-is-grid25/, (Accessed 13^th November 2011)

[19] http://www.eirgrid.com/media/Gate%203%20ITC%20Results%202010-2023.pdf (Accessed 14^th November 2011)

[20] Sustainable Energy Authority of Ireland, Strategic Environmental Assessment (SEA) of the Offshore Renewable Energy Development Plan (OREDP) in the Republic of Ireland, 2010

[21] http://www.environ.ie/en/Foreshore/FAQs/, (Accessed 1^st December 2011)

[22] www.dublinarray.com (Accessed 19^th November 2011)

[23] www.orielwind.com (Accessed 19^th November 2011)

[24] http://www.orielwind.com/documents/Vol_I_Non-Technical_Summary/Non-Technical%20Summary.pdf (Accessed 19^th November 2011)

[25] http://www.codlingwindpark.ie/, (Accessed 21^st November 2011)

[26] http://www.fsteo.com/Non-Technical%20Summary.pdf, (Accessed 24^th November 2011)

[27] http://www.renewableenergyworld.com/rea/news/article/2011/01/offshore-wind-booming-in-europe??cmpid=WNL-Friday-January21-2011 (Accessed 6^th December 2011)

[28] http://www.vattenfall.co.uk/en/thanet-offshore-wind-farm.htm (Accessed 6^th December 2011)

[29] http://www.sse.com/GreaterGabbard/ProjectInformation/ (Accessed 6^th December 2011)

[30] http://www.rwe.com/web/cms/en/310134/rwe-innogy/sites/wind-offshore/under-construction/the-proposal/ (Accessed 6^th December 2011)

[31] http://www.londonarray.com/the-project/, (Accessed 8^th December 2011)

[32] http://www.nowireland.ie/pdf/IndeconSummary.pdf, 2008, (Accessed 21^st November 2011)