EVALUATION CRITERIA OF THERMIC TREND IN THE

EVALUATION CRITERIA OF THERMIC TREND IN THE

EVALUATION CRITERIA
CROPS
OF THERMIC TREND IN THE MEDITERRANEAN COVERED
S. P o r c e l l i
V e g e t a b l e Crops
Research I n s t i t u t e
P. 0 . Box 48
84098 PONTECAGNANO (SA)
Italy
R. D'Amore
V e g e t a b l e Crops
Research I n s t i t u t e
P. 0 . Box 48
84098 PONTECAGNANO (SA)
Italy
A b s t r a c t
A.A. r e p o r t on t h e b e h a v i o u r of t h r e e d i v e r s e V/S c u b a t u r e r a t i o s
t u n n e l s , covered by d i f f e r e n t p l a s t i c f i l m s : "Eva a n t i t a u , H o s t a f l o n
22, C o e x t r u s i o n s M u l t i e v a and M u l t i s o l a r , Calor 2C, Eva P a t i l u x and
PE, p r o v i d e d with p r o t e c t i o n systems f i t t o d e c r e a s e t h e r m i c l o s s e s :
thermic
screens,
double
wall,
hydrotunnel
and
double
walled
hydrotunnel".
The r e s u l t s o b t a i n e d d u r i n g t h e two-year p e r i o d of 1986-88 i n t h e
South of I t a l y , showed a p o s i t i v e t h e r m i c t r e n d f o r t u n n e l s with a
l a r g e r V/S c u b a t u r e r a t i o , covered by Eva and C o e x t r u s i o n p l a s t i c
f i l m s , equipped with some d e f e n c e systems a t low t e m p e r a t u r e s , such a s
t h e t h e r m i c s c r e e n e d h y d r o t u n n e l and t h e double w a l l e d h y d r o t u n n e l .
These s y s t e m s eployment and p a r t i c u l a r l y , t h e one of t h e double
w a l l e d h y d r o t u n n e l , c h a r a c t e r i z e d by a high t h e r m i c o u t p u t , a l l o w s t h e
meso and macrotherme w i n t e r c r o p s growth, even in t h e a g r i c u l t u r a l
a r e a s in the Northern Mediterranean b a s i n .
1.
Introduction
The need t o o b t a i n an e a r l y p r o d u c t i o n f o r many v e g e t a b l e c r o p s
and t o s a v e energy has promoted t h e development of means and of
p r o t e c t i v e t e c h n o l o g i e s a b l e t o f u l f i l the d i v e r s e
mediterranean
covered c r o p r e q u i r e m e n t s .
The g r e a t m e d i t e r r a n e a n l u m i n o s i t y and t h e l o v e r t h e r m i c minimum
w i n t e r f r e q u e n c y , l e t h a l t o t h e v e g e t a b l e c r o p s growth, s i n c e many
y e a r s , induced t h e V e g e t a b l e Crops Research I n s t i t u t e ,
to
carry
r e s e a r c h e s a b o u t t h e employment of cold t u n n e l s f o r e a r l y p r o d u c t i o n s
t r y i n g t o e x p l o i t t h e n a t u r a l e n e r g e t i c a l r e s o u r c e s and t o reduce t h e
thermic l o s s e s .
S e v e r a l p r o t e c t i v e systems f o r e a r l y or o u t of season y i e l d i n g s
were s e t u p .
Such
preparations
may
be
Acta H o r t i c u l t u r a e 281, 1990
Greenhouse C o n s t r u c t i o n , Design
groupped
into
two c a t e g o r i e s :
those
159
s u i t a b l e f o r e a r l y p r o d u c t i o n ( s e m i f o r c i n g ) and t h o s e s u i t a b l e f o r
extra seasonal output ( f o r c i n g ) .
To t h e f i r s t c a t e g o r y g e n e r a l l y b e l o n g , very symple p r o t e c t i o n s and
t u n n e l s , t o be employed f o r a long or s h o r t c y c l e t i m e : p o l y p r o p y l e n e
and p o l y e s t e r e non-woven s h e e t s layed d i r e c t e l y on t h e p l a n t s , small
tunnels, etc.
Such p r o t e c t i o n systems a r e mainly employed f o r microtherme v e g e t a b l e
c r o p s t h e y o n l y tend t o reduce t h e damages of n e g a t i v e e v e n t s or t o
s t r e n g t h e n some p o s i t i v e e n v i r o n m e n t a l e f f e c t s .
More c o m p l i c a t e d mouvable or f i x e d t u n n e l s b e l o n g i n g t o t h e second
c a t e g o r y have t o be employed d u r i n g a l l t h e c u l t u r a l p r o d u c t i v e c y c l e :
tunnels,
greenhouse t u n n e l s , with
3 m^ /1m^ of c u b a t u r e / s u r f a c e
r a t i o . In t h i s second t u n n e l c a t e g o r y , mainly s u i t a b l e f o r a l l t h e
meso and macrotherme v e g e t a b l e c r o p s , w i t h o u t any " a c t i v e " t h e r m i c
c o n d i t i o n i n g , some u r g e n t " p a s s i v e " t h e r m i c c o n d i t i o n i n g problems a r e
e v i n c e d , wich a r e u s e f u l t o c r e a t e t h e minimal s u r v i v i n g c o n d i t i o n s t o
t h e in p r o g r e s s c r o p s .
We may s t a t e t h a t between t h e non-woven f a b r i c s h e e t s layed on t h e
plants
and
the
wholly
computerized
greenhouses
exist
several
i n t e r m e d i a t e s o l u t i o n s which respond t h e v a r i o u s c u l t u r a l needs in
Southern I t a l y covered c r o p s .
The low " t h e r m i c i n e r t i a " t u n n e l s , l a c k i n g of some r e i n f o r c i n g
t h e r m i c s y s t e m s , t y p i c a l of t h e m e d i t e r r a n e a n h o r t i c u l t u r a l a r e a s ,
r e q u i r e s a c o n s t a n t and e x a c t e v a l u a t i o n of t h e i n s i d e r t h e r m i c
f l u c t u a t i o n s which depend d i r e c t l y from t h e o u t s i d e r
climatical
conditions.
2.
M a t e r i a l s and Methods
Aiming t o e v a l u a t e t h e d i f f e r e n t i n e r t i a l b e h a v i o u r of t e m p e r a t u r e
in t h e M e d i t e r r a n e a n a r e a ' s t u n n e l s , i n t h e t w o - y e a r p e r i o d 1986-1988
a t t h e V e g e t a b l e Crops Research I n s t i t u t e ,
v a r i o u s t u n n e l s were
equipped f o r t h e f o l l o w i n g o b s e r v a t i o n s :
a) t u n n e l s v o l u m e / s u r f a c e r e l a t i o n s h i p . I r o n s t r u c t u r e d t u n n e l s were
employed f o r t r i a l s having t h e f o l l o w i n g c u b a t u r e r a t i o s :
- small t u n n e l s with V/S = m3 1/m^ 1 r a t i o , made of c a r r y i n g
e l e m e n t s of 1 . 5 0 m wide and a t 1 . 3 0 m of r i d g e h e i g h t , p l a c e d
a t a d i s t a n c e of 2 m among them ( i n t e r a x i s ) ;
- medium t u n n e l s with V/S = m ^ / m ^ l r a t i o , made of c a r r y i n g
e l e m e n t s having a d i s t a n c e among them of a 2 m i n t e r a x i s and 5 m
w i d e , t h e r i d g e and t h e e a v e s h e i g h t b e i n g r e s p e c t i v e l y of 1 . 3 0
and 2 . 5 0 m;
- b i g t u n n e l s with V/S = m33/ir,2l made of
carrying
elements with
a 7.20 m width,
placed
at
a
distance
among them of 2 m,
t h e r i d g e and t h e e a v e s h e i g h t b e i n g r e s p e c t i v e l y of 3 . 6 0 and
1 . 6 5 m.
231»
b)
d i f f e r e n t c o v e r i n g m a t e r i a l s . Tunnels were
equipped with a
2 m3/1 m^ V/S r a t i o covered with t h e
following p l a s t i c films:
H o s t a f l o n 22 F l o u r i n e p l a s t i c f i l m a t long l i f e (10 y e a r s ) , Eva
antitau,
Eva P a t i l u x J
C o e x t r u s i o n M u l t i e v a 33, C o e x t r u s i o n
Multisolar
, Calor 2C and PE.
c) t h e r m i c l o s s e s r e d u c t i o n s y s t e m s . For t h i s purpose t u n n e l s were
equipped w i t h m ^ / m ? 1 V/S having t h e f o l l o w i n g d e f e n c e systems
from low t e m p e r a t u r e s :
- Simple EVA covered t u n n e l
(Test)
- Simple EVA c o v e r e d and p o l y p r o p y l e n e t h e r m i c s c r e e n e d t u n n e l
- EVA + EVA d o u b l e w a l l e d t u n n e l
- Simple EVA c o v e r e d h y d r o t u n n e l
- EVA covered h y d r o t u n n e l with an i n s i d e r p o l y p r o p y l e n e t h e r m i c
screen
- Double w a l l e d h y d r o t u n n e l
The s i m p l e EVA c o v e r e d hydrotunnel i s made up by a t u n n e l with a
PE r i g i d p i p e l i n e on t h e r i d g e - l i n e and with l a t e r a l h o l e s placed a t
a d i s t a n c e of 23 cm from which water f l o w s on t h e o u t s i d e r t u n n e l
walls.
The r a t e d p r e s s u r e f i x e d a t 0 . 5 - 1 atm. a l l o w s t h e water s p r u t i n g
with a volume of 0 . 8 1/min per pipe ml.
The t h r e s h o l d l i m i t f o r t u n n e l working has been s e t up around 4°C
( P o r c e l l i e t a l . , 1988)
Double w a l l e d h y d r o t u n n e l was s e t up in 1988 f o r c o u p l i n g t h e
p o s i t i v e e f f e c t s of both t h e systems t o o b t a i n a maximum c o v e r i n g
action (Figure 4 ) .
I t i s made up a s f o l l o w s : i n s i d e t h e s t a n d a r d t u n n e l a new one was
b u i l t up with t h e same shape but with a s m a l l e r volume so a s t o c r e a t e
a 50 cm a i r s p a c e between t h e two w a l l s .
On t h e i n s i d e r t u n n e l t o p a PE bd pipe (0 1" 1 / 2 ) was placed a t an
i n t e r m e d i a t e d i s t a n c e between both r i d g e s . I t was provided with
hydrodynamic m i c r o j e t a t t h e lower s i d e , placed a t a d i s t a n c e of 1.5m.
The equipment worked with very small w a t e r q u a n t i t y f l o w i n g
2 . 0 1/h per p i p e ml and was provided with a c l o s e d system of water
r e - g a t h e r i n g t h r o u g h some i n s i d e r eaves p i p e s p l a c e m e n t .
The f l o w i n g w a t e r was g a t h e r e d i n t o a tank i n t o which a sanked
electropump was p l a c e d f o r water r e c i r c u l a t i o n with 1 atm e x e r c i s e
pressure.
The
pump, c o n n e c t e d
with
a t h e r m o s t a t , s t a r t e d working when t h e
Reference
Porcelli,
S . , D'Amore R . , 1988 - Energy s a v i n g i n
mediterraneau
covered c r o p s with r e f e r e n c e t o d i f f e r e n t
tunnels
volume,
different
covering
materials
and
to
h o r t i c u l t u r a l c r o p s with s e v e r a l t h e r m i c a l n e e d s .
Acta H o r t i c u l t u r a e 230.
High t e c n o l o g y in P r o t e c t e d C u l t i v a t i o n .
231»
i n s i d e r t u n n e l t e m p e r a t u r e reached 15°C t h r e s h o l d value ( P o r c e l l i e t
a l . , 1989).
Thermic d a t a were c o n t i n u a l l y c a r r i e d o u t f o r each t r i a l u s i n g an
e l e c t r o n i c d r i l l s placed a t t h e some p l a n t h e i g h t and connected t o
d a t a l o g g e r and computer.
Tunnels were l a t e r a l l y opened when t h e i n s i d e r t e m p e r a t u r e reached
v a l u e s of a b o u t 18°C.
3.
Results
The minimum, maximum and average d a i l y t e m p e r a t u r e t r e n d r e c o r d e d
from 1 October 1988 t o 31 May 1987 showed some d i f f e r e n c e s f o r what
c o n c e r n s t h e t h r e e observed c u b a t u r e t h e r m i c t r e n d .
The minimum t e m p e r a t u r e t r e n d s of t h e c o n s i d e r e d p e r i o d have been,
f o r t h e s m a l l , medium and b i g s i z e d PE t u n n e l s , r e s p e c t i v e l y of
3.93°C,
5.3a°C,
6.36°C and of
5.18°C,
7.43°C,
7.98°C f o r Eva
covered t u n n e l s .
The maximum t e m p e r a t u r e s showed on i n v e r s e t r e n d with h i g h e r
v a l u e s f o r t h e small Eva covered t u n n e l s , w i t h t h e f o l l o w i n g v a l u e s :
3 4 . 2 5 , 30.87 and 27.28°C r e s p e c t i v e l y f o r t h e t h r e e V/S = 1 / 1 ; 2/1
and 3/1 c u b a t u r e s ( P o r c e l l i e t a l . ,
1 9 8 7 ) . By consequence
the
c o n s i d e r e d p e r i o d average t e m p e r a t u r e i n c r e a s e d a s we p a s s from l a r g e r
t o narrower V/S r a t i o t u n n e l s .
Such r e s u l t s c o n f i r m what has a l r e a d y been s t a t e d from p r e v i o u s
e x p e r i e n c e s on t u n n e l V/S r e l a t i o n s h i p , a s a b i g g e r a i r mass worked
like "thermic flywheel".
In g e n e r a l , i t i s p o s s i b l e c o n s i d e r t h a t t h e supposed t u n n e l
i n s i d e r t e m p e r a t u r e f o l l o w s a s i n u s o i d a l t r e n d depending by t h e d a i l y
and n i g h t l y t h e r m i c e x c u r s i o n , such v a r i a t i o n s a r e lower in t h e wider
t u n n e l s and h i g h e r i n t h e narrower o n e s .
The t h e r m i c e x c u r s i o n , become weaker and weaker, from w i n t e r t o
s p r i n g t i m e , while t h e average t u n n e l i n s i d e r t e m p e r a t u r e i s normally
growing. ( P o r c e l l i e t a l . , 1 9 8 5 ) .
References
P o r c e l l i , S . , D'Amore R., 1989 - Un nuovo i d r o t u n n e l con e l e v a t o
e f f e t t o t e r m i c o . C o l t u r e p r o t e t t e , n . 6, g i u g n o .
Porcelli,
S . , D'Amore R . , e t a l 1987 - C o l t i v a z i o n e in ambiente
p r o t e t t o d i p i a n t e o r t i c o l e micro-meso e macroterme
a l t e r n a t i v e a l l e Solanacee.
R e l a z i o n e C.E.E.-AGR1MED ( i n c o r s o ) .
P o r c e l l i , S . , D'Amore R., P e t r a l i a S . , Monopoli F . P . , 1985
Apprestamenti per l a s e m i f o r z a t u r a o per l a p r o t e z i o n e
temporanea. I t a l i a A g r i c o l a (Gennaio - Marzo).
231»
The t h e r m i c t r e n d s r e c o r d e d from 1 October 1986 t o 31 May 1987 and
r e f e r r e d t o open a i r and t o t u n n e l s with a V/S = 2/1 r a t i o , covered
with H o s t a f l o n 22, C o e x t r u s i o n s Multieva 33 and M u l t i s o l a r , Calor 2C,
Eva a n t i t a u , Eva P a t i l u x and PE showed a b e t t e r Eva a n t i t a u t h e r m i c
o u t p u t with minimum t e m p e r a t u r e s average v a l u e s , d u r i n g t h e c o n s i d e r e d
time of 8 . 7 6 ° C , i t was f o l l o w e d by H o s t a f l o n 22 and by Calor 2C, with
t e m p e r a t u r e s r e s p e c t i v e l y of 8.49°C and 7.82°C.
As f o r t h e maximum t e m p e r a t u r e of t u n n e l s covered with EVA a n t i t a u
and P a t i l u x , H o s t a f l o n 22, Calor 2C, t h e y showed a t h e r m i c t r e n d with
an average s u p e r i o r t o t h e o t h e r c o v e r i n g f i l m s whose maximum v a l u e s
have o f t e n reached and exceeded 35°C d u r i n g t h e time of April-May
1987. ( P o r c e l l i e t a l . , 1 9 8 7 ) .
The d e f e n c e s y s t e m s a t low t e m p e r a t u r e s employed d u r i n g t h e t r i a l s
meant t o o b s t r u c t or t o reduce in v a r i o u s ways t h e o u t s i d e r h e a t
l o s s e s , r e d u c i n g t h e c o n d u c t i o n - c o n v e c t i o n exchanges a n d / o r c r e a t i n g a
c o v e r i n g opaqueness a t t h e long l . R .
In f i g u r e s 1, 2 and 3 t h e minimum d a i l y t e m p e r a t u r e t r e n d s
r e c o r d e d in Pontecagnano - S a l e r n o ( l a t . 40° 3 7 ' ) from February 24 t o
March 23, 1987 a r e compared f o r t h e f o l l o w i n g t e s t s : open a i r , EVA +
EVA double w a l l e d t u n n e l with an i n t e r s t i c e of 5 cm, s i n g l e t u n n e l
covered w i t h Eva f i l m ( t e s t ) , p o l y p r o p y l e n e (PP) t h e r m i c s c r e e n e d
t u n n e l , s i m p l e h y d r o t u n n e l and f i n a l l y t h e p o l y p r o p y l e n e (PP) t h e r m i c
s c r e e n e d h y d r o t u n n e l . From t h e g r a p h i e s , we may n o t i c e t h a t t h e simple
t u n n e l ( t e s t ) showed a d a i l y t h e r m i c minima s i m i l a r t o t h e open a i r ,
with lower v a l u e s of a b o u t -5°C, t h e s e v a l u e s e i t h e r f o r t h e season
time and f o r t h e g e o g r a p h y c a l p o s i t i o n r e s u l t e d t o be e x c e p t i o n a l .
C l e a r l y h i g h e r t h e r m i c a l o u t p u t were given by t h e double walled
t u n n e l and by t h e p o l y p r o p y l e n e t h e r m i c s c r e e n e d t u n n e l .
Only f o r one time such t e s i s showed minimum d a i l y t e m p e r a t u r e of
- 0 . 5 ° C i n any way t h i s t h e r m i c t r e n d may r e s u l t t o be l e t h a l f o r many
meso and macrotherme v e g e t a b l e c r o p s .
Thermic t r e n d s c l e a r l y s u p e r i o r t o 0°C were e i t h e r given by t h e
s i m p l e h y d r o t u n n e l and by t h e PP t h e r m i c s c r e e n e d
hydrotunnel,
t h e r e f o r e , t h i s l a s t one has never given minima lower t h a n 2°C.
The o p p o r t u n i t y t o "equip more or l e s s s o f i s t i c a t e d t u n n e l s , a b l e
t o g i v e e a r l y or o u t of season y i e l d i n g s , depends e i t h e r by a good
c l i m a t i c a l environment and by t h e b i o l o g i c a l ,
physiological
and
e n e r g e t i c a l needs of v e g e t a b l e c r o p s .
In 1988 a double w a l l e d h y d r o t u n n e l with w a t e r r e c i r c u l a t i o n was
s e t up f o r t h e impruvement of t h e t u n n e l t h e r m i c o u t p u t .
Hourly t h e r m i c t r e n d r e g i s t e r e d d u r i n g t h e n i g h t of 1 6 - 1 7 / 2 / 8 8
Reference
P o r c e l l i , S . , O'Amore R . , e t a l . , 1987
C o l t i v a z i o n e in ambiente p r o t e t t o d i p i a n t e o r t i c o l e
tnicro-meso e macroterme a l t e r n a t i v e a l l e S o l a n a c e e .
R e l a z i o n e C.E.E.-AGRIMED ( i n c o r s o ) .
231»
showed a double w a l l e d h y d r o t u n n e l minimum t e m p e r a t u r e of 6°C with a
very good t h e r m i c d e v i a t i o n of t h e T5? min. of 2 . 8 ; 5 . 7 and 8.5°C
r i s p e c t i v e l y f o r t h e h y d r o t u n n e l , t h e s i m p l e t u n n e l and f o r t h e open
a i r (Figure 5 ) .
As f o r t h e q u a n t i t y of water in r e c i r c u l a t i o n , i t has been n o t i c e d
t h a t with a system working a p p r o x i m a t i v e l y f o r 12 h o u r s , only 25 water
I t . per ml of p i p e - l i n e were d e l i v e r e d .
4.
Conclusions
From t h e undertaken t r i a l s , we n o t i c e d t h a t in many c a s e s t h e
i t a l i a n covered v e g e t a b l e crop shows, s t r u c t u r a l and t e c h n o l o g i c a l
features typical
of t h e m e d i t e r r a n e a n
environment
through
the
employment of v a r i o u s l y s i z e d t u n n e l s , of v a r i o u s c o v e r i n g m a t e r i a l s
and with t h e use of c o v e r i n g systems f o r a maximum e x p l o i t m e n t of t h e
n a t u r a l e n e r g e t i c a l r e s o u r c e s . R e s u l t s o b t a i n e d from t h e
thermic
e x c u r s i o n t e s t s f o r t h o s e t u n n e l s w i t h a d i f f e r e n t c^jbature r a t i o ,
showed t h e need t o employ V/S v a l u e s around 2 . 5 - 3 m /im
particularly
i n t h e s o u t h e r n l a t i t u d e s and f o r t h e more s p r e a d m i c r o , meso and
macrotherme v e g e t a b l e c r o p s .
As f o r t h e s i n g l e c o v e r i n g m a t e r i a l , t h e minimum t e m p e r a t u r e t r e n d
gave t h e chance t o employ a l s o some new m a t e r i a l s such a s : H o s t a f l o n
22 and t h e two C o e x t r u s i o n s M u l t i s o l a r and M u l t i e v a 33. These l a s t two
showed lower maximum t e m p e r a t u r e v a l u e s d u r i n g t h e s p r i n g t i m e , when
t u n n e l i n s i d e r t e m p e r a t u r e was g e t t i n g h i g h e r , a s a m a t t e r of f a c t ,
t e m p e r a t u r e v a l u e s h i g h e r t h a n 32°C d e p r e s s t h e v e g e t a b l e
crop
photosynthetic process.
The p o s s i b i l i t y t o employ, d u r i n g t h e w i n t e r , p r o t e c t i o n systems
a l t e r n a t i v e t o t h o s e equipped with t h e t r a d i t i o n a l h e a t i n g system i s
f o r t h e m e d i t e r r a n e a n v e g e t a b l e c r o p a new e v a l u a t i o n .
The high hydrotunnel t h e r m i c o u t p u t , p a r t i c u l a r l y t h e double
w a l l e d one, a l l o w s meso and macrotherme v e g e t a b l e crop forcing and may
promote t h e w i n t e r covered c r o p s y i e l d i n g a l s o f o r t h e c o o l e r
a g r i c u l t u r a l a r e a s of t h e M e d i t e r r a n e a n c o u n t r i e s .
231»
Figure
1 - 4 D i f f e r e n t environments,
daily m i n i m u m
T e m p e r a t u r e , 24/2 - 24/3/1987
a Open air O D o u b l e walled A Tunnel EVA x Tunnel EVA
EVA and EVA
(Test)
and PP T . S c r .
K
t
^A
N
Figure
2 - Idrotunnel , daily m i n i m u m T.24/2 - 24/3/1987
A
Figure
Particular
4 - D o u b l e w a l l e d i d r o t u n n :1 scheme.
Legend
1 Water entrance
6 Eaves
2 Tank
7 Thermosta t
3 Pump w i t h float
8 Back p i p e l i n e
Water pipeline
9 E x t e r n a l tunnel
S Jet *
10 I n t e r n a l tunnel
* Type G o - G o - j et 0 (360° w i t h m a r b l e )
hours
Figure
5 - Hourly Minimum Temperature
16-17/2/1988
Open air
Tunnel ( T e s t )
231»
In 4
Environments,
Idrotunnel
Double walled
idrotunnel