Tails, taxiing, windmill protection from strong winds - Wind power and alternative energy. Protecting a homemade windmill (wind generator) from strong wind Electric generator for a wind farm

The maximum wind speed allowed for the operation of a wind generator with your own hands is 20-25 meters per second. If this indicator of the air flow rate is exceeded, the operation of the station must be limited. Moreover, this should be done even if the windmill is of the slow-moving type.

Of course, it is unlikely that a homemade windmill will be able to spin up to such a speed that it will collapse completely. But there are many cases in history when enthusiasts built their own wind turbines, but did not provide any protection from strong winds. As a result of this, even the strong axles of the automobile generator could not withstand the entire load and broke like matches. Therefore, if the wind is strong, then the pressure on the tail of the plumage increases significantly, and in the event of a sharp change in the direction of the air flow, the generator will spin sharply.

Taking into account the fact that at high wind speeds the generator impeller is able to rotate fast enough, the whole structure turns into a gyroscope that resists any turns. This causes significant loads to be concentrated on the generator shaft between the wind wheel and the frame.

Among other things, a wheel with a diameter of 2 meters will have high aerodynamic drag. With a strong wind, this threatens with high loads on the mast. And therefore, for a more reliable and long-term operation of the wind generator, it is worth worrying about protection.

The easiest way to use for such purposes is the so-called side shovel. This is a very simple device that can significantly save money, effort and time spent on the construction of the station.

The operation of such a device lies in the fact that with a working wind at a speed of 8 m / s, the wind pressure on the structure is lower than the pressure of the protection spring. This allows the generator to operate normally and keep upwind with the help of the feathers. To prevent the windmill from collapsing in operating mode, there is a stretch between the side shovel and the tail. But with a strong wind flow, the pressure on the wind wheel exceeds the force of the spring pressure, as a result, the protection is triggered. When the generator begins to fold, the wind flow hits the wind generator at an angle, which seriously reduces its power.

At very high wind speeds, the protection completely folds the generator, which lies parallel to the direction of the wind flow. As a result, the operation of the windmill almost completely stops. It is worth noting that in this case, the empennage tail is not rigidly attached to the frame, but has the ability to rotate. The hinge, which is used in this case, must be made of high-strength steel, and its diameter must not be less than 12 millimeters.

How to protect a wind generator from a strong wind, because, for example, during a hurricane, the blades can easily fail and fly off. Or, even worse, the mast will not withstand, for example, it will tear off the stretch marks and the wind generator will collapse, sweeping away everything in its path of fall. Of course, for small windmills with a propeller diameter of up to 1.5m, protection against strong winds is not particularly relevant, since there is no such huge pressure on the propeller. But for large windmills, wind protection is obligatory, a large propeller during a hurricane experiences tremendous pressure and here not only the blades can fly off, but also steel cables can be torn or uprooted from the ground. Well, in general, I think it is clear that without protection, especially in the vicinity of people and buildings, it is better not to install a windmill, once a year at least hurricanes still happen.

Storm protection has already been installed in factory wind generators; for small wind turbines, as a rule, an electric brake is used. That is, when a certain speed is reached, the generator phases are pulsed by the controller and the screw loses speed, dropping power. Or protection is not provided at all and the controller slows down by shorting the generator only when the voltage exceeds a certain value, for example 14 volts for a twelve-volt system. For home-made small windmills, home-made controllers (ballast regulators) are often made, which also slow down the windmill when the voltage is exceeded, slow down by turning on an additional load in the form of light bulbs or nichrome spirals, tenns. Or they buy ready-made controllers where everything is already there and braking and forced stop of the windmill.

Large windmills, in addition to the controller, must also have mechanical protection, since large propellers take off huge power in strong winds and go "over the top" and even a complete circuit of the generator does not stop the propeller. In factory windmills, protection is usually made by turning the tail and the screw turns away from the wind. The "wind catchers" are based on the classic method of removing the propeller from the wind by folding the tail, which has long become a classic. This scheme will be discussed further.

Strong wind protection scheme

Defense works like this. When there is no wind and the propeller is not turning, the tail is deflected to its 45 degrees and hangs to the side. With the advent of wind, the propeller turns and begins to turn, and the tail turns into the wind and aligns. When a certain wind speed is exceeded, the pressure on the propeller becomes greater than the weight of the tail, and it turns away, and the tail folds. As soon as the wind weakens, the tail unfolds under the weight again and the propeller becomes in the wind. So that when folding the tail does not damage the blades, a limiter is welded.

Wind turbine protection principle

Here the main role is played by the weight of the tail and its length and plumage area, as well as the distance by which the axis of rotation of the propeller is shifted. There are formulas for the calculation, but for convenience, people wrote Excel spreadsheets on which everything is calculated in two clicks. Below are two plates taken from the forum windpower-russia.ru

Screenshot of the first plate. Enter the data in the yellow fields and get the desired length of the tail and the weight of its tip. The tail area is by default 15-20% of the swept propeller area.

Tail unit calculation

The second plate is slightly different. Here you can change the horizontal angle of the tail. It is considered as 45 degrees in the first table, but here it can be changed in the same way as the vertical deviation. Plus, a spring is added, which additionally holds the tail. The spring is installed as a resistance to tail folding for faster return and to reduce the weight of the tail. The tail area is also taken into account in the calculation.

Download - Tail unit calculation 2.xls

Tail unit calculation 2

Also, the weight of the tail and other parameters can be calculated using these formulas

Fa - axial force on the screw.

According to Sabinin Fa=1.172*pi*D^2/4*1.19/2*V^2
according to Zhukovsky Fa=0.888*pi*D^2/4*1.19/2*V^2,
where D is the diameter of the wind wheel, V is the wind speed;

X - desired offset (offset) from the rotary axis to the axis of rotation of wines;
m is the mass of the tail;
g - free fall acceleration;
l is the distance from the finger to the center of gravity of the tail;
a - angle of inclination of the finger.

For example, a screw with a diameter of 2 meters, wind speed at which the tail should fold = 10 m / s

We consider according to Zhukovsky Fa \u003d 0.888 * 3.1415 * 2 ^ 2 / 4 * 1.19 / 2 * 10 ^ 2 \u003d 165N

Tail mass = 5 kg,
distance from the finger to the center of gravity of the tail = 2m,
finger angle =20 degrees

X=5*9.81*2*sin(20)/165/3.1415*2=0.129 m.

Also a more understandable calculation of the mass of the tail

0.5*Q*S*V^2*L1*p/2=M*L2*g*sin(a), where:
Q - air density;
S - screw area (m ^ 2);
V - wind speed (m/s);
L1 - displacement of the axis of rotation of the wind head from the axis of rotation of the propeller (m);
M - tail mass (kg);
L2 - distance from the axis of rotation of the tail to its center of gravity (m);
g - 9.81 (gravity);
a - angle of inclination of the axis of rotation of the tail.

Well, that's probably all, in the printsepe of Excel tables it is quite enough for the calculation, although you can use formulas. The disadvantage of such a protection scheme is the yaw of the propeller during operation and a somewhat belated reaction to a change in wind direction due to the floating tail, but this does not particularly affect energy generation. In addition, there is another option for protection by the "floating" of the propeller. The generator is placed higher and it capsizes, while the propeller, as it were, lies down turning away from the wind, in this case the generator props up the shock absorber.

Making a wind generator with your own hands

After the generator is purchased, you can start assembling the wind generator with your own hands. The figure shows the device of a wind farm. The method of attachment and location of nodes may be different and depends on the individual capabilities of the designer, but you need to adhere to the dimensions of the main nodes in Fig. 1. These dimensions are selected for this wind farm, taking into account the design and dimensions of the wind turbine.

Electric generator for wind farm

When choosing an electric current generator for a wind farm, first of all, you need to determine the speed of the wind wheel. Calculate the frequency of rotation of the wind wheel W (under load) using the formula:

W=V/L*Z*60,
L=π*D,

where V - wind speed, m/s; L - circumference, m; D is the diameter of the wind wheel; Z is the indicator of the speed of the wind wheel (see Table 2).

Table 2. Wind turbine speed index

If we substitute data for the selected wind turbine with a diameter of 2 m and 6 blades into this formula, we will get the rotation frequency. The dependence of frequency on wind speed is shown in Table. 3.

Table 3. Turnovers of a wind wheel with a diameter of 2 m with six blades depending on the wind speed

Let's take the maximum operating wind speed equal to 7-8 m/s. With stronger winds, the operation of the wind turbine will be unsafe and will have to be limited. As we have already determined, at a wind speed of 8 m/s, the maximum power of the selected wind power plant design will be 240 W, which corresponds to a wind wheel speed of 229 rpm. So, you need to choose a generator with the appropriate characteristics.

Fortunately, the times of total shortage “have sunk into oblivion”, and we will not have to traditionally adapt a car generator from a VAZ-2106 to a wind farm. The problem is that such an automobile generator, for example, the G-221, is a high-speed one with a nominal speed of 1100 to 6000 rpm. It turns out that without a gearbox, our low-speed wind wheel will not be able to spin the generator up to operating speed.

We will not make a gearbox for our “windmill”, and therefore we will select another low-speed generator in order to fix the wind wheel simply on the generator shaft. The most suitable for this is a bicycle motor specially designed for bicycle wheel motors. Such bicycle motors have low operating speed, and can easily work in generator mode. The presence of permanent magnets in this type of motor will mean that there will be no problems with the excitation of the generator, as is the case, for example, with asynchronous AC motors, which usually use electromagnets (field winding). Without current supply to the field winding, such a motor will not generate current during rotation.

In addition, a very pleasant feature of bicycle motors is that they are brushless motors, which means that they do not require replacement of brushes. In table. 4 shows an example of the technical characteristics of a 250 W bicycle motor. As you can see from the table, this bike motor is perfect as a generator for a “windmill” with a power of 240 W and with a maximum wind wheel speed of 229 rpm.

Table 4. Specifications of a 250W bike motor

Making a wind generator with your own hands

After the generator is purchased, you can start assembling the wind generator with your own hands. The figure shows the device of a wind farm. The method of attachment and location of nodes may be different and depends on the individual capabilities of the designer, but you need to adhere to the dimensions of the main nodes in Fig. 1. These dimensions are selected for this wind farm, taking into account the design and dimensions of the wind turbine.

On fig. 1 shows the dimensions of the side shovel (1), the tail with plumage (2), as well as the lever (3), through which the force from the spring is transmitted. The tail with plumage for turning the wind wheel in the wind must be made according to the dimensions in fig. 1 from a profile pipe 20x40x2.5 mm and roofing iron as plumage.

Mount the generator at such a distance that the minimum distance between the blades and the mast is at least 250 mm. Otherwise, there is no guarantee that the blades, bending under the action of wind and gyroscopic forces, will not break on the mast.

Blade manufacturing

A do-it-yourself windmill usually starts from the blades. The most suitable material for the manufacture of low-speed windmill blades is plastic, or rather a plastic pipe. It is easiest to make blades from a plastic pipe - it is a little labor intensive and it is difficult for a beginner to make a mistake. Also, plastic blades, unlike wooden ones, are guaranteed not to warp from moisture.

The pipe must be made of PVC with a diameter of 160 mm for a pressure pipe or sewer, for example SDR PN 6.3. Such pipes have a wall thickness of at least 4 mm. Pipes for non-pressure sewage will not work! These pipes are too thin and fragile.

The photo shows a wind turbine with broken blades. These blades were made from a thin PVC pipe (for non-pressure sewage). They buckled under the pressure of the wind and crashed against the mast.

The calculation of the optimal blade shape is quite complicated and there is no need to bring it here, let the professionals do it. It is enough for us to make the blades using the already calculated template according to Fig. 2, which shows the dimensions of the template in millimeters. You just need to cut out such a template from paper (photo of the blade template on a scale of 1: 2), then attach it to the pipe 160 mm, draw the outline of the template on the pipe with a marker and cut the blades using a jigsaw or manually. The red dots in Fig. 2 shows the approximate location of the blade mounts.

As a result, you should get six blades, shaped like in the photo. In order for the resulting blades to have a higher KIEV and make less noise during rotation, it is necessary to grind off sharp corners and edges, as well as grind all rough surfaces.

To attach the blades to the body of the bicycle motor, you need to use the head of the wind turbine, which is a disc of mild steel with a thickness of 6-10 mm. Six steel strips 12 mm thick and 30 cm long with holes for attaching the blades are welded to it. The disc is attached to the body of the bike motor with bolts with locknuts for the holes for fastening the spokes.

After the manufacture of the wind turbine, it must be balanced. To do this, the wind wheel is fixed at a height in a strictly horizontal position. It is advisable to do this indoors, where there is no wind. With a balanced wind wheel, the blades should not turn spontaneously. If some blade is heavier, it must be ground from the end to balance in any position of the wind wheel.

You also need to check whether all the blades rotate in the same plane. To do this, measure the distance from the end of the lower blade to some nearest object. Then the wind wheel turns and the distance from the selected object to the other blades is measured. The distance from all blades must be within +/- 2 mm. If the difference is greater, then the skew must be eliminated by bending the steel strip to which the blade is attached.

Fastening the generator (bike motor) to the frame

Since the generator is under heavy loads, including from gyroscopic forces, it should be securely fastened. The bicycle motor itself has a strong axle, as it is used under heavy loads. So, its axis must withstand the weight of an adult under the dynamic loads that occur when riding a bicycle.

But on the bicycle frame, the bike motor is mounted on both sides, and not on one side, as it will be when working as a current generator for a wind farm. Therefore, the shaft must be attached to the frame, which is a metal part with a threaded hole for screwing onto the bike motor shaft of the appropriate diameter (D) and four mounting holes for mounting with M8 steel bolts to the frame.

It is advisable to use the maximum length of the free end of the shaft for fastening. To prevent the shaft from turning in the frame, it must be secured with a nut with a lock washer. The bed is best made of duralumin.

For the manufacture of the frame of the wind generator, that is, the base on which all other parts will be located, you need to use a steel plate 6-10 mm thick or a section of a channel of suitable width (depending on the outer diameter of the swivel unit).

Manufacture of the pantograph and rotary assembly

If you simply tie wires to the generator, then sooner or later the wires will twist when the windmill rotates around the axis and break. To prevent this from happening, you need to use a movable contact - a current collector, which consists of a sleeve made of insulating material (1), contacts (2) and brushes (3). To protect against precipitation, the contacts of the current collector must be closed.

For the manufacture of a current collector of a wind generator, it is convenient to use this method: first, contacts are placed on the finished rotary assembly, for example, from a thick brass or copper wire of rectangular cross section (used for transformers), the contacts must already be with soldered wires (10), for which you need to use one - or stranded copper wire with a cross section of at least 4 mm 2. The contacts are covered with a plastic cup or other container, the hole in the support sleeve (8) is closed and filled with epoxy resin. The photo uses epoxy resin with the addition of titanium dioxide. After the epoxy resin has hardened, the part is ground on a lathe until contacts appear.

As a moving contact, it is best to use copper-graphite brushes from a car starter with flat springs.

In order for the wind wheel of the wind turbine to turn in the wind, it is necessary to provide a movable connection between the frame of the wind turbine and the fixed mast. The bearings are located between the support sleeve (8), which is bolted to the mast tube through a flange, and the coupling (6), which is welded by arc welding (5) to the frame (4). To facilitate turning, a swivel assembly is required using bearings (7) with an inner diameter of at least 60 mm. Roller bearings are best suited because they are better at absorbing axial loads.

Protecting a wind farm from hurricane winds

The maximum wind speed at which this wind farm can be operated is 8-9 m/s. If the wind speed is higher, the operation of the wind farm should be limited.

Of course, this proposed type of DIY windmill is low-speed. It is unlikely that the blades will spin up to extremely high speeds, at which they collapse. But if the wind is too strong, the pressure on the tail becomes very significant, and with a sharp change in wind direction, the wind generator will turn sharply.

Given that the blades rotate rapidly in strong winds, the wind wheel turns into a large heavy gyroscope that resists any turns. That is why significant loads arise between the frame and the wind wheel, which are concentrated on the generator shaft. There are many cases when amateurs built wind turbines with their own hands without any protection from hurricane winds, and due to significant gyroscopic forces, the strong axles of automobile generators broke due to significant gyroscopic forces.

In addition, a six-bladed wind wheel with a diameter of 2 m has significant aerodynamic resistance, and in strong winds it will significantly load the mast.

Therefore, in order for a home-made wind generator to serve for a long time and reliably, and the wind wheel does not fall on the head of passers-by, it is necessary to protect it from hurricane winds. The easiest way to protect a windmill is with a side shovel. This is a fairly simple device that has proven itself in practice.

The operation of the side shovel is as follows: with a working wind (up to 8 m / s), the wind pressure on the side shovel (1) is less than the stiffness of the spring (3), and the windmill is installed approximately downwind with the help of plumage. In order for the spring not to fold the windmill when the working wind is more than necessary, an extension (4) is stretched between the tail (2) and the side shovel.

When the wind speed reaches 8 m/s, the pressure on the side shovel becomes stronger than the force of the spring, and the wind generator begins to fold. In this case, the wind flow begins to run into the blades at an angle, which limits the power of the wind wheel.

In very strong winds, the windmill folds completely, and the blades are installed parallel to the direction of the wind, the operation of the windmill practically stops. Please note that the empennage tail is not rigidly connected to the frame, but rotates on a hinge (5), which must be made of structural steel and have a diameter of at least 12 mm.

The dimensions of the side shovel are shown in fig. 1. The side shovel itself, as well as the plumage, is best made from a profile pipe 20x40x2.5 mm and a steel sheet 1-2 mm thick.

As a working spring, any carbon steel springs with a protective zinc coating can be used. The main thing is that in the extreme position the spring force is 12 kg, and in the initial position (when the windmill does not fold yet) - 6 kg.

For the manufacture of extensions, a steel bicycle cable should be used, the ends of the cable are bent into a loop, and the free ends are fixed with eight turns of copper wire with a diameter of 1.5-2 mm and soldered with tin.

Wind turbine mast

As a mast for a wind farm, you can use a steel water pipe with a diameter of at least 101-115 mm and a minimum length of 6-7 meters, provided that the area is relatively open, where there would be no wind obstacles at a distance of 30 m.

If the wind farm cannot be installed in an open area, then nothing can be done. It is necessary to increase the height of the mast so that the wind wheel is at least 1 m higher than the surrounding obstacles (houses, trees), otherwise the power generation will significantly decrease.

The base of the mast itself should be installed on a concrete platform so that it does not squeeze into the soggy soil.

Galvanized steel mounting cables with a diameter of at least 6 mm should be used as stretch marks. Stretch marks are attached to the mast with a clamp. At the ground, the cables are attached to strong steel pegs (from a pipe, channel, angle, etc.), which are buried in the ground at an angle to a full depth of one and a half meters. It is even better if they are additionally monolithic at the base with concrete.

Since the mast assembly with the wind turbine has a significant weight, for manual installation it is necessary to use a counterweight made of the same steel pipe as the mast or wooden beam 100x100 mm with a load.

Wiring diagram of a wind farm

The figure shows the simplest battery charging circuit: three outputs from the generator are connected to a three-phase rectifier, which is three diode half-bridges connected in parallel and connected by a star. Diodes must be rated for a minimum operating voltage of 50V and a current of 20A. Since the maximum operating voltage from the generator will be 25-26 V, the outputs from the rectifier are connected to two 12 volt batteries connected in series.

When using such a simple circuit, the batteries are charged as follows: at a low voltage of less than 22 V, the batteries are charged very weakly, since the current is limited by the internal resistance of the batteries. At a wind speed of 7-8 m/s, the generated voltage of the generator will be in the range of 23-25 ​​V, and an intensive process of charging the batteries will begin. At higher wind speeds, the operation of the wind generator will be limited by the side shovel. To protect the batteries (during emergency operation of the wind farm) from excessive high current, the circuit must have a fuse rated for a maximum current of 25 A.

As you can see, this simple scheme has a significant drawback - with a calm wind (4-6 m / s), the battery will practically not be charged, and it is precisely such winds that are most often found on flat terrain. In order to recharge the batteries in light winds, you need to use a charge controller that is connected in front of the batteries. The charge controller will automatically convert the required voltage, also the controller is more reliable than a fuse and prevents overcharging of batteries.

To use rechargeable batteries to power household appliances designed for 220 V AC voltage, you will need an additional inverter to convert 24 V DC voltage of the appropriate power, which is selected depending on the peak power. For example, if you connect lighting, a computer, a refrigerator to the inverter, then a 600W inverter is enough, but if you plan to use an electric drill or a circular saw (1500W) at least occasionally, then you should choose a 2000W inverter.

The figure shows a more complex electrical circuit: in it, the current from the generator (1) is first rectified in a three-phase rectifier (2), then the voltage is stabilized by the charge controller (3) and charges the batteries at 24 V (4). An inverter (5) is connected to power household appliances.

The currents from the generator reach tens of amperes, so copper wires with a total cross section of 3-4 mm 2 should be used to connect all devices in the circuit.

It is desirable to take the capacity of the batteries at least 120 a / h. The total capacity of the batteries will depend on the average wind intensity in the region, as well as on the power and frequency of the connected load. More precisely, the required capacity will be known during the operation of the wind farm.

Wind farm maintenance

The considered low-speed do-it-yourself wind generator, as a rule, starts up well in light winds. For the normal operation of the wind generator as a whole, you must adhere to the following rules:

1. Two weeks after launch, lower the wind generator in light wind and check all fasteners.

The increase in user interest in alternative sources of electricity is understandable. The lack of opportunities to connect to centralized networks forces the use of other methods of providing housing or temporary residences with electricity. The share is constantly growing, since the acquisition of an industrial design is a very costly business and is always quite effective.

When creating a windmill, one should take into account the possibility of heavy gusts of wind and take appropriate measures to protect the structure from them.

Why do you need protection from strong winds?

Wind turbine operation designed for a certain wind force. Usually, average indicators typical for a given region are taken into account. But when the wind flow increases to critical values, which sometimes happens in any area, there is a risk of device failure, and in some cases - complete destruction.

They are equipped with protection against such overloads either by current (if the permissible voltage value is exceeded, an electromagnetic brake is activated), or by rotation speed (mechanical brake). Homemade designs also need to be equipped with similar devices.

Impellers, especially those equipped with, at high speeds of rotation, begin to act on the principle of a gyroscope and retain the plane of rotation. Under such conditions, the tail cannot do its job and orient the device along the flow axis, which leads to breakdowns. This is possible even if the wind speed is not too high. Therefore, a device that slows down the speed of the impeller is a necessary design element.

Is it possible to make a device with your own hands?

Making a fixture is quite possible. Moreover, it is an absolute necessity. Brake device should be provided at the design stage of the windmill. The operating parameters of the device must be calculated as carefully as possible so that its capabilities are not too low compared to the actual needs of the structure.

First of all, you need to choose a way to implement the braking device. Usually, simple and trouble-free mechanical devices are used for such designs, but electromagnetic samples can also be created. The choice depends on which winds prevail in the region and what is the design of the windmill itself.

The easiest option is to change the direction of the rotor axis, which is done manually. To do this, you only need to install a hinge, but the need to go outside in strong winds is not the best solution. In addition, it is not always possible to manually stop, since at this moment you can be far from home.

Operating principle

There are several mechanical ways to brake the impeller. The most common options for horizontal windmill designs are:

• rotor deflection from the wind with the help of a side blade (stopping by the folding tail method);
• rotor braking by means of a side blade.

Vertical structures are usually braked by means of weights hung on the outer points of the blades. With an increase in the rotation speed, under the action of centrifugal force, they begin to put pressure on the blades, forcing them to fold or turn sideways to the wind, which causes the rotation speed to decrease.

Attention! This method of braking is simple and most effective, allows you to adjust the speed of rotation of the impeller, but is applicable only for vertical structures.

Tail folding defense method

A device that steers away from the wind by folding the tail allows you to smoothly and quite flexibly adjust the speed of rotation of the rotor. The principle of operation of such a system is to use a side lever installed in a horizontal plane perpendicular to the axis of rotation. The rotating impeller and arm are rigidly connected, and the tail is attached through a spring-loaded swivel joint acting in a horizontal plane.

At nominal values ​​of wind force, the side arm is not able to move the rotor to the side, as the tail directs it into the wind. When the wind increases, the pressure on the side blade increases and exceeds the force of the spring. In this case, the rotor axis turns away from the wind, the impact on the blades is reduced and the rotor slows down.

other methods

The second method of mechanical braking is similar in design, but the side blade acts differently - when the wind intensifies, it begins to put pressure on the rotor axis through special pads, slowing down its rotation. In this case, the rotor and tail are mounted on the same shaft, and the swivel with a spring is used on the side lever.

At normal wind speeds, the spring holds the lever perpendicular to the axis, when strengthened, it begins to deviate towards the tail, pressing the brake pads to the axis and slowing down the rotation. This option is good for small blade sizes, since the force applied to the shaft to stop it must be quite large. In practice, this option is used only at relatively low wind speeds; with squall gusts, the method is ineffective.

In addition to mechanical devices, electromagnetic devices are widely used. As the voltage rises, a relay starts to operate, attracting the brake pads to the shaft.

Another option that can be used for protection is to open the circuit when too high voltage occurs.

Attention! Some methods only protect the electrical part of the complex without affecting the mechanical elements of the structure. Such methods are not able to ensure the integrity of the windmill in the event of sudden heavy winds and can only be used as additional measures, acting in tandem with mechanical devices.

Scheme and protection drawings

For a more visual representation of the principle of operation of the braking device, consider a kinematic diagram.

The figure shows that the spring in the normal state keeps the rotating assembly and tail on the same axis. The force created by the wind flow overcomes the resistance of the spring when the speed increases and gradually begins to change the direction of the rotor axis, the wind pressure on the blades decreases, due to which the rotation speed drops.

This scheme is the most common and effective. It is easy to perform, allows you to create a device from improvised materials. In addition, setting this brake is simple and comes down to selecting a spring or adjusting its force.

Attention! The maximum angle of rotation of the rotor is not recommended to be more than 40-45°. Large angles contribute to the complete stop of the windmill, which then starts with difficulty in uneven squally winds.

Calculation procedure

Calculation of the braking device pretty complicated. It will require various data, which is not easy to find. It is difficult for an unprepared person to make such a calculation, the probability of errors is high.

However, if self-calculation is necessary for any reason, you can use the formula:

P x S x V 2 = (m x g x h) x sinα, where:

• P is the force applied to the screw by the wind flow,
• S is the area of ​​the propeller blades,
• V - wind speed,
• m - mass,
• g - free fall acceleration (9.8),
• h is the distance from the hinge to the spring attachment point,
• sinα - angle of inclination of the tail relative to the axis of rotation.

It should be borne in mind that the values ​​obtained from independent calculations require a correct interpretation and a complete understanding of the physical essence of the process occurring during rotation. In this case, they will not be correct enough, since the subtle effects that accompany the operation of the windmill will not be taken into account. However, the values ​​calculated in this way will be able to give the order of magnitude required for the manufacture of the device.

The process of creating a wind turbine is accompanied by a lot of expenses and requires a variety of actions, which in itself forces the structure to be protected as much as possible from the possibility of destruction. If there is a foreseeable danger of destruction or failure of the complex, then the creation and use of protective devices should not be neglected in any case.

Wind water aerators

I decided to post my work in a separate thread.
There were many experiments and tests (and now, at the moment, all new ideas are being tested), many mistakes, but successful solutions were also found, which, by the way, have already worked to save the fish.
Why a separate topic - I suggest that those who are interested discuss exactly the constructive parts. Maybe together we can find better solutions.
An Internet search did not give any results either 3 years ago or now. Now there are links to my videos on YouTube
To be continued...