DIY solar air collector: step by step process, how to do it right. DIY solar air collector Air solar collector fiberglass mesh
The usual sources of thermal energy are gradually depleted, simultaneously polluting the environment during combustion. Therefore, humanity pays a lot of attention to renewable solar energy. Naturally, full-fledged, automated systems based on solar power plants are not a cheap pleasure, but a simple solar air collector for a summer cottage or a subsidiary farm can be easily built by yourself. We will talk further about how it works, what it consists of, what is needed to assemble it.
How it works
Going outside on a hot summer day, you can make sure by personal example that the sun's rays not only illuminate everything around, but also have a decent amount of heat, heating the surrounding air. Unlike traditional sources (gas, coal, wood), this energy is unlimited - you just need to take and use it. To do this, you will have to use the elements of different solar plants, for example, an air or vacuum collector. But, as already mentioned above, such mass-produced systems have a complex design and a high enough price to qualify for mass use.
If we analyze them using the example of heating or hot water supply systems, then we must admit that a panel or vacuum solar collector is the same heat exchanger as a general household boiler (gas, fuel oil, coal). That is, its design provides for the possibility of circulation of the coolant (water, air). The latter is heated by visible / infrared radiation absorbed by the outer selective coating (adsorber surface). In serial samples of an air or water collector, a sputtering of black nickel or titanium oxide is used for this. It absorbs the entire spectrum of sunlight - all seven colors of the rainbow, each of which has a supply of internal energy. That is, the main task of the solar installation as a whole, and of the collector in particular, is the maximum absorption of the rays of the visible spectrum and their transformation into heat, which is then transferred to the coolant circulating in the system / housing.
Interesting ! In serial samples of solar collectors, the degree of efficiency of absorption of rays and heat transfer reaches 95%, and in the absence of analysis, they can heat water in the heating system or hot water supply to 200 ° C.
The design and principle of operation of the air apparatus are quite simple: getting inside the solar collector, the air gradually heats up under the influence of sunlight, becomes lighter and rises. The circulation itself in the body of the apparatus can be organized along a natural and forced path. In the first case, the hot air, having given up the heat for its intended purpose, will cool down and sink down, pushing the lighter one warming up. For forced circulation, the ventilation equipment of the solar heat exchanger must be used.
Water or air
The high cost of a solar collector for traditional water heating systems is indirectly related to the properties of the heat carrier used. Water has a high heat capacity, that is, when cooled, it gives off much more heat to the surrounding space than air. But its functioning is associated with a number of problems that should be taken into account during the operation of a system with a solar collector:
- Like any liquid, water practically does not compress, but at the same time it expands with an increase in temperature, which means that pressure must be controlled, especially in closed systems;
- Water changes its state of aggregation, that is, in winter you need to make sure that it does not freeze, destroying the body, pipelines, fittings;
- It contains oxygen, which causes pipe corrosion, which means you have to take care of additional protection.
The heat capacity of air is 4 times lower than that of water. Calculations show that for the same volume, the air collector releases up to 8 kcal of heat into the environment, compared to 300 kcal for the water collector. But this also means that four times less heat is needed to heat a cubic meter of air. The gaseous medium has excellent mobility, allowing you to establish natural circulation in the body of the device and the system, it is not toxic, cannot freeze or boil, and, most importantly, there is a lot of air around. Its use in heating systems does not require a lot of special engineering solutions.
From this we can conclude that the air manifold has a simpler design and operation procedure. He is not so whimsical in terms of operation. Plus, it's easy to DIY.
Design features
Naturally, there are a lot of technical solutions, but in general, the device, design, scheme of action of the air solar collector can be depicted as follows:
It follows from the illustration that its main parts are:
- Hermetically sealed housing. Serves for the convenience of system installation and placement of the main operating components of the solar air collector;
- Adsorber / absorber. Typically, this is a ribbed panel located inside the enclosure. Its main task is to absorb sunlight with subsequent heat transfer to the air that circulates in the collector. For this, the outer side of the adsorber must be black with a matte structure (in this case, the reflectivity will be lower). The material is usually aluminum or copper, which have high thermal conductivity. The ribs are mainly used in the design to increase the heat transfer area, to ensure the required mode of air flow movement inside the case;
- External insulation. This is a transparent material (tempered glass), the main task of which is to protect the adsorber of the solar air collector from mechanical damage and to ensure maximum transmission capacity for the rays;
- Thermal insulation. A layer of material located between the adsorber and the housing wall. Eliminates heat loss when circulating air flow to the environment.
When installed, the air manifold is directed southward, tilted towards the horizon. This is done to ensure maximum surface loading of the absorber during the day and season. The influence of the orientation of the installation site in space on the degree of insolation (duration and area of incidence of sunlight) can be estimated in the following illustration.
The pie chart on the left shows the degree / intensity of the flow of sunlight, and the layout on the right shows the efficiency of the air collectors depending on the orientation of the walls relative to the cardinal points.
It should also be borne in mind that the entire structure in the case must be located as close as possible to the heating object, otherwise heat loss in the air line of the system will negate the entire effect.
Air heating with beer cans
When the task is to design and assemble an air solar collector with your own hands, the first thing that is taken into account is the maximum simplicity of the final design. The use of materials at hand will speed up the assembly process and make it cheaper, but their properties should not be neglected.
It was already mentioned above that the best option for an adsorber of an air solar unit is copper or aluminum, due to their high heat capacity, but in the retail network such sheet metal has a high cost. You can replace it in the design, as it turns out, with a simple can of beer or Coca-Cola - who said that the adsorber of a solar collector with air circulation should be flat. For their manufacture, a manganese-aluminum alloy is used, and all sizes are standardized and the same.
Interesting ! Having resorted to simple calculations, it turns out that if 64 cans (8x8 square) are laid out on the site and connected to each other, then their area will be equal to the sheet area 1400x670 mm.
In addition to the cans themselves, you will have to make a case for an air solar collector, for which it is advisable to use sheet plywood or chipboard. To ensure sufficient rigidity and strength, the thickness of the solar heat exchanger plates should be approximately 16-20 mm. To cut parts to size, you need to use a circular saw together with a template - so the cutting surface of the boards will turn out to be more even.
Important ! When marking, it is necessary to leave an allowance for a segment and future processing of the order of 3-5 mm per side.
Between themselves, the boards of the air manifold body are fastened with screws or confirmations with a mandatory layer of sealant. If plywood is used, then the entire structure must be treated with a protective varnish or impregnation.
The inner walls of the casing of the air solar heat exchanger are insulated. The easiest way for these purposes is to use tiled polystyrene foam (PPS, EPS), which sits on any adhesive. A roll of aluminum foil is laid on top of them, as a reflective layer. Its joints are glued with aluminized tape.
Banks are attached to each other end-to-end - the bottom is inserted into the neck, which is pre-cut with metal scissors and pressed into the body. Several holes are made in the bottom of the can with a drill to organize air circulation, and when joining, the joints are necessarily treated with a sealant. In order for the assembled columns (8 pieces of 8 cans) to be securely located in a wooden case, guides should be made for them - tube sheets, holes for which are made with core drills.
When the air manifold structure is ready, it should be painted. To do this, you can use automotive matte (this is important!) Paint in spray cans. From the outside, the banks are closed with hardened or plexiglass. It provides a high degree of beam transmission and protection for the ductwork inside the enclosure.
Holes are pre-drilled on the rear wall to ensure air circulation. To give a more aesthetic appearance, the finished structure can be refined, for which you can use cladding from lining or furniture profiles.
Before starting operation, you will also have to think over the operation of the air manifold. It may be that natural circulation will be involved or a fan will have to be installed to force the air to be forced.
Metal sheet to help
Another simple installation option for heating air is a collector, in which ordinary corrugated board plays the role of an absorber. This is a ribbed, wavy sheet, which, like the cans in the previous example, is placed in a wooden case. A layer of insulation, such as mineral wool, is also placed underneath. Transparent glass is attached to the outside. The surface of the sheet will also have to be coated with heat-resistant, matte and always black paint. The advantage of such an air manifold is that there is no need for additional ribbing. In addition, there is no need to use expensive aluminum or copper as a material. Similar to the canned version, circulation modes are used - natural or forced.
Agree, it's a strange spring this season. The sun is shining brightly and it seems warm, but the temperature outside is 8 -11 degrees Celsius. And, nevertheless, I am happy to notice that in my apartment, the bay window of which is located to the south, sunlight penetrating through the glass brings energy and warmth in the rooms. My efforts to exploit the greenhouse effect paid off.
Poltava resident Vitaliy, using the same principle, built his house with a domed roof and heats rooms with solar air collectors. Using the energy of the sun to heat a house, it practically doesn’t need natural gas, coal or firewood.
Vitaly is happy to share his experience and this is what he says: “The main material for the construction of a two-story house is ordinary foam. Anyone can build such housing. The premises on the second floor are heated exclusively by solar-air collectors.
In order for warm air to be drawn into the room faster, I installed ordinary fans such as a computer cooler, which consume only 1 W of electrical energy and are powered by a solar battery. As a result, we do not waste electricity, and most importantly we get heat thanks to solar air collectors.
A solar air heater made with my own hands cost me 500 hryvnia. An autonomous device that works with the energy of the sun does not require additional costs. Six solar air collectors heat the entire second floor of the domed building even in winter. "
Based on the experience of the Poltava innovator, I decided to get acquainted in more detail with the principle of building solar air collectors. Fortunately, there is enough material for this. I note that the designs of such devices may be different, but the principle is the same - a black surface (absorber) absorbs solar heat and gives it to the air.
Air manifold technology and manufacturing
The design is based on the design developed by the famous Ukrainian inventor Yuriy Dudikevich.
While the sun is shining on the manifold, the absorber heats up the cold air from the fans. The already heated air returns to the room - thanks to such ventilation, the temperature in the room gradually rises.
The solar air collector is usually installed on the roof or on the south wall of the house, but for this it is necessary to first make four holes with a diameter of about 10 cm.
Through the lower holes in the wall, cool house air is supplied to the collector, heats up and returns back to the room through the upper holes. Check valves are installed at the outlet of the collector, which block the movement of air when the fans are off.
According to Yuri's calculations, the solar air collector can generate 1.5 kW. h of heat energy per square meter of area. For example, 10 collectors, each with an area of two meters, can provide 30 kW. h on a sunny day. In December, when the outside air temperature reached -6 ° C, the total output heat energy of the collector during a sunny day (7:00) was 6 kW. h, and the efficiency is at least 50%, and in October the efficiency of the device rises to 75%.
It is better to direct warm air from a solar heater under the floor using flat rectangular air ducts 30 cm wide and 5 cm high. They are made of galvanized sheet metal, having previously performed thermal insulation, they have a larger surface area than round pipes, and therefore give off heat better.
To make a solar air heater that can work in winter, you will need a wooden frame with a plywood bottom, insulating and reflective film, a metal sheet, blackened mesh and a sheet of transparent polycarbonate. In addition, two fans are needed, and two non-return valves, which are installed at the outlet of the manifold.
The plywood bottom with a size of 1500x1500 mm must be cut into two parts: 1050x1500 mm and 450x1050 mm (connected by a 20x40 mm bar) and cut four holes for the movement of ventilated air.
An insulating film with heat-reflecting properties is placed in the bottom, then two holes with a diameter of 10 cm are drilled from the bottom for the intake of cold domestic air and two holes on the top for the removal of hot air from the collector. Fans are mounted in the lower holes, with the help of which cold air will be drawn into the collector, and check valves are installed on the upper holes, which block the movement of air when the fans are turned off.
The main element of the collector - the absorber - is a black painted metal sheet.
A metal mesh is nailed to the inside of the absorber, which changes the structure of the air flow generated by the fans, and the whole structure is mounted to the collector frame.
Cold domestic air drawn into the collector moves along the mesh, warms up and becomes temperature homogeneous.
For the collector, two Domovent VKO-100 fans are used, which create an air flow of 200 m3 / h. The power consumption of one fan is 14 W with daily solar gains from 3 kW to the collector. h and above.
To install the air manifold on a vertical wall (preferably from the south side), it is necessary to drill four holes 10 cm in diameter. To reduce heat losses, the absorber is covered with a sheet of transparent polycarbonate, which has a protective film against harmful ultraviolet radiation.
Now, I hope, those who wish can make their own solar air collector to satisfy their own ambitions and to the delight of their family in creating comfortable living conditions in the house.
When it comes to solar collectors, first of all, there are associations with the familiar already flat or vacuum models. The energy of the sun in them is transferred through water or antifreeze, in other words, a liquid heat carrier. Such liquid collectors have already appeared in many homes and have ceased to cause any surprise. But in addition to liquid, there is another type of collector, which is much less common, although in some situations it is no less effective. This is an air solar collector.
Features and Applications
Its main difference from liquid versions lies in the coolant, the role of which is played by ordinary atmospheric air. In fact, such a collector is a flat ribbed panel (often perforated) or a system of pipes made of heat-conducting metal (however, sometimes plastic is also used). In such a collector, the air is heated by direct contact with the metal, and ribbing is necessary to increase heat transfer. The entire system must be reliably thermally insulated. An air collector is placed on the southern wall of the house, and air circulation can be either natural, convective, or forced (using fans).
It works at much lower temperatures than liquid models. So, in the usual solar systems, the temperature on the collectors should be more than 45-50 ° С, for air systems, 25-30 ° С is enough. As a result, heat loss is reduced and overall efficiency is increased. However, since the thermal conductivity of air is rather low, such a collector is used very limitedly.
It is used mainly in drying plants (in agriculture), in air heating systems and in indoor air recovery complexes. That is, such systems cannot be considered as a full-fledged alternative to liquid collectors, but they may well reduce overall utility costs.
Pros and cons
Like any system, solar air collectors have their advantages and disadvantages.
Advantages of air collectors:
- Simplicity of construction;
- Minimum cost;
- Effective in air drying systems.
Their disadvantages include a rather low efficiency, the impossibility of using water for heating and the rather large dimensions of the collectors themselves (due to the small specific heat capacity and low air density).
To increase the efficiency of such systems, they are often integrated into the walls of agricultural buildings even at the design stage.
DIY making
Since the solar air collector has a very simple design, it is not so difficult to make it yourself. For this, the most commonly available materials and improvised means are used (some make such collectors even from aluminum cans). However, it must be remembered that such systems are very dimensional due to the peculiarities of the air coolant, therefore, in order to obtain a tangible effect, it will be necessary to assemble products of considerable size (often for the entire length of the wall).
Downpipe collector
Such a solar heater is best done on the entire wall of the house. In the spring-autumn period, it will help to significantly save on energy resources. Taking into account the dimensions of the device, materials are also selected.
For the frame:
- Board about 30-40 mm thick;
- Moisture-resistant plywood (for the back wall) is about 8-10 mm thick.
For the absorber:
- Downpipes made of aluminum (more convenient - rectangular);
- Thin sheet of aluminum;
- Fastening clamps.
You will also need mineral wool to insulate the back wall of the case and polystyrene foam to insulate the side surfaces.
Such a solar collector is assembled as follows. First of all, a wooden case of given dimensions is made (in the form of an open box), the depth of which is a couple of centimeters greater than the height of the pipe walls. Then the back wall and side surfaces are reliably insulated, and a thin sheet of aluminum is laid on the mineral wool layer, to which the pipes are attached with mounting clamps. For better fixation and air circulation, the pipes must be laid so that on one side of the body they are about 20 cm from the end face. The edges of the pipes must be fixed not with clamps, but with a wooden partition, in which the corresponding cutouts will be made.
Since the inlet and outlet of this collector will be located on the same side, there should be several wooden partitions in the body from the opposite end to delimit the air flows. After assembly, the collector is painted with black paint, and honeycomb polycarbonate can be used as a front panel.
It is worth remembering that the finished product is very heavy, so several people are required to install it. It is located on the south side of the house on stable supports. The collector is connected to the ventilation system of the house through insulated air ducts, and a duct fan is used to deliver air to the rooms.
This is a simpler version of the air manifold. You can do it yourself much faster. In the same way, a wooden box of the required dimensions is made, then a beam of about 40x40 mm is laid along the perimeter of the rear wall, a layer of mineral wool is laid on the bottom. The only thing is that you need to make an outlet in the bottom. Then a sheet of corrugated board with a high rib profile is laid on the beam and painted with black paint (if the sheet itself is of a different color). Further, perforation is made in the corrugated board for the air flow.
The entire structure can also be glazed with polycarbonate to increase the heating temperature of the absorber, but it is necessary to provide an inlet for the intake of cold air. A small fan should be placed at the outlet.
Such a self-made collector gives a less significant increase in temperature (usually on a sunny day, the heating is about 28 ° C relative to the outside air). However, it can significantly improve the indoor climate, as it provides a constant supply of fresh heated air.
Solar air collectors (Fig. 1) are gaining an increasing following. This is a solution that offers good opportunities for a relatively small price to improve the indoor atmosphere. They really deserve to be paid more attention to.
The solar air collector, as applied to private households, has three functions. The first is additional heating of the room. The second is ventilation and air filtration in the room. The third is dehumidification of the room with periodic heating in cold weather.
There are practically no restrictions in the operation of solar air collectors - electricity and gas are not needed, air as a heat carrier does not boil or freeze. There is simply no such thing as “stagnation of the solar system” as in liquid collectors.
Rapid heating of indoor air to the desired temperature is also one of the features of solar air collectors. Despite the fact that air has a 28 times lower thermal conductivity and a 4 times lower specific heat than water, it is mobile as a heat carrier and is well regulated (in terms of temperature and quantity). Air allows for rapid temperature changes and a more even distribution of heat inside rooms. It is fire safe. The heated air can be distributed through the existing ducts of the ventilation system.
Operating principle.
A solar air collector (SVK) is a heat absorber in which air is used as a working medium (heat carrier), and solar radiation is used as a heat source. Cold air enters the duct system, where it is heated in contact with the absorber surface, heated by solar heat, and then enters the heated room.
Solar air collectors are divided into three main groups based on air circulation system: internal circulation / recirculation(cold air intake takes place inside the heated room) (Fig. 2b), external circulation(cold air intake is carried out from the street) (Fig. 2a), combined circulation(cold air intake can be carried out from both sources in turn or simultaneously) (Fig. 2c).
According to the method of organizing the heat flow in the solar air collector, these devices are divided into two types: with natural circulation(passive type) and forced circulation(active type). In the first type, the laws of convection and gravity operate in the organization of air movement, in the second type, air movement is carried out with the help of a fan.
In modern solar air collectors, a miniature photovoltaic (solar) panel is installed, from which a 12V / 12W DC fan is powered. This reduces the fire hazard of the system to zero, compared to a 220V fan powered by a home network.
Device.
Solar air collectors sold on the market in Russia are flat box-shaped devices (similar to flat water collectors), consisting of: an aluminum frame, frontal transparent glass, an absorber (metal plate painted black or dark blue, sometimes corrugated and / or perforated), box ducts, insulation (glass wool or basalt wool slab), plastic back panel, fan, photovoltaic mini-panel, non-return air valve, switch and wire, exhaust unit and fasteners (Fig. 3).
Appointment.
The first function of solar air collectors is space heating. Cold air located in the lower part of the room or outside enters the collector, where it heats up and returns to the room through the upper exhaust unit (Fig. 4).
Simultaneously with the heating of the room when using outside air, the solar air collector performs the second function - ventilation of the room and the supply of fresh air. A filter is installed at the outlet from the collector duct to the room, then even in recirculation mode, you can get the air in the room.
Now let's consider the third function of the solar air collector, for which summer residents and other owners of buildings in which they do not live permanently fell in love with it.
The solar air collector does not allow the rooms to become damp when the heating system is operating periodically. This problem cannot be solved by simply ventilating the premises, since the humidity of the cold air is higher, and its moisture absorption properties are lower. It is enough to look at Mollier's Psychometric Diagram and we will see that when the air collector takes air from the street with a temperature of -10 ° C and a humidity of 70%, it heats the air by 15 ° C-40 ° C, even to a temperature of + 10 ° C, then the humidity of this air decreases to 15%, and the moisture absorption properties of the air supplied to the room increase 7-9 times (Fig. 5).
Accordingly, the SVK protects the house from the appearance of mold, unpleasant odors, freezing and, accordingly, premature destruction of damp structural elements.
This function of the air solar collector is also very relevant for saunas (Fig. 6) and indoor pools (Fig. 7).
It is necessary to mention another function of air solar collectors, which is not very relevant for private households in our latitudes, but still.
In addition to generating heat, the solar air collector can perform barrier and heat protection functions.
In this case, the collector covers the entire surface of the wall or roof. The outer surface of the collector and the building wall form the so-called double-skin façade. In this way, walls, roofs and sloping elements of buildings can be “covered” (Fig. 8).
The outer part of such a facade fulfills, on the one hand, a barrier function (protection of the inner part - that is, the building wall itself from getting wet), on the other, it is a heat-absorbing surface that transmits heat well to its inner side. It is usually made corrugated with fine perforations.
This double-skinned façade is internally divided into vertical sections. The outer surface of the façade is heated by solar heat and transfers this heat to the air between the outer and inner walls. The heated air actively rises up, where it is taken inside the premises to heat the building. Very often, as in conventional solar air collectors, hot air is used in combination with a ventilation system - directly or indirectly. The upward flow of hot air in the cavity of a double-skinned facade simultaneously dries out the building wall and improves its thermal insulation characteristics.
These properties are highly appreciated in countries with cold and / or damp climates. The solar air collector of the "solar wall" type is not so much used for heating or heating the air in the ventilation system as it performs energy-saving functions.
In our country, individual solar air collectors of a small area have become widespread in application to seasonal, periodically visited and therefore not constantly heated objects: summer cottages, baths, garages, workshops, studios, warehouses.
At the end of the text, it is necessary to say a little about the disadvantages of the solar air collector:
- The solar air collector works only in the presence of the sun, its efficiency on cloudy days will be about zero.
- at low temperatures, even on a sunny day, it is better to switch the collector to the internal circulation mode.
- When installing the collector, one or two large holes must be drilled in the load-bearing wall or in the roof (depending on the installation location).
Fig. 9 Examples of different options for attaching collectors to the wall of a house.
However, by using an air solar collector, we can solve the following problems (Fig. 9):
- Ventilation and filtration of indoor air.
- Maintaining a dry atmosphere in rooms in which heating is not constantly working.
- Additional space heating.
Everyone loves to bask in the sun in the summer. But few people know that in winter the sun can warm you just as well. To do this, you only need to correctly apply the energy of the sun. And modern technology allows you to do this.
Air solar collector- the best assistant in this matter. It heats the air passing through it, while working completely autonomously. And most importantly, it does not care about the readings of the thermometer, it is effective even in cold weather, creating comfortable conditions in the room.
How the solar collector works
A photosensitive element with photovoltaic properties starts a fan that draws in air from the street. On the way, the air passes through the filter, thanks to which it is warmed and cleaned. As a result, the room is always dry and warm.
The air manifold allows:
maintain the optimal value of humidity in the room;
get rid of mold and mildew on walls, floors and ceilings;
maintain a comfortable room temperature;
saturate the room with fresh air, and therefore oxygen.
A small panel allows you to maintain a comfortable microclimate in large rooms. Therefore, it is very beneficial to use an air solar collector to heat your home. This significantly saves money on paying bills for centralized power supply.
Pros of solar ventilation and heating:
Such a system works completely autonomously. The fan is switched on from electricity generated by the sun, air circulation takes place without the participation of additional devices.
Solar energy is free, environmentally friendly and available to absolutely everyone.
Heating costs are reduced, and in some cases this even allows you to completely disconnect from the central heating. After the system pays for itself (about 3-4 years), it starts working for free, without spending any resources, except for solar radiation.
Anyone can buy an air solar collector, it does not require serious financial costs.
To maintain the comfortable atmosphere of a one-family house, one small panel is sufficient, installed on the southern wall of the building.
This method of using the energy of the sun has been actively used in Europe for more than a decade. The most advanced countries in the field of solar energy (Germany, France) use air collectors on an industrial scale: to maintain the required air humidity in warehouses with products and in workshops, for ventilation of premises; farmers use technology to create an optimal climate in barns and granaries.
The most popular applications for air collectors in Russia are:
ventilation and heating of private houses;
ventilation of baths and bath rooms;
maintaining the required humidity in conservatories and greenhouses.
Now on the Russian market there is a large selection of air collectors from domestic and foreign manufacturers. A wide model range allows you to choose the system that best meets the individual requirements of each customer, which will work effectively in his conditions.
If you have additional questions about solar heating and hot water supply, please contact the curator of the direction "collectors, heat pumps" Vladimir: t. Mob..soldatov9