Articles
Evaluation of performances of new vapour-permeable material as energy saving screens for greenhouse towards sustainable environmental controls
Article number
1437_15
Pages
111 – 118
Language
English
Abstract
An energy saving screen plays a key role in improving heat insulation of a greenhouse and energy efficiency under heating.
In general, screens are closed when a greenhouse is heated up in winter nights.
Transparent screens can be closed also during very cold daytime hours.
However, vapour accumulates as well, and finally high humidity and condensation will occur by closing screens.
In order to avoid these effects, a screen will be opened slightly for a short time or will have small holes or gaps on itself to discharge excessive vapour.
Discharging vapour (latent heat) will in these cases come together with uncontrolled loss of sensible heat (by air transport), thus energy-saving is decreased.
In order to solve this problem, we evaluated the performances of new vapour-permeable films which can transmit vapour without air transport and decouple latent heat release from air transport, thus potentially from sensible heat loss in greenhouse application.
Six types of transparent films, 2 vapour-permeable films with thicknesses of 80 µm (FJ80) and 130 µm (FJ130), 3 perforated films with 20×20 cm (AC20), 15×15 cm (AC15), 10×10 cm (AC10) perforation holes of ca. 6 mm diameter, and 1 traditional knitted screen (LS), were compared in 2 repetitions.
Twelve boxes covered with the different materials were set in the greenhouse as experimental plots.
Environmental conditions inside every box and the greenhouse were measured.
First, all boxes were filled with high concentration CO2 and the decay of CO2 was measured to analyse the air permeability of each material.
The CO2 permeabilities were FJ130 < FJ80 < AC20 < AC15 < AC10 < LS from low to high, thus new vapour-permeable films can decrease CO2 loss.
Second, the same number of potted plants were installed into every box as source of vapour (H2O) and the effects of vapour permeability on each material were investigated.
The level of both relative and absolute humidity of FJ130 was similar to AC20 as well as FJ80 was close to AC10. LS had the lowest humidity of all boxes.
These results showed that new vapour-permeable films (FJ130 and FJ80) indeed decouple vapour release from air and CO2 transport.
There is a potential to be able to improve energy efficiency under closing screens without problems of high humidity and condensation by installing the new films in the future.
In general, screens are closed when a greenhouse is heated up in winter nights.
Transparent screens can be closed also during very cold daytime hours.
However, vapour accumulates as well, and finally high humidity and condensation will occur by closing screens.
In order to avoid these effects, a screen will be opened slightly for a short time or will have small holes or gaps on itself to discharge excessive vapour.
Discharging vapour (latent heat) will in these cases come together with uncontrolled loss of sensible heat (by air transport), thus energy-saving is decreased.
In order to solve this problem, we evaluated the performances of new vapour-permeable films which can transmit vapour without air transport and decouple latent heat release from air transport, thus potentially from sensible heat loss in greenhouse application.
Six types of transparent films, 2 vapour-permeable films with thicknesses of 80 µm (FJ80) and 130 µm (FJ130), 3 perforated films with 20×20 cm (AC20), 15×15 cm (AC15), 10×10 cm (AC10) perforation holes of ca. 6 mm diameter, and 1 traditional knitted screen (LS), were compared in 2 repetitions.
Twelve boxes covered with the different materials were set in the greenhouse as experimental plots.
Environmental conditions inside every box and the greenhouse were measured.
First, all boxes were filled with high concentration CO2 and the decay of CO2 was measured to analyse the air permeability of each material.
The CO2 permeabilities were FJ130 < FJ80 < AC20 < AC15 < AC10 < LS from low to high, thus new vapour-permeable films can decrease CO2 loss.
Second, the same number of potted plants were installed into every box as source of vapour (H2O) and the effects of vapour permeability on each material were investigated.
The level of both relative and absolute humidity of FJ130 was similar to AC20 as well as FJ80 was close to AC10. LS had the lowest humidity of all boxes.
These results showed that new vapour-permeable films (FJ130 and FJ80) indeed decouple vapour release from air and CO2 transport.
There is a potential to be able to improve energy efficiency under closing screens without problems of high humidity and condensation by installing the new films in the future.
Publication
Authors
T. Asai, C. Stanghellini, D. Katzin, B. Van Breugel, V. Mohammadkhani, S. Hemming
Keywords
screen, humidity control, insulation, energy efficiency, greenhouse
Online Articles (57)