The most popular wind turbines in the industry today are the horizontal axis upwind turbines. When it comes to the popularity of certain wind turbines models, it is mostly based on reliability and value. The efficiency is not a best measure of a turbines viability and effectiveness. Parameters such as and low cut-in speed for low wind location and durability in high wind locations are far more important compared to efficiency.
Nonetheless power efficiency of turbines (Electrical output/ Wind Energy input) does have its place in determining a turbines overall effectiveness. It is well known that increasing the number of blades improves the efficiency. Therefore a two bladed turbine is more efficient than a single bladed turbine, similarly a three bladed turbine is more efficient than a two-bladed counterpart. However Law of diminishing returns catches up. Adding more blades to a three bladed turbine does improve the efficiency but the cost increase compared to efficiency increase is much higher. Furthermore, there is also the matter of enhanced dynamic loading on the nacelle and bearings with additional blades that needs to be dealt.
Generally larger wind turbines are more efficient than smaller wind turbines. There are many reasons for higher output rate. One of them is the fact that larger wind turbines they are exposed to better quality wind due to a higher mast. They are also designed to spin at slower speeds which improves their overall reliability. They have a gearing system and blade pitching mechanism that can cater to changing wind speed and direction.
In this article, the most popular large scale wind turbines (above 500 kW) in the industry have been explored. It is interesting to note that some turbines are ahead of the pack because of their drive train while others have better blades shapes. Mergers of large scale companies will usher in conflation of technology that could result in even better products in the future.
Siemens 2.3 MW
Siemens is a reputable name in industrial machinery. Siemens provides a range of wind turbine options, their largest being 7.0 MW. However, their 2.3 MW platform turbines are by far the most popular. Siemens provides 3 different wind turbines in the 2.3 MW capacity range. The smallest of them has a swept area of 8000 m2 (blade length 49 meters), while the largest (SWT-2.3-120) has a swept area of 11300 m2 (blade length 59 m). The advantage of larger blade is reflected in its higher capacity factor and lower cut-in speed.
The Siemens 2.3 MW turbines are extremely popular and have been installed in wind farms across the world. The blades can can be tilted up to 6 degrees and can handle gusts (3 sec) up to 59.5 m/s. One of the Siemens 2.3 MW, the SWT-2.3 101 turbines can be recognized from a distance with its unique crayon-like nacelle shape.
In the off shore sector, Siemens 3.6 MW machines are extremely popular with more than 1000 of them installed in the UK alone.
Vestas 2 MW
Vestas is one of the oldest and also one of the largest wind turbine company in the world. Established in 1945, the Danish company today employs over 21000 people globally. Within the wind power industry, Vestas is an established name and their products are at the forefront of the industry. It should be noted that the highest ever Capacity Factor to be recorded anywhere in the world (57%), was on a wind farm in Scotland that deployed Vesta’s wind turbines. The company also holds the record for producing the wind turbine with the highest nameplate capacity of 8 MW, Vestas 164.
The 2 MW platform are one of the most popular turbines in the Vestas portfolio with over 15000 units sold since 2002. The company offers 4 different turbines in the 2 MW range with different blade sizes. Thier V110-2MW model, offers an extremely low cut-in speed of 3 m/s and therefore is popular in low- to- medium wind sites.
General Electric 1.5 MW
General Electric is a household name not only in the United States, but around the world. The company whose founder included Thomas Edison, has thousands of products in its portfolio. It entered the wind power industry in 2002 but has already installed 250,000 wind turbines.
General Electric wind turbines have four different platforms 1.5 MW, 2.5 MW, 3.6 MW and 4.2 MW. Their product that is far popular compared to others is the 1.5 MW platform range. The choice for a 204 watts per square metre specific power rating enables this turbine to achieve very high capacity factors that were the preserve of really high wind onshore and offshore sites. GE first produced this turbine in 1996. The earliest models developed by GE had a peak power of 15000 kW however newer models in the category use the same platform but have borrowed blades from 2.5 MW platform thus giving them additional power 1.7 MW and higher capacity factor.
GAMESA 2.0 MW
GAMESA is a Spanish concern and has more than 22 years of experience in the wind power industry. Gamesa was one of the first company to commercialize direct drive turbines in the market. GAMESA 2.0 MW is extremely successful platform and has become a reference in the industry. It has 5 different rotor diameters within this platform to cater for all kinds of wind conditions. More than 20,000 unit of this turbine platform have been sold worldwide in 34 countries. Owing to the success of this model, Gamesa are have successfully ventured into 2.5 MW platform by up scaling their existing product. Gamesa has recently entered a merger with Siemens Wind, which is good news for connoisseurs of renewable energy.
The name Enercon has become synonymous with very large scale turbines. In contrast to the record braking Enercon E-126 7.2 MW turbine, this German company had humble beginnings. Their initial turbines were modest with 55 kW capacity and blade sizes of 15 meters. In fact even today, the most popular product of Enercon is the E-40, which is a direct drive 500 kW turbine.
Enercon’s largest wind turbine the E-126 has the second highest named capacity but has over 150 units operational units in comparison to Vestas 164 which has less than 50.
Goldwind 1.5 MW & Sinovel SL1500
Goldwind and Sinovel are Chinese wind turbine companies that can be credited for halving the price of wind energy. Today Goldwind is the second biggest wind turbine company in the world, only second to Vestas. Similarly, Sinovel in 2011 was also being dubbed to become biggest wind turbine company in the world, however it did not live up to its potential. Their 1.5 MW platforms are extremely popular and have provided access to wind power for many countries in the developing world. The Goldwind 1.5 MW is a permanent magnet direct drive wind turbine, that has a very high reliability because of fewer moving parts. The generator and rotor require only two bearings compared with more than 20 for conventional gearbox machines.
As mentioned earlier, the efficiency of the wind turbine is not a measure of its success and popularity. Other factors such as cost, ease of installation, durability and fitness of purpose play a major role in making it a commercial hit. Wind power is consistently grown over the past decade. Gansu wind farm that is expected to be completed by 2020, will become the biggest power plant in the world (20 GW). The price of wind power has come down substantially and will continue to decrease with more competition in the future.
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