Abstract
Introduction
Solar ox-shed structure
Experiment and measurement
Analysis of the cost and benefit of the solar ox-fattening shed
Huang Guiqin
Li Yunfei Wang Yujang
Jilin Agricultural University
Changchun. Jilin Province. 130118, China
Paper No.9410
|
In this paper, the authors will introduce the structure and the performance of a solar ox-fattening shed. The' results obtained from experiments showed that increasing the temperature of the solar ox-fattening shed had increased significantly the weight of the oxen and increased economic output. KEYWORDS: fattening ox, solar ox-shed, solar collector |
Jilin is in the Northeast of China. Temperatures in the long winter are quite low. In January, the temperature can drop to minus 30 degrees centigrade. The forage which the oxen eat is just used to maintain body temperature. Therefore, the oxen in the winter grow very slowly and the economic output is quite low owing to the long raising period. The temperature in the traditional ox-shed is about minus ten degrees centigrade which does not meet the needs of the growing conditions of the oxen. Taking into account Jilin's local resources, we designed the solar ox-fattening shed which brought high economic and social benefits.
Based on the popular ox-shed, we set up a moveable solar collector in front of the shed. Through 90 days fattening experiment on the oxen, we found that in January the average temperature of the shed was about 5°C and the lowest during the night was just above 1°C, which almost met the requirements of the growing conditions needed for the oxen.
The designing principles of the solar ox-shed were simple structure and low cost which the farmers could afford. The capacity of each shed was 8 to 10 oxen that was suitable to the raising farmer family. The oxen in the shed were divided by a wall. The area of the shed was 50 m² and the raising density was 0.16 to 0.2 ox per square meter. The ox dung was removed from the dung trough at the end of ox-bed.
1. Round wall and its materials
To keep the heat, the thickness of the wall was more than 24 cm. Brick was used as wall material, even though its heat insulating property is not better than that of adobe. However it lasts longer than adobe.
2. Roof
The roof was covered with wood board, crop stem and tiles. The thickness is not less than 90 mm. To collect solar energy, the south side of the roof was covered with double layer plastic film in which there was static air. The angle of the slope was 30 degrees, and the wood frame of 650* 650 mm kept the film smooth and fixed. In the warm season, the film can be detached and the shed becomes a half-open ox-shed that is good for ventilation.
3. Solar collector
The solar collector was constructed with double layer film and the blackened south wall of the shed on which three air inlets and outlets were opened. The film let the sunlight in and prevented the heat from going out. The blackened wall absorbed the heat. The temperature grade between the collector and the shed made air flow through the inlets and the outlets. As a result of heat convection, the shed was heated by solar energy. During the night, the wall would release the heat stored during the day to the cold air in the shed and kept the temperature of the shed above zero.
Fig 1. Simple solar ox-shed structure
1. Natural conditions of the experimental village
Sheng Li is a village in Li Shu county which is located in 43°21' North latitude, 124°18' East longitude and is 1587 m above sea level. The local meteorological data for the 90 day experimental period are shown in Table 1.
Table 1. Meteorological data of Li Shu county from December 1991 to March 1992
|
Temperature (°C) |
December |
January |
February |
March |
|
highest |
-16 |
-0.6 |
+ 16.3 |
+ 9.2 |
|
lowest |
-28.8 |
-34.4 |
-22.4 |
-15.5 |
By calculation, from the beginning of December to the middle of March, the solar altitude is 27° to 44° and the minimum solar altitude is 23 °.
2. Experimental conditions
2.1 Ox-shed
We selected three ox-sheds to do the experiment, No.1, No.2, and No.3. No.1 was the solar ox-shed. Its south wall was covered with the plastic film of the solar collector at 67 ° against the horizontal earth. No.2, to the west of No.1, was covered with the plastic film of the solar collector vertically. No.3, to the west of No.2 was a half-open shed.
Table 2 Average temperature inside and outside the shed during the raising period (°C)
|
Time |
Days |
Shed No.1 |
Shed No.2 |
Shed No.3 |
Outside |
|
91.12 |
6 |
3.06±2.05 |
1.04±3.01 |
-11.71±4.91 |
-17.55t4.31 |
|
92.1 |
31 |
4.39±1.65 |
1.43±2.15 |
-7.39±4.17 |
-11.22t4.14 |
|
92.2 |
29 |
4.66±3.09 |
2.72±2.41 |
-4.48±5.99 |
-7.9±8.35 |
|
93.3 |
24 |
8.34±3.13 |
6.3812.01 |
0.986±5.09 |
-2.14±7.21 |
The incidence of sunlight to No.1 shed on the first of December is 4°; in the middle of March it is 21° and on the winter solstice it is zero. Whereas the incidence of sunlight to No. 2 shed is 27°, 44° and 23° respectively. Therefore, the performance of No.1 shed was better than that of No. 2 shed as shown by the experiment. The optimal inclination (a) was a =90°-hmin
2.2 Other conditions
Eighteen oxen, of almost the same age and weight were raised in three sheds with the same forage and conditions. The results, after 90 days raising, are given in Tables 2, 3 and 4.
Table 3 Average relative humidity of the inside and outside of the shed during raising period (%)
|
Time |
Shed No.1 |
Shed No.2 |
Shed No.3 |
Outside |
|
91.12 |
49.99±15.84 |
70.62±14.21 |
42.44±18.54 |
33.75±22.02 |
|
92.1 |
75.59±11.00 |
67.98±17.02 |
44.24±8.24 |
29.41±15.70 |
|
92.2 |
70.14±13.28 |
64.20±15.04 |
41.00±11.02 |
34.91±11.74 |
|
92.3 |
64.08±11.97 |
44.83±17.11 |
43.20±11.70 |
36.10±11.94 |
Table 4. Weight gain results during the raising period (kg)
|
Shed |
Head |
Initial weight |
Last weight |
Gain Average daily gain | |
|
No.1 |
6 |
381.67+65.24 |
500.83±74.32 |
119.16±8.80 |
1.324 |
|
No. 3 |
6 |
387.50±78.02 |
460.00±88.99 |
72.50±31.41 |
0.806 |
3. Results and discussion
From Table 2, we can see that the temperature of Sheds No.1 and No. 2 were about 10 °C above those of Shed No. 3, that the temperature of Shed No.1 was about 2°C above that of Shed No.2. Shed No.1 gave the best performance.
The relative humidity in Sheds No.1 and No. 2 was relatively high, but it still did not meet the requirement for the growing conditions, which is about 75 - 80%. If the humidity was too high, the roof windows could be opened for 1 to 2 hours at noon.
1. The cost of the shed
The shed cost 56 yuan/m² which is equal to 467 yuan/head (based on 6 oxen). If at the maximum capacity of 8 oxen, then the cost was 350 yuan/head. The plastic film collector can be used for 2--3 years. If the film is replaced, the cost will increase 1.0--1.2 yuan/m², which is about 8--10 yuan per head. If the shed lasts for 10 years, and the film is replaced four times during this period, then for raising six oxen, the shed will cost 50.7 yuan / (head* year) and 39 yuan/ (head* year) if eight oxen are raised. The above considerations are only limited to the winter period. If fattening oxen can be marketed during two or three cycles in one year, the cost of the shed will be significantly reduced.
2. Input and output analysis
Table 4 showed that the ox gained 46.6 kg/head in Shed No.1 more than that in Shed No.3. If the ox is at 4.00 yuan/kg, the gain benefit will be 186.48 yuan/head. In the shed structure, the cost of No.1 was 50 yuan/head more than that in No.3. It can be concluded that the economic benefit in Shed No.1 was significant.
Reference
1. Northeast Agricultural College, Poultry and Environmental Hygiene. Agricultural Publisher, 1990.10
2. China Solar Energy Society, Fundamental Theory of Solar Head Utilization.
3. Tian Jin University, Solar Heating.1983.6
4. China Agricultural Engineering Research Institute, Directory of Agricultural Engineering, Agricultural Publisher.
