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To decrease cost, wind turbine design is also motivated by a desire to decrease materials usage while striving to enlarge turbine size, improve component and system reliability, and to enhance wind power plant functions, [52–54].

Schematic illustration of solar water heating collectors’ global capacity, 2000–2019. Schematic illustration of solar water heating collector capacity by top 10 countries in 2016.

      The three main components of the wind generation system are: (i) turbine which could be vertical or horizontal‐axis, (ii) installation area which could be onshore or offshore, and (iii) application which could be grid connected or stand‐alone. The majority of large wind turbines are up‐wind horizontal‐axis turbines with three blades. The majority of small wind turbines are horizontal‐axis. Developed structures of vertical‐axis turbines are presently utilized in many regions across the globe. They are associated with an aerodynamic energy loss ranging from 50 to 60% at the blade and rotor, a mechanical loss of 4% at the gear, and a 6% electromechanical loss at the generator. The full production efficiency typically ranges from 30% to 40% at wind energy facilities.

Schematic illustration of growth in capacity and rotor diameter of wind turbines, 1985–2016, [52].

      With regard to the reliability of a power system, the power transformation system is of paramount importance when it comes to wind turbines. For large grid‐connected turbines, power transformation systems are categorized into three forms. Fixed‐speed induction generators are well‐known for their stall‐regulated and pitch‐controlled turbines; in these particular arrangements, wind turbines are net consumers of reactive power that must have been given by the power network. Advanced turbines replaced this with variable‐speed machines. Two arrangements are recognized world‐wide, doubly‐fed induction generators and synchronous generators with a full‐power electronic converter, and they come with pitch‐controlled rotors. These particular variable speed designs decouple the rotating masses of the turbine from the power system, thus, producing many power quality benefits as opposed to the old turbine configurations. These turbines could transmit real and reactive power, and some fault ride‐through capability, which are required by power network operators. To enhance production, development is now going directed toward bigger machines, which means greater dimensions of the blades, more hub heights and greater rotor dimensions. These modifications mean significantly increased capacity factors within given wind resource regimes, enabling more opportunities in both established and new markets [52, 54].

Schematic illustration of installed wind power capacity, top 10 countries in 2019. Schematic illustration of wind power market forecast for 2017–2021.

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