Basic

Wind energy – is indirect form of solar energy. It is the consequence of difference of temperatures and pressures in the Earth atmosphere. About 2% of solar power converts to wind power. The wind is a huge renewable source of energy. Its power can be used in almost all regions of the Earth. Generating power with the help of wind turbines is very attractive but technically complex task. The problem is the dissipation of wind and its inconstancy.

The operation of wind turbine is simple: wind presses on the blades of turbine, turns the wind rotor connected with the shaft of electric alternator. Alternator generates electric power. In that way wind power converts to electric current.

Wind Power Unit (Wind Turbine) – the unit which converts the energy of forward movement of the wind into electric energy.

The first wind turbine (or wind power generator) was built in Denmark in 1890:

The term “Wind Power Generator” is not proper term for wind turbine as it means actually the generating of wind. The most correct term for these machines is “Wind Turbine” or Wind Power Unit”.

Lots of different types of wind turbines were built by different designer groups. The most famous are:
Horizontal Axis Wind Turbines (HAWT):

Vertical Axis Wind Turbines (VAWT):

Rotor of Wind Turbine – the module which converts the forward movement of the wind into rotating movement of wind turbine.

SRC-Vertical rotor is similar to Gorlov helicoid turbine which is considered as the most efficient in the World. SRC-Vertical rotor actually presents helicoid design technologically improved due to the flattening of the air foils.

            

Download the movie showing transformation of helical turbine into technologically improved rotor (6 air foils).
Download the movie showing transformation of helical turbine into technologically improved rotor (3 air foils).
 
Hub of Wind Turbine – the structure which the rotor with the blades is mounted on. It contains several modules – alternator, bearings and several more aggregates of wind power unit.

Aerodynamic brakes – the extra wings-blades located in the horizontal plane. They help to generate rotation power when the wind speed is under the nominal value. When the wind speed exceeds the nominal, the aerodynamic brakes generate braking torque and stabilize the rotating speed of wind rotor preventing the damage of the wind turbine on high wind speed.

Download movie showing aerodunamic brakes operation.

Magnetic bearing of Wind Turbine – the option module which could be installed into the wind turbine. Due to the magnetic fields directed vertically in opposite ways the rotor of wind turbine “hangs” in the air. Mechanical bearings prevent radial beating. As there are no front bearings, the life time of wind rotor rises several dozens times. The cost of such module generally equals to the cost of alternator.

Alternator of Wind Turbine – the module which converts the rotating movement of wind rotor into electric power. The simple alternator consists of winding and magnets. When coil turn of winding moves through magnetic field, it generates electric current which moves to the output terminals of alternator by wires.

There are many different types of alternators used in Wind Turbines. The most widely distributed are:
•    Magnitoelectric alternators generate the alternative voltage on output. It varies depending on the alternating rotating speed of wind rotor (or wind). Electronic regulator requires to utilize such energy for normal use. It should convert the alternating voltage into the constant or sinusoidal alternating.
•    Alternators with combined excitation (from permanent magnets and excitation winding) generate constant voltage due to its stabilizing with the help of excitation winding (similar to how it is designed in the automobile where the voltage is stable though the crankshaft rotation is alternating). No electronic regulator required if the alternator is used for heating or as a source of electric power for devices operating on 12, 24, 48, 96 Volts Direct Current (VDC).
•    Asynchronous multi-pole alternators can be connected to the grid. They consume the re-active power and generate the active power. In this case they synchronize the self frequency with the frequency of the grid automatically. This type of alternators can be grid-connected only.

Electronic Regulator – the device which converts the alternating voltage of different frequency, phase and amplitude generated by alternator, into the voltage of direct current (VDC).

Mast (Tower) of Wind Turbine – construction which the hub is mounted on. There are several types of masts are used for Wind Turbines:
•    Pipe. The mast consists of sequentially connected pipes. The guy wires or rods required to support the mast in vertical position.
•    Pipe with alternating diameter. Concrete work development required in most cases. Sometimes the guy wires should also be used.
•    Framework. Concrete development is required. No guy wires needed.

Inverter – the device which converts the constant voltage into the alternating of constant frequency. For instance 24 (48 or 96) Volts of direct current into 110 (or 220) Volts of 50 Hz frequency. The process is based on the cutting extra voltage and further generating pulses of constant frequency.
Different inverters generate:
•    Rectangular alternating pulse. Such inverters are the most inexpensive ($100/kW) and can be used for power supply of the most appliances. However some devices (like drill) will be warming while operation. For some types of washers with complex electronic system this type of energy is unacceptable..
•    Quasi-sinusoid. Such pulse is similar to the normal sinusoid but has some small “teeth”. These devices are not expensive ($250/kW), but allow to supply almost all known electric appliances excluding some high technological measuring and other scientific equipment, etc.
•    Sinusoid. These devices are expensive ($1700/kW) and used in industry for power supply of high sensitive equipment.

Battery – the device which allows to reserve the electric power. It can be charged by direct current (not more that 10% of its nominal capacity). For instance the battery of 75 Ampere-hours capacity can be charged by 7.5 Ampere maximum current.

Connecting wires – the wires which connect all devices between each other. Some wires conduct the electric current which is dangerous for man and animals. Some wires conduct the signals from sensors to electric devices.

Diesel-generator (Gas-generator) – the device which consumes diesel fuel (or gasoline or even natural gas) and generates electric power. The most distributed devices generate 110 (or 220) Volts of alternating current of 50 (or 60) Hz frequency.

Commutating controller – the device which “chooses” where the power can be get from – from wind turbine, battery, or diesel-generator. When there is enough wind, the controller gets power from turbine. When there is no wind or the consumption is more than turbine can produce, the controller “draws” power from batteries. When the battery becomes weak, the controller gets power from diesel-generator or grid, per customer solution.

Montage of Wind Turbine – the process of installation, montage and connecting the wiring in accordance with customer requirements.
Dealer which sells the Wind Turbines can install the 3 kW wind turbine at extra payment with the help of special tooling (3 extra masts) in 6-8 hours.
Customer can install the turbine by himself using the appropriate crane or other lifting mechanism. If the wind turbine is installed without mast (roof top, cell tower) then the installation is more simple or complex depending on the local conditions.

Power – the value which shows what job (or energy) was produced per one second (minute, hour).
The term “3 kW power” means that if this power is produced by wind turbine during 1 hour, then the consumer will get 3 kilowatt-hours of energy. The cost of kW-h is known to everyone who pays electricity bills.

The power of wind turbine is relative. If the power of wind turbine is said 3kW, then it cannot be considered that it will constantly produce 3 kW.

According to standards in different countries the power of wind turbines is determined on 10.4, 11 or 11.2 meters per second wind speed. This value is considered as “nominal” power which is reported to customers by manufacturer.
If the wind speed is less than the said value, the wind turbine will produce less power. For instance 3 kW wind turbine will produce the following power on different wind speeds in accordance with cubic parabola:

Power produced by WT-30 (30 kW), will be about 10 times more. Power produced by WT-300, will be about 100 times more, etc.

The desired power can be generated on less wind speed if the dimensions of wind rotor will be increased. The table below shows how the height and diameter of wind rotor go up if the nominal calculated wind speed for specific region goes down. 

The table shows that the less nominal wind speed calculated for 3 kW turbine, the less the rotation speed of wind rotor. I.e. to produce the nominal power the wind turbine has to have larger dimensions on the smaller wind speed. It leads to the increase of the price of the parts and the whole turbine.

For instance to produce 3 kW power on 5 m/sec wind speed, the rotor should have the dimensions of 30 kW wind turbine.

If the nominal wind speed was reduced, then the task of preventing of wind overloading should be considered. If the turbine is calculated for 7 m/sec wind speed, and real speed of the wind is 10 m/sec, the turbine will produce power which greatly exceeds nominal and can damage the electric devices (alternator, inverter, etc.).

To prevent that it’s possible to stabilize the rotation speed by aerodynamic brakes of install more powerful electric equipment.

Gearbox (multiplier) can be used for the reduction of wind turbine rotor dimensions on the same wind speed. It will increase the speed of alternator rotor, i.e. power, up to the required. It is necessary to know that any gearbox has specific efficiency. For instance belt pulley has 85-90% efficiency. It means that due to its use the power reduces on 10-15%.

The family of wind turbines manufactured by SRC-Vertical (1, 3, 30, 55 kW) was chosen in accordance with marketing and sociological research in USA and Russia in 2004-2006. In particular 1 kW turbines are used for portable use. The interval between 3 and 30 kW appeared due to the lack of widely available inverters. The family is closed by 55 kW because the Governmental requirements for 60 kW and bigger wind turbines are more complex.  

Power of inverter – the value which shows maximum power which can be consumed by customer, or maximum power acceptable for this specific device.

Power payback – relative value which depends of the region and people.
For instance 3 kW wind turbine on 6 m/sec average annual speed produces 700 W instant power, or 0.7 kW per hour, or 16.8 kW-hours per day, or 504 kW-hours per month. What does it mean?

Average family consumes 400 kW-hours per month, or 13.3 kW-hours per day, or 0.56 kW per hour.
It seems that turbine produces enough power for the family which consumes even less than being produced. However it’s not true. People don’t consume energy during the day and night (only small power consumption devices are operating – alarm and monitoring system, small lights, low current electronics, clock, etc. on total power 0.1 – 0.2 kW). Instead in the morning and evening the power consumption is “peak” and may increase up to 10 kW and more. In this case the inverter will be switched off or damaged.

The possible ways of solution:
•    Energy saving. For instance do not switch on the washer, microwave oven and vacuum cleaner simultaneously to avoid the consumption which exceeds the number shown in inverter manual. To make these simple calculations read the manuals of the devices.
•    The number of batteries should be enough to provide the peak mode. More powerful inverter required to provide the peak consumption. The number of batteries and inverter power can be calculated as a sum of all power nominals of appliances which will be switched on simultaneously during the peak mode.
•    If there is no plan to save power, then the bigger wind turbine should be purchased. In this case the extra power produced during the day and night, should  be utilized according to customer desire (lighting, watering, water pumping, guarding, or even grid power supply under agreement with local energy company.

Efficiency of Wind Turbine – the value which shows what part of wind power the wind turbine uses.
For instance if the wind power initially was 100%, wind turbine used 40% (Ewt=0.4), losses in alternator 15% (efficiency of alternator in this case 85%), electronic regulator heat losses 15%, wiring losses 15%, then total efficiency of the whole system can be calculated by multiplying of all these numbers.

In our case: Ewt х Ealter х Eelectr х  Ewire х Einvert =
=0.4 х 0.85 х 0.85 х 0.95 х 0.85 = 0.23 (or 23%). This is the amount of energy which the wind turbine gets from 100% wind energy.

It’s obvious that the less the efficiency, the bigger wind turbine you need to install, to get the same amount of energy. And vice versa the more the efficiency, the smaller (and less expensive) turbine is needed for getting the same power.

In general the power of turbine is shown as an output of alternator or electronic voltage regulator. This power in turn is determined by the output voltage of direct current. For instance if the power is shown as 3 kiloWatts (kW), it means that the output of electronic regulator is 3 kW. However the end user doesn’t get this power. In the typical example mentioned above the mutual efficiency of inverter and wiring was 0.85 х 0.95 = 0.8 (or 80%). I.e. the consumer will get 3 kW х 0.8 = 2.4 kW. It has to be taken on account when calculating the amount of required energy or power.

Maximum calculated efficiency (theoretical efficiency) of wind rotor according to Lanchester-Betz limit is 16/27 or 59.3%.

Real efficiency of Horizontal Axis Wind Turbines (HAWT) is 20-30% because they have to be oriented on the wind. The real efficiency of Vertical Axis Wind Turbines (VAWT) is 35% and more because they shouldn’t be directed on the wind.

The calculated efficiency of wind turbines fabricated by SRC-Vertical is 42% and it is not a limit. The calculation was made by Pulse-Vortex Theory, modified in State Rocket Center (Design Bureau named after Academician V.Makeyev). Really proved value is 36-38% measured on the models tested in water channel of Novosibirsk State Academy of Water Transport.

Cost of Wind Turbine - the cost of parts. For each consumer the set of parts is differ in power and variety. It is important to inquire what is included into the basic set. As a rule the parts required for Wind Turbine operation, include rotor with hub, alternator, regulator (controller) on 24 or 48 VDC output, inverter 24/48VDC / 220/110VAC(50/60Hz), batteries on the appropriate voltage, mechanical brake for parking, wires, electric cabinet, lighting rod. However the manufacturer may include another variety of the parts into the basic set and the customer has the right to inquire the list of parts included.
Usually montage is not included into the bsic set. Its cost is appr. 10-20% of the total Wind Turbine set cost and includes concrete works, height montage using the qualified personnel and other works connected with wiring installation in accordance with applicable standards.

Pay-back time of Wind Turbine – the conditional number which depends of region, conditions of operation, etc.
For instance, the initial data is as follows:
•    The cost of 3 kW wind turbine (including montage) is $10,000.
•    Average annual wind speed in the specific region is 6 m/sec (i.e. real average power of turbine is 0.7 kW).
•    Cost of 1 kW-hour of local Energy supply company is 8 cents ($0.08).

The wind turbine produces 0.7 kW per hour, or 16.8 kW-hours per day, or 6132 kW-hours per year, or in cash terms 6132 kW-h х $0.08 = $490 per year.
It means that the pay-back time of this turbine is $10,000 / $490 = 20 years.

If the cost of kW-hour is $0.6 (in the North regions where diesel fuel has to be shipped constantly), then the pay-back period is 2.5 years. If the average wind speed is not 6, but at least 7 m/sec, then it is easy to calculate that the pay-back time is 1.5 years only.

However every wind turbine owner should know that it needs periodical servicing which is harder (and more expensive) in far located regions. These expenses could be calculated easily using the price list.

Servicing of Wind Turbine – package plan of technical servicing of components of wind turbine. Wind power generator (wind turbine) is complex aggregate similar to automobile. And as each auto it requires periodical technical servicing and repairs. The wind turbines of SRC-Vertical in normal temperate climate require the servicing once in 5 years which costs about $200-500 per 1 kW of turbine power, depending on location. The owner and trading company may make an agreement for periodical servicing of wind turbine.

Safety of Wind Turbine – system of data which characterise the mechanical, electrical and ecological parameters of Turbine. The Wind Power Units of SRC-Vertical meet all Internatinal requirements. Moreover they do not generate the elctromagnetic oscillations as Horizontal Axis Turbines. The noise level is under 50 dB at 10 meters around the operating Turbine which meets Lloyd Requirements.

Vibration – harmonic or non-harmonic oscillations of Wind Turbine components. Vibration is one the main parameters of turbines which negatively influences on the environment. Vibrational oscillations are generated by rotor because of its disbalance i.e. the difference of the location of geometrical and actual mass center. Its displacement is caused by the difference of masses of blades, ring segments, traverses. Vibration may occur as the result of icing the rotor, snow/ice in the blades. It may cause the dynamical disbalance of rotor which generates vibromotion which cause the damage of the assembly and its components. It can also be a reason of noise, infra and ultra sound. If the frequency of vibration oscillations or at least one of its harmonics is equal to the self-oscillations of the Wind Turbine component or base/building where the turbine is located, the mutual oscillations may lead to the resonance which can damage the turbine and building. Vibrations can be limited by rotor baancing.

Rotor balancing – pre-operation, operation or automatic balancing
Pre-operation  balancing (including field balancing) has to be made on the stage of reserach and design works, before montage and after montage before operation stage. Automatic balancing is almost never made as it is very hard and expensive. Automatic balancing is used in big (>500 kW) Wind Turbines.

Length of warranty – time of wind turbine operating during which the manufacturer (or trading company or dealer) guarantees the normal operation and obliged to make repairs at its expense. The owner of wind turbine should have the appropriate certificate.

Operation time (Life time) – the time of wind turbine operation during which the technical servicing and repairs are paid by the owner of the turbine.

Wind Farm (Wind Park) – the number of Wind Turbines joined together into one set.