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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Not flour, but current. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Alternative energy sources To develop and implement a home-made power plant project, an amateur designer will need to first analyze the features of an object that should be supplied with electricity (a separate building, a homestead, a tourist base, several houses, etc.), as well as a water flow rate and the possibility of obtaining a level difference using it hydraulic equipment. If it turns out that a micro HPP should operate at a constant load, with a constant (during the day) power consumption, the water flow is regulated by a debit limiter. In the simplest case, this can be a plate (board, etc.) fixed between two guides. Depending on the current situation, it is easily placed in a position below or above the "norm". And there is no urgent need to use storage batteries. In the case of a significant difference in electricity consumption (especially when the "scissors" exceed a kilowatt-hour), a battery becomes highly desirable. The flow rate of water and the height from which the flow rushes to the turbine are the main factors in the power delivered by the hydroelectric power station to the load. Without them, and in our calculations, as they say, we can not do. Water flow measurement is carried out using a stopwatch and a float, on a fixed section of the river (canal, etc.). The reference length of this section is about 10 m. And the timed value, during which the float will pass these 10 m, will make it easy to calculate the speed of the flow itself. But what is the cross section of the channel? Appropriate measurements are performed at three points. According to the averaged data, the cross section is found. Knowing, in addition, the speed, the debit itself is calculated.
Creating the desired water level difference (transport channel) requires certain hydraulic engineering works; quite voluminous, but absolutely necessary corresponding structures (see Fig.). The energy potential of the hydroflow is calculated by the formula: Wn=mgh, where Wn - potential energy; m is the mass of water that falls on the turbine in one second (this is where the previously found flow rate comes in handy!); g - free fall acceleration equal to 9,8 m/s2; h is the height of the water fall (before the turbine exits). The power that can ideally be obtained from a turbine offered for self-manufacturing is approximately 10 kW. Working in a real micro hydroelectric power station, a variant of which is shown in the figure, such a turbine is capable of delivering 800 W to the load (taking into account the inevitable losses here). Based on this, the generator was also selected. It has the following parameters: 800 W, 24 V, 700 rpm. If we take into account the fact that in the evening and at night, electricity is mainly used for lighting (it is not consumed only for 3-4 hours), and during the day it is used to power 1-2 refrigerators, that is, it apparently makes sense to accumulate it in batteries , connected for charging and operation in a network with a voltage of 24 V. But it is required that the batteries be located as close as possible to the switchboard. After all, the losses here grow in proportion to the length of the line and the cross section of the electric cable. Fortunately, they do not go beyond the "norm" in our 150-meter line, which uses a cable with a total cross-section of aluminum conductors of 25 mm2. So that not a single watt is lost from the energy of water at a microhydroelectric power station, they resort to the fact that the turbine is supplied with blades fixed at an angle that favors the maximum use of the kinetics of the downward flow. The blades following one after another cannot be slowed down by "tired", exhausted water. And friction is kept to a minimum. After all, the inner surface of each of the blades (vanes) and the turbine drum (a kind of "bowl") is carefully polished. The losses in the V-belt transmission, which brings the number of revolutions of the generator to the optimum value, are also extremely reduced. All shafts are on ball bearings. The belts do not slip (their tension is adjusted according to the place where the supports are attached). Now - about other specifics of the proposed design. A three-hundred-kilogram turbine (see Fig. ) is made of two ring-crowns (sheet steel), twelve blades (stainless steel), a tin drum, eight spokes made of steel reinforcement (26 mm in diameter) and a hub bushing mounted on the working shaft with the help of two bolted connections M12. The shaft rotates on two self-aligning (and necessarily sealed - to protect against water) ball bearings. All this is located on two supports that can withstand loads up to a ton. The latter are mounted on four, driven into the ground by 1,5 meters, piles with a diameter of 200-250 mm (from acacia). A flywheel (diameter 700 mm, weight about 80 kg) is placed on the turbine shaft, which is also the driving pulley of a two-stage V-belt transmission. Its rotation speed is 80 rpm (idling) and 60 rpm (under load). To obtain the 700 rpm required by the generator, an intermediate shaft with pulleys was introduced: driven (D = 150 mm) and leading (D = 350 mm). From the last, the torque is already transmitted to the shaft of the DC generator. The pulley here can be considered running (Z=130). And therefore it is better to take it ready for our micro hydroelectric power station. For example, pick up a suitable one from decommissioned agricultural machinery. As, however, and all the previous ones. But you can also make your own. According to the methodology, repeatedly and with sufficient completeness published in the journal, and therefore - well known to many of our do-it-yourselfers. The rest of the construction under consideration, I think, is clear from the illustrations themselves. It should also be noted that this development of a micro hydroelectric power station (for 24 V and 800 W) was successfully implemented on the territory of the Koshava forestry to provide electricity to the tents of the tourist forest base in the Shasa valley (600 meters above sea level). Of course, there are other equally valuable developments. Including those made in Russia. But here, technical thought has been directed since ancient times to the use of the energy of free-flowing water without dams. In particular, a number of documents dating back to the 1th century indicate the construction of mills in Cossack settlements on the Don, rotated by the force of the river current. The wheel of these mills, immersed 4/XNUMX into the rapids, was mounted on a shaft between two canoes or canoes. By the name of the floating base, such structures have since been called "canoe". Moreover, the further development of technical thought in this direction was stimulated by the emerging and increasingly asserting its influence in the national economy of electrical engineering. Unfortunately, the First World War and then the Civil War interrupted scientific research in this area. And only in 1926 (with the growth of industry) the idea of an inexpensive, quickly created damless power plant, using the energy of the river current to supply collective farms, state farms and peasant artels, received its practical development in the design of the "canoe hydroelectric power station engineer B. Kazhinskiy". For the period from 1926 to 1930, 4 such power plants (see Fig. 11) were built. Moreover, according to a project quite accessible for repetition by today's do-it-yourselfers.
With a water wheel diameter of 6 meters with 24 blades-blades (their length and width are respectively 4,5 and 1,0 m) on Russian rivers (with a flow rate of 1 ... 1,5 m / s) the "heart" is such mini hydroelectric power station makes 10-12 revolutions per minute, developing a power of up to 6 kW on the shaft. The latter (thanks to the V-belt multiplier) is already transferred to the electric generator.
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