Solar heating
From Wikipedia, the free encyclopedia
Solar heating is the usage of solar energy to provide process, space or water heating. See also Solar thermal energy. The heating of water is covered in solar hot water. Solar heating design is divided into two groups:
- Active solar heating uses pumps which move air or a liquid from the solar collector into the building or storage area.
- Passive solar heating does not require electrical or mechanical equipment, and may rely on the design and structure of the house to collect, store and distribute heat throughout the building (passive solar building design).
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[edit] History
The very first solar heating factory in the world was built by Jewish immigrants, from South Africa, in Ashqelon Israel in 1952. In 1980 law was passed in Israel making solar heating mandatory.
[edit] How solar heating works
A household solar heating system consists of a solar panel (or solar collector) with a heat transfer fluid flowing through it to transport the heat energy collected to somewhere useful, usually a hot water tank or household radiators. The solar panel is located somewhere with good light levels throughout the day, often on the roof of the building. A pump pushes the heat transfer liquid (often just treated water) through the panel. The heat is thus taken from the panel and transferred to a storage cylinder.
[edit] Other uses
Solar heating also refers to the heating of any objects, including buildings, cars, through solar radiation. Solar heating depends on the solar radiation, surface area, surface reflectance, surface emissivity, ambient temperature, and thermal convection from wind. With most all objects on Earth, solar heating reaches a state of temperature equilibrium as the heat imparted by the sun is offset by the heat given off through reflection, radiation, and convection. White objects stay dramatically cooler than other objects because the most important variables are characteristics of the surface, reflectance, emissivity, convection and surface area. Silvery objects get hot even though they are excellent reflectors because they are very poor in heat emission. Human skin, and many other living surfaces, like tree leaves, have near perfect emissivity (~1.0), and so stay pretty cool. A perfect sunscreen is a dye that perfectly absorbs, with high emissivity, or perfectly reflects, ultraviolet and infrared while being transparent in visible light.
It is worth noting that it is impossible for any material to be a good absorber of a given frequency and at the same time a poor emitter of the same frequency ( or the other way around). The difference in absorption and emission arises because the radiation emitted by a relatively cold object like a human, has much lower frequency than the radiation emitted by a hot object like the sun. Materials which have high emissivity for low frequencies but high absorption at higher frequencies will therefore stay much cooler than materials which have high absorption of high frequencies and low emission of low frequencies.
[edit] Worldwide
| Solar Hot Water Installed Capacity 2005[1] | ||||||||
|---|---|---|---|---|---|---|---|---|
| Country | million m2 | GWth | ||||||
| China | 79.3 | 55.5 | ||||||
| EU | 16.0 | 11.2 | ||||||
| Turkey | 8.1 | 5.7 | ||||||
| Japan | 7.2 | 5.0 | ||||||
| Israel | 4.7 | 3.3 | ||||||
| Brazil | 2.3 | 1.6 | ||||||
| United States | 2.3 | 1.6 | ||||||
| Australia | 1.7 | 1.2 | ||||||
| India | 1.5 | 1.1 | ||||||
| World | 125 | 88 | ||||||
[edit] Solar heating in Europe
| Solar heating systems with glazed collectors* (kWth)[2] | ||||||||
|---|---|---|---|---|---|---|---|---|
| Total (2006) | Added in 2006 | Added in 2005 | Added in 2004 | |||||
| Germany | 5 637 800 | 1 050 000 | 665 000 | 525 000 | ||||
| Greece | 2 301 040 | 168 000 | 154 350 | 150 500 | ||||
| Austria | 1 828 139 | 204 868 | 163 429 | 127 816 | ||||
| Italy | 598 661 | 130 200 | 88 941 | 68 417 | ||||
| Spain | 491 516 | 122 500 | 74 760 | 63 000 | ||||
| France | 430 920 | 154 000 | 85 050 | 36 400 | ||||
| Cyprus | 392 140 | 42 000 | 35 000 | 21 000 | ||||
| Switzerland | 310 484 | 36 304 | 27 392 | 21 812 | ||||
| Denmark | 253 596 | 17 710 | 14 875 | 14 000 | ||||
| Netherlands | 222 909 | 10 280 | 14 174 | 18 410 | ||||
| UK | 175 644 | 37 800 | 19 600 | 17 500 | ||||
| Sweden | 165 850 | 19 977 | 15 835 | 14 041 | ||||
| Portugal | 126 665 | 14 000 | 11 200 | 7 000 | ||||
| Poland | 117 264 | 28 980 | 19 390 | 20 230 | ||||
| Slovenia | 76 510 | 4 830 | 3 360 | 1 260 | ||||
| Czech Republic | 74 711 | 15 421 | 10 885 | 8 575 | ||||
| Belgium | 72 883 | 24 945 | 14 164 | 10 290 | ||||
| Slovakia | 50 925 | 5 950 | 5 250 | 3 850 | ||||
| Romania | 48 370 | 280 | 280 | 280 | ||||
| Bulgaria | 17 570 | 1 540 | 1 400 | 1 260 | ||||
| Malta | 16 702 | 3 150 | 2 800 | 2 951 | ||||
| Finland | 11 545 | 2 380 | 1 668 | 1 141 | ||||
| Luxembourg | 11 130 | 1 750 | 1 330 | 1 190 | ||||
| Ireland | 11 053 | 3 500 | 2 450 | 1 400 | ||||
| Hungary | 4 375 | 700 | 700 | 1 050 | ||||
| Latvia | 2 695 | 840 | 700 | 350 | ||||
| Lithuania | 1 925 | 420 | 350 | 350 | ||||
| Estonia | 784 | 210 | 175 | 175 | ||||
| Total (GWth) | 13.45 | 2.10 | 1.43 | 1.14 | ||||
| * The relation between collector area and capacity is 1 m2 = 0.7 kWthermal | ||||||||
[edit] See also
- Solar gain
- Solar combisystem
- Solar furnace
- Renewable energy
- Renewable heat
- Seasonal thermal store
- Timeline of solar cells
- Wood pellets
[edit] References
- ^ 2005: Record year for investments in renewable energy REN21: Renewables Global Status Report 2006 Update, 18.7.2006, p. 21.
- ^ Solar Thermal Markets in Europe, Trends and market statistics 2006 European Solar Thermal Industry Federation ESTIF, June 2007, p. 4.
