ranjitbees

Oracle – DBA

WIND TURBINE TECHNOLOGY-RECENT ADVANCEMENTS.

Advancements in wind turbine technology have been growing rapidly. In the shadows of multi-megawatt wind turbines is another growing sector within this industry: residential wind. Improved airfoil designs for maximum efficiency at low wind speed, high efficiency direct drive permanent magnet alternators, improved governing methods and highly sophisticated controls and inverters now allow home owners to interface directly with utility companies or design off-grid systems. These systems are increasing energy independence, competing with current energy prices and reducing environmental impacts. Several new small wind turbines utilizing new and advancing technology have been introduced recently with promise of more to come.

Many small wind turbines and wind turbine manufacturers have suffered from extensive criticism over poorly made machines, over stated energy production, and over estimating longevity. Abundant Renewable Energy has adopted a design philosophy that puts efficiency, long life and high-energy production in low wind speeds as the first priority of our engineering and manufacturing efforts.

<http://www.medioambienteonline.com/web/guest/technology-articles/article/-/article/N2ze/21607/-1/4206/technology-advancements-in-small-wind-turbines>

Recent significant developments in wind turbine systems less than 20 kW include the following:

      1. Advanced blade manufacturing methods:

Blades for small turbines have been made primarily of fiberglass by hand lay-up manufacturing or pultrusion. The industry is now pursuing alternative manufacturing techniques, including injection, compression, and reaction injection molding. These methods often provide shorter fabrication time, lower parts costs, and increased repeatability and uniformity, although the tooling costs are typically higher.

Manufacturers are using such techniques as injection molding and compression molding to produce more durable wind rotors. Although these techniques have reduced fabrication time, lowered parts costs, and increased repeatability, they have led to higher tooling costs. Another new technique—reaction injunction molding—has been prototyped but is not yet used in production.

<http://www.accessenergycoop.com/Content/Going-Green/Protecting-Our-Environment/Wind-Energy-Information/Small-Wind-Basics.aspx>

These days, most rotor blades in the market are built from glassfiber reinforced plastic (GRP). Other materials that have been tried include wood and carbon filament reinforced plastic (CFRP).

With increased optimization in the manufacturing techniques, the capital cost of producing rotor blades have come down steadily over the past years. Replacing the hand lay up method, vaccum assisted resin infusion moulding (VARIM) has now become the most widely used technique in blade manufacturing, irrespective of the resin system in use.

VARIM  is the commonly used method for rotor blade manufacturing because of the below given advantages:

      • Excellent resin consolidation
      • Excellent fiber impregnation with more fibre content
      • Environmental fee

In recent years, PREPREG – a next generation technique, has started gaining momentum among rotor blade manufacturing processes. However, the temperature and climatic conditions in countries like India have hindered the easy adoption of this advanced blade development process. A major obstacle to employ this process is presented by the higher temperatures that constitute the climatic conditions of the country.

Though PREPEG is the more advanced manufacturing technique but it poses the following challenges:

      • Difficult handling in large structures
      • Higher production costs
      • Raw material storage

Akshay Urja Magazine

Siemens has an innovative process that makes blades in one piece, unlike the typical blade that is made in two shells and glued together. Siemens’ IntegralBlade technology uses vacuum infusion to make glass/epoxy blades in a closed process. The molding system has a closed outer mold and an expanding, flexible inner bladder. Epoxy resin is injected under a vacuum and the blade is cured at high temperature in the mold. After curing, the blade is removed from the outer mold while the inner bladder is collapsed with a vacuum and pulled from the blade. The result is a seamless one-piece blade.

<http://www.ptonline.com/articles/wind-power-blades-energize-composites-manufacturing>

Active flow control (AFC) technology to improve the turbine’s efficiency, reduces noise and vibrations, and enables high performance in smaller rotor dimensions

Smart Wind’s proprietary technology is based on a specific use of active flow control (AFC) technology, which is used to improve the aerodynamic performance of aircraft wings. The company has deployed this technology in a VAWT, resulting in improved aerodynamic performance of the rotor blades.

Smart Wind’s AFC technology enhances the turbine’s efficiency, reduces noise and vibrations, and enables high performance in smaller rotor dimensions. The rotor draws wind from all directions, making it effective in unstable wind conditions and across a range of wind speeds. The simple design offers safety and low maintenance, and can be mounted on a lower pole – factors that are especially important for more populated settings. Smart Wind’s increased efficiency – for greater electricity production – will translate into a relatively rapid ROI.

http://www.israelnewtech.com/wp-content/uploads/2011/10/SmartWind-profile.pdf

 <http://www.cleantechinvestor.com/portal/wind-energy/9844-smart-wind-ltd-the-new-generation-of-wind-turbines.html>

 <http://www.cleantechinvestor.com/portal/wind-energy/9844-smart-wind-ltd-the-new-generation-of-wind-turbines.html>

Magnetic suspension and self-pitch for vertical axis wind turbine

Maglev Engineering Research Center, Shandong University, China has committed to the magnetic bearing research and related product development. Recently, magnetic suspension technology has been applied to the vertical axis wind turbine, in which the entire rotor weight of a VAWT was suspended by magnetic bearing. The turbine friction was greatly reduced, and start-up wind speed decreased.  The manufacturing cost and operational cost were also effectively reduced. This new magnetically suspended vertical-axis wind generator has irreplaceable advantages compared with other VAWTs in the market. Due to its low cost and suitability for high-power single devices, this new VAWT design will have broad commercial potential.

Vertical wind turbine Blade 3500 – Blade Wind Tech

The Blade uses maglev technology using magnetic levitation to suspend an object on top of another without any contact, by canceling the gravity with an electromagnetic force. This revolutionary technology allows the turbine to operate without any friction, which gives it many advantages. Thanks to this, the turbine is more efficient and more importantly, it has the speed to start the lowest in the world!

The Blade incorporates both technologies Darrieus and Savonius, which allows him to combine the advantages of both technologies (starting in light winds, high torque …). Indeed Savonius technology enables it to start with very light winds and have high torque at startup, when the technology allows the Darrieus wind to benefit from a larger catchment area and therefore yield more high.

Specifications
Model Blade 3500
Maximum power 3500 W
Impeller diameter 3,2 m
Height of the turbine 3,5 m
Weight 230 kg
Materials of pale Aluminum alloy
Generator characteristics Permanent magnet generator
Braking Electromagnetic brake
Boot speed 1 m/s
Speed min in charge 2,5 m/s
Rated speed 11 m/s
Speed stop 15 m/s
Survival gear 60 m/s
Protection IP65
Lifetime >20 years

<http://www.blade-wind-tech.nl/products/vertical-axis/blade-wt/blade-3500>

Siemens IntegralBlades®

This uniquely designed wind turbine blade is made from fiberglass-reinforced epoxy resin. The cutting edge design offers ideal support in terms of optimal aerodynamics. The IntegralBlade® is made with Siemens’ patented technology and is created during a process that has multiple benefits over conventional blade manufacturing processes. Only one mould set is required in the manufacturing cycle. The blade, therefore, is just one integrated structure in which no joints need to be glued together, resulting in zero weak points in the structure that could be exposed to cracking, lightning or water ingress.

Pasted from <http://www.energydigital.com/green_technology/new-advances-wind-energy-technology>

A Design for Cheaper Wind Power

FloDesign Wind Turbine, a spin-off from the aerospace company FloDesign based in Wilbraham, MA, has developed a wind turbine that could generate electricity at half the cost of conventional turbines. The company recently raised $6 million in its first round of venture financing and has announced partnerships with wind-farm developers.

The company’s design, which draws on technology developed for jet engines, circumvents a fundamental limit to conventional wind turbines. Typically, as wind approaches a turbine, almost half of the air is forced around the blades rather than through them, and the energy in that deflected wind is lost. At best, traditional wind  turbines capture only 59.3 percent of the energy in wind, a value called the Betz limit.

FloDesign surrounds its wind-turbine blades with a shroud that directs air through the blades and speeds it up, which increases power production. The new design generates as much power as a conventional wind turbine with blades twice as big in diameter. The smaller blade size and other factors allow the new turbines to be packed closer together than conventional turbines, increasing the amount of power that can be generated per acre of land.

From the front, the wind turbine looks something like the air intake of a jet engine. As air approaches, it first encounters a set of fixed blades, called the stator, which redirect it onto a set of movable blades–the rotor. The air turns the rotor and emerges on the other side, moving more slowly now than the air flowing outside the turbine. The shroud is shaped so that it guides this relatively fast-moving outside air into the area just behind the rotors. The fast-moving air speeds up the slow-moving air, creating an area of low pressure behind the turbine blades that sucks more air through them.

Pasted from <http://www.technologyreview.in/energy/21737/>

Fangled tubercle technology

New wind turbine designs aim to address three major limitations in wind power – poor reliability when winds fail, noise and poor performance in unsteady or turbulent air. One such design is the new-fangled tubercle technology, which pushes the limits of airfoil-dependent blade design.

Tubercles are installed along the edges of airfoils to help the blades cut through the air while still absorbing energy from the wind.

Canadian wind turbine manufacturer WhalePower makes tubercle-enhanced blades similar to whale fins.

The tubercle technology tilts blades to a steeper angle to cut through air, akin to humpback whales shifting its fins at a specific angle to make a better lift in the water.

Steeper-angled winds are beneficial in low wind speeds and, with a stalled angle of 40 percent, are better in moving the air around.

Wind Energy Institute of Canada concluded that tubercles not only enhance wind turbines’ operational stability and durability under varying wind speeds and turbulence, but also reduce noise and remove tip chatter through its quieter blades.

Tubercle-enhanced blades also increase annual energy production by 20 percent due to stall reduction as the air stays attached to the blade, the institute added. Whale Power said the new rotor blade design has attracted the interest of 10 large and small turbine manufacturers.

<http://wwwaltwinds.blogspot.in/2010_11_01_archive.html>

Co-axial, multi-rotor

Two or more rotors may be mounted to the same driveshaft, with their combined co-rotation together turning the same generator — fresh wind is brought to each rotor by sufficient spacing between rotors combined with an offset angle (alpha) from the wind direction. Wake vorticity is recovered as the top of a wake hits the bottom of the next rotor. Power has been multiplied several times using co-axial, multiple rotors in testing conducted by inventor and researcher Douglas Selsam, for the California Energy Commission in 2004. The first commercially available co-axial multi-rotor turbine is the patented dual-rotor American Twin Superturbine from Selsam Innovations in California, with 2 propellers separated by 12 feet. It is the most powerful 7-foot-diameter (2.1 m) turbine available, due to this extra rotor.

<http://en.wikipedia.org/wiki/Unconventional_wind_turbines>

The Drivetrain (Gearbox, Generator, and Power Conversion)

Parasitic losses in generator windings, power electronics, gears and bearings, and other electrical devices are individually quite small. When summed over the entire system, however, these losses add up to significant numbers. Improvements that remove or reduce the fixed losses during low power generation are likely to have an important impact on raising the capacity factor and reducing cost. These improvements could include innovative power-electronic architectures and large-scale use of permanent-magnet generators. Direct-drive systems also meet this goal by eliminating gear losses. Modular (transportable) versions of these large generation systems that are easier to maintain will go a long way toward increasing the productivity of the low-wind portion of the power curve.

Currently, gearbox reliability is a major issue, and gearbox replacement is quite expensive. One solution is a direct-drive power train that entirely eliminates the gearbox. This approach, which was successfully adopted in the 1990s by Enercon-GmbH (Aurich, Germany), is being examined by other turbine manufacturers. A less radical alternative reduces the number of stages in the gearbox from three to two or even one, which enhances reliability by reducing the parts count. The fundamental gearbox topology can also be improved, as Clipper Windpower (Carpinteria, California) did with its highly innovative multiple-drive-path gearbox, which divides mechanical power among four generators (see Figure 2-12). The multiple-drive-path design radically decreases individual gearbox component loads, which reduces gearbox weight and size, eases erection and maintenance demands, and improves reliability by employing inherent redundancies.

The use of rare-earth permanent magnets in generator rotors instead of wound rotors also has several advantages. High energy density eliminates much of the weight associated with copper windings, eliminates problems associated with insulation degradation and shorting, and reduces electrical losses. Rare-earth magnets cannot be subjected to elevated temperatures, however, without permanently degrading magnetic field strength, which imposes corresponding demands on generator cooling reliability. The availability of rare-earth permanent magnets is a potential concern because key raw materials are not available in significant quantities within the United States.

Power electronics have already achieved elevated performance and reliability levels, but opportunities for significant improvement remain. New silicon carbide (SiC) devices entering the market could allow operation at higher temperature and higher frequency, while improving reliability, lowering cost, or both. New circuit topologies could furnish better control of power quality, enable higher voltages to be used, and increase overall converter efficiency.

      1. Rare-earth permanent magnets:

In addition to airfoil design advancement, alternators have also been advancing in their efficiency and capabilities. Neodymium magnets are now being used in most every modern alternator design for small scale wind turbines. These high strength rare earth alloy magnets consist of neodymium, iron and boron (Nd2Fe14B) plus other doping ingredients to increase coercivity and improve oxidation characteristics. These magnets are resistant to demagnetization, and have a much higher flux density than plastic, ceramic, or alnico magnets. This results in alternators with a higher flux density that can produce more power then an alternator of an equal size using Ferro or other magnets. Other improvements such as high quality laminate to reduce iron losses, tight air gap tolerances and low induction winding configurations to reduce cogging torque all add to increasing alternator efficiency.

http://www.medioambienteonline.com/web/guest/technology-articles/article/-/article/N2ze/21607/-1/4206/technology-advancements-in-small-wind-turbines

Rare earth elements possess strange magnetic and conductive properties aren’t found anywhere else in our cabinet of elements.

Pasted from <http://edition.cnn.com/2011/TECH/innovation/03/09/rare.earth.magnet.race/index.html>

Ferrite magnets have long been the staple in permanent-magnet generators for small wind turbines. Rare-earth permanent magnets are now taking over the market with Asian suppliers offering superior magnetic properties and a steady decline in price. This enables more compact and lighter weight generator designs. By eliminating copper from the generator rotor and using permanent magnets, which are becoming more economically feasible, it is possible to build smaller and lighter generators.

http://www.icrepq.com/icrepq-08/247-ghita.pdf

From all the generators that are used in wind turbines the PMSG’s have the highest advantages because they are

stable and secure during normal operation, they have smaller overall dimensions than wound rotor synchronous generators (WRSGs) and they do not need an additional DC supply for the excitation (circuit).

Permanent-magnet generators have been used for wind turbines for many years. Many small wind turbine

manufacturers use direct-drive permanent-magnet generators. For wind turbine generators, the design philosophy must cover the following characteristics: low cost, light weight, low speed, high torque, and variable speed generation. The generator is easy to manufacture and the design can be scaled up for a larger size without major retooling.

http://www.nrel.gov/docs/legosti/fy98/24996.pdf

Permanent magnet generators (PMGs) offer an attractive option for wind power extraction. They eliminate the need for a gearbox, increase energy extraction efficiency and are less noisy. PMGs can be controlled electronically making it possible to regulate the reactive flow into the grid as part of the generator control and maintain the power

factor close to 1.

http://www.wrapwind.com/download/1828_Individual_Blade_Pitch_and_Camber_Control_for_Vertical_Axis_Wind_Turbines.pdf

Braun-windturbinen NdFeBo permanent magnets

http://www.braun-windturbinen.com/en/generators.html

Polar Wind-12 VAWT with proprietary Axial Flux Permanent Magnet Generator

Permanent Magnet (PM) technology which achieves more efficient wind power generation and is able to produce more power at lower wind speeds due to its coreless technology. The ability of Polaris generators to eliminate traditional cogging issues makes it the ideal candidate for wind turbine applications. This new technology eliminates the need for a gearbox to be used as part of the wind turbine drive train thereby minimizing down time and reducing maintenance costs over the life of the system.

In PM generators, a coil is wrapped around a specially designed disc at the centre axis. Magnetic discs then rotate on the sides of the coiled disc and generate electricity. This kind of power generating technology is therefore ideal for wind power generation because its initial operation torque (cut-in speed) is lower.

Pasted from <http://www.polarisamerica.com/turbines/technology/permanent-magnet.html>

http://www.vawtsystems.com/images/PWT-12.pdf

      1. Induction generators:

Small turbines used induction generators in the early 1980s and later they are replaced with permanent magnet generators.

Now a few companies are reintroducing induction generators in their machines. By eliminating the inverter, these companies seek to reduce the cost of a wind turbine while improving reliability. According to several experts, inverters are the least reliable component in small wind systems.

Start-up Wind Speed  3.4 m/s (7.5 mph)
Cut-in Wind Speed 2.5 m/s (5 mph) – grid intertie; 4 m/s (9 mph) – battery charging
Rated Wind Speed 12 m/s (27 mph)
Rated Power 10 kW for grid intertie, 7.5 kW for battery-charging
Cut-Out Wind Speed  None
Furling Wind Speed 15.6 m/s (35 mph)
Max. Design Wind Speed  60 m/s (134 mph)
Type 3 Blade Upwind
Rotor Diameter 7 m (23 ft.)
Blade Pitch Control None, Fixed Pitch
Overspeed Protection  AUTOFURL
Gearbox None, Direct Drive
Generator Permanent Magnet Alternator

<http://www.accessenergycoop.com/Content/Going-Green/Protecting-Our-Environment/Wind-Energy-Information/Small-Wind-Basics.aspx>

According to several experts, inverters are the least reliable component in small wind systems. But some manufacturers are addressing this issue by adapting inverters from the photovoltaic (PV) market for use with wind turbines. By using an existing, proven product, they have lowered the cost of wind-specific inverters and been able to get them to the market more easily.

<http://www.accessenergycoop.com/Content/Going-Green/Protecting-Our-Environment/Wind-Energy-Information/Small-Wind-Basics.aspx>

Small turbine designs that use induction generators are under development. This approach, common in the early 1980s, avoids the use of power electronics that increase cost and complexity, and reduce reliability.

Many small turbines use variable frequency alternators. Because the voltage and frequency of the electricity generated by these turbines varies with wind speed, the electricity they produce is incompatible with the utility grid. The power must be conditioned with an inverter before it can be interfaced with utility power. Inverters are complex, expensive and, oftentimes the most vunerable trouble prone component of a wind turbine installation.

Induction generators are very similar to the induction motors which are used almost exclusively on every piece of rotating electrical machinery being produced today. They are simple, robust, reliable, efficient and trouble free. Because induction generators contain no solid state components, they are not subject to voltage transient such as lightning, which can easily damage the sensitive electronic components of an inverter.

BECAUSE INDUCTION GENERATORS MUST HAVE UTILITY POWER AVAILABLE BEFORE THEY CAN PRODUCE POWER, THEY ARE INHERENTLY SAFE AND CANNOT ENERGIZE THE GRID WHEN UTILITY POWER FAILS

Induction generators are also inherently safe. In order to produce power, induction generators take their excitation (reactive power) from the utility grid. If grid power becomes unavailable, the generator will not product power. This eliminates the possibility that the turbine can backfeed power into the grid during a power outage and potentially injure someone working on the lines.

<http://www.aerostarwind.com/induction_generator.html>

The traditional stall concept with the generator coupled to the grid.

<http://www.abb.co.in/product/seitp322/5f641f087db6118cc1256ddb0048752c.aspx>

BENEFITS OF INDUCTION GENERATOR TECHNOLOGY

Induction generator has several benefits to offer for the micro, mini power systems under consideration. These benefits relate to the generator design as follows:

i) Cost of Materials: Use of electromagnets rather than permanent magnets means lower cost of materials for the induction generator. Rare earth permanent magnets are substantially more expensive than the electrical steel used in electromagnets. They also must be contained using additional supporting rings.

ii) Cost of Labor: PM’s require special machining operations and must be retained on the rotor structure by installation of the containment structure. Handling of permanent magnets that are pre-charged is generally difficult in production shops. These requirements increase the cost of labor for the PM generator.

iii) Generator Power Quality: The PM generator produces raw ac power with unregulated voltage. Depending upon the changes in load and speed, the voltage variation can be wide. This is all the more true for generators exceeding about 75 kW power rating.

iv)Fault Conditions: When an internal failure occurs in a PM generator, the failed winding will continue to draw energy until the generator is stopped. For high-speed generators, this may mean a long enough duration during which further damage to electrical and mechanical components would occur. It could also mean a safety hazard for the individuals working in the vicinity. The induction generator on the other hand is safely shut down by de-excitation within a few milliseconds, preventing the hazardous situations.

http://www.electrodynamics.net/documents/electrodynamics_power_gen2002.pdf

Small wind energy converters

(SWECs) for urban or rural applications range in size from

a few hundred watts to thousands of watts (usually with

a rated capacity of less than 100kW) and can be applied

economically for a variety of power demands. These systems

can be used in connection with an electricity transmission

and distribution system, or in stand-alone applications that

are not connected to the utility grid and are appropriate

for homes, farms, or even entire communities.

      1. Inverters integrated into the nacelle (rotor hub);

Controlling a wind turbine’s power output and rotor speed can be one of the largest challenges for designers and manufacturers. Without proper controls wind turbines are not able to achieve their maximum efficiency and run the risk of over speeding in high winds and damaging the equipment.

Advanced control enable small wind turbines to interface directly with the utility grid without the use of a battery bank. Several inverters are now available to directly interface with a machine’s controller and synchronize with utility voltage and frequency with very little conversion losses.

Inverters used in the photovoltaics market are being adapted for use with wind turbines. Turbine-specific inverters are also appearing in both single- and three-phase configurations. Another new trend is obtaining certification of most inverters by Underwriters Laboratories and others for compliance with national  interconnection standards.

Skystream 3.7 Grid Tie 2400W Wind Generator

Skystream 3.7 is a down-wind (wind hits the blades on the downwind side of the tower), direct drive (gearless), permanent magnet wind generator. Skystream 3.7 is the first all-inclusive personal wind generator with controls and an inverter built-in, which simplifies the installation process designed specifically for businesses and homes.

Since the inverter is integrated into the nacelle at the top of the tower a single set of wires can be directly connected to your ac electrical system.  No battery bank is required.

<http://www.windenergy.com/about/news/southwest-windpower-receives-swcc-certification-skystream-37>

Skystream 3.7 Specifications
Energy Potential Up to 400 kWh/month*
Rated Capacity 2.4 kW
Energy Monitoring Skyview™ wireless communication & monitoring system
Weight 205 lbs (93 kg)
Rotor Diameter 12 ft (3.72 m) Swept Area: 115.7 ft² (10.87 m²)
Type Downwind rotor with stall-regulation control
Direction of Rotation Clockwise looking upwind
Blade Material Fiberglass reinforced composite
Number of Blades 3
Rated Speed 50-325 rpm
Tip Speed 213 ft/sec. (66 m/s)
Alternator Slotless permanent magnet brushless
Yaw Control Passive
Grid Feeding Southwest Windpower inverter 120/240 VAC 50-60 Hz
Braking System Electronic stall regulation with redundant relay switch control
Cut-in Wind Speed (power production starts) 8 mph (3.5 m/s)
Rated Wind Speed 29 mph (13 m/s)
User Control Wireless 2-way interface remote system
Survival Wind Speed 140 mph (63 m/s)

http://www.windenergy.com/products/skystream/skystream-3.7#upclose

http://www.medioambienteonline.com/web/guest/technology-articles/article/-/article/N2ze/21607/-1/4206/technology-advancements-in-small-wind-turbines

      1. Alternative power and load control strategies:

Wind Turbines are designed to take the energy of the wind and convert it into useful electricity – the stronger the wind the better usually. If the wind is too strong then a turbine can spin so fast it destroys itself with turbine blades ripped off, the alternator damaged by excessive heat, and damage to the turbine tower.

Furling is one method of preventing a wind turbine from spinning too quickly simply by turning the blades away from the direction of the wind.

Furling inherently increases sound levels because the cross-wind operation creates a helicopter-type chopping noise. Aerodynamic models available today cannot accurately predict the rotor loads in the highly skewed and unsteady flows that occur during the furling process, complicating design and analysis. Alternative development approaches include soft-stall rotor-speed control, constant-speed operation, variable-pitch blades, hinged blades, mechanical brakes, and centrifugally actuated blade tips. These concepts offer safer, quieter turbines that respond more predictably to high winds, gusts, and sudden wind direction changes.

Alternatives to rotor furling—yawing and/or tiling out of the wind to protect against excessive rotor speeds in high winds—to control rotor speed. Among the alternatives are stall control, dynamic braking, mechanical braking, and pitch control—methods that have been demonstrated in utility-scale wind generators.

Active Controls

Active controls using independent blade pitch and generator torque can be used to reduce tower-top motion, power fluctuations, asymmetric rotor loads, and even individual blade loads. Actuators and controllers already exist that can achieve most of the promised load reductions to enable larger rotors and taller towers. In addition, some researchers have published control algorithms that could achieve the load reductions (Bossanyi 2003). Sensors capable of acting as the eyes and ears of the control system will need to have sufficient longevity to monitor a high-reliability, low-maintenance system. There is also concern that the increased control activity will accelerate wear on the pitch mechanism. Thus, the technical innovation that is essential to enabling some of the most dramatic improvements in performance is not a matter of exploring the unknown, but rather of doing the hard work of mitigating the innovation risk by demonstrating reliable application through prototype testing and demonstration.

http://www.nrel.gov/docs/fy08osti/41869.pdf

      • Wind Turbine with Passive Pitch Control using Torsion Rubber:

Under normal conditions, the wind turbine rotor will control the rotation on its own. This is achieved by using torsion rubber that automatically adjusts the pitch of the blade.

At high wind speeds, the torsion rubber twists with the centrifugal force to adjust the blade pitch, that controls the rotation speed of the blades. This allows the wind turbine to continue to generate power without a cut – off. This also acts as safety feature when there is no load, controller issues, or electrical brake issues.

http://www.nikkowindpower.com/pdf/nikko-passive-pitch-control-using-torsion.pdf

NIKKO Small Wind Turbine Specifications – NWG-10K

Survival Wind Speed 80m/s
Startup Wind Speed 1.0~1.5m/s
Cut In Wind Speed 2.5m/s
Cut-Out Wind Speed *1 20m/s
Maximum Output (kW) 10kW
 On-Grid Available (3 phase 200V)
Generator Type Permanent Magnet
Output Voltage 3 phase 3 wire 200V
Safety Protection Active ControlBlade Angle Adjustment

Mechanical Brake

Rotor Diameter

φ7.0m

Turbine Weight 1,000kg
Standard Rotor Height (from ground) *2 11m

http://www.nikkowindpower.com/pdf/071409rev_nokko_wind_turbine_spec_list.pdf

<http://www.reuk.co.uk/What-is-Wind-Turbine-Furling.htm>

      1. Reduced rotor speeds:

Other improvements made by manufacturers include slower rotor speeds to reduce sound levels.

<http://www.accessenergycoop.com/Content/Going-Green/Protecting-Our-Environment/Wind-Energy-Information/Small-Wind-Basics.aspx>

In addition, manufacturers are designing the electronics in wind generators for safer and more reliable performance. Some models also feature wireless display units for consumer convenience.

Pasted from <http://www.accessenergycoop.com/Content/Going-Green/Protecting-Our-Environment/Wind-Energy-Information/Small-Wind-Basics.aspx>

Residential 1KW Small Wind Turbine for Eco Friendly residences and businesses

Pasted from <http://www.nikkowindpower.com/residential-compact-wind.html>

Specifications

Rated Output: 1,000W @ 12 m/s (26.8 mph)

Maximum Output (kW): 1.5kW

Survival Wind Speed: 60 m/s

Startup Wind Speed: 1.5 m/s

Wind speed required to start rotation of rotor. The smaller this value is, the Cut-In wind speed becomes smaller

Cut In Wind Speed: 2.5 m/s

Minimum wind speed to generate power.

Power Output

@6 m/s: 140W

@7 m/s: 210W

@8 m/s: 350W

Projected Annual Output

Avg 3 m/s: 500kWh/yr

Avg 4 m/s: 1,000kWh/yr

Avg 5 m/s: 1,800kWh/yr

Independent Battery Hookup: Available

Emergency Power (during power outage): Available

On-Grid: Available

Generator Type: Permanent Magnet

Output Voltage: Single phase 3 wire 200V

Safety Protection: Self-Deflect Function, Blade Angle Adjustment, Electric Brake

Rotor Diameter:  2.0m

Turbine Weight: 70 kg

Standard Rotor Height (from ground) *2: –

Main Applications: Residential; Community environmental educational tools; Emergency Backup Power

Comments: Along with NWG-10K, the only horizontal shaft rotor type wind turbine with active control; Best in Class safety with 3 levels of safety protection

<http://www.nikkowindpower.com/residential-compact-wind.html>

      1. Design standards and certification: The industry is increasing the use of consensus standards in its turbine design efforts for machines with rotor swept areas under 200 m2 (about 65 kW rated power). In particular, IEC Standard 61400-2 Wind Turbines – Part 2: Design Requirements of Small Wind Turbines. Currently, however, a limited number of wind turbines have been certified in compliance with this standard because of the high cost of the certification process. To address this barrier, a Small Wind Certification Council has been formed in North America to certify that small wind turbines meet the requirements of the draft AWEA standard that is based on the IEC standard (AWEA 1996–2007).

http://www.renewable-energy-sources.com/2012/01/13/distributed-wind-energy-technology-trends/

Advance Technologies

Technologies such as unique high-efficiency airfoils, neodymium-iron-boron “super-magnet” generators, pultruded FRP blades, graphite-filled injection molded plastic blades, special purpose power electronics, and tilt-up tower designs will throw twin benefits i.e. lowered costs and increased efficiency.

http://www.upm.ro/InterIng2007/Papers/Section1/11-Dragusin,%20Enoiu,%20Negrea%20lucrarea%202.pdf

<http://www.magnet4less.com/>

      1.  Wind Turbine Noise Solutions to dampen sound

Wind energy is clean energy but not without its usual baggage. Their noise disturbs those who reside in the close proximity with a wind farm. Many a time wind turbines are forced to operate under partial load so that residents and wind farms can exist in peaceful co-existence. But operating under partial load means lower energy production. Even high winds go unutilized in residential areas. The sources of the noises are many. First is the motion of the rotor blades and another is the cogwheels. Cogwheels generate noise in the gearboxes. These are transported to the tower of the wind turbine, where they are emitted across a wide area — and what the residents hear is a humming noise. This noise comes out as if mosquitoes are buzzing constantly.

If an active damping system is employed at wind farms they make this noise somewhat ineffective by producing counter vibrations. To neutralize this humming operators have to install additional damping systems or even substitute the gearbox. And these things are certainly not cost effective. If we examine closely the efficiency of the existing passive damping systems, we will find its success is limited. They operate only at certain frequencies. And it is their greatest drawback because modern wind energy converters rotate and keep changing their rotational speed according to the wind velocity to generate maximum energy. But all this leads to variations in humming sounds too and this limits the usefulness of the modern damping system. Despite noise decreasing measures, humming noises permeate the surrounding areas.

A team of researchers from Schirmer GmbH, ESM Energie – and Schwingungstechnik Mitsch GmbH and the Dr. Ziegler engineering office, IWU are developing an active damping system for wind turbines. The project is financed by the Deutsche Bundesstiftung Umwelt.

This active damping system is obviously an improvement over its predecessors. It senses the change in frequency and neutralizes the noise without affecting the speed of the wind generator. Piezo actuators are the key constituents of this system. These units transform the electric currents into mechanical motion and create “negative vibrations.” These anti-noises offset the vibrations from wind turbines. How do these piezo actuators fine-tune to the changing noise frequencies? Here the research team has devised some sensors that constantly calculate the vibrations coming out from the gearbox. These measurements of frequencies are transferred to the actuator control system. The researchers have already developed a working model of the active vibration dampers, and their next step will be to perform field trials

<http://www.qdfzy.com/en/view.asp?f=39>

      1. Software and wireless display units;

Southwest Windpower Skystream Wireless Remote Display

The Skystream Remote Display allows you to monitor the performance of up to five Skystream wind generators at once. While the Skystream will operate without the remote display, this indoor device allows you to turn the generator on and off.

The display can also be connected to a PC via the optional USB Converter to download data. It works off of either battery battery or can be connected to regular AC power. The wireless unit operates at 916 MHz and can be located up to 1000 feet (300 meters) from the tower.

The display unit, antenna and AC adaptor are all included.

<http://www.altestore.com/store/Alternative-Energy-Products/Skystream-Wind-Turbine-Accessories/Southwest-Wind-Power-Skystream-Wireless-Remote-Display-Kit/p4103/>

GE WindVAR electronics

GE has developed a way to monitor voltage in real time. The WindVAR electronics system delivers reactive power to the grid rapidly and only when it is necessary, which regulates system voltage and stabilizes weak grids. Now that this solution can supply reactive power to the grid, weak rural or remote locations can take advantage of new wind power applications. Wind power projects that are equipped with the WindVAR system, will actually bolster grids that tend to be weak. Additionally, the device has the capacity to offer emergency backup support.

According to GE, “The turbine’s power electronics also reduce the inrush current to about 75 percent of full load current during the wind turbine start-up and provide ride-thru capability.”

Other types of VAR equipment can be expensive and difficult to use, minimizing its efficiencies and making it a less viable solution. WindVAR offers a more advanced solution that supplies reactive power when and where it’s needed. Currently, over 2,000 WindVAR systems are operating on wind turbines worldwide.

Second Wind’s TRITON® Sonic Wind Profiler

The TRITON® Sonic Wind Profiler is the wind industry’s market-leading remote sensing system which sits on the ground, and can measure wind speed and direction up to 200 meters, or 600 feet in the air.

The device is used throughout all phases of the wind project lifecycle. We can use it in the early phases to determine windy locations that you might want to explore further for wind farms. Because it’s mobile, unlike a tower, you can put it up for say a month and if the wind at one location doesn’t seem promising, you can easily move it to another location.

Additionally, once a location is selected, the TRITON can remain in the field for extended periods of time for more intensive studies. “It has a very low power requirement, so it operates autonomously, and we have a satellite data retrieval system, to present the data on the internet. It can be in the remote locations that wind farms often are sited in,” says Giordano.

Once the wind farm is installed, it can verify which turbines are operating as needed. Giordano says, “You can move it from turbine to turbine to provide an upwind, wind speed source, which is the best way to figure out whether or not the turbines are producing as expected.”

This product has been on the market for three years. Currently, 200 units are out in the fields with over a million hours of accumulated data.

The device has been deployed to four continents, including: Australia, Africa, Europe and North America. Giordano says, “The customers altogether are very pleased. They really like the versatility of the product; and its ruggedness—how it has stood up to cold winters and hot summers—in all different locations.” The units can be either solar powered or fuel-cell based, depending on location. Teams at Second Wind monitor and manage the data collection for customers as well. “This keeps reliability high and customers happy,” says Giordano.

Siemens IntegralBlades®

This uniquely designed wind turbine blade is made from fiberglass-reinforced epoxy resin. The cutting edge design offers ideal support in terms of optimal aerodynamics. The IntegralBlade® is made with Siemens’ patented technology and is created during a process that has multiple benefits over conventional blade manufacturing processes. Only one mould set is required in the manufacturing cycle. The blade, therefore, is just one integrated structure in which no joints need to be glued together, resulting in zero weak points in the structure that could be exposed to cracking, lightning or water ingress.

<http://www.energydigital.com/green_technology/new-advances-wind-energy-technology>

      1. Integration of turbines with the tower structures, such as utility or lighting poles.

http://www.cppwind.com/support/papers/papers/windenergy/Building-Integrated_Turbines.pdf

The Bahrain World Trade Center incorporates the first towers in the world to generate part of their own electricity  using wind turbines. It harnesses wind power to produce about 35% of its requirements. Three wind turbines, measuring 29 meters in diameter, are supported by a 30 meter bridge spanning between two towers, were installed at a cost of 1 million Bahraini Dinars.

https://netfiles.uiuc.edu/mragheb/www/NPRE%20475%20Wind%20Power%20Systems/Wind%20Turbines%20in%20the%20Urban%20Environment.pdf

Southwest Windpower’s Air Breeze Turbine integrated with light pole

AIR Breeze Specifications
Manufacturer Southwest Windpower
Energy Potential 38 kWh/month at 13.4 mph (6.0 m/s)
Swept Area 11.5 ft2 (1.07 m2)
Rotor Diameter 46 in (1.17 m)
Weight 13 lb (5.9 kg)
Shipping Dimensions 27 x 12.5 x 9 in (686 x 318 x 229 mm) 17 lb (7.7 kg)
Startup Wind Speed 7 mph (2.2 m/s)
Voltage 12, 24 and 48 VDC
Turbine Controller Microprocessor-based smart internal regulator
Body Cast aluminum with corrosion resistant paint
Blades (3) Injection-molded composite
Alternator Permanent magnet brushless
Overspeed Protection Electronic torque control
Survival Wind Speed 110 mph (49.2 m/s)
Mount* 1.5 in schedule 40 pipe 1.9 in (48 mm) outer diameter

<http://www.windenergy.com/products/air/air-breeze>

Ground based, wind energy extraction systems have reached their maximum capability. The

limitations of current designs are: wind instability, high cost of installations, and small power output of

a single unit. The wind energy industry needs of revolutionary ideas to increase the capabilities of wind

installations. This article suggests a revolutionary innovation which produces a dramatic increase in

power per unit and is independent of prevailing weather and at a lower cost per unit of energy

extracted. The main innovation consists of large free-flying air rotors positioned at high altitude for

power and air stream stability, and an energy cable transmission system between the air rotor and a

ground based electric generator. The air rotor system flies at high altitude up to 14 km. A stability and

control is provided and systems enable   the changing of altitude.

This article includes six examples having a high unit power output (up to 100 MW). The proposed

examples provide the following main advantages: 1. Large power production capacity per unit – up to

5,000-10,000 times more than conventional ground-based rotor designs; 2. The rotor operates at high

altitude of 1-14 km, where the wind flow is strong and steady; 3. Installation cost per unit energy is

low. 4. The installation is environmentally friendly (no propeller noise).

http://arxiv.org/ftp/physics/papers/0701/0701114.pdf

Gearboxes The step-up gearbox used on large turbines today is expected to be replaced in many

future machines. Most small turbine designed for battery charging use a variable

speed, permanent magnet, variable frequency generator connected to a rectifier. As

high power solid state electronics are improved, larger and larger machines are likely

to use AC-DC-AC cyclo converters. This is the case on turbines being developed by

Northern Power Systems (100 kW), the ABB (3 MW), and in some commercial

machines. This trend will increase the use of magnetic materials in future turbines.

Large epicyclical gear boxes used in large ships, may continue to be the drive system

for some large turbines.

Towers Low cost materials are especially important in towers, since towers can represent as much as 65% of the weight of the turbine. Prestressed concrete is a material that is starting to be used in greater amounts in European turbines, especially in off-shore or near-shore applications. Concrete in towers has the potential to lower cost, but may involve nearly as much steel in the reinforcing bars as a conventional steel tower.

http://www.perihq.com/documents/WindTurbine-MaterialsandManufacturing_FactSheet.pdf

CONTRA ROTATING BLADE SYSTEM

The prime mover in wind energy system is the wind turbine. One prevailing trend in wind turbine technology throughout the past couple of decades has been growth in the size of the rotor to realize the advantages of scale and the generally higher winds available at greater heights. Geometrically, consistent up

scaling of blade length shows that the surface stresses at the blade surface, vibratory loads, and loading noise due to aerodynamical and gravitational loads grow in proportion to the length of the blade  However, an alternative mean of overcoming the limitation of the efficiency of the single-rotor system without increasing the size of the rotor and consequently the stress on blades could be the through the adoption of a dual-rotor (contra-rotating) blade system. In addition, the acceptance of wind turbines by the public depends strongly on achieving low noise levels in operation, which largely depends on the level of stress on the blades.

The contra-rotating system is a very old concept that was initially proposed more than 100 years ago. A friend of Betz who is sometimes described as the “father of modern wind energy collection theory”, Hans Honneff, wrote a book on the use of contra-rotation, using two rotors one behind the other, driving the two

halves of an electrical generator, therefore creating a true wind turbine [2]. Currently, the contra concept is used on airplanes, boats, and submarines to increase efficiency while eliminating the asymmetrical torque faced by conventional rotors.

A dual-rotor system can be described as a system consisting of two rotors separated by an appropriate distance (Fig. 1). One of the rotors is rotating in counter-clockwise direction and the other in clockwise direction on the same axis. This system is aerodynamically more efficient than the conventional single-rotor

system. The relative size as well as the appropriate distance between the two rotors should be identified for  best performance. Drawbacks of the dual-rotor system come from mechanical complexity based in the fact that, in order to reverse direction of rotation of one rotor, a gearbox is required. This may increase weight or maintenance and spare parts cost for the system.

The maximum power that can be extracted from a dual-rotor system increases up to 64% of the available energy. It continues to reach 66.7% for an infinite number of rotors. A contra-rotating wind turbine equipped with two 500 kW turbines performed quite well at high wind speeds. The turbine can produce 43.5 % more annual energy than a single rotor turbine of same type. The performance of the system can be improved if it is operated for low wind speeds at the tip-speed-ratio where a maximum Cp is obtained.

http://downloads.mts.hindawi.com/MTS-Files/ME/papers/regular/828739.v1.pdf?AWSAccessKeyId=0CX53QQSTHRYZZQRKA02&Expires=1328279205&Signature=Ln1klu%2B39501pWZroTEeRajUu7M%3D

Combining several or all of these advancements in wind turbine technology can result in quieter, longer lasting and more efficient turbines. Implementing these technology advancements is not without it’s price. As blade and alternator sizes increase so does weight. This leads to more expensive manufacturing costs, more robust tower requirements and higher shipping expenses. Sophisticated controllers and inverters also come with a slightly higher price tag than their predecessors. The end effect results in a more expensive machine. I guess it is true what they say: you get what you pay for.

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