Aerodynamics Considerations in Wind Turbine Blade Design
Blade design is one of the most important & complex process in the development of improved and more efficient wind turbines and hence the development of wind industry as such. Advances in aerodynamic design advances has over the years contributed towards that end.
Though ideally, to obtain best results from a perfect blade designed to extract maximum power
from wind, it should have a perfect aerodynamic design. Viewing the requirements of extracting
maximum power at minimum costs pragmatically, leads to necessitating numerous compromises, influenced by various factors.
The major factors that influence design of a practically adequate blade are:
– Economics to ensure costs under control
-Â Structural Strength to take care of bending stresses (maximum at root), aerodynamic &
structural dynamic loads
-Â Noise & Aesthetic considerations
-Â Choice of materials; carbon versus fibre glass; availability of desired material
-Â Manufacturing Processes adopted
The blade needs to be robust enough to survive forces acting on them due to the variability of wind, to include varying wind velocities, facing gusty conditions to an extent, centrifugal & centripetal forces and other conditions that are rarely optimal.
Over the years, with the continuous development of larger & more efficient Wind Turbines, a variety of blade designs & materials have got introduced, mainly through trial & error, resulting in the most popular 3-bladed composite blade designs, each better than the other.
The choice of blade aerofoils, chords, twist distribution, blade tip & root configurations, use of spoilers, use of vortex generators for noise control &/ or enhancing aerodynamic efficiencies, are a result of compromises being made from conflicting considerations. The dictating requirements could be, need for blade stiffness/ flexibility, Solidity of rotor disc, aerofoil thickness, maximising lift coefficients, minimising drag, roughness tolerance. To sum it all, the design considerations are numerous and at times conflicting leading to the need for an intelligent compromise.
The aerofoil is the foundation of wind turbine blade designs & hence its optimisation goes a long way in achieving the three objectives of aerofoil design, namely, aerodynamic performance of the blade, Noise control & its structural robustness.
Selection of Aerofoil Sections along the Blade Length
In the early stages of development of wind turbine blade designs, NACA series of aerofoils, which were basically developed for use in aviation industry were used mainly because of their inherent design of high lift Coefficients and low Drag Coefficients, (High Lift to Drag ratio). However, it was quickly recognised, that there were numerous drawbacks which glaringly stood out while they were being used for high performance blade designs wind turbines. This led to the development of a number of specially designed aerofoils for wind turbines. These included:
- American S Series airfoil
- Dutch DU Series
- Swedish FFA-W series
- Danish RisF series airfoil
While a number of research papers are available, describing the utility of each of the aerofoil sections, their suitability for use at specific Tip speeds, Lift coefficients, L/D ratios, structural properties, and noise characteristics, in order to grasp the nuances of each of these designs, certain basics of loads on a wind turbine blade and specifically an aerofoil section would be necessary and the same are briefly introduced in subsequent paragraphs.
Forces Acting on the Blade
Fig 1 : Forces Acting on Blade Section of a Horizontal Axis Wind Turbine
Figure 1 above depicts a wind turbine, viewed from top. (Plan View). Details are explained below:
– The direction of rotation is clockwise as seen from front end, as indicated.
– Aerofoil section of one blade has been shown.
– As it is understood, the turbine is designed to face the wind squarely and the ambient wind velocity vector impinging the aerofoil section is shown by the blue arrow.
– Since the blade is rotating, the instantaneous tangential velocity of blade is considered. The relative wind velocity vector due to motion of the blade will be opposite to the blade tangential velocity vector.
– Resultant of the two wind velocity vectors impinging on the aerofoil section, (the actual relative velocity vector) is shown as a red arrow.
– The angle between the chord of the aerofoil section and the relative velocity vector is called the angle of attack. (âº)
– Angle of Attack has a great significance on aerodynamic performance of an aerofoil. A brief
bringing out its significance is explained subsequently.
– Lift generated is perpendicular to the relative wind velocity vector, and perpendicular to the lift is the drag. (in the same direction of the relative wind velocity). The same are depicted in Figure 1.
– Resultant of Lift & Drag forces is the “Net Aerodynamic Force on Bladeâ€.
– This “Net Aerodynamic Force on Blade†is resolved into two mutually perpendicular forces. These are (a) the Torque Force that Rotates the Rotor & (b) the thrust force, which acts along the axis of rotation. This force is the design element for finalising the bearing design.
Significance of Angle of Attack
It can be appreciated that the aerofoil sections move at faster speeds as we move from root to the tip of the blade (V=r w). While the ambient wind speed remains the same. The effect of this would be, that the angle of attack at various aerofoil sections all along the length of the blade from root to tip will progressively change. The necessity of giving a twist to the blade as we move from the root to tip of the blade is shown in the Figure 2 below.
If there is no twist, the angle of attack would have large variations all along the length of the blade and hence, only a section of the blade will generate optimal lift and the most of it will be either stalled of producing low lift and therefore working at sub-optimal levels. By giving the twist, the most efficient angle of attack, (see Fig 3) for each aerofoil section all along the blade length is obtained. This leads to an overall performance level of the blade to be enhanced/ optimised.
Fig 2: Showing the necessity of twisting the blade
The production of lift force due to the aerodynamic shape of the blade depends on a number of factors like the blade profile, shape, thickness, camber, aspect ratio and the surface finish of the blade, which must be in consonance with the designed rpm, tip speed ratio, solidity and the magnitude of lift coefficient.
Fig: 3 Indicating that an aerofoil section performs at peak performance levels (at CL max) for a very narrow range of the value of Angle of Attack. Beyond the max level it stalls and before that the blade efficiency rapidly drops.
 The complete mechanism of production of lift and various other modifications to enhance blade aerodynamic performance will be covered in my next blog.
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RE Industry – PAA Awards 2019
PAA Award was all about honoring the O&M field workmen who with their own hands have developed the industry as well as developing their own profile. So this honor comes to them for which PAA Awards have been instated and PAA Award 2019. This function was held in Pune on 24th Oct.
Out of 500+ RE industry Nominations, 12 most deserving candidates were chosen by the jury panel of 9 and felicitated for their stupendous work.
Among the 12 Awardees, 5 have been honored gold, 4 silver and 2 as rising stars.
Here is the list of Awardees: –
- Mr. Tejas Sole – The Go-getter 2019: Gold Award
- Mr. Dhananjay Nandedkar – The Innovative Mind 2019: Gold Award
- Mr. Nivas Vallavan – The Troubleshooter 2019: Gold Award
- Mr. Bushan Palhade – The safety & Quality Combo 2019: Gold Award
- Mr. Yogesh Bochare – The Skill Developer 2019: Gold Award
- Mr. Manoj M.SÂ – The Go-getter 2019: Silver Award
- Raman Sharma (Currently with Siemens Gamesa)- The Go-getter 2019: Silver Award
- Mr. Agastya Sagar (Currently with Sagar Asia Private Limited)- The Innovative Mind – 2019: Silver Award
- Mr. Pankajkumar Bhagwan Suryawanshi (Currently with ReGen) – The Troubleshooter 2019: Silver Award
- Mr. Shanmukha Srinivasa Kumar Bathina (Currently with Greenko Wind Power) – The Skill Developer 2019: Silver Award .
- Mr. Deepak Nair (Currently with Clean Max Enviro Energy Solutions Pvt Ltd.) – The Skill Developer 2019: Rising Star Award.
Apart from the RE industry Awardees, the inhouse 30 Power group members countrywide were also felicitated with respective PAA Awards in recognition of their contribution.
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How Much Wind Energy Need in Your City?
The world’s first floating wind farm is generating electricity off the coast of Scotland. Now, a new research project estimates the amount of sea-based wind generation that will be necessary to power major cities, giving leaders and citizens new data to assess their renewable energy options.
Researchers estimate that wind farms have the technical potential to produce up to 40 times the electricity the world consumes. Yet they provide only 4 percent of the world’s electricity today. Imagine having all that surplus energy. We could power carbon removal technologies with this excess electricity. We could remove the trillion tons in excess CO2 from the atmosphere with energy left to spare.
Improved infrastructure and higher voltage cables are driving wind power costs to new lows. It is predicted that by 2040, one-third of power will come from wind and solar.
Let’s take a look at how many wind turbines would be needed to power the world’s major cities. Call your legislators or city government to encourage them to explore the land- and ocean-based wind power for your community.
The top five places that need the most wind turbines to power their major city:
- Tokyo, Japan, needs 10,310 offshore wind turbines.
- New York City, U.S., needs 3,687 offshore wind turbines.
- Seoul, South Korea, needs 3,644 offshore wind turbines.
- Shanghai, China, needs 3,304 offshore wind turbines.
- Los Angeles, U.S., needs 1,818 offshore wind turbines.
The top five cities with the biggest offshore areas, in square kilometers (km2), of wind turbines needed to power them:
- Tokyo, Japan, would need 10,620 km2 of space to power the city with wind turbines.
- New York City, U.S., would need 3,797 km2 of space to power the city with wind turbines.
- Seoul, South Korea, would need 3,752 km2 of space to power the city with wind turbines.
- Shanghai, China, would need 3,402 km2 of space to power the city with wind turbines.
- Los Angeles, U.S., would need 1,872 km2 of space to power the city with wind turbines.
It seems that Asia is the continent that is most hungry for a renewable energy source; Tokyo, Seoul, and Shanghai are among the top five major cities that could use the most wind turbines to power their city.
But what about the cities that don’t need a lot to power them?
The top five cities with the smallest offshore areas (km2) of wind turbines needed to power them:
- Milan, Italy, would need 244 km2 of offshore space to power the city with wind turbines.
- Kuala Lumpur, Singapore, would need 293 km2 of offshore space to power the city with wind turbines.
- Barcelona, Spain, would need 307 km2 of offshore space to power the city with wind turbines.
- Mumbai, India, would need 355 km2 of offshore space to power the city with wind turbines.
- San Francisco, U.S., would need 373 km2 of offshore space to power the city with wind turbines.
The top five places that need the least wind turbines to power their major city:
- Milan, Italy, needs 238 offshore wind turbines.
- Kuala Lumpur, Singapore, needs 286 offshore wind turbines.
- Barcelona, Spain, needs 299 offshore wind turbines.
- Mumbai, India, needs 346 offshore wind turbines.
- San Francisco, U.S., needs 363 offshore wind turbines.
It may come as a surprise that San Francisco is one of the major cities that needs the least amount of wind turbines to power its population, as well as Mumbai, as they both have a very large population. Take a look at the following interactive graph and see where your nearest major city comes in at and how many wind farms it would take to power its population.
% of City Area
km2Â of wind turbines
- Published in Renewable Energy Sector News, Uncategorized
India’s top 9 states by installed wind power capacity!
India is at the cusp of a renewable energy revolution. The government has already set an ambitious target to achieve 175 gigawatt (GW) of renewable energy capacity by 2022.
Keeping the target in mind, states have already started ramping up their installed solar and wind powered capacity.
1.Tamil Nadu
Tamil Nadu tops the list of states with the largest installed wind power generation capacity in the country. The state’s total wind capacity at the end of 2018 stood at 8,631 Mw while its total installed electricity generation capacity stood at 30,447 Mw at the end of 2018, with wind sector’s share at 28.34 percent.
2.Gujarat
Gujarat houses the second-largest installed wind power generation capacity in the country. The state’s total wind capacity at the end of 2018 stood at 6,044 Mw while its total installed electricity generation capacity stood at 31,382 MW at the end of 2018, with the wind sector’s share at 19.25 per cent.
3.Maharashtra
Maharashtra houses the third-largest installed wind power generation capacity in the country. The state’s wind capacity at the end of 2018 stood at 4,789 Mw while its total installed power generation capacity stood at 43,779 Mw at the end of 2018, with the wind sector’s share at 11 per cent.
4.Karnataka
Karnataka houses the fourth-largest installed wind power generation capacity in the country. The state’s wind capacity at the end of 2018 stood at 4,584 Mw while its total installed power generation capacity stood at 27,199 Mw at the end of 2018, with the wind sector’s share at 17 per cent.
5.Rajasthan
Rajasthan houses the fifth-largest installed wind power generation capacity in the country. The state’s wind capacity at the end of 2018 stood at 4,300 Mw while its total installed electricity generation capacity stood at 21,833 Mw at the end of 2018, with the wind sector’s share at 20 per cent.
6.Andhra Pradesh
Andhra Pradesh houses the sixth-largest installed wind power generation capacity in the country. The state’s wind capacity at the end of 2018 stood at 4,007 Mw while its total installed electricity generation capacity stood at 23,726 Mw at the end of 2018, with the wind sector’s share at 17 per cent.
7.Madhya Pradesh
Madhya Pradesh houses the seventh largest installed wind power generation capacity in the country. The state’s wind capacity at the end of 2018 stood at 2,520 Mw while its total installed electricity generation capacity stood at 21,873 Mw at the end of 2018, with the wind sector’s share at 11.52 per cent.
8.Telangana
Telangana’s installed wind capacity at the end of 2018 stood at 128 Mw while its total installed power generation capacity stood at 15,944 Mw at the end of 2018, with the wind sector’s share at 0.80 per cent.
9.Kerala
Kerala’s installed wind capacity at the end of 2018 stood at 53 Mw while its total installed power generation capacity stood at 5,083 Mw at the end of 2018, with the wind sector’s share at 1.04 per cent.
[Source: Economics Times]
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POWERCON announces Col Bharat Sharma as the Executive Director!
Pune: 8th May’18: POWERCON, an Indo-German JV with M/s BaxEnergy GmbH, Germany, is the first Indian Renewable Energy Asset Management Company that provides a complete 360-degree Operation and Maintenance (O&M) service for Renewable Energy assets with varied makes, models, capacities & technologies, today announced Col Bharat Sharma as the Executive Director (ED) of the company.
With a career span of almost 5 decades, Col Bharat Sharma brings to POWERCON his rich experience as an Executive Director.
In his earlier role, he was an Educational & Renewable Energy Tutor at ENERCON, were he trained 2500+, technical commandos for Domestic & International Renewable Energy operations.
Prior to that, he served Indian Army for over 35 years.
He is an Indian Institute of Technology Delhi alumni and was also a visiting faculty at Royal Melbourne Institute of Technology, Australia.
” The PowerTeam has immense respect & gratitude towards Col Bharat’s contribution in quickly raising the company’s technical strength and discipline by virtue of which we have earned a marked reputation in the wind industry. ”
– Praveen Kakulte, CEO, POWERCON.
His ability to motivate the organization has led to company’s continued success.
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Enercon opens new channels for green energy
GERMANY: The German turbine maker has developed a high-performance charging station for the latest generation of electric vehicles, and has ambitious plans for wind power development in India and Argentina.
The E-Charger 600 prototype began operating on 14 March at Aurich’s Energy, Education and Experience centre (EEZ), with the commercial launch planned for later this spring, starting in Germany before rolling out across Europe. The plan is to install up to 30 pre-series charging units this year.
Each E-Charger 600 is equipped with up to four charging columns, and claims Enercon, it offers the most powerful rapid-charging solution for electric vehicles (EVs) available on the market today. It is especially focused on the next generation of EVs, including high-performance premium cars such as the 600kW Porsche Mission E and Audi e-tron, plus vans and trucks.
The technology complies with the latest High Power Charging 2 (HPC 2) standard capable of charging up to four EVs at the same time with variable ratings of 50-350kW. This would, in an ideal scenario, take only around eight minutes to “refuel” a vehicle for a 400km-plus plus driving range. By comparison, Tesla’s maximum charging capacity is 60-70kW, according to independent e-Mobility experts at the launch, while ABB offers high-performance chargers up to 250kW.
The E-Charger 600 is a technology spin-off of Enercon’s frequency converters, says Alfred Beekman, head of the control technology division. “Converters are a core technological and integral part of our in-house E-Module, which is incorporated in over 28,000 turbines,” he says. “Each frequency converter consists of two main functional parts. The ‘generator-side’ rectifier converts generator AC power with variable frequency into direct current (DC). The ‘grid-side’ inverter second part converts DC via a DC/DC bridge to grid-compliant AC power. We re-utlilise the modular inverter part, composed of standardised 60kW modules, and for the E-Charger 600, up to a maximum of 600kW.
Ecosystem
The inverter DC-power output voltage is about 700V. Enercon’s main project partner, Germany’s Power Innovation, developed a dedicated DC/DC converter, which boosts voltage level to around 920V DC, sufficient for achieving 350kW charging capacity. Beekman adds that the solution retains the advanced grid support and grid stabilising features already incorporated in Enercon converters. A second built-in feature of the E-Charger 600 is the optional linkage to battery storage units, for use under demanding conditions when the grid is weak.
The product development fits well into Enercon’s strategy to open up additional sales channels for green energy. It also represents a diversification of its wind-turbine core business towards a fully integrated energy concept in support of the energy transition process in Germany.
“One key example is our co-operation with the Aurich district in establishing the Stadtwerke Aurich, a green utility that became operational in 2016 and in which Enercon has a 40% share, says managing director Hans-Dieter Kettwig. “Our long-term aim is to build an ‘ecosystem’ around our wind turbine key products. This will be gradually expanded with other integrated energy options like power-to-gas, battery storage, and innovative marketing models for wind power, including from older-generation turbines.” Enercon was founded and is still based in the town of Aurich in Lower Saxony, north-west Germany.
Kettwig also elaborates on plans and strategies to integrate Lagerwey’s products and key technologies into a global product portfolio after acquiring the Dutch turbine maker.
“Enercon is a large, globally operating supplier with decades of product-to-market experience in many main markets. This small company has come up with several innovative and promising solutions, it could become a creative partner in smaller, developing markets for which it lacked sufficient leverage on its own. For us, a very promising development was Lagerwey’s business deal with Russia’s Rosatom, which involves initial turbine production in the Netherlands and/or Germany, followed by step-by-step localisation.”
Increased competition
Kettwig adds that Enercon needs to be much faster in developing and adapting its products and process to rapidly changing market circumstances and increased competition, including a shorter time-to-market for new products. “Our next moves must therefore be very quick. We cannot take 36 months to develop and fully certify a new product,” he says.
Lagerwey’s key products include the compact, lightweight 4-4.5MW L136 LP4 direct-drive platform, a modular steel tower and a self-installing crane. Kettwig says these solutions together offer substantial Capex savings and LCOE reduction potential on their own, and when integrated with existing and new Enercon products.
“The introduction of Lagerwey’s permanent-magnets generators could become a plan B, and we are evaluating several options for integrating elements of the LP4 turbines with our latest 3.5-4MW EP3 platform. Our strategy plan for the next two years will be presented at the Hanover international trade fair this April,” Kettwig says.
Enercon established a successful majority joint venture with an Indian partner in 1994. However, after initial differences on turbine production numbers, quality guarantees, and intellectual property issues, the disputes escalated and Enercon withdrew from India in 2006. It decided last year to return to the Indian wind market with a fully owned local company, Enercon WindEnergy PTY Ltd, following a series of favourable court rulings since 2013-14, whereby all patents and other IP were reinstated.
“In the period until 2006, roughly 2,500 Enercon turbines were installed in India, and another 4,000 after the split,” says Wolfgang Juilfs, Enercon’s new country director. “The former Enercon India Limited, later renamed Wind World (India), discontinued production in September last year and is now in insolvency proceedings.
Limited quality
Juilfs adds that due to limited quality of Wind World (India) O&M activities in the past two years, many of the turbines in the total fleet are no longer operating. Others operate only in curtailed modes, and there are problems with the supply of spare parts.
“The quality of the initial 2,500 turbines was good, but there is still little insight into the product quality of the turbines following the split, and the overall condition of the full fleet,” says Juilfs. “To support Indian customers with the running problems of this fleet — mainly comprising E-32, E-40, E-48 and E-53 turbines, Enercon has teamed up with three local independent service providers. In addition, the first two containers with spare parts were recently shipped from Germany to be available in India before the start of the upcoming wind season in April/May.
Juilfs says there is still substantial goodwill among Indian clients towards Enercon GmbH in Germany, and that this “old” customer based is very interested in the new E-126 EP3 and E-138 EP3 turbines.
“We will initially enter the Indian market with the E-126 EP3 still incorporating a 400V generator, and well-known electrical system, but fitted with the larger 138-metre rotor. This machine, and the final E-138 with the new 690V electrical system, is our best turbine for the Indian market. Our sales team has already entered extensive talks with Indian developers, and by initially offering the EP3 variant with the 400V electrical system we will be able to install the first turbines early in 2020.”
  Step up… Enercon will offer its new EP3 model in India with a 138-metre rotor (pic:ENERCON GMBH)
The turbines will first come only with 135-metre concrete-steel towers, based on the classic hyprid design composed of multiple stapled coning rings with two or more tubular steel section on top. These towers and the rotor blades will be the first components to be localised, says Juilfs. “The blades will come from a local third-party supplier, but based on a dedicated Enercon blade design. We expect to require 12-15 months for his localising process, and this will be followed by additional main components for the local and export markets in Asia.”
Latin American push
Nikolaus Kraus coordinates Enercon’s activities in Latin America, traditionally focused on Brazil, but with a growing eye on Argentina, which is poised to become the region’s second-largest wind market over the next few years, thanks to a government objective to install 6-7GW of wind power by 2025. Patagonia in the south of the country is blessed with very strong winds — up to 12m/s on average, and with low turbulence, Kraus explains.
“These wind conditions exceeed IEC I standards, and we offered our 3MW E-82 E4 model for a 27MW wind project under development. These turbines feature an 82-metre rotor, which is modest by comparison with some competitors’ offerings, but the combination of being slightly conservative, and our direct-drive technology seems to match well with client preferences,” he says.
As in other Latin American markets, the product focus in Argentina is shifting rapidly to turbines in the 3-4MW class. Enercon already actively offers the E-126 EP3 in Argentina, as this turbine fits well at sites in the south due to the unusual combination of high wind speeds and low turbulence. “Currently, all turbine components are imported, especially from Portugal and Germany,” says Kraus.
“Brazil might at first glance have seemed the logical choice, but pricing and transportation costs count for a lot. The main issue in Argentina is the port infrastructure and a key bottleneck is the availability of suitable cranes that can operate in high-wind conditions. This is where Lagerwey’s crane could perhaps play an important role, as it can be deployed in wind speeds of up to 15m/s,” he says.
Source:Â https://www.windpowermonthly.com/article/1460241/windtech-enercon-opens-new-channels-green-energy
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