Alternative energy received from wind turbines is of great interest to society. There are many confirmations to this at the level of real household practice.
Owners of suburban real estate build windmills with their own hands and are content with the result, although the effect can be short-lived. The reason - during the assembly, the wind generator was not calculated properly.
Agree, I would not want to spend time and money on the project, to get an inefficient installation. Therefore, it is important to understand how to calculate the wind generator, and by what parameters to choose the main working units of the wind turbine.
The article is devoted to the solution of these questions. The theoretical part of the material is supplemented by illustrative examples and practical recommendations for the assembly of a wind generator.
Calculation of a wind generator
Where to start calculating the system of reproduction of electricity from wind energy? Considering that we are talking about a wind generator, a preliminary analysis of the wind rose in a particular area seems logical.
Design parameters such as wind speed and its characteristic direction for a given territory are important design parameters. They to some extent determine the level of power of the windmill, which will be achievable.
It is difficult to imagine wind generators of such power. But similar designs exist and work effectively. However, calculations of such structures show a relatively small power compared to traditional energy sources.
What is noteworthy, this process is of a long-term nature (at least 1 month), which is quite obvious. It is impossible to calculate the most probable parameters of the wind speed and its most frequent direction with one or two measurements.
Dozens of measurements will be required. Nevertheless, this operation is really necessary if there is a desire to build an effective productive system.
How to calculate the power of a windmill
Household wind generators, especially those made with their own hands, have not yet had to surprise people with high power. It is understandable. One has only to imagine a massive mast 8-10 m high, equipped with a generator with a rotor blades span of more than 3 m. And this is not the most powerful installation. Only about 2 kW.
To service windmills of such power, helicopters and teams of specialists, numbering up to a dozen people, are used. To calculate such a power plant, an even greater number of performers are involved
In general, if you rely on a standard table showing the ratio of the power of the wind generator and the required span of the rotor blades, there is nothing to be surprised. According to the table, a 10-meter propeller is required for a 10 W windmill.
A screw with a diameter of 14 m will be required for a 500-watt design. In this case, the blade span parameter depends on their number. The more blades, the smaller the scope.
But this is just a theory, due to the wind speed not exceeding 4 m / s. In practice, everything is somewhat different, and the power of domestic installations that have been in effect for a long time has never exceeded 500 watts.
Therefore, the choice of power here is usually limited to the range of 250-500 W with an average wind speed of 6-8 m / s.
Table of the dependence of the power of the wind energy system on the diameter of the rotor and the number of blades. This table can be used for calculations, but taking into account its compilation under a wind speed parameter of up to 4 m / s (+)
From a theoretical point of view, the power of a wind power station is calculated by the formula:
N = p * S * V3/2,
Where:
- p - density of air masses;
- S - total blown area of the propeller blades;
- V - air flow rate;
- N - air flow rate.
Since N is a parameter that dramatically affects the power of the wind generator, the real power of the installation will be close to the calculated value of N.
Calculation of wind turbine screws
When designing a windmill, two types of screws are usually used:
- winged - rotation in the horizontal plane;
- Savonius rotor, Daria rotor - rotation in a vertical plane.
The design of the screws with rotation in any of the planes can be calculated using the formula:
Z = L * W / 60 / V
Where:
- Z - the degree of speed (low speed) of the screw;
- L - the size of the length described by the blades of the circle;
- W - speed (frequency) of rotation of the screw;
- V - air flow rate.
Based on this formula, one can easily calculate the number of revolutions W, the rotation speed.
This is the design of the screw called "Rotor Darier." This version of the propeller is considered effective in the manufacture of wind generators of small power and size. The calculation of the screw has some features
A working ratio of revolutions and wind speed can be found in the tables that are available on the network. For example, for a screw with two blades and Z = 5, the following relation is true:
Number of blades | Degree of speed | Wind speed m / s |
2 | 5 | 330 |
Also one of the important indicators of a wind turbine prop is a step.
This parameter can be determined using the formula:
H = 2πR * tan α,
Where:
- 2π - constant (2 * 3.14);
- R - radius described by the blade;
- tg α - section angle.
Additional information on choosing the shape and number of blades, as well as instructions for their manufacture, is given in this article.
Selection of generators for windmills
Having the calculated value of the rotational speed of the screw (W) obtained by the above method, it is already possible to select (make) the corresponding generator.
For example, when the degree of speed Z = 5, the number of blades equal to 2 and a speed of 330 rpm. At a wind speed of 8 m / s. generator power should be approximately 300 watts.
Generator of a wind power installation "in section". A representative example of one of the possible designs of a generator of a home wind power system, assembled independently
With these parameters, the motor that is used in the construction of modern electric bicycles can be a suitable choice as a generator for a household wind farm. The traditional name of the part is a bicycle motor (production of the PRC).
It looks like an electric cycle motor, on the basis of which it is proposed to make a generator for a home wind turbine. The design of the bicycle motor is ideal for implementation with virtually no calculations and improvements. However, their power is small
The characteristics of the electric cycle motor are approximately as follows:
Parameter | Values |
Voltage | 24 |
Power, W | 250-300 |
Rotational speed, rpm | 200-250 |
Torque, Nm | 25 |
A positive feature of cycle motors is that they practically do not need to be redone. They were constructively developed as low-speed electric motors and can be successfully used for wind generators.
To make a windmill, you can use a car generator or assemble the unit from a washing machine.
Calculation and choice of charge controller
The battery charge controller is necessary for any type of wind power installation, including a domestic construction.
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Standard controller for a windmill
Controller in a wind generator connection diagram
Private Power Station Batteries
Combining solar panels and a windmill
The calculation of this device is reduced to the selection of the electrical circuit of the device, which would correspond to the calculated parameters of the wind system.
Of these parameters, the main ones are:
- rated and maximum voltage of the generator;
- maximum possible generator power;
- maximum possible battery charge current;
- battery voltage;
- ambient temperature;
- environmental humidity level.
Based on the presented parameters, do-it-yourself charge controller assembly or selection of the finished device.
Battery charge controller used as part of a wind power plant. An industrial manufacturing device, choosing which you only need to carefully study the technical specifications for exact coordination with the existing system
Of course, it is desirable to select (or assemble) a device whose circuitry would provide an easy start function in the conditions of flow of weak air flows. A controller designed for use with batteries of different voltages (12, 24, 48 volts) is also welcome.
Finally, when calculating (selecting) the controller circuit, it is recommended not to forget about the presence of such a function as inverter control.
Battery selection for the system
In practice, different types of batteries are used and almost all are quite suitable for use as part of a wind energy system. But the concrete choice will have to be made anyway. Depending on the parameters of the windmill system, the selection of the battery is carried out according to voltage, capacity, charge conditions.
The classic components for home windmills are classic lead acid batteries. They showed good results in a practical sense. In addition, the cost of this type of battery is more acceptable compared to other types.
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Batteries for mini power plants
Wind turbine charge processing equipment
Placement of batteries on racks
Guidelines for selecting batteries
Lead-acid batteries are especially unpretentious to the conditions of charge / discharge, but it is unacceptable to include them in the system without a controller.
If there is a professionally made charge controller in the wind generator set, which has a full-fledged automation system, it seems rational to use AGM or helium batteries.
Battery pack home wind generator. Not the best option, given the chaos of the wires and storage requirements. With this state of energy storage, one cannot count on their long-term effect.
Both types of energy storage devices are characterized by greater efficiency and a long service life, but have high requirements for charging conditions.
The same applies to the so-called helium-type armored batteries. But the choice of these batteries for a household windmill is significantly limited by the price. However, the life of these expensive batteries is the longest in relation to all other types.
These batteries are also distinguished by a more significant charge / discharge cycle, but subject to the use of a high-quality charger.
Calculation of the inverter for a home wind turbine
It should be noted right away: if the design of a home energy wind turbine contains one 12 volt battery, it makes sense to put an inverter on such a system completely.
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Inverter for mini power plants
Operation of the direct current converter
Modular system assembly principle
On average, the household power consumption is at least 4 kW at peak loads. Hence the conclusion: the number of batteries for such power should be at least 10 pieces and preferably under a voltage of 24 volts. For such a number of batteries, it already makes sense to install an inverter.
However, in order to provide fully energy to 10 batteries with a voltage of 24 W each and to stably maintain their charge, a wind turbine with a power of at least 2-3 kW will be required. Obviously, for simple household structures, such a power can not be pulled.
A small power inverter (600 W), which can be used for a small home power installation. You can power a TV or a small refrigerator from such equipment with a voltage of 220 volts. There isn’t enough current for the lamps in the chandelier
However, the inverter power can be calculated as follows:
- Summarize the power of all consumers.
- Determine the time of consumption.
- Determine the peak load.
For a concrete example, it will look like this.
Let there be household appliances as a load: lighting lamps - 3 pcs. 40 W each, television receiver - 120 W, compact refrigerator 200 W. We summarize the power: 3 * 40 + 120 + 200 and we get 440 watts of output.
We determine the power of consumers for an average period of time of 4 hours: 440 * 4 = 1760 watts. Based on the obtained value of power according to the time of consumption, it seems logical to select an inverter from among such devices with an output power of 2 kW.
Based on this value, the current-voltage characteristic of the required device is calculated: 2000 * 0.6 = 1200 V / A.
The classical scheme of reproduction and distribution of energy received from a household type wind generator. However, in order to provide long-term energy with such a number of devices, a sufficiently powerful installation is needed (+)
Actually, the load from the household for a family of three people, where there is full equipment for household appliances, will be higher than calculated in the example. Usually, in terms of load connection time, the parameter exceeds 4 hours taken. Accordingly, the inverter of the wind power system will require a more powerful one.
A preliminary calculation of the windmill is useful not only for its independent assembly. It is also necessary to determine the optimal parameters when choosing a ready-made wind generator.
It is necessary to use the calculated data in any case. Whether it is an industrial power plant or manufactured for living conditions, the calculation of each node always carries with it the maximum efficiency of the device and, most importantly, the safety of operation.
Pre-made calculations determine the feasibility of the project, help to establish how costly or economical the project is.
Have experience in solving such problems? Or have questions about the topic? Please share your skills in calculating and designing a wind generator. You can leave comments and ask questions in the form below.