HISTORY

HISTORY

WIND TURBINE. GLOBAL DEMAND

The wind power as an element of green technologies is attractive for investors due to the following reasons:

  1. The wind energy is available on 70% of all the Earth surface and free (Renewable capacity statistics, IRENA 2019);
  2. Access to the wind energy without any climatic barriers, day or night, be it polar night, cloudy weather or snow mantle;
  3. The market offers the wind turbines (WT) of different sizes for stable power supply. The consumer is interested in reducing the supply price.
  4. The issue of power supply to the remote territories away from the grids (distributed power consumption) is far from its solution in many countries. The improvement of the level of life and access to education are impossible without large-scale electrification.

Today, two types of wind turbines are used in the world: with a horizontal axis (HAWT) and vertical axis (VAWT).

The HAWT turbines attract investors by their high Wind Power Utilization Factor (WPUF), efficiency of power generators, scalability and reproducibility of the economic model. The projects using HAWT turbines publish the following numbers: 90% of the turbines have the power of >500 kW, the average construction price of about 1,000 $/kW, the average power price from0.1 (several WTs) to 0.15 (one WT) $/kWh, the payback period of 10 years or more, which is comparable to the investments into the nuclear power generation (IRENA 2019).

The WTs are produced with account of extreme weather factors. However, the wind both gives power and kills turbines. Thus, in Gujarat, India, in 1998, 111 turbines were uprooted by the hurricane (Jargstorf, 2010), dozens of turbines in Miyako Jima, Japan (Gardiner, 2004), and Cangnan Xiaguan, China, were destroyed in 2006. Dozens of turbines were destroyed by the ice rain in Taxes, USA, in 2019.

Poor stability of HAWT during hurricanes and ice blasts due to the complexity and susceptibility of the rotor mechanism allow turning to VAWT as an alternative. The WPUF values demonstrated by VAWT are 3-4 times lower than those of HAWT, making VAWT lose in the “investment shows” to the competitor.

Two basic VAWT constructions are the derivatives of Darrieus rotor (driven by the rotor blades’ lifting power) or Savonius rotor (driven by the difference between the power of the blades frontal resistance in the wind). It is considered that the most successful VAWTs is Darrieus-type with WPUF of 0.43 and Savonius-type based on a semi-sphere with WPUF of 0.19-0.20 (Gipe, 2009). Savonius efficiency may be improved by introducing new aerodynamic forms, deflectors, towers that would increase the costs but not the incomes of the VAWT owner. It is considered that Darrieus requires less materials in terms of $/kW than Savonius.

The advantages of the VAWT as opposed to the HAWT is that it operates with any wind direction. The VAWT does not require a mechanism for turning the rotor blades, which is a high tower with a turning mechanism. Due to the location of the generator and the gear box close to the ground and simple construction, the VAWT requires less operation costs. Some VAWTs are designed to withstands the gusts of wind of up to 60 m/sec. (SeaTwirl, 2021).

The first cheer of the investors in respect of the prospects of Darrieus VAWTs was destroyed by negative experience. Thus, 95 units of TW “FloWind” that have been rolled out in California since 1982 (the Altamont Pass and the Tehachapi Loop) generated up to 100 million kW/h at the peak, however, due to equipment failures and force-majeure costs of maintenance, the projected profit was not achieved and the project was shut down in 1992. The negative track record of FloWind is used by Darrieus opponents as an argument against the VAWT (Gipe, 2009).

The last 30 years have seen the emergence of new mathematical design models, new types of turbines, construction materials, powerful permanent magnets, allowing scientists and investors to see the new horizons. One of the examples is VAWT SeaTwirl. The turbine of Darrieus type is located on an anchor in the sea that does not freeze in the winter in high latitudes, resistant to the winds of up to 60 m/s and demonstrates impressive figures of cheap electricity of 0.05 E/kW with the VAWT lifecycle of 25 years (SeaTwirl, 2021). The question of sea corrosion remains, but this factor will become more understandable only after 5 years of sea turbines’ operation. The Australian project VAWT-X Energy announces a high WPUF of 45%, fast payback based on the track record of VAWT VX-80 for 5 years, which is less than the payback period of HAWT. The price of power generation of VAWT VX-80 amounts to 018 $/kW.

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As a rule, the optimism about the WT leaves out the issue of locating them in high latitudes. The highest power consumption for life sustenance does not meet the level of development of alternative energy generation. Solar batteries, the WT competitors, are an economically attractive project, however, their operation is limited in the North. The lack of sun and polar nights, rain, snow, ice, wind, damaging the structures and fixtures, undermine the attractiveness of solar power stations. HAWT and VAWT may be the ground for the alternative energy over 50 latitude (for the north hemisphere), but the ice blasts and snow mantle prevent this. The icing blocks the rotor movement, causes incorrect balance and a pulsing torque, which destroys HAWTs and VAWTs. It was the icing that damaged the FloWind turbines in the mountain passes of California, and this issue is very far from being solved.
Thus, in the North VAWTs and HAWTs are exposed to the damage caused by snow, ice, corrosion and storms. In the South, VAWT and HAWT are exposed to corrosion, tropical storms, and hurricanes. High risk of destruction is what underlies high insurance premiums and reduces the economic attractiveness of WT.
One of the important tasks in connection with designing and manufacturing the WTs is the reduction “carbon footprint”. The harm caused to the Earth by the consumption of fossil fuels during the production of WT basic components at all the stages of >500 kW HAWT construction is so high that causes a lot of questions and concerns. It turns out that the higher is the WPUF, the more durable are the WT components, meaning the extensive use of petroleum-based polymers, non-ferrous metals, rare-earth elements, power consumption for the production of metals and organic synthesis; the higher is the difference between the benefit and harm for the Earth, and more voices speaking against the construction of new mega-wind-generators.

THE LSSUE WITH WIND POWER

HAWT >500 kW have already become a pretty usual business project. The increase in the rotor size in combination with attractive price per kW/h results in boosting the related “hidden” costs, such as roads construction, forming of pits in the rocks, etc. The reduction of HAWT size curtails the economic benefits but does not mitigate the negative factors.
The following economic criteria of wind power have been identified (D.Al. Kacaprakakis, D.G. Kristacis 2012):

  • Available wind potential and geographic specifics of the installation location
  • Physical WT sizes
  • Nominal WT capacity
  • Requirement for regular WT maintenance
  • WT cost
  • Available area in the place of WT installation taking into account the WT rated capacity
  • Extreme wind, hurricane, icing and a need in the insurance program
  • Restrictions caused by the exposure of WT to the environment, its habitants and human activity
  • Requirements of a utility enterprise to the quality parameters of the power produced by the WT
  • The price of redistribution and accumulation of power within low-power private power station
  • Existing technical infrastructure in the place of the WT installation: a road network, distance to the power lines

Let’s look at the extreme values that attract attention and those on the periphery.
The WT power output is related to the wind speed. This criterion allows making the preliminary estimate. The WT power output Ptwind  according to A.Hasankhani, A.Vafaeizadeh et all., 2021, is as follows.

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is the wind speed, generator cut-out speed and nominal WT wind speed, which define the range of power generation by the wind turbine in different WT speed ranges

 
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is the rated capacity and the trip capacity of the wind generator, respectively.

 
Elementor Error 404 #26

is the wind speed.

 

The final economic analysis figures can be obtained by using the rated data for the HAWT and separately for the VAWT. The total cost of power production by the WT in 24 hours will be calculated as follows.

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is the wind speed, generator cut-out speed and nominal WT wind speed, which define the range of power generation by the wind turbine in different WT speed ranges

 
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cost of power generation by WT, taken as 0.15$/kW

 

In 2/3 of the total earth surface WT will be able to generate power with the wind speed in the range from 5 to 25 m/s. WT achieve the rated / nominal mode of operation at the wind speed of 10 m/s (IRENA, 2018). Such territories include sea coast, foothills, island territories, grasslands and deserts. Such territories have been actively claimed by the HAWT for the last fifty years.
Consequently, with the wind speed Scut-in in the range from 3 to 10 m/s and with Scut-off >25 m/s, the WTs physically cannot produce the power according to the specification (rated capacity), and the consumer is actually misled. Sometimes, the economic estimates specify 3 m/s as the starting value of Scut-in for the generation of power at the rated capacity of the WT Srated, thus misleading third parties (A.Lopatin, V.Kucherov et all. 2014).
It is reasonable to perform the economic calculations referring to the location of WTs for the areas with the average annual wind speed over 7.5 m/s. It is economically unprofitable to locate the WTs in the regions with the average annual wind speed of 4-5 m/s. A number of innovative WT companies perform their economic analysis for the wind speeds of 6.5 m/s, for example, VAWT-X Energy. The issue of availability of the WTs operating with the wind speeds of 3-5 m/s, which is about 30% of the earth surface, does not have a solution at the moment.
By way of example, the table shows technical characteristics of the VAWTs, which provide Scut-in for the wind speeds at <4 m/s as compared to HAWTs (M.A.Hyams, 2012). The difference between Scut-in and Srated is worth noting, the last corresponds to Ptwind (in the table Manuf. power rating), demonstrated by the seller and taken into account by the buyer’s accountant.

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In view of the above, the pioneer projects in the area of innovative VAWT scare the investors with the counterparts’ negative track and high price of the starting investments. A rational household owner analyzes the costs and incomes and will not find it reasonable to invest into the VAWT for 10 years. As a result, the installation of a household VAWT rarely becomes a profitable project.
WPUF improvement and boosting power generation by the WT is the ultimate goal of the majority of the projects. Both results are achieved by using innovative materials (S.C. Bhatia, 2014). Owing to the resulting reduction of structural costs, improvement of the turbine’s WPUF and the generator capacity, the total WT costs was reduced almost three times from 1983 to 2018 (IRENA, 2019).
What is HATW comprised of? Rotor components, accounting for approximately 20% of the wind turbine costs, include blades made of composite materials to transform wind power into low speed rotational energy. It should be noted that composite materials have a material carbon footprint.

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The generator and gear box components amount to approximately 34% of the HAWT costs. As a rule, the electric generator is synchronous and contains pure copper as the basis for the electric magnets. In low capacity generators the electromotive force is formed by neodymium magnets.
The gear box is intended for transforming low-speed incoming rotor rotation into high-speed electric generator rotation. The gear box may be represented by planet gearing, variable speed drive, or infinitely variable transmission. All three are produced from high-quality steel with a known carbon footprint.
The controlling electronics include by high current controllers and relays for the mechanisms changing the blade step, turning mechanisms, electrodynamic rotor brake. All the electric devices are produced from synthetic plastics, containing rare and non-ferrous metals.
The structural support components, accounting for about 15% of the WT cost, include the tower and the rotor’s yawing mechanism. All the components are produced from steel, composite materials, including aluminium, magnesium, nickel, cobalt and require considerable consumption of fossil energy during their production.
It would be logical to assume that the larger is the rotor’s turbine size and the content of new technologies, the more fossil energy is required to produce it and the higher is the carbon footprint of such a WT. This conflict exceeds the threshold of responsibility for the Planet and requires considerable capital from the investors. It calls for the following question: are the modern WT really green having such a strong carbon footprint?
Innovative materials and technologies do not make regular maintenance, including insurance payments, redundant. It is well-known that a complicated cinematic and power-generating chain poses more emergency risk.
The larger is the turbine, the more power and noise it produces. The transfer of power requires the conductor with a large copper or aluminium cable. The noise makes it necessary to remove the WT from the places of actual power consumption, that is, from the people, and use a lot of electric wire. Rhythmic noise produced by the HAWT is dangerous for the majority of living organisms and is not suitable for location close to the residence areas. The noise is generated by the rotating HAWT blades. Usually, the stronger the wind is, the more noise is produced.
An attempt to avoid the risks related to the large WT causes another issue. Smaller HAWT and VAWT are unable to feed the power into the unified grid without first accumulating it. This requires using electric batteries. These are expensive, have a limited charge-discharge, serve for not more than 5 years (lead batteries) or 7 years (lithium batteries) and increase the power prices several times to unattractive values at the launch of the project, being significantly higher than 0.15 $/kW.
Additionally to the batteries, it requires a charge controller, an inverter for the transformation of accumulated current into variable 50Hz current of the household grid. Practical solutions of direct power accumulation, such as heat energy, are at the initial stages of development. A household WT often becomes not a source of free power, but a sign of belonging to the right social group concerned with the Planet’s future. As a result, the rational household owner as a mini-investor is not motivated to purchase a private power station with the payback period of over 10 years.

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