In the last decade, solar energy as an alternative source of energy has been increasingly used for heating and providing buildings with hot water. The main reason is the desire to replace traditional fuels with affordable, environmentally friendly and renewable energy sources.
The conversion of solar energy into heat occurs in solar systems - the design and principle of operation of the module determines the specifics of its application. In this material we will consider the varieties of solar collectors and the principles of their functioning, as well as talk about popular models of solar modules.
The feasibility of using a solar system
Heliosystem - a complex for converting solar radiation energy into heat, which is subsequently transferred to a heat exchanger to heat the heating medium of a heating system or water supply.
The efficiency of the solar thermal installation depends on solar insolation - the amount of energy supplied during one daylight per 1 square meter of surface located at an angle of 90 ° relative to the directivity of the sun's rays. The measured value of the indicator is kW * h / sq.m, the value of the parameter varies depending on the season.
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The solar energy used in everyday life has enormous prospects. The source for its receipt is inexhaustible. The resource itself is renewed and costs absolutely nothing.
According to the type of accumulation and processing of solar energy, devices are divided into two groups. The first includes batteries that generate electricity, the second - collectors that transfer heat to the consumer
Both solar panels and collectors are installed in open, unshaded areas illuminated by the sun for a maximum period of days. Because they are most often located on the roofs
To operate a mini solar power station, in addition to batteries, the number of which is selected based on the required power, you will need a controller, a conventional or hybrid inverter and batteries, the volume of which is calculated at least on the day of operation
To obtain the thermal energy supplied by the solar collector, no complicated technical equipment is needed. The water heated in the tubes of the appliance immediately enters the heating circuit or the hot water tank
Solar collectors according to the type of coolant are divided into water and air. Water supply hot water to the heating system and mixers, air transfer heated air to the air heating systems
Practical and useful in the countryside solar collector can be done with your own hands. In the summer, he will provide the pool with warm water, heats it for sanitary and hygienic purposes, for irrigation of cultivated plants
The disadvantage of both systems is the inability to store the energy received from the sun for a long time. If in the case of batteries it can be stored for 24 hours in a battery, then it must be used immediately with collectors. An insulated storage tank will help maintain heat for some time.
Solar collectors in tandem with batteries
Small solar power station
Rooftop Solar Panels
The easiest way to connect the solar battery
Solar water collector
Air solar collector
Homemade polymer pipe manifold
Thermal insulation tank for hot water
The average level of solar insolation for the region of temperate continental climate is 1000-1200 kWh / sq.m (per year). The amount of sun is a determining parameter for calculating the performance of the solar system.
Using an alternative energy source allows you to heat the house, get hot water without traditional energy costs - exclusively through solar radiation
Installation of a solar heating system is an expensive undertaking. In order for capital expenditures to pay off, an accurate calculation of the system and adherence to installation technology is necessary.
Example. The average solar insolation for Tula in the middle of summer is 4.67 kV / sq.m * day, provided that the system panel is installed at an angle of 50 °. The solar collector capacity of 5 square meters is calculated as follows: 4.67 * 4 = 18.68 kW of heat per day. This volume is enough to heat 500 liters of water from a temperature of 17 ° C to 45 ° C.
As practice shows, when using a solar installation, the owners of the cottage in the summer can completely switch from electric or gas heating to the solar method
Speaking about the feasibility of introducing new technologies, it is important to take into account the technical features of a particular solar collector. Some begin to work at 80 W / sq.m of solar energy, while others are enough - 20 W / sq.m.
Even in a southern climate, the use of a collector system exclusively for heating will not pay off. If the installation will be used exclusively in winter with a shortage of sun, then the cost of equipment will not be covered for 15-20 years.
In order to use the solar complex as efficiently as possible, it must be included in the hot water supply system. Even in winter, a solar collector will allow you to "cut" energy bills for heating water to 40-50%.
According to experts, with domestic use, the solar system pays for itself in about 5 years. With rising prices for electricity and gas, the payback period of the complex will be reduced
In addition to economic benefits, “solar heating” has additional advantages:
- Environmental friendliness. Carbon dioxide emissions are reduced. For a year, 1 square meter of the solar collector prevents 350-730 kg of mining from entering the atmosphere.
- Aesthetics. The space of a compact bathtub or kitchen can be eliminated from bulky boilers or geysers.
- Durability. Manufacturers claim that, subject to installation technology, the complex will last about 25-30 years. Many companies provide a warranty of up to 3 years.
Arguments against the use of solar energy: pronounced seasonality, weather dependence and high initial investment.
General arrangement and principle of operation
Consider a solar system with a collector as the main working element of the system. The appearance of the unit resembles a metal box, the front side of which is made of tempered glass. Inside the box there is a working body - a coil with an absorber.
The heat-absorbing block provides heating of the heat carrier - the circulating liquid, transfers the generated heat to the water supply circuit.
The main components of the solar system: 1 - collector field, 2 - air vent, 3 - distribution station, 4 - pressure relief tank, 5 - controller, 6 - water heater, 7.8 - heating element and heat exchanger, 9 - heat mixing valve, 10 - hot water consumption, 11 - cold water intake, 12 - discharge, T1 / T2 - temperature sensors
The solar collector must work in tandem with a storage tank. Since the coolant is heated to a temperature of 90-130 ° C, it cannot be fed directly to hot water taps or heating radiators. The coolant enters the boiler heat exchanger. The storage tank is often supplemented by an electric heater.
Scheme of work:
- The sun heats the surface of the collector.
- Thermal radiation is transmitted to the absorbing element (absorber), which contains the working fluid.
- The coolant circulating through the tubes of the coil is heated.
- Pumping equipment, a control and monitoring unit provide heat transfer through the pipeline to the coil of the storage tank.
- The heat is transferred to the water in the boiler.
- The cooled coolant flows back to the collector and the cycle repeats.
Heated water from the water heater is supplied to the heating circuit or to the water intake points.
When arranging a heating system or year-round hot water supply, the system is equipped with a source of additional heating (boiler, electric heater). This is a prerequisite for maintaining the set temperature.
Solar panels in the arrangement of private houses are most often used as a backup source of electricity:
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Solar system for power generation
The dependence of power on the used area
Equipment for solar control
Solar Energy Automation
Varieties of solar collectors
Regardless of the purpose, the solar system is equipped with a flat or spherical tubular solar collector. Each of the options has a number of distinctive features in terms of technical characteristics and operational efficiency.
Vacuum - for cold and temperate climates
Structurally, a vacuum solar collector resembles a thermos - narrow tubes with a coolant are placed in larger diameter flasks. A vacuum layer is formed between the vessels, which is responsible for thermal insulation (heat preservation - up to 95%). The tubular shape is most optimal for keeping the vacuum and "occupation" of the sun's rays.
Basic elements of a tubular solar thermal installation: support frame, heat exchanger body, vacuum glass tubes treated with a highly selective coating for intense "absorption" of solar energy
The inner (heat) tube is filled with saline with a low boiling point (24-25 ° C). When heated, the liquid evaporates - the vapor rises up the flask and heats the coolant circulating in the collector body.
In the process of condensation, water droplets flow into the tip of the tube and the process repeats.
Due to the presence of a vacuum layer, the liquid inside the heat bulb is able to boil and evaporate at minus street temperature (up to -35 ° С).
The characteristics of solar modules depend on such criteria:
- tube design - feather, coaxial;
- heat channel device - "Heat pipe"direct-flow circulation.
Feather bulb - a glass tube in which a plate absorber and a heat channel are enclosed. The vacuum layer passes through the entire length of the heat channel.
Coaxial tube - double flask with a vacuum "insert" between the walls of two tanks. Heat is transferred from the inside of the tube. The thermotube tip is equipped with a vacuum indicator.
The efficiency of pen tubes (1) is higher compared to coaxial models (2). However, the former are more expensive and more difficult to install. In addition, in the event of a breakdown, the pen flask will have to be replaced entirely.
The “Heat pipe” channel is the most common variant of heat transfer in solar collectors.
The mechanism of action is based on the placement in a sealed metal tube of a volatile liquid.
The popularity of “Heat pipe” is due to its affordable cost, unpretentiousness of service and maintainability. Due to the complexity of the heat exchange process, the maximum level of efficiency is 65%
Direct-flow channel - through the glass flask pass parallel, connected in a U-shaped arc metal tubes
The coolant flowing through the channel is heated and fed to the collector body.
Design options for a vacuum solar collector: 1 - modification with a central heating pipe “Heat pipe”, 2 - solar installation with direct-flow circulation of the coolant
Coaxial and feather tubes can be combined with heat channels in different ways.
Option 1. Coaxial flask with Heat pipe is the most popular solution. In the collector, heat is repeatedly transferred from the walls of the glass tube to the inner flask, and then to the coolant. The degree of optical efficiency reaches 65%.
The scheme of the coaxial tube “Heat pipe”: 1 - a shell of glass, 2 - selective coating, 3 - metal fins, 4 - vacuum, 5 - heat bulb with a light-boiling substance, 6 - inner glass tube
Option 2 Direct-flow coaxial flask is known as a U-shaped collector. Thanks to the design, heat losses are reduced - thermal energy from aluminum is transferred to the tubes with a circulating coolant.
Along with high efficiency (up to 75%), the model has disadvantages:
- complexity of installation - the flasks are a single unit with a two-pipe collector body (mainfold) and are installed as a whole;
- single tube replacement is excluded.
In addition, the U-shaped unit is demanding on the coolant and more expensive than the “Heat pipe" models.
The device of the U-shaped solar collector: 1 - glass "cylinder", 2 - absorbent coating, 3 - aluminum "cover", 4 - flask with a coolant, 5 - vacuum, 6 - inner glass tube
Option 3 Feather tube with the principle of action "Heat pipe". Distinctive features of the collector:
- high optical characteristics - efficiency of about 77%;
- a flat absorber directly transfers heat energy to a heat transfer tube;
- through the use of a single layer of glass, the reflection of solar radiation is reduced;
It is possible to replace a damaged element without draining the coolant from the solar system.
Option 4 Direct-flow fountain flask is the most effective tool for using solar energy as an alternative energy source for heating water or heating homes. The high-performance collector works with an efficiency of 80%. The disadvantage of the system is the difficulty of repair.
Schemes of the device of feather solar collectors: 1 - a solar system with a “Heat pipe” channel, 2 - a two-pipe housing of a solar collector with direct-flow movement of the coolant
Regardless of the design, tubular manifolds have the following advantages:
- performance at low temperature;
- low heat loss;
- duration of functioning during the day;
- the ability to heat the coolant to high temperatures;
- low windage;
- ease of installation.
The main disadvantage of vacuum models is the impossibility of self-cleaning from snow cover. The vacuum layer does not let heat out; therefore, the snow layer does not melt and blocks the access of the sun to the collector field. Additional disadvantages: high price and the need to comply with the working angle of inclination of the flasks is not less than 20 °.
Solar collectors that heat the air coolant can be used in the preparation of hot water, if they are equipped with a storage tank:
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Hot water tank
Manifold tube structure for air heating
Water heating in a heat carrier
System control device
Read more about the principle of operation of a vacuum solar collector with tubes, read on.
Water - the best option for the southern latitudes
Flat (panel) solar collector - a rectangular aluminum plate, closed on top with a plastic or glass cover. Inside the box there is an absorption field, a metal coil and a layer of thermal insulation. The collector area is filled with a flow line through which the coolant moves.
The basic components of a flat solar collector: housing, absorber, protective coating, thermal insulation layer and fasteners. During assembly, frosted glass with a transmittance of the spectral range of 0.4-1.8 microns is used.
The heat absorption of a highly selective absorbent coating reaches 90%. A flowing metal pipeline is placed between the “absorber” and the thermal insulation. Two tube-laying schemes are used: “harp” and “meander”.
The process of assembling solar collectors that heat the liquid coolant includes a number of traditional steps:
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In order to fix one or a group of collectors on the roof, a metal frame is assembled on it. Fastening to the crate through the coating
Before installing the tubes in which the coolant will be heated, it is necessary to check whether the sealing rings fit tightly in the nests of the manifold pipe
Glass tubes of a solar device are connected to the collector. At the top, they need to be inserted into the socket with a sealing ring, at the bottom, gently fix with a clamp, without pulling
To reduce heat loss during transportation of water heated by the sun or antifreeze, the pipe leaving the collector and the pieces connecting the devices are tightly wrapped with foil insulation
Until the home solar system is filled with coolant, adjust the angle of inclination, focusing on the actual degree of illumination
To remove air, always contained in the water and gradually released from its composition, an automatic air vent is installed at the top of the system
The assembled collector is connected to the heating system in any convenient way: through a hatch or a passage in the roof, through an opening in the wall, etc.
If there is a desire to automate the process of preparing the coolant, depending on weather conditions, it can be equipped with outdoor temperature sensors and a temperature controller
Step 1: Assembling the frame for mounting the collector group
Step 2: Preparing the manifold for pipe installation
Step 3: Attaching the Solar Collector Tubes
Step 4: Insulating the Solar Pipeline
Step 5: adjust the crucible for angle
Step 6: Installing an Automatic Air Vent
Step 7: Connect the collector to the heating circuit
Step 8: connecting to the control system
If the heating circuit is supplemented by a line supplying sanitary water to the hot water supply, it makes sense to connect a heat accumulator to the solar collector. The simplest option will be a tank of suitable capacity with thermal insulation, able to maintain the temperature of heated water. It must be installed on the flyover:
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Production of the simplest heat accumulator
Installation of a tank on a flyover
Tie-in of a branch of GVS and connection of fittings
Laying of the GVS line in the equipped house
A tubular collector with a liquid coolant acts as a "greenhouse" effect - the sun's rays penetrate through the glass and heat up the pipeline. Thanks to tightness and thermal insulation, heat is retained inside the panel.
The strength of the solar module is largely determined by the material of the protective cover:
- ordinary glass - the cheapest and brittle coating;
- strained glass - high degree of light scattering and increased strength;
- anti-reflex glass - differs in the maximum absorbing ability (95%) due to the presence of a layer eliminating the reflection of the sun's rays;
- self-cleaning (polar) glass with titanium dioxide - organic pollution burns out in the sun, and the remnants of garbage are washed off by rain.
Polycarbonate glass is the most resistant to shock. The material is installed in expensive models.
Reflection of sunlight and absorption: 1 - anti-reflex coating, 2 - tempered impact-resistant glass. The optimum thickness of the protective outer shell is 4 mm
Operational and functional features of solar panels:
- in forced circulation systems, a thawing function is provided that allows you to quickly get rid of the snow cover on the heliopol;
- prismatic glass picks up a wide range of rays at different angles - in the summer period the efficiency of the installation reaches 78-80%;
- the collector is not afraid of overheating - with an excess of thermal energy, forced cooling of the coolant is possible;
- increased impact resistance compared to tubular counterparts;
- the ability to mount at any angle;
- affordable pricing.
Systems are not without flaws. During a period of deficiency of solar radiation, as the temperature difference increases, the efficiency of a flat solar collector decreases significantly due to insufficient thermal insulation. Therefore, the panel module pays off in the summer or in regions with a warm climate.
Heliosystems: design and operation features
The diversity of solar systems can be classified by the following parameters: the method of using solar radiation, the method of circulation of the coolant, the number of circuits and the seasonality of operation.
Active and passive complex
A solar collector is provided in any solar energy conversion system. Based on the method of using the obtained heat, two types of heliocomplexes are distinguished: passive and active.
The first variety is the solar heating system, where the structural elements of the building act as the heat-absorbing element of solar radiation. The roof, the collector wall or the windows act as a solar surface.
Scheme of a low-temperature passive solar system with a collector wall: 1 - rays of the sun, 2 - a translucent screen, 3 - an air barrier, 4 - heated air, 5 - exhaust air flows, 6 - heat radiation from the wall, 7 - heat-absorbing surface of the collector wall, 8 - decorative blinds
In European countries, passive technologies are used in the construction of energy-efficient buildings. Helio-receiving surfaces decorate under false windows. Behind the glass coating is a blackened brick wall with light apertures.
The heat accumulators are structural elements - walls and floors, insulated with polystyrene from the outside.
Active systems involve the use of independent devices that are not related to the construction.
The above considered complexes with tubular, flat collectors fall into this category - solar thermal installations, as a rule, are placed on the roof of a building
Thermosiphon and circulation systems
Solar thermal equipment with the natural movement of the coolant along the collector-accumulator-collector circuit is carried out by convection - warm liquid with a low density rises up, cooled liquid flows down.
In thermosiphon systems, the storage tank is located above the collector, providing spontaneous circulation of the coolant.
The scheme of work is characteristic of single-circuit seasonal systems. Thermosiphon complex is not recommended for collectors with an area of more than 12 sq.m
Non-pressure solar system has a wide list of disadvantages:
- on cloudy days, the performance of the complex decreases - a large temperature difference is required for the movement of the coolant;
- heat loss due to slow fluid movement;
- risk of overheating of the tank due to uncontrollability of the heating process;
- collector instability;
- the difficulty of placing the battery tank - when mounted on the roof, heat losses increase, corrosion processes are accelerated, there is a risk of freezing of the pipes.
Advantages of the “gravitational” system: simplicity of design and affordability.
Capital expenditures for arranging a circulation (forced) solar system are significantly higher than installing a pressure-free complex. A pump crashes into the circuit, providing coolant movement. The operation of the pumping station is controlled by the controller.
The additional thermal power generated in the forced complex exceeds the power consumed by the pumping equipment. System efficiency will increase by a third
This method of circulation is used in year-round double-circuit solar thermal installations.
Pros of a fully functional complex:
- unlimited choice of the location of the storage tank;
- off-season performance;
- selection of the optimal heating mode;
- safety - blocking operation during overheating.
The disadvantage of the system is its dependence on electricity.
Technical solution schemes: one - and double-circuit
In single-circuit installations, fluid circulates, which is subsequently fed to the water intake points. In winter, the water from the system must be drained to prevent freezing and cracking of pipes.
Features of single-circuit solar thermal complexes:
- “refueling” of the system with purified, non-rigid water is recommended - salt settling on the pipe walls leads to clogging of channels and breakage of the collector;
- corrosion due to excess air in the water;
- limited service life - within four to five years;
- high efficiency in the summer.
In the dual-circuit heliocomplexes, a special coolant circulates (non-freezing fluid with anti-foaming and anti-corrosion additives), which transfers heat to the water through the heat exchanger.
Single-circuit (1) and dual-circuit (2) heliosystem circuitry. The second option is characterized by increased reliability, the ability to work in winter and the duration of operation (20-50 years)
The nuances of operating a dual-circuit module: a slight decrease in efficiency (3-5% less than in a single-circuit system), the need for a complete replacement of the coolant every 7 years.
Conditions for working and increasing efficiency
Calculation and installation of the solar system is best entrusted to professionals. Compliance with the installation technique will ensure operability and obtaining the declared performance. To improve efficiency and service life, some nuances must be taken into account.
Thermostatic valve. In traditional heating systems, the thermostatic element is rarely installed, since the heat generator is responsible for adjusting the temperature. However, when equipping the solar system, the safety valve must not be forgotten.
Heating the tank to the maximum permissible temperature increases collector productivity and allows the use of solar heat even in cloudy weather
The optimum valve position is 60 cm from the heater. At close proximity, the “thermostat” heats up and blocks the flow of hot water.
Placement of the storage tank. The DHW buffer capacity must be installed in an accessible place. When placed in a compact room, special attention is paid to the height of the ceilings.
The minimum free space above the tank is 60 cm. This clearance is necessary to maintain the battery and replace the magnesium anode.
Installation of an expansion tank. The element compensates for thermal expansion during stagnation. Installing the tank above the pumping equipment will provoke overheating of the membrane and its premature wear.
The best place for the expansion tank is under the pump group. The temperature effect during this installation is significantly reduced, and the membrane retains elasticity longer
Solar connection. When connecting pipes, it is recommended to organize a loop. "Thermo Loop" reduces heat loss, preventing the release of heated fluid.
Technically correct version of the implementation of the "loop" of the solar circuit. Neglect of the requirement causes a decrease in temperature in the storage tank by 1-2 ° C per night
Non-return valve. Prevents "overturning" of the coolant circulation. With a lack of solar activity, the non-return valve prevents the heat accumulated during the day from dissipating.
Popular models of "solar" modules
Heliosystems of domestic and foreign companies are in demand. Products of manufacturers have won a good reputation: NPO Mashinostroeniya (Russia), Helion (Russia), Ariston (Italy), Alten (Ukraine), Viessman (Germany), Amcor (Israel), etc.
Solar system "Falcon". Flat solar collector equipped with a multilayer optical coating with magnetron sputtering. The minimum radiation ability and high absorption level provide an efficiency of up to 80%.
Performance characteristics:
- operating temperature - up to -21 ° С;
- reverse heat radiation - 3-5%;
- top layer - tempered glass (4 mm).
Collector SVK-A (Alten). Vacuum solar installation with an absorption area of 0.8-2.41 sq. M (depending on the model). The heat carrier is propylene glycol; the heat insulation of a 75 mm copper heat exchanger minimizes heat loss.
Extra options:
- case - anodized aluminum;
- heat exchanger diameter - 38 mm;
- isolation - mineral wool with anti-hygroscopic treatment;
- coating - borosilicate glass 3.3 mm;
- Efficiency - 98%.
Vitosol 100-F - flat solar collector for horizontal or vertical mounting. Copper absorber with harp-shaped tubular coil and heliotitan coating. Light transmission - 81%.
The approximate order of prices for solar systems: flat solar collectors - from 400 cu / sq.m, tubular solar collectors - 350 cu / 10 vacuum flasks. A complete set of circulation system - from 2500 cu
The principle of operation of solar collectors and their types:
Performance assessment of a flat collector at sub-zero temperatures:
Mounting technology for a solar panel collector using the Buderus model as an example:
Solar energy is a renewable source of heat. Given the increase in prices for traditional energy resources, the introduction of solar systems justifies capital investments and pays off in the next five years, subject to installation techniques.
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