The total amount of energy from the sun that reaches the surface of the Earth in just a week exceeds the energy stored in oil, uranium, coal and gas throughout the world. You can save solar heat different ways. One such solution is solar concentrators. This special device for collecting solar energy, which performs the function of heating the coolant material. Typically used for space heating and hot water supply needs. It is precisely this property that distinguishes it from solar panels which directly produce electricity.

Device

The main function of a solar concentrator is focusing solar radiation at the emitter receiver, which is located at the focal line or focal point of the solar energy collector.

The design of a solar concentrator requires the presence of the following elements:

• Lenses or reflectors that are used as a concentrator of sunlight.
• The structure of the base on which lenses or reflectors are mounted.
• A heat-receiving element, which is often a solar collector.
• Pipelines that supply and discharge coolant.
• Drive mechanism of the tracking system. This mechanism in most cases includes:
  — Electronic signal conversion unit.
  — Direction sensor to the Sun.
  — An electric motor with a gearbox that rotates the solar concentrator structure in two planes.

Depending on the design, the device may also include a Fresnel lens, a thermometer, a control valve, a heating circuit, circulation pump and a number of other elements.

Operating principle

The principle of operation of solar concentrators lies in focusing the sun's rays on a container containing coolant.

The work of the coolant is to absorb solar energy. Depending on the method used to concentrate solar energy, the following can be used:

• Parabolic concentrators that focus solar radiation onto oil or water pipes
• Heliocentric tower-type installations.
• Special parabolic mirrors.

Solar radiation in certain models concentrators can concentrate:

• At the focal point.
• Along the focal line where the receiver is located.

Everything looks like this:

• Achievement in Hubs high temperatures is provided by reflecting solar radiation from a larger surface onto a smaller surface of the receiver-absorber.
• The coolant fluid that passes through the receiver absorbs heat as much as possible and transfers it to the consumer.

The temperature in the receiver reaches high values, but the concentrators are able to focus only direct solar radiation. As a result, their effectiveness in cloudy or foggy weather is significantly reduced. The highest efficiency indicators are demonstrated in regions with a high degree of insolation, for example, in equatorial or desert areas.

In order to use solar radiation as efficiently as possible, solar concentrators should be oriented in the direction of the sun. For this purpose, concentrators are equipped with a tracker, that is, a special tracking system. It turns the system directly “facing” the sun.

Single-axis tracking systems rotate the system from east to west. In turn, biaxial systems from north to south to orient the system towards the Sun all year round.

On an industrial scale, a parabolic-cylindrical mirror concentrator provides focusing of solar radiation, providing more than a hundredfold concentration. The result is that the liquid heats up to almost 400 degrees. Passing through a series of heat exchangers, the liquid produces steam, which rotates the steam generator turbine. To minimize heat losses, the receiving tube is surrounded by a transparent glass tube that extends along the focal line of the cylinder.

Kinds

According to the design scheme of operation, concentrators are divided into the following types:

• Parabolic solar concentrators.

• Parabolic cylindrical concentrators.

• Solar towers.

• Concentrators on spherical lenses.

• Concentrators on Fresnel lenses, that is, flat lenses.

Solar concentrators are also classified into the following types:

• Strongly concentrating (Ks≥100) and weakly concentrating (Ks<100). Это зависит от уровня повышения плотности излучения, либо степени его концентрации.
• Selective and non-selective systems, that is, according to the degree of influence of concentrated radiation on the spectral characteristics.
• Refractive (lens) and reflective (mirror) systems - according to the nature of the interaction of solar rays with
  optical elements of solar concentrators.
• Without tracking, equatorial, azimuth-zenithal system - according to the sun tracking scheme.
• Single- and multi-element systems - according to the number of optical elements that sequentially participate in the process of concentrating radiation.
• With a tracking receiver, with a tracking reflector - using the sun tracking method.
• liquid or air-convective heat removal - according to the heat removal method.

Peculiarities

• The radiation of the sun in some concentrators is focused at a focal point, in others - along the focal line, where the receiver is located. When radiation is reflected from a larger surface to a smaller one, a high temperature of the receiver is achieved, this heat is removed by the coolant.
• The efficiency of concentrators is significantly reduced during cloudy periods, since only direct solar radiation is focused. In this regard, such systems have high efficiency in regions where the level of insolation is especially high: in the equator region and deserts. To increase the efficiency of solar radiation use, concentrators are often equipped with tracking systems that provide precise orientation to the sun.
• Since the cost of solar concentrators is quite high, and tracking systems require periodic maintenance, in most cases their use is limited to industrial electrical generation systems. In addition, such installations can be used in hybrid systems, for example, in combination with hydrocarbon fuel. In this case, the storage system will reduce the cost of supplied electricity.

Application

• Parabolic solar concentrators and towers operate optimally in the structure of large systems connected to a network of power plants with a capacity of 30-200 MW.
• Dishes-type systems are made of modules; they can be used in stand-alone installations and groups with a total power of several megawatts.

Parabolic cylindrical solar concentrators are currently one of the most developed solar energy technologies. Most likely, they will be used in industry in the near future. Thanks to their efficient thermal storage capacity, tower-type stations can also become stations of the near future. Due to the modular nature of the trays, they can be used in small installations.

"Tables" and towers make it possible to provide higher efficiency values ​​while obtaining energy at a lower cost. However, this requires a significant reduction in capital costs. Currently, only parabolic concentrators have already been tested and will soon be improved. Tower solar concentrators require demonstration of operational reliability and efficiency. Disc-type systems require the development of an inexpensive concentrator and the creation of a commercial engine.

Parabolic concentrators

Advantages: proven technology.

Flaws:

• High costs.
• Low coolant temperature.
• We need an ultra-flat landscape.

Towers

Advantages:

• Higher efficiency.
• Higher temperature.
• Lower energy costs.
• No need for ultra-flat terrain.

Flaws:

• High price.
• Low prevalence.

Solar concentrators with linear Fresnel reflectors

Advantages:

• Low energy cost.
• Simple design.

Interest in alternative energy is steadily growing. There are many reasons for this, and quite objective ones. The most powerful and stable source of environmentally friendly 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 people with their own hands. A house with solar panels and heat generators—solar collectors—providing electricity on the roof is not uncommon these days in places with a fairly harsh climate, see fig. Moreover, the advantage of solar radiation, such as complete independence from the technogenic environment and natural disasters, cannot yet be replaced with anything.

It’s not without reason that the picture used for illustration is “winter”: modern models of solar collectors are capable of supplying the heating system with a coolant with a temperature of +85 degrees Celsius on a cloudy day with a frost of -20 outside. Such solar installations are quite affordable in price, but require a developed production base for manufacturing. If the task is to provide hot water supply at a dacha or in a country house during the warm season, when the 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 an average-level home craftsman, you can install an installation that will help the heating boiler save a considerable amount of fuel even in winter, and the owners will save money on it. Other applications for homemade solar collectors are also possible; at least - heating the water in the pool. The prices of branded samples of this type are clearly absurd in comparison with their capabilities, and there is nothing there that you cannot do yourself.

With autonomous solar power supply the matter is more complicated. Let's face it: public solar power plants that are superior in all respects 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 to space and its full spectrum is used for this, it is hardly possible. In Eurasia, the northernmost points where the payback period for large solar power plants turns out to be at least slightly less than their service life are the islands of the Aegean Sea and Turkmenistan.

However, an individual purchased solar power plant can be profitable in mid-high latitudes, subject to careful technical and economic calculations and selection of a suitable model; The stability of power supply in a given area plays a significant role in this. And the concept of a do-it-yourself solar battery can have a very 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 can you purchase or make these useful devices yourself, so that you don’t regret wasting money later? This is what this article is devoted to. With a small addition about solar concentrators, or solar concentrators. These devices collect the sun's radiation into a dense beam before transmitting it for conversion. In some cases, it is impossible to achieve the required technical performance of an installation in any other way.

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

1. Significant features of the use of solar energy.
2. Solar collectors (SC), purchased and homemade.
3. Solar concentrators.
4. Solar panels (SB), in the same order.
5. Correct installation and adjustment of the SK and SB.
6. Conclusion in conclusion.

A word to the Kulibins

Hobbyists make solar batteries from a variety of available materials: semiconductor diodes, transistors, disassembled antediluvian selenium and cuprox rectifiers, independently oxidized copper plates 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 section. about SB.

However, it would be completely stupid to blame lovers of technical experiments. Thomas Alva Edison once said, “Everyone knows it can’t be done. There is an ignoramus who does not know this. He is the one who makes the invention.” In any case, touching the subtleties of high technology and the depths of matter (and SB is a visible example of both) gives knowledge and the ability to apply them, i.e. intelligence. And they are capital that never depreciates and whose profitability is higher than any securities.

Nevertheless, even the most general theoretical foundations of all further material are such that the “little bit on the fingers” does not result in articles - in books. Therefore, we will further limit ourselves to those samples for various occasions that you can make yourself at home, without completely forgetting what you were taught at school (by the way, there are quite a few of them); this is the first thing. Secondly, we will limit ourselves to devices that actually produce heat or current, suitable for domestic and economic needs. You will then have to take some of the author’s statements on faith, or turn to fundamental sources.

What can you expect?

Here is an example of a telephone conversation with a sales manager of a company selling solar power: “Under what conditions does your battery develop the declared power?” - “At any!” - “And in Murmansk (beyond the Arctic Circle) in winter too?” - silence, lights out.

Now let's look at the top map in Fig. below. There is a zoning of the Russian Federation based on insolation specifically for the needs of solar energy. Not for farmers, plants over billions of years of life evolution 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. m per day. In mid-latitudes, from the spring to autumn equinox and taking into account the change in the altitude of the Sun during the day and by season, the duration of daylight hours will be something around 14 hours. More precisely, for a specific geographical location, you can calculate it using online calculators, there are some.

Then the flow of solar energy reaches a circle of 4/14 = 0.286 kW/sq. m or 286 W/sq. m. With a solar installation efficiency of 25% (and this is a good indicator), it will be possible to extract 71.5 W of power, thermal or electrical, from a square. If the medium-long-term power consumption (see below) requires 2 kW (this is a typical case), then the converter panel needs an area of ​​2000/71.5 = 27.97 or 28 sq. m; this is 7x4 m. Efficiency 25% - isn't it underestimated? Yes, you can squeeze more out of the panels. A significant part of the further material is devoted to how exactly.

Note: for reference – the solar constant, i.e. The solar energy flux density in the entire spectrum of radiation from ultra-long radio waves to ultra-hard gamma radiation in space in Earth's orbit is 1365.7 W/sq. m. At the equator at noon on the days of the equinox (Sun at its zenith) - about 1 kW/sq. m. Traders often don’t know this, but keep it in mind.

Okay, but what about the manufacturers’ promises then? The panel is, say, 1x1.5 m, and the power for it is stated to be 1 kW. It seems to be not against physics and astronomy, but it looks clearly unrealistic in the middle latitudes under the fur coat of the atmosphere. They say correctly, they are not lying. Only the power was measured on their test bench under special lamps. If they want to be completely honest with me, let them come and shine them on my panel, and for this they can get electricity anywhere.

The map below the first one is needed to further determine the price category or the choice of design for the proposed installation. SB and, especially, SC, capable of working in cloudy weather, are more complex and more expensive than those that operate only in direct light. There are 365x24 = 8760 hours in a year. Taking into account the fact that in high latitudes in summer the duration of daylight hours is longer, SK or SB may pay for themselves within the estimated service life in Yakutsk or Anadyr, but not in the Moscow region or Ryazan. Those. Keep in mind also that solar energy as a beneficial addition to conventional energy is possible not only in the Sahara or the Mojave Desert.

Subtotal

From this section follows an important conclusion for everything that follows: when looking for a panel to buy or repeat, be interested first of all in the area of ​​the surface that effectively perceives (or absorbs) light, and then calculate everything else from it. Moreover, it may turn out that according to marketing and consumer ideas, the panel that seems to be worse in this particular case will be more profitable than the “cool” one.

Collectors

Principle of operation

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

Note: It is actually incorrect to call UV-transmitting glass mineral glass, because... silicate glass is also mineral. It would be better to keep the previous name “quartz glass”, because... Most of the charge for melting UV-transparent glasses is crushed quartz. There are also tourmaline glasses, but not for everyday use - crystals of precious stones are melted into them.

Sunlight entering the camera will be absorbed by it, and the camera will heat up. To avoid heat loss, we will provide it with thermal insulation. Then the thermal energy will turn into IR, but it will not come out through the lid and will not be able to dissipate. Now the IR has no choice but to heat the heat exchanger with coolant placed inside 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” excess heat through the thermal insulation and thermodynamic equilibrium is established.

What is a black hole

To better understand further, you need to know how the pyramidal, or needle-shaped, blackbody model (BLM) works; since we will not need others, further, if we are talking about the blackbody model, we will omit “pyramidal-needle” everywhere. In RuNet, and on the Internet in general, you can’t really find anything about it, but in laboratory practice and technology such things 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 better, the closer its coating or the configuration of the effectively absorbing surface (EAS) itself is in properties to the blackbody model.

Note: A blackbody is a body that absorbs electromagnetic radiation of any frequency. Wood soot, e.g. – not a blackbody; when photographed through an IR filter, it looks light gray. The pyramidal-needle model of the black body is capable of absorbing any, not only electromagnetic, vibrations. Thus, in acoustics, foam rubber pyramids are used to cover the internal surfaces of sound-measuring chambers.

Purchased insurance companies

If you decide to buy a solar collector, you will have to face a price range per 1 sq. m of absorbing area 2000-80 000 rub. And keep in mind that only the final cost is displayed, and even if the EPP area is written down, it is in small print. Also, when choosing a model, you should definitely ask whether it is equipped with a storage tank and piping elements; see more about them below. Let's try to figure out what explains this 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, there are no problems with payback, as long as the climate allows their use.

Types and purpose

In everyday life, SCs of 3 types of design are most commonly 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 either free-flow, on thermosiphon circulation, or pressure. The former are 1.5-5 times cheaper than pressure analogues, because It is easier to ensure strength and tightness in them. Non-pressure SKs heat the coolant relatively slowly, therefore they are more suitable for hot water supply in the warm season. The harness is simple and inexpensive; sometimes combined with a panel into one construct.

In pressure ones, the coolant is either pumped through a circulation pump (which makes them energy-dependent), or tap water is supplied to the heat exchanger. This, of course, requires a stronger and more reliable structure, plus complex energy-dependent wiring and a controller that controls it. The price rises accordingly. But only pressure SKs are suitable for use in 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 auxiliary devices.

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

The latter, naturally, are more expensive, because... able to work in cold weather in any climate. The former are used mainly for heating in spring and autumn. However, it is directly heated pressure boilers (single-circuit) 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 heating system is enough for the house; single-circuit ones are relatively inexpensive. It is only necessary to provide the appropriate shut-off and distribution valves in the system and turn off and empty the system in the fall before the real cold.

Flat

The diagram of a flat SC is shown in Fig. on right; The principle of operation fully corresponds to that described above. As a rule, these are efficient only in the warm season. The efficiency, depending on the design, is in the range of 8-60%. Water is supplied at temperatures up to 45-50 degrees. Pressure ones are produced extremely rarely; the complexity of the design makes them uncompetitive with vacuum ones. The heat exchanger seals are designed to be filled with water only, because... In summer there is no need for antifreeze. The price (we emphasize - per 1 sq. m of EPP; you need to recalculate it yourself each time according to the specification data) is mainly influenced by the following factors:

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

The glass coating plays the role primarily of an antireflective film in optical devices: it reduces the refraction of light at the interface and light loss due to lateral reflection. In properly installed summer SCs (see at the end, before the conclusion), these losses are small or, in the southern regions, completely unnoticeable. In addition, the coating is abraded by wind-blown dust 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 the coating for models with similar technical data, take the “naked” one, most likely you will not be disappointed.

Glass itself is the most important element, and when choosing, you need to focus primarily on it:

1. Mineral - transmits UV, which greatly enhances the greenhouse effect.
2. Textured (structured) - has a special microrelief on the surface, providing 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 antireflection.
4. Silicate with additives - structured or not, does not transmit UV, does not reflect IR well and gives significant lateral reflection without clearing. 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 certain types of it can provide maximum efficiency values.

Based on this, for permanent use, the choice should be made in favor of mineral structured glass. It allows you to get by with a smaller area of ​​the equipment and often ultimately benefit from the cost of the entire installation. At a weekend dacha, the speed of water heating and the initial cost of the collector are also important, so a water heater with plexiglass is more suitable there. The installation, in addition to being cheap, will be more compact and easier; on weekdays and in 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 so - absorbent coating (blackening) of EPP. The properties of various solar absorber coatings are shown in Fig. on right. The rule is, 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 panels. And in general, when making any calculations of the electrical system, we must remember, as we know, that the greatest savings are achieved by reducing the required area of ​​the panel (panels). At the same time, sellers are also checked: if, say, the specification states selective painting and promises an efficiency of 75%, send them to a lamp test bench, it’s hot as hell. It is clear that the efficiency of the entire installation cannot be higher than its parts.

About the tank

A storage tank for 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 approximately 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 amount 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 it is well insulated, will receive excess heat on a clear, hot day and release it on a cloudy day. As a result, the actual efficiency of the installation increases by a quarter to a third. And in the end, by cleverly working with local data, in the central zone of the Russian Federation it is often possible to reduce the required EPP area by half or more compared to that determined by the estimated calculation given above. Accordingly, so do the installation costs.

The vacuum SCs described below without a heat storage tank are inoperative. In them it is either included in the finished design or included in the delivery kit. 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 Minolta SLR with a zoom lens they asked for as much as $190. And the crappiest photo enlarger cost about $600. That is, if you take one, you can’t do without the other, so turn your pockets out.

In relation to flat tanks, the prices for optional or recommended branded tanks for them look outrageously overpriced. Therefore, if you know how to tinker, it is better to make the tank yourself, maintaining only its volume prescribed in the specification for the panel. And don’t believe the threats of traders - a homemade tank can be made no worse than the “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 absorber panel made of rows of pipes; the gaps between them act like a black body model, only along one coordinate. But the main role to ensure 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 (for radiation, a vacuum does not provide it at all), but in the absence of air convection in the chamber. This allows the temperature to be distributed optimally over the surface of the heat exchanger. In a gas-filled chamber, convection currents level it out.

In Fig. the device of the 2 most common types of vacuum SCs is shown. On the left - 1-circuit summer or seasonal. This is roughly how the one shown in Fig. above works. with types of SC 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 “thermosiphon” in it.

The shell of the flask is made of different types of glass, see above. The inner tube is an energy receiver (PE) and a heat exchanger. A lot of controversy, even mutual insults and slander on 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, IR losses are minimal, because The shell is made of highly reflective IR glass. This is exactly how instruments for measuring insolation - actinometers - are designed, only there are spheres instead of tubes.

It is therefore better to take an inexpensive non-pressure vacuum SC for places with little insolation and aurora with blackened PE, however, in the southern regions with an average annual insolation of more than 4 kWh/day with a radiance value of over 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 a blackened shell from the inside will be more reliable.

Also, with the shell blackened 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 IR through the shell, a high concentration along the axis of the flask is achieved, which is necessary for good and quick heating of a strong flow of water. Additionally, in the most efficient single-circuit pressure pumps, the central (supply) pipe is also blackened, but it heats primarily the upward flow flowing around it.

On the right in Fig. – 2-circuit SC with a heat pipe and a double bulb made of glass of different types. These are the ones that feed CO with coolant all year round at a temperature of 90 degrees: the concentration of 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 of it. Therefore, delving into the price lists, we pay special attention to:

• Does the supplier calculate the installation based on on-site measurements?
• Is the harness included (see below).
• Do company specialists connect the installation to the existing CO?
• Are the declared parameters guaranteed in this case?
• How long does the warranty last?
• Is scheduled and extraordinary maintenance provided and how much does it cost?

Connection and piping

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

Pressure solar heating systems are equipped with a storage tank with thermal insulation. In the Russian Federation, the most widely sold systems are those designed for connection to an existing CO with a boiler. The water heater for a solar heating system must be designed accordingly, centered in Fig. In addition to the additional coil for connecting the boiler (in the tank at the top), the lower one, powered from the SC, is divided into 2 parts; the upper one is approximately twice as large as the lower one and is wound in a cone at the bottom in the tank. The lower spiral excites the convective current 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 form in it, which quickly disables the boiler. When the Sun does not shine and the boiler cannot help the boiler, a water plug forms in the conical spiral, preventing the cold “cushion” from rising up to the boiler coil.

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

About modular SC

The systems described above are integral structures. But there are also modular SCs on sale, assembled from panels until the required parameters are obtained, for example, the Russian “Helioplast”, see fig. on right. By connecting panels in parallel or in series, you can obtain either a higher coolant flow or a higher temperature. The cost of modular SCs is considerable, for example. 1 Helioplast panel costs about $300. However, by switching pipelines with three-way valves, the entire system can be switched from “spring-autumn” to “summer” mode and back. Or, for example, “shower/kitchen – swimming pool”.

Note: Modular SCs, as more expensive ones, are designed for operation at any above-zero temperatures, or - from +(10-15), and in cloudy weather.

Compact

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

Homemade SC

The most available for self-production are flat dacha and country summer SCs for hot water supply. Seasonal heating systems turn out to be so complex and labor-intensive that it is easier and more profitable to buy a ready-made panel. But when it comes to homemade products from scrap materials, craftsmen sometimes create samples that are inferior to the best industrial ones only in appearance, but cost literally pennies. Let's go in order.

Box, glass, insulation

The body of a homemade flat SC is best made from wood, plywood, OSB, etc. Double impregnation with a water-polymer emulsion before painting will give it durability and durability. It is advisable to take the thickness of the bottom from 20 mm (preferably from 40), so that thermal deformations do not cause cracks to form. A (120-150)x20 board will be used for the sidewalls. It is not advisable to make the body lower, because IR leakage through the glass will increase. The outside can be painted as desired, but the inside can be painted as the backing of a “pie”, see below. Dimensions in plan are calculated based on the amount of insolation and the required power.

It is better to take cheaper and lighter glass, organic. Monolithic polycarbonate with a thickness of 4 mm is suitable: its light transmittance is acceptable, 0.92, the price is low, and its relatively low refractive index will provide a small lateral reflection. Poor UV transmission is partially compensated 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.

The body is insulated with polystyrene foam; for summer SC, 20-30 mm is enough. They are insulated in 2 layers of equal thickness with spacers made of aluminum foil, but more on that below. The box needs to be insulated from the inside for the sake of strength. If you have read articles about insulating buildings, keep in mind: with the temperature difference that a flat insulating system provides, and with a sufficiently high temperature outside, there is no need to talk about wandering of the dew point.

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

Pie

The “pie” (see figure on the right) in this case is a substrate that absorbs IR radiation well and quickly, before the IR quanta have time to “escape,” transfers 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 most of the “fugitives” back; wood and foam plastic for IR are not completely opaque materials.

The second highlight of the “pie” is painting. They are painted together with the heat exchanger already installed on the clamps. You need to paint with oil-based (slow-drying) black paint using the “Gas Soot” pigment; it can be purchased at art stores. Paints based on synthetic pigments will not be black at all when exposed to IR rays.

After painting, you need to wait until the paint dries to a dry touch, i.e. After lightly pressing with your finger, your fingerprint should remain on it, and the finger itself should not get dirty. Then the paint coating is pierced with a foam swab or a very soft end brush. The latter is better, but requires some skill so as not to pierce the still soft coating right through. The result will be a film that is quite similar in properties to the blackbody model.

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

Heat exchanger

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

The best heat exchanger is a zigzag one made of a copper tube with a clearance of 10-12 mm in diameter. Why exactly like this? Because in order to quickly heat the water in the tank, the thermal power of the SK chamber must be slightly greater than what the heat exchanger with water can accept even at a given temperature difference; for homemade SC - 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 while the tank heats up.

The second parameter that determined the choice of tube is the resistance to water flow. When the pipe lumen increases from 5 to 10 mm, it drops quickly, and then more slowly. The third factor is the minimum permissible radius of its bending, 5 diameters for a thin-walled tube without coating (for split-system air conditioners). Then the width of the zigzag loops is 100 mm, which is optimal from the point of view of heat transfer. And you can use a regular manual pipe bender.

Note: these relationships are valid for the described “pie” on an aluminum substrate. As for stamped heating radiators, everything has been calculated before us. What gives off heat well also 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 absorb all the heat generated by the box. Poor efficiency, slow heating. In the center, on the contrary, the power of the chamber for this heat exchanger is insufficient. The efficiency may be acceptable, but the tank will still take a long time to heat up. In addition, there is a nightmare job of assembling, identifying and eliminating leaks (“All sealed joints leak” - one of Murphy’s laws). On the right - everything seems to be OK, including the cover of the heat exchanger (radiator of an old refrigerator). But the tube lumen is 3-4 mm, this is not enough. The IR that has not “pushed through” to the water has nowhere to go except out in vain, and the increased resistance to liquid flow (water is not freon) guarantees low efficiency and slow heating.

Note: The efficiency of the SC described above, when carefully executed, exceeds 20%, which is comparable to industrial designs of this type.

Tank again

It's time to take a closer look at the battery tank: without it, the SK will be of little use. Let's start with calculating the volume - we need to take from the Sun in a day everything that the SC allows and store it longer; this is especially important if heating is also supplied from the panel. The small tank will soon warm up and then the SC will “stoker” uselessly, because it cannot warm up indefinitely. In a tank that is too large, the water will not have time to heat up in a day to the temperature that the heating system is capable of providing, and again we do not fully utilize the thermal potential of the given area. Why do we charge per day? Because we are counting on seasonal use with heating, and by nightfall heating may already be needed. In the summer at the dacha - to wash yourself without waiting for the evening; preferably to several people.

Let our places not be completely gloomy, and we get 4 kWh/day. Then, see above, Sun per 1 sq. m pours out a power of 286 W. Let’s take the dimensions of the EPP as 1x1.5 m (this is for example, if you make a larger one, it won’t be worse), i.e. EPP area – 1.5 sq. m; Let's assume the efficiency of the SC is 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 outputs 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 it take in? Depends on the temperature difference. Let's take the initial temperature of 12 degrees (shallow water supply in spring/autumn or a well); the final one is 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 is 4.1868 J). When heated by 33 degrees, 1 liter of water will take 4.1868 x 33 = 138.1644 kJ. The capacity you will need is just a little more than 26 liters. In summer, with a high sun and long daylight hours - under 50 liters. Or, based on several clear days in a row and good thermal insulation of the tank - up to 200 liters. Which, in general, happened spontaneously: amateurs don’t make tanks larger than a barrel.

Wait, but people actually wash themselves under solar showers? Heating is a joke so far, it is clear that at least 4 panels are needed here. And it wouldn’t hurt to take into account heat loss, at least 20% of what was accumulated overnight. That’s right, that’s what technology is all about, to circumvent 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 simply give the result - diagrams of tanks powered by water supply and with manual filling, see fig.

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

The location of the nozzles is designed so that during any use the hot and cold flows mix as little as possible, i.e. We deliberately stratify the 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 plastic from 50 mm. And it is necessary to provide 1 more drain pipe with a shut-off valve at the lowest point of the entire system, at the return entrance to the SC. Also, don’t forget that the return return pipe must be raised above the bottom, otherwise the sludge will soon clog the SK, and it is difficult to clean it. The pipes are regular water pipes, 1/2 to 3/4 inches. Flexible link – PVC reinforced 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 mm. degrees. According to sanitary standards, its limit value is 29 German. degrees. Then the return elevation should be taken to be 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 air rather than water from the Sun. Not necessary for heating; for example, for drying or harvesting crops. Due to the low heat capacity of air, the design of an air compressor must have a number of features. You can learn more about them, and at the same time about the use of air heating for air heating (for a seasonal dacha), from the video:

Video: homemade solar air heating

Unusual homemade products

An amateur master would not be one if he did not strive to make everything his own way from the trash at hand. And, I must say, the results are amazing. It is impossible to review all the original homemade SCs in one publication; let’s take 3 for examples, so to speak, of different signs.

In Fig. – air, i.e. easier than water, SK from beer cans. Let’s not giggle into our fists or become indignant: “But I won’t drink that much!” Let's see technically. The idea itself is quite sensible: the gaps between the rows of cans bring the panel’s ability to absorb light closer to the blackbody model. But! Materials: aluminum, wood, silicone sealant. Their coefficients of thermal expansion (TCE) are significantly different. There are more than 200 joints. 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 heavily, this is a miracle.

But the solar collector made of plastic bottles in Fig. The one below doesn't look quite as elegant, but 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, gazebos, etc. light buildings made from bottles, but they are strung not on a rigid rod, but on a transparent PVC hose. The back side of the “sausages” is covered 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 they don’t charge a tax for the Sun yet.

Another interesting homemade product made from bottles is the Uzbek “Ildar”, see fig. below. The operating principle is the same; In our area, it is highly desirable to foil the bottom surface of the bottles. When installed on the southern slope of the roof, no frames, supports, roof bulkheads or reinforcement of the roof crossbar (supporting frame) are required. There are many joints, but materials similar in TKR are joined, so the reliability is sufficient. The strongest joint will be at pos. B, when the bottles are stuck on top of each other. They repeat “Ildar” a little, but in vain. Apparently, it is confusing that the water flow is shown to be the opposite of the thermosiphon flow. But the thermosiphon pressure is much weaker than the gravitational pressure from the tank, so the Ildar is quite operational.

Solar collector made from “Ildar” bottles

Note: in bottled SCs, the length of 1 “sausage” should be about 3 m in mid-latitudes, and more of them should be connected in parallel, as many bottles as there are or as 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 written. The plus, or rather the minus, is that the light transmittance 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 helioconcentrator, allows you to solve the following problems:

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 in it that require sealing.
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 more fully use the accumulated energy.
4. Simplify the procedure for orienting the radiation receiver to the Sun; in some cases, one-time adjustment along the meridian and elevation angle is possible.

pp. 1 and 3 allow in industrial installations to achieve 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 don’t have to use light concentrators.

The basic diagrams of solar concentrators are shown in Fig; everywhere there is 1 – collecting system, 2 – light receiver. There are also compact concentrators, one of which we will look at below. In the meantime, schemes c) and e) require continuous tracking of the Sun; diagram c), in addition - manufacturing a parabolic mirror. You can adapt a satellite dish, but you probably know the prices for them. And you need to make electronics that control a precision 2-axis electromechanical drive. A scheme with a Fresnel lens d) is sometimes used to increase the efficiency of small-sized solar cells, but they degrade much faster, see below.

We will deal with linear concentrators, pp. a) and b), as the most suitable for homemade solar power plants. The scheme in the form of a semi-cylindrical mirror a) was generally considered earlier, together with bottles. We can only add that it can be oriented (see below) either along the meridian or perpendicular to it, depending on how you want to direct the flow of water in the receiving pipe. This concentrator speeds up 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 more than about 45 degrees from the normal, no light is captured at all. Re-reflection in it is always one-time. The light transmission coefficient in the aluminum foil + PET 0.35 mm system is about 0.7.

A concentrator made of oblique incidence mirrors b) captures light within angles of incidence from the normal of 60 degrees or more. Can be done linear or pointwise. The visible reduction in daylight hours in summer in the southern regions is almost imperceptible. However, in the morning and evening the efficiency of the installation drops significantly, 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 pitch is selected based on the actual dimensions of the installation. Please note that the adjustment is needed, albeit once, but accurately: on June 22 or on the days closest to it, at astronomical (not zone!) noon, the wings are brought together/spread and bent so that the caustic (a bright strip of concentrated light) lies exactly along the receiver pipe . Its diameter is about 100 mm, the material is thin blackened metal.

Most likely, one of the types of compact non-orientable concentrators will be of greater interest to the DIYer, see next. rice. It does not need to be pointed 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 our receiver is an extended round one, so we can get by with conical ones. What dimensions and ratios need to be maintained in this case is clear from Fig. The outer belt (indicated in red) almost does not increase the effectiveness of the device; it is better to do without it. Light transmission is about 0.6, so this concentrator will only be useful on a clear summer day. But that’s exactly when it’s needed.

Batteries

Now let's take a look at 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 make it yourself.

Principle of operation

The SB is based on an elementary semiconductor photoelectric converter (PVC), see Fig. on right; If someone sees some “clunky stuff” with school electrostatics, keep in mind: the charges receive energy from an external source - the Sun. The ability of semiconductors to transmit electric current is described by the band theory of conductivity, created in the 30s of the last century through the works of mainly Soviet physicists. This is a very complex thing; understanding it requires knowledge of quantum mechanics and a number of other disciplines. In a very simplified way (forgive a physicist-technologist if he reads this), the principle of operation of a solar cell is as follows:

1. Donor and acceptor impurities from metals are introduced into a high-purity silicon crystal, each in its own region, the atoms of which are capable of being integrated into the crystal lattice of silicon without disturbing it; this is the so-called doping. n-region (cathode) is doped with donors; p-region (anode) – acceptors.
2. Donors create an excess of electrons in their area; acceptors in their own - equal in magnitude positive charges - holes, this is a completely correct physical term. Electrons and holes from alloying additives are the so-called. minority 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 constantly steal electrons from each other.
3. Electrons with holes are attracted to each other, tending to mutually neutralize (recombine).
4. In a crystal (this is where its quantum properties come into play), 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 seems to eject electrons from the boundary layer into the cathode and onto the negative current collector electrode.
6. Holes cannot follow electrons, because capable of drifting only 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 an electric photocurrent.
8. Once in the anode region, the electrons receive another “kick” from the quanta of sunlight, which prevents them from recombining with holes and launches them into the circuit again and again while the crystal is illuminated.

Another word to the Kulibins

Most often, radio amateurs and electronics engineers undertake home-made SBs. As a rule, they understand the basics of semiconductor theory. For them, just in case, let us explain how a solar cell differs from a similar diode, and why it will not be possible to squeeze a significant photocurrent out of diode/transistor crystals:

• The degree of doping of the anode and cathode of a 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 to approximately the same extent, as far as planar epitaxial technology allows.
• The boundary region is wide (calling it a p-n junction in this case is only a 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, the opposite is true to improve performance.

The features of the PV structure are based on the fact that it is not a receiver of electricity in the form of applied voltage, but a generator. This leads to conclusions that are important for any users:

1. Because There are always more quanta of light trapped in a crystal than there are free electrons there; the extra quanta spend their energy on exciting the atoms of the crystal, which is why it deteriorates over time, this is the so-called. degradation or aging of solar cells. Simply put, the SB wears out, like any equipment, and eventually runs out, like any electric battery.
2. The passage of electric current when connecting a solar cell to a consumer circuit accelerates degradation, because electrons forcibly drifting in the crystal, 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 volume of the space charge; sunlight only initiates its redistribution.
4. FEPs and the SBs consisting of them are afraid of contamination: gradually penetrating (diffusing) into the crystal, they disrupt its structure. There are “toxic” impurities in the air, and their “lethal” dose for the photoelectric effect is negligible.

Item 3 requires additional clarification. Namely: SB is not capable of issuing extracts. For example, a starter battery with a capacity of 90 A/h briefly produces 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 you can’t squeeze more out of it by any means.

Note, just in case: It is impossible to dope silicon indefinitely; it will simply turn into dirty metal (a “high” degree of doping is expressed as a decimal fraction with many zeros after the decimal point). But in metals there is no internal photoelectric effect. The Hall effect can be difficult to detect, but the photoelectric effect is fundamentally impossible: the conduction band of metals is filled with degenerate electron gas, it simply will not let quanta in, which is why metals shine. Yes, the zone in this case is not a region of space, but a set of particle states 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 high. Quantum mechanics does not cancel Ohm's law. Therefore, the battery voltage is taken with a margin of one and a half: if, for example, 12 V SB is drawn from 0.5 V modules, then they are taken 36 per column, which will give an idle (no-load) voltage of 18 V. For 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, parallel, or both are available for sale and assembly; their idle voltage and short-circuit current are indicated in the product specification. Associated with this is a common misconception that, supposedly, SB needs to be assembled only from 0.5 V elements, and others are substandard. On the contrary, modules from a reputable manufacturer are rated at, say, 6V 4W, i.e. at 6 V and 0.67 A, will be more reliable than self-assembled ones with the same parameters. If only because here the solar cells are grown on the same plate and their parameters exactly match.

In the SB solar battery circuit (see figure), the PE modules are connected into E pillars that provide the required voltage; usually 12, 24 or 48 V. The poles 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 slightly different, and the voltage “floats” under load. A reverse current will flow through the slightly more powerful poles (with less internal resistance), and from this the degradation of the solar cell occurs rapidly. Radio amateurs may remember that if the diode is opened even a little “from the side,” it begins to pass reverse current, and the operation of the thyristor is based on this. Therefore, the poles are blocked from the “return” by VD diodes. Schottky diodes are most often used, because The voltage drop across them is small and they do not require additional cooling at high currents. But sometimes (see below, about homemade SBs) you may also need a diode with a p-n junction.

When turning on/off powerful consumers, the so-called. transient processes accompanied by extra currents. Just a few ms, but a gentle SB is enough to quickly sit down. Therefore, a GB buffer battery is required for 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 battery together with the battery charging current. In the simplest case, the battery discharge is free according to the level of consumption. Inverter I converts direct current from the battery into alternating current 220 V 50 Hz or other as 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 (SPP).

Very important circumstances follow from the above: first, the battery must be included in the circuit permanently. To build a power supply system according to the scheme of “deaf” UPS, in which the battery provides current only when the network is lost, means dooming the power supply system to rapid degradation due to extra currents. The battery life in a “flow” circuit is significantly reduced, but nothing can be done about it except using expensive batteries with gel electrolyte. So there is no need and once again no need to design a SB with computer UPS. Secondly, the operating current should be approximately 80% of the short-circuit current. If, for example, according to calculations, the primary circuit current is 12 V at 100 A, then the SB needs to be designed for 120 A.

Third, in this scheme, when the battery is deeply discharged, a reversible system failure is possible, when everything is in order, but there is no current. Therefore, in real SES, the harness is supplemented with a battery overdischarge alarm (it beeps even worse than a UPS without a network) and an automatic system that turns off the inverter if the owners ignore 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, last.

A solar system without strapping is usually called a solar panel. Its design (see figure) ensures first of all the reduction of light degradation, then the efficient use of light and mechanical strength. The first is provided mainly by a special glass that cuts off quanta, which most certainly will not produce current; The sensitivity of photovoltaic cells to rays from different spectral zones is significantly uneven. EVA film also provides some light filtration, but it is more designed to increase efficiency: it reduces light refraction and lateral reflection, i.e. brightens the coating. Glass, EVA and the elements underneath are “molded” into a single pie without air gaps, so this design is not for amateurs. The PET lining is, firstly, a mechanical damper (crystalline silicon is a fragile substance, and the element plates are thin). Secondly, it isolates the modules from the panel body electrically, but ensures heat transfer from elements that heat up during operation, because PET conducts heat better than other plastics. Diodes have already been mentioned. The entire cake is placed in a durable metal case (it also serves as a heat sink) and carefully sealed.

Note: Flexible SBs are also available for sale, see fig. on right. They may be cheaper and more efficient than rigid panels of the same power, but remember - these SBs are not designed to convert the supplied current. Flexible SBs are used mainly to power 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 power system or solar power plant, you need to understand the concepts of peak factor, peak and long-term energy consumption. In everyday life this is easier than in complex energy systems. Let's say you have circuit breakers or 25 A plugs 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 calculate the power grid at the peak, it will be unreasonably expensive: powerful consumers do not turn on for a long time and all at once.

When calculating electrical networks, electricians use peakfator = 5; accordingly, long-term power consumption will be 0.2 of the peak. In our case - 1.1 kW. However, if you calculate the SES for such a peak, then the battery capacity will be too large, the battery itself will be expensive, and its service life will be much less than normal. To minimize the cost of a solar power plant, its peak factor should be taken to be half as much, 2.5. In SES, the solar power system “pulls” the long-term load, and the peaks are taken over by the battery, i.e. In this case, we need a 2.2 kW solar power supply 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 within the range of 50-55 rubles. for 1 W of power for polysilicon batteries (see below) and 80-85 rubles/W for monosilicon batteries. But here additional circumstances intervene:

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

Taking into account these factors and the climatic conditions of the Russian Federation, the price of 1 W levels out and turns out to be about 130-140 rubles/W. A 1.1 kW solar system will thus 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 data, will not last 5 years, is sold element by element for self-assembly. Do-it-yourselfers take note!

The price of a finished SB, of course, increases in accordance with its service life. Based on the study of company declarations and calculations, SBs turn out to be the most profitable for 15 years. There is an insidious subtlety here: SBs are produced in Grade A, Grade B, Grade C and Ungrade standards. Accordingly, the SB power at the end of its service life drops by up to 5%, 5-30% and over 30%. However, if you buy SB Grade A for 5 years, then you cannot expect that it will then last another 25 until it withers by 30%. Due to an increase in the load on the remaining functional solar cells in the element, the degradation process develops like an avalanche: poly lasts for another six months to a year, and mono lasts for 2-4 months.

So, let's count further. With the correct choice of primary constant voltage (see below), in 15 years you will need 1 battery replacement costing about 70 thousand rubles. Plus wiring, wires, tires, switching elements, metal structures or work on the roof, that’s about another 150 thousand rubles. The battery will cost about 30 thousand; It is strictly forbidden to install batteries in residential premises. We have:

1. SB – 150,000 rub.
2. Battery – 140,000 rub.
3. Strapping – 150,000 rubles.
4. Battery – 30,000 rub.

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

In 15 years, 15x24x365=131,400 hours. During this time we will consume 131,400x1.1=144,540 kW/h. 1 kW/h from your own solar power plant will cost 470,000/144,540 = 3.25 rubles. You know the current prices (from 3.15 to more than 6 rubles). The benefit doesn’t seem to be very good, considering that these “half a lemon” need to be taken somewhere else without going into debt at current lending rates. However, building a solar power plant is already justified in the following 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 commercial farms that require continuous energy supply, such as greenhouses or, for example, poultry houses. It is possible to build on cheap land without infrastructure, and the cost of a solar power plant may immediately be lower than the cost of laying a power feeder.
• In large households that systematically exceed the basic consumption limit.
• For collective use. Example: A solar power plant for 15 kW peak (3 average houses) will cost about 1.5 million rubles. self-building or 2.5 million rubles. Full construction. By “sharing” with neighbors/relatives, we will receive the same 500,000 rubles. and 5 kW per house, but stably and without any relations with energy companies.

Who to get it from?

However, it’s too early to run for batteries. The situation in the SB market is very complicated: high and disorderly, on the verge of rush, demand all over the world gives rise to tough and often unfair competition. The world leader in this segment is the PRC, and thanks not to “Chinese” prices (they are not dumping at all), but to real quality. But China is a very controversial country; There are plenty of Shanghai-Wuhan offshore basements masquerading as reliable state-owned enterprises. On the other hand, the Western “whales” of the industry, in a panic under the threat of bankruptcy, are going to great lengths just to secure the goods, not sparing their good name.

In Russia, there is a good outlet when it comes to choosing a manufacturer. The electronics and semiconductor industries 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 at that time. But Soviet-Russian electronics have never been noticeable in the world; They worked mainly “for the war.” During perestroika, products better than those in the world at that time appeared on sale, but it was too late to compete with the “sharks.” For example - see fig. It still works flawlessly, the calculations for the article were done on it. But its more expensive and less capable peers, Casio and Texas Instruments, have worn out their keys and have been dead for a long time.

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

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

Recently, MicroART (TM “Inverter”) has been making good progress in the SB market, and it seems to be for good reason. But there have been false starts in this segment, so we still need to take a closer look at the “Inverter”. There is one more circumstance: EVA film. It must be frost-resistant, otherwise at sub-zero temperatures it becomes rough, gradually peels off and the SB fails. Therefore, when choosing, be sure to look at the range of operating temperatures and the permissible minimum exposure time. Or, ultimately, the warranty period in given climatic conditions.

Which ones to take?

The fact that statements like “mono is cool, poly sucks” are more emotional than substantiated is probably already clear to you. The difference between them, by the way, is not so fundamental. Silicon ingots of the highest quality, most uniformly recrystallized, are used for large chips. 1st condition – for the average degree of integration, 2nd – for discrete components, and only 3rd – for SB. “Mono” differs from “poly” in that in the former, several FEPs or 1 large one are grown on a cut of one crystal in a blank (crystallite); in polysilicon SBs, small PECs each occupy approximately one small crystallite.

However, manufacturers and fraudulent traders are trying to pass off completely unusable mono-polys, replacing the designation with a similar 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 shifts), on the left in Fig. Monocrystalline are very dark, to completely black; If there is iridescence, it is barely noticeable, on the right there. In general, it is impossible to determine the quality of a module by eye or electrical measurements; laboratory chemical, crystallographic and microstructural analysis is needed. This is what rogue traders take full advantage of.

About Primary Voltage

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

It was calculated above - for an average house you need a buffer battery with 5.5 kW peak. The current from it during an hourly discharge will be 5500/12 = 458.(3) or approximately 460 A. Banks for batteries with a capacity of up to 210-240 A/h are widely sold, and starter batteries for heavy special equipment are collected from them. Not to mention the cost, you can’t do without paralleling batteries, and they like to work in parallel with batteries no more than SB elements 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 5-6 years at most, and in 15 years it will need 2-3 replacements.

Now let’s take the “primary” DC at 48 V. It would be better 60-72, direct current up to 100 V is safe, only SBs don’t make such things. In terms of the 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 5500/48 = 114.58(6) A with an hourly discharge and a battery capacity of 120 A/h. This is an ordinary car battery, plus you can use long-lasting sealed AGM, GEL, OpzS, if you don’t mind the money for them. And the worst of all (autostarter) will last at least 8 years, or even 15. And it will cost half as much as a huge one.

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

Note: and God forbid you connect the SES to the street input! You will have to pay your uncles according to the meter for your expenses and efforts. You need to install a packager after the meter (this is already a subscriber wiring and here you are the complete master, just don’t forget about TB) and switch back from the Sun to the general network if you suddenly need it. For example, when replacing a battery or prolonged bad weather.

SB and homemade products

The first thing that an amateur solar energy worker needs to know is that there are rejected modules on sale randomly, which definitely won’t 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 signature “pie”, you need a chamber with a deep vacuum, so you will have to assemble the SB in a ventilated box, which means the elements are subject to atmospheric influences. Without ohmic heat removal, SB modules degrade literally before our eyes. So it’s 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 3,000 rubles. We’ll see which ones exactly below, but for now let’s dwell on the assembly technology. It is shown quite fully here:

Video: making a solar battery with your own hands

There is little to add. First, do not take into account the obvious defects sent in bulk, on the left in Fig. It’s better to buy a construction set, see fig. on right. They are equipped with flux pencils and special conductors, which greatly reduces solder defects.

Soldering with a regular 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 holds on. At home, it will probably withstand only 1-fold soldering (in production, with automatic machines - 3-fold), and with a soldering iron with a bronze nickel-plated tip. Don't try to tin it, you can dry solder it with this soldering iron.

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

Video: tinning and soldering contacts

The third point is that before assembly, the modules need to be calibrated and the pillars must be assembled from plates with approximately the same parameters (see video below). It is almost never possible to install substandard modules on 48-volt poles, so homemade power supply units 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 a dacha, only instead of a motor you need to turn on a 12VDC/220VAC 50 Hz inverter for 200-300 W. This is enough for a TV, a small refrigerator and a music center. 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 as the current through it increases. Not much, but in combination with the limiting resistor Rp (both are designed for a 12V 60A/h lead-acid battery!) the current overload of the SB lasts even with a completely “empty” battery for no more than 2-3 minutes. If such a situation occurs once a day, then the SB will last from 4 years, i.e. more than self-assembly from substandard conditions. And during this time, a gasoline engine would consume fuel in an amount much greater than the cost of installation.

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

Switch S1 and bright white LED D3 are test ones. If you want to tinker with solar modules, we offer videos (see below). In this case, the SB will also be used for obvious defects individually, the price is a pittance. By the way, this is a good practice for working with solar cells before taking on a large solar panel, and it will be a useful device.

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

Installation and adjustment

Installation of solar panels and collectors of a stationary design is most often done on the roof. There are 2 possible solutions here: either disassemble part of the roof and include the SK/SB housing in the power circuit of the roof crossbar (its frame without the 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 rest should be reinforced with cross members.

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

As for movable (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 a frame, it needs to be sheathed with something so that the wind blowing from behind does not cause the panel to demonstrate its aerodynamic qualities, which are quite good.

Fixed panels should be oriented (adjusted) to the maximum average annual (seasonal average) insolation as accurately as possible. A chicken pecks a grain, but a penny saves a ruble - in this case, these sayings are fully reflected in relation to 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 mark 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 by elevation angle 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 altitude of the Sun in mid-latitudes varies according to 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 come out, you are above the Arctic Circle, and you do not need a winter panel. Next, for simplicity and accuracy, the magnitude of the rise of the northern edge of the panel in units of length is calculated from the angle α as h = Lsinα, where L is the length of the panel from south to north. Let's say a panel 2 m long is installed along the meridian. α came out at 30 degrees. Then the northern edge (sin 30 degrees = 0.5) needs to be raised by 1 m. With sinα = 1 or so the panel is placed vertically.

Finally

Whatever you say, Russia cannot be called a country ideal for the development of solar energy. But it’s not a great honor to take something that’s bad. But to achieve your 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 (experts, fully armed with the then theories, considered them worthless), and in Russia - at least the construction of the Trans-Siberian Railway, which still has no analogues. Here do-it-yourselfers have a place to roam, and if a “Russian solar miracle” happens, they will probably have a lot to do with it.

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 containing coolant, which can be, for example, oil or water, which absorb solar energy well. Concentration methods vary: parabolic-cylindrical concentrators, parabolic mirrors, or heliocentric tower-type 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 to a smaller surface (the surface of the receiver), a high temperature is reached, the coolant absorbs heat as it moves through the receiver. The system as a whole also contains an accumulating 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, near the equator. To increase the efficiency of using solar radiation, concentrators are equipped with special trackers and tracking systems that ensure the most accurate orientation of the concentrators in the direction of the sun.

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

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

Parabolic cylindrical solar concentrators They are up to 50 meters long and have the appearance of 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 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 into a line, heats the coolant to almost 400 degrees; it passes through heat exchangers, producing steam, which rotates the generator turbine.

To be fair, it is worth noting that a photocell can also be located in place of the pipe. However, despite the fact that with photocells, the size of the concentrators can be smaller, this is fraught with a decrease in efficiency and the problem of overheating, the solution of which requires the development of a high-quality cooling system.

In the California desert in the 80s, 9 power plants were built on parabolic-cylindrical concentrators with a total capacity of 354 MW. Then the same company (Luz International) also built the hybrid station SEGS I in Deggette, with a capacity of 13.8 MW, which additionally included 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 cylindrical power plants is being carried out in Morocco, Mexico, Algeria and other developing countries with funding from the World Bank.

Experts ultimately conclude that today parabolic-cylindrical power plants are inferior both in profitability and efficiency to tower- and plate-type solar power plants.

- These are parabolic mirrors, similar to satellite dishes, with which the sun's rays are focused onto a receiver located at the focus of each such dish. At the same time, the temperature of the coolant with this heating technology reaches 1000 degrees. The coolant liquid 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 disc solar plant is 29% efficiency achieved when converting thermal energy into electrical energy in a disk 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 utility grid and off-grid. 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 production itself, and high pressure steam is supplied directly to generate electricity.

Of course, solar dish concentrators combined with a Stirling engine are of interest to 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 tower-type solar power plants with a central receiver, solar radiation is focused on the receiver, which is located at the top of the tower. Around the tower there are a large number of heliostat reflectors. Heliostats are equipped with a biaxial sun tracking system, thanks to which they are always rotated so that the rays are stationarily concentrated on the heat sink.

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

The coolant liquid, circulating in the receiver, transfers steam to the heat accumulator. Typically, water vapor works with a temperature of 550 degrees, air and other gaseous substances 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 directly used in some kind of production. The temperature in the receiver varies from 538 to 1482 degrees.

The Solar One tower power plant in Southern California, one of the first plants of its type, initially produced electricity through a water-steam system, producing 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 led to thermal storage tower power plants marking 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 550 degrees, and electricity can now be produced at any time of day and in any weather. The Solar Two tower station 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 constructing industrial-scale tower stations. For example, in order to locate a 100 megawatt tower station, 200 hectares are needed, while a nuclear power plant capable of producing 1000 megawatts of electricity requires only 50 hectares. Parabolic-cylindrical stations (modular type) with low capacities, in turn, are more cost-effective than tower ones.

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

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

Energy sources such as electricity, coal and gas are constantly becoming more expensive.

People have to think more often about using more environmentally friendly systems heating.

Therefore it was developed technical innovation in the field of alternative heat sources. For this purpose, solar collectors began to be used.

Solar collector for heating

The surface of this device has low reflectivity, due to which heat is absorbed. For heating the room this mechanism uses the light of the sun and its infrared radiation.

To heat water and heat your home, the power of a simple solar collector is enough. This depends on the design of the unit. A person can install the equipment himself. You don't need to use expensive tools and materials for this.

Reference. The efficiency of professional devices is 80—85% . Homemade ones are much cheaper, but their efficiency no more than 60-65%.

Design

The structure of the equipment is simple. The device is a rectangular plate consisting of several layers:

• anti-reflective tempered glass cover with frame;
• absorber;
• bottom insulation;
• lateral insulation;
• pipeline;
• glass curtain;
• aluminum weatherproof housing;
• connecting fittings.

The system includes 1-2 collectors, storage capacity and anterior chamber. The design is organized in a closed manner, so the sun's rays only enter it and turn into heat.

Principle of operation

The basis of the operation of the installation is thermosiphon. The coolant inside the equipment circulates independently, which will help eliminate the use of a pump.

Heated water tends upward, thereby pushing aside cold water and transporting it to the heat source.

The collector is tubular radiator, which is mounted in a wood box, one plane of which is made of glass. Steel pipes are used in the manufacture of the unit. Discharge and supply are carried out by pipes used in the installation of water supply systems.

The design works like this:

1. The collector converts solar energy into heat.
2. Liquid enters the storage tank through the supply line.
3. The coolant circulates independently or using an electric pump. The liquid in the installation must meet several requirements: not evaporate at high temperatures, be non-toxic, frost-resistant. Usually they take distilled water mixed with glycol. in a ratio of 6:4.

Solar concentrator

A device for accumulating energy from the sun's rays, has a coolant function. Serves to focus energy on the emitter receiver inside the product.

The following types exist:

• parabolic cylindrical concentrators;
• concentrators on flat lenses ( Fresnel lenses);
• on spherical lenses;
• parabolic concentrators;
• solar towers.

Hubs reflect radiation from a large plane to a small one, which helps to reach high temperatures. The liquid absorbs heat and moves it to the heating object.

Important! The price of the devices is not cheap, and also they require constant qualified maintenance. Such equipment is used in hybrid systems, most often on an industrial scale, and allows increasing collector productivity.

Types of collectors powered by solar energy

Currently, there are several types of solar heating collectors.

Flat, do-it-yourself installation

This device consists of a panel into which an absorber plate is mounted. This type of device is the most common. The cost of the units is affordable and depends on the type of coating, manufacturer, power and heating area. Prices for equipment of this type - from 12 thousand rubles.

Photo 1. Five flat-type solar collectors installed on the roof of a private house. The devices are tilted.

Scope of application

Similar collectors often installed in private homes for heating rooms and supplying the premises with hot water. The devices cope with heating water for a summer shower in the country. It is appropriate to use them in warm and sunny weather.

Attention! Collectors surface cannot be obscured by other buildings, trees and houses. This has a negative impact on performance. The equipment is mounted on the roof or facade of the building, as well as on any suitable surface.

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Flat-plate collector design

Device composition:

• protective glass;
• copper tubes;
• thermal insulation;
• absorbent surface with a high degree of absorption;
• aluminum frame.

A collector with a tubular coil is a classic option. As an alternative in home-made designs, the following is used: polypropylene material, aluminum beverage cans, rubber garden hoses.

The bottom and edges of the system must be thermally insulated. If the absorber comes into contact with the housing, heat loss is possible. The external part of the device is protected by tempered glass with special properties. Antifreeze is used as a coolant.

Operating principle

The liquid is heated and enters a storage tank, from which, cooled, it moves to the collector. The design is presented in two versions: single-circuit and double-circuit. In the first case the liquid goes straight into the tank, in the second— passes through a thin tube through water in a container, warming up the volume of the room. As it moves, it cools and moves back to the collector.

Photo 2. Diagram and principle of operation of a flat-type solar collector. The arrows indicate the parts of the device.

Advantages and disadvantages

Units of this type have the following advantages:

• high performance;
• low cost;
• long-term operation;
• reliability;
• possibility of self-made installation and maintenance.

Flat-plate collectors are suitable for operation in southern regions with warm climates. Their disadvantage is high windage due to the large surface, so strong winds can tear down the structure. Productivity drops in cold winter weather. The unit should ideally be installed on the south side of the site or house.

Vacuum

Device consists of individual tubes united at the top to form a single panel. In fact, each of the tubes is an independent collector. This is an effective modern look, suitable for use even in cold weather. Vacuum devices are more complex compared to flat ones, and therefore cost more.

Photo 3. Vacuum type solar collector. The device consists of many tubes fixed in one structure.

Scope of application

Apply for hot water supply and heating of large spaces. They are most often used in dachas and private households. They are mounted on building facades, pitched or flat roofs, and special supporting structures. They function in cold climates and short daylight hours without compromising efficiency. Due to their high efficiency, they are also used on agricultural lands and industrial enterprises. This type is common in European countries.

Design

The device includes:

• thermal storage (water tank);
• heat exchanger circulation circuit;
• the collector itself;
• sensors;
• receiver.

The design of the unit consists of a series of tubular profiles installed in parallel. The receiver and vacuum tubes are made of copper. The block of glass tubes is separated from the external circuit, so that the operation of the collector does not stop if it fails 1-2 tubes. Polyurethane insulation is used as additional protection.

Reference. A distinctive feature of the collector is the composition of the alloy from which the pipes are made. This Aluminum coated and polyurethane protected copper.

Operating principle

Construction work based on zero thermal conductivity of vacuum. An airless space is formed between the tubes, which reliably retains the heat generated by the sun's rays.

The vacuum manifold works like this:

• the sun's energy is received by a pipe inside a vacuum flask;
• the heated liquid evaporates and rises into the condensation area of ​​the pipe;
• the coolant flows down from the condensation zone;
• the cycle repeats again.

Thanks to this work much higher level of heat transfer, and heat loss is low. Energy can be saved due to the vacuum layer, which effectively traps heat.

Photo 4. Schematic diagram of a vacuum solar collector. The components of the device are indicated by arrows.

Advantages and disadvantages

Advantages of devices of this type:

• durability;
• stability in operation;
• affordable repair, it is possible to replace only one element that has failed, and not the entire structure;
• low windage, ability to withstand gusts of wind;
• maximum absorption of solar energy.

The equipment is expensive and will only be repaid in a few years. after use. The price of components is also high; replacing them may require the help of a professional. The system is not capable of self-cleaning from ice, snow, and frost.

Types of Vacuum Manifolds

Products come in two types: with indirect and direct heat supply. The functioning of structures with indirect supply is carried out from the pressure in the pipes.

In devices with direct heat supply, the coolant container and glass vacuum devices are mounted to the frame at a certain angle, through a rubber connecting ring.

Equipment connects to water supply lines via a shut-off valve, and the fixing valve controls the water level in the tank.

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Air

Water has a much higher heat capacity than air. However, its use is associated with a number of everyday problems during operation (pipe corrosion, pressure control, change in physical state). Air collectors not so whimsical, have a simple design. The devices cannot be considered a complete replacement for other types, but they are able to reduce utility costs.

Scope of application

This type of equipment is used in air heating of houses, drying systems And for air recovery (processing). Used for drying agricultural products.

Design

Comprises:

• an adsorber that absorbs heat from a panel inside the housing;
• external insulation made of tempered glass;
• thermal insulation between the housing wall and the absorber;
• sealed housing.

Photo 5. Air solar collector for heating a house. The device is mounted vertically on the wall of the building.

The device is located close to the heating object due to large heat losses in air lines.

Operating principle

Unlike water collectors, air ones do not accumulate heat, but immediately release it into the insulation. Sunlight hits the outer part of the device and heats it, air begins to circulate in the structure and heats the room.

You can design the air manifold yourself, using available materials in production: beer cans made of copper or aluminum, chipboard panels, aluminum and metal sheets.

Photo 6. Diagram of the airborne solar collector. The drawing shows the main parts of the device.

Advantages and disadvantages

Advantages:

• low cost of the device;
• possibility of self-installation and repair;
• simplicity of design.

Disadvantages: limited scope of application (heating only), low efficiency. At night, the equipment will work to cool the air if it is not closed.

Selecting a set of solar collectors for a heating system

Device selection depends on the purposes for which the work of the design will be directed. The solar system is used to support air, provide hot water supply, and heat water for the pool.

Power

To calculate the possible power of the solar system, You need to know 2 parameters: solar insolation in a certain region at the right time of year and the effective absorption area of ​​the collector. These numbers must be multiplied.

Is it possible to use the collector in winter?

Vacuum devices cope with work in cold climates. Flat show low performance in cold weather and are better suited for southern regions.

Less suitable than others for functioning in cold conditions air structure since at night it is not able to heat the air.

Heavy rainfall causes inconvenience, because in winter the equipment is often covered with snow and regular cleaning is required. Frosty air takes away the accumulated heat, and the collector itself can be damaged by hail.

Taking into account the scope of application

In industry, the use of solar systems is more common. Solar energy is used in the operation of power plants, steam generators, and water desalination plants. To heat water, heat a cottage or a bathhouse in domestic conditions, vacuum collectors are often installed, less often - flat ones. Air systems help reduce heating costs by heating the air during the day.

The main task of a solar collector is to convert energy received from the sun into electricity. The operating principle and design of the equipment are simple, so technically it is easy to make. Typically, the resulting energy is used to heat buildings. Making a solar collector for heating a house with your own hands must begin with the selection of all components.

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Design and operating principle

Heating a home by converting solar energy into electrical energy is usually used as an additional source of heat, rather than the main one. On the other hand, if you install a high-power structure and convert all the appliances in the house to electricity, then you can only get by with a solar collector.

But it is worth remembering that heating using solar collectors without additional heat sources is possible only in the southern regions. In this case, there should be quite a lot of panels. They must be positioned in such a way that shadows do not fall on them (for example, from trees). The panels should be placed with their front side in the direction that receives maximum sun exposure throughout the day.

Solar Energy Concentrators

Although today there are many varieties of such devices, the principle of operation is the same for all. Any circuit takes solar energy and transfers it to the consumer, representing a circuit with a sequential arrangement of devices. The components that produce electricity are solar panels or collectors.

The collector consists of tubes that are connected in series to the inlet and outlet. They can also be arranged in the form of a coil. Inside the tubes there is process water or a mixture of water and antifreeze. Sometimes they are simply filled with air flow. Circulation occurs due to physical phenomena such as evaporation, changes in the state of aggregation, pressure and density.

Absorbers perform the function of collecting solar energy. They look like a solid black metal plate or a structure made up of many plates connected to each other by tubes.

Materials with high light transmittance are used to make the housing cover. Often this is either plexiglass or tempered types of ordinary glass. Polymer materials are sometimes used, but making collectors from plastic is not recommended. This is due to its large expansion from heating by the sun. As a result, depressurization of the housing may occur.

If the system will be operated only in autumn and spring, then water can be used as a coolant. But in winter it must be replaced with a mixture of antifreeze and water. In classical designs, the role of coolant is played by air, which moves through channels. They can be made from ordinary corrugated sheets.

Experience in operating a solar battery made independently (solar battery part 3).

If the collector needs to be installed to heat a small building that is not connected to the autonomous heating system of a private house or centralized networks, then a simple system with one circuit and a heating element at its beginning is suitable. The scheme is simple, but the feasibility of its installation is disputed, since it will only work in sunny summers. However, circulation pumps and additional heaters are not required for its operation.

With two circuits, everything is much more complicated, but the number of days when electricity will be actively generated increases several times. In this case, the collector will process only one circuit. Most of the load is placed on a single device that runs on electricity or another type of fuel.

Although the performance of the device directly depends on the number of sunny days per year, and its price is too high, it is still very popular among the population. No less common is the production of solar heat exchangers with your own hands.



Classification by temperature indicators

Solar systems are classified according to various criteria. But in devices that you can make yourself, you should pay attention to the type of coolant. Such systems can be divided into two types:

• use of various liquids;
• air structures.

The first ones are used most often. They are more productive and allow you to directly connect the collector to the heating system. Classification by temperature is also common, within which the device can operate:



DIY solar battery Part11

The last type of solar system works thanks to a very complex principle of solar energy transfer. The equipment requires a lot of space. If you place it in a country house, then it will occupy the predominant part of the site. To produce energy, you will need special equipment, so making such a solar system yourself will be almost impossible.






DIY making

The process of making a solar heater with your own hands is quite exciting, and the finished design will bring a lot of benefits to the owner. Thanks to this device, you can solve the problem of heating rooms, heating water and other important household tasks.



Materials for self-production

An example is the process of creating a heating device that will supply heated water to the system. The cheapest option for producing a solar collector is to use wooden blocks and plywood, as well as chipboards, as the main materials. As an alternative, you can use aluminum profiles and metal sheets, but they will be more expensive.

All materials must be moisture resistant, that is, meet the requirements for outdoor use. A well-made and installed solar collector can last from 20 to 30 years. In this regard, materials must have the necessary performance characteristics for use throughout their entire service life. If the body is made of wood or chipboards, then to extend its service life it is impregnated with water-polymer emulsions and varnish.

Review: Homemade solar panel (battery).

The necessary materials for manufacturing can either be bought freely on the market, or a structure can be made from scrap materials that can be found in any household. Therefore, the main thing you need to pay attention to is the price of materials and components.

Arrangement of thermal insulation

To reduce heat loss, insulating material is placed at the bottom of the box. You can use polystyrene foam, mineral wool, etc. Modern industry provides a large selection of different insulation materials. For example, using foil is a good option. It will not only prevent heat loss, but will also reflect the sun's rays, which means it will increase the heating of the coolant.

If you use polystyrene foam or polystyrene for insulation, you can cut grooves for the tubes and install them in this way. As a rule, the absorber is fixed to the bottom of the housing and laid over the insulating material.

Collector heat sink

The heat sink of the solar collector is the absorbent element. It is a system consisting of tubes through which the coolant moves and other parts, usually made from copper sheets.

The best material for the tubular part is copper. But home craftsmen have invented a cheaper option - polypropylene hoses, which are twisted into a spiral shape. Fittings are used to connect to the system at the inlet and outlet.

It is allowed to use various materials and means at hand, that is, almost any that are on the farm. A do-it-yourself heat collector can be made from an old refrigerator, polypropylene and polyethylene pipes, steel panel radiators and other available materials. An important factor when choosing a heat exchanger is the thermal conductivity of the material from which it is made.




The ideal option for creating a homemade water collector is copper. It has the highest thermal conductivity. But using copper tubes instead of polypropylene does not mean that the device will produce much more warm water. Under equal conditions, copper tubes will be 15-25% more efficient than installing polypropylene analogues. Therefore, the use of plastic is also advisable, and it is much cheaper than copper.

When using copper or polypropylene, all connections (threaded and welded) must be sealed. Possible arrangement of pipes is parallel or in the form of a coil. The top of the main structure with tubes is covered with glass. When shaped in the form of a coil, the number of connections is reduced and, accordingly, the possible formation of leaks, and also ensures uniform movement of the coolant through the tubes.

You can use more than just glass to cover the box. For these purposes, translucent, matte or corrugated materials are used. You can use modern acrylic analogues or monolithic polycarbonates.

When making the classic version, you can use tempered glass or plexiglass, polycarbonate materials, etc. A good alternative would be to use polyethylene.

It is important to consider that the use of analogues (corrugated and matte surfaces) helps to reduce the light transmission capacity. In factory models, special solar glass is used for this. It has a little iron in its composition, which ensures low heat loss.

Installation storage tank

To create a storage tank, you can use any container with a volume from 20 to 40 liters. A scheme with several tanks that are connected to each other into one system is also used. It is advisable to insulate the tank, otherwise the heated water will quickly cool down.

If you look at it, there is no accumulation in this system, and the heated coolant must be used immediately. Therefore, the storage tank is used for:

• maintaining pressure in the system;
• replacing the front camera;
• distribution of heated water.

Of course, a solar collector made by yourself at home will not provide the quality and efficiency characteristic of factory-made models. Using only available materials, there is no need to talk about a high efficiency. In industrial samples, such indicators are several times higher. However, the financial costs will be much lower here, since improvised means are used. A self-made solar installation will significantly increase the level of comfort in a country house, as well as reduce costs for other energy resources.