Article. Energy in fokus - from Kyoto to Copenhagen. - AgroTech

agrotech.dk

Article. Energy in fokus - from Kyoto to Copenhagen. - AgroTech

Eva Rosenqvist 1 , Anker Kuehn 2 , Jakob Skov Pedersen 2 , Per Holgersson 3 and Hans Andersson 3

1 Dept. of Agriculture and Ecology, University of Copenhagen, Højbakkegård Allé 9, 2630 Tåstrup, Denmark, ero@life.ku.dk

2 Agrotech, Højbakkegård Allé 21, 2630 Tåstrup, Denmark, 3 AB Ludvig Svensson, 511 82 Kinna, Sweden

The effect of screen material

on air and leaf temperature

The present development of greenhouse

production is much focused on new

climate control strategies and new technical

solution for energy management.

Here the development of new screen

material will play an important role since

the screens have a great impact on both

the micro climate experienced by the crop

and the temperature distribution in the

greenhouse, which will be important for

the possibilities for heat extraction aiming

at storing energy harvested during warm

periods of time for use during cold periods

of time.

In an experiment run during June – September

2009 we have compared radiation

and temperature parameters under three

permanently closed screens: (1) a traditional

ventilated screen with one aluminium

strip, on clear transparent strip and two

open strips, (2) a dense prototype of NIR

screen, with clear strips that transmits less

near infra-red radiation than the traditional

transparent strips does and (3) a dense

diffusing screen with one white and two

diffusing transparent strips. Each screen

was sewn into a tent measuring 1.8 x 6.2

m, being 1.2 m high to the south and 1.6

m high to the north, towards the wall (fig.

1). In the tents and (4) on a control bench

without any screen the following climate

parameters were measured; global radiation,

photosynthetic active radiation (PAR),

air temperature and leaf temperature by

four thermocouples inserted into the leaves.

The leaf temperature was measured

on Chrysanthemum, pot roses, Begonias

and Kalanchoë.

Data from June show that the three

permanent screens decrease the global

radiation by 33–36 %, i.e. they all have

comparable filtration in the spectral range

of 400–1100 nm. In the PAR region screen

1 and 3 removes 27–30 % of the light

while the NIR screen (2) only removes

19 % of the light thus potentially increasing

the rate of photosynthesis in the

crop compared to the other screens. The

screens decreased the mean air temperature

in the range 0.3–0.9 °C while the

mean leaf temperature of Chrysanthemum

only varied with +/- 0.3 °C i.e. the effects

of the different screens on the two mean

temperature parameters were limited. It

should be kept in mind, though, that the

screens were permanently on and not

ventilated more that what the screen material

itself allowed. However, when looking

at the daily temperature course several

interesting patterns are revealed where

the screens can decrease the leaf temperature

with up to 5 °C, compared to the

control, and these differences and the

effect of the various screen materials will

be shown and discussed.


Fig. 1. The experimental setup in a greenhouse at University of Copenhagen, Tåstrup. From left are screen (1) a traditional

ventilated screen with one aluminium strip, on clear transparent strip and two open strips, (2) a dense prototype of NIR

screen, with clear strips that transmits less near infra-red radiation than the traditional transparent strips does, (3) a dense

diffusing screen with one white and two diffusing transparent strips and (4) a control bench to the east without any screen.

ENERGY IN FOCUS 51

More magazines by this user
Similar magazines