Do-it-yourself selective coating of a solar collector

Glass is traditionally used in window openings as a light barrier and protection from atmospheric conditions. Today it is an indispensable element in the design of buildings for various purposes.

The use of glass with different coatings allows you to improve the characteristics and additional functional features of the window, control the spectrum of penetrating sunlight and other possibilities.

Marking of double-glazed windows

At first glance, it may seem that the labeling of double-glazed windows is understandable only to their manufacturers. In fact, almost everyone can decipher the marking formula.

Sheet glass

• M0 (M1; M2, etc.) - transparent, colorless, obtained using a hood;
• 4 or 6,8,10 and so on. — glass thickness;
• 4float or 4F - float glass is used, 4 mm in thickness;

Float glass is a flat, colorless glass produced by continuously casting a silicate mixture onto a layer of tin that is in a liquid state (with cooling).

• 6Fjumbo - 6 mm float glass. thick; Jumbo - maximum dimensions of float glass (6000x3210 mm.)

Zinc coating for solar collectors

Zinc is a good material as a selective surface for solar collectors. There are three ways to process it to achieve maximum absorber efficiency.

Copper plating and oxidation

Zinc sheets must be washed with a solution of 20 g. sodium phosphate and 20 g. soap in 1 liter of water. Preheat the solution to boiling temperature. After degreasing, you can only work with the sheet wearing rubber gloves.

To remove oxides, treat with a solution of 5 g. hydrochloric or sulfuric acid in 100 ml. water. The solution temperature should be 18-24 degrees, processing time – 1 minute. After etching, rinse the sheet with water and dry.

For copper plating, prepare a solution:

• Copper sulfate (CuSO4) – 10 grams;
• Concentrated sulfuric acid (H2SO4) – 10 ml;
• Water – 1 liter.

Treat the sheet with the solution for 2-5 minutes (see the result), then rinse it with water. After the copper plating procedure, the surface can be treated like a regular copper sheet.

Powder paint application

Copier or printer toner can be used as a selective paint for solar collectors. A zinc or galvanized sheet must be heated with a construction hairdryer, and then evenly coated with powder.

The toner is soldered to zinc without losing its matte finish, which ensures good absorption of sunlight. If the powder melts and a glossy surface is formed, it is treated with fine-grained sandpaper.

Printer or copier toner is also used to improve the absorbent properties of zinc.

Galvanization blackening

Zinc can be chemically blackened to increase absorption capacity. Home-made chemicals are ineffective - the resulting selective coating quickly collapses. Analogues are ready-made mixtures and reagents available for free sale.

Laminated glass or triplex

A product consisting of more than 2 glasses, which are bonded with a layer or several layers of special polymers.

Divided into several types according to purpose:

• Fire resistant;
• Resistant to mechanical stress;
• Noise-proof;

Soundproofing glass effectively absorbs acoustic vibrations of different frequencies. Can provide isolation from 40 to 70 dB.

• With special properties (for example, it interrupts radio waves, etc.).

Special-purpose glasses can partially dampen or completely reflect microwave and electromagnetic radiation. Through them it is impossible to listen to information that should not leave the walls of the building. Such glazing is installed in special services, large companies and private properties.

Marking:

• MS 33.2 is laminated glass with a thickness of 8 mm. (3 mm;2 mm;3 mm);
• 4-4-1 - laminated glass thickness 9 mm (4 mm; 1 mm; 4 mm).

Film for panels

There is another option for applying a selective absorbent coating. For this purpose, a special film was developed, which is currently available in two types: single-layer and multilayer on a metallized substrate.

As for the effectiveness of films, the coefficient is quite high and is comparable to the same indicator for paints, but if we talk about the cost, it is very different. High-quality film is characterized by the fact that its emissivity is 5% or less.

As for the application process, the procedure is very simple. A single-layer self-adhesive film is attached to a sheet of metal, which can be made of zinc, copper, or aluminum. There is no need to carry out any complex manipulations; the film is glued very easily. However, before applying it, it is worth treating the metal sheet in the same way as was done with paint, that is, you need to treat it with a grinding machine with an abrasive wheel.

Solar control glass

Such a product is capable of either reflecting or absorbing infrared radiation.

This is reliable protection in the summer heat. While the glass remains transparent, it provides very effective protection from the sun's rays, similar to closed blinds. If windows with solar control glass are installed in the house, then it will heat up at least 2 times less than when installing double-glazed windows with standard glass.

Divided into groups according to manufacturing technology:

• Reflex;
• Tinted in bulk;
• With soft coating (magnetron nanocoating).

Marking:

• 4ANTELIO - 4 mm thick, available in three colors - bronze, green, gray (manufacturer Saint-Gobain);
• 4 SunStop - 4 mm, manufacturer Glas-Trösh;
• 4 SGSolar - 4 mm, from SunGuard;
• 4SolarCool - 4 mm, reflective from PPG;
• 4StopSol is a manufacturer of AGC. It can have four types of coating: Supersilver, Classic, Silverlight, Phoenix.

Safety precautions

1. All organic matter is quickly corroded by NaOH, so you should not take the solution with your bare hands. On the contrary, you need to use protective equipment (rubber gloves, goggles), because during the reaction caustic sodium boils violently.
2. NaСlО₂ is not so dangerous, but it is also better not to take it with your hands. Releases chlorine.
3. (NН₄)₂S₂О₈ releases a lot of ammonia during the reaction, so the procedure cannot be carried out indoors. It is advisable to use a respirator.
4. It would seem that a respirator is not needed in the open air, but in such conditions it is impossible to achieve the required temperature even in the hot summer.
5. The safest is K₂S₂O₈, but at the same time it is also the most expensive of the reagents.

Strained glass

The strength of the product is increased by chemical or mechanical treatment. It has increased impact resistance and resistance to sudden temperature changes due to thermal or chemical hardening. Such products are usually used in boiler rooms and saunas. Even if they are used in places of very high temperatures, they retain their primary characteristics.

Distributed into groups:

• Thermal hardening;
• Thermal strengthening;
• Chemical hardening.

Marking:

• 6TVG - 6 mm, heat-strengthened;
• 4ESG - 4 mm, heat-hardened.

Methods for producing copper oxide

To obtain CuO, it is necessary to oxidize the copper itself - the absorber is, in fact, made from it. There can be no rollers or brushes here.

The main methods for preparing (more precisely, components) of a solution for copper oxidation are discussed below.

Method one

1. Liter of water.
2. 15 g of potassium persulfate (K₂S₂O₈).
3. 50 g caustic soda (NaOH).

   Caustic soda

Method two

Everything is almost the same as in the first method, only instead of K₂S₂O₈ it is necessary to use ammonium persulfate ((NH₄)₂S₂O₈).

Method three

1. Liter of water.
2. 50 g sodium chlorite (NaСlО₂).
3. 100 g caustic soda (NaOH).

Mandatory conditions for all oxidation methods

1. All surfaces must be free of grease.
2. The solution temperature should be within 62-65ᵒC.
3. During the reaction, oxygen will be released, which will quickly evaporate, so the solution must be fresh.
4. It is advisable to use distilled water.

Energy saving glass

In the manufacture of energy-saving glass, a soft or hard coating of thin balls of metal oxides that reflect infrared radiation and electromagnetic waves is applied to the surface of sheet glass.

In the production of K-glass (hard-coated), indium or tin oxide is applied to the hot surface of the sheet.

Marking:

• Pilkington K Glass - hard coated from Pilkington;
• 4K - K-glass, 4 mm. thickness.

Transparent products with a soft coating (I-glass) are made using vacuum magnetron deposition of a layer of silver oxide, which can reflect thermal energy.

The most recognizable markings of I-glass are:

• Top;
• Low-e;
• I;
• E;
• AND.

Other markings:

• ZERO E - a product with a unique Silverstar Zero coating, from Glas-Trösh;
• Optitherm - has an energy-saving coating, manufactured by Pilkington;
• Futur-N - PLANITHERM FUTUR N energy coating from Saint-Gobain;
• Top-N - energy saving from AGC;
• Enplus - Silverstar Enplus coating from Glas Trösh;
• ClimaN - ClimaGuard N coating from Guardian.

Selective-cover

Separately, it is worth mentioning the most popular, perhaps, selective coating - namely Selective-Cover Silver Mirror. This is one of the best reagents that absorb solar energy.

Has the following characteristics:

• selectivity index 16;
• reliability, ease of use;
• operating temperature up to 365ᵒС;

· Possibility of application by roller, spray or even brush.

Based on the reagent, an electrolyte can be produced, which is applied electrochemically. One bottle (costs approximately 3,000 rubles) is enough for:

• 6 m² with electrochemical application;
• 2 m² with contact.

Selective glass

This is an innovative high-tech product. Ideally combining sun protection and energy saving properties. Allows you to achieve a high level of light transmission, while providing effective heat conservation.

Due to multi-layer spraying of a special coating, the multifunctional product blocks infrared radiation and reflects thermal energy, allowing only useful daytime color to penetrate into the room.

Extra selective glass is triple coated with silver, which allows for improved technological characteristics. In addition, it is able to transmit a sufficient amount of daylight and at the same time provide excellent protection from harmful solar radiation. Owners of large country houses or cottages will be able to save significantly by reducing costs for lighting, heating and cooling of premises.

Marking:

• ClimaSolar - highly selective glass from Guardian;
• LifeGlassGlear - second generation multifunctional glass from Pilkington;
• SELEKT - float glass with Silverstar Combi coating from Glas-Trösh;
• StopRay Neo is a multifunctional light transmission product from AGC.

Double-glazed windows using highly selective glass have the highest heat transfer coefficient.

Features of functioning in the cold

Everyone knows that one of the most important purposes of a window is to protect both one room and the entire apartment (house) from the cold. However, not many people know that a room loses much more heat through a window than, say, through walls, ventilation, and even a door. That’s why it’s so important to ensure comfortable conditions by installing high-quality modern windows. It doesn't matter which profile you choose: PVC, wood or aluminum. It is necessary to pay special attention to the choice of double-glazed windows and glass for it, because it is this that takes up almost 90% of the window structure, which means it is one of the main constituent elements.

To increase the thermal insulation characteristics of a double-glazed window, instead of the usual so-called float glass, you can use low-emissivity glass, the peculiarity of which is its coating, which includes a thin layer of sputtering of silver atoms. Technology incorporating silver allows the glass to easily transmit short waves emitted by the celestial body (in other words, transmit light). The long ones emitted by heating devices are blocked and do not “leak” out.