Hybrid Technology: Save Power Generation Cost

Donauer Al Badi Gulf is a joint venture between Germany’s Donauer and NAS International. Their latest technology is based on a hubrid solution for power generation. A state of art solution including solar based panels is developed for commercial use in Middle Eastern countries.

Due to shortage of electricity during summers, the dependency on diesel generators increases. The latest technology is a combination of disel generators and solar designs to produce electricity from the combination of the two processes. This way a saving of 30-40% generation cost will be seen. The solar process which is cheaper to produce electricity will produce electricity first. An artificial intelligence sensor will detect the deficit and automatically that demand will be fulfilled by the diesel generator.

Remote areas which are not connected to the power grid and which rely on diesel generators can also be benefitted from this technology. Also, such projects, if developed on a larger scale can produce employment for many in the villages. Compared to almost 5 years taken by diesel generator setup, solar projects can be completed in less than a year. Such innovative ideas help save the natural fuel of the nature which are presently used to generate electricity.

Development in Wave Energy Technology

The marine energy industry has been in a state of technological developments recently. Innovations to improve the existing technology we already have are growing by giant strides. The efforts of many companies are being rewarded by various Government organizations which provide financial aid to boost research so that the industry keeps developing forward.

The most recent announcement was made by the Scottish Government which said that a funding of 7.9 million pounds would be given to boost the developments of five marine energy developers. The marine energy market is developing rapidly and keeping that in mind The WATERS program (Water & Tidal Research Development and Demonstration Support) has been released. The Scottish energy market has a potential to benefit their economy by an amount of 4 billion pounds with wave technology. 

Here are some new technologies developed by big brand names in the field of marine energy development.

Albatern: WaveNET technology

Based on the technology of modules and associated nodes, this project has been granted 617,000 pounds under the WATERS2 scheme. With adevelopment and testing phase in the period of late 2012 to late 2013, this project is capable of becoming a 10MW energy proposition.

AWS Ocean Energy: AWS-III Wave Energy Converter (WEC)

Awarded with a grant of 3.9 million pounds, this project has a rated power output of 2.5MW. A full prototype plan is planned in 2014. The technology involved is a multi cell array of flexible membranes.

Nautricity:CoRMaT technology

Aimed to reduce the complexity of operations, the CoRMaT can deliver the tidal power without needing big and heavy supporting structures.

Oceanflow Energy: Oceanflow’s ‘Evopod’ tidal technology

The company’s strategy is to build an operating experience with its 35 kW mono turbine and 70 kW twin turbine Evopod units. The technology involves a semi submerged floating body that is tethered to the seabed by a multi-line spread mooring system.

Scotrenewables Tidal Power: SRTT

This technology features two contra rotating rotors that excite that extract the kinetic energy of the tidal flow, which is converted to electricity though a power take-off system.Company’s WATERS project will involve the design, construction and installation at EMEC of a commercial demonstrator SRTT rated up to 2 MW.

Future Growth

The UK has become a world leader in development of marine energy projects. The UK will be home to the first multi MW commercial array project. Tidal energy has been given due acknowledgment and is considered as a significant contributor the energy demand.Tidal power plays an important role in reducing the dependability on other sources like imported fuels.

Understanding Permanent Magnet Alternator

The output voltage of a permanent magnet alternator depends on the shaft rpm and the load. The higher the rpm, the higher is the voltage. The higher the load for a given rpm, the lower is the voltage.

Current & RPM when connected to load

The current (“amperage”) of a dc generator at any rpm is not governed by its rpm but only by the load put on it. This means that if you run a generator with no load, the current stays at zero no matter how high the rpm is. Only the Generator terminal voltage goes up, but no matter how high the voltage is, if there is no load, there is no current flow.

Frequency

Frequency is related to the rpm and the number of poles the generator has. The more the number of poles, the higher is the frequency at a given rpm.

Wind Permanent Magnet Generators: Battery Charging Application

The market for small wind turbines is providing added electrification needed in remote areas. Many parts of the world are still running on electricity from batteries rather than electrical grids laid by national power corporations.  Telecom companies who have to provide uninterrupted signals in remote areas rely on batteries and generators to get electricity. Another area that uses battery back up is Marine operations.  Off grid wind turbines are proving to be more and more valuble in these situations.

Wind speed is not always constant and it is usually highest during the night hours when people are not using much electricity. Storage of this night-time electricity can charge the battery and become an important method to utilize this electricity that could be lost.

Installing a small wind permanentmagnet generator at remote sites can provide battery charging at a much lower cost than diesel generation or charging stations. Since there are no recurring costs with wind energy, the payback period of the initial setup cost is minimal. 

 In marine environments where the sources of electricity are scarce, batteries are the only viable option and due to high wind speed at sea, these wind turbine battery charging options become a very profitable and convenient source. The overall cost of electricity is reduced. Also with battery usage the overall capacity of the site is doubled. The wind turbine produces the electricity and the battery stores the the extra electricity.

The initial setup is simple. The connection diagram is shown below.

Since the generator is a permanent magnet one, the efficiency obtained in converting mechanical energy to electrical energy is maximum. It is more than 90%, which means more than 90% of the applied mechanical force by the wind is converted into electricity. Compared to 70% provided by traditional generators the amount of wastage is minimal. With such high efficiencies in permanent magnetgenerators, the fuel savings are more, the batteries last longer and overall cost of using electricity is decreased.

Linear Permanent Magnet Generator

Wave energy and tidal power have always been an area of interest in many nations since there is an immense potential  in these energy sources. But, the problem of energy conversion has always been a daunting issue. The traditional energy conversion devices use rotary generators which are high speed  and convert the mechanical force to electricity.

To combat these adversities, growing interest has begun in linear permanent magnet generator for energy conversion. The motion of the rotor in a linear generator is unlike the traditional rotary generator. The  main difference between the two is the motion is going straight up and down  in a linear generator. Because of this linear feature it is possible to couple the motion of the rotor to the reciprocating vertical motion of the ocean waves. By coupling, we can eliminate the use of gearboxes and power take off schemes.  A linear alternator is most commonly used to convert reciprocating (i.e. back-and-forth) motion directly into electrical energy. Because of this ability, this type of permanent magnet alternator is suitable for tidal action and production of electricity from that motion.

Still many considerations are to be taken into account to get the desired efficiency. If the rotor speed is low then i.e. if the frequency is low then a larger construction is required which increases the overall cost. Hence newer designs are required which increases the efficiency along with smaller designs. The linear permanent magnet can be designed in a tubular form as well as a flat structure depending upon the application. Leakage is limited in flat type generators due to symmetrical structure. 

There are several factors which are important to the output of the generator of this type:

·         Number of turns

·         Area of magnetic surface

·         Revolutions/second

·         Tesla of the magnet ( flux intensity)

·         Number of poles

Harnessing the ocean energy has been escalating  since the developments of newer technologies like the permanent magnet alternators. Due to a lack of gearboxes, the maintenance has become easy and inexpensive. The efficiency has increased which has made the overall projects profitable and attractive for people to invest in. 

10 kW Permanent Magnet Generator

10kW Design

The 10kW permanentmagnet generator finds its applications in residential houses on country sides, farming sites, small business setups etc. This has empowered owners to a great extent to reduce utility bills. Other than these, 10kW wind turbine setups are very famous in telecom sector, on or off grid residential areas, rural schools etc. Areas with no electricity grids or with unreliable grids depend on wind energy most of the time.

Very high efficiency and long lasting design have made 10kW system a favorite amongst rural   land owners and farmers. Farmers can expect a very short payback period of less than 5 years which makes their fuel cost go down.

 When designing a 10kW wind turbine, many considerations have to be kept in mind. This is not a very small setup. Issues like weight of the whole turbine, tower, braking system etc play an important role while designing. These windmills have to be made to withstand strong wind conditions since potential of generating electricity during high wind conditions are much more.  Also during strong wind conditions the design and strength of the whole setup comes into play. These winds can damage strong structures easily, hence the material of the wind blades and the tower strength have to be strong enough to withstand winds at 150 km/hr. 10 KW designs have to be robust and dependable for these wind conditions. With a yield of 40,000 -60,000 kWh, users can increase their benefits by selling back the electricity to the national grids. 

10kW Generators in Telecom

During past seven years the installation of telecom grids all over the world has increased many folds. During these competitive times, the telecom companies are expanding their networks to regions where there are no electric grids also. The small wind industry is a key player in this field. Wind turbines like 10kW turbines find a huge potential in these areas by providing uninterrupted power supply throughout the day 365 days a year.

Direct Drive 10kW

The many advantages of 10kWpermanent magnet generator especially a 10 kW are reliability, efficiency and reduction in the overall cost of producing electricity. In the direct drive method power is taken directly from the wind turbine without any reductions which was earlier provided by a gearbox.

A 10kW turbine fitted with a direct driven mechanism offers many advantages:

·         More efficient – No power wastage from belts, chains, gearbox etc

·         Drive Stiffness – Avoiding gearbox results in removal of mechanical backlash, hysteresis and elasticity

·         High torque at low speed

·         Noise reduction

·         Increased lifetime

·         The positioning is faster and accurate

Other features of a 10kW design:

Since a 10kW wind generator becomes a large unit and weight is more, the mounting arrangement like tower is made from high tensile foundations. Mechanical fail safe braking system is incorporated for to stop the turbine operations. Heat sensors, over voltage sensors etc are fitted to keep the machinery safe from any damage. At very high wind speeds which can be a danger to the setup, wind shutdown mechanisms are installed to keep the kit from getting blown away.  

Grid Tie Inverter

The Grid Tie Inverter or synchronous inverter is a special type of power inverter that converts DC electricity into alternating current. A special feature of these types of inverters is that it can feed AC into the existing electrical grid. GTIs are often used to convert DC electricity produced by renewable sources of energy like small wind turbines using permanent magnet generators into AC used to power homes and businesses.

During the period of overproduction from the permanent magnet source, power is routed back to the state grid and hence sold to the local power corporations. But these types of arrangements are possible with special type of grid networks only. These grids are specially manufactured to allow ease of distribution and back feeding.  Residential areas and businesses connected with grid-tied electrical system are permitted in many countries most popular being North America and Europe. There are different compensating ways in which different governments pay the individuals for feeding back the power like “Net metering” or “Feed-in-tariff”. 

Due to this system, the payback period of the renewable energy source like a windpermanent magnet generator decreases and hence the inflow of money is increased for the consumer. Hence using a wind permanent magnet generator is becoming a popular way of generating the power in many nations.

More on Permanent magnet generators and grid tie inverters to come……..Keep following. 

Small Wind Industry moves towards higher kilowatts

Power generation for the small wind industry is experiencing a change. The demand for higher power turbines is increasing in many markets all around the world. Demand is moving from less than 1kw to 5kw and higher. These are generally for home purposes or businesses. Typically the speed of these 5kw horizontal wind turbines range from 200 rpm to 450 rpm at the rated output for the permanent magnet generator. Producing more power than required lets you store the excess generation in batteries which can be used whenever required or even sell the excess generation back to the state grid in countries which allow it. This is an innovative way to generate and store energy which can have low payback periods through PMGL’s wind permanent magnet generators.

Pension Funds: Latest investors in the energy sector

Wind energy companies seek to develop more and more operational wind energy projects and farms every year. Many nations have now pledged to get a major portion of their power from renewable sources of energy like wind, water etc. but funds for these projects are huge and large companies are relying less on loans from banks.

Developers of large renewable energy projects are now targeting investments from pension funds. The expansion plans of many companies and nations have clearly laid down the need of development of renewable energy projects in coming decades. For achieving these goals, pension funds look to be a good investment source since they have a lower threshold for return
on invested capital.

Latest news of Swedish wind power, Arise Windpower, indulging in such new investment plans for upcoming projects show the eagerness of investors to see renewable energy projects as a source of stable and consisting cash flow. If these institutional investors are successfully tapped, then the inflow of capital will get a boost and a long term growth trajectory can be drawn for this industry.

MPPT: Maximum Power Point Tracking 

Maximizing Power output of wind permanent magnet generators with MPPT

Maximum Power Point Tracking or MPPT is an electronic system that allows grid tie inverters and battery chargers to get maximum power from the electricity source. These sources can be solar panels or other renewable sources like wind using permanent magnet alternators. MPPT is a technique through which maximum power is obtained. For wind generators, a controller compares the output of the pm alternator and compares it with the battery voltage. MPPT changes the electrical output voltage and current levels. This available power is provided to the battery in the form of increased current. MPPT detects the optimal power that can be obtained from the system and thus makes changes in the voltage.

Example

Imagine a conventional controller (non MPPT) that connects the alternator (75W) to the battery (12V) to charge a discharged battery. This makes the permanent magnet alternator operate at the battery voltage which may not be the ideal voltage at which the module is capable of producing. The maximum power may be obtained at some other voltage point. By limiting the voltage to 12V, the 75W wind generator system is able to produce power limited to a 53W module. Hence potential is not reached.

With a MPPT system attached arrangement, the controller will detect the voltage at which the module gives its maximum possible voltage which in this example is of 17V. The MPPT system then operates the module at 17V and extracts complete 75W of power. This is irrespective of the current battery voltage.

Wind Turbine for High Speed Winds

Aviation technology has developed designs to harness wind energy at higher speeds. Modern wind turbines are developed with the motive of utilizing more and more wind that strikes the blades of the wind mill. While wind is certainly a renewable source of energy, main problem with wind is its erratic nature. Power per square meter is the cube of the wind velocity.

Wind Energy measurements:

 Kinetic energy of the wind is half of (mass * velocity squared)

Amount of energy moving past a point on the wind turbine therefore depends on the velocity.So the power per unit area comes out to be Kinetic Energy * velocity = MV³ 

Having power being related to the cube of velocity creates a large difference in generation potential for higher wind speeds.

Imagine wind blowing at 60mph gives 27 times more power than wind at 20mph.  

Wind mill efficiency: Windmills cannot have 100% efficiency since the structure itself impedes the flow of the wind. Many times the efficiency depends on the actual wind speed, in correlation to the wind speed design.

Offshore wind:

Wind energy is the most popular renewable source of energy worldwide which can meet electricity demands in a sustainable and clean way. Offshore wind is attractive since it has minimal environmental effects. Also the wind speeds at offshore areas is greater which means increased production as power is related to the cube of the wind velocity. On an average the wind speed increases by 10-20% at off shore wind farms.  But higher energy yield has to compensate the additional maintenance and installation cost. Hence the needs of modern wind turbines which can withstand higher wind speeds and perform efficiently are in great              demand. 

High Speed Wind Permanent Magnet Generator  

There is a demand for wind turbines which start producing at low wind speeds and withstand

high wind speeds too. To continually run at high speeds, foundation, tower (mount), blades, and the permanent magnet generator should be designed properly so that they are strong enough to handle the greater mechanical force and electrical output.

The energy in the wind is proportional to the cube of the wind speed, so a wind turbine operating at very high speed will be under a huge amount of stress but also have the opportunity to generate exponentially. Many manufacturers are using fewer blades for a wind turbine which are longer and can withstand higher speeds. Also windings of the permanent magnet generators should not overheat under this stress. Hence permanent magnet alternators are built to withstand higher wind speeds so that the efficiency of the wind mills is not affected and no damage is done to the internal parts of the generator. All these measures lead to the development of a turbine which withstands speeds which are higher than average. These models are essential since the power obtained from these high speed winds is enormous and should not be wasted. Power

densities are increased if we successfully utilize these high speed winds which are in abundance at many off shore and high latitude areas.

Impressive Efficiency Results obtained during tests conducted by PM Generators Ltd.

PM Generators Ltd. is best known for its world class permanent magnet alternators and best quality products. PM Generators Ltd. has further taken steps to maintain their competency in the industry by conducting efficiency tests the results of which continue to prove that PMGL manufactures the most efficient products in the industry.

Need of the tests

PM Generators Ltd.  makes sure that only the best products are manufactured at its facility. For this purpose it conducts research and development of newer designs with increased efficiencies and better outputs. Similar tests were conducted to test the efficiencies obtained at varying speeds for a recently built permanent magnet alternator. These alternators are perceived as the future of renewable energy generation. Hence it is all the more important to develop more efficiency in this field.

How were the tests conducted?

We know that efficiency is output by input in terms of percentage. For a permanent magnet alternator, the output is in the form of electrical energy and the input is mechanical energy. So we basically needed to measure these two results, the input and the output to calculate the efficiency. Since the output is electrical, we measure the loaded voltage and current. The input side is mechanical energy which is generally provided by a motor. The factors to be considered here are speed and torque. All these quantities help us calculate the efficiency of the machine.

Results

The alternator tested was rated at 750rpm. We required the efficiency not only at the rated speed but also at half speed and the customer's cut-in speed. At the rated rpm, the PMGL alternator achieved 95% efficiency. At 400 rpm it was over 90% efficient and at 200rpm, it was 74%.

  The efficiency of more than 90% at less than the rated speed is worth noting. All alternator models at PM Generators Ltd. give very high efficiencies between 85% and 95%. 

Materials for Wind Permanent Magnet Generator

 Winding Wires

In electric industries, winding wires play a very important role. Their role spreads from generators to transformers, control devices and even pumps. Many materials can be used to make wires. The most popular material used is copper. It is the most accepted material. 

Copper has many advantages which makes it a number one choice. It offers very little resistance. It can be either solid or stranded. Materials which make the water impervious to water, grease, chemicals and oil are needed at this stage. Hence insulation used is of tough grade polymer compounds.

Winding wires are either enameled or coated with various types of varnish and other insulating materials. These wires are used as semi finished material for generating electromagnetic fields and transforming electrical energy.

Varnishing of Winding Wires
A layer of insulation is provided on the wires by varnishing. One important feature of these varnishes is that they must resist high temperatures. Wires are mainly made of conductive material; copper is the most popular as said earlier. Varnishes are made of copolymer which is made from thermoplastic of thermosetting resin. The conductor can be covered with one or more layer of varnishing. These layers can withstand temperatures up to 200°C. The resin is made of any of the followings materials like

Importance and need of Varnishing
Varnishing is done to give extra strength and stability to the copper winding wires. Varnishing increases the ability of these wires to withstand partial discharge and voltage peaks at high temperatures. Thus these varnished insulated windings are used to make coils for permanent magnet alternators.

Bearings

To get the correct efficiency we have to make sure all the necessary measures are taken, like using the correct type of bearings. Sealed ball bearings are commonly used , which should be correct in size and should be able to withstand axial loads.

Sealed Ball Bearings

This type of bearing covers the balls and provides a greater degree of protection because the shield on the sealed ball bearing actually comes into contact with the inner race. But this comes with a price; the high contact pressure of the seal against the rotating inner race increases the    friction and torque losses and can cause a buildup of heat as well.

Magnets

Grade: The grade of a magnet refers to the maximum energy product of the material that composes the magnet. In simple terms it is to tell how strong the magnet is. The higher the grade the stronger the magnet. Unit of energy product is Gauss. Sintered Nd-Fe-B will remain indefinitely; they experience a minute reduction in flux density over time. As long as their physical properties remain intact, they can work well with same efficiency for 100 years.

Magnets will start losing their properties if we heat them above their rate temperatures which is why you cannot overload a permanent magnet generator.

We coat the surfaces of the magnets to protect them from external environment and this will not affect the magnetic properties of the magnets. This increases the air gap between the magnets and the device it is held to. The coatings are very thin and hence the air gap change is negligent.

Precision manufacturing

Bearing Housing: These are very important for safe operation and durability of industrial bearings. These are used to mount the bearings safely.

There are many types of bearing housings available. The possibility of relubrication should be kept in mind while choosing the type. Housings which require relubrication are called relube type others are called maintenance free bearing housing. One other type can be split type and unsplit type. 

Wind Mill Installation

It is very critical to understand the concept of wind before we think of generating electricity from it. There are many basics like wind blade designs, speed of wind, tower height, site location etc. which should be given due importance before going into windmill construction. In this article we will help you understand these things and take you further toward the completion of windmill designing.  

Height:

Turbines are usually 100-120 m high. Increase in the diameter of the blades will increase the height with it. With more height, the wind power increases and power yielded is more. But the costs increases too and hence a balance is sought when deciding on the height of the tower.

Power:

Power in watts yielded by the wind turbine alternator equals the angular velocity (radians per second = 2 pi RPM/60) multiplied by the torque which is in Newton-meters. In case of a permanent magnet alternator, voltage and current are proportional to the RPM. Hence the power is proportional to the square of the RPM.

A very important thing to note here is that wind speed is not a one to one function of the speed. In fact energy increases by the cube of the wind speed. If we double the wind speed, we get eight times the energy. Hence looking at the maps become all the more important. Even a small difference in wind speed within a given area can have a big impact on the amount of energy a wind turbine can generate. It is also one of the reasons why a taller wind tower can make so much of a difference. You can get a sense of the energy produced by the turbine by the power curve graphs given by the manufacturers along with the turbine.

Speed

§  Start-up Speed – The speed at which the blades begin to rotate.

§  Cut-in Speed – The minimum speed at which the turbines will begin producing electricity.

This factor will depend on the wind permanent magnet alternator.

§  Rated Speed - The rated speed is the minimum wind speed at which the wind turbine will generate its designated rated power. For example, a "10 kilowatt" wind turbine may not generate 10 kilowatts until wind speeds reach 25 mph. Rated speed for most machines is in the range of 25 to 35 mph.

§  Cut-out Speed - At very high wind speeds, typically between 45 and 80 mph, most wind turbines cease power generation and shut down. The wind speed at which shut down occurs is called the cut-out speed, or sometimes the furling speed. Having a cut-out speed is a safety feature which protects the wind turbine from damage. Shut down may occur in one of several ways.

Temperature

Utility-scale wind turbine generators have minimum temperature operating limits which apply in areas that experience temperatures below –20 °C. Ice accumulation should always be avoided.

Axis

Vertical axis windturbines (VAWTs) have become popular in recent times. Manufacturers claim that these designs are quiet, efficient, and economical. The rotor shaft in a VAWT is placed perpendicular to the ground. They can be used to generate electricity without getting bothered about placing them in the direction of the wind. These are Omni Directional. Hence they require less parts which makes them less costly and gives ease of maintenance.

They produce a good amount of torque. Its blades have a larger surface area. Hence they can be coupled directly to pumps etc.  Also they are designed to spin at much lower speeds, hence they can function efficiently at higher wind speeds. This decreases noise and vibrations and provides stability.

Horizontal axis wind turbines (HAWTs) are the most common type of wind designs used today. In fact most grid connected commercial wind turbines are today designed with propeller-type rotors mounted on a horizontal axis on top of a vertical tower. These turbines need to be aligned with the direction of the wind, hence allowing the wind to flow parallel to the axis of rotation.

Upwind rotors need a yaw mechanism to keep the axis aligned with wind direction.  Downwind rotors are placed on the lee side of the tower. A great disadvantage in this design is the fluctuations in the wind power due to the rotor passing through the wind shade of the tower which gives rise to more fatigue loads.

Generator torque

With wind permanent magnet alternator, we can set the cut in speeds as well as the cut out speeds. Hence we can generate electricity at a variable speed. Let us take an example. Suppose the turbine speed is 200 RPM at a torque of 40 NM. With permanent magnet generators, the torque generated will be around 90% of 40 NM at same RPM. Other machines are able to provide just around 70% of this torque. 

 

Blade design

The ratio between the speed of the blade and wind speed is called tip speed ratio. High efficiency 3-blade-turbines have tip speed/wind speed ratios of 6 to 7. Modern wind turbines are designed to rotate at varying speeds. Low inertia is achieved by the use of aluminum and composite materials in the blade design. Hence the blades start rotating quickly.

The speed and torque at which a wind turbine rotates must be controlled for several reasons:

§  For keeping the generator within the speed and torque limits.

§  To optimize the aerodynamic efficiency of the rotor in light winds.

§  To keep the rotor and hub within their centrifugal force limits. The centrifugal force from the spinning rotors increases as the square of the rotation speed, which makes this structure sensitive to over speed.

§  To keep the rotor and tower within their strength limits. Because the power of the wind increases as the cube of the wind speed, turbines have to be built to survive much higher wind loads (such as gusts of wind) than those from which they can practically generate power.

§  To facilitate maintenance. Since it is dangerous to have people working on a wind turbine while it is active, it is sometimes necessary to bring a turbine to a full stop.

§  To reduce noise. As a rule of thumb, the noise from a wind turbine increases with the fifth power of the relative wind speed.

When you gather all these basic information regarding the designing of the wind mill, send us the requirements and the conditions and the skilled and experienced R&D heads at PM generators Ltd. will design an alternator which will match the mechanical power output as per the alternator requirement. PM Generators Ltd. will work on the provided specifications and develop a customized design which will suit your requirements to the fullest.  

Gearboxes give way to Direct Drive Turbines

Many turbine manufacturers are moving towards direct drive turbines and leaving the traditional

gearbox turbines behind. Direct drive turbines achieve more reliability, efficiency and reduce the

overall cost of producing electricity. In a direct drive method, power is taken directly from the

mechanical source without any efficiency reductions earlier caused by a gearbox.

Direct drive mechanisms have always been around. They have had mechanical advantages

over traditional methods but since they came with a high price tag and were huge in size,

they never really posed as a threat for the gear box turbine manufacturing process. But many

bigger corporations like Siemens and PM Generators Ltd. have come up with new designs and

technology where turbines are directly connected to permanent magnet generators. The overall

arrangement has resulted in a lighter and affordable model.


The Direct Drive has its reasons to become popular:

• More efficient – No power wastage from belts, chains, gearbox etc

• Drive Stiffness – Avoiding gearbox results in removal of mechanical backlash, hysteresis

and elasticity

• High torque is obtained even at low speed

• Noise reduction – Fewer components and friction reduce overall noise

• Increased lifetime – Less parts result in less failures and increased performance


In a traditional gearbox mechanism, the blades rotate and the shaft connected to it provides the

turning speed to the generator through a gearbox. A rotation speed of about 1500 rpm generates

required electricity. A typical wind turbine will rotate at less than 300 rpm. To increase the

rotations to 1500 rpm, energy is loss in the process. The inner components of the gearbox are

prone to tremendous stress. Eliminating this part simplifies the operation to a larger extent and

makes it easier to maintain for a long period of time. This is especially important for offshore

wind farms because doing maintenance at sea is a lot more complex and expensive than on the

ground.