Solar panels are better on the principle of a parabola. Solar energy concentrators. Video: making a solar battery with your own hands

Published on 09.08.2013

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

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

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

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

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

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

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

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

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

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

Experiment #1

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

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

Experiment #2

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

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

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

Experiment #3

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

The general scheme is as follows:

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

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

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

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

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

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

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

Experiment #4

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

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

The problem of using solar energy has occupied the best minds of mankind since ancient times. It was clear that the Sun is the most powerful source of free energy, but no one understood how to use this energy. If you believe the ancient writers Plutarch and Polybius, then the first person to practically use solar energy was Archimedes, who, using some optical devices he invented, managed to collect the sun's rays into a powerful beam and burn the Roman fleet.

In essence, the device invented by the great Greek was the first concentrator of solar radiation, which collected the sun's rays into one energy beam. And at the focus of this concentrator, the temperature could reach 300 ° C - 400 ° C, which is quite enough to ignite the wooden ships of the Roman fleet. One can only guess what kind of device Archimedes invented, although, according to modern ideas, he had only two options.

The very name of the device - a solar concentrator - speaks for itself. This device receives the sun's rays and collects them into a single energy beam. The simplest concentrator is familiar to everyone from childhood. This is an ordinary biconvex lens, which could burn various figures, inscriptions, even entire pictures, when the sun's rays were collected by such a lens into a small dot on wooden board, sheet of paper.

This lens belongs to the so-called refractor concentrators. In addition to convex lenses, Fresnel lenses and prisms also belong to this class of concentrators. Long-focus concentrators based on linear Fresnel lenses, despite their low cost, are practically used very little, since they have large sizes. Their use is justified where the dimensions of the concentrator are not critical.

Refractory solar concentrator

The prismatic concentrator of solar radiation is deprived of this shortcoming. Moreover, such a device is also capable of concentrating part of the diffuse radiation, which significantly increases the power of the light beam. The trihedral prism, on the basis of which such a concentrator is built, is both a radiation receiver and a source of an energy beam. In this case, the front face of the prism receives radiation, the back face reflects, and radiation is already emerging from the side face. The operation of such a device is based on the principle of total internal reflection of rays before they hit the side face of the prism.

Unlike refractor concentrators, reflex concentrators work on the principle of collecting reflected sunlight into an energy beam. According to their design, they are divided into flat, parabolic and parabolic-cylindrical concentrators. If we talk about the effectiveness of each of these types, then the highest degree of concentration - up to 10,000 - is given by parabolic concentrators. But for the construction of solar heating systems, mainly flat or parabolic-cylindrical systems are used.

Parabolic (reflector) solar concentrators

Practical application of solar concentrators

Actually, the main task of any solar concentrator is to collect the radiation of the sun into a single energy beam. And you can use this energy in various ways. It is possible to heat water with free energy, and the amount of heated water will be determined by the size and design of the concentrator. Small parabolic devices can be used as a solar cooker.

Parabolic concentrator as a solar oven

You can use them for additional lighting of solar panels to increase the power output. And it can be used as an external heat source for Stirling engines. The parabolic concentrator provides a focus temperature of about 300°C - 400°C. If the focus of such a relatively small mirror put, for example, a stand for a kettle, a frying pan, you get a solar oven, on which you can cook food very quickly, boil water. A heater with a heat carrier placed at the focus will allow you to quickly heat up even running water, which can then be used for household purposes, for example, for showering, washing dishes.

The simplest scheme for heating water with a solar concentrator

If a Stirling engine of suitable power is placed at the focus of a parabolic mirror, then a small thermal power plant can be obtained. For example, Qnergy has developed and launched the QB-3500 Stirling engines, which are designed to work with solar concentrators. In fact, it would be more correct to call them generators electric current based on Stirling engines. This unit generates an electric current with a power of 3500 watts. The output of the inverter is a standard voltage of 220 volts 50 hertz. This is quite enough to provide electricity to a house for a family of 4, a dacha.

By the way, using the principle of operation of Stirling engines, many craftsmen make devices with their own hands that use rotational or reciprocating motion. For example, water pumps for summer cottages.

The main disadvantage of a parabolic concentrator is that it must be constantly oriented towards the sun. In industrial helium installations, special tracking systems are used that rotate mirrors or refractors following the movement of the sun, thereby ensuring the reception and concentration of the maximum amount of solar energy. For individual use it would hardly be expedient to use such tracking devices, since their cost can significantly exceed the cost of a simple reflector on a conventional tripod.

How to make your own solar concentrator

The easiest way to make a homemade solar concentrator is to use old plate from a satellite dish. First you need to decide for what purposes this hub will be used, and then, based on this, choose the installation site and prepare the base and fasteners accordingly. Thoroughly wash the antenna, dry it, stick a mirror film on the receiving side of the dish.

In order for the film to lie flat, without wrinkles and folds, it should be cut into strips no more than 3-5 centimeters wide. If you intend to use the concentrator as a solar oven, it is recommended to cut a hole in the center of the plate with a diameter of about 5 - 7 centimeters. Through this hole, a bracket with a support for dishes (burner) will be passed. This will ensure the immobility of the container with the cooked food when the reflector is turned to the sun.

If the plate is small in diameter, it is also recommended to cut the strips into pieces about 10 cm long. Stick each piece separately, carefully adjusting the joints. When the reflector is ready, it should be installed on the support. After that, it will be necessary to determine the focus point, since the optical focus point at the satellite dish does not always coincide with the position of the receiving head.

Homemade solar concentrator - oven

To determine the focal point, you need to arm yourself with dark glasses, a wooden plank and thick gloves. Then you need to direct the mirror directly at the sun, catch a sunbeam on the board and, bringing the board closer or further away from the mirror, find the point where this sunbeam will have the minimum size - a small point. Gloves are needed in order to protect hands from burns if they accidentally fall into the beam area. Well, when the focus point is found, it remains only to fix it and mount the necessary equipment.

Options self-manufacturing there are many solar concentrators. In the same way, you can make a Stirling engine from improvised materials yourself. And you can use this engine for a variety of purposes. How much imagination, desire and patience is enough.

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

People need to think more about using greener systems heating.

Therefore, it was developed technical innovation in the field of alternative heat sources. Solar collectors have been used for this.

Solar collector for heating

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

To heat the water and heat the house, the power of a simple solar collector is enough. It depends on the design of the unit. A person can independently make the installation of equipment. For this, you do not need to use expensive tools and materials.

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:

• framed anti-reflective tempered glass cover;
• absorber;
• bottom insulation;
• side insulation;
• pipeline;
• glass curtain;
• aluminum weatherproof case;
• connecting fittings.

The system includes 1-2 collectors, storage capacity and avankameru. The design is organized closed, so the sun's rays fall only into it and turn into heat.

Principle of operation

The basis of the operation of the installation is a thermosyphon. The coolant inside the equipment circulates on its own, which will help to abandon the use of the pump.

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

The collector is tubular radiator, which is mounted in a wooden box, one plane of which is made of glass. Pipes in the manufacture of the unit are used steel. The diversion and supply are carried out by pipes used in the plumbing device.

The structure works like this:

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

solar concentrator

solar energy storage device has the function of a heat carrier. Serves to focus energy on the emitter receiver inside the product.

There are the following types:

• parabolic-cylindrical concentrators;
• concentrators on flat lenses ( fresnel lens);
• 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 to the heating object.

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

Types of solar collectors

Currently, there are several varieties of solar heating collectors.

Flat, do-it-yourself installation

This device consists of a panel in which the 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 appliances are tilted.

Scope of application

Similar collectors often installed in private homes for room heating and supply hot water. Devices manage to heat water for a summer shower in the country. It is appropriate to operate them in warm and sunny weather.

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

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flat collector design

The composition of the device:

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

The collector, which has a tubular coil, is a classic option. As an alternative to makeshift designs apply: polypropylene material, aluminum beverage cans, rubber garden hoses.

The bottom and edges of the system must be thermally insulated. If the absorber is in contact with the body, then heat loss is possible. The outer part of the device is protected by tempered glass with special properties. Antifreeze is taken as a coolant.

Operating principle

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

Photo 2. Scheme 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;
• the possibility of self-made installation and maintenance.

Flat-plate collectors are suitable for operation in southern areas with a warm climate. Their downside is high windage due to the large surface, therefore strong wind may destroy the structure. Performance drops in cold winter weather. Ideally, the unit should be installed on the south side of the site or house.

Vacuum

device consists of separate tubes, combined at the top and forming a single panel. In fact, each of the tubes is an independent collector. This is an efficient modern look, usable even in cold weather. Vacuum devices are more complex in relation to flat ones, therefore they are more expensive.

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 visits. Most often used in summer cottages and in private households. Mounted on the facades of buildings, pitched or flat roofs, special support structures. They function in cold climates and with short daylight hours without compromising efficiency. Due to the high efficiency, they are also used on agricultural land, industrial enterprises. This type is common in European countries.

Design

The device includes:

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

The design of the unit is a series of tubular profiles installed in parallel. The receiver and vacuum tubes are made of copper. The glass tube block is separated from the outer circuit, so that the activity of the collector does not stop when 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 vacuum thermal conductivity. An airless space is formed between the tubes, which reliably retains the heat generated from the sun's rays.

The vacuum manifold works like this:

• the energy of the sun is received by a tube inside a vacuum flask;
• the heated liquid evaporates and rises to the condensation area of ​​the pipe;
• the coolant flows down from the condensation zone;
• the cycle is repeated anew.

Thanks to this work much higher heat transfer and heat loss is low. Energy can be stored due to the vacuum layer, which effectively captures heat.

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

Advantages and disadvantages

The advantages of this type of device:

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

The equipment is expensive, which can only be recouped in a few years after use. The price of components is also high, and their replacement may require the help of a professional. The system is not capable of self-cleaning from ice, snow, frost.

Types of vacuum manifolds

Products are of 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 heat carrier container and glass vacuum devices are mounted to the frame at a certain angle, through a rubber connecting ring.

Equipment connects to the water lines through a constipation 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. Devices cannot be considered a full-fledged 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, drainage systems And for air recovery (treatment). It is used for drying agricultural products.

Design

Comprises:

• an adsorber, a heat-absorbing panel inside the case;
• 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 fixed vertically on the wall of the building.

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

Operating principle

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

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

Photo 6. Scheme of the device of an air solar collector. The drawing shows the main parts of the device.

Advantages and disadvantages

Advantages:

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

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

Choosing a set of solar collectors for the heating system

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

Power

To calculate the possible output of a solar system, you need to know 2 parameters: solar insolation in a certain region at the right time of the 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 the southern regions.

Less suitable for functioning in the cold aerial structure as at night it is not able to heat the air.

Trouble with heavy rainfall, because in winter the equipment often falls asleep with snow and regular cleaning is required. Frosty air takes away the accumulated heat, and the collector itself can be damaged by hail.

Scope consideration

In industry, the use of solar systems is more common. Solar energy is used in the operation of power plants, steam generators, water desalination plants. For heating water, heating a summer house or a bath in domestic conditions, vacuum collectors are more often installed, less often flat ones. Air systems help reduce the cost of heating by heating the air during the day.

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

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

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

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

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

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

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

Word to the Kulibins

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

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

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

What can be expected?

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

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

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

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

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

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

Subtotal

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

collectors

Principle of operation

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

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

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

What is AChT

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

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

Purchased SC

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

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

Types and purpose

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

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

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

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

flat

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

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

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

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

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

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

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

About the tank

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

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

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

vacuum

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

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

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

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

Also, with the blackening of the shell from the inside, pressure SCs are performed (inset at the top left in the figure). quick warm-up strong flow of water. Additionally, in the most efficient 1-circuit pressure SCs, the central (supply) pipe is also blackened, but it heats mainly the upward flow around it.

On the right in fig. - 2-circuit SC with a heat pipe and a double flask made of glass of different grades. It is these that feed CO all year round coolant with 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. Therefore, delving into the price lists, we pay special attention to:

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

Connection and strapping

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

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

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

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

About modular SCs

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

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

Compact

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

Homemade SC

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

box, glass, insulation

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

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

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

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

Pie

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

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

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

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

heat exchanger

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

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

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

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

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

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

Tank again

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

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

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

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

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

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

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

About Air Solar SCs

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

Video: homemade air-solar heating

Unusual homemade

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

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

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

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

Solar collector from Ildar bottles

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

Light Concentrators

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

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

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

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

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

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

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

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

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

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

Batteries

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

Principle of operation

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

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

Another word for the Kulibins

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

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

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

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

Item 3 requires additional explanations. Namely: SB is not capable of delivering extra current. For example, a starter battery (battery) with a capacity of 90 A / h briefly 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 more cannot be squeezed out of it by any means.

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

Device

One FEP without load creates a potential difference of 0.5 V. It is determined by the quantum properties of silicon and from no external conditions does not depend. Under load, the voltage of the solar cell drops, because. its internal resistance is great. Quantum mechanics does not cancel Ohm's law. Therefore, the battery voltage is taken with a one and a half margin: if, for example, 12 V SB is drawn from modules at 0.5 V, then they are taken 36 per pole, which will give an XX (idle) voltage of 18 V. For a one and a half voltage overload power supply, all DC consumers are calculated. The short circuit current of one solar cell is from several to hundreds of mA; it depends on the area of ​​the exposed (illuminated) surface of the element.

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

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

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

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

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

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

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

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

Purchased SB

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

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

Economy

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

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

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

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

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

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

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

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

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

Who to take?

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

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

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

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

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

Which ones to take?

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

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

About Primary Voltage

Most often, it is recommended to take a SB for 12 V. They say that you can turn on 12-volt economy 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 number of voltages. Secondly, the share of housekeepers in energy consumption is nothing at all, and they need separate wiring. But that's not the point.

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

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

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

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

Sat and homemade

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

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

Video: making a solar battery with your own hands

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

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

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

Video: tinning and soldering contacts

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

Video: element calibration

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

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

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

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

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

Installation and alignment

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

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

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

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

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

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

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

Finally

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

The total amount of solar energy that reaches the Earth's surface in just a week exceeds the energy reserves of oil, uranium, coal and gas worldwide. There are many ways to save solar heat. One such solution is solar concentrators. This is a special device for collecting solar energy, which performs the function of heating the heat-transfer material. Usually used for space heating and hot water needs. It is in this property that it differs from solar panels, which directly produce electricity.

Device

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

The device of the solar concentrator assumes the presence of the following elements:

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

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

Operating principle

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

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

• Parabolic trough concentrators that focus solar radiation on oil or water pipes
• Heliocentric towers.
• Special parabolic mirrors.

Solar radiation in certain models of concentrators can be concentrated:

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

Everything looks like this:

• Achieving high temperatures in concentrators is ensured by reflecting solar radiation from a larger surface onto a smaller surface of the receiver-absorber.
• The heat-carrier 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 shown in regions with a high degree of insolation, for example, in equatorial or desert regions.

In order to use solar radiation as efficiently as possible, it is necessary to ensure that the solar concentrators are oriented in the direction of the sun. For this purpose, the hubs are equipped with a tracker, that is, a special tracking system. It turns the system directly "face" to the sun.

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

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

Kinds

According to the constructive scheme of work, concentrators are divided into the following varieties:

• Parabolic solar concentrators.

• Parabolic trough 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 spectral characteristics.
• Refractive (lens) and reflective (mirror) systems - according to the nature of the interaction of sunlight 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 radiation concentration.
• With a tracking receiver, with a tracking reflector - according to the method of tracking the sun.
• liquid or air-convective heat removal - according to the heat removal method.

Peculiarities

• The radiation of the sun in some concentrators is focused at the 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 reached, 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 a high efficiency in regions where the level of insolation is especially high: in the equatorial region and deserts. To improve the efficiency of the application of solar radiation, concentrators are often equipped with tracking systems that provide accurate orientation to the sun.
• Since the cost of solar concentrators is quite high, and tracking systems need periodic maintenance, in most cases their use is limited to industrial power generation systems. In addition, such installations can be used in hybrid systems, for example, in conjunction with hydrocarbon fuels. In this case, the storage system will reduce the cost of electricity produced.

Application

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

Parabolic trough solar concentrators are currently one of the most advanced solar energy technologies. Most likely, they will be used in industry in the near future. Thanks to their efficient heat 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.

"Plates" 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 the demonstration of operational reliability and efficiency. For poppet-type systems, the development of an inexpensive concentrator and the creation of a commercial engine are needed.

Parabolic concentrators

Benefits - Proven technology.

Flaws:

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

towers

Advantages:

• Higher efficiency.
• higher temperature.
• Lower cost of energy.
• You don't need an ultra-flat landscape.

Flaws:

• High price.
• Low prevalence.

Solar concentrators with linear Fresnel reflectors

Advantages:

• Low energy cost.
• Simple design.