How to make a solar collector for DIY heating: a step-by-step guide
The rise in price of traditional energy sources encourages private homeowners to look for alternative options for heating homes and heating water. Agree, the financial component of the issue will play an important role in choosing a heating system.
One of the most promising ways of energy supply is the conversion of solar radiation. To do this, use solar systems. Understanding the principle of their device and the mechanism of operation, making a solar collector for heating with your own hands will not be difficult.
We will tell you about the design features of solar systems, offer a simple assembly diagram and describe the materials that can be used. The stages of work are accompanied by visual photographs, the material is supplemented by video clips on the creation and commissioning of a home-made collector.
The content of the article:
- Principle of work and design features
- Temperature classification
- Hand-made manifold
- Factory Appliance Prices
- Conclusions and useful video on the topic
Principle of work and design features
Modern solar systems - one of types of alternative sources heat generation. They are used as auxiliary heating equipment that processes solar radiation into energy useful to home owners.
They are able to fully provide hot water and heating in the cold season only in the southern regions. And then, if they occupy a sufficiently large area and are installed in open areas not shaded by trees.
Despite the large number of varieties, they work the same way. Any solar system represents a circuit with a sequential arrangement of devices that supply thermal energy and transmit it to the consumer.
In this article, we will consider the second option - a collector solar system.
Collectors are a system of tubes connected in series with the output and input line or laid out in the form of a coil. Industrial water, air flow, or a mixture of water with some non-freezing liquid circulates through the tubes.
Physical phenomena stimulate the circulation: evaporation, changes in pressure and density from the transition from one state of aggregation to another, etc.
The collection and accumulation of solar energy is carried out by absorbers. This is either a solid metal plate with a blackened outer surface, or a system of individual plates attached to the tubes.
For the manufacture of the upper part of the body, the cover, materials with a high ability to transmit light are used. It can be plexiglass, similar polymeric materials, tempered types of traditional glass.
I must say that polymeric materials do not tolerate the influence of ultraviolet rays. All types of plastic have a sufficiently high coefficient of thermal expansion, which often leads to depressurization of the housing. Therefore, the use of such materials for the manufacture of the collector body should be limited.
Water as a heat carrier can be used only in systems designed to supply additional heat in the autumn / spring period. If it is planned to use the solar system year-round before the first cooling, the process water is changed to a mixture of it with antifreeze.
If the solar collector is installed to heat a small building that does not have a connection with the autonomous heating of the cottage or with centralized networks, a simple single-circuit system with a heating device at the beginning of it is built.
The chain does not include circulation pumps and heating devices. The scheme is extremely simple, but it can only work in the sunny summer.
When a collector is included in a two-circuit technical structure, everything is much more complicated, but the range of days suitable for use is significantly increased. The collector processes only one circuit. The predominant load is assigned to the main heating unit, which runs on electricity or any type of fuel.
Despite the direct dependence of the performance of solar devices on the number of sunny days, they are in demand, and the demand for solar devices is steadily increasing. They are popular among craftsmen seeking to direct all types of natural energy into a useful channel.
There are a fairly large number of criteria by which these or those designs of solar systems are classified. However, for appliances that you can do with your own hands and use for hot water supply and heating, the most rational is the separation by type of coolant.
So, systems can be liquid and air. The first type is more often applicable.
In addition, a classification is often used according to the temperature to which the working nodes of the collector can heat up:
- Low temperature. Options that can heat the coolant to 50ºС. They are used for heating water in irrigation containers, in bathrooms and showers in the summer, and to increase comfort in cool spring and autumn evenings.
- Medium temperature. Provide a coolant temperature of 80ºС. They can be used for space heating. These options are most suitable for arranging private homes.
- High temperature. The temperature of the coolant in such installations can reach 200-300ºС. They are used on an industrial scale, are installed to heat production shops, commercial buildings, etc.
In high-temperature solar systems, a rather complex process of transferring thermal energy is used. In addition, they occupy an impressive space, which most of our country life lovers cannot afford.
The manufacturing process is time-consuming, the implementation requires specialized equipment. It is almost impossible to independently make such a variant of the solar system.
Making a solar device with your own hands is an exciting process that brings a lot of benefits. Thanks to him, it is possible to rationally apply free solar radiation, to solve several important economic problems. We will analyze the specifics of creating a flat collector that supplies heated water to the heating system.
The simplest and most affordable material for self-assembly of the solar collector body is a wooden block with a board, plywood, OSB boards or similar options. Alternatively, a steel or aluminum profile with similar sheets can be used. The metal case will cost a little more.
Materials must comply with the requirements for outdoor structures. The life of the solar collector varies from 20 to 30 years.
So, the materials must have a certain set of operational characteristics that will allow the use of the structure throughout the entire period.
If the case is made of wood, then the durability of the material can be achieved by impregnation with water-polymer emulsions and coating with paints and varnishes.
The basic principle that should be followed when designing and assembling a solar collector is the availability of materials in terms of price and ability to purchase. That is, they can either be found in free sale, or made independently from available improvised means.
Nuances of thermal insulation
To prevent thermal energy loss, insulating material is mounted on the bottom of the box. It can be polystyrene or mineral wool. Modern industry produces a fairly extensive range of insulation materials.
To insulate the box, you can use foil insulation options. Thus, it is possible to provide both thermal insulation and reflection of sunlight from the foil surface.
If a rigid plate of polystyrene foam or expanded polystyrene is used as insulation material, grooves can be cut to lay the coil or pipe system.Typically, the collector absorber is laid on top of the insulation and firmly fixed to the bottom of the body in a manner that depends on the material used in the manufacture of the body.
Solar collector heat sink
This is an absorbent element. It is a system of pipes in which the coolant is heated, and parts made most often from sheet copper. The optimal materials for the manufacture of a heat sink are considered copper pipes.
Home craftsmen invented a cheaper option - a spiral heat exchanger from polypropylene pipes.
An interesting budget solution is a solar system absorber from a flexible polymer pipe. Suitable fittings are used to connect to the input and output devices. The selection of improvised means from which the solar collector heat exchanger can be made is quite wide. It can be the heat exchanger of an old refrigerator, polyethylene water pipes, steel panel radiators, etc.
An important criterion for efficiency is the thermal conductivity of the material of which the heat exchanger is made.
For self-production, copper is the best option. It has a thermal conductivity of 394 W / m². For aluminum, this parameter varies from 202 to 236 W / m².
However, the large difference in the thermal conductivity between copper and polypropylene pipes does not mean at all that a heat exchanger with copper pipes will produce hundreds of times large volumes of hot water.
Under equal conditions, the performance of a copper pipe heat exchanger will be 20% more efficient than the performance of metal-plastic options. So heat exchangers made of polymer pipes have the right to life. In addition, such options will be much cheaper.
Regardless of the pipe material, all joints, both welded and threaded, must be airtight. Pipes can be placed both parallel to each other, and in the form of a coil.
The coil type scheme reduces the number of connections - this reduces the likelihood of leaks and provides a more uniform movement of the coolant flow.
The top of the box in which the heat exchanger is located is closed with glass. Alternatively, you can use modern materials, such as acrylic analogue or monolithic polycarbonate. Translucent material may not be smooth, but corrugated or matte.
This treatment reduces the reflectivity of the material. In addition, this material must withstand significant mechanical stress.
In industrial designs of such solar systems, special solar glass is used. Such glass is characterized by a low iron content, which provides less heat loss.
Storage tank or advance tank
As a storage tank, you can use any capacity with a volume of from 20 to 40 liters. A series of somewhat smaller tanks, connected by pipes in a serial chain, will do. It is recommended to insulate the storage tank, as water heated in the sun in a tank without insulation will quickly lose thermal energy.
In fact, the heat carrier in the solar heating system must circulate without accumulation, because the thermal energy received from it must be consumed during the period of receipt.The storage tank rather serves as a distributor of heated water and a ditch chamber, which maintains the pressure stability in the system.
Solar assembly steps
After the manufacture of the collector and the preparation of all the constituent structural elements of the system, you can proceed to direct installation.
Work begins with the installation of an advance chamber, which, as a rule, is placed at the highest possible point: in the attic, a separate tower, a flyover, etc.
During installation, it should be noted that after filling the system with liquid coolant, this part of the structure will have an impressive weight. Therefore, you should verify the reliability of the overlap or strengthen it.
After installing the tank proceed to install the collector. This structural element of the system is located on the south side. The angle of inclination relative to the horizon should be from 35 to 45 degrees.
After installing all the elements, they are tied with pipes, connecting into a single hydraulic system. The tightness of the hydraulic system is an important criterion on which the effective operation of the solar collector depends.
To connect structural elements into a single hydraulic system, pipes with an inch and a half inch diameter are used. A smaller diameter is used to arrange the pressure part of the system.
Under the pressure part of the system is meant the entry of water into the chamber and the withdrawal of the heated coolant into the heating system and hot water supply. The rest is mounted using pipes of larger diameter.
To prevent the loss of thermal energy, pipes must be carefully insulated. For this purpose, you can use polystyrene, basalt wool or foil versions of modern insulating materials. The storage tank and the advance chamber are also subject to the warming procedure.
The simplest and most affordable option for thermal insulation of a storage tank is the construction of a box around it from plywood or boards. The space between the box and the container should be filled with insulation material. This can be slag, a mixture of straw with clay, dry sawdust, etc.
Test before commissioning
After installing all the elements of the system and warming some of the structures, you can begin to fill the system with liquid coolant. The initial filling of the system should be done through the nozzle located in the lower part of the collector.
That is, the filling is carried out from bottom to top. Thanks to such actions, the possible formation of air jams can be avoided.
Water or other liquid coolant enters the chamber. The process of filling the system ends when water begins to pour from the drainage pipe of the fore-chamber.
Using the float valve, you can adjust the optimum fluid level in the fore chamber. After filling the system with coolant, it begins to heat up in the collector.
The process of increasing temperature occurs even in cloudy weather. The heated coolant begins to rise to the top of the storage tank. The process of natural circulation occurs until the temperature of the coolant that enters the radiator is aligned with the temperature of the carrier exiting the collector.
With the flow of water in the hydraulic system, the float valve located in the fore chamber will trigger. Thus, a constant level will be maintained. In this case, cold water entering the system will be located in the lower part of the storage tank. The process of mixing cold and hot water practically does not occur.
In the hydraulic system, it is necessary to provide for the installation of shutoff valves, which will impede the reverse circulation of the coolant from the collector to the reservoir. This occurs when the ambient temperature drops lower than the temperature of the coolant.
Such valves are usually used at night and in the evening.
The connection to the places of consumption of hot water is carried out using standard mixers. Conventional single taps are best avoided. In sunny weather, the water temperature can reach 80 ° C - using such water directly is inconvenient. Thus, the faucets will significantly save hot water.
The performance of such a solar water heater can be improved by adding additional collector sections. The design allows you to mount from two to an unlimited number of pieces.
The basis of such a solar collector for heating and hot water supply is the principle of the greenhouse effect and the so-called thermosiphon effect. The greenhouse effect is used in the design of the heating element.
The sun's rays freely pass through the transparent material of the upper part of the collector and are converted into thermal energy.
Thermal energy is in a confined space due to the tightness of the duct section of the collector. The thermosiphon effect is used in the hydraulic system when the heated coolant rises, while displacing the coolant and forcing it to move into the heating zone.
Solar collector performance
The main criterion that affects the performance of solar systems is the intensity of solar radiation. The amount of potentially useful solar radiation incident on a specific area is called insolation.
The value of insolation at different points of the globe varies over a fairly wide range. To determine the average indicators of this value, there are special tables. They display the average solar insolation for a given region.
In addition to the insolation value, the area and material of the heat exchanger also affect system performance. Another factor affecting system performance is the storage tank capacity. The optimum tank capacity is calculated based on the area of the collector adsorbers.
In the case of a flat collector, this is the total area of pipes that are in the collector box. This value, on average, equals 75 liters of tank volume per one m² of collector tube area. Storage capacity is a kind of thermal battery.
Factory Appliance Prices
The lion's share of the financial cost of building such a system is in the manufacture of collectors. This is not surprising, even in industrial designs of solar systems about 60% of the cost falls on this structural element. Financial costs will depend on the choice of a material.
It should be noted that such a system is not able to heat the room, it will only help to save on costs, helping to heat the water in the heating system.Given the rather high energy costs that are spent on heating the water, a solar collector integrated into the heating system significantly reduces such costs.
For its manufacture, fairly simple and affordable materials are used. In addition, such a design is completely non-volatile and does not require technical maintenance. Maintenance of the system is reduced to periodic inspection and cleaning of the collector glass from contamination.
Additional information on the organization of solar heating in the house is presented in this article.
Conclusions and useful video on the topic
The process of manufacturing an elementary solar collector:
How to assemble and commission the solar system:
Naturally, a self-made solar collector will not be able to compete with industrial models. Using improvised materials, it is quite difficult to achieve the high efficiency that industrial designs have. But financial costs will be much less in comparison with the purchase of ready-made plants.
Nonetheless, homemade solar heating system significantly increase the level of comfort and reduce the cost of energy that is generated by traditional sources.
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