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Encyclopedia of radio electronics and electrical engineering / Alternative energy sources

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The appearance of dachas and even farms on waste lands remote from the power grid, the galloping rise in fuel and electricity prices brought to life the old ideas of autonomous power supply with the widespread use of natural energy from the sun, wind and water. In particular, interest in mini- and micro-hydroelectric power stations has increased.

The free-flow (model of 1964) daisy-chain hydroelectric power station of V. Blinov served as a prototype for those under review.

The hydroelectric power plants that will be discussed are free-flow, with a rather original turbine from the so-called Savonius rotors strung on a common (maybe flexible, composite) working shaft. They do not require dams and other large-scale hydraulic structures for their installation. Able to work with full efficiency even in shallow water, which, combined with the simplicity, compactness and reliability of the design, make these hydroelectric power plants very promising for those farmers and gardeners whose plots of land are located near small watercourses (rivers, streams and ditches).

Rice. Fig. 1. Savonius rotors for self-made daisy-chain micro hydroelectric power plants (click to enlarge): a, b - blades; 1 - transverse, 2 - end

Unlike dams, free-flow hydropower plants, as is known, use only the kinetic energy of flowing water. To determine the power, there is a formula here:

N=0,5*p*V³*F*n(1),

where N is the power on the working shaft (W), p is the density of water (1000 kt / m³), V - river flow velocity (m/s), F - cross-sectional area of ​​the active (immersed) part of the working body of the hydraulic machine (m²), n - energy conversion efficiency.

As can be seen from formula 1, at a river speed of 1 m/s, ideally (when n = 1) a power equal to only 500 W per square meter of the section of the active part of the hydraulic machine falls. This value is clearly small for industrial use, but it is quite sufficient for the subsidiary farm of a farmer or summer resident. Moreover, it can be increased by the parallel operation of several "hydraulic garlands".

And one more subtlety. The speed of the river in its different parts is different. Therefore, before starting the construction of a micro hydroelectric power station, it is necessary to determine the energy potential of your river using a simple method outlined in the first issue of the magazine for 1996. We only recall that the distance traveled by the measuring float and divided by the time of its passage will correspond to the average flow velocity in this section. It should also be noted that this parameter will change depending on the season. Therefore, the calculation of the structure should be made, guided by the average (for the planned period of operation of the microhydro) speed of the river.

Next, you need to determine the size of the active part of the hydraulic machine and its type. Since the entire micro hydroelectric power station should be as simple and easy to manufacture as possible, the most suitable type of converter is the Savonius rotor of the end design. When working with complete immersion in water, the value of F can be taken equal to the product of the rotor diameter D and its length L, and n=0,5. The rotation frequency f with an accuracy acceptable for practice is determined by the formula:

f=48V/3,14D (rpm) (2).

To make the hydropower plant as compact as possible, the power specified in the calculation should be correlated with the real load, the power supply of which should be provided by the microhydroelectric power station (since, unlike a wind turbine, current will be continuously supplied to the consumer's network here). As a rule, this electricity goes to lighting, powering the TV, radio, refrigerator. And only the latter is included in the work during the day constantly. The rest of the electrical appliances work mainly in the evening. Based on this, it is advisable to focus on the maximum power from one "hydraulic garland" of the order of 250-300 W, covering the peak load with a battery charged from a microhydroelectric power station.

The transmission of torque from the working shaft of the hydraulic power plant to the pulley of the electric generator is usually carried out using an intermediate transmission. However, this element, strictly speaking, can be excluded if the generator used in the design of the microhydroelectric power station has an operating speed of rotation of less than 750 rpm. However, direct communication often has to be abandoned. After all, for the vast majority of generators of domestic production, the operating speed of rotation at the beginning of the "delivery" of power lies in the range of 1500-3000 rpm. This means that additional coordination of the shafts of the hydraulic power plant and the electric generator is needed.

Well, now that the preliminary theoretical part is over, let's consider specific designs. Each of them has its own merits.

Rice. 2. Submersible power plant with a horizontal arrangement of rotors of a transverse type (click to enlarge): 1 - spar-base (beam 150x100, 2 pcs.), 2 - lower cross-beam (board 150x45, 2 pcs.), 3 - middle cross-beam (beam 150x120 , 2 pcs.), 4 - riser (round timber with a diameter of 100, 4 pcs.), 5 upper spar (board 150x45, 2 pcs.), 6 - upper cross member (board 100x40, 4 pcs.), 7 - intermediate shaft (stainless steel, rod with a diameter of 30), 8 - a block of pulleys, 9 - a DC generator, 10 - a "gander" with a porcelain roller and a two-core insulated wire, 11 - a base plate (board 200x40), 12 - a drive pulley, 13 - a wooden knot bearings (2 pcs), 14 - the rotor of the "hydraulic garland" (D600, L1000, 2 pcs.), 15 disk (from boards 20-40 mm thick knocked into a shield, 3 pcs); metal fasteners (including extensions, hubs of the outer discs) are not conventionally shown

Here, for example, is a semi-stationary free-flow microhydroelectric power station with a horizontal arrangement of two coaxial, rotated 90 ° relative to each other (to facilitate self-starting) and rigidly connected transverse-type Savonius rotors. Moreover, the main parts and components of this home-made hydropower plant are made of wood as the most accessible and "obedient" building material.

The proposed micro HPP is submersible. That is, its support frame is located across the watercourse at the bottom and is reinforced with stretch cables or poles (if, for example, there are walkways, a boat pier, etc. nearby). This is done in order to avoid the entrainment of the structure by the watercourse itself.

Of course, the depth of the river at the installation site of the microhydroelectric power station should be less than the height of the support frame. Otherwise, it is very difficult (if not impossible) to avoid water entering the electric generator. Well, if the place where it is supposed to place the microhydroelectric power station has a depth of more than 1,5 m, or there is a high flow and flow rate that varies greatly throughout the year (which, by the way, is quite typical for snow-fed watercourses), then this design is recommended to be equipped with floats. This will also make it easy to move it when installed on the river.

The support frame of the micro hydroelectric power station is a rectangular frame made of timber, boards and small logs fastened with nails and wire (cables). The metal parts of the structure (nails, bolts, clamps, corners, etc.) should be, if possible, made of stainless steel or other corrosion-resistant alloys.

Well, since the operation of such a microhydroelectric power station is often possible in Russia only seasonally (due to the freezing of most rivers), then after the expiration of the operation period, the entire structure pulled ashore is subject to a thorough inspection. Timely change rotten wooden elements, rusted, despite the precautions taken, metal parts.

One of the main nodes of our micro hydroelectric power station is a "hydropower garland" of two rigidly fixed (and constituting a single whole on the working shaft) rotors. Their discs are easy to make from boards 20-30 mm thick. To do this, having made a shield out of them, using a compass, build a circle with a diameter of 600 mm. After that, each of the boards is cut according to the curve obtained on it. Having knocked the blanks together on two slats (to give the required rigidity), they repeat everything three times - according to the number of required disks.

As for the blades, it is advisable to make them from roofing iron. And better - from cylindrical stainless containers (barrels) of suitable size and cut in half (along the axis), in which agricultural fertilizers and other aggressive materials are usually stored and transported. In extreme cases, the blades can also be made of wood. But their weight (especially after a long stay in the water) will greatly increase. And this should be remembered when creating microhydroelectric power plants on floats.

Spike supports are attached to the ends of the "hydroenergy garland". In fact, these are short cylinders with a wide flange and an end slot for a key. The flange is attached to the respective rotor disc with four bolts.

Rice. 3. Plain bearing assembly (click to enlarge): 1; - crimping bracket (St3, strip 50x8, 4 pcs.), 2 - middle frame cross member, 3 - crimping insert (made of hard wood, 2 pcs.), 4 replaceable insert (made of hard wood, 2 pcs.), 5 - M10 bolt with Grover's nut and washer (4 sets), 6 - M8 stud with two nuts and washers (2 pcs.)

To reduce friction, bearings are provided located on the middle crossbars. And since ordinary ball or roller bearings are unsuitable for working in water, they use ... home-made wooden ones. The design of each of them consists of two clamps and insert plates with a hole for the passage of the spike support. Moreover, the middle bearing shells are positioned so that the wood fibers here run parallel to the shaft. In addition, special measures are taken to ensure that the insert plates are rigidly fixed from lateral displacements. Do this with the help of tightening bolts.

As an electric generator in the considered microhydroelectric power station, any of the automobile ones is used. They give out 12-14 V DC and easily dock with both the battery and electrical appliances. The power of these machines is about 300 watts.

Rice. 4. Micro HPP with a vertical arrangement of end-type rotors: 1 - support rod, 2 - lower bearing assembly, 3 - "hydraulic garland" disk (3 pcs.), 4 - rotor (D600, 2 pcs.), 5 - upper bearing assembly , 6 - working shaft, 7 - transmission, 8 - electric generator, 9 - "gander" with a porcelain roller and a two-wire insulated wire, 10 - generator mounting clamp, 11 - movable shield-guide; a, b - blades: extensions at the upper end of the support rod are conventionally not shown

The design of a portable microhydroelectric power station with a vertical arrangement of a "garland" and a generator is quite acceptable for self-production. Such a hydroelectric station, according to the author of the development, is the least material-intensive. The supporting structure of the installation, which fixes its position in the riverbed, is a hollow steel rod (for example, from pipe sections). Its length is chosen based on the nature of the bottom of the watercourse and the speed of the current. Moreover, such that the sharp end of the rod, driven into the bottom, would guarantee the stability of the microhydroelectric power station and its inseparability by its course. It is also possible to use additional stretch marks.

Having determined the active surface of the rotor by formula (1) and measured the depth of the river at the installation site of the microhydroelectric power station, it is easy to calculate the diameter of the Savonius rotors used here. To make the design simple and self-starting, it is advisable to make a "hydraulic garland" of two rotors connected so that the blades of the first are shifted by 90° relative to the second (along the axis of rotation). Moreover, to increase the efficiency of work, the structure on the side of the oncoming flow is equipped with a shield that plays the role of a guide vane. Well, the working shaft is mounted in plain bearings of the upper and lower supports. In principle, with a short operating time of a micro hydroelectric power station (for example, on a camping trip), large-diameter ball bearings can also be used. However, if there is sand or silt in the water, after each use, these units will have to be washed in clean water.

The fastening of the supports to the rod is bolted and welded, depending on the weight of the "hydraulic garland" and the need to disassemble it into parts. The upper end of the working shaft of the hydraulic machine is also the input shaft of the multiplier, which (as the most simple and technological) can be used as a belt.

The electric generator is taken again by automobile. It is easy to attach it to the support rod with a clamp. And the wires themselves coming from the generator must have reliable waterproofing. In the illustrations, the exact geometric proportions of the intermediate transmission are not conventionally shown, since they depend on the parameters of the particular generator you have. Well, transmission belts can be made from an old car camera by cutting it into tapes 20 mm wide, followed by twisting into bundles.

For the power supply of small villages, a daisy-chain microhydroelectric power station designed by V. Blinov is suitable, which is nothing more than a chain of barrel-shaped Savonius rotors with a diameter of 300-400 mm, mounted on a flexible cable stretched across the river. One end of the cable is attached to a hinged support, and the other through a simple multiplier to the generator shaft. At a flow rate of 1,5-2,0 m/s, the chain of rotors makes up to 90 rpm. And the small size of the elements of the "hydropower garland" makes it possible to operate this microhydroelectric power station on rivers with a depth of less than one meter.

I must say that before 1964 V. Blinov managed to create several portable and stationary micro hydroelectric power plants of his own design, the largest of which was a hydroelectric power station built near the village of Porozhki (Tver region). A pair of garlands here drove two standard autotractor generators with a total power of 3,5 kW.

Author: I.Dokukin

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