2011 International Conference on Alternative Energy in Developing Countries and Emerging Economies
- 294 -
Fig. 3 shows the temperature of working fluid in a
representative day of winter. It was found that before air
flowing into ETS, the inflow temperature was lower than
air temperature in the model GH by the range of 0 - 6
o
C.
This was a result of heat generated from air energy loss
by the friction and pressure drop through the suction tube.
When the air moved into the underground and transferred
heat to soil, air temperature could decrease by about 0 - 4
o
C from 11 a.m. to 3 p.m. thus the temperature of model
GH was lower than that of non-cooling condition.
10
15
20
25
30
35
40
45
6:00AM
7:00AM
8:00AM
9:00AM
10:00AM
11:00AM
12:00PM
1:00PM
2:00PM
3:00PM
4:00PM
5:00PM
6:00PM
Air Temperature
(
0
C)
Time (hr)
modelGH controlGH ambient
Fig. 4. The variation of temperature changes for model GH, control GH
and surrounding in a typical day of winter.
Fig. 4 shows the temperature changes inside the model
GH, control GH and surrounding from 6 a.m. to 6 p.m.
Due to the influence of solar radiation and accumulative
heat in the GH, the inside temperature was high
obviously except in the morning and evening. Both inside
temperatures and ambient air were similar. At 2 p.m. the
maximum temperature of the model GH with the ETS
was 39.39
o
C, while the temperature inside control GH
was equal to 40.47
o
C and ambient temperature was 32
o
C
respectively. When considering the operation time, the
ETS could reduce the temperature from 11 a.m. to 4 p.m.
by at least 0 - 3
o
C. However, from 8 a.m. to 9 a.m. the
model GH had received heat from ETS while the control
GH got a shadow from the nearby trees, accordingly the
control GH temperature was lower than the model GH.
From 4 p.m. to 6 p.m., as a result of the model GH
getting a shadow from the nearby GH, the model GH
temperature had decreased rapidly and was lower than
control GH by the range of 2 - 4
o
C.
Fig. 5 shows the RH changes in the model GH, control
GH and surrounding since 6 a.m. to 6 p.m. The
characteristic of RH changes inside both GHs were in a
same trend due to the variation of solar radiation,
moisture content from condensation of water vapor on
plastic walls and the occurrence of fog in the morning.
From 10 a.m. to 6 p.m. the ETS could maintains RH to be
higher than control GH by approximately 0 - 10 %. In the
evening, the RH was higher than control GH by
maximum 12 %. The measured RH of the model GH was
27.35 % at 2 p.m. while the control RH was lowest equal
to 22.97 % at 3 p.m. For the ambient RH was higher than
both experimental GHs by 0 - 20 % as a result of the
decreasing sunshine and the increasing of wind speed in
the atmosphere.
10
20
30
40
50
60
70
80
90
100
6:00AM
7:00AM
8:00AM
9:00AM
10:00AM
11:00AM
12:00PM
1:00PM
2:00PM
3:00PM
4:00PM
5:00PM
6:00PM
Relative Humidity
(%)
Time (hr)
modelGH controlGH ambient
Fig. 5. The variation of relative humidity changes for model GH,
control GH and ambient air in a typical day of winter.
B. Summer micro climate
TABLE
II
H
OURLY WEATHER DATA OF SUMMER
,
ATYPICAL DAY
ON
M
AY
4, 2010
Time (h)
Solar
radiation
(W/m
2
)
Ambient
temp.
(
o
C)
Ambient
RH.
(%)
Soil temp.
at 1 m
(
o
C)
6 a.m.
28.05
22.95
97.46
29.10
7 a.m.
79.73
24.25
95.51
29.00
8 a.m.
142.77
26.45
83.37
28.80
9 a.m.
437.28
29.70
68.51
28.80
10 a.m.
626.06
32.00
58.95
29.00
11 a.m.
779.42
35.40
43.34
29.00
12 a.m.
877.53
35.85
44.86
28.90
1
p.m.
892.95
36.25
43.43
28.80
2
p.m.
814.32
38.35
37.59
28.80
3
p.m.
658.25
39.40
31.57
28.90
4
p.m.
247.66
37.30
35.81
28.80
5
p.m.
292.23
39.05
29.60
28.80
6
p.m.
103.45
37.25
32.41
28.90
Table II shows weather data in summer, a typical day
on May 4, 2010. For normally the solar radiation and
surrounding temperature in summer are higher than other
seasons, accordingly the relative humidity might be
lowest. The average maximum solar radiation was in the
range 900 - 1000 W/m
2
. At 1 m depth, soil temperature
was higher than the winter because the ground surface
absorbed more quantities of heat and transferred it into
underground. However, the soil temperature was nearly
constant at 29
o
C.
In Fig. 6, when the air was moving into the earth tube,
the air temperature was decreased by about 0 - 6
o
C as a
discussion in winter climate. Although the outflow
temperature during operation time was higher than the
soil temperature by about 2 - 6
o
C, it was still lower than
the inflow temperature by the range of 0 - 8
o
C. Therefore
from 10 a.m. to 6 p.m, the ETS could keep the
temperature 0 - 4
o
C lower compared to the control GH.
