Solar panels are better on the parabola principle. Concentrators of solar energy. Video: DIY solar battery making

Published on 08/09/2013

An increasing number of great minds are interested in alternative energy. 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 wind turbine for generating electricity is not a very convenient solution. Variable wind power, chargers, batteries, inverters, a lot of not a penny equipment. In a simplified scheme, the wind turbine copes with water heating perfectly. 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 complicated expensive electronics. But calculations showed significant construction costs to spin the 500 watt generator.
The power carried by the wind is calculated by the formula P \u003d 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" an 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 500 watt generator with a wind of say 5 m / s. An area swept by the wind turbine propeller is required, about 12 sq.m. Which corresponds to a screw with a diameter of almost 4 meters! A lot of money is of little use. Add here the need to obtain a permit (noise limitation). By the way, in some countries the installation of a windmill must be coordinated even with ornithologists.

But then I remembered about 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 it needs 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. A figure of about 1 kilowatt per square meter sounds tempting. But this is at the equator on a clear day. How realistic is it to utilize solar energy for household needs in our latitudes (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 from cardboard (focus in the parabola bowl). The pattern of the sectors was pasted over with ordinary food foil. It is clear that the surface quality, and the reflectivity of the foil, is very far from ideal.

But the task was to heat a certain volume of water using the “collective farm” methods in order to find out what power can be obtained taking into account all losses. The pattern can be calculated using the Excel 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 temperatures, you can calculate the amount of heat spent on heating it. And, knowing the heating time, you can calculate the power. Knowing the dimensions of the concentrator, you can determine what practical power can be obtained from one square meter of the surface on which the 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 in the focus of a parabolic solar concentrator. The solar concentrator is oriented towards the Sun.

Experiment # 1

was held at about 7 am at the end of May. Morning is far from ideal time, but just in the morning the Sun is shining through the window of my "laboratory".

With a parabola diameter 0.31 m calculations showed that a power of the order of 13.3 Watt... Those. least 177 Watt / m2 It should be noted here that the round open can far from the best option for getting a good result. Part of the energy is spent on heating the can itself, part is emitted into the environment, including carried away by air flows. 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 from a hardware store was used as her mirror. Its reflective qualities are marginally better than aluminum foil.

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

This made it possible to project the rays onto one surface of the heater and obtain a high temperature in focus. The parabola can easily burn through a sheet of paper in a few seconds. The experiment was carried out at about 7 a.m. in early June. According to the results of the experiment with the same volume of water and the same container, the power was obtained 28 Watt., which corresponds approximately 102 Watt / m2... This is less than in the first experiment. This is explained by sun rays from the parabola to the round surface of the can is not always optimal. Some of the rays passed by, some fell tangentially. The jar was cooled by the fresh morning breeze on one side, while it was warmed 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 correct heat sink, the following design was made: a tin can inside, painted black, has pipes for supplying and removing water. Hermetically sealed with transparent double glass. Thermally insulated.

The general scheme is as follows:

Heating occurs as follows: rays from the solar concentrator ( 1 ) through the glass they penetrate into the can of the heat receiver ( 2 ), where, falling on a black surface, they heat it up. Water, in contact with the surface of the can, absorbs heat. Glass poorly transmits infrared (thermal) radiation, so losses due to heat radiation are minimized. Since over time the glass heats up with warm water and begins to radiate heat, double glazing was used. Ideal if there is a vacuum between the glasses, but this is an elusive task at home. On the reverse side of the can, it is thermally insulated with foam, which also limits the radiation of thermal energy into the environment.

Heat receiver ( 2 ) using tubes ( 4,5 ) connects 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 vessel and pipes should also be thermally insulated. The experiment was conducted at about 7 am in mid-June. The experimental results are as follows: Power 96.8 Watt, which corresponds approximately 342 Watt / m2

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

During experiments 1, 2, 3, the aiming of the parabola at the sun was done manually, "eyeballs". Parabola and heating elements were held by hand. Those. the heater was not always in the focus of the parabola, as a person's hands get tired and begin to look for a more comfortable position, which is not always correct from a technical point of view.

As you may have noticed, efforts have been made on my part to provide a disgusting environment for the experiment. Conditions are far from ideal, namely:
- not ideal concentrator surface
- not ideal reflective properties of concentrator surfaces
- not ideal orientation to the sun
- not ideal position of the heater
- not an ideal time for an experiment (morning)

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

Experiment # 4

Next, the heating element was fixed motionlessly relative to the solar concentrator. This allowed us to raise the power to 118 Watt, which corresponds approximately 419 W / m2... 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, while flat collectors have high temperature losses during the cold season. The use of solar concentrators can solve these problems, however, it 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. According to the ancient writers Plutarch and Polybius, the first person to practically use solar energy was Archimedes, who, with the help of some optical devices invented by him, managed to collect the sun's rays into a powerful beam and burn the Roman fleet.

In fact, 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 in 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 views, he had only two options.

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

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

Refractory solar concentrator

A prism concentrator of solar radiation is devoid of this drawback. Moreover, such a device is also capable of concentrating part of the diffuse radiation, which significantly increases the power of the light beam. The triangular 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 rear face reflects, and radiation is already coming out of the side face. The operation of such a device is based on the principle of complete internal reflection of rays before they hit the side face of the prism.

Unlike refractory ones, reflex concentrators work on the principle of collecting reflected sunlight into an energy beam. By 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 heat supply systems, mainly flat or parabolic-cylindrical systems are used.

Parabolic (reflex) solar concentrators

Practical application of solar concentrators

Actually, the main task of any solar concentrator is to collect the sun's radiation into a single energy beam. And you can use this energy in different 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 oven for cooking.

Parabolic concentrator as a solar oven

You can use them to provide additional lighting for 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 the order of 300 ° C - 400 ° C. If, for example, a stand for a teapot or a frying pan is placed in the focus of such a relatively small mirror, you get a solar oven, on which you can very quickly cook food, boil water. A focused heater with a coolant will allow you to quickly heat even running water, which can then be used for household purposes, for example, for a shower, washing dishes.

The simplest schemes for heating water with a solar concentrator

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

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 plants, special tracking systems are used that rotate mirrors or refractors to follow the movement of the sun, thereby ensuring the reception and concentration of the maximum amount of solar energy. For individual use, it will hardly be advisable to use such tracking devices, since their cost can significantly exceed the cost of a simple reflector on an ordinary 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 concentrator will be used, and then, based on this, choose an 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 plate.

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 about 5 - 7 centimeters in diameter. A bracket with a cookware support (burner) will be passed through this hole. This will ensure that the food container remains stationary when the reflector is turned in the sun.

If the plate is small in diameter, it is also recommended to cut the strips into pieces about 10 cm long. Glue each piece separately, carefully adjusting the joints. When the reflector is ready, it should be mounted on a support. After that, it will be necessary to determine the focal point, since the optical focal 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 to the sun, catch a sunbeam on the board and, bringing the board closer or away relative to the mirror, find the point where this bunny will have its minimum size - a small point. Gloves are needed in order to protect your hands from burns if they accidentally fall into the beam. Well, when the focal point is found, it only remains to fix it and mount the necessary equipment.

There are many options for self-manufacturing solar concentrators. In the same way, you can make a Stirling engine from the materials at hand. And this engine can be used for a variety of purposes. How much imagination, desire and patience will last.

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

People have to think about using more often more sustainable systems heating.

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

Solar collector for heating

The surface of this device has a low reflectivity, thereby absorbing heat. For space heating this mechanism uses the light of the sun and its infrared radiation.

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

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

Design

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

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

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

Principle of operation

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

Heated water tends upward, thereby pushing back cold water and forwarding it to a heat source.

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

The construction works like this:

1. The collector converts solar energy into heat.
2. The liquid enters the 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: it will not evaporate when high temperaturesah, be non-toxic, frost resistant. Usually they take distilled water mixed with glycol in a ratio of 6: 4.

Solar concentrator

Device for storing energy of sun rays, 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 lenses);
• on spherical lenses;
• parabolic concentrators;
• solar towers.

Concentrators reflect radiation from a large plane to a smallwhich helps to reach high temperatures. The liquid absorbs heat and moves it to the heating object.

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

Types of solar collectors

Currently, there are several types of solar heating collectors.

Flat, DIY installation

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

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

Scope of application

Similar collectors are more often installed in private housesfor heating rooms and supplying the premises with hot water. Appliances cope with heating 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 negatively affects performance. The equipment is mounted on the roof or facade of the building, as well as on any suitable surface.

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Flat collector design

The composition of the device:

• protective glass;
• copper tubes;
• thermal insulation;
• highly absorbent absorbing surface;
• aluminum frame.

A manifold with a tubular coil is the classic option. As an alternative to homemade constructions apply: polypropylene material, aluminum beverage cans, rubber garden hoses.

The bottom and edges of the system must be thermally insulated. If the absorber comes into contact with the housing, heat loss is possible. The 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 in a cooled form to the collector. The design is presented in two versions: single-circuit and double-circuit. In the first case the liquid goes directly 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 to the manifold.

Photo 2. Scheme and principle of operation of a flat solar collector. Arrows indicate parts of the device.

Pros and cons

Units of this type have the following advantages:

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

Flat collectors are suitable for work in southern areas with warm climates. Their disadvantage ishigh windage due to the large surface, therefore strong wind can disrupt 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 individual tubes combined at the top to form a single panel. In fact, each of the tubes is an independent collector. It is an effective modern look, suitable for use even in cold weather. Vacuum devices are more complex than flat ones, therefore they are more expensive.

Photo 3. Solar collector of vacuum type. The device consists of many tubes fixed in one structure.

Scope of application

Are applied for hot water supply and heating of large visits... They are more often used in summer cottages and in private households. They are mounted on building facades, pitched or flat roofs, special support structures. They function in cold climates and with short day lengths without compromising efficiency. Due to their high efficiency, they are also used on agricultural land, industrial enterprises. This type is common in European countries.

Design

The device includes:

• heat storage (water tank);
• a 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 external circuit, so that the collector's activity is not interrupted in case of failure 1-2 tubes.Polyurethane insulation is used as additional protection.

Reference. A distinctive feature of the collector is the alloy composition from which the pipes are made. it copper coated with aluminum and protected by polyurethane.

Operating principle

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

The vacuum manifold works like this:

• the sun's energy is received by a tube inside a vacuum flask;
• the heated liquid evaporates and rises to the condensation area of \u200b\u200bthe pipe;
• the coolant flows down from the condensation zone;
• the cycle is repeated again.

Thanks to such work much higher heat transfer rate, and heat loss is low. Energy can be saved due to the vacuum interlayer, which effectively traps heat.

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

Pros and cons

The advantages of this type of device:

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

The equipment is expensive, which can only be recouped in a few yearsafter use. The price of the components is also high and may require professional help when replacing them. The system is not capable of self-cleaning of ice, snow, frost.

Types of vacuum collectors

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

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

Equipment connects to the water supply lines through the shut-off valve, and a 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 the state of aggregation). not so whimsical, have a simple design. Devices cannot be considered a complete replacement for other types, but they are able to reduce utility costs.

Scope of application

Equipment of this type is used in air heating of houses, drainage systemsand for air recovery (treatment)... It is used for drying agricultural products.

Design

Consists of:

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

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

The device is located close to the object of heatingdue to large heat losses in the air lines.

Operating principle

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

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

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

Pros and cons

Advantages:

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

Disadvantages:limited scope (heating only), 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 to which the construction will be directed.The solar system is used to maintain air, provide hot water supply, and heat water for the pool.

Power

To calculate the possible capacity of the solar system, you should know 2 parameters: solar insolation in a specific region at the right time of the year and the effective absorption area of \u200b\u200bthe 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 is better suited for southern regions.

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

Inconvenience is caused by heavy precipitation, because in winter the equipment is often covered with snow and regular cleaning is required. Frosty air takes away the accumulated heat, and the collector itself can be damaged by hail.

Consideration of the scope

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

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 with their own hands by many. A house with electricity-generating solar panels and heat generators - solar collectors - on the roof, these days is not uncommon in places with a rather harsh climate, see fig. Moreover, there is still nothing to replace such an advantage of solar radiation as complete independence from the technogenic environment and natural disasters.

The picture for illustration is not for nothing taken "winter": modern models of solar collectors are capable of supplying the heating system with a coolant with a temperature of +85 degrees Celsius on a cloudy day with -20 frost outside. For the 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 the 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 the average level - an installation that will help the heating boiler save a considerable amount of fuel in winter, and the owners - money for it. Other uses for homemade solar collectors are possible; at least - heating the water in the pool. The prices of branded samples of this kind are clearly awkward in comparison with their capabilities, and there is nothing there that you cannot do yourself.

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

However, an individual purchased solar power plant can be profitable in mid-high latitudes, subject to careful technical and economic calculation and selection suitable model; not the least role in this is played by the stability of power supply in a given area. And the concept of a solar battery with your own hands can have a very definite and positive economic meaning for the owner, if some easy and free conditions for its manufacture and operation are observed, in the following cases:

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

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

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

A word to the Kulibins

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

However, it would be utterly foolish to blame those who like technical experiments. Thomas Alva Edison once said: “Everyone knows that this is impossible. There is an ignoramus who does not know this. It is he 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 profitability is higher than any securities.

Nevertheless, even the most general theoretical foundations of all further material are such that the most "a little on the fingers" pours out not in articles - in books. Therefore, we will further restrict ourselves to those samples for different occasions that can be made independently at home, without completely forgetting what they taught at school (by the way, there are quite a few of them); this is the first thing. Secondly, of these, we will restrict ourselves to devices that actually give heat or current, suitable for domestic and economic needs. You then have to take some of the author's statements on faith, or turn to fundamental sources.

What can you expect?

Here is an example of a telephone conversation with a trade manager of a company selling SB: "And under what conditions does your battery develop the declared capacity?" - "For any!" - "And in Murmansk (beyond the Arctic Circle) in winter too?" - silence, lights out.

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

Then the flow of energy from the Sun goes to the circle 4/14 \u003d 0.286 kW / sq. m or 286 W / sq. m. With the efficiency of the solar plant 25% (which is a good indicator), it will be possible to remove 71.5 W of power from the square, thermal or electrical. If the medium-long-term power consumption (see below) requires 2 kW (this is a typical case), then the converter panel is needed with an area of \u200b\u200b2000 / 71.5 \u003d 27.97 or 28 sq. m; it is 7x4 m. The efficiency is 25% - isn't it underestimated? Yes, you can squeeze more out of the panels. Much 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 spectrum of radiation from ultra-long radio waves to super-hard gamma radiation, in space on Earth's 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. Traders often do not know this, but you must bear in mind.

Well, what about the manufacturers' promises? 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 it looks clearly unrealistic in mid-latitudes under a fur coat of the atmosphere. Correctly declare, do not lie. Only the power was measured 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 for this they take electricity anywhere.

The card 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 operating in cloudy weather, are more difficult and more expensive than those that operate only in direct light. 365x24 \u003d 8760 hours in a year. Taking into account the fact that in high latitudes in summer the length of daylight hours is longer, the SC or SB may in Yakutsk or Anadyr turn out to be recouped during the estimated service life, but not in the Moscow region or Ryazan. Those. also bear in mind that solar energy as a beneficial aid to the conventional is not only possible in the Sahara or the Mojave Desert.

Subtotal

From this section follows an important conclusion for everything further: when looking for a panel for purchase or repetition, be interested first of all in the area of \u200b\u200bthe surface that effectively perceives (or absorbs) light, and only use it to calculate everything else. Moreover, it may turn out that according to marketing and consumer perceptions, 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 greenhouse effect lies at the heart of the work of any SC. Its essence is well known: take a camera 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 satisfied by silicate glass and plexiglass; almost entirely - quartz glass and other mineral glasses based on fused quartz.

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

Sunlight entering the camera will be absorbed by it and the camera will heat up. To avoid heat loss, we will provide it with thermal insulation. Then the thermal energy will turn into IR, but through the cover it will go outside and will not be able to dissipate. Now the IK has no choice but to heat the heat exchanger with the coolant placed inside or the air blown through the chamber. If they are absent, the temperature inside will rise until the temperature difference between the inside and outside "pushes" excess heat through the thermal insulation and thermodynamic equilibrium is established.

What is black body

To better understand further, you need to know how the pyramidal, or needle, black body model (BBB) \u200b\u200bworks; since we do not need others, further, if we are talking about the model of black body, "pyramidal-needle" is omitted everywhere. In Runet, and in the Internet in general, you really can't find anything about it, but in laboratory practice and technology, such 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 configuration of the efficiently absorbing surface (ESP) itself is closer in properties to the blackbody model.

Note: Black body is called a body that absorbs electromagnetic radiation of any frequency. Wood soot, e.g. - not black body, when photographing through an IR filter, it looks light gray. The pyramidal-needle model of the black body is capable of absorbing any, not only electromagnetic, oscillations. So, in acoustics, foam-rubber pyramids are used to paste over the inner surfaces of sound chambers.

Purchased IC

If you decide to buy a solar collector, you will have to face the price plug for 1 sq. m of absorbing area in 2000-80,000 rubles. And keep in mind that only the total cost is displayed in appearance, and if the EPP area is prescribed, it is in small print. Also, when choosing a model, you must definitely ask whether it is equipped with a storage tank and strapping 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. Practically - in more or less decent models, with proper operation, it is at least 15 years. Therefore, with a reasonable choice, there are no problems with payback, as long as the climate allows them to be used.

Types and purpose

In everyday life, SCs of 3 types of design are most 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 free-flow, with thermosyphon circulation, and pressure. The first ones are 1.5-5 times cheaper than pressure counterparts, because it is easier to ensure strength and tightness in them. Non-pressure SCs heat the coolant relatively slowly, therefore, they are intended more for hot water supply in the warm season. Strapping is simple and inexpensive; sometimes combined with a panel in one construct.

In the pressure head, the coolant is either pumped through 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 piping and a controller that controls it. The price is also growing accordingly. But only pressurized SCs are suitable for the cold season, because warm quickly. Most of the models are all-season; sold in the Russian Federation, taking into account climatic conditions, are most often designed to work together with a heating boiler, i.e. are auxiliary devices.

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

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

Flat

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

• Coating (transparent insulation) of glass.
• A kind of glass itself.
• Absorbent panel construction and quality.

Glass coating plays the role, first of all, of an antireflection film in optical devices: it reduces the refraction of light at the interface between media and light loss to lateral reflection. In correctly installed summer SCs (see at the end, before the conclusion), these losses are small or, in the southern regions, are completely invisible. In addition, the coating is abraded by wind-blown dust and is usually 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 with similar technical data, take the "naked" one, 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 - transmits 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 angles of incidence without antireflection.
4. Silicate with additives - structured or not, does not transmit UV, does not reflect IR and gives significant lateral reflection without anti-reflection coating. 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.

Based on this, for SC for permanent use, the choice should be made in favor of mineral structured glass. It allows you to use less space and often ultimately benefit from the cost of the entire installation. At a 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. The installation, in addition to being cheap, will be more compact and easier; on weekdays and for the winter, it can be covered with a cover or even taken to 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, in any calculations of the SC, one must remember how ottenash - the greatest savings are achieved by reducing the required area of \u200b\u200bthe panel (panels). At the same time, sellers are also checked: if, say, selective painting is declared in the specification and promises an efficiency of 75%, send them to a test stand under lamps, it is hot as hell. After all, it is clear that the efficiency of the entire installation cannot be higher than that of a part of it.

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 according to the season. And depending on the weather, the amount of insolation can "jump" day by day by 1.5-3 times, depending on the local climate. The heated water accumulated in the tank, provided it is well insulated, will take in excess heat on a clear hot day and give it back on a cloudy day. 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 RF often manages to reduce the required EPG area by half or more against that determined by the approximate calculation given above. Accordingly - and installation costs.

The vacuum SCs described below are inoperative without a heat storage tank. In them, it is either included in the finished construct, or is included in the delivery set. 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 SLR "Minolta" with a zoom lens they asked for as much as $ 190. And the crappiest 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 SC, the prices for optional or recommended branded tanks for them look overpriced simply ugly. Therefore, if you know how to tinker, it is better to make the tank yourself, maintaining only its volume prescribed in the specification for the panel. And do not believe the threats of the merchants - a homemade tank can be made no worse than a "firm". How - more on this further, 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 due in part to the design of the row-of-tube absorbent panel; the intervals 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 thermal insulation (for radiation, the vacuum does not provide it at all), but in the absence of air convection in the chamber. This allows the temperature to be distributed over the surface of the heat exchanger in an optimal way. In a gas-filled chamber, convection flows equalize it.

In fig. shows the device of 2 of the most common types of vacuum SC. Left - 1-contour summer or seasonal. Something like this is shown in Fig. with types of SK Russian "Dachnitsa". They are filled with such water, its outlet temperature is under 60 degrees. The role of vacuum is especially clearly visible here: 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 envelope of the flask is made of different types of glasses, see above. The inner tube is an energy receiver (PE) and a heat exchanger. A lot of controversy, up to mutual insults and vilifications on the forums, raises the question: which is better to blacken - the inner tube on the outside or the inner surface of the shell? From the point of view of the highest efficiency - PE. At the same time, IR losses are minimal, since the shell is made of highly reflective IR glass. This is exactly how devices for measuring insolation are arranged - actinometers, only there instead of tubes are spheres.

Therefore, it is better to take an inexpensive free-flow 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 kW * h / day, with a radiance of more than 2000 h / year, it can boil at the height of summer, and this is almost always means depressurization and complete failure. Here, a system with a blackening of the shell from the inside will be more reliable.

Also, with the blackening of the shell from the inside, pressure ICs are performed (inset at the top left in the figure) .In this case, at the cost of some IC leakage through the shell, its high concentration along the flask axis is achieved, which is necessary for good and quick warm-up strong flow of water. In addition, in the most effective 1-circuit pressure head SCs, the central (supply) pipe is also blackened, but it is heated mainly by the ascending flow around it.

On the right in Fig. - 2-circuit SC with a heat pipe and a double flask made of different types of glass. 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:

• Whether the supplier calculates the installation from on-site measurements.
• Is the harness included in the delivery set (see below).
• Do company specialists connect the installation to the existing CO.
• Are the declared parameters guaranteed in this case?
• How long is the warranty valid.
• Whether and how much is scheduled and extraordinary maintenance provided.

Connection and piping

To prevent freezing and bursting in winter, year-round pressure head SCs are filled with antifreeze. A simplified diagram of their connection is shown on the left in Fig: the controller, according to the temperature ratio at the supply, return and in the tank, "spins" the circulation pump as required.

Pressure heating solar systems are equipped with a storage tank with thermal insulation. In the Russian Federation, the most sold systems are designed for connection to operating CO with a boiler. The solar water heater must be designed accordingly, in the center in fig. In addition to the 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 is wound in a cone at the bottom 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 acid condensate may fall out in it, quickly causing the boiler to fail. When the Sun does not shine and the SC cannot help the boiler in any way, a water lock forms in the conical spiral, which does not allow the cold "pillow" to rise up to the boiler coil.

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

About modular IC

The systems described above are integral constructs. But there are also modular SCs on sale, recruited from panels until the required parameters are obtained, for example, the Russian Helioplast, see fig. on right. By connecting the panels in parallel or in series, you can get either a higher coolant flow or a higher temperature. The cost of modular SC is considerable, for example. 1 panel "Helioplast" 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, 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 in relation to technical parameters are incredible; Mercedes-Benz with its "star", here, as they say, is resting. The design is simple and completely repeatable with your own hands, see the section on light concentrators.

Homemade SC

For self-production, most of all flat country-house summer SCs for hot water supply are available. Seasonal heating turns 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 scrap materials, craftsmen sometimes create samples that are inferior to the best industrial ones, except in appearance, but cost literally a penny. Let's go in order.

Box, glass, insulation

The body of a homemade flat SC is best made of 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 no cracks form due to thermal deformations. A board (120-150) x20 will go to the sidewalls. It is undesirable to make the body below. leakage of IR through glass will increase. Outside, paint as you like, but inside - as a "cake" substrate, see below. The dimensions in the plan are calculated based on the amount of insolation and the required power.

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

Insulate the body with foam; for summer SC, 20-30 mm is enough. Insulate in 2 layers of equal thickness with aluminum foil gaskets, but more on that below. It is necessary to insulate the box for strength from the inside. If you have read articles about the insulation of buildings, please note: with a temperature difference that a flat SC provides, and with a sufficiently high outside temperature, there is no need to talk about dew point wanderings.

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

Pie

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

The second highlight of the "pie" is painting. They are painted at the same time with the heat exchanger already installed on the clamps. It is necessary to paint with oil (slowly drying) black paint on the pigment "Gas soot"; it can be purchased from art stores. Inks based on synthetic pigments in infrared rays will not be black at all.

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

Note: a very good option is an old thin-walled stamped heating battery. Then there is no need to look for aluminum. Only it is necessary to paint, as described above, and not leave 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 BBT 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, 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. Nevertheless, a flat spiral heat exchanger can be used in a home-made SC for a pool with a compact concentrator, see below.

The best heat exchanger is a zigzag one made of a copper tube with a lumen of 10-12 mm in diameter. Why exactly like that? 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 capable of accepting at a given temperature difference; for homemade SC - 15-25 degrees. Otherwise, the leaving water temperature will be too low at first, and it will have to make many revolutions in the system until the tank heats up.

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 bending radius, 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 from the point of view of heat transfer. And you can use a regular manual pipe bender.

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

Without knowing these circumstances, you can commit typical mistakes, see fig. On the left, a thick pipe with wide loops will not accept all the heat generated by the box at once. 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 take a long time to warm up. Besides, the nightmarish work of assembling, identifying and fixing leaks ("All sealed joints are flowing" is one of Murphy's laws). On the right - everything seems to be OK, including the heat exchanger coating (the radiator of the old refrigerator). But the lumen of the tube is 3-4 mm, this is not enough. The IC that has not pushed its way to the water has nowhere to go, except in vain outside, and the increased resistance to the flow of liquid (water is not freon) guarantees low efficiency and slow heating.

Note: The efficiency of the SC described above, with a neat design, exceeds 20%, which is comparable with industrial designs of this type.

Tank again

It's time to tackle the battery tank closely: without it, the SC will be of little use. Let's start with calculating the volume - we need to take everything from the Sun that allows the SC and keep it longer; this is especially important if heating is also involved from the panel. The small tank will soon warm up and then the SC will "fire" without benefit, because he cannot warm up to infinity. In a too large tank, the water will not have time to heat up to the temperature that the SC is capable of providing in a day, and again we do not fully use the thermal potential of this area. Why take - for a day? Because we are counting on seasonal use with heating, and heating may be needed by nightfall. In the summer at the dacha - to wash, without waiting for the evening; preferably for several people.

Let the places we have are not entirely gloomy, and we get 4 kWh / day. Then, see above, Sun on 1 sq. m pours out a power of 286 watts. Let's take the dimensions of the EPG as 1x1.5 m (for example, if you make a big one, it won't get any worse), i.e. EPP area - 1.5 sq. m; The efficiency of the SC will be 20%. We get: 286 W x 1.5 x 0.2 \u003d 85.6 W, this is the thermal power of our panel. 1 W \u003d 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 \u003d 3 697 720 J or 3 697.72 kJ.

How much water can it take in? Depends on the temperature difference. Let's take the initial 12 degrees (shallow water supply in spring / autumn or a well); the final one is 45 degrees, i.e. heating will be 33 degrees. The heat capacity of water is 1 kcal / l or 4.1868 kJ / l (1 cal - 4.1868 J). When heated by 33 degrees, 1 liter of water will take 4.1868 x 33 \u003d 138.1644 kJ. The capacity will only need 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 don't people wash under the sun shower? Heating is a fool for now, it is clear that at least 4 panels are needed here. And heat loss would not hurt to take into account, at least 20% of the accumulated overnight. That's right, the technique is to get around the limitations of a stubborn theory. By the way: "There is nothing more practical than a good theory" - this is the same great practitioner Edison. Only technical calculations and calculations turn out to be much more cumbersome, so we just give the result - schemes of tanks powered by a water supply system and with manual filling, see Fig.

The idea is that one can wash himself in the summer 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 a suction from a flexible hose on the float. The length of the flexible link should be taken moderately: if it is too short in a full tank, the hose will stick up, and too long with a low water level will fall on the tank wall.

The arrangement of the nozzles is designed so that hot and cold streams mix as little as possible in any application, i.e. we deliberately stratify water by temperature. The best vessel for a tank is a barrel laid on its side. Then the sludge (sludge) will take up a small part of its capacity. Insulation - polystyrene from 50 mm. And you need to provide for another 1 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 selection pipe of the return must be raised above the bottom, otherwise the sludge will soon clog the SC, and it is difficult to clean it. The pipes are regular plumbing, 1/2 to 3/4 inches. Flexible link - PVC-reinforced hose for irrigation; its float is styrofoam.

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

About air-solar SC

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

Video: homemade solar-air heating

Unusual homemade products

An 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 different signs.

In fig. - air, i.e. simpler than water, SK from beer cans. Let's not giggle into a fist or be indignant: "I won't drink so much!" Let's take a technical look. The idea itself is quite sensible: the gaps between the rows of cans bring the panel's ability to absorb light closer to the blackbody model. But! Materials - aluminum, wood, silicone sealant. Their coefficients of thermal expansion (TCR) 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 flow much, it is a miracle.

And here is a solar collector made of plastic bottles in Fig. below looks less elegant, but quite workable. In essence, this is a chain of linear light concentrators, see below. The containers are assembled into "sausages", as in the construction of greenhouses, hotbeds, gazebos, etc. lightweight buildings made of bottles, but they are strung not on a rigid rod, but on a transparent PVC hose. The back of the "sausages" is covered with aluminum foil, at least with a baking sleeve. In this case, the fact is used that water itself absorbs IR well. 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 lower surface of the bottles. When installed on a south-facing roof slope, no frames, supports, roof bulkheads or reinforcement of the roof transom (supporting frame) are required. There are many joints, but materials similar in TCR fit, so the reliability is sufficient. The joint will be the strongest in pos. B, when the bottles are piled on top of each other. They repeat "Ildar" a little, but in vain. Apparently, it is embarrassing that the water flow is shown opposite to the thermosyphon one. But the thermosiphon head is much weaker than the gravitational head from the tank, so the Ildar is quite efficient.

Solar collector from bottles "Ildar"

Note: in bottle SCs, the length of 1 "sausage" should be about 3 m in middle latitudes, and in parallel, connect as many as there are bottles 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 plant more compact, as they sometimes write. 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. The solar concentrator, or solar concentrator, allows you to solve the following tasks:

1. To simplify the design of the radiation receiver, to make the most complex part of the solar system more compact and to reduce the number of joints requiring sealing in it.
2. Increase the illumination of the radiation receiver and thereby enhance the light absorption.
3. Increase the temperature of the coolant, which makes it possible to use the accumulated energy more fully.
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 industrial installations to achieve greater overall system efficiency. It is difficult to make such installations at home, because a system of continuous accurate 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 setup even in cloudy weather, you do not need to deal with the light concentrators.

The main schemes of solar concentrators are shown in Fig. there everywhere 1 - collecting system, 2 - 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 adapt a satellite dish, but you probably know the prices for them. And you need to make electronics that control a precision 2-axis electromechanical drive. A scheme with a Fresnel lens d) is sometimes used to increase the efficiency of small-sized solar cells, but they degrade much faster, see below.

We will deal with linear concentrators, pp. a) and b), as the most suitable for self-made solar plants. The scheme in the form of a semi-cylindrical mirror a) was generally considered earlier, together with the bottles. You can only add that you can orient it (see below) both along the meridian and perpendicular to it, depending on how you want to direct the water flow in the receiver pipe. This concentrator accelerates the heating of water, but when oriented along the meridian significantly reduces the length of daylight hours for the receiver, because at angles of incidence from the side more than about 45 degrees from the normal, the light does not catch at all. The re-reflection in it is always one-time. The light transmittance in the 0.35 mm aluminum foil + PET system is about 0.7.

A concentrator of oblique incidence mirrors b) captures light within the angles of incidence from the normal of 60 degrees or more. Can be performed linear and point. The visible decrease 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 dramatically. 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 wishing to make such a profile of the mirrors, see Fig. The grid step is selected based on the actual dimensions of the installation. Please note that the alignment is needed, though one-time, but accurate: on June 22 or in the coming days at astronomical (not zone!) Noon, the wings are pulled / spread and bent so that the caustic (a bright strip of concentrated light) lies exactly along the receiver tube ... Its diameter is about 100 mm, the material is thin blackened metal.

Most likely, one of the types of compact non-orientable concentrators will be of greater interest to the home-builder, see next. fig. It does not need to be aimed 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 coiled into a spiral, supply it with this concentrator, and we get a water heater for the pool.

To bring the rays of the Sun to a point, the concentrator belts need a parabolic profile (inset at the top left in the figure), but our receiver is long and round, so you can get by with conical ones. What dimensions and ratios must be maintained in this case is clear from Fig. The extreme belt (marked in red) hardly increases 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 just when you need it.

Batteries

Now we will deal with solar panels (SB). To begin with - a little theory, without this you cannot understand what and when are good and bad in them. And how to choose the right SB to buy or do it yourself.

Principle of operation

At the heart of the SB is an elementary semiconductor photoelectric converter (PEC), see Fig. on right; if someone sees there "non-folding boxes" 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. This thing is very complex, understanding it requires knowledge of quantum mechanics and a number of other disciplines. In a very simplified way (forgive the physicist-technologist if he reads it), the principle 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, whose atoms are capable of being embedded in the silicon crystal lattice without violating it; this is the so-called. alloying. n-region (cathode) doped with donors; p-region (anode) - acceptors.
2. Donors create an excess of electrons in their area; acceptors in their - equal to them in magnitude of positive charges - holes, this is a completely correct physical term. Electrons and holes from alloying additives are the so-called. minority charge carriers. The holes are not antiparticles, positrons, they are simply places where an electron is missing. Holes can wander (drift) within the crystal, because acceptors intercept each other's electrons all the time.
3. Electrons with holes are attracted to each other, trying to mutually neutralize (recombine).
4. In a crystal (this is where its quantum properties are played out with might and main) they cannot freely unite in a finite period of time, therefore large space charges of the corresponding sign are formed in the boundary layer; in general, 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 can only drift within the crystal.
7. The electrons have no choice but to go through the electric 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 them into the circuit again and again while the crystal is illuminated.

Another word to the Kulibins

Most often, radio amateurs and electronics engineers take on home-made SBs. As a rule, they understand the basics of semiconductor theory. For them, just in case, we will explain how the FEP differs from a similar diode, and why it will not work to squeeze out a significant photocurrent from the crystals of diodes / transistors:

• The degree of doping of the anode and cathode of the PVC is orders of magnitude, and even many orders of magnitude higher than that of active electronic components.
• The cathode and anode are doped to about the same degree as the planar-epitaxial technology allows.
• The boundary region is wide (in this case it is possible to call it a p-n junction only with a great stretch), so that there is more "working space" for light quanta, and the space charge in it is very large. In component manufacturing, electronic circuits tend to do the opposite in order to improve performance.

The features of the structure of the PVC are based on the fact that it is not a receiver of electricity in the form of an applied voltage, but its generator. From here follow the conclusions that are already important for any user:

1. Because There are always more quanta of light that have fallen into the crystal than there are free electrons there, the extra quanta spend their energy on exciting the atoms of the crystal, which is why it deteriorates over time, this is the so-called. degradation or aging of FEP. Simply put, the SB wears out, like any equipment, and eventually sits down, like any electric battery.
2. The passage of electric current when the FEP is connected to the consumer circuit accelerates degradation, because electrons forcibly drifting in the crystal, so to speak, hit the atoms and gradually knock them out of their places.
3. The energy reserve in a PVC is determined by the volume of the space charge; sunlight only initiates its redistribution.
4. FEPs and SBs consisting of them are afraid of contamination: 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 producing extracurrents. For example, a starter battery (accumulator battery) with a capacity of 90 A / h briefly delivers a current of 600 A. Theoretically - even much more until it explodes from overheating. But, if the specification on the SB says "Short-circuit current (short circuit) 6A", then more from it and not squeeze out in any way.

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

Device

One PVC 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. The PV voltage drops under load, because his inner 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 recruited from 0.5 V modules, then they are taken 36 per pole, which will give a voltage of XX (open circuit) of 18 V. For one and a half overvoltage all DC consumers are calculated. The short-circuit current of one FEP is from several to hundreds of mA; it depends on the area of \u200b\u200bthe exposed (illuminated) surface of the element.

Modules (elements) from many PVCs, connected on a common substrate in series, in parallel, or this and that, come on sale and for assembly; their XX voltage and short-circuit current are indicated in the product specification. Associated with this is a common misconception that, they say, SB should be recruited only from 0.5 V elements, while others are substandard. On the contrary, modules from a bona fide 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 PVCs are grown on one plate and their parameters exactly coincide.

In the SB solar battery circuit (see fig.), The PE modules are connected to the E pillars, providing the required voltage; usually 12, 24 or 48 V. The poles are connected in parallel to obtain the required operating current. Because the modules in the pillars are not necessarily made of the same crystal, the internal resistances of the pillars are slightly different, and the voltage “floats” under load. A reverse current will flow through the pillars, a little more powerful (with a lower internal resistance), and from it the degradation of the FEP occurs rapidly. To radio amateurs, you can remember that if the diode is even slightly opened "from the side", it starts to pass the reverse current as well, this is the basis of the thyristor's operation. Therefore, the poles are blocked from the "return" by VD diodes. Schottky diodes are most often used, because the voltage drop across them is small and they do not need additional cooling at high currents. But sometimes (see below, about SB-homemade products), you may need a diode with a p-n junction.

When turning on / off powerful consumers, so-called. transient processes accompanied by extracurrents. For just a few milliseconds, but a gentle sat is enough to get you down quickly. Therefore, a GB buffer battery is required for powering powerful devices. The controller C controls the distribution of currents in the SB; it is a controlled current source that regulates and limits the SB operating current together with the battery charging current. In the simplest case, the battery discharge is free according to the level of consumption. Inverter I converts the direct current from the battery into alternating current 220 V 50 Hz 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 constantly. To build a SB according to the scheme of "deaf" UPS, in which the battery gives current only when the network is lost, means to condemn the SB to rapid degradation due to extra currents. The battery life in the "flow-through" scheme is significantly reduced, but there's nothing you can do about it, except to use expensive batteries with gel electrolyte. So there is no need and again no need to design a SB with computer UPS. Second, the operating current should be taken approximately 80% of the short-circuit current. If, for example, according to the calculation, the primary circuit current of 12 V is 100 A, then the SB must be designed for 120 A.

Third - in this scheme, 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 SES, the strapping is supplemented with a battery overdischarge alarm (it beeps even more disgusting than a UPS without a network) and automation that turns off the inverter if the owners ignored the signal. In the most expensive SPPs, the inverter has several outputs, the 220 V wiring has several branches, and the automation switches off consumers in the reverse order of their priority; refrigerator, e.g. last.

Sat without strapping is usually called a solar panel. Its design (see Fig.) Ensures, first of all, a reduction in light degradation, then - efficient use of light and mechanical strength. The first gives mainly a special glass, cutting off quanta, which will certainly not give current; the PEC sensitivity to rays of different spectral zones is significantly uneven. EVA film also provides some light filtering, but it is more intended to increase efficiency: it reduces light refraction and side reflection, i.e. anti-reflective coating. Glass, EVA and the elements under it are "molded" into a single pie without air gaps, so this design is not for amateurs. The PET lining is, firstly, a mechanical damper (crystalline silicon is a fragile substance, and the element plates are thin). Secondly, it insulates the modules from the panel case electrically, but provides heat transfer to the elements that are heated during operation, because PET conducts heat better than other plastics. It has already been said about diodes. The entire cake is placed in a durable metal case (it also serves as a heat sink) and carefully sealed.

Note: flexible SBs are also 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 supplied current. Flexible SBs are used mainly to supply low-power DC consumers in various mobile or remote unattended facilities.

Purchased SB

To prepare for the purchase or manufacture of SB or SES, you need to master the concepts of peak 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 \u003d 5500 W or 5.5 kW from the network. This is your peak consumption, but if you count on the power grid at the peak, then it will come out unreasonably expensive: powerful consumers do not turn on for a long time and all at once.

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

Economy

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

• The efficiency of monosilicon SBs is more than twice that of polysilicon (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 buffered acid battery is 74%, and other types of them, except for the terribly expensive lithium ones, are poorly suited for buffer storage.

Taking into account these factors and the climatic conditions of the Russian Federation, the price of 1 Watt levels out and turns out to be about 130-140 rubles / Watt. SB for 1.1 kW, thus, will cost somewhere in the 140-150 thousand rubles. How long will it last? Security service terms are not regulated in any way; manufacturers usually give 5, 10, 15 and 25 years. That, according to the final inspection, will not last 5 years, is sold item by item for self-assembly. Take into account, homemade people!

The price of the finished SB, of course, grows according to the service life. After studying the company declarations and calculations, the SB turns out to be the most profitable for 15 years. There is an insidious subtlety here: SB are available in Grade A, Grade B, Grade C and Ungrade (substandard) conditions. Accordingly, the power of the SB by the end of its service life decreases by up to 5%, 5-30% and over 30%. However, if you buy SB Grade A for 5 years, then you cannot expect that it will then last another 25 until it withers by 30%. Due to an increase in the load on the remaining serviceable solar cells in the element, the degradation process develops like an avalanche: it lasts for another six months or a year, and mono - 2-4 months.

So, we consider further. With the correct choice of the primary constant voltage (see below), 1 replacement of the battery will be required in 15 years, costing about 70 thousand rubles. Plus strapping, wires, tires, switching elements, metal structures or work on the roof, this is about 150 thousand rubles more. The battery will cost about 30 thousand; it is categorically impossible to put a battery in residential premises. We have:

1. Sat - 150,000 rubles.
2. Joint stock bank - 140,000 rubles.
3. Strapping - 150,000 rubles.
4. Rechargeable battery - 30,000 rubles.

Total RUB 470,000 A turnkey SPP of the same capacity will cost about 1.2-1.5 million rubles. But how justified is this or that?

In 15 years 15х24х365 \u003d 131,400 hours. During this time we will consume 131 400x1.1 \u003d 144 540 kW / h. 1 kWh from your own solar power plant will cost 470,000 / 144,540 \u003d 3.25 rubles. You know the current prices (from 3.15 to more than 6 rubles). The benefit seems to be not very good, given that these "half-lemon" need to be taken somewhere else, without getting into debt at the current credit rates. Nevertheless, building a SES for yourself is already justified in such cases:

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

From whom to take?

However, it's too early to run for batteries. In the security market, the situation is very difficult: high and disordered, on the verge of a rush, demand all over the world generates tough 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 the actual quality. But China is a very controversial country; There are plenty of Shanghai-Wuhan offshore basements masquerading as reliable state-owned enterprises. On the other hand, the western "whales" of the industry, in a panic under the threat of bankruptcy, are going all out, just to get the goods in, not sparing their good name.

In Russia, there is a good outlet for choosing a manufacturer. 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; Intel's first CPUs, by the way, were made of Soviet silicon, Silicon Valley was still developing. But on a shaft, Soviet-Russian electronics has never been noticeable in the world; worked mainly for the war. During perestroika, products better than the then world ones flashed on sale, but it was too late to compete with the "sharks". For example - see fig. It works flawlessly so far, calculations for the article were made on it. And his more expensive and less-capable peers Casio and Texas Instruments have worn out the keys and sat down for a long time.

Currently, there are several enterprises operating in the Russian Federation with clean rooms, trained personnel, engineering and technical personnel and experience in this field. They stay afloat thanks to the correct market tactics: they buy SB components from trusted Chinese suppliers, pass them through their own incoming control and assemble them in panels according to all the rules of technology. The declared parameters of their products can be trusted unconditionally. Unfortunately, after the past perturbations, there are not many of them left:

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

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

Which ones to take?

That statements like “mono is cool, poly sucks” are emotional rather than substantiated, you are probably already clear. The difference between them, by the way, is not so fundamental. Silicon pigs of the highest quality, the most uniformly recrystallized, are used for large chips. 1st condition - for medium integration, 2nd - for discrete components, and only 3rd - for SB. "Mono" differ from "poly" in that in the former on a cut of one crystal in a blank (crystallite), several PVCs or 1 large one are grown; In polysilicon SBs, small PVCs each occupy approximately 1 also fine crystallite.

However, rogue manufacturers and traders are trying to give out completely unusable mono polys, replacing the designation with similar ones in meaning, but with the letter "m" at the beginning: multicrystalline, microstructural, etc. Therefore, we remind you: polycrystalline SB modules are blue, most often with noticeable iridescence (tints of colors), on the left in Fig. Monocrystalline very dark to completely black; if there is irisation, it is not noticeable, on the right in the same place In general, it is impossible to determine the quality of the module by eye or by electrical measurements; laboratory chemical, crystallographic and microstructural analysis is needed. What traders-rogue with might and main use.

About primary voltage

Most often, it is recommended to take a 12 V SB. Like, you can turn on 12-volt housekeeping bulbs and you don't need a special controller. Firstly, DC equipment for 24, 36 and 48 V is not "special" at all, these are standard values \u200b\u200bof a number of voltages. Secondly, the share of housekeepers in energy consumption is nothing at all, and they need a separate wiring. But this is not the main point.

Above it is calculated - for an average house you need a buffer battery for 5.5 kW peak. The current from it with an hourly discharge will be 5500/12 \u003d 458, (3) or approximately 460 A. There are cans for batteries with a capacity of up to 210-240 A / h on a wide sale, of which starter batteries of heavy special equipment are recruited. Not to mention the cost, paralleling the battery is indispensable, and no more SB elements like to work in parallel with the battery, and for the same reasons; this is a common property of all direct current sources. As a result - a battery for 100-120 thousand rubles. will last 5-6 years at most, and 2-3 replacements will be needed in 15 years.

And now let's take the "primary" DC at 48 V. It would be better to 60-72, direct current up to 100 V is safe, only SB does not do such. In terms of the impact on the human body, 50/60 Hz are the most dangerous frequencies, only there is nowhere to go, their values \u200b\u200bhave developed historically. Then we get with an hourly discharge 5500/48 \u003d 114.58 (6) A and the capacity of the battery is 120 A / h. This is an ordinary car battery, plus you can use long-lasting sealed AGM, GEL, OpzS, if you don't mind the money. And the worst of all (auto-starter) will last at least 8 years, or even all 15. And it will cost half the price of a huge one.

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

Note: and God forbid you to connect the SPP to the street input! We'll have to pay the uncles on the counter for their expenses and labors. It is necessary to put a packet bag after the counter (this is a subscriber wiring and here you are a complete master, just don't forget about TB) and switch back from the Sun to the general network, suddenly you need it. For example, when replacing the battery or prolonged bad weather.

Sat and homemade products

The first thing that an amateur solar energy needs to know is that discarded modules are scattered on sale, which 5 will definitely not work. Even if you organize cleaner production at home, they are already "poisoned" with slow-acting poison - harmful impurities. In addition, to make a branded "cake", 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 the removal of ohmic heat, the 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, DIY can be useful as 100 W of their power will cost less than 3000 rubles. Which ones - let's see a little below, but for now let's dwell on the assembly technology. It is shown quite fully here:

Video: DIY solar battery making

You can add little. First, do not take into work an obvious waste, sent in bulk, on the left in Fig. Better to buy a constructor, see fig. on right. They are equipped with flux pencils and special conductors, which greatly reduces soldering rejects.

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-plated (silicon is not soldered), the silver layer is thin and barely holds. At home, it probably withstands only 1-fold soldering (in the production of automatic machines - 3-fold), and with a soldering iron with a nickel-plated bronze tip. Do not try to tin it, they solder dry with such a soldering iron.

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 need to be calibrated and the pillars must be assembled from plates with approximately the same parameters (see video below). It is almost never possible to pick up modules for 48-volt poles from substandard ones, so home-made SBs are made 12-volt or 6-volt.

Video: Calibrating Elements

Now about the cases when it makes perfect sense to make a solar battery yourself. The first is the rubber 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 a 12VDC / 220VAC 50 Hz inverter for 200-300 watts. For a TV, a small refrigerator and a music center, this is enough. Switch S2 is working, S1 - for repair and emergency and for winter storage.

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

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

Switch S1 and bright white LED D3 are test ones. 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 SB, the price is cheap. By the way, it's a good practice to work with solar cells before taking on a large sat, and it will be a useful tool.

Video: mini solar battery to charge your phone - assembly and testing

Installation and alignment

Installation of solar panels and collectors of a stationary structure is carried out most often on the roof. There are 2 possible solutions: either disassemble a part of the roof and include the SK / SB body in the power circuit of the roof girder (its frame without a roofing cake), 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 should be reinforced with crossbars.

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

As for mobile (mobile) or free-standing ground panels, they are mounted on a three-dimensional frame or a 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, quite good.

It is necessary to orientate fixed panels to the maximum annual average (seasonal) insolation (align) as accurately as possible. The chicken bites a grain, and saves a penny a ruble - in this case, these sayings are fully reflected in relation to the payback period of the installation. Azimuth is set exactly along the meridian. If you are using a compass for this, you need to take into account the magnetic declination of the place; in GPS or GLONASS devices - enable the corresponding correction. You can also beat off the midday line (this is the meridian), as described in school textbooks on nature, geography, astronomy, or, say, in the guides for the construction of a sundial.

The tilt of the panel in elevation α, depending on its geographic latitude φ, is calculated for different cases with a correction for the inclination of the earth's axis β \u003d 23.26 degrees, as a result of which the height of the Sun in mid-latitudes changes according to the seasons:

• For summer installations α \u003d φ-β; if α \u003d<0, панель укладывается горизонтально.
• For seasonal spring-summer-autumn α \u003d φ
• For year-round α \u003d φ + β

If in the latter case α\u003e 90 degrees comes out, you are beyond the Arctic Circle, and you do not need a winter panel. Further, for simplicity and accuracy in terms of the angle α, the lift of the northern edge of the panel is calculated in units of length as h \u003d Lsinα, where L is the length of the panel from south to north. Let's say a panel 2 m long is installed along the meridian. α came out at 30 degrees. Then the north edge (sin 30 degrees \u003d 0.5) needs to be raised 1 m. With sinα \u003d 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 there is little honor to take what is bad. But to come to 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 (the cultivation of badlands), 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 to be worthless), and in Russia - at least the construction of the Trans-Siberian Railway, which still has no analogues. Here self-made people have a place to roam and, if a "Russian solar miracle" happens, for sure this will be their considerable merit.

The total amount of energy from the sun that reaches the Earth's surface in just a week exceeds that of the world's oil, uranium, coal and gas reserves. There are a variety of ways to conserve heat from the sun. One of these solutions is solar concentrators. This is a special device for collecting solar energy, which performs the function of heating the heat carrier material. Usually used for space heating and hot water supply. 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 at the focal point of the solar collector.

The solar concentrator device assumes the following elements:

• Lenses or reflectors used to concentrate the sun's rays.
• The base structure on which lenses or reflectors are mounted.
• Heat-sensing element, which is often a solar collector.
• Pipelines that supply and remove the coolant.
• Tracking system drive mechanism. This mechanism in most cases includes:
  - Electronic signal conversion unit.
  - Sun direction sensor.
  - An electric motor with a gear that turns the structure of the solar concentrator in two planes.

Depending on the design, the device can also include a Fresnel lens, 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 focusing the rays of the sun on a container with a coolant.

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

• Parabolic cylindrical concentrators that focus solar radiation on pipes filled with oil or water
• Tower-type heliocentric plants.
• Special parabolic mirrors.

Solar radiation in certain concentrator models can concentrate:

• At the focal point.
• Along the focal line that contains the receiver.

Everything looks like this:

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

To be able to use solar radiation as efficiently as possible, you must ensure the orientation of the solar concentrators 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 straight to face the sun.

Uniaxial tracking 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 hundred times 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 drives the turbine of the steam generator. To minimize heat loss, the receiving tube is surrounded by a transparent glass tube that runs along the focal line of the cylinder.

Views

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

• Parabolic solar concentrators.

• Parabolic cylindrical concentrators.

• Solar towers.

• Spherical lens concentrators.

• Fresnel lens concentrators, i.e. 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 impact of concentrated radiation on spectral characteristics.
• Refractive (lens) and reflective (mirror) systems - by the nature of the interaction of sunlight with
  optical elements of solar concentrators.
• Without tracking, equatorial, azimuthal-zenith system - according to the sun tracking scheme.
• Single and multielement systems - according to the number of optical elements that are consistently involved in the process of radiation concentration.
• With a tracking receiver, with a tracking reflector - using the method of tracking the sun.
• liquid or air convective heat removal - by the heat removal method.

Features:

• Radiation from 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 achieved, this heat is removed by the coolant.
• The efficiency of concentrators decreases significantly during cloudy periods, since only direct solar radiation is focused. In this regard, such systems have high efficiency in regions where the level of insolation is especially high: in the equator and deserts. To improve the efficiency 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 the tracking systems need periodic maintenance, in most cases their use is limited to industrial power generation systems. In addition, such units can be used in hybrid systems, for example, in conjunction with hydrocarbon fuels. In this case, the storage system will reduce the cost of the supplied electricity.

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.
• Poppet-type systems are made of modules; they can be used in stand-alone installations and groups with a total power of several megawatts.

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

"Trays" and towers allow for higher efficiency values \u200b\u200bwhile 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 a demonstration of operational reliability and efficiency. For poppet-type systems, an inexpensive concentrator and commercial engine is needed.

Parabolic concentrators

Benefits - proven technology.

Disadvantages:

• High costs.
• Low coolant temperature.
• An ultra-flat landscape is needed.

Towers

Benefits:

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

Disadvantages:

• High price.
• Low prevalence.

Solar concentrators with linear Fresnel reflectors

Benefits:

• Low energy cost.
• Simple design.