Mapping methane sources in Paris

A potent greenhouse gas, methane is released by many sources, both human and natural. Large cities emit significant amounts of methane, but in many cases the exact emission sources are unknown. Now, researchers reporting ...

Organic farming could feed Europe by 2050

Food has become one of the major challenges of the 21st century. According to a study carried out by CNRS scientists, an organic, sustainable, biodiversity-friendly agro-food system, could be implemented in Europe and would ...

Sweet sorghum promising for the environment

Sweet sorghum can be used to produce biogas, biofuels, and novel polymers. In addition, it can help replace phosphate fertilizers. A new sweet sorghum variety developed at Karlsruhe Institute of Technology (KIT) accumulates ...

Should ships in India switch to shore power?

Countries throughout Europe and North America require ships, when in port, to be attached to the shore-based power grid to prevent them from running their own engines and generating harmful emissions right on the city's doorstep. ...

page 1 from 40

Greenhouse

A greenhouse (also called a glasshouse) is a building in which plants are grown. These structures range in size from small sheds to very large buildings. A miniature greenhouse is known as a cold frame.

A greenhouse is a structure with different types of covering materials, such as a glass or plastic roof and frequently glass or plastic walls; it heats up because incoming visible solar radiation (for which the glass is transparent) from the sun is absorbed by plants, soil, and other things inside the building. Air warmed by the heat from hot interior surfaces is retained in the building by the roof and wall. In addition, the warmed structures and plants inside the greenhouse re-radiate some of their thermal energy in the infra-red, to which glass is partly opaque, so some of this energy is also trapped inside the glasshouse. However, this latter process is a minor player compared with the former (convective) process. Thus, the primary heating mechanism of a greenhouse is convection. This can be demonstrated by opening a small window near the roof of a greenhouse: the temperature drops considerably. This principle is the basis of the autovent automatic cooling system. Thus, the glass used for a greenhouse works as a barrier to air flow, and its effect is to trap energy within the greenhouse. The air that is warmed near the ground is prevented from rising indefinitely and flowing away.

Although there is some heat loss due to thermal conduction through the glass and other building materials, there is a net increase in energy (and therefore temperature) inside the greenhouse.

Greenhouses can be divided into glass greenhouses and plastic greenhouses. Plastics mostly used are PEfilm and multiwall sheet in PC or PMMA. Commercial glass greenhouses are often high tech production facilities for vegetables or flowers. The glass greenhouses are filled with equipment like screening installations, heating, cooling, lighting and may be automatically controlled by a computer.

This text uses material from Wikipedia, licensed under CC BY-SA