Solar heating for the home. Solar heating: how effective? Choosing the Right Solar Heating System

08.03.2020

Born by Chaos, the ruler of the universe Ra, the luminous guardian of the heavenly firmament Surya, the firmament of Helios circling the chariot, Yarilo, frantic in his passions - all the ancient peoples of the world revered the Sun, realizing that the heat and light exuded by it are the fundamental principle of life. Modern civilization is trying to find ways to use the clean and endless energy of the daylight for the next million years, getting rid of the need to burn hydrocarbons. solar heating- one of the stages of this path to universal prosperity.

Types of solar heating

The methods used today for using solar energy to heat a home (and not only) can be divided into passive and active. Passive heating of the house by the sun provides direct heating interior spaces due to infrared radiation. Active is based on the receipt of thermal or electrical energy in special installations, often located outside the building, its subsequent transformation and distribution for heating needs. The most effective solar heating of the house, where both passive and active methods.

Let the sun into the house - passive heating methods

Windows - to the south

It seems that everyone should understand that by placing the main part of the windows on the sunny side of the house, we will let in not only light, but also heat into the premises. However, driving through our cottage villages, you can see that a good half of the developers do not adhere to the rational principle "the house is to the northern part of the site, and the windows are to the south." But in vain.

Huge stained-glass windows of the Eagle Ridge Residence (USA) energy-saving design are open to the south and west sides, letting in maximum warmth and light into the house. From the north, the building is bounded by a blank, well-insulated wall.

In winter, the low-lying sun penetrates the premises to their full depth, and in summer, when it shone at its zenith, a visor protruding more than two meters from the glass facade protects from overheating

Trombe wall

In the 40s of the last century, the American engineer Tromb came up with a "solar stove". On the south side of the house there is a massive wall made of heat-intensive material (concrete, stone, solid brick), painted black. There are holes in the bottom and top of this heat accumulator. Outside a short distance from the wall - stained glass window. The sun heats the concrete warm air tends to rise up, goes into the room, and the cold one enters the space between the stone and the glass from below. A stable circulation of warm air is formed in the room. Thanks to the invention of selective coatings for glass and stone (concrete), the effectiveness of the Trombe wall in the modern version has become noticeably higher.

The principle of operation of the Trombe wall. A nice bonus: it can be used not only in winter for indirect heating of the house (in the figure on the right), but also in summer for ventilation (left)

Logical development of the Trombe wall. It is a hollow flat box (panel), placed obliquely for better radiation trapping. The upper railing of the panel is transparent for infrared radiation, and a partition separates it along it. Painted black, the partition heats up, warm air rises and enters the room. Unheated air from the room penetrates into the lower, cold part of the collector.

The passive air solar collector is the simplest device. Do-it-yourself solar heating is within the power of any economic peasant

Solar greenhouse - fresh vegetables as a bonus

Solar greenhouse attached to the house. To “let in” more sun into the house, you need to increase the area of \u200b\u200bwindows. It is problematic to make the entire southern wall glass in a cold climate, the heat loss will be too high. Separating part of the building with glass walls and a roof from the main premises of the house, we get a solar greenhouse. It almost does not interfere with the penetration of infrared radiation into the windows of the house, in addition to this it will heat up outer wall inside the greenhouse. On a bright winter sunny day, the air in the solar greenhouse can warm up to a temperature significantly higher than in the house.

On a sunny day, the solar greenhouse can overheat, which is a problem for summer time. It is necessary to organize ventilation or shade the stained-glass windows.

To maximize the use of the heat received by the greenhouse, it is possible to organize air exchange with living quarters.

The greenhouse of a solar house in Winchester (USA) is separated from the main part of the house by a massive heat-storing wall with opening ventilation holes. Such a solution is a combination of a solar greenhouse and a Trombe wall. Water canisters installed in the greenhouse help to keep warm longer

The natural air exchange between the greenhouse and the house is rather weak and, in order to use the energy to the maximum, the air movement is forced.

Air exchange between the main part of this house in Hamptden (USA) and the attached greenhouse is organized through an underground space, warm air enters the premises from below, and cooled air enters the greenhouse from above. The circulation of air flows is provided by a fan, automatics turns it on and off at the right time. In practice, this is already solar heating of a private active-type house

An additional bonus that the solar greenhouse gives to its owners: almost all year round you can grow vegetables in it or leave citrus fruits for the winter. True, this will require solving the problems of ventilation, humidity, daytime overheating and nighttime frosts.

Active heating - sunlight is collected by vacuum collectors

Air solar collector

An air solar collector, equipped with a system of forced transmission and distribution of energy, is able to provide much more heat compared to a passive variant. The air circulation rate is automatically adjusted depending on the temperature in the house and the degree of heating of the collector. The air heated in the collectors can enter the ventilation system or the premises directly. If its temperature is high enough, it can also be used to heat the heat transfer fluid. Excess daytime energy is stored overnight in heat accumulators.

Solar air heating based on a solar collector. From the hollow panel (1) through the air channels (6), the fan drives the air into Utility room, where the automation, depending on the situation, distributes it to the air preparation unit (3) or a massive heat accumulator (2). At the same time, the hot water coil (5) can also heat up. During the day, when the rooms need heating, the system operates in mode B, warm air from the collector is sent to the rooms. When the required temperature in the house is reached, the air flow is redirected to the heat accumulator, mode A. At night, when the collector does not provide heat, the damper closes the channel leading to it, circulation is carried out between the heat accumulator and the premises.

Vacuum solar collector

The most advanced device for solar heating today.

circuit diagram vacuum solar collector. The liquid absorber circulating through the U-shaped tubes, when heated, evaporates and rises up into the collector. The latter is connected to the circuit of the heating system and, in turn, the liquid coolant circulates through it. The absorber gives energy to the coolant, cools down, condenses, goes down. The cycle repeats

solar heating country house based on vacuum collectors is much more efficient than other solar systems, however, in addition to the uneven heat generation traditional for solar systems, it has three more significant drawbacks: in severe frost, heat transfer drops sharply, installations are fragile and expensive.

Vacuum solar collectors should be installed in such a way that they are protected from vandals. This is especially true for our country, getting a pebble into a glass tube is a sweet thing.

Vacuum panels are not connected directly to the heating system. At a minimum, buffer tanks are needed to smooth out uneven heat generation.

The "correct" scheme for connecting a vacuum solar collector to the heating system. Heat is not transferred directly, but through a heat exchanger, daytime excess heat is stored in a heat accumulator (buffer tank) for the night. Please note that the diagram shows a "normal" heating boiler, the solar system only complements it

Electric solar panels can only be used indirectly for heating. It is unreasonable to spend electricity on space heating directly, it can be used more rationally. For example, send fans and automation of active solar systems to work.

Why solar plants are not visible on the roofs of our houses

The Internet is replete with promotional materials with beautiful pictures that tell about the extraordinary benefits of solar systems. Craftsmen post videos on youtube on the topic “heating from the sun with their own hands” about their own know-how, collected on their knees from improvised materials. The web is swollen with rave articles reposting about the miraculous benefits of solar heating. However, how many houses with solar collectors on the roof appeared behind last years near your home? No one? What are the reasons for the heating solar energy does not find recognition in our area?

Unfortunately, solar energy for home heating does not come when and where it is needed. It is cold closer to the poles, in winter and at night. And the maximum solar radiation falls on the equatorial regions, in the summer and during the day. Heat accumulators at the very least help to smooth out daily, but not seasonal fluctuations.

Map of the intensity of the distribution of sunlight over the territory of Russia. In the Western part of the country, where the lion's share of the population lives, there is little sun. And in eastern Siberia, where the proportion of radiation is noticeably higher, it is cold, which makes it difficult to use active systems. By the way, solar panels that generate electricity are not so sensitive to severe frosts. Quite powerful solar power plants have already been built and are successfully operating in cold but sunny Yakutia.

Passive heating with solar energy is inefficient and is not able to seriously heat the house in the conditions of the Russian winter. "Windows - to the south" - really useful method design, costless, but helping to optimize heating costs. But once relatively popular in the United States, solar greenhouses, Trombe walls and their derivatives gradually faded away even in their homeland.

Active solar heating systems for a private house are very expensive, a lot of money will have to be paid for equipment. Operation, contrary to some statements, is by no means free: electricity is consumed, maintenance of equipment is required. At current prices, compared not only with cheap natural gas, but even with rather expensive pellets, diesel fuel, the installation of a vacuum solar collector in the vast majority of the territory of the Russian Federation will never pay off at all, the payback period exceeds the life of the equipment. Only in some southern regions of the country, solar heating systems for a private house may not be unprofitable under certain conditions.

Scientific station on Olkhon Island (Russia). Using vacuum manifolds (on the right on the roof) for cooking hot water and solar panels (left) for generating electricity makes sense, because there are no central communications on this rocky Baikal island. However, for full-fledged heating in the climate of Buryatia, solar systems are not enough, “normal” stoves heat the house, the fuel for which is imported from the “mainland”, because it is impossible to harass the local forest for firewood

How are things in Europe?

Why, when traveling through Western Europe, do we see (although not so often) solar collectors on the roofs of houses? There are several reasons for this: the high cost of traditional fuels, mild climate, more sunny days. It is no coincidence that solar heating is as uncommon in overcast Britain as it is here. And, most importantly, in those countries where the solar heating system is a practical reality, there are support programs, up to half of the cost of the equipment is paid by the state. Hand on heart, solar collectors are of little use for heating, they are mainly used for preparing hot water, in sunny weather in summer it is really possible to fully meet the needs of hot water supply. By the way, mostly on the roofs of houses you can see solar panels that generate electricity. It is more profitable to produce electricity, and uneven generation is not a problem, because at any time of the day the central power grids buy electricity received in a private house. Moreover, the payment is at an increased rate. Again, the equipment requires almost no maintenance and repair. Today we can safely say that on a global scale, solar energy, although it is not yet a competitor to the traditional one, has a great future. As for the prospects for solar heating, the situation is unclear. Existing systems have already exhausted their potential, new approaches are not yet in sight, and the cost of traditional fuels is falling, which reduces the attractiveness of solar heating systems.

"Sunny Roofs" of Bavaria. All the panels that we see in the photo are electric, rational Germans do not consider solar heating to be particularly profitable, even if the state takes on half the cost of installing solar systems

For those readers who are keenly interested in the topic of using solar energy for life support at home, we recommend that they critically perceive promotional materials and contact professional practitioners, preferably with experience in installing and operating solar installations.

Video: do-it-yourself solar air heating

Is it possible to provide your home with solar thermal energy? Today we will discuss the prospect of using solar systems as the main source of heating, consider the issue of economic feasibility and efficiency of solar collectors.

The main components of the heating system

The heating source of the solar system is solar collectors, the purpose of which is the most efficient transfer of energy from the infrared spectrum of solar radiation to the heat carrier. The thermal range of sunlight is 40-45% of the total radiant flux, in specific figures it is 200-500 W / m 2, depending on latitude, time of year and day.

In principle, collectors alone are enough to build the simplest solar system. Through their channels, ordinary water used for household needs and heating of housing can circulate. However, this approach is not effective enough for a number of reasons, the first of which is the lack of replenishment of energy losses for a full day. Therefore, one of the most important elements of the solar heating system is a heat accumulator - a container with water.

The scheme of heating the house with solar collectors: 1 - cold water supply; 2 - heat exchanger; 3 - heat accumulator; 4 - temperature sensor; 5 - coolant circuit; 6 - pumping station; 7 - controller; 8 - expansion tank; 9 - hot water; 10 - three-way valve; 11 - solar collector

Also a limitation is technical device solar collector. Its channels have a rather small flow area, due to which there is a risk of clogging with mechanical impurities. There is also a high probability of freezing of the coolant at night, while the upper limit of the operating temperature range is 200-300 °C. The collectors are designed for fast continuous circulation of the coolant, which enters at a low temperature, is quickly heated by sunlight and just as quickly gives off heat to the battery.

Tubes of the vacuum U-shaped solar collector

For these reasons, for direct heating in heat pipes, it is customary to use propylene glycol with a set of special additives. So, the third obligatory element of a solar heating system is a special coolant and an exchange circuit, which is often structurally included in the heat accumulator, or may be part of the collector itself.

Varieties and differences of collectors

If you do not go into the technical details of the device, the main difference between flat and vacuum collectors lies in the expediency of their use in different climatic zones. Flat collectors are best used in southern latitudes with prevailing temperatures above zero, vacuum - closer to the north.

The design of a flat solar collector: 1 - coolant outlet; 2 - collector frame; 3 - structured hail-resistant glass; 4 - absorber; 5 - copper tubes; 6 - thermal insulation; 7 - coolant inlet

The expediency of using certain types of solar collectors is due to a number of features:

the inability of vacuum collectors to independently clear snow;
high heat losses of flat solar collectors, growing together with the temperature difference;
low resistance of flat collectors to wind loads;
high cost of the project on vacuum solar collectors;
low temperature range effective application flat collectors.

Vacuum collector design with indirect heat transfer: 1 - cooled coolant inlet; 2 - heat exchanger (collector); 3 - sealed plug; 4 - vacuum tube; 5 - aluminum plate (absorber); 6 - heat pipe; 7 - working fluid; 8 - output of the heated coolant; 9 - heat sink housing; 10 - heat pipe capacitor; 11 - insulation

One of the most important differences lies in the installation process. Flat-plate collectors require delivery to the roof in assembled form, while vacuum collectors can be assembled on site. Also, flat-plate collectors usually do not have their own heat storage and exchange circuit.

Problems of solar energy

Heating solar systems are not without disadvantages, the most important of which is the inconstancy of the energy source. At night, the system does not heat up, and in prolonged overcast weather, expecting clear skies to heat the house is below average pleasure. If the battery, with a sufficiently large volume, is able to maintain the required amount of heat at least until the morning, then several days of battery life in low light conditions can only be expected with a significant expansion of the solar farm. This, in turn, causes the opposite problem: when reaching the maximum power mode (for example, on a clear spring day), such a solar system will require more intensive heat removal or temporary shutdown of several absorbers with their shading.

It is important to understand that solar systems in the realities of the Russian climate cannot be used as the only or main source of heating. However, they can significantly reduce energy consumption during the heating season. Hybrid collectors work especially effectively, in which the heaters are combined with photocells. If the cloudiness delays most of the IR radiation, then the losses of the photoelectric part of the spectrum are not so significant.

Another disadvantage of solar collectors lies in the need for forced circulation of the coolant in the collector-accumulator system. Some vacuum collectors are equipped with a tank designed for natural circulation and located above the absorber. Such installations are usually used in hot water supply systems with cold water intake under pressure. But there are still ways to establish joint work of such solar collectors with a heating system.

Integration into the heating system

There are two ways to combine solar collectors with an arbitrarily complex liquid heating system. The main source of energy can be either gas or electricity - there is no significant difference.

The first option is to heat the common daily battery. The accumulator is connected to the boiler jointly and sequentially; if the temperature is not high enough, the latter is put into operation and heats up the liquid. A properly designed system of this kind can work effectively even without forced circulation.

1 - heating circuit; 2 - heating fluid; 3 - temperature sensor; 4 - pumping station; 5 - controller; 6 - pump; 7 - expansion tank; 8 - sanitary water; nine - cold water; 10 - hot water supply; 11 - solar collector; 12 - heating boiler

The second type of combination involves the use of a heat accumulator with two circuits. Through one, heat is removed from the collector, through the second, the coolant in the system is heated, water from the accumulator serves as a source of hot water. Since the circuits are isolated from each other, warmer liquids or antifreeze can be used in the heating system and the heat exchange cycle from the solar collector. The main disadvantage is the volatility of the system, because in both circuits the circulation is forced.

1 - cold water supply; 2 - temperature sensor; 3 - solar collector heat exchanger; 4 - boiler heat exchanger; 5 - collector coolant circuit; 6 - pumping station; 7 - controller; 8 - expansion tank; 9 - circulation pump; 10 - hot water outlet; 11 - heating boiler; 12 - solar collector

Power calculation and installation steps

The transition to solar energy does not accept haste and a superficial approach. Often, conclusions about the expediency of installing a solar system can be made only after several years of observations and calculations.

Unfortunately, relying on solar maps does not special meaning, because local weather conditions can greatly distort the average. Therefore, the first thing to do is to independently compile a report on the intensity of solar radiation at the installation site of the collectors. Pyranometers are used for measurements; within 5 thousand rubles, you can purchase a budget device with a sufficient set of functions.

Measurements should be carried out at different times of the day with a frequency of about a week throughout the year. In the course of measurements it is necessary to take into account the angle of inclination and the orientation of the collectors. The data obtained are finally compared with the statistics of the hydrometeorological center on the percentage of cloudy days in a year.

In order to ensure high efficiency of the solar plant, the most negative scenario should be considered, that is, the longest period with the lowest illumination should be taken as a starting point. Ideally, you can make an adjustment for the likelihood of even worse weather conditions using meteorological statistics for the last 15-20 years. The obtained data on the incoming solar energy will help to determine the required total area of the absorption field and determine the number of collectors that need to be purchased.

As mentioned, collectors are very rarely used as the main source of heating, usually they play an auxiliary role. But the share of participation can be calculated, it is indicated as a percentage of the total power of the house's energy system or its heat loss. Having received the required number of kilowatts, it is multiplied by the optical efficiency of the absorbers, several coefficients are added - corrections for orientation, inclination, temperature regime, as well as a margin of safety.

Based on the "net" value of the generated power, the following is selected:

the required number of collectors of a certain model and, on average, one backup solar collector per 10-15 in operation;
piping system with manufacturer's recommended capacity and heat resistance;
circulation group, shut-off valves, other auxiliary devices;
volume and location of the battery tank. In systems with a daily storage or a heat extraction power of more than 20 kW, it makes sense to build insulated concrete tanks with a volume of 15-20 m3.

For independent installation and maintenance, it is necessary to draw up a system project, allocate space for auxiliary devices and fix the solar collector on the southern (for the northern hemisphere) slope of the roof, taking into account the recommendations of the equipment supplier regarding wind loads. Do not forget that by purchasing a full range of equipment from one distributor, you get the opportunity to compile for free, if not a design of a solar heating system, then at least a list of well-compatible equipment and components.

Is a heat pump necessary?

One of the main disadvantages of solar heating systems is the high cost. While flat-plate collector technology is well established, vacuum absorbers remain expensive and, under certain weather conditions, are the only ones that can be successfully operated. But there is another alternative - air-type collectors.

In view of more simple device their cost is less, plus there is the possibility of battery life. The efficiency of the air collectors is increased with the installation of a blower fan powered by the built-in solar panel. Due to the accelerated, but proportional to the heating, cooling of the channels, the return heat losses through the collector are minimized. Power limitation can be achieved by controlling the fan speed or by simply blocking the flow - air collectors are not afraid of thermal shock, and it is also easy to set up natural recirculation.

The lack of air systems in a small degree of heating of the coolant. The heat capacity of air is less, plus the absorber is almost always heated without focusing. To be able to integrate into heating system(which is most often necessary due to the impossibility of laying a ventilation duct in a heated room) a heat pump or a split system is really needed.

But air heat pumps can also be used to increase the efficiency of air conditioning. With them, the circulation rate can be raised to values that are not acceptable in household ventilation systems, which gives a 2-3-fold increase in output due to the high temperature difference. During the night, the collector will also have a small share of output over the operating temperature range.

The air used as a heat carrier can be dried or replaced with carbon dioxide or another more heat-intensive gas. However, it makes no sense to use heat pumps with a water primary circuit: they are initially designed to work with a high temperature difference, and therefore the increase in power is not enough to justify the installation cost.

The cost of a solar heating installation

For the pleasure of using clean energy in general, you have to pay quite a lot, at least for today. To be fair, there is also positive news: over the past five years, the cost of manufacturing flat-plate collectors has fallen by 2-2.5 times, the same can be expected soon from devices with vacuum absorbers.

The cost of flat and vacuum collectors is determined by the volume of production - the value of solar radiation in ideal lighting conditions, that is, power density. On average for 1 kW of solar collectors flat type you will have to pay about $350-500, and for a complete installation with an external battery - about $800-1000. The cost of vacuum solar collectors fluctuates in a higher range - from $600 to $1000-1200 per complex, depending on the quality of workmanship, tube material, heat exchanger insulation and other features.

For capacitive collectors, the measurement standard is in liters of water heated to the highest possible temperature. You can calculate the amount of electricity generated by either total area absorber, or by expressing it in terms of the specific heat capacity of water. Depending on the complexity of the system, the cost varies greatly, the price of one of the examples from the middle market segment reaches $1,500 per 300 liters (for 4-5 residents) with a temperature difference of about 50 °C, which is equivalent to 2.5 kW of specific power.

In most regions of Russia, huge amounts are spent on heating residential buildings. This forces homeowners to look for additional opportunities in this area. The energy of solar radiation is environmentally friendly and free heat. Applying modern technologies, you can use solar energy for space heating in the regions of central and southern Russia.

Possibilities of modern technologies

The surface of the earth receives a different amount of solar energy, it all depends on the location of the territory relative to the equator and the season. For example, in the Arctic, the sun is much less than in the equatorial part. In addition, solar radiation is more intense in summer than in winter period. When calculating the average values, experts determined that in one hour square meter Earth's surface receives about 160 watts of solar energy. Modern systems are highly productive, making it possible to use the energy of solar radiation almost anywhere.

To receive maximum efficiency When using solar energy, two methods are used:

Direct heating of thermal collectors. Direct sunlight heats the thermal collectors, which in turn transfer heat to the liquid in the heating circuit and hot water system. Thermal collectors can be of open and closed type, they can have a flat or spherical shape. thermal energy obtained from the collectors can be used to heat the working medium in the water supply system and the coolant in the heating system.
The use of solar panels. In this case, the solar energy is converted into electricity, which is subsequently transmitted to the consumer through a special system.

The development of solutions for the collection, accumulation and use of solar energy is progressing quite rapidly. However, there are many positives and negatives in this area.

Advantages and disadvantages of using solar collectors and batteries

The main advantage in using solar heating systems is the general availability. In second place is the absence of emissions. Solar energy is considered the most environmentally friendly and natural form of energy.

In addition, the operation of solar panels and collectors is quiet, and the location on the roof of the building saves usable space.

The main inconvenience in the use of solar energy for the home, consumers experience from intermittent lighting. For example, at night there is no possibility of collecting energy, and in winter time when required a large number of warm, daylight hours are short.

In addition, it is necessary to constantly monitor the cleanliness of the panels so as not to reduce the efficiency. It should also be noted that depreciation of equipment, work circulation pump and control electronics requires constant costs.

Solar collectors of open type

The design of open solar collectors is made in the form of a system of tubes, unprotected from external influences. Inside this system, a coolant circulates, which is heated directly from the sun's rays. The tubes are fixed on the carrier panel in the form of a snake or with parallel stacking of rows and exit to the branch pipe. The tubes can be filled with water, gas, air or antifreeze.

The simple design and lack of insulation makes open collectors affordable for almost all consumers. In addition, home craftsmen have the opportunity to make solar heating of a private house with their own hands.

The lack of insulation on the tubes of the system does not allow to store the received solar energy, therefore, such systems have a very low efficiency. Their main use is for heating water in swimming pools and showers in summer time. Most often, open-type collectors are used by residents of warm and sunny regions, where the temperature of the air and heated water does not have significant differences. The highest efficiency of work was noted in sunny weather in the absence of wind.

Solar collectors of tubular type

To assemble a tubular solar collector, separate tubes filled with water, gas or steam are used. This design is one of the types of open solar systems, but with a more coolant, more protected from negative impact external factors. This includes vacuum installations, arranged according to the principle of a thermos.

In a tubular solar collector, the tubes are arranged in parallel with individual connections to the overall system. This allows you to replace a failed tube with a new element without compromising the operation of the entire structure. In addition, the system can be assembled directly on the roof of the building, which greatly simplifies the installation process.

The main advantage of a tubular solar collector is the cylindrical shape of the main elements. Thanks to this, solar energy is collected throughout the daylight hours, and this does not require the installation of additional devices that monitor the movement of the sun.

Depending on the design features, solar collectors are divided into two types: feather and coaxial.

Tubes of coaxial type have some resemblance to a conventional thermos. Their design consists of two flasks with air pumped out between them. The surface inside the first flask is coated with a highly selective substance that is able to absorb solar energy to the maximum. It is this layer that serves as a kind of conductor of thermal energy to the internal heat exchanger, consisting of aluminum plates. However, this stage is characterized by a large number of unwanted heat losses.

Feather-type tubes are made of glass and have a cylindrical shape, inside glass cylinder the feather absorber is located. The absence of air inside the tube significantly increases the thermal insulation characteristics. The amount of heat transferred from the absorber is practically not reduced, therefore, the efficiency of such collectors is much higher.

Heat transfer is carried out by a direct-flow system and by means of a thermotube.

A thermotube is a sealed container, inside of which an evaporating liquid is poured, which is most often water under low pressure. Heated from the inner walls of the container or feather absorber, the liquid boils, and its vapors rise up. After the transfer of thermal energy to the coolant of the heating system or hot water supply, the vapor condenses into a liquid, which flows down the walls.

The direct-flow system is a U-shaped tube with a coolant circulating inside.

A cold coolant is located in one half of the tube, and the heated liquid is discharged through the second part. When the temperature rises, the coolant expands, and it enters the storage tank to ensure natural circulation.

The main condition for the location of the thermotube and the direct-flow system is the creation of a certain angle of inclination, which should not be less than 20 degrees.

Direct-flow systems are characterized by the greatest efficiency, since the coolant is directly heated in them.

Advantages and disadvantages of heating systems

Like any system, tubular solar collectors have their pros and cons. The advantages of the system include the following:

Minor heat loss.
Possibility of use at rather low air temperature, up to -30 degrees.
High efficiency throughout the daylight hours.
High performance in regions with a cold and temperate climate.
Low windage, which is explained by the fact that tubular systems pass through themselves the main amount of air masses.
The ability to heat the coolant to a high temperature.
Long service life.

Of the shortcomings of the system, the following attracts special attention:

The system is not capable of clearing snow, ice and frost on its own.
High price level.

As for the high cost, it should be noted here that tubular collectors pay off in a fairly short time.

Closed flat solar collectors

The design of a flat collector is an aluminum frame with a special absorbing layer and a transparent coating. It also includes piping and insulation.

The absorbent layer is blackened copper sheet with excellent thermal conductivity, ideal for building solar systems. The absorber absorbs the energy of solar radiation and transfers it to the coolant, which circulates through the adjacent pipeline.

The outer part of the panel is protected by a transparent coating, for the manufacture of which tempered glass is used, resistant to mechanical damage. This allows you to create reliable protection against hail. The bandwidth of such glass is 0.4-1.8 microns, which is sufficient for maximum solar radiation. The inner side of the panel has a good thermal insulation layer.

Closed flat panels have a number of undeniable advantages:

Simple construction.
High efficiency when used in warm regions.
The presence of a device for changing the angle of the panel, allowing you to choose the optimal location of the structure.
Self-cleaning of frost and snow.
Acceptable cost.
Long service life, high-quality products can last up to half a century.

If the use of the system was included in the design of the building, then in this case, you can get a big benefit.

Of the shortcomings, attention is drawn to the following:

High heat loss.
Quite a large mass of the structure.
High windage of inclined panels.
Low performance with temperature changes up to 40 degrees.

The area of use of flat closed panels for home heating using solar panels is quite wide:

In summer, the systems fully meet the needs for hot water.
Between heating seasons, they are able to replace gas heating appliances and electric heaters.

Comparative characteristics of some types of solar collectors

The main characteristic of any solar collector is its performance. Depending on the design features and the temperature difference, the efficiency of the system is determined. it should be taken into account that the cost of flat-plate collectors is much lower than that of tubular systems.

When choosing a solar collector, you should carefully study the parameters on which the efficiency of solar water heating and the power of the structure depend.

Solar collectors have a number of rather important characteristics:

The ratio of the total and absorbed energy of solar radiation can be determined from the adsorption coefficient.
The ratio of the amount of transferred heat and absorbed energy is determined by the emission factor.
The ratio of the total and aperture area.
Efficiency.

The aperture area should be understood as the working area of the collector. Flat-type systems are characterized by the maximum values of this indicator. The aperture area corresponds to the area of the absorbent layer.

Ways to connect to the heating system

One of the disadvantages of solar collectors is the impossibility of a constant supply of energy. Therefore, when connecting, it is important to choose a system that is capable of operating in a limited mode.

In the regions of central Russia, solar collectors are used as an additional source of heat, as they do not guarantee a constant flow of energy. Connecting solar collectors and batteries to a functioning heating and hot water supply system has some differences that must be taken into account.

Connection of heat collectors

The connection scheme is determined by the direct purpose of the design, most often two options are used:

For heating water in the summer.
For heating the coolant in winter in heating and hot water systems.

The first option is distinguished by its simplicity, its operation is based on the natural movement of the coolant. Therefore, such a scheme for the use of solar energy for a private house can be used without a circulation pump. The principle of operation is as follows: when heated by sunlight, the water in the collector expands and enters the storage tank. A cold liquid is sucked in to replace the outgoing water.

However, it should be borne in mind that for greater efficiency of the system with natural circulation, it is necessary to create a certain angle of inclination. In addition, it is important to place storage tank at a higher level than the solar collector.

To maintain a high temperature of the coolant, the storage tank requires additional thermal insulation.

Maximum effective work solar collector requires the use of a more complex connection scheme.

A non-freezing coolant is poured into the system and a circulation pump is inserted. To control its operation, a controller and temperature sensors are installed. The first sensor shows the temperature of the water in the storage tank, the second sensor is installed on the pipe supplying the hot coolant from the solar collector. This scheme works for following principle: when the water in the tank is heated above the set parameters, the circulation pump is turned off, and the movement of the coolant stops. When the temperature drops to the control values, the controller turns on the heating boiler.

How solar panels are connected

The solar collector connection scheme, in which the energy of solar radiation is accumulated, cannot be used to connect solar panels. In this case, you will have to additionally install an expensive battery pack. Therefore, another option must be used.

Energy from the solar panels is transferred to the charge controller, which is designed to constantly supply energy to the batteries and stabilize the voltage. When electricity is supplied to the inverter D.C. is converted into alternating single-phase current 220 V.

Receipt universal view energy for heating a house from the sun makes solar panels more profitable, but do not forget about the lower efficiency of this system. It should also be noted that the solar collector cannot store energy, as solar panels do.

Power calculation

To profitably use solar collectors, it is important to consider the following recommendations from manufacturers:

The system should provide hot water only by 70%.
No more than 30% of energy can enter the heating system from solar collectors.

Only in this case it is possible to achieve savings in heating and hot water supply costs by almost 40%.

When calculating the power of the collector for heating a house with solar energy, one should also take into account the location of the system, the angle of the panels and the average annual temperature in the region.

The energy of the sun, which gives us light, electricity, heat, is rapidly gaining more and more frontiers. Nobody surprises anymore various devices and solar-powered devices, home helium power plants, various lamps, street garlands, traffic lights powered by sunlight.

And of course, the logical direction of using solar energy was to use it for heating, heating water not only in a single private house, but also in large houses, in public buildings.

Of course, solar systems are not able to provide round-the-clock operation for heating water. But they are able to replace traditional fossil energy sources - oil, gas, coal - during daylight hours. Since solar heating does not require the consumption of raw materials, there are no harmful emissions into the atmosphere, no environmental pollution.

Therefore, the use of solar energy for heating residential buildings, hot water supply will become increasingly important every year against the background of the expected rise in prices for oil, gas, coal.

Solar heating system

In the simplest case solar system heating consists of one or more solar collectors connected in a closed circuit with heating fittings - batteries or pipes laid in the floor. In this case, the batteries or floor pipes must be above the collectors.

Then the water heated in the collectors, according to the laws of convection, will rise to the heating sections, and the cold water will descend to the collectors. Batteries or pipes hidden in the floor heat up and thus, without any additional devices, the room is heated.

The simplest scheme of solar heating

But this is the most simple circuit, explaining the principle of building the system. In reality, solar heating at home involves the installation of much more complex system. Before buying solar water heaters or making them yourself, you need to determine what area you need to heat, which home heating system is most suitable for these purposes.

At the same time, it should be taken into account that none of the helium systems will be able to provide round-the-clock operation. To heat the premises at night, it will be necessary to use traditional means of heating, working on one of the fossil energy carriers.

Typical scheme of solar heating and hot water supply

For small house with one or two rooms the system can be used air heating from solar collectors. In such installations, air is used as a heat carrier, which, heated in the collector system, enters the heated room through air ducts. Cooled air from this room enters the collector.

Scheme of solar air heating

As for solar heating systems with a liquid heat carrier, in principle they are all built in the same way. The difference lies in the type of collectors used to heat the coolant.

The standard kit consists of manifolds, a storage tank with two heat exchangers (one connected to the manifolds, the other to an additional heater). The storage tank must be provided with good thermal insulation. The circulation of the coolant and water in the heating system is maintained by the pumping group.

flat collector heating system

The design of a flat collector is so simple that it can be freely made by hand. This device is a box, inside of which an adsorber, pipes with a heat carrier, and thermal insulation are placed. For its manufacture does not require any special materials. All components are quite affordable. These are boards, fiberboard, wooden blocks, roofing iron, polystyrene, copper pipes, tempered glass, sealing materials, heat-resistant black paint.

So well put together homemade device able to heat the coolant in stagnation mode up to 150°C. As a rule, water is poured into the system with the addition of antifreeze in such a proportion that this solution does not freeze in winter at night when the solar collector is not working.

Industrial flat collector

The collector or collector batteries are installed in such a way as to provide maximum illumination of them by the sun. As a rule, this is the south side of the roof of the house. The heat carrier circulating in the circuit of the device is supplied by a pump to the heat exchanger located at the bottom of the storage tank. Continuously circulating in this system, the coolant heats the water in the boiler up to 50°C - 60°C, which is quite enough to heat the living quarters.

Flat solar collectors on the roof of a hotel and a private house

To ensure a continuous supply of heat to residential premises at night, a backup water heating system is installed that runs on traditional energy sources - gas, electricity, coal, wood. The coolant circulating in the backup system enters the heat exchanger located above the main one.

This ensures the heating of water in the boiler and a continuous heating cycle. If the backup heating system, working on coal and wood, can only be started manually, then gas and electrical system can be switched on automatically, under the control of a special control unit.

Heating system with vacuum manifold

This system differs from the previous one only in the design of the collector. In this device, vacuum tubes are used to heat the coolant. In essence, these vacuum tubes are a modified Dewar.

A double glass tube in which air is evacuated from the interstitial space. This ensures reliable thermal insulation of the inner tube. The inner tube contains an adsorber and copper pipe, the upper end of which has a slightly larger diameter than the pipe itself, and is sealed. The pipe is first filled with a low-boiling liquid.

Under the influence of solar radiation, the tube heats up, the liquid in it begins to boil, the vapor rises into the tip. There he gives up his heat, returns to the liquid state and flows down according to the laws of convection. This process continues continuously, while heating the tip to 250°C -280°C. Fifteen to twenty such tubes are mounted in a single structure - a collector. The tips are inserted into the pipe through which the coolant circulates. The heat carrier is heated up to 60°С - 80°С and fed into the boiler heat exchanger.

Diagram of a vacuum tube

The vacuum manifold itself is installed obliquely to ensure free circulation of fluid in copper pipes. With the exception of the collector, this heating system is no different from a flat-plate collector system.

Vacuum collectors on the roof of the house

Heating system with parabolic trough mirror

Such a device is the most bulky and difficult to operate design. This is a long (several meters) mirror, curved into a parabola. You can make such a mirror yourself by bending, for example, a sheet of plywood and pasting it on the inside with aluminum foil.

Such a parabolic-cylindrical mirror is mounted on a stable frame. A long pipe is installed at the focus of the mirror, through which the coolant circulates. If the focus of the mirror is correctly determined and the pipe is installed in this focus, the temperature along the heating line of the pipe can reach 250°C - 300°C. But this is subject to the correct installation and orientation of the mirror to the sun.

Parabolic cylindrical mirror collector

The last condition is very important, since if the mirror is not properly oriented, the heating power is lost, and the temperature on the pipe drops significantly. To prevent this from happening, the installation with a parabolic trough mirror must be equipped with a tracking device with an actuator.

The tracking device will track the position of the sun and orient the mirror in the vertical and horizontal planes accordingly. This greatly complicates and, consequently, increases the cost of the design.

If, in addition to solar collectors, a set of solar panels is also installed to supply the house with electricity, then as a result, you can get an absolutely autonomous energy supply for the house, which does not depend on the general power supply networks.

Vacuum collectors and helium photovoltaic cells

The sun will supply the house with electricity and heat, and at night the electricity accumulated during daylight hours will heat the water in the backup heating system. The control unit will monitor the timely switching on and off of the necessary devices, regulate the temperature inside the premises. And it's not a distant future. This is already working.

The use of "green" energy supplied by natural elements can significantly reduce utility costs. For example, by arranging solar heating of a private house, you will supply virtually free heat carrier low temperature radiators and underfloor heating systems. Agree, this is already saving.

You will learn everything about “green technologies” from our article. With our help, you can easily understand the types of solar installations, how they are constructed and the specifics of operation. Surely you will be interested in one of the popular options that are intensively working in the world, but not yet very popular with us.

In the review presented to your attention, the design features of the systems are disassembled, the connection diagrams are described in detail. An example of the calculation of a solar heating circuit to assess the realities of its construction is given. Photo collections and videos are attached to help independent masters.

On average, 1 m 2 of the earth's surface receives 161 watts of solar energy per hour. Of course, at the equator this figure will be many times higher than in the Arctic. In addition, the density of solar radiation depends on the time of year.

In the Moscow region, the intensity of solar radiation in December-January differs from May-July by more than five times. However modern systems so efficient that they can work almost anywhere on earth.