Potentials, costs and environmental assessment of electricity generation technologies 8 Wind power (onshore and offshore) Karin Treyer (Laboratory for Energy Systems Analysis, PSI) 8.1 Introduction and definitions Wind energy is the renewable energy source with the highest increase in installed capacity worldwide in the last years. The total capacity by the end of 2015 amounted to 435 GW, out of it 12 GW offshore (GWEC 2015, WWEA 2016). This covered about 3-5% of the world’s electricity needs.154 Wind power is supposed to have a huge potential in the electricity supply in many countries, and is supported by manifold governmental incentives. Windmills have been making use of the kinetic energy of wind for centuries now. Starting with pumping water or grinding grain, these mills have developed in the late nineteenth century to produce electricity (Burton, Jenkins et al. 2011). The first wind turbines showed capacities of 5 to 10 kW, developing to a 1 MW turbine in 1941 in Vermont, US.155 The 1980ties came along with intensive research in the wind sector due to increased oil prices, which led to wind turbines of about 4 MW capacity. The latest wind turbines demonstrate capacities of up to 8 MW on- and offshore. 156 The first offshore wind farm was commissioned in 1991 with a total capacity of 5 MW (Burton, Jenkins et al. 2011). In 2015, the largest offshore wind parks are located in the United Kingdom with installed capacities of 500 to 630 MW.157 In the following some definitions are given. The harvest of electrical energy with a wind turbine is possible due to rotation of blades using kinetic energy from moving air. In lingual terms there is a difference between individual wind turbines standing alone and wind farms, which represent an assembly of wind turbines. The wind turbines and farms can be located onshore on firm land or offshore in a body of water. Whereas it is technically more challenging to build offshore plants, stronger wind speeds at such locations can drive higher harvest of energy. The efficiency of a wind farm can be defined as the relation between the energy supplied with the blowing wind and the harvested electrical power. The theoretical maximum power which can be extracted is defined by the Betz’s law to be 16/27 (59.3%) of the kinetic energy of the wind (Betz 1926). However, this maximal efficiency is not reached by modern rotors, which can use up to 50% of the kinetic energy. Losses of other parts of the wind turbine such as gear, generator or transformer have to be subtracted in addition, which reduces the efficiency to around 30%.158 Wind speed and wind supply over the year determine the actual electricity production. The full load (equivalent) hours correspond to the number of hours a wind turbine would have to run at rated capacity in order to produce the amount of electricity delivered in a year. The capacity factor of a wind turbine or park is calculated by dividing these full load 154 http://www.gwec.net/global-figures/wind-in-numbers/, http://www.wwindea.org/new-record-in- worldwide-wind-installations/ 155 http://www.energy.gov/eere/wind/history-wind-energy 156 http://www.windpowermonthly.com/10-biggest-turbines 157 https://en.wikipedia.org/wiki/List_of_offshore_wind_farms 158 http://www.weltderphysik.de/gebiet/technik/energie/gewinnungumwandlung/windkraft/physik-der- windenergie/ 258 Potentials, costs and environmental assessment of electricity generation technologies hours by 8760 hours. The capacity factor varies with location and includes downtime due to ordinary and unforeseen maintenance. Common capacity factors are between 0.1 and ca. 0.55 (IRENA 2012c) with a world average of ca. 23% in 2013 (calculated from (GWEC 2015, IEA 2015c, WWEA 2016)). In general, offshore wind parks show considerably higher capacity factors (up to 0.52159) than onshore wind parks (see chapter 8.4.6). Onshore availabilities are usually around 95%, while offshore availabilities have increased up to 92% to 98% in the past few years (IEA 2013a) (see chapter 8.4.8). 8.2 Wind power worldwide 8.2.1 Status Quo worldwide Key facts and figures and time series of wind power are presented yearly by the Global Wind Energy Council (GWEC), the World Wind Energy Association (WWEA), and other Wind Associations such as the European Wind Energy Association (EWEA) or the American Wind Energy Association (AWEA). According to (WWEA 2016), a total of 435 GW wind capacity was installed by the end of 2015 on the world in around 105 countries (Figure 8.1). Another 60 GW are estimated to be added in 2016 (GWEC 2016). Total electricity production with the installed capacity of 372 GW in 2014 corresponded to 717 TWh, which was ca. 4% of the world’s electricity supply. The share of wind power in the electricity supply of OECD countries went up to 5.3% in 2015, which is 22.9% of the renewable power in these countries (IEA 2016c). The countries with the largest shares of electricity from wind in their production mix in 2014 have been Denmark (41% of domestic production mix), Portugal (23%), Ireland (20%), and Spain (19%) (OECD 2015). Note that the actual share in the electricity consumption mix might be lower if electricity is imported. Out of the 435 GW wind power installed by the end of 2015 worldwide, 12 GW are offshore – half of these are installed in the United Kingdom (WWEA 2015, EWEA 2016). Detailed data for installed capacities in the end of each year 2010 to 2014, growth rate 2014, and installed capacity per capita and per square km are given for all countries in the appendix of this chapter (Table 8.14). The largest market for new turbine capacity in 2015 was China with 33 GW, followed by the USA (8.6 GW, ca. 4000 new turbines) and Germany (4.9 GW). These are also the regions with largest installed capacities: 148 GW in China, 74 GW in the USA, and 45 GW in Germany. Most of the remaining capacity is installed in Europe, which hosts a total of ca. 142 GW (GWEC 2016, WWEA 2016). 159 http://cf01.erneuerbareenergien.schluetersche.de/files/smfiledata/3/1/7/2/7/1/V2BC37NhCFWindDK.pdf 259 Potentials, costs and environmental assessment of electricity generation technologies 12 GW offshore Figure 8.1: World total installed capacity [GW] and world electricity production [TWh] between 1997 and 2015 (OECD 2016, WWEA 2016). No worldwide electricity data are available for 2015 yet. 8.2.2 Projections: Technical potential of wind power worldwide The theoretical worldwide potential of wind power is huge. However, manifold factors narrow down the actual locations where wind energy can be harvested. Examples are too low or too high wind speed, distance to land on the high seas or other water bodies, urban areas, mountains and other regions which are difficult to access, or social and political factors. Figure 8.2 shows an example of the decrease from the theoretical to the practical wind power potential. Archer and Jacobson (2013) define the technical wind power potential to include all areas where it is technically possible to install a wind turbine. This excludes polar regions, offshore locations deeper than 200 m, and mountainous areas above 2000 m. The practical potential then excludes areas with practical restrictions, such as conflicting land and water uses or remoteness, and areas with wind speed lower than 7 m/s, as only high- wind locations are considered in the study. The regions with highest wind speeds are ocean waters, the Sahara desert, the lowest part of Southern America, central parts of Northern America, Himalaya, and parts of the eastern coast of Africa (Archer and Jacobson 2013, IEA 2013a). 260 Potentials, costs and environmental assessment of electricity generation technologies Figure 8.2: Theoretical, technical and practical global wind power potential. Taken from (Archer and Jacobson 2013). Archer and Jacobson (2013) estimate that the practical potential is between 68 and 115 TW, while the global installed electricity demand in 2012 was 2.44 TW. They comment that the practical potential is a theoretical exercise and in any case exceeds the world’s electricity demand if it could be exploited and the intermittency challenge could be solved. The highest potentials are modelled to be in Northern and Western Africa (26-33 TW), former USSR (9- 18 TW), Oceania (5.5-11.6 TW), East Asia (7-11 TW), US (6.5-11 TW), and Eastern Africa (6- 8 TW). As will be shown in chapter 8.4.2, the availability of these potentials varies over the seasons. Further, the regions with the highest potentials are not the regions where high wind power deployment is expected until 2050 (see below). The offshore potential is modelled to be rather low in Archer and Jacobson (2013). The regions with highest potential are the former USSR, South America and the US, Oceania, and OECD Europe. Besides the excluding criteria of seawaters deeper than 200 m, it is not discussed in the paper why the potential is not higher. Depending on such influences and resulting assumptions, projections of installed global wind capacities vary a lot (see Figure 8.3). 261 Potentials, costs and environmental assessment of electricity generation technologies Figure 8.3: Expected installed wind capacity until 2050 modelled by (IEA 2013a, WWEA 2015, GWEC 2016). The GWEC models four different scenarios up to 2050 (of which one intermediate is not displayed), the IEA shows two scenarios up to 2050, while the WWEA only gives an estimate up to 2030. 2DS = 2 degree scenario; hiRen = high renewables scenario. According to the World Wind Energy Association (WWEA 2015), expected global installed wind capacity will be larger than 500 GW by 2017, exceed 700 GW in 2020 and reach 2000 GW in 2030.