FR2494554A1 - Agricultural greenhouse structure - involving both transparent and reflective plastics films to retain and distribute internal heat - Google Patents

Abstract

An agricultural greenhouse has multiple ridged panels mounted on a frame inclined at 15 deg. with the south end lower than the north end, the relative slopes of successive ridge faces being such as not to cause mutual shading. The structure also includes at least one internal blind to help conserve internal heat overnight. Pref. the northern faces of the ridges and the enclosure walls have an external layer of UV-stabilised polyethylene film sepd. by a few cm from an internal layer of aluminised polyester film such as 'Claryl' (RTM-Soc. Plastic Omnium). The internal blind, extended horizontally to trap warm air at lower levels, is pref. a film of EVA copolymer at least partly covered with a material to reflect infrared radiation back inwards. A pump system may be used to redirect warm air beneath the path of the cover to lower levels. The ridges may include vents which can be opened in summer. Typically the enclosures are inclined at angles of 60-80 deg. to the horizontal. The south faces of each ridge are inclined at 50 deg; The angle of the northern faces depends upon the local solar angle at the winter solstice.

Description

 The subject of the invention is a greenhouse, the thermal energy of which is supplied in all seasons by the sun, equipped with diurnal and nocturnal insulation means which can be used in winter, and with a heat storage system suitable for ensuring the minimum energy consumption.

 The greenhouse object of the invention is structured in such a way that it functions as a solar collector.

As shown in Figure 1, in section, it is oriented to the south, its south face (S) is of a height significantly lower than its north face (N), the transparent enclosure is covered with an equally transparent roof made up of a series of chapels (1,2,3) stepped, identical, making no reciprocal shadow, built on a frame, 4, making an angle of 150 with the horizontal
The south (S) and north (N) faces of the enclosure advantageously form an angle of 600 to 800 with the horizontal.

 The south faces of each chapel make an angle with the horizontal as open as possible, to present a good transmission of the solar flux, even when the sun is low. An angle close to 500 with the horizontal has been found suitable. The angle of 1-a North face of each chapel, with the horizontal, is calculated according to the height of the sun at the winter solstice. The chapels are constructed in such a way that they do not shade the neighboring chapels.

 All these transparent walls can be made of glass, or plastic, they are preferably made of low density polyethylene film resistant to UV rays.

 The roof in particular consists of such a polyethylene film, of determined width, fixed to the base of each chapel, 5, 6, 7, 8 on the frame 4, by any suitable system. A so-called "clip-on" clamping system between two sections 5 which fit into each other has proved particularly convenient.

 It is shown in Fig.2, in which we see the film, 2l, clamped between a gutter profile, 22, and an interior profile, 23, under the effect of the pressure exerted by a rubber or elastomer lining 24 .

This self-tightening system allows an installation
fast and safe.

A mechanical device makes it possible to set up
the film of each chapel without tension and adjust the
tension of the film according to the seasons. Masts 9, 10, 11
can move in translation along their axis - The
Figure 3, represents this device - The mast, 9, is threaded
on a determined length, 25, and it is guided by a
hollow tube, 26. A rotating mobile nut, 27, drives
e displacement in translation of the mast.

The north faces of the roof and the side faces of
the enclosure are permanently covered with a double
wall, 12, made of an outer polyethylene film
stabilized with Ultra-Violets and an inner film of aluminized polyester spaced a few centimeters apart, such as the material designated by the registered trademark "Claryl" of the Company
Plastic Omnium ~ - These sides have wooden cladding on which the reflective film is stapled.

 The double wall reduces heat losses by convection and, because it is reflective, losses by radiation.

On the north face inside the greenhouse are placed, in addition to the double wall, reflective panels
chissants, 13, made of alumi polyester film
nise whose orientation can be controlled, and which reflected
shine during the day the light incident on
plants.

In addition to these means of insulation useful during the day, a night isolation device is provided which consists of a horizontal reflective curtain, 14, removable, located
at a height of about 2.5 m. This curtain is made up
a plastic film support, such as a copolymer
ethylene vinyl acetate to which is bonded, on all or
part of this support a totally reflective material
in Infra-Red such as aluminized film, for example.

The criterion conditioning all these ISO devices
lation and reflection is the temperature of the plant and
not the air temperature.

 Indeed, placed in a totally reflecting space, the energy loss of plants by radiation is considerably reduced.

 The structure in tiered greenhouses allows to recover the hot air in the enclosure of the highest chapel, 3, which after having passed through the storage is reintroduced at ground level on the South face, the greenhouse and heats up in progressing along the different chapels. Another advantage of the reflective curtain is to limit the circulation of hot air, at night, to the space between the ground and the curtain which stops the movement of air near the roof of the greenhouse which makes the more efficient heating.

 The hot air circuit is shown diagrammatically in FIG. 4, where it can be seen that the hot air taken off at 31, during the day, passes through the fan 33 then through the storage 34 and is rejected at 36.

 At night for destocking, the hot air is taken at 32, below the reflecting curtain, heats up in the storage, 34, is optionally heated by the auxiliary system, 35, and exits at 36 on the south face.

 At night, if the storage is empty, the air taken off at, 32, goes directly to the auxiliary heating, thus passing the storage.

 Finally, the North and South faces are provided with openings ensuring the ventilation of the greenhouse - In summer, these openings remain permanently open.

Claims (9)

REVEN'DIC TIONS 1 - Greenhouse whose thermal energy is supplied in all seasons by the sun, characterized in that it is  consisting of a transparent enclosure including the South face,  is significantly lower in height than the North face,  also covered with a transparent roof  of a series of identical tiered chapels  carrying no shade, built on a frame making a  angle of 15 with the horizontal, and that it is equipped  day and night isolation means as well as a  heat storage system to reduce  at least the auxiliary energy. 2 - Greenhouse according to claim 1 characterized in that the  South faces of each chapel present with the horizon  spread an angle such as the transmission of the solar flux  is optimum and the north faces of each chapel are  an angle with the horizontal calculated according to the  height of the sun at winter solstice. 3 - Greenhouse according to claim 1 characterized in that the  North faces of the roof and the enclosure, as well as  side faces of the latter are covered in  permanence of a double wall made of a film  exterior in UV stabilized polyethylene  and a distant inner aluminized polyester film  a few centimeters. 4 - Greenhouse according to claim 1 characterized in that the  North face of the greenhouse is coated internally with  reflective panels, adjustable in film of  aluminized polyester. 5 - Greenhouse according to claim 1 characterized in that the i  night solation in winter is further improved by  the horizontal deployment of a reflective curtain,  blocking the circulation of hot air along the  chapels. 6 - Greenhouse according to claims 1 and 6 characterized in  what the reflective curtain consists of a  support in copolymer of vinyl acetate and ethylene  on which is glued on all or part of this support  a totally reflective material in the Infra Red. 7 - Greenhouse according to claim 1 characterized in that  circulation of hot air is ensured during the day  by removal from the highest chapel, passage  in the storage and discharge at the base of the South face. 8 - Greenhouse according to claim 1 characterized in that  at night for destocking, hot air is taken from the  under the reflective curtain, heated in the  storage, possibly in a backup system and  rejected at the base of the south face. 9 - Greenhouse according to claim 1, carautérisée in that  at night if the storage is empty the air taken from under  reflective curtain goes directly to heating  10 -Green according to claim 1 characterized in that  the north and south walls have openings  permanently in summer.