Passive solar systems. Window. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Alternative energy sources

 Comments on the article

The effectiveness of any passive system depends on the type of windows. Glass or other transparent materials let short waves through and block long waves of heat radiation indoors. Windows regulate the energy flow in two main ways: in winter, they provide heat to the house by letting solar energy into the building, due to which the air temperature inside the premises exceeds the outside temperature; in the summer, they help cool the building by reducing the amount of sunlight that enters through the window by well positioning and shading it, and by using ventilation to cool the house.

If we use solar heat, then it is necessary to ensure its penetration into the room exactly at the time when it is most useful. As a rule, in winter, the sun's rays should fall into the room from 9.00 to 15.00. It is desirable that there are practically no obstacles in their way. So, the trees on the site can obscure the rooms of the house. This must be taken into account during construction. You can plan a house with windows facing either side. At the same time, the building will have low energy consumption. When designing, the frame of the building, that is, the walls, floor and ceiling, is more important than the location of the internal partitions. If you want the window to face west, you need to properly shade it and choose the appropriate size.

Glass transmits solar radiation waves in the range of 0,4-2,5 microns. As a result of the absorption of light by opaque objects located inside the room, and further re-emission, its wavelength increases to 11 microns. Glass is an impenetrable barrier to an electromagnetic wave of this length. Light entering the room is trapped. The amount of light passing through the glass depends on the angle of incidence. Optimum angle of incidence - 90°. If sunlight hits the glass at an angle of 30° or less, then most of the sunlight is reflected.

(click to enlarge)

Solar radiation spectrum and heat transfer

To choose the right glazing, you need to have an idea about light and warmth. The spectrum of sunlight hitting the Earth consists of waves of different wavelengths. Different glasses transmit, absorb and reflect solar radiation waves in different ways. For example, reducing bright light (by reflection or shading) is useful in the workplace. By letting in daylight, you can save the energy needed for artificial lighting. The most favorable for a person are infrared rays, which create a feeling of comfort. By identifying the right type of glass, you can either transmit or reflect infrared radiation.

There are three options for the passage of heat through the material used for glazing. The first is thermal conductivity: in this case, heat passes through the glass. To feel the heat, just touch the glass. The second form of heat transfer is radiation: electromagnetic waves transfer heat through glass. This creates the feeling that the surface of the window radiates heat. The third way to move heat is convection. Convection moves heat through the movement of air, in this case air currents. The natural movement of warm air to colder air allows you to raise or lower the temperature in the room.

The thermal resistance index of the material (R-value) used for glazing is determined by its degree of thermal conductivity, radiation and convection. The overall value of the thermal resistance index of the window as a whole is affected by the infiltration of the air flow. The amount of heat that passes through the glazing is just as important as the movement of heat through the windows. The quality of manufacture and installation of the entire window, including the installation of the frame, affects the degree of air penetration.

Advances in window technology significantly affected building efficiency in the 70s and today play an important role in passive solar systems. Here are some advances in window technology:

• Double and triple glazing (double glazing) with a high degree of thermal insulation.
• Low emissivity glass that has a coating that lets heat in but does not let it out.
• The use of argon (or other inert gas) to fill the space inside an insulating glass unit, resulting in an increase in the degree of thermal insulation compared to insulating glass units filled with ordinary air.
• Technologies based on the use of a phase transition, which allow you to change the degree of transparency of glass using electrical voltage.

Main types of glass

The materials used for glazing include: glass, acrylic fibers, fiberglass, etc. Although different materials have different applications, the most common is the use of glass. Various types of glass allow the designer to develop a passive solar house that meets all customer requirements. Single pane is the simplest of all types of glass and is the building block for higher quality glazing. Ordinary glass has high transparency to sunlight, but poor thermal insulation - the coefficient of thermal resistance is approximately 1,0. Ordinary window glass can perform its role effectively when used in double-pane or double-pane windows, in buildings located in warm climate regions (unless air conditioning is also used), in some types of solar collectors, and in seasonal greenhouses. Structures that use single panes of glass are usually subject to large temperature fluctuations, drafts, condensation and do not block cold air from outside well.

The most common structure used in construction today is the double-glazed window. A double-glazed window is two glasses assembled into one product. Single glasses (thermoglass) are connected into a single structure by an intermediate bar, consisting of a material that absorbs moisture. This design is usually sealed with silicone. A closed air space is formed between the glasses, which contributes to an increase in thermal resistance, the coefficient of which for a double-glazed window is approximately 1,8-2,1. Practice has shown that the best distance between glasses for airspace is 1-2 centimeters. A larger distance between the panes will not increase the coefficient of thermal resistance much.

In fact, a large air space can increase convection in an insulating glass unit and lower the temperature as a result. Of course, you can increase the distance between the glasses up to 10-12 centimeters without creating a convection flow, but then the product will be very bulky. The increased demand for energy efficiency in buildings has led to double-glazed windows becoming the standard in construction. With good transparency for solar energy and high-quality thermal insulation, such windows represent a significant step forward compared to a conventional window. Double-glazed windows are used in the production of windows, doors, for the construction of glazed roofs, solariums, and in many other areas.

high quality glass

High quality glass has a higher thermal resistance coefficient and good transparency for solar energy. By increasing the insulating capacity of the glass, the design of the building can be improved at the same time. Premises previously enclosed by walls can be converted into so-called solar rooms with passive solar lighting (windows in the roof and ceiling). Dark rooms will be filled with natural light, solar warmth, and wonderful views from the window can also open up. With a relatively small increase in cost, it is possible to improve energy efficiency, provide greater moisture resistance and UV protection. And as a result - a variety of building projects. Today, a large variety of high-quality glass is available to consumers.

What are the advantages of such glass? Glass with a low emissivity (low ability of the material to transmit infrared (thermal) radiation) increases the energy efficiency of an insulating glass unit. The higher the emissivity, the more heat the material transmits. Conversely, the lower this coefficient, the more heat is reflected by the material. Coatings having a low emissivity will reflect or re-radiate infrared radiation back into the room, thus increasing the temperature. When converted to the drag coefficient, the latter will be 2,6-3,2.

For warmer climates, building windows can be modified to radiate infrared heat back to the outside, keeping the temperature inside the home cooler. Low emissivity glass has high thermal resistance, UV protection and moisture resistance. Windows filled with inert gas have a higher coefficient of thermal resistance, its index increases by about 1,0. The air inside the insulating window is replaced by an inert gas with better insulating performance. The most commonly used gases are krypton and argon.

window curtains

In addition to performing decorative functions, curtains can reduce heat loss during the cold months, or prevent the temperature from rising during the warm season. A cornice made of, for example, plywood will prevent the warm air under the ceiling from moving into the space between the window and the curtain. To achieve the desired result, the curtains should be at least 30 cm longer than the height of the window, although it is most optimal when they are floor-length.

See other articles Section Alternative energy sources.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Energy from space for Starship 08.05.2024

Producing solar energy in space is becoming more feasible with the advent of new technologies and the development of space programs. The head of the startup Virtus Solis shared his vision of using SpaceX's Starship to create orbital power plants capable of powering the Earth. Startup Virtus Solis has unveiled an ambitious project to create orbital power plants using SpaceX's Starship. This idea could significantly change the field of solar energy production, making it more accessible and cheaper. The core of the startup's plan is to reduce the cost of launching satellites into space using Starship. This technological breakthrough is expected to make solar energy production in space more competitive with traditional energy sources. Virtual Solis plans to build large photovoltaic panels in orbit, using Starship to deliver the necessary equipment. However, one of the key challenges ... >>

New method for creating powerful batteries 08.05.2024

With the development of technology and the expanding use of electronics, the issue of creating efficient and safe energy sources is becoming increasingly urgent. Researchers at the University of Queensland have unveiled a new approach to creating high-power zinc-based batteries that could change the landscape of the energy industry. One of the main problems with traditional water-based rechargeable batteries was their low voltage, which limited their use in modern devices. But thanks to a new method developed by scientists, this drawback has been successfully overcome. As part of their research, scientists turned to a special organic compound - catechol. It turned out to be an important component that can improve battery stability and increase its efficiency. This approach has led to a significant increase in the voltage of zinc-ion batteries, making them more competitive. According to scientists, such batteries have several advantages. They have b ... >>

Alcohol content of warm beer 07.05.2024

Beer, as one of the most common alcoholic drinks, has its own unique taste, which can change depending on the temperature of consumption. A new study by an international team of scientists has found that beer temperature has a significant impact on the perception of alcoholic taste. The study, led by materials scientist Lei Jiang, found that at different temperatures, ethanol and water molecules form different types of clusters, which affects the perception of alcoholic taste. At low temperatures, more pyramid-like clusters form, which reduces the pungency of the "ethanol" taste and makes the drink taste less alcoholic. On the contrary, as the temperature increases, the clusters become more chain-like, resulting in a more pronounced alcoholic taste. This explains why the taste of some alcoholic drinks, such as baijiu, can change depending on temperature. The data obtained opens up new prospects for beverage manufacturers, ... >>

Random news from the Archive Growing teeth right in your mouth 13.06.2020 Scientists have proposed a new way to "grow" teeth directly in a person's mouth, which will take about nine weeks. The corresponding work was carried out by the staff of Columbia University. Dr. Jeremy Mao proposed using stem cells to "grow" a tooth, as well as DNA in the human body. The discovery is an important step in the development of dentistry, providing new solutions for those who suffer from dental problems. In particular, the missing bone formation is planned to be replaced with stem cells, after which it will begin to merge with surrounding cells. Thanks to this approach, the regeneration process will be noticeably accelerated, which means that recovery will be fast. So far, this procedure is only being studied by a wide range of specialists, and only after that the possibility of introducing such a practice in dentistry will be considered.

Other interesting news:

▪ Artificial skin feeling pain

▪ New synchronous boost converter chipsets

▪ Australian rock art

▪ 13-megapixel camera module for Samsung smartphones

▪ Samsung Portable SSD T1

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ section of the site for the Builder, home craftsman. Selection of articles

▪ article State policy in the field of prevention and elimination of emergencies, protection of the population and territories. Basics of safe life

▪ article What is the Mohorovichic surface and how was it discovered? Detailed answer

▪ article Belovezhskaya Pushcha. Nature miracle

▪ Article Fiberglass. Encyclopedia of radio electronics and electrical engineering

▪ article Replacing the card (six ways). Focus Secret

Leave your comment on this article:

All languages ​​of this page

Arabic	Hebrew	Polish
Bengali	Hindi	Portuguese
Chinese	Italian	Spanish
English	Japanese	Turkish
French	Korean	Ukrainian
German	Malay	Vietnamese

Home page | Library | Articles | Website map | Site Reviews

www.diagram.com.ua
2000-2024