The overall capacity of all wind turbines installed worldwide by the end of 2017 reached 539 GW.
Wind power generating capacity grew by 10% in 2017, with capacity increasing by 47 GW to reach 539 GW by the end of 2017.
China leads the world in terms of installed wind capacity (164 GW), and in 2017 China recorded the largest addition of new wind capacity (15 GW), followed by the US (6 GW), Germany (6 GW), India (4 GW) and UK (4 GW).
Wind power generation grew by more than 17% in 2017 to reach 1120 TWh, or 4.4% of total world electricity generation. That is more than the total power generation of Russia, the world’s fourth largest power generator. China was the largest wind power producer in 2017, growing by 21% and contributing 30% of global growth in wind power.
Wind has become an important contributor to European electricity generation. In Denmark wind power provided more than 48% of power generation in 2017: and wind power now provides 15% or more of power generated in Ireland, Lithuania, Germany, Portugal, and Spain. Wind has a much smaller share in the US, where it contributed just under 6% of power generation in 2017; and in China, where wind provided just under 4% of power.
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Renewables are calculated to be the quickest developing energy source throughout the following 20 years, with the part helped by falling expenses for wind and solar power, and the energy market drawing closer ‘peak coal’.
The cost of electricity from offshore wind turbines is now cheaper than nuclear energy for the first time, with improved infrastructure and higher voltage cables seeing prices falling by almost half in the past two years, to less than £58 for every megawatt-hour of electricity produced.
Bigger turbines, a growing UK supply chain, and the downturn in the oil and gas industry are among the various factors that have contributed to the falling cost and growing use of offshore wind energy. Latest figures from the National Grid show that around half of the UK’s electricity over the summer months – between 21 June to 22 September – was generated from non-fossil fuel sources.
Meanwhile, according to the US Energy Information Administration, worldwide coal use remains flat, with the coal share of total world energy consumption predicted to decline from 27% in 2015 to 22% in 2040.
Some commentators claim the falling price of renewables and growing demand for these alternative energy sources signals a “new era” for UK energy, which could present opportunities for investors.
Wind power plants
A fixed speed wind turbine commonly employs a three-phase squirrel-cage induction generator (SCIG) that is driven by the turbine via a gearbox and directly connected to the grid, i.e. without an intervening power electronic frequency converter. Thus, the induction generator will provide an almost constant rotational speed, i.e. only varying by the slip of the generator (typically about 1 %). The reactive consumption of the induction generator is compensated by application of capacitors, whereas a soft-starter limits the in-rush current to the induction generator during start- up. At wind speeds above rated, the output power is limited either by natural aerodynamic stall or by active pitching of the blades before the wind turbine is stopped at cut-out wind speed, commonly 25 m/s.
Variable speed operation opens for increased efficiency and enhanced control. The variable speed operation is commonly achieved either by controlling the rotor resistance of the induction generator, i.e. slip control (Type B), or by a power electronic frequency converter between the generator and the grid (Type C or D). Slip control is offered by Vestas only in what they call OptiSlip, and is mainly marketed in the USA where foreign sales of wind turbines with frequency converters are hindered by patent issues. The variable slip concept (OptiSlip) yields a speed range of about 10 %, whereas application of a frequency converter opens for larger speed variations. All variable speed concepts are expected to yield quite small power fluctuations and especially during operation above rated wind speed. They are also expected to offer smooth start-up. Hence, the basic difference between the three variable speed concepts in relation to power quality is that Type B does not have a power electronic converter and thus have reactive capabilities as a fixed speed wind turbine, whereas Type C and D has a converter that offers dynamic reactive power control. The reactive capabilities of Type C and D may differ as the Doubly-Fed Induction Generator (DFIG) concept of Type C uses a converter rated typically about 30 % of the generator and not 100 % (or more) as the case is for the Type D concepts. The grid side of the converters of all major wind turbine suppliers offering Type C or D concepts are all based on fast switching transistors and is hence not expected to emit over-harmonic currents that may significantly distort the voltage waveform. The converters are also full bridge meaning that the reactive power can be controlled independently of the active power output (within the apparent rating of the converter).
It will be impressive as an engineering feat, but the significance of growing turbine size goes well beyond. Bigger turbines harvest more energy, more steadily; the bigger they get, the less variable and more reliable they get, and the easier they are to integrate into the grid. Wind is already outcompeting other sources on wholesale energy markets. After a few more generations of growth, it won’t even be a contest anymore.