solar heating

Solar heating is the usage of solar energy to provide process, space or water heating. 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).

Other uses

Solar heating also refers to the heating of any objects, including buildings, cars, hats, 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 homeostasis 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.

Worldwide

Solar heating in Europe

See also

• Solar hot water
• Solar gain
• Solar combisystem
• Solar furnace
• Renewable energy
• Seasonal thermal store
• Solar design
• Timeline of solar cells
• Wood pellets‎

References

1. ^ 2005: Record year for investments in renewable energy REN21: Renewables Global Status Report 2006 Update, 18.7.2006
2. ^ Solar Thermal Markets in Europe, Trends and market statistics 2006 European Solar Thermal Industry Federation ESTIF, June 2007

Donate to Wikimedia