GREEN

HOUSE

greenhouse

A greenhouse (also called a glasshouse) is a building where plants are grown These structures range in size from small sheds to very large buildings A miniature greenhouse isknown as a

cold frame

greenhouse

A greenhouse (also called a glasshouse) is a building where plants are grown These structures range in size from small sheds to very large buildings A miniature greenhouse isknown 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

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 orflowers The glassgreenhouses are filled with equipment like screening installations heatingcooling lighting

and may be automatically controlled by a computer

UsesGreenhouses protect crops from too much heat or cold shield plants from dust storms and blizzards and help to keep out pests Light and temperature control allows greenhouses to turn inarable land into arable land there by improving food production in marginal environments

Because greenhouses allow certain crops to be grown throughout the year greenhouses are increasingly important in the food supply of high latitude countries One of the largest greenhouse complexes in the world is in Almeria Spain where greenhouses cover almost 50000 acres (200 km2) Sometimes called the sea of plastics

Greenhouses are often used for growing flowers vegetables fruits and tobacco plants Bumblebees are the pollinators of choice for most greenhouse pollination although other types of bees have been used as well as artificial pollination Hydroponics can be used in greenhouses as well to make the most use of the interior space

Besides tobacco many vegetables and flowers are grown in greenhouses in late winter and early spring and then transplanted outside as the weather warms Started plants are usually available for gardeners in farmers markets at transplanting time Special greenhouse varieties of certain crops such as tomatoes are generally used for commercial production

The closed environment of a greenhouse has its own unique requirements compared with outdoor production Pests and diseases and extremes of heat and humidity have to be controlled and irrigation is necessary to provide water Significant inputs of heat and light may be required particularly with winter production of warm-weather vegetables

Because the temperature and

humidity of greenhouses must

be constantly monitored to ensure optimal conditions a

wireless sensor network can be

used to gather data remotely The data is transmitted to a

control location and used to control

heating cooling and irrigation

systems

HistoryThe idea of growing plants in

environmentally controlled areas has existed since Roman times The Roman emperor Tiberius ate a cucumber-like[2] vegetable daily The Roman gardeners used artificial methods (similar to the

greenhouse system) of growing to have it available for his table every day of the

year Cucumbers were planted in wheeled carts which were put in the sun daily then taken inside to keep them warm at night

The cucumbers were stored under frames or in cucumber houses

glazed with either oiled cloth known as specularia or with sheets of selenite (aka lapis specularis)

according to the description by Pliny the Elder

The first modern greenhouses were built in Italy in the 13th century[5] to

house the exotic plants that explorers brought back from the

tropics They were originally called giardini botanici (botanical gardens) The concept of greenhouses soon

spread to the Netherlands and then England along with the plants

Some of these early attempts required enormous amounts of work to close up at night or to winterize There were serious problems with providing adequate and balanced heat in these early greenhouses Today the Netherlands has many of the largest greenhouses in the world some of them so vast that they are able to produce millions of vegetables every year

The Netherlands

The Netherlands has some of the

largest greenhouses in

the world Such is the scale of food production in the country that in

2000 greenhouses

occupied 10526 hectares or

025 of the total land area of the

Netherlands

Greenhouses began to be built in the Westland area of the Netherlands in the mid-nineteenth century The addition of sand to bogs and clay soil created fertile soil for agriculture and around 1850 grapes were grown in the first greenhouses simple glass constructionswith one of the sidesconsisting of solid wall By the early 20th century greenhouses began to be constructed of nothing but glass and they began tobe heated

The Netherlands

The Netherlands has some of the

largest greenhouses in

the world Such is the scale of food production in the country that in

2000 greenhouses

occupied 10526 hectares or

025 of the total land area of the

Netherlands

Greenhouses began to be built in the Westland area of the Netherlands in the mid-nineteenth century The addition of sand to bogs and clay soil created fertile soil for agriculture and around 1850 grapes were grown in the first greenhouses simple glass constructionswith one of the sidesconsisting of solid wall By the early 20th century greenhouses began to be constructed of nothing but glass and they began tobe heated

Greenhouses began to be built in the Westland area of the Netherlands in the mid-nineteenth century The addition of sand to bogs and clay soil created fertile soil for agriculture and around 1850 grapes were grown in the first greenhouses simple glass constructionswith one of the sidesconsisting of solid wall By the early 20th century greenhouses began to be constructed of nothing but glass and they began tobe heated

This also allowed for the production of fruits and vegetables that did not ordinarily grow in the area Today the Westland and the area around Aalsmeer have the highest concentration of greenhouse agriculture in the world The Westland produces mostly vegetables besides plants and flowers Aalsmeer is noted mainly for the production of flowers and potted plants Since the twentiethcentury the area aroundVenlo (in

Limburg) and parts of Drenthehave also become important regions for greenhouse agriculture