Method and an installation for the air-conditioning of greenhouses and frames

• US 4,108,373 A
• Filed: 05/14/1975
• Issued: 08/22/1978
• Est. Priority Date: 05/22/1974
• Status: Expired due to Term

• Current Assignee: Commissariat a L'Energie Atomique (French Alternative Energies and Atomic Energy Commission), Institut National de La Recherche Agronomique
• Original Assignee: Commissariat a L'Energie Atomique (French Alternative Energies and Atomic Energy Commission), Institut National de La Recherche Agronomique
• Inventors: Damagnez, Jacques A., Denis, Pierre M., Jourdan, Paul, Chiapale, Jean-Pierre J.
• Primary Examiner(s): Wayner, William E.
• Application Number:
  US05/577,358
• Time in Patent Office: 1,196 Days
• Field of Search: 47/17, 237/1 A, 126/271, 52/2
• US Class Current: 126/640
• CPC Class Codes: A01G 9/243 Collecting solar energy in general F24S
• CPC Class Codes: Y02A 40/25 Greenhouse technology, e.g. cooling systems therefor
• CPC Class Codes: Y02P 60/12 using renewable energies, e.g. solar water pumping
• CPC Class Codes: Y10S 126/91 Heat storage liquid

Abstract

Solar radiations having longer wavelengths than those which are useful for plant development are selectively absorbed by an optical filter formed by two transparent walls which constitute at least part of the roofing structure of a greenhouse or "lean-to" frame and by a heat-transporting fluid which is circulated between the walls in a closed-circuit system. The heat absorbed is removed and stored in a separate reservoir, then recovered at night by pumping and circulating the fluid so as to maintain a predetermined minimum temperature within the greenhouse.

Claims

1. A method of day and night air-conditioning of an enclosure in which plants are cultivated, at least part of the roofing structure of said enclosure being made up of at least two walls transparent to solar radiation delimiting an intermediate space which is filled with a heat-transporting liquid, wherein:

(a) during the daytime, the penetration of the solar energy within said enclosure is selectively limited by making use of an optical filter constituted by said liquid containing an additive for selectively absorbing all radiant energy of wavelengths exceeding a threshold value that lies within the range of 6,000 A to 7,500 A and having no potential usefulness for the productivity and growth of the plants, at the same time permitting the greater part of the solar radiant energy that is ptotentially useful to green plants to be absorbed by the leaves of the plants under cultivation,

(b) during the daytime, the heat absorbed is removed by circulating said liquid in a closed circuit and is stored in a reservoir which is separate from the space formed between said walls,

(c) during the night, a minimum temperature is maintained within the enclosure by circulating said liquid within said intermediate space,

(d) measuring the radiative temperature of the plant cover within the enclosure,

(e) determining a top threshold value of a radiative temperature which is slightly lower than the maximum permissible limit and a bottom threshold value which is slightly higher than the minimum permissible limit, and

(f) circulating the heat-transporting liquid during the daytime as long as said radiative temperature exceeds said top threshold value and circulating the heat-transporting liquid during the night as long as said radiative temperature is lower than said bottom threshold value.

2. A method according to claim 1, wherein said liquid is water containing copper chloride in solution in preferably in a concentration of 25 g/l in respect of a depth of 1 cm of water.

3. A method according to claim 1, wherein said top threshold value is within the range of 25°

C to 30°

C and said bottom threshold value is within the range of 15°

C to 20°

C.

4. An installation for the plant temperature control by radiant energy in an enclosure in which plants are cultivated, wherein said installation comprises in combination on the one hand an enclosure in which at least part of said enclosure is comprised of at least two transparent to solar radiation walls delimiting at least one intermediate space filled with a heat-transporting liquid, said liquid containing an additive which operates to constitute an optical filter which absorbs radiant energy having a wavelength exceeding a threshold value lying within the range of 6,000 A to 7,500 A and having no usefulness for that growth of plants;

and on the other hand a closed circulating system for circulating heat-transporting liquid comprising said intermediate space or spaces, a heat-storage reservoir which is separate from said circulation system, and a pump means for determining a top threshold value of a radiative temperature which is slightly lower than the maximum permissible limit and a bottom threshold value which is slightly higher than the permissible limit, said pump circulating the heat-transporting liquid during the daytime as long as said radiative temperature exceeds the top threshold value and circulating the heat-transporting liquid during the night as long as the radiative temperature is lower than the bottom threshold value.

5. An installation according to claim 4, wherein said top threshold value is within the range of 25°

C to 30°

C. and said bottom threshold value is within the range of 15°

C to 20°

C.

6. An installation according to claim 4, wherein said pump is controlled automatically during the day and during the night by a radiative temperature transducer placed within said enclosure.

7. An installation for the plant temperature control by radiant energy in an enclosure in which plants are cultivated, wherein said installation comprises in combination on the one hand an enclosure in which at least part of said enclosure is comprised of at least two transparent to solar radiation wall delimiting at least one intermediate space filled with a heat-transporting liquid, said liquid containing an additive which operates to constitute an optical filter which absorbs radiant energy having a wavelength exceeding a threshold value lying within the range of 6,000 A to 7,500 A and having no usefulness for that growth of plants;

and on the other hand a closed circulation system for circulating heat-transporting liquid comprising said intermediate space or spaces, a heat-storage reservoir which is separate from said circulation system, and a pump.

8. An installation according to claim 7, wherein said liquid is water containing copper chloride in solution and preferably in a concentration of 25 g/liter in respect of a depth of 1 cm of water.

9. A method of day and night air-conditioning of an enclosure in which plants are cultivated, at least part of the roofing structure of said enclosure being made up of at least two walls transparent to solar radiation delimiting an intermediate space which is filled with a heat-transporting liquid, wherein:

during the daytime, the penetration of the solar energy within said enclosure is selectively limited by making use of an optical filter constituted by said liquid containing an additive for selectively absorbing all radiant energy of wavelengths exceeding a threshold value that lies within the range of 6,000 A to 7,500 A and having no potential usefulness for the productivity and growth of the plants, at the same time permitting the greater part of the solar radiant energy that is potentially useful to green plants to be absorbed by the leaves of the plants under cultivation,

during the daytime, the heat absorbed is removed by circulating said liquid in a closed circuit and is stored in a reservoir which is separate from the space formed between said walls,

during the night, a minimum temperature is maintained within the enclosure by circulating said liquid within said intermediate space.