Solar energy as an alternative energy source: scheme

In the last decade, solar energy as an alternative source of energy is used more and more for heating buildings and provide hot water. The main reason - the desire to replace the traditional fuel accessible, environmentally clean and renewable energy resources.

Converting solar energy into heat takes place in the Solar - module design and operating principle determines the specificity of its application.

In this article we look at the variety of solar collectors and principles of their operation, as well as tell you about popular models of solar modules.

The feasibility of using solar

Geliosistema - system for converting solar radiation into thermal energy, which is then passed to a heat exchanger for heating the coolant or heating water system.

Efficiency solar thermal installation depends on the insolation - the amount of energy supplied for a light day on the surface of 1 square meter at an angle of 90 ° relative to the direction of sunlight. Measuring the value of the index - kWh / sq m, the value varies depending on the season.

The average level of solar insolation for the temperate continental climate of the region - 1000-1200 kWh / square meter (per year). The amount of the sun - defining the parameter to calculate the solar performance.

Installation gelioteplosnabzheniya system - an expensive event. To capital expenditures were justified, an accurate calculation of the system and compliance with the installation technology.

Example. The average value of insolation for Tula in midsummer - 4.67 kW / m * day provided installation panel at an angle of 50 °. Performance solar collector 5 square meters is calculated as follows: 4.67 * 4 = 18.68 kW of heat energy per day. This volume is sufficient for 500 liters of water heated to a temperature of from 17 ° C to 45 ° C.

Speaking about the feasibility of the introduction of new technologies, it is important to take into account the specific technical features of the solar collector. Some start working at 80 W / m of solar energy and other enough - 20 W / sqm

Even in the southern climate, the use of the collector system only not pay for heating. If the installation will be used exclusively in the winter sun with a deficit, the cost of the equipment is covered and for 15-20 years.

To maximize geliokompleks, it must be included in the hot water system. Even in winter geliolektor would "cut" account for energy for heating water up to 40-50%.

In addition to the economic benefits of "solar heating" has additional advantages:

1. Environmentally friendly. Reduced carbon dioxide emissions. Over 1 year sq solar collector into the atmosphere prevents 350-730 kg mining.
2. Aesthetics. Space of a compact bath or kitchen manages to get rid of bulky boilers or geysers.
3. Durability. Manufacturers claim that, subject to installation technology, the complex will last about 25-30 years. Many companies provide a guarantee of up to 3 years.

Arguments against the use of solar energy: a pronounced seasonality, depending on weather and high initial investment.

The general design and function

Consider the embodiment with the solar collector as a primary system operating element. Exterior unit resembles a metal box, the front side of which is made of tempered glass. Inside the box is located a working body - the coil to the canister.

A heat absorbing block provides coolant heating - circulating fluid transfers heat generated in the water circuit.

Solar collector necessarily work in tandem with the storage tank. Since the coolant is heated to a temperature of 90-130 ° C, it can not be fed directly into the hot water taps or radiators. Heat transfer fluid enters the heat exchanger of the boiler. Storage tank is often supplemented by an electric heater.

Scheme of work:

1. The sun heats the surface collector.
2. Thermal radiation is transmitted absorbent member (absorber), which contains a working fluid.
3. Circulating in the coil tubes is heated coolant.
4. Pumps, control unit and provide the retraction control of the coolant conduit to the coil of the storage tank.
5. Implemented heat transfer water in the boiler.
6. The cooled coolant flows back into the reservoir and the cycle repeated.

The heated water from the heater is fed into the heating circuit or to the water intake points.

Variety of solar collectors

Regardless of the destination, solar system comes with a flat or spherical tube geliokollektorom. Each option has a number of distinctive features in terms of performance and operation efficiency.

Vacuum - for cold and temperate climate

Solar collector vacuum structurally resembles a thermos - narrow tubes with coolant placed in flasks larger diameter. Formed between the vacuum vessels layer responsible for the thermal insulation (heat preservation - up to 95%). The tubular shape is optimal to hold the vacuum and "occupation" of the sun's rays.

The inner (heat) tube filled with saline solution having a low boiling point (24-25 ° C). When heated liquid is evaporated - the evaporation flask move upward and heated heat medium circulating in the collector housing.

During the condensation of water droplets flow down in the tube tip and the process repeats.

Due to the vacuum within the liquid layer of the flask is capable of heat to boil and vaporize in subzero outdoor temperatures (up to -35 ° C).

Characteristics of solar modules depend on such criteria:

• tube design - fountain, coaxial;
• heat channel device - «Heat pipe», Co-current circulation.

Fountain bulb - a glass tube, in which the enclosed plate and the heat absorber duct. Vacuum layer extends across the channel length of the heat.

coaxial tube - double vacuum flask with "insert" between the walls of the two tanks. Heat transfer is carried out from the inner surface of the tube. Tip Heat-equipped vacuum indicator.

Channel «Heat pipe» - the most common heat transfer in solar collectors embodiment.

The mechanism of action is based on placement in sealed metal tubes of a volatile liquid.

The continuous-flow channel - through a glass flask are parallel connected in a U-shaped metal arc tube

The coolant flowing through the channel is heated and supplied to the manifold housing.

Coaxial and fountain tubes can be combined in different ways with the thermal channels.

Option 1. Coaxial with the bulb «Heat pipe» - the most popular solution. The collector occurs multiple heat transfer from the walls of the glass tube to the inner flask and then to the coolant. The degree of optical efficiency reaches 65%.

Option 2. Coaxial flask with a co-current circulation is known as the, U-shaped collector. Due to the design reduces heat loss - the heat energy is transferred from the aluminum tubes with a circulating coolant.

Along with high efficiency (up to 75%) of the model has some drawbacks:

• installation complexity - bulb are integral with the body of a two-pipe manifold (mainfold) and are set entirely;
• It ruled out the replacement of single tubes.

In addition, U-shaped assembly demanding and expensive coolant «Heat pipe» models.

Option 3. Pen tube with the principle of action «Heat pipe». Distinctive features of the reservoir:

• high optical characteristics - an efficiency of about 77%;
• flat absorber directly transfers energy to heat with the coolant tube;
• by utilizing a single glass layer is reduced reflection of solar radiation;

Possible replacement of the damaged element without emptying the solar system.

Option 4. Fountain bulb ram action - the most effective tool for the use of solar energy as an alternative energy source for heating water or home heating. High collector operates with efficiency - 80%. The disadvantage of the system - the difficulty of repair.

Regardless of the performance tube collectors have the following advantages:

• operability at a low temperature;
• low heat loss;
• the duration of operation during the day;
• ability to heat the coolant to a high temperature;
• low windage;
• ease of installation.

The main drawback of the vacuum models - the impossibility of self-cleaning of the snow cover. Vacuum layer does not transmit the heat to the outside, so the layer of snow melts and covers the sun access to the collector field. Additional disadvantages: the high cost and the need for working angle flasks not less than 20 °.

More details about the working principle of vacuum solar collector tubes to read Further.

Water - the best option for the southern latitudes

Flat (panel) Solar collector - a rectangular aluminum plate, a closed top plastic or glass cover. Inside the box is arranged an absorption field, the metal coil and insulation layer. collector area is filled with a flow conduit through which coolant moves.

Heat absorption by a highly selective absorbent coating reaches 90%. The flow conduit is arranged between the metallic "absorbent" and thermal insulation. It is used two tubes laying schemes: "Harp" and "meander".

Tubular collector with heat transfer fluid acts as a "greenhouse" effect - the sun's rays penetrate through the glass and heated tubing. Due tightness and heat insulation is maintained within 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 - a high degree of light scattering and increased strength;
• antirefleksnoe glass - different maximum absorption capacity (95%) by the presence of the layer depleting reflected rays of the sun;
• self-cleaning (polar) glass with titanium dioxide - organic pollution fade in the sun, and the remains of garbage washed away by rain.

Most endures blows polycarbonate glass. The material is installed in expensive models.

Operational and functional features panel solar power plants:

• in forced circulation systems is provided defrosting function allows you to quickly get rid of the snow cover at Heliopolis;
• prismatic glass captures a wide range of beams from different angles - efficiency of the plant in the summer reaches 78-80%;
• the collector is not afraid of overheating - if an excess of thermal energy possibly forced cooling the coolant;
• improved impact strength as compared with tubular counterparts;
• can be mounted at any angle;
• affordable pricing.

Systems are not without drawbacks. Between the solar radiation deficiency with increasing temperature difference, the efficiency of a flat solar collector falls significantly due to insufficient thermal insulation. Therefore, the panel module pays off in the summer or in warm climates.

Solar: features of the design and operation

The variety of solar systems can be classified according to parameters: the method of use of solar radiation, the method of circulation of the coolant, and the number of circuits operating seasonality.

Active and passive range

In any solar energy conversion system has a suntrap. Proceeding from a method of using generated heat geliokompleksov two types: passive and active.

The first kind - solar heating system where the heat sink element sunlight act structural elements of the building. As geliopriemnoy surface act roof, wall or window-collector.

In European countries, passive technologies are used in the construction of energy efficient buildings. Geliopriemnye surface decorated with a false window. For the coated glass is placed brick wall with svetoproemami blackened.

As the storage tank are the elements of construction - walls and ceilings, polystyrene insulated from the outside.

Active systems involve the use of stand-alone devices that are not related to construction.

Thermosiphon and circulation systems

Solar thermal equipment with the natural movement of the coolant circuit of the collector-accumulator-collector carried by convection - warm fluid with low density rises cooled - flows way down.

In systems of thermosiphon storage tank is located above the reservoir, providing a spontaneous circulation of the coolant.

Gravity solar system is a wide range of shortcomings:

• on cloudy days of the complex performance falls - for coolant flow large temperature difference is required;
• heat loss due to a slow movement of the liquid;
• risk of overheating due to uncontrollability tank heating process;
• instability of the collector;
• the complexity of the placement of the storage tank - for installation on the roof of the heat loss increases, accelerated corrosion processes, the risk of freezing pipes appears.

Pros "gravity" of the system: simplicity of design and affordability.

Capital costs for the circulation arrangement (forced) considerably higher solar installation unconfined complex. The circuit "cuts" pump for coolant flow. Job controller operated pump station.

Such a process is involved in circulation year-round dual-circuit solar heating units.

A full-featured set of pros:

• unlimited choice of the location of the storage tank;
• performance out of season;
• selection of the optimum heating mode;
• Safety - lock operation in case of overheating.

The disadvantage of the system - dependent on electricity.

Technical schemes solution, one - and two-circuit

In single-loop installations circulating fluid that subsequently is supplied to the water intake points. In winter, the water drained from the system is necessary to prevent freezing and cracking tubes.

Features single-circuit solar heating systems:

• Recommended "refill" system nonrigid purified water - deposition of salts on the tube walls leads to clogging of channels and reservoir damage;
• corrosion due to the excess air in water;
• limited lifetime - within four to five years;
• high efficiency in the summer.

The combi geliokompleksah special circulates coolant (antifreeze with antifoam and anti-corrosion additives), water gives off heat through the heat exchanger.

Nuances of operation of a bypass module: a slight decrease in efficiency (3-5% less than in the single-system), the need for complete replacement of the coolant every 7 years.

Working conditions and efficiency

Calculation and installation of solar systems is best left to professionals. Compliance with the installation equipment to ensure the efficiency and performance of applications received. To improve the efficiency and the period of service must take into account some of the nuances.

Thermostatic valve. In traditional heating systems thermostatic element rarely installed as for temperature control responds heat source. However, the regeneration of the solar safety valve must not be forgotten.

Optimal placement of the valve - 60 cm from the heater. In close proximity "thermostat" is heated and blocks the flow of hot water.

Placement of the storage tank. DHW buffer tank must be installed in an accessible location. When placed in a compact room focuses on the height of ceilings.

installation expansion tank. Member compensates thermal expansion in the stagnation period. Installation of the tank above the pump equipment will provoke overheating of the membrane and its premature wear.

Connecting the solar circuit. When connecting the pipes is recommended to arrange the loop. "Termopetlya" reduces heat loss by preventing the heated fluid outlet.

The check valve. Warns "overturning" circulation of the coolant. With a lack of solar activity check valve does not dissipate heat accumulated during the day.

Popular model "solar" modules

Demand for solar domestic and foreign companies. Good reputation won the product manufacturers: NPO Machine Building (Russia), Helion (Russia), Ariston (Italy), Viola (Ukraine), Viessman (Germany), the Amcor (Israel) and others.

"Falcon" solar system. Flat Solar collector, equipped with an optical multilayer coated with magnetron sputtering. The minimum emission capacity and high absorption rate provide efficiency up to 80%.

Performance:

• Working temperature - up to -21 ° C;
• reverse heat radiation - 3-5%;
• the top layer - glass (4 mm).

Collector CRS-A (Viola). Vacuum solar thermal system with absorption area 0,8-2,41 m (depending on model). Coolant - propylene insulated copper heat exchanger 75 mm minimizes heat loss.

Extra options:

• housing - anodised aluminum;
• coil diameter - 38 mm;
• isolation - with rockwool antigigroskopichnoy treatment;
• coating - borosilicate glass of 3.3 mm;
• Efficiency - 98%.

Vitosol 100-F - Solar collector flat horizontal or vertical assembly. Copper absorber arfoobraznym tubular coil and titanium coated. Light transmission - 81%.

Conclusions and useful videos on the topic

Principle of operation of solar collectors and their types:

Assessment of the Performance of a flat collector-zero temperatures:

Technology mounting panel solar collector on the example of Buderus models:

Solar energy - renewable sources provide heat. Taking into account the rise in prices for traditional energy resources justifies the introduction of solar systems, and capital investment pays off in the next five years, subject to installation technology.

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