According to the principle of operation, solar concentrators are very different from. Moreover, thermal solar power plants are much more efficient than photovoltaic ones due to a number of features.

The task of a solar concentrator is to focus the sun's rays on a container with a coolant, which can be, for example, oil or water, which absorb solar energy well. Concentration methods are different: parabolic-cylindrical concentrators, parabolic mirrors, or tower-type heliocentric installations.

In some concentrators, the sun's radiation is focused along the focal line, in others - at the focal point, where the receiver is located. When solar radiation is reflected from a larger surface onto a smaller surface (to the surface of the receiver), a high temperature is reached, the coolant absorbs heat, moving through the receiver. The system as a whole also contains a storage part and an energy transmission system.

The efficiency of concentrators is greatly reduced during cloudy periods, since only direct solar radiation is focused. It is for this reason that such systems achieve the highest efficiency in regions where the level of insolation is especially high: in deserts, around the equator. To increase the efficiency of using solar radiation, the concentrators are equipped with special trackers, tracking systems that provide the most accurate orientation of the concentrators in the direction of the sun.

Because the cost of solar concentrators is high and tracking systems require periodic maintenance, their application is mainly limited to industrial power generation systems.

Such installations can be used in hybrid systems in combination with, for example, hydrocarbon fuel, then the storage system will reduce the cost of electricity generated. This will become possible, since the generation will take place around the clock.

Parabolic trough solar concentrators are up to 50 meters long, they look like an elongated mirror parabola. Such a concentrator consists of an array of concave mirrors, each of which collects parallel solar rays and focuses them at a specific point. Along such a parabola, a pipe with a coolant is located so that all the rays reflected by the mirrors are focused on it. To reduce heat loss, the pipe is surrounded by a glass tube, which is stretched along the focal line of the cylinder.

Such concentrators are arranged in rows in a north-south direction, and they are, of course, equipped with solar tracking systems. The radiation focused in the line heats the coolant to almost 400 degrees, it passes through the heat exchangers, generating steam, which rotates the generator turbine.

In fairness, it should be noted that a photocell can also be located in place of the pipe. However, despite the fact that with photovoltaic cells, the size of the concentrators can be smaller, this is fraught with a decrease in efficiency and the problem of overheating, which requires the development of a quality cooling system to solve.

In the California desert in the 80s, 9 power plants were built on parabolic trough concentrators with a total capacity of 354 MW. Then the same company (Luz International) also built a 13.8 MW SEGS I hybrid station at Deggett, which included additional natural gas furnaces. In general, as of 1990, the company had built hybrid power plants with a total capacity of 80 MW.

The development of solar generation at parabolic trough power plants is being carried out in Morocco, Mexico, Algeria and other developing countries with funding from the World Bank.

As a result, experts conclude that today parabolic-cylindrical power plants are inferior both in terms of profitability and efficiency to solar power plants of tower and dish type.

are satellite dish-like parabolic mirrors that focus the sun's rays onto a receiver located at the focus of each such dish. At the same time, the temperature of the heat carrier with this heating technology reaches 1000 degrees. The liquid coolant is immediately supplied to the generator or engine, which is combined with the receiver. Here, for example, Stirling and Brayton engines are used, which can significantly increase the performance of such systems, since the optical efficiency is high and the initial costs are low.

The world record for the efficiency of a parabolic plate type solar plant is 29% efficiency, achieved when converting thermal energy into electrical energy, on a plate plant combined with a Stirling engine at Rancho Mirage.

Thanks to their modular design, dish-type solar systems are very promising, they make it easy to achieve the required power levels for both hybrid consumers connected to the public power grid and for autonomous ones. An example is the STEP project, consisting of 114 parabolic mirrors with a diameter of 7 meters, located in the state of Georgia.

The system produces medium, low and high pressure steam. Low pressure steam is supplied to the air conditioning system of the knitting factory, medium pressure steam is supplied to the knitting industry itself, and high pressure steam is supplied directly to generate electricity.

Of course, dish-shaped solar concentrators combined with a Stirling engine are of interest to the owners of large energy companies. So the Science Applications International Corporation, in collaboration with a trio of energy companies, is developing a system using a Stirling engine and parabolic mirrors that can produce 25 kW of electricity.

In solar power towers with a central receiver, solar radiation is focused on the receiver, which is located at the top of the tower.. Around the tower are placed in large numbers heliostat reflectors. The heliostats are equipped with a biaxial solar tracking system, thanks to which they are always rotated so that the rays are fixedly concentrated on the heat sink.

The receiver absorbs thermal energy, which then rotates the generator turbine.

The liquid coolant circulating in the receiver transfers steam to the heat accumulator. Usually water vapor works with a temperature of 550 degrees, air and other gaseous matter with a temperature of up to 1000 degrees, organic liquids with a low boiling point - below 100 degrees, and liquid metal - up to 800 degrees.

Depending on the purpose of the station, steam can rotate a turbine to generate electricity, or be used directly in some kind of production. The temperature in the receiver varies from 538 to 1482 degrees.

The Solar One tower plant in Southern California, one of the first plants of its kind, originally produced electricity through a water-steam system, delivering 10 MW. Then it underwent modernization, and the improved receiver, now operating on molten salts, and the heat storage system became much more efficient.

This has led to the fact that thermal storage towers marked a breakthrough in solar concentrator technology: electricity in such a power plant can be produced as needed, since the thermal storage system can store heat for up to 13 hours.

Molten salt technology makes it possible to store solar heat at a temperature of 550 degrees, and electricity can now be produced at any time of the day and in any weather. Tower station "Solar Two" with a capacity of 10 MW, became the prototype of industrial power plants of this type. In the future, the construction of industrial stations with capacities from 30 to 200 MW for large industrial enterprises.

The prospects are colossal, but development is hampered by the need for large areas, and the considerable cost of building industrial-scale tower stations. For example, in order to accommodate a 100 megawatt tower station, you need 200 hectares, while for a nuclear power plant capable of producing 1000 megawatts of electricity, you need only 50 hectares. Parabolic-cylindrical stations (modular type) for small capacities, in turn, are more cost-effective than tower ones.

Thus, tower and parabolic concentrators are suitable for power plants from 30 MW to 200 MW, which are connected to the grid. Modular poppet concentrators are suitable for autonomous power supply of networks that require only a few megawatts. Both tower and poppet systems are expensive to manufacture, but provide very high efficiency.

As you can see, parabolic-cylindrical concentrators occupy an optimal position as the most promising solar concentrator technology for the coming years.

Interest in alternative energy is growing steadily. There are many reasons for this, and quite objective ones. The most powerful and stable source of clean energy is the sun. Although the cost of recycled solar energy is still inferior to that produced on an industrial scale, its converters into heat or electricity - solar panels - are purchased or made by many with their own hands. A house with electricity-generating solar panels and heat generators - solar collectors - on the roof, these days is not uncommon in places with a fairly harsh climate, see fig. Moreover, there is nothing to replace such a dignity of the radiation of the Sun as complete independence from the man-made environment and natural disasters.

The picture for illustration was taken “winter” not without reason: modern models of solar collectors are capable of supplying a coolant with a temperature of +85 degrees Celsius to the heating system on a cloudy day with a frost of -20 outside. At a price, such solar plants are quite affordable, but they require a developed production base for the manufacture. If the task is to provide hot water supply in a country house or in a country house during the warm season, when autonomous heating is turned off, then it is quite possible to make a solar collector suitable for this with your own hands. And if you have the skills of a mid-level home master, an installation that will help the heating boiler save a considerable amount of fuel in winter, and the owners will save money on it. Other uses for homemade solar collectors are also possible; at least the water in the pool is heated. The prices of branded designs of this kind are clearly ridiculous in comparison with their capabilities, and there is nothing that one could not do oneself.

With autonomous solar power supply, the matter is more complicated. Let's face it: solar power plants for general use, in all respects superior to traditional thermal power plants, hydroelectric power plants and nuclear power plants, do not exist today. And, until the generation of electricity from the Sun is transferred into space and its spectrum is not used in full for this, it is hardly possible. In Eurasia, the extreme northern points, where the payback period of large solar power plants is at least a little less than their service life, are the islands of the Aegean Sea and Turkmenistan.

However, an individual purchased solar power plant can also be profitable in medium-high latitudes, subject to a thorough feasibility study and the selection of an appropriate model; not the last role in this is played by the stability of power supply in the area. And the concept of a do-it-yourself solar battery can have a quite definite and positive economic meaning for the owner, if some easy and free conditions for its manufacture and operation are met, in the following cases:

How to purchase or make these useful devices yourself, so that later you do not regret wasted money? This is what this article is about. With a small addition about solar concentrators, or solar concentrators. These devices collect solar radiation into a dense beam before passing it on for conversion. In some cases, it is impossible to achieve the required technical indicators of the installation in any other way.

In general, the material is organized into 5 sections with subsections:

1. Essential features of the use of solar energy.
2. Solar collectors (SC), purchased and homemade.
3. Solar concentrators.
4. Solar panels (SAT), in the same order.
5. Proper installation and alignment of the SC and SB.
6. Conclusion in conclusion.

Word to the Kulibins

Amateurs make solar batteries from a variety of improvised materials: semiconductor diodes, transistors, disassembled antediluvian selenium and cuprox rectifiers, copper plates independently oxidized on an electric stove, etc. The maximum that can be powered from them is a receiver or player with a consumption current of up to 50-70 mA at medium volume. More is fundamentally impossible; why - see sec. about SB.

However, it would be completely stupid to blame lovers of technical experiments. Thomas Alva Edison once said: “Everyone knows that this is impossible to do. There is an ignoramus who does not know this. He's the one who makes the invention." In any case, touching the subtleties of high technologies and the depths of matter (and SB is a visible example of both) gives knowledge and the ability to apply them, i.e. quick wits. And they are capital that never depreciates and whose return is higher than any securities.

Nevertheless, even the most general theoretical foundations of all further material are such that the most "slightly on the fingers" does not result in articles - in books. Therefore, we will further limit ourselves to those samples for various occasions that can be made independently at home, not completely forgetting what they were taught at school (there are, by the way, quite a few of them); this is first. Secondly, we will limit ourselves to devices that actually provide heat or current, suitable for domestic and household needs. You then have to take some of the author's statements on faith, or turn to fundamental sources.

What can be expected?

Here is an example of a telephone conversation with a sales manager of a company selling SBs: “And under what conditions does your battery develop the declared power?” - "For any!" – “And in Murmansk (beyond the Arctic Circle) in winter too?” - silence, hang up.

Now let's look at the top map in Fig. below. There - the zoning of the Russian Federation for insolation specifically for the needs of solar energy. Not for farmers, plants over billions of years of evolution of life have learned to use sunlight more economically. Let's say we live in a place where the solar energy flow is 4 kW / h per 1 sq. km. m per day. In the middle latitudes, from the spring to the autumn equinox, and taking into account the change in the height of the standing of the Sun during the day and according to the season, the duration of daylight hours will be something around 14 hours. More precisely, for a specific geographical point, you can calculate on online calculators, there are some.

Then the energy flow of the Sun goes to the circle 4/14 = 0.286 kW/sq. m or 286 W/sq. m. With a solar plant efficiency of 25% (and this is a good indicator), it will be possible to remove 71.5 W of power, thermal or electrical, from the square. If the medium-long-term power consumption (see below) needs 2 kW (this is a typical case), then the converter panel is needed with an area of ​​2000 / 71.5 = 27.97 or 28 square meters. m; this is 7x4 m. Efficiency 25% - is it underestimated? Yes, more can be squeezed out of the panels. A significant part of the following material is devoted to exactly how.

Note: for reference - the solar constant, i.e. the energy flux density of the Sun in the entire radiation spectrum from ultra-long radio waves to super-hard gamma radiation, in space in earth orbit is 1365.7 W/sq. m. At the equator at noon on the days of the equinox (the Sun at its zenith) - about 1 kW / sq. m. Merchants often do not know this, but you should keep in mind.

Well, what about the manufacturers' promises then? The panel, for example, is 1x1.5 m, and a power of 1 kW is declared for it. It seems to be not against physics and astronomy, but in the middle latitudes under the fur coat of the atmosphere it looks clearly unrealistic. They are right, they are not lying. Only measured power on their test bench under special lamps. If they want to be honest with me to the end, let them come and shine them on my panel, and they take electricity for this anywhere.

The map under the first one is needed to additionally determine the price category or the choice of the design of the proposed installation. SB and, especially, SC, capable of working in cloudy weather, are more complicated and more expensive than those that operate only in direct light. In a year 365x24 = 8760 hours. Taking into account the fact that at high latitudes in summer the length of daylight hours is longer, SC or SB may turn out to be paid off in Yakutsk or Anadyr during the estimated operating life, but not in the Moscow Region or Ryazan. Those. also keep in mind that solar energy as a beneficial support to conventional energy is possible not only in the Sahara or the Mojave Desert.

Subtotal

An important conclusion for everything follows from this section: when looking for a panel for purchase or repetition, be primarily interested in the area of ​​\u200b\u200bthe surface that effectively perceives (or absorbs) light, and only calculate everything else from it. Moreover, it may turn out that, according to marketing and consumer ideas, the panel that seems to be the worst in this particular case will come out more profitable than the “cool” one.

collectors

Principle of operation

The work of any SC is based on the greenhouse effect. Its essence is well known: let us take a chamber open on one side with a light-absorbing surface. We close it with a lid that is transparent to visible light (preferably also ultraviolet, UV), but well reflects thermal (infrared, IR) radiation. These conditions are largely met by silicate glass and plexiglass; almost completely - quartz glass and other mineral glasses based on fused quartz.

Note: It is generally wrong to call UV-transmitting mineral glasses as mineral glasses. silicate glass is also mineral. It would be better to keep the former name "quartz glass", because. most of the charge for melting UV-transparent glass is crushed quartz. There are also tourmaline glasses, but not for everyday life - crystals of precious stones are melted down on them.

Sunlight entering the camera will be absorbed by the camera and the camera will heat up. To avoid heat loss, we will supply it with thermal insulation. Then the thermal energy will turn into IR, but it will not be able to go out through the lid and be unable to dissipate. Now the IR has no choice but to heat the heat exchanger placed inside with a heat carrier or the air blown through the chamber. If they are not there, the temperature inside will rise until the temperature difference between inside and outside “pushes” the excess heat through the thermal insulation and thermodynamic equilibrium is established.

What is AChT

To better understand further, you need to know how the pyramidal, or needle, model of a blackbody (black body) works; since we do not need others, further, if we are talking about the blackbody model, we omit the “pyramidal-needle” model everywhere. In Runet, and on the Internet in general, you can’t really find anything about it, but in laboratory practice and technology such ones are successfully used. How it works is clear from Fig. on right. And in this case, the absorption of light in the SC will be the better, the more its coating or the very configuration of the effectively absorbing surface (EAS) is closer in properties to the blackbody model.

Note: A blackbody is a body that absorbs electromagnetic radiation of any frequency. Wood soot, eg. - not blackbody, when photographed through an IR filter, it looks light gray. The pyramidal-needle blackbody model is capable of absorbing any, not only electromagnetic, vibrations. So, in acoustics, foam rubber pyramids are pasted over the inner surfaces of sound chambers.

Purchased SC

If you decide to buy a solar collector, you will have to face a price fork per 1 sq. m of absorbing area in 2000-80 000 rubles. And keep in mind that only the final cost is displayed in appearance, and the EPP area, if prescribed, is in small print. Also, when choosing a model, you should definitely ask if it is equipped with a storage tank and piping elements, see more about them below. Let's try to figure out what explains such a discrepancy and whether it is always justified.

Note: theoretically, the service life of the SC is unlimited. In practice, for more or less decent models, with proper operation, it is at least 15 years. Therefore, with a reasonable choice with a payback, there are no problems, as long as the climate allows them to be used.

Types and purpose

In everyday life, most of all, SCs of 3 types of design are used, see fig. On the left is a flat SC, in the center is a vacuum one, on the right is a compact one. All of them can be performed both non-pressure, on thermosiphon circulation, and pressure. The first ones are 1.5-5 times cheaper than pressure analogues, because in them it is easier to ensure strength and tightness. Non-pressure SCs heat the coolant relatively slowly, therefore they are designed more for hot water supply in the warm season. Tying is simple and inexpensive; sometimes combined with a panel in one construct.

In pressure vessels, the coolant is either pumped by a circulation pump (which makes them volatile), or tap water is supplied to the heat exchanger. This, of course, requires a stronger and more reliable design, plus a complex volatile harness and a controller that controls it. The price increases accordingly. But only pressurized SCs are suitable for the cold season, because. heat up quickly. Most models are all-season; sold in the Russian Federation, taking into account climatic conditions, are most often designed to work together with a heating boiler, i.e. are assistive devices.

Pressure SC are of direct and indirect heating. In the first case, the SC is connected directly to the CO circuit (heating system). In the second, the first one, which receives solar energy, the SC circuit is filled with antifreeze, and the secondary coolant is heated in the heat exchanger of the 2nd circuit.

The latter, of course, are more expensive, because. able to work in cold weather in any climate. The former are mainly used for heating in spring and autumn. Nevertheless, it is directly heated pressure SCs (single-circuit ones) that are most likely to be beneficial for individual CO: in the off-season, at very low power, the efficiency of a solid fuel boiler drops significantly. But just at this time, the thermal power of the SC for the house is enough, while single-circuit ones are relatively inexpensive. It is only necessary to provide for the appropriate shut-off and distribution valves in the CO and in the fall, before the real cold weather, turn off the SC and empty it.

flat

The scheme of a flat SC is shown in fig. on right; the principle of operation is fully consistent with that described above. Such, as a rule, are efficient only in the warm season. Efficiency, depending on the design, lies in the range of 8-60% Water is dispensed with a temperature of up to 45-50 degrees. Pressure pumps are produced extremely rarely, the complexity of the design at the same time makes them uncompetitive with vacuum ones. The heat exchanger seals are designed to be filled with water only, as in summer there is no need for antifreeze. The price (we emphasize - for 1 sq. m of EPP; you need to recalculate yourself each time according to the specification data) is mainly influenced by the following factors:

• Coating (transparent insulation) of glass.
• The type of glass itself.
• The design and quality of the absorbent panel.

The glass coating plays the role, first of all, of an antireflection film in optical devices: it reduces the refraction of light at the interface between the media and the light loss due to lateral reflection. In correctly established summer SCs (see at the end, before the conclusion), these losses are small or, in the southern regions, are not noticeable at all. In addition, the coating is abraded by dust carried by the wind and is most often not covered by the warranty. Therefore, coverage is the first thing you can save on. If there is a noticeable difference in price due to coverage for models similar in terms of technical data, take it “naked”, most likely you will not be disappointed.

Glass itself is the most important element and you need to navigate when choosing, first of all, by it:

1. Mineral - passes UV, which greatly enhances the greenhouse effect.
2. Textured (structured) - has a special microrelief on the surface, which provides almost equal efficiency in direct and diffused light, i.e. in clear and cloudy weather.
3. Mineral structured - combines both of these qualities and, in addition, practically does not give lateral reflection in a fairly wide range of incidence angles without enlightenment.
4. Silicate with additives - structured or not, does not transmit UV, does not reflect IR well and gives significant side reflection without enlightenment. You should not count on an efficiency of more than 20% with it.
5. Organic - with any improvements in 5-7 years, the maximum will become cloudy from dust, but some of its types are able to provide maximum efficiency values.

Proceeding from this, for SC of permanent use, the choice should be made in favor of structured mineral glass. It allows you to get by with a smaller area of ​​the SC and often ultimately win on the cost of the entire installation. At the weekend cottage, the rate of water heating and the initial cost of the collector are also important, so SC with plexiglass is more suitable there. Installation, in addition to being cheap, will be more compact and lighter; for weekdays and for the winter it can be covered with a cover or even taken into the house, so wear resistance in this case is not a determining factor.

Under good glass, the efficiency of the SC depends little on the design of the absorbing panel (absorber). Not that - the absorbing coating (blackening) of the EPP. The properties of various solar absorber coatings are shown in Fig. on right. Regularity - as always, the more effective, the more expensive. Here again it is necessary to calculate different models, reaching a minimum cost of 1 sq. m. m panel. And in general, in any calculations of the SC, one must remember how to save - the greatest savings are achieved by reducing the required area of ​​​​the panel (s). At the same time, sellers are also checked: if, say, the specification declares selective painting and promises an efficiency of 75% - send them to the test bench under the lamps, it's hot as hell. It is clear, after all, that the efficiency of the entire installation cannot be higher than that of its parts.

About the tank

The storage tank for the SC is necessary not only for the sake of convenience. The map above shows the average annual insolation values. For a summer installation, when calculating, they can be increased by about 1.7 times, and for a seasonal spring-summer-autumn - by 25%. But this will only be an average value, now for the season. And depending on the weather, the value of insolation can "jump" from day to day by 1.5-3 times, depending on the local climate. The heated water accumulated in the tank, provided that it is well thermally insulated, will receive excess heat on a clear hot day and release it on a cloudy one. As a result, the actual efficiency of the installation increases by a quarter to a third. And in the end, having competently conjured over local data, in the middle zone of the Russian Federation it is often possible to reduce the required area of ​​​​the EPP by half or more against a certain estimated calculation given above. Accordingly - and the cost of installation.

The vacuum SCs described below are inoperable without a heat accumulator tank. In them, it is either included in the finished construct, or included in the delivery. But with flat SCs, the situation is exactly the opposite and resembles the state of affairs with photographic equipment during the agony of “wet” film photography. Then, for example, for an excellent mirror "Minolta" with a zoom lens, they asked for as much as $190. And the crappiest photo enlarger cost about $600. That is, you took one, you can’t do without the other, so turn your pockets inside out.

In relation to flat SKs, the prices for optional or recommended branded tanks for them look too high, just ugly. Therefore, if you know how to tinker, it is better to do the tank yourself, withstanding only its volume prescribed in the specification for the panel. And do not believe the threats of merchants - a home-made tank can be made no worse than a “company”. How - more on this later, in the section on homemade products.

vacuum

Vacuum SCs are capable of heating the coolant to 80-85 degrees, and their efficiency reaches 74%, and only the cheapest ones are below 50%. This is partly determined by the design of the absorbent panel of rows of pipes; the gaps between them act like a blackbody model, only along one coordinate. But the main role for ensuring high efficiency here is played by the fact that the heat exchanger is located in a vacuum flask or a system of such flasks. The point here is not in thermal insulation (vacuum does not give it at all for radiation), but in the absence of air convection in the chamber. This allows you to distribute the temperature over the surface of the heat exchanger in an optimal way. In a gas-filled chamber, convection currents level it.

On fig. the device of the 2 most common types of vacuum SC is shown. On the left - 1-circuit summer or seasonal. Approximately as shown above in Fig. with types of SK Russian "Dachnitsa". These are filled with water, its outlet temperature is under 60 degrees. Here the role of vacuum is especially clearly visible: if air flows into the flask, its convection will equalize the temperature of the inner tube and there will be no “thermosyphon” in it.

The shell of the flask is made of glasses of different types, see above. The inner tube is an energy receiver (PE) and a heat exchanger. A lot of controversy, up to mutual insults and slander on the forums, gives rise to the question: what is better to blacken - the inner tube from the outside or the inner surface of the shell? From the point of view of the highest efficiency - PE. In this case, the IC losses are minimal, because the shell is made of highly reflective IR glass. This is how the devices for measuring insolation are arranged - actinometers, only there instead of sphere tubes.

Therefore, it is better to take an inexpensive non-pressure vacuum SC for places with low insolation and radiance with PE blackening, however, in the southern regions with an average annual insolation of more than 4 kWh / day with a radiance value of more than 2000 hours / year, it can boil at the height of summer, and this is almost always means depressurization and complete failure. Here, a system with blackening of the shell from the inside will be more reliable.

Also, with blackening of the shell from the inside, pressure SCs are performed (inset at the top left in the figure). In this case, at the cost of some leakage of IC through the shell, its high concentration along the axis of the flask is achieved, which is necessary for good and fast heating of a strong water flow. Additionally, in the most efficient 1-circuit pressure SCs, the central (supply) pipe is also blackened, but it heats mainly the upward flow around it.

On the right in fig. - 2-circuit SC with a heat pipe and a double flask made of glass of different grades. It is precisely these that feed the CO all year round with a coolant with a temperature of 90 degrees: the concentration of the IR on the heat pipe ensures the evaporation of the coolant of the 1st circuit. Which, by the way, is not water at all. Therefore, 2-circuit SCs are not subject to self-repair. Efficiency costs money, and in this case a lot. Therefore, delving into the price lists, we pay special attention to:

• Does the supplier calculate the installation from measurements on site.
• Whether the harness is included in the package (see below).
• Do firm specialists connect the unit to the existing CO.
• Are the declared parameters guaranteed in this case?
• How long is the warranty.
• Whether and how much scheduled and extraordinary maintenance is provided.

Connection and strapping

Year-round pressure vessels are filled with antifreeze to prevent freezing and rupture in winter. A simplified diagram of their connection is shown on the left in the figure: the controller, according to the ratio of temperatures at the supply, return and in the tank, “unwinds”, as required, the circulation pump.

Pressurized solar heating systems are equipped with an accumulative tank with thermal insulation. In the Russian Federation, most of all, systems are sold that are designed to be connected to an existing CO with a boiler. The water heater for the solar heating system must have an appropriate design, in the center in fig. In addition to an additional coil for connecting the boiler (in the tank at the top), the lower one, powered by the SC, is divided into 2 parts; the upper one is about twice as large as the lower one and winds in a cone, below in the tank. The lower spiral excites the convective flow of water, and the upper one transfers heat into it.

Such a solution is necessary so that the boiler return temperature does not fall below 45 degrees, otherwise acidic condensate may fall in it, which quickly disables the boiler. When the Sun does not shine and the SC cannot help the boiler in any way, a water plug forms in the conical spiral, which does not allow the cold “cushion” to rise up to the boiler coil.

In addition to a special tank, when you turn on the SC in a home CO, you also need a piping for it, on the right in Fig. The old boiler piping (not shown conditionally in the figure) is completely preserved! The boiler “feels” the work of the SC only as a warming of the weather! Actually, the procedure for connecting the solar system to CO is simple: CO supply and return are disconnected from the boiler and connected to the SC tank. And the corresponding pipes of the boiler are connected to the fittings of the upper heat exchanger of the SC tank.

About modular SCs

The systems described above are integral constructs. But there are also modular SCs on sale, recruited from panels until the desired parameters are obtained, for example, the Russian Helioplast, see fig. on right. By connecting panels in parallel or in series, you can get either a larger flow of coolant or a higher temperature. The cost of modular SC is considerable, for example. 1 Helioplast panel costs about $300. However, by switching pipelines with three-way valves, it is possible to transfer the entire system from the “spring-autumn” to “summer” mode and vice versa. Or, for example, "shower / kitchen - pool."

Note: modular SC, as more expensive ones, are designed for operation at any positive temperatures, or - from + (10-15), and in cloudy weather.

Compact

It remains to mention compact SCs. They are used, as a rule, for heating water in pools, so that large man-made structures do not spoil the landscape. Prices relative to technical parameters are outrageous; Mercedes-Benz with its "for an asterisk", here, as they say, is resting. The design is simple and quite repeatable with your own hands, see the section on light concentrators.

Homemade SC

For self-production, most of all, flat country-country summer SCs for hot water supply are available. Seasonal heating systems turn out to be so complicated and time-consuming that it is easier and more profitable to buy a ready-made panel. But in terms of homemade products from improvised materials, craftsmen sometimes create samples that are inferior to the best industrial ones, except in appearance, but literally cost a penny. Let's go in order.

box, glass, insulation

The body of a homemade flat SC is best made from wood, plywood, OSB, etc. Durability and durability will be given to it by double impregnation with a water-polymer emulsion before painting. It is advisable to take the thickness of the bottom from 20 mm (preferably from 40), so that cracks do not form from thermal deformations. A board (120-150)x20 will go to the sidewalls. It is undesirable to make a case below, because IR leakage through the glass will increase. Outside, they are painted as you like, but inside - like a “pie” substrate, see below. Dimensions in the plan are calculated based on the amount of insolation and the required power.

Glass is better to take cheaper and easier, organic. Monolithic polycarbonate 4 mm thick is well suited: its light transmission is acceptable, 0.92, the price is low, and a relatively small refractive index will provide little side reflection. Poor UV transmission is partially offset by low thermal conductivity. In terms of surface wear resistance, polycarbonate is one of the best organic glasses; it is enough for cheap homemade products.

Insulate the body with foam; for summer SC, 20-30 mm is enough. They are insulated in 2 layers of equal thickness with aluminum foil strips, but more on that below. To insulate the box of strength for the sake of it is necessary from the inside. If you have read articles about building insulation, please note: with a temperature difference that a flat SC provides, and at a sufficiently high outside temperature, it is not necessary to talk about dew point wandering.

An indispensable addition to insulation is the sealing of all joints and places of pipeline wiring with silicone. Through the slightest crack with a current of air, so much heat will “whistle out” that if there is any sense from the SC, it’s only “for appearance”. First, the body is sealed (before painting); after installing the heat exchanger - tubes, and the glass is laid on a "sausage" of sealant applied to a quarter selected along the top of the sides. Additionally, they are fixed on top with a frame, brackets, etc.

Pie

The "pie" (see the figure on the right) in this case is a substrate that absorbs IR radiation well and quickly, until the IR quanta have time to "escape", gives off heat to the heat exchanger. The basis of the "pie" is an aluminum plate. Copper is less suitable due to its high heat capacity. Additional foil screens bring back most of the "fugitives"; wood and IR foam are not completely opaque materials.

The second highlight of the "pie" is painting. They paint along with the heat exchanger already installed on the clamps. It is necessary to paint with oil (slow-drying) black paint on the pigment "Soot gas"; it can be purchased at art stores. Paints based on synthetic pigments in IR rays will not be black at all.

After painting, you need to wait until the paint dries to a dry touch, i.e. on it, after light pressing with a finger, its imprint should remain, and the finger itself should not get dirty. Then the colorful coating is punched with a foam swab or a very soft end brush. The latter is better, but requires a certain skill in order not to pierce through the still soft coating. As a result, you get a film that is quite reminiscent of the blackbody model in terms of properties.

Note: a very good option is an old thin-walled stamped heating battery. Then you do not need to look for aluminum. Only it is necessary to paint, as described above, and not leave it as it was, see fig.

heat exchanger

The simplest and most efficient heat exchanger is a spiral one made of a thin-walled propylene hose, see fig. on right. It itself is already similar to the blackbody model. Copper one will be even better, but much more expensive. However, a flat spiral heat exchanger has an unpleasant property: in any position, except for a strictly horizontal one, airing is inevitable over time: when heated, the air dissolved in it is released from the water, and there are more than enough ascending arcs where it can accumulate. However, a flat coil heat exchanger can be used in a homemade SC for a pool with a compact concentrator, see below.

The best heat exchanger is a zigzag copper tube with a gap of 10-12 mm in diameter. Why exactly like this? Because for the fastest heating of water in the tank, the thermal power of the SC chamber must be slightly greater than that which the heat exchanger with water is able to accept even at a given temperature difference; for self-made SK - 15-25 degrees. Otherwise, the outlet water temperature will be too low at first, and it will have to make many turns in the system until the tank is heated.

The second parameter that determined the choice of the tube is the resistance to water flow. With an increase in the lumen of the pipe from 5 to 10 mm, it falls quickly, and then more slowly. The third factor is the minimum allowable radius of its bend, 5 diameters for a thin-walled tube without coating (for split air conditioners). Then the width of the zigzag loops is 100 mm, which is just optimal in terms of heat transfer. And you can use a regular manual pipe bender.

Note: these ratios are valid for the described "pie" on an aluminum substrate. As for stamped heating radiators, everything has been calculated there before us. What gives off heat well, absorbs it well. This is one of the axioms of thermodynamics.

Without knowing these circumstances, you can make typical mistakes, see fig. On the left - a thick pipe with wide loops will not immediately accept all the heat generated by the box. Poor efficiency, slow heating. In the center, on the contrary, the capacity of the chamber for this heat exchanger is insufficient. The efficiency may be acceptable, but the tank will still warm up for a long time. In addition, it is a nightmare job of assembling, identifying and fixing leaks ("All sealed joints leak" - one of Murphy's laws). On the right, everything seems to be OK, including the heat exchanger cover (the radiator of an old refrigerator). But the lumen of the tube is 3-4 mm, this is not enough. The IR that has not “pushed through” to the water has nowhere to go, except in vain outside, and the increased resistance to fluid flow (water is not freon) guarantees low efficiency and slow heating.

Note: The efficiency of the SC described above with careful execution exceeds 20%, which is comparable to industrial designs of this type.

Tank again

It's time to take a close look at the battery tank: without it, there will be little sense from the SC. Let's start with the calculation of the volume - we need to take from the Sun everything that the SC allows and save longer; this is especially important if heating is also enabled from the panel. The small tank will soon warm up and then the SC will “fire” to no avail, because. it cannot be heated to infinity. In a tank that is too large, the water in a day will not have time to heat up to the temperature that the SC is capable of providing, and again we do not use the full thermal potential of this area. Why do we take - for the day? Because we are counting on seasonal use with heating, and by nighttime heating may already be needed. In the summer, in the country - to wash, without waiting for the evening; preferably several people.

Let our places not be completely gloomy, and we get 4 kWh / day. Then, see above, the sun per 1 square. m pours out a power of 286 watts. We take the dimensions of the EPP 1x1.5 m (this is for example, make a large one - it will not be worse), i.e. EPP area - 1.5 sq. m; We will take the efficiency of the SC to be 20%. We get: 286 W x 1.5 x 0.2 = 85.6 W, this is the thermal power of our panel. 1 W = 1 J * s, i.e. every second, the SC delivers 85.6 J into the pipe (supply). And for 12 light hours - 85.6 x 12 x 3600 = 3,697,720 J or 3,697.72 kJ.

How much water can take it in? Depends on temperature difference. Let's take the initial one at 12 degrees (shallow water supply in spring / autumn or a well); final - 45 degrees, i.e. heating will be 33 degrees. The heat capacity of water is 1 kcal / l or 4.1868 kJ / l (1 cal - 4.1868 J). When heated to 33 degrees, 1 liter of water will take 4.1868 x 33 = 138.1644 kJ. The capacity will need only a little more than 26 liters. In summer, with a high standing of the Sun and a long daylight hours - under 50 liters. Or, counting on several clear days in a row and good thermal insulation of the tank - up to 200 liters. Which, in general, happened spontaneously: amateurs do not make tanks larger than from a barrel.

Wait, but do people wash themselves under a solar shower? Heating is still with him, it is clear that at least 4 panels are needed here. And it would not hurt to take into account heat loss, at least 20% of the accumulated overnight. That's right, that's what the technique is for bypassing the limitations of a stubborn theory. By the way: "There is nothing more practical than a good theory" - this is still the same great practitioner Edison. Only technical calculations and calculations turn out to be much more cumbersome, so we give a simple result - diagrams of tanks powered by water supply and with manual filling, see fig.

The idea is that one can wash oneself in the summer already after 1.5-2 hours after turning on the SC. That is, we select the upper heated layer of water; in the case of manual filling - with an intake from a flexible hose on a float. The length of the flexible link must be taken moderate: if it is too short in a full tank, the hose will stand upright, and if it is too long, if the water level is low, it will lie on the tank wall.

The location of the nozzles is designed so that in any use, hot and cold flows mix as little as possible, i.e. We deliberately stratify water according to temperature. The best vessel for a tank is a barrel laid on its side. Then the sludge (sludge) will occupy a small part of its capacity. Insulation - foam from 50 mm. And you need to provide 1 more drain pipe with a shut-off valve at the lowest point of the entire system, at the entrance of the return to the SC. Also, do not forget - the selective return pipe must be raised above the bottom, otherwise the sludge will soon clog the SC, and it is difficult to clean it. Pipes - ordinary plumbing, from 1/2 to 3/4 inches. Flexible link - reinforced PVC hose for irrigation; its float is foam.

Note: the elevation of the return flow above the bottom is taken based on the usual hardness of drinking water in the Russian Federation up to 12 German. degrees. According to sanitary standards, its limit value is 29 German. degrees. Then the elevation of the return must be taken 80-100 mm, and the hot supply pipe should be raised above it by the same 20-30 mm.

About Air Solar SCs

Sometimes it is necessary to heat from the Sun not water, but air. Not required for heating; for example, for drying crops or harvesting. Due to the low heat capacity of air, the design of an air SC should have a number of features. You can learn more about them, and at the same time about the use of SC for air heating (this is very important for seasonal cottages), you can find out from the video:

Video: homemade air-solar heating

Unusual homemade

The amateur master would not be him if he did not strive to do everything in his own way from improvised trash. And, I must say, the results are amazing. It is impossible to review all the original home-made SCs in one publication, let's take 3 for examples, so to speak, of a different sign.

On fig. - air, i.e. easier than water, SC from beer cans. Let's not giggle into a fist or be indignant: “Yes, I won’t drink so much!” Let's see technically. The idea itself is quite sensible: the gaps between the rows of cans bring the ability of the panel to absorb light closer to the blackbody model. But! Materials - aluminum, wood, silicone sealant. Their coefficients of thermal expansion (TEC) are significantly different. Joints - more than 200. An elementary calculation, taking into account the law of large numbers, shows that if by the end of the first season of operation the panel does not leak much, this is a miracle.

But the solar collector from plastic bottles in fig. below looks not so elegant, but it is quite functional. In essence, this is a chain of linear light concentrators, see below. The containers are assembled into "sausages", as in the construction of greenhouses, greenhouses, arbors, etc. light constructions from bottles, but are strung not on a rigid rod, but on a transparent PVC hose. The back side of the "sausages" is pasted over with aluminum foil, at least with a baking sleeve. In this case, the fact that water itself absorbs IR quite well is used. The efficiency of the installation is low, but the cost - judge for yourself. And for the Sun tax is not yet taken.

Another interesting home-made from bottles is the Uzbek Ildar, see fig. below. The principle of operation is the same; in our area it is highly desirable to foil the bottom surface of the bottles. When mounting on the southern slope of the roof, frames, props, roof bulkheads and strengthening of the crossbar (bearing frame) of the roof are not required. There are many joints, but materials similar in TKR are joined, so the reliability is sufficient. The strongest will be the joint in pos. B, when the bottles are put on each other. They repeat "Ildar" a little, but in vain. Apparently, it is embarrassing that the water flow is shown to be the reverse of the thermosiphon. But the thermosyphon pressure is much weaker than the gravitational one from the tank, so the Ildar is quite efficient.

Solar collector from Ildar bottles

Note: in bottled SKs, the length of 1 “sausage” should be taken in the middle latitudes about 3 m, and in parallel to connect more of them, how many bottles there are or how much space allows.

Light Concentrators

A light concentrator is a system of mirrors or lenses that collects light from an illuminated area and redirects it to a specific location. Light concentrators do not make the entire solar installation more compact, as is sometimes said. Plus, more precisely - a minus, is that the light transmission coefficient of the collecting system rarely reaches 0.8; most often - 0.6-0.7, and for homemade products - about 0.5. A solar concentrator, or a solar concentrator, allows you to solve the following tasks:

1. Simplify the design of the radiation receiver, make the most complex part of the solar system more compact and reduce the number of joints requiring sealing in it.
2. Increase the illumination of the radiation receiver and thereby enhance light absorption.
3. Increase the temperature of the coolant, which makes it possible to make better use of the accumulated energy.
4. Simplify the procedure for orienting the radiation receiver to the Sun; in some cases, a single adjustment along the meridian and elevation is possible.

Pp. 1 and 3 allow in industrial installations to achieve a greater overall system efficiency. It is difficult to make such installations at home, because. a system of continuous precise orientation to the Sun is required. But pp. 2 and 4 can help the home craftsman.

Note: any solar concentrator collects only direct rays. If you expect to use your installation in cloudy weather, you can not deal with light concentrators.

The main schemes of solar concentrators are shown in fig. there everywhere 1 is a collecting system, 2 is a light receiver. There are also compact hubs, we will deal with one of them below. In the meantime, schemes c) and e) require continuous tracking of the Sun; scheme c), in addition - the manufacture of a parabolic mirror. You can fit a satellite dish, but you probably know the prices for them. And you need to make electronics that controls a precision 2-coordinate electromechanical drive. The Fresnel lens scheme d) is sometimes used to improve the efficiency of small solar cells, but they degrade much faster, see below.

We will deal with linear concentrators, pp. a) and b), as the most suitable for self-made solar installations. The scheme in the form of a semi-cylindrical mirror a) was generally considered earlier, together with bottles. One can only add that it can be oriented (see below) both along the meridian and perpendicular to it, depending on how you want to direct the flow of water in the receiving pipe. This concentrator accelerates the heating of water, but when oriented along the meridian, it significantly reduces the duration of daylight hours for the receiver, because. at angles of incidence from the side of more than about 45 degrees from the normal, no light is captured at all. Re-reflection in it is always single. The light transmission coefficient in the aluminum foil + PET 0.35 mm system is about 0.7.

A concentrator of oblique-incidence mirrors b) captures light within angles of incidence from the normal of 60 degrees or more. It can be done linear and dot. The apparent reduction in daylight hours in the summer in the southern regions is almost imperceptible with it. However, in the morning and in the evening, the efficiency of the installation drops sharply, because. the light then experiences up to 4-5 reflections. For reference: the reflectance of optically polished aluminum is 0.86; galvanized steel - about 0.6.

Nevertheless, for those who want to do this, we present the profile of the mirrors, see fig. The grid step is selected based on the actual dimensions of the installation. Please note that alignment is needed, albeit one-time, but accurate: on June 22 or in the days closest to it, at astronomical (not belt!) Noon, the wings are reduced / spread and folded so that the caustic (bright band of concentrated light) lies exactly along the receiver pipe . Its diameter is about 100 mm, the material is thin blackened metal.

Of greater interest to the do-it-yourselfer will most likely be one of the types of compact non-orientable concentrators, see next. rice. It does not need to be directed at the Sun at all: installed horizontally, it collects its rays within angles of incidence up to 75 degrees from the normal, which in this case is directed to the zenith. That is, we take the SC described above from a hose twisted into a spiral, supply it with this concentrator, and we get a water heater for the pool.

To bring the rays of the Sun to a point, the concentrator belts need a parabolic profile (inset at the top left in the figure), but we have an extended round receiver, so we can get by with conical ones. What dimensions and ratios must be maintained in this case is clear from Fig. The extreme belt (indicated in red) almost does not increase the efficiency of the device, it is better to do without it. Light transmission is about 0.6, so this concentrator will be useful only on a clear summer day. But that's when you need it.

Batteries

Now let's deal with solar panels (SB). To begin with, a little theory, without this it is impossible to understand what and when is good and bad in them. And how to choose the right SB to buy or do it yourself.

Principle of operation

The SB is based on an elementary semiconductor photoelectric converter (PVC), see fig. on right; if someone sees there "ugly" with school electrostatics, please note: the charges receive energy from an external source - the Sun. The ability of semiconductors to pass an electric current is described by the band theory of conductivity, created in the 30s of the last century by the works of mainly Soviet physicists. The thing is very complex, its understanding requires knowledge of quantum mechanics and a number of other disciplines. Very simplified (forgive the physicist-technologist if he reads it), the principle of operation of the FEP is as follows:

1. In a high-purity silicon crystal, donor and acceptor impurities from metals are introduced, each in its own region, the atoms of which are capable of being integrated into the silicon crystal lattice without disturbing it; this is the so-called. doping. the n-region (cathode) is doped with donors; p-region (anode) - acceptors.
2. Donors create an excess of electrons in their region; acceptors in their own - equal in magnitude positive charges - holes, this is a completely correct physical term. Electrons and holes from dopants are the so-called. minor charge carriers. Holes are not positron antiparticles, they are simply places where an electron is missing. Holes can wander (drift) within the crystal, because acceptors are always stealing electrons from each other.
3. Electrons with holes are attracted to each other, seeking to mutually neutralize (recombine).
4. In a crystal (this is where its quantum properties are played out with might and main) they cannot freely combine in a finite period of time, therefore large space charges of the corresponding sign are formed in the boundary layer; on the whole, the boundary layer is electrically neutral.
5. Solar energy, as it were, ejects electrons from the boundary layer to the cathode and to the negative current collector electrode.
6. Holes cannot follow electrons, because they can only drift within the crystal.
7. Electrons have no choice but to pass through the electrical circuit and give the energy received from the Sun to the consumer, this is the electric photocurrent.
8. Once in the anode region, the electrons receive another “kick” from sunlight quanta, which prevents them from recombining with holes and launches them into the circuit again and again, while the crystal is illuminated.

Another word for the Kulibins

Home-made SBs are most often taken by radio amateurs and electronics engineers. As a rule, they understand the basics of the theory of semiconductors. For them, just in case, we will explain how the FEP differs from a diode similar to it, and why it will not work to squeeze out a significant photocurrent from diode / transistor crystals:

• The degree of doping of the anode and cathode of the solar cell is orders of magnitude, and even many orders of magnitude higher than that of active electronic components.
• The cathode and anode are doped approximately to the same extent, as far as planar-epitaxial technology allows.
• The boundary region is wide (it can only be called a p-n junction in this case with a big stretch), so that there is more “working space” for light quanta, and the space charge in it is very large. In the production of electronic circuit components, they tend to do the opposite in order to increase speed.

The structural features of the solar cell proceed from the fact that it is not a receiver of electricity in the form of an applied voltage, but its generator. From this follow conclusions that are already important for any users:

1. Because there are always more light quanta that have entered the crystal than free electrons there, the extra quanta spend their energy on excitation of the atoms of the crystal, which causes it to deteriorate over time, this is the so-called. degradation or aging of solar cells. Simply put, the SB wears out, like any technique, and sits down over time, like any electric battery.
2. The passage of electric current when connecting the solar cell to the consumer circuit accelerates degradation, because. Forcibly drifting in the crystal electrons, so to speak, hit the atoms and gradually knock them out of their places.
3. The energy reserve in the solar cell is determined by the amount of space charge, sunlight only initiates its redistribution.
4. FEPs and SBs consisting of them are afraid of pollution: gradually penetrating (diffusing) into the crystal, they violate its structure. "Poisonous" impurities are also in the air, and their "lethal" dose for the photoelectric effect is negligible.

Item 3 requires additional explanations. Namely: SB is not capable of delivering extra current. For example, a starter battery (battery) with a capacity of 90 A / h briefly delivers a current of 600 A. Theoretically, much more until it explodes from overheating. But, if the specification on the SB says “Short-circuit current (short circuit) 6A”, then more cannot be squeezed out of it by any means.

Note, just in case: it is impossible to dope silicon to infinity, it will simply turn into a dirty metal (“high” degree of doping is expressed as a decimal fraction with many zeros after the decimal point). And in metals there is no internal photoelectric effect. The Hall effect can be hardly felt, but the photoelectric effect is fundamentally impossible: the conduction band of metals is filled with a degenerate electron gas, it simply does not let the quanta inside, which is why the metals shine. Yes, the zone in this case is not a region of space, but a set of states of particles, described by a system of quantum equations.

Device

One solar cell without load creates a potential difference of 0.5 V. It is determined by the quantum properties of silicon and does not depend on any external conditions. Under load, the voltage of the solar cell drops, because. its internal resistance is great. Quantum mechanics does not cancel Ohm's law. Therefore, the battery voltage is taken with a one and a half margin: if, for example, 12 V SB is drawn from modules at 0.5 V, then they are taken 36 per pole, which will give an XX (idle) voltage of 18 V. For a one and a half voltage overload power supply, all DC consumers are calculated. The short circuit current of one solar cell is from several to hundreds of mA; it depends on the area of ​​the exposed (illuminated) surface of the element.

Modules (elements) from many solar cells connected on a common substrate in series, in parallel, or both; their XX voltage and short circuit current are indicated in the product specification. This is associated with a common misconception that, they say, SBs need to be recruited only from 0.5 V elements, while others are substandard. On the contrary, modules from a conscientious manufacturer for, say, 6V 4W, i.e. at 6 V and 0.67 A, they will be more reliable than self-assembled ones with the same parameters. If only because here the photovoltaic cells are grown on the same plate and their parameters are exactly the same.

In the SB solar battery circuit (see Fig.), the PE modules are connected into pillars E, providing the required voltage; as a rule - 12, 24 or 48 V. The columns are connected in parallel to obtain the required operating current. Because the modules in the pillars are not necessarily made of the same crystal, the internal resistances of the pillars are somewhat different, and the voltage under load also “floats”. Through the pillars a little more powerful (with less internal resistance), a reverse current will flow, and from it the degradation of the solar cell occurs rapidly. Radio amateurs can remember that if the diode is even slightly opened “from the side”, it begins to pass the reverse current as well, the operation of the thyristor is based on this. Therefore, the poles are blocked from the "return" by VD diodes. Most often, Schottky diodes are used, because. the voltage drop across them is small and additional cooling at high currents is not required. But sometimes (see below, about SB homemade products), a diode with a p-n junction may also be needed.

When turning on / off powerful consumers, the so-called. transient processes accompanied by extra currents. Just for a few ms, but a gentle SB is enough to quickly sit down. Therefore, a buffer battery GB is required to power the SB to power powerful devices. Controls the distribution of currents in the SB controller C; this is a controlled current source that regulates and limits the operating current of the SB together with the current of the battery charge. In the simplest case, the battery discharge is free according to the level of consumption. Inverter I converts the DC from the battery into AC 220V 50Hz or whatever is required.

Note: the harness on the right in the diagram (C, I, GB) can serve several or many SBs. Then we get a solar power plant (SES).

Very important circumstances following from the above: first, the battery must be included in the circuit all the time. To build a SB according to the “deaf” UPS scheme, in which the battery gives current only when the network fails, it means dooming the SB to rapid degradation due to extra currents. The battery resource in the "flow" scheme is significantly reduced, but there's nothing you can do about it, except to use expensive batteries with a gel electrolyte. So it is not necessary and once again it is not necessary to design SBs with computer UPSs. Secondly, the operating current must be taken approximately 80% of the short-circuit current. If, for example, according to the calculation, the current of the primary circuit is 12 V at 100 A, then the SB must be designed for 120 A.

Thirdly, in this circuit, with a deep discharge of the battery, a reversible system failure is possible, when everything is in order, but there is no current. Therefore, in real solar power plants, the strapping is supplemented with a battery overdischarge alarm (beeps even more nasty than a UPS without a network) and an automation that turns off the inverter if the owners ignored the signal. In the most expensive solar power plants, the inverter has several outputs, the 220 V wiring has several branches, and the automation turns off consumers in the reverse order of their priority; refrigerator, for example, the last one.

SB without strapping is commonly called a solar panel. Its design (see Fig.) ensures, first of all, the reduction of light degradation, then - the efficient use of light and mechanical strength. The first gives mainly a special glass that cuts off the quanta, which will certainly not give a current; the sensitivity of the solar cell to the rays of different zones of the spectrum is significantly uneven. EVA film also provides some light filtering, but it is more designed to increase efficiency: it reduces light refraction and side reflection, i.e. illuminates the coating. The glass, EVA and the elements underneath are “molded” into a single cake with no air gaps, so this design is not for amateurs. The PET lining is, firstly, a mechanical damper (crystalline silicon is a brittle substance, and the element plates are thin). Secondly, it electrically isolates the modules from the panel case, but provides heat transfer of the elements that heat up during operation, because. PET is a better conductor of heat than other plastics. Diodes have already been mentioned. The whole cake is placed in a strong metal case (it also serves as a heat sink) and carefully sealed.

Note: flexible SBs are also on sale, see fig. on right. They can be cheaper and more efficient than rigid panels of the same power, but remember - these SBs are not designed to convert the output current. Flexible SBs are mainly used to supply low-power DC consumers in various types of mobile or remote unattended facilities.

Purchased SB

To prepare for the purchase or manufacture of a solar or solar power plant, you need to understand the concepts of crest factor, peak and long-term energy consumption. In everyday life, this is easier than in complex power systems. Let's say you have circuit breakers or plugs for 25 A on your meter panel. Then you can take up to 220x25 = 5500 W or 5.5 kW from the network. This is your peak consumption, but if you count the power grid for the peak, then it will come out unreasonably expensive: powerful consumers do not turn on for a long time and all at once.

When calculating electrical networks, electricians take picfator \u003d 5; accordingly, the long-term power consumption will be 0.2 of the peak. In our case - 1.1 kW. However, if the SES is calculated for such a peak, then the battery capacity will turn out to be too large, the battery itself will be expensive, and its resource will be much less than normal. To minimize the cost of SPP, its peak factor should be taken half as much, 2.5. In SES, SB “pulls” a long-term load, and the peaks are taken over by the battery, i.e. in this case, we need a 2.2 kW SB and a battery capable of delivering 5.5 kW for an hour or 1.1 kW for 12 hours (dark hours).

Economy

The price of SB on the market is kept within 50-55 rubles. for 1 W of power for polysilicon batteries (see below) and 80-85 rubles / W for monosilicon. But here additional circumstances intervene:

• The efficiency of monosilicon SBs is more than twice as high as that of polysilicon ones (22-38% versus 9-18%) and they are more durable.
• The power of polysilicon SBs decreases less in cloudy weather, and after the expiration of their service life, they completely degrade more slowly.
• The energy utilization factor (energy efficiency) of a buffer acid battery is 74%, and their other types, except for the terribly expensive lithium ones, are poorly suited for buffering SBs.

Taking into account these factors and the climatic conditions of the Russian Federation, the price of 1 W is leveled off and turns out to be about 130-140 rubles / W. SB for 1.1 kW, thus, will cost somewhere around 140-150 thousand rubles. How long will it last? The service life of the SB is not regulated in any way; manufacturers usually give 5, 10, 15 and 25 years. What, according to the output control, will not last 5 years, goes on sale element by element for self-assembly. Beware, do-it-yourselfers!

The price of the finished SB, of course, grows in accordance with the service life. According to the study of company declarations and calculations, SBs for 15 years turn out to be the most profitable. There is an insidious subtlety here: SBs are produced in Grade A, Grade B, Grade C and Ungrade (substandard) conditions. Accordingly, the SB power by the end of its service life drops by up to 5%, 5-30% and more than 30%. However, if you buy Grade A SB for 5 years, then you can’t expect it to last another 25 until it withers by 30%. Due to the increase in the load on the remaining serviceable solar cells in the cell, the degradation process develops like an avalanche: polys last for another six months or a year, and mono - 2-4 months.

So, let's keep counting. With the right choice of primary DC voltage (see below), in 15 years, 1 replacement of the battery will be needed at a cost of about 70 thousand rubles. Plus piping, wires, tires, switching elements, metal structures or work on the roof, this is about another 150 thousand rubles. About 30 thousand will cost the battery; it is strictly forbidden to put batteries in residential premises. We have:

1. Sat - 150,000 rubles.
2. Battery - 140,000 rubles.
3. Strapping - 150,000 rubles.
4. Rechargeable - 30,000 rubles.

Total 470,000 rubles. A turnkey solar power plant of the same capacity will cost about 1.2-1.5 million rubles. But how justified is one or the other?

At 15 years 15x24x365=131400 hours. During this time we will consume 131,400x1.1=144,540 kW/h. 1 kW / h from its own solar power plant will cost 470,000/144,540 = 3.25 rubles. You know the current rates (from 3.15 to more than 6 rubles). The benefit does not seem to be very good, given that these "half a lemon" need to be taken somewhere else, without getting into debt at current loan rates. Nevertheless, it is already justified to build a solar power plant in such cases:

• In remote hard-to-reach places with unstable power supply. Life is more expensive than any tariffs. At least greenhouse plants and domestic animals that provide food and income.
• In commodity farms that require continuous energy supply, the same greenhouses or, say, poultry houses. It is possible to build on cheap land without infrastructure, and the cost of solar power plants may immediately turn out to be less than the cost of laying a power feeder.
• In large households, systematically sorting out the basic consumption limit.
• In collective use. Example: SPP for 15 kW peak (3 average houses) will cost about 1.5 million rubles. self-building or 2.5 million rubles. Full construction. "Dumped" with neighbors / relatives, we get the same 500,000 rubles. and 5 kW per house, but stable and without any communication with the energy companies.

Who to take?

However, it is too early to run “for batteries”. The situation on the SB market is very complicated: high and disorderly, on the verge of a rush, demand all over the world gives rise to fierce and often unfair competition. The world leader in this segment is China, and thanks not to “Chinese” prices (they are not dumping at all), but to actual quality. But China is a very ambiguous country; There are plenty of Shanghai-Wuhan offshore cellars masquerading as reliable state-owned enterprises. On the other hand, the Western "whales" of the industry, in a panic under the threat of bankruptcy, indulge in all serious, if only to push the goods, not sparing their good name.

In Russia, in terms of choosing a manufacturer, there is a good outlet. The electronics and semiconductor industry of the USSR and the Russian Federation have always been at their best in terms of scientific and technical level; the first Intel CPUs, by the way, were made from Soviet silicon, Silicon Valley was still unfolding then. But along the shaft, Soviet-Russian electronics has never been noticeable in the world; worked mostly for the war. In perestroika, products better than those in the world of that time flashed on sale, but it was too late to compete with the "sharks". For example - see fig. It has been working flawlessly so far, the calculations for the article were made on it. And for its more expensive and less capable peers Casio and Texas Instruments, the keys have worn out and the SB has sat down for a long time.

Currently, there are several enterprises operating in the Russian Federation that have clean rooms, trained personnel, engineering and technical personnel and experience in this field. They keep afloat thanks to the right market tactics: they buy SB components from trusted Chinese suppliers, pass them through their own input control and assemble them into panels according to all the technology rules. The declared parameters of their products can be trusted unconditionally. Unfortunately, after the past perturbations, there are few of these left:

1. Telecom-STV in Zelenograd, TSM trademark.
2. RZMKP, Ryazan, TM RZMP.
3. NPP "Kvant", Moscow, folding portable SB.

Recently, MicroART (TM Invertor) has been making good progress on the SB market, and it seems to be not in vain. But there were and were false starts in this segment, so you still need to take a closer look at Inverter. There is one more circumstance: EVA film. It must be frost-resistant, otherwise it coarsens at sub-zero temperatures, gradually exfoliates and the SB fails. Therefore, when choosing, it is imperative to look at the operating temperature range and the allowable minimum exposure time. Or, in the end - the warranty period in these climatic conditions.

Which ones to take?

That statements like “mono is cool, poly sucks” are more emotional than justified, you probably already understand. The difference between them, by the way, is not so fundamental. Silicon ingots of the highest standard, most uniformly recrystallized, go to large chips. 1st condition - for an average degree of integration, 2nd - for discrete components, and only 3rd - for SB. "Mono" differ from "poly" in that in the former, on the cut of one crystal in a blank (crystallite), several solar cells or 1 large one are grown; in polysilicon SBs, small PVCs each occupy approximately 1 also small crystallite.

However, manufacturers and crooks are trying to pass off completely unusable policies as mono-, replacing the designation with a similar one in meaning, but with the letter “m” at the beginning: multicrystalline, microstructural, etc. Therefore, we remind you: polycrystalline SB modules are blue, most often with noticeable iridescence (color overflows), on the left in Fig. Monocrystalline very dark to completely black; iridescence, if there is, is little noticeable, on the right in the same place. But in general, it is impossible to determine the quality of the module by eye or electrical measurements; laboratory chemical, crystallographic and microstructural analysis is needed. What traders-swindlers use with might and main.

About Primary Voltage

Most often, it is recommended to take a SB for 12 V. Like, you can turn on 12-volt economy bulbs and you don’t need a special controller. Firstly, 24, 36 and 48 V DC equipment is not “special” at all, these are standard values ​​for a number of voltages. Secondly, the share of housekeepers in energy consumption is nothing at all, and they need separate wiring. But that's not the point.

Calculated above - for an average house, you need a buffer battery for 5.5 kW peak. The current from it with an hourly discharge will be 5500/12 \u003d 458, (3) or approximately 460 A. There are banks for batteries with a capacity of up to 210-240 A / h on sale, of which starter batteries for heavy special equipment are recruited. Not to mention the cost, one cannot do without parallelizing the batteries, and no more SB elements like to work in parallel with the batteries and for the same reasons; this is a common property of all DC sources. As a result - a battery for 100-120 thousand rubles. it will last at most 5-6 years, and in 15 years it will need 2-3 replacements.

And now let's take the "primary" DC at 48 V. It would be better if 60-72, DC up to 100 V is safe, only SBs don't do that. In terms of impact on the human body, 50/60 Hz are the most dangerous frequencies, but there is nowhere to go, their values ​​have developed historically. Then we get with an hourly discharge 5500/48 = 114.58 (6) A and the battery capacity is 120 A / h. This is an ordinary car battery, plus you can use durable sealed AGM, GEL, OpzS, if you don’t mind the money for them. And the worst of all (auto-starter) will last at least 8 years, or even all 15. And it will cost half as much as a huge one.

There is one more nuance. Take a look at fig. - a SES diagram with a 48 V primary. At the bottom right is the main machine for 175 A. For 12 V, you need 700 A. Have you seen these on sale? Direct current? How much are? Plus other high-current switching, automation, wires and tires. In general, if we discard trade markups, then a 48 V primary circuit reduces the cost of SES by half or more.

Note: and God forbid you connect SES to the street input! You will have to pay uncles on the counter for your expenses and labors. You need to put a packet after the counter (this is already a subscriber wiring and here you are the complete owner, just don’t forget about TV) and switch back from the Sun to the general network, if you need it. Say, when replacing the battery or a long bad weather.

Sat and homemade

The first thing that an amateur solar power industry needs to know is that rejected modules are sold randomly, which 5 will definitely not last. Even if you organize clean production at home, they are already "poisoned" with a slow-acting poison - harmful impurities. In addition, to make a branded "pie", you need a chamber with a deep vacuum, so you will have to assemble the SB in a ventilated box, which means that the elements are subject to atmospheric influences. Without ohmic heat removal, SB modules degrade literally before our eyes. So it is better not to count on a service life of more than 2-3 years.

However, homemade products can be useful, because. 100 W of their power will cost less than 3000 rubles. Which ones - let's see a little lower, but for now let's dwell on the assembly technology. It is shown in full here:

Video: making a solar battery with your own hands

Little can be added. First, do not take into work an obvious defect sent in bulk, on the left in fig. It is better to buy a constructor, see fig. on right. They are equipped with flux sticks and special conductors, which greatly reduces soldering defects.

Soldering with an ordinary soldering iron with rosin flux (on the right in the figure on the left) is also not necessary. The contact pads of the modules are silver (silicon is not soldered), the silver layer is thin and barely sticks. At home, it probably withstands only 1-fold soldering (in production by automatic machines - 3-fold), moreover, with a soldering iron with a bronze nickel-plated tip. Do not try to tin it, with such a soldering iron they solder dry.

However, SB craftsmen also solder with ordinary soldering irons with all sorts of precautions; how can be seen here:

Video: tinning and soldering contacts

The third point - before assembly, the modules must be calibrated and the poles must be assembled from plates with approximately the same parameters (see video below). It is almost never possible to recruit from substandard modules to 48-volt poles, so home-made SBs are made 12-volt or 6-volt.

Video: element calibration

Now about the cases when making a solar battery yourself makes complete sense. The first is the “rubber band” boat described above. The diagram of its power plant is shown in fig. below. The same is suitable for giving, only instead of a motor you need to turn on the inverter 12VDC / 220VAC 50 Hz at 200-300 watts. For a TV, a small refrigerator and a music center, this is enough. Switch S2 is working, S1 is for repair and emergency and for winter storage.

The thing here is that the voltage drop across a conventional diode increases with increasing current through it. Not by much, but in combination with a limiting resistor Rp (both are designed for a lead-acid battery 12V 60A / h!) The SB current overload lasts no more than 2-3 minutes even with a completely “empty” battery. If such a situation occurs once a day, then the SB will last from 4 years, i.e. more than self-collection from substandard. And the gasoline engine during this time would have eaten fuel for an amount much greater than the cost of installation.

The second case is charging for a mobile phone. For her, it is better to buy a ready-made module for 6V 5W; the diagram for it is in fig:

Switch S1 and bright white LED D3 are test switches. If you want to tinker with solar modules, then we offer videos (see below). In this case, an obvious marriage by the piece will also go to the Security Council, the price is cheap. By the way, it's a good practice to work with solar cells before taking on a large SB, and there will be a useful tool.

Video: mini solar battery for charging your phone - assembly and testing

Installation and alignment

The installation of solar panels and collectors of a stationary design is most often carried out on the roof. There are 2 possible solutions: either disassemble a part of the roof and include the SC/SB body in the power circuit of the roof crossbar (its frame without a roofing pie), and then seal the gap, or install the panel on supports made of metal pins passing through the roof. And the rafters, on which the fasteners fell, are reinforced with crossbars.

The first method, of course, is more difficult and requires rather complex construction work. However, it solves not only the problem of wind resistance of the panel. A very slight heating of the hull from the attic side greatly reduces the likelihood of peeling the EVA film and increases the reliability of the entire installation. Therefore, in places with severe frosts / winds, it is certainly preferable.

As for mobile (mobile) or free-standing ground panels, they are mounted on a three-dimensional frame or stand (support) made of metal, wood, etc. If the panel is on the frame, it needs to be sheathed with something so that the wind blowing from behind does not force the panel demonstrate their aerodynamic qualities, pretty good.

Orient to the maximum average annual (seasonal) insolation (adjust) fixed panels should be as accurate as possible. A chicken pecks grain by grain, and a penny saves a ruble - in this case, these sayings fully affect the payback period of the installation. The azimuth is set exactly along the meridian. If you use a compass for this, you need to take into account the magnetic declination of the place; in GPS or GLONASS devices – enable the appropriate correction. You can also beat off the noon line (this is the meridian), as described in school textbooks on natural history, geography, astronomy, or, say, in manuals for building a sundial.

The tilt of the panel in elevation α depending on its geographic latitude φ is calculated for different cases, adjusted for the tilt of the earth's axis β = 23.26 degrees, due to which the height of the Sun in the middle latitudes varies with the seasons of the year:

• For summer installations α = φ-β; if α=<0, панель укладывается горизонтально.
• For seasonal spring-summer-autumn α = φ
• For year-round α = φ + β

If in the latter case α>90 degrees comes out, you are beyond the Arctic Circle, and you do not need a winter panel. Further, for simplicity and accuracy, the angle α is used to calculate the rise of the northern edge of the panel in units of length as h = Lsinα, where L is the length of the panel from south to north. Let's say a 2 m long panel is installed along the meridian. α came out at 30 degrees. Then the northern edge (sin 30 degrees = 0.5) must be raised 1 m. With sinα = 1 or so, the panel is placed vertically.

Finally

Russia, whatever you say, cannot be called a country ideal for the development of solar energy. But it is not a great honor to take what lies badly. But to reach the goal in spite of everything and when everything is against you is a great success for a long time, if only the goal is worthy and useful. There are many examples in history: Holland, Chile (cultivation of barren lands), Japan - an industrial giant, almost completely devoid of sources of raw materials, in the world as a whole - the development of HF radio waves by radio amateurs (specialists, fully armed with theories of that time, considered them worthless), and in Russia - at least the construction of the Trans-Siberian Railway, which still has no analogues. Here homemade people have a place to roam, and if a “Russian solar miracle” happens, this will certainly be their considerable merit.

A huge amount of free energy from the sun, water and wind, and much more that nature can give, people have been using for a long time. For some, this is a hobby, and someone cannot survive without devices that can extract energy “out of thin air”. For example, in African countries, solar panels have long become a saving companion for people, in arid villages solar-powered irrigation systems are being introduced, “solar” pumps are being installed on wells, etc.

In European countries, the sun does not shine so brightly, but the summer is quite hot, and it is a pity when the free energy of nature is wasted. There are successful developments of solar-powered ovens, but they use solid or prefabricated mirrors. Firstly, this is expensive, and secondly, it makes the structure heavier and therefore not always convenient in operation, for example, when a light weight of the finished concentrator is required.
An interesting model of a homemade parabolic solar concentrator was created by a talented inventor.
It does not require mirrors to make it, so it is very light and will not be a heavy load on a hike.

It takes very few things to create a homemade film-based solar concentrator. All of them are sold in any clothing market.
1. Self-adhesive mirror film. It has a smooth, shiny surface and is therefore an excellent material for the mirror part of a solar oven.
2. Chipboard sheet and hardboard sheet of the same size.
3. Thin hose and sealant.

How to make a solar oven?

First, two rings are cut from a chipboard of the size you need with an electric jigsaw, which must be glued to each other. The photo and video show one ring, but the author indicates that he later added a second ring. According to him, one could have been limited to one, but the space had to be increased to form a sufficient concavity of the parabolic mirror. Otherwise, the focus of the beam will be too far away. Under the size of the ring, a circle is cut out of hardboard to form the back wall of the solar concentrator.
The ring should be glued to the hardboard. Be sure to coat everything well with sealant. The design must be completely sealed.
On the side, carefully so that there are even edges, make a small hole into which tightly insert a thin hose. For tightness, the connection of the hose and the ring can also be treated with a sealant.
Stretch a mirror film over the ring.
Evacuate the air from the installation case and thus form a spherical mirror. Bend the hose and clamp with a clothespin.
Make a convenient stand for the finished hub. The energy of this installation is enough to melt an aluminum can.

Attention! Parabolic solar reflectors can be dangerous and can cause burns and eye damage if not handled carefully!
Watch the process of making a solar stove in the video.

Used material from the site zabatsay.ru. How to make a solar battery -.

Published on 09.08.2013

Alternative energy is of interest to an increasing number of great minds. I'm not an exception. 🙂

It all started with a simple question: “Can a brushless motor be turned into a generator?”
-Can. What for?
- Make a wind generator.

A windmill for generating electricity is not a very convenient solution. Variable wind power, chargers, batteries, inverters, a lot of cheap equipment. In a simplified scheme, the windmill does an excellent job of heating water. For the load is ten, and it is absolutely not picky about the parameters of the electricity supplied to it. You can get rid of complex expensive electronics. But calculations showed significant construction costs to spin a 500 watt generator.
The power carried by the wind is calculated by the formula P=0.6*S*V 3 , where:
P– power, watt
S- Area, m2
V– wind speed, m/s

The wind blowing on 1 m2 at a speed of 2 m/s "carries" the energy of 4.8 watts. If the wind speed increases to 10 m/s, then the power will increase to 600 watts. The best wind turbines have an efficiency of 40-45%. With this in mind, for a generator with a power of 500 watts with a wind of, say, 5 m / s. It will take an area swept by the wind turbine propeller, about 12 sq.m. Which corresponds to a screw with a diameter of almost 4 meters! A lot of money - little sense. Add here the need to obtain a permit (noise limit). By the way, in some countries, the installation of a windmill must be coordinated even with ornithologists.

But then I remembered the Sun! It gives us a lot of energy. I first thought about this after flying over a frozen reservoir. When I saw a mass of ice more than a meter thick and 15 by 50 kilometers in size, I thought: “This is how much ice! How much does it need to be heated to melt!?” And all this will be done by the Sun in a dozen and a half days. In reference books, you can find the energy density that reaches the surface of the earth. The figure of about 1 kilowatt per square meter sounds tempting. But this is at the equator on a clear day. How realistic is it to utilize solar energy for household needs in our latitudes (the central part of Ukraine) using available materials?

What real power, taking into account all losses, can be obtained from this square meter?

To clarify this issue, I made the first parabolic heat concentrator out of cardboard (focus in the bowl of the parabola). I pasted over the pattern from the sectors with ordinary food foil. It is clear that the quality of the surface, and the reflective properties of the foil, are very far from ideal.

But the task was to heat a certain volume of water using “collective farm” methods in order to find out what power could be obtained, taking into account all losses. The pattern can be calculated using the Excel file that I found on the Internet from fans of building parabolic antennas on their own.
Knowing the volume of water, its heat capacity, initial and final temperature, it is possible to calculate the amount of heat spent on its heating. And, knowing the heating time, you can calculate the power. Knowing the dimensions of the concentrator, it is possible to determine what practical power can be obtained from one square meter of the surface on which sunlight falls.

A half of an aluminum can, painted black on the outside, was taken as a volume for water.

A container of water is placed at the focus of a parabolic solar concentrator. The solar concentrator is oriented towards the sun.

Experiment #1

held around 7 am at the end of May. Morning is far from an ideal time, but just in the morning the Sun shines through the window of my “laboratory”.

With a parabola diameter 0.31 m calculations showed that a power of the order of 13.3 watts. Those. least 177 watts / sq.m. It should be noted here that a round open jar is far from the best option for obtaining a good result. Part of the energy is spent on heating the can itself, part is radiated into the environment, including being carried away by air currents. In general, even in such far from ideal conditions, you can at least get something.

Experiment #2

For the second experiment, a parabola with a diameter 0.6 m. Metallized tape purchased at a hardware store was used as its mirror. Its reflective qualities are slightly better than aluminum food foil.

The parabola had a longer focal length (focus outside the bowl of the parabola).

This made it possible to project the rays onto one surface of the heater and obtain a high temperature at the focus. Parabola easily burns through a sheet of paper in a few seconds. The experiment was carried out at about 7 am in early June. Based on the results of the experiment with the same volume of water and the same container, I received the power 28 watts., which corresponds approximately to 102 watts/sq.m. This is less than in the first experiment. This is explained by the fact that the sun's rays from the parabola fell on the round surface of the jar not optimally everywhere. Some of the rays passed by, some fell tangentially. The jar was cooled by the fresh morning breeze on one side while warming up on the other. In the first experiment, due to the fact that the focus was inside the bowl, the jar was heated from all sides.

Experiment #3

Realizing that a decent result can be obtained by making the right heat sink, the following design was made: a tin can inside is painted black and has nozzles for water supply and drainage. Hermetically sealed with transparent double glass. Thermally insulated.

The general scheme is as follows:

Heating occurs as follows: the rays from the solar concentrator ( 1 ) through the glass penetrate into the jar of the heat receiver ( 2 ), where, getting on a black surface, it is heated. Water, in contact with the surface of the jar, absorbs heat. Glass does not transmit infrared (thermal) radiation well, so heat radiation losses are minimized. Since over time the glass warms up with warm water and begins to radiate heat, double glazing was used. Ideal if there is a vacuum between the glasses, but this is a difficult task to achieve at home. On the reverse side of the bank is thermally insulated with foam, which also limits the radiation of thermal energy to the environment.

Heat sink ( 2 ) using tubes ( 4,5 ) is connected to the tank ( 3 ) (in my case, a plastic bottle). The bottom of the tank is 0.3m above the heater. This design provides convection (self-circulation) of water in the system.

Ideally, the expansion tank and pipes should also be thermally insulated. The experiment was carried out at about 7 am in mid-June. The results of the experiment are as follows: Power 96.8 watts, which corresponds approximately 342 watts/sq.m.

Those. system efficiency has improved more than 3 times just by optimizing the design of the heat sink!

When conducting experiments 1,2,3, aiming the parabola at the sun was done manually, "by eye". The parabola and the heating elements were held by hand. Those. the heater was not always in the focus of the parabola, because the person's hands get tired and start looking for a more comfortable position, which is not always correct from a technical point of view.

As you can see, efforts were made on my part to provide disgusting conditions for the experiment. Far from ideal conditions, namely:
– not ideal surface of concentrators
– not ideal reflective properties of concentrator surfaces
– not ideal orientation to the sun
– not ideal position of the heater
– not an ideal time to experiment (morning)

could not prevent getting a completely acceptable result for installation from improvised materials.

Experiment #4

Next, the heating element was fixed motionless relative to the solar concentrator. This made it possible to increase the power to 118 watts, which corresponds approximately 419 watts/sq.m. And this is in the morning! From 7 to 8 am!

There are other methods of heating water using solar collectors. Collectors with vacuum tubes are expensive, and flat ones have large temperature losses in the cold season. The use of solar concentrators can solve these problems, but requires the implementation of a mechanism for orientation to the Sun. Each method has both advantages and disadvantages.

(Canada) has developed a versatile, powerful, efficient and one of the most economical solar parabolic concentrators (CSP - Concentrated Solar Power) with a diameter of 7 meters, both for ordinary homeowners and for industrial use. The company specializes in the production of mechanical devices, optics and electronics, which helped it create a competitive product.

According to the manufacturer's assessment, the SolarBeam 7M solar concentrator is superior to other types of solar devices: flat solar collectors, vacuum collectors, solar concentrators of the "trough" type.

External view of Solarbeam solar concentrator

How it works?

The automatic solar concentrator tracks the movement of the sun in 2 planes and directs the mirror exactly at the sun, allowing the system to collect maximum solar energy from dawn to late sunset. Regardless of the season or place of use, SolarBeam maintains a sun pointing accuracy of up to 0.1 degrees.

The rays incident on the solar concentrator are focused at one point.

Calculations and design of SolarBeam 7M

Stress - testing

3D modeling and software stress testing methods were used to design the system. Tests are performed according to the FEM methodology (Finite Element Analysis) to calculate the stresses and displacements of parts and assemblies under the influence of internal and external loads in order to optimize and verify the design. This precise testing ensures that SolarBeam can operate under extreme wind and climatic conditions. SolarBeam has successfully passed wind load simulations up to 160 km/h (44 m/s).

Stress testing of the connection between the parabolic reflector frame and the column

Solarbeam hub mount photo

Stress Testing a Solar Concentrator Rack

Production level

Often, the high cost of manufacturing parabolic concentrators prevent their mass use in individual construction. The use of stamps and large segments of reflective material have reduced production costs. Solartron has used many of the innovations used in the automotive industry to reduce cost and increase output.

Reliability

SolarBeam has been tested in the harsh conditions of the north, providing high performance and durability. SolarBeam is designed for all weather conditions, including high and low ambient temperatures, snow load, icing and strong winds. The system is designed for 20 or more years of operation with minimal maintenance.

The SolarBeam 7M parabolic mirror can hold up to 475 kg of ice. This is approximately equal to 12.2 mm thick ice cover over the entire area of ​​38.5 m2.
The installation works normally in snowfalls due to the curved design of the mirror sectors and the ability to automatically perform "auto clearing of snow".

Performance (comparison with vacuum and flat collectors)

Q / A = F’(τα)en Kθb(θ) Gb + F’(τα)en Kθd Gd -c6 u G* - c1 (tm-ta) - c2 (tm-ta)2 – c5 dtm/dt

The efficiency for non-concentrating solar collectors was calculated using the following formula:

Efficiency = F Collector Efficiency - (Slope*Delta T)/G Solar Radiation

The performance curve for the SolarBeam concentrator shows an overall high efficiency over the entire temperature range. Flat plate and evacuated solar collectors show lower efficiency when higher temperatures are required.

Comparison graphs of Solartron and flat/vacuum solar collectors

Efficiency (COP) of Solartron as a function of temperature difference dT

It is important to note that the diagram above does not account for heat loss from wind. In addition, the data above indicates the maximum efficiency (at noon) and does not reflect the efficiency during for. The data is given for one of the best flat and vacuum collectors. In addition to high efficiency, SolarBeamTM produces an additional 30% more energy due to the dual axis tracking of the sun. In geographical regions where low temperatures prevail, the efficiency of flat and vacuum collectors is significantly reduced due to the large absorber area. SolarBeamTM has an absorber area of ​​only 0.0625 m2 compared to an energy harvesting area of ​​15.8 m2, resulting in low heat loss.

Please also note that due to the dual axis tracking system, the SolarBeamTM hub will always operate at maximum efficiency. The effective area of ​​the SolarBeam collector is always equal to the actual surface area of ​​the mirror. Flat (fixed) collectors lose potential energy according to the equation below:
PL = 1 - COS i
where PL is the loss in energy in %, of the maximum at displacement in degrees)

Control system

SolarBeam controls use "EZ-SunLock" technology. With this technology, the system can be quickly installed and configured anywhere in the world. The tracking system tracks the sun with an accuracy of 0.1 degrees and uses an astronomical algorithm. The system has the possibility of general dispatching through remote networks.

Abnormal situations in which the "dish" will automatically be parked in a safe position.

• If the coolant pressure in the circuit drops below 7 PSI
• When the wind speed is more than 75km/h
• In the event of a power outage, the UPS (Uninterruptible Power Supply) moves the dish to a safe position. When power is restored, automatic sun tracking continues.

Monitoring

In any case, and especially for industrial applications, it is very important to know the status of your system to ensure reliability. You must be warned before a problem occurs.

SolarBeam has the ability to monitor through the SolarBeam Remote Dashboard. This panel is easy to use and provides important SolarBeam status, diagnostics and energy production information.

Remote configuration and management

SolarBeam can be remotely configured and changed on the fly. The "dish" can be controlled remotely using a mobile browser or PC, simplifying or eliminating on-site control systems.

Alerts

In the event of an alarm or service requirement, the device sends an e-mail message to designated service personnel. All alerts can be customized according to user preferences.

Diagnostics

SolarBeam has remote diagnostic capabilities: system temperatures and pressures, energy production, etc. At a glance, you can see the status of the system.

Reporting and charts

If energy production reports are needed, they can be easily obtained for each "dish". The report can be in the form of a graph or a table.

Mounting

SolarBeam 7M was originally designed for large-scale CSP installations, so installation was made as simple as possible. The design allows quick assembly of the main components and does not require optical alignment, which makes installation and start-up of the system inexpensive.

Installation time

A team of 3 can install one SolarBeam 7M from start to finish in 8 hours.

Accommodation Requirements

SolarBeam 7M is 7 meters wide with 3.5 meters of indentation. When installing multiple SolarBeam 7Ms, each system should be given an area of ​​approximately 10 x 20 meters to ensure maximum solar collection with the least amount of shading.

Assembly

The parabolic hub is designed to be assembled on the ground using a mechanical lift system, allowing for quick and easy installation of trusses, mirror sectors and mounts.

Areas of use

Electricity generation with ORC (Organic Rankine Cycle) installations.

Industrial water desalination plants

Thermal energy for the desalination plant can be supplied by SolarBeam

In any industry where a lot of thermal energy is required for the technological cycle, such as:

• Food (cooking, sterilization, obtaining alcohol, washing)
• Chemical industry
• Plastic (Heating, exhaust, separation, …)
• Textile (bleaching, washing, pressing, steaming)
• Petroleum (sublimation, clarification of petroleum products)
• And much more

Installation location

A suitable location for installation are regions that receive at least 2000 kWh of sunlight per m2 per year (kWh/m2/year). I consider the following regions of the world to be the most promising producers:

• Regions of the former Soviet Union
• Southwestern USA
• Central and South America
• North and South Africa
• Australia
• Mediterranean countries in Europe
• Middle East
• Desert plains of India and Pakistan
• Regions of China

Solarbeam-7M Model Specification

• Peak power - 31.5 kW (at a power of 1000 W / m2)
• The degree of energy concentration - more than 1200 times (spot 18cm)
• Maximum focus temperature - 800°С
• Maximum coolant temperature - 270°С
• Operational efficiency - 82%
• Reflector diameter - 7m
• The area of ​​the parabolic mirror - 38.5m2
• Focal length - 3.8m
• Power consumption of servomotors - 48W+48W / 24V
• Wind speed during operation - up to 75km/h (20m/s)
• Wind speed (in safe mode) - up to 160 km / h
• Sun tracking in azimuth - 360°
• Sun tracking vertical - 0 - 115°
• Support height - 3.5m
• Reflector weight - 476 kg
• Total weight -1083 kg
• Absorber size - 25.4 x 25.4 cm
• Absorber area -645 cm2
• The volume of the coolant in the absorber - 0.55 liters

Reflector overall dimensions