FIGURE 1.8 Evolution of wind turbine rotor diameter and power between 1980 and 2010.
systems increased the production of wind turbines. A picture of how the wind turbine diameter and power increased in the last 25 years is shown in Figure 1.8. It is anticipated that by 2010, machines with diameters of 180 m that are capable of producing 8-12 MW will be produced. These are possible today after the recent developments in the carbon fiber-reinforced blade production, which allows the manufacture of long and strong blades with small weight.
In many countries, wind power is already competitive with fossil and nuclear power when the external and social costs are included. The often-perceived disadvantage of wind energy (and solar energy) is that being an intermittent (stochastically varying) source not representing any capacity credit makes the resource of uncertain value for large-scale electricity production; this, however, is not true. Utility studies have shown that wind energy does represent a certain capacity credit, though at a factor of 2-3 lower than the value for nuclear and fossil fuel-fired plants. Therefore, wind energy replaces fossil fuels and saves capacity of other generating plants.
The growth in installed wind power is hampered by a number of barriers. These are public acceptance, land requirements, visual impact, audible noise, telecommunication interference, and various impacts on natural habitat and wildlife. Most of these problems, however, are solved by the installation of offshore wind parks.
Wind energy technology has progressed significantly over the last two decades, driving down capital costs to as low as $1000 per kW. At this level of capital costs, wind power is already economical at locations with fairly good wind resources. Therefore, the average annual growth in worldwide wind energy capacity was over 30% for the last five years. The total worldwide installed capacity reached a level of 59 GW in 2005 (WWEA, 2007). The world's total theoretical potential for onshore wind power is around 55 TW, with a practical potential of at least 2 TW, which is about two thirds of the entire present worldwide generating capacity. The offshore wind energy potential is even larger.
Wind energy can compete with energy from other sources (coal, oil, and nuclear) only under favorable wind and grid conditions. Further decrease in cost will extend the market potential for wind turbine systems considerably. Decrease in the cost of wind energy can be achieved by reducing the relative investment cost, introducing reliability design methods, and exploiting the best available wind sites.
wind ENERGY SYSTEMS TECHNOLOGY
The exploitation of wind energy today uses a wide range of machine sizes and types, giving a range of different economic performances. Today there are small machines up to about 300 kW and large-capacity ones that are in the megawatt range. A photograph of a wind park is shown in Figure 1.9.
The technology of the wind turbine generators currently in use is only 25 years old, and investment in it so far has been rather modest, compared with other energy sources. Nearly all the wind turbines manufactured by industry are of the horizontal axis type, and most of them have a three-bladed rotor. However, for some years now, machines have been constructed with two blades to reduce the costs and prolong the life of machines by making them lighter and more flexible by reducing the number of high-technology components.
Europe installed 7588 MW of wind turbines in 2006, valued at 9 billion Euros, an increase of 23% over the installation levels of 2005. The market for European wind power capacity broke new records in 2006, according to annual statistics from the European Wind Energy Association (EWEA). The cumulative wind capacity in the European Union increased 19% to 48,027 MW, which can generate 100 TWh of electricity in an average wind year, equal to 3.3% of total EU power consumption.
For the seventh year in a row, wind is second only to gas-fired capacity (8500MW) in terms of new electricity-generating installations. Germany and Spain continue to attract the majority of investments (last year representing 50% of the EU market), but there is a "healthy trend in the European market towards less reliance on Germany and Spain." In 2002, 680MW of European wind capacity was installed outside Germany, Spain, and Denmark; in 2006, that level was 3755 MW. Excluding the three pioneering countries, this represents a sixfold increase in the annual market in four years. The figures clearly confirm that a second wave of European countries is investing in wind power.
It is clear that this investment is due to the strong effect of the EU Renewable Electricity Directive passed in 2001, which urges the European Commission and the council to introduce safeguard measures that ensure legal stability for renewable electricity in Europe. These figures confirm that sector-specific legislation is the most efficient way to boost renewable electricity production.
Germany installed 2233 MW of turbines in 2006, 23% more than in 2005, and passed the 20,000MW mark. Spain was the second largest market, with 1587 MW, while France moved into third place from sixth by installing 810 MW during 2006. Portugal installed 694 MW of new capacity, more than in any previous year, and is constructing another 1063 MW on its way to meet the government target of 3750 MW by 2010. The United Kingdom installed 634MW in 2006, and its total installed capacity increased by 47%, while Italy installed 417 MW and Ireland set a new record with 250 MW, increasing its total capacity by 50%. Wind energy in the new EU-12 countries tripled to 183 MW last year, mostly in Poland, Lithuania, and Hungary. Bulgaria installed 22 MW, while Romania installed 1.3 MW of turbines. Eight countries in the EU now have surpassed the 1000MW threshold of wind capacity.
The investments made to achieve this level of development have led to a steady accumulation of field experience and organizational learning. Taken together, many small engineering improvements, better operation and maintenance practices, improved wind prospects, and a variety of other incremental improvements have led to steady cost reductions.
Technological advances promise continued cost reductions. For example, the falling cost of electronic controls has made it possible to replace mechanical frequency controls with electronic systems. In addition, modern computer technology has made it possible to substantially improve the design of blades and other components.
The value of wind electricity depends on the characteristics of the utility system into which it is integrated, as well as on regional wind conditions. Some areas, particularly warm coastal areas, have winds with seasonal and daily patterns that correlate with demand, whereas others have winds that do not. Analyses conducted in the United Kingdom, Denmark, and the Netherlands make it clear that wind systems have greater value if numerous generating sites are connected, because it is likely that wind power fluctuations from a system of turbines installed at many widely separated sites will be less than at any individual site.
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