Design of Air Distribution Systems for Closed Greenhouses

Wells, Colin; Amos, N.

doi:10.17660/actahortic.1994.361.8

Cited by 11 publications

(6 citation statements)

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“…Centralised ACU, perhaps serving 1,000 m 2 , are usually located at the gable-ends, extract warm air from the greenhouse and cool it with cold water from the aquifer. The cold air is often distributed in the greenhouse by means of perforated polyethylene ducts underneath the crop Wells and Amos, 1994). The main difference between these systems and cooling via ventilation openings in the cover is that the cold air is now entering in the lower part of the greenhouse, causing stratification of the air and resulting in vertical temperature gradients.…”

Section: Temperature Distributionmentioning

confidence: 99%

An overview of climate and crop yield in closed greenhouses

Gelder¹,

Dieleman²,

Bot³

et al. 2012

The Journal of Horticultural Science and Biotechnology

103

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The closed greenhouse is a recent innovation in the horticulture industry. Cooling by ventilation is replaced partly (in semi-closed greenhouses) or completely (in closed greenhouses) by mechanical cooling. Excess solar energy is collected and stored to be reused to heat the greenhouse. In temperate climates, this concept combines improved crop production with energy savings. This paper presents an overview of climate, crop growth and development, and crop yield in closed and semi-closed greenhouses. The technical principles of a closed greenhouse are described and the macroclimate and microclimate arising from this are studied. The consequences of the typical growth conditions found in closed greenhouses for crop physiology and crop yield are examined. Finally, the experiences of commercial growers are presented. In temperate climates, closed greenhouses can reduce the use of fossil fuel-derived energy by 25 -35%, compared with open greenhouses. With high global radiation, the climate in closed greenhouses is characterised by high CO 2 concentrations, high air humidity, improved temperature control, and a vertical temperature gradient. An annual increase in production of 10 -20% is realistic, with reduced amounts of supplied CO 2 . The yield increase is primarily obtained through increased rates of photosynthesis due to the higher CO 2 concentrations in closed greenhouses. To introduce this innovation into practice, knowledge transfer was a key factor for its implementation and the realisation of increased production levels. Future trends will require minimising the use of fossil fuels and increasing the level of control of the production process. Closed and semi-closed greenhouses fit seamlessly into this trend as they allow for a more controlled climate and higher levels of production, combined with savings in fossil fuel use.

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Section: Temperature Distributionmentioning

confidence: 99%

An overview of climate and crop yield in closed greenhouses

Gelder¹,

Dieleman²,

Bot³

et al. 2012

The Journal of Horticultural Science and Biotechnology

103

View full text Add to dashboard Cite

show abstract

“…The length of the tube depends on the length of the building, and if the building is more than 30 m long it may be advisable to have two, dead-ended tubes running back-to-back, and have both tubes fitted with their own fan located on each end of the building (Wells and Amos 1994). If a bend is required to better position the tube over a pen, the bend should be as minimal as possible.…”

Section: Tubementioning

confidence: 99%

Ensuring optimal ventilation of calf buildings

Halbach¹,

Robertson²

2021

In Practice

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Background: There has been considerable change over the past 10 years in the perceived value of beef and dairy calves, with potential for improvement to animal health and farm financial sustainability. One of the main calf health issues is respiratory disease, with multifactorial aspects that all require attention in order to produce healthy calves. Poor ventilation is often cited as a contributing factor to respiratory problems on specific farms, but it is seldom described in an objective manner that would facilitate providing an effective solution.Aim of the article: This article outlines the importance of fresh air in calf houses on calf health, with specific focus on natural ventilation, stack effect and positive pressure tube ventilation.

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“…1 When properly designed, PPTV systems aim to provide a uniform distribution of air throughout the barn, without creating a draft on the calf. 3,4 Mathematical formulas factoring in several variables were used to develop a spreadsheet for designing and analyzing PPTV systems in calf facilities. This Excel spreadsheet was developed by the University of Wisconsin Dairyland Initiative and is available for use by trained consultants.…”

Section: Introductionmentioning

confidence: 99%

“…The spreadsheet ensures that the fan's static pressure and tube's discharge coefficient and aperture ratio are at the desired levels to ensure that air volume and velocity are similar at every hole on the tube and the fan is performing as expected while under the load of the tube. 3 Veterinary practitioners need to be aware that housing calves and heifers in a barn, particularly in larger groups, is a risk factor for BRD at least partially due to an increase in bacterial air counts and other noxious agents. Even if the practitioner is not proficient in designing PPTV systems, they need to be able to recommend in what situations a system will improve respiratory health and to identify when existing systems are not functioning properly.…”

Section: Introductionmentioning

confidence: 99%

What every practitioner should know about calf barn ventilation

Practitioners¹

2020

American Association of Bovine Practitioners Proceedings of the Annual Conference

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Bovine respiratory disease (BRD) is financially significant to a dairy operation due to treatment costs, veterinary costs, loss of replacements, and reduced future production potential. High air bacterial counts have been shown to increase incidence of respiratory disease. Positive pressure tube ventilation systems aim to reduce air bacterial counts and noxious agents by driving fresh, outside air to the microenvironment of the calf. It is important for dairy practitioners to understand the basics of these systems so that they can make recommendations or troubleshoot problems.

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Design of Air Distribution Systems for Closed Greenhouses

Cited by 11 publications

References 0 publications

An overview of climate and crop yield in closed greenhouses

An overview of climate and crop yield in closed greenhouses

Ensuring optimal ventilation of calf buildings

What every practitioner should know about calf barn ventilation

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