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Development of Solar Dryer for Drying of Spices Seeds

MUHAMMAD ZAKARIA HOSSAIN
FMPE, BARI

MD AYUB HOSSAIN
FMPE, BARI

MD MASUD ALAM
FMPE, BARI

Abstract/ Executive Summary:

A solar dryer was designed, fabricated and installed at Spices Research Centre, Shibganj, Bogra for drying of spices seeds. As a spices chilli was dried following three different techniques named drying with solar collector, drying without solar collector and drying of partial shading of the collector. The open sun drying of chilli was done simultaneously to study performance among them. The germination percentage at dryer with collector was found 55% in the dryer whereas 76% at open sun with drying time of 3 and 8 days respectively. Again in case of chamber drying without collector the germination was found 75% in the dryer with drying time of 8 days and 73% in open sun with drying time of 9 days. The germination percentages of dryer with partial shade of solar collector and open sun was found 71% and 74% with 6 and 8 days of drying time. Though solar drying was quick way of drying of chilli than that of sun drying but the germination percentages of sun drying was found well than that of solar drying at every case.

Keywords: Solar dryer, Spices seed, Chilli

Location: Spices Research Centre, Shibganj, Bogra

Start Date: 00-00-2014

End Date: 00-00-2015

Program Area: Farm Mechanization

Commodity: Drier

Objectives:

(a) to design and fabrication of a solar dryer suitable for drying of spices seeds

(b) to test the performance of the dryer for drying of spices seeds

(c) to evaluate the seed quality in terms of germination

Methodology:

A solar dryer was designed based on the procedure described by Akoy et al. (2006), Ampratwum (1998), Basunia and Abe (2001). The solar dryer was consisted of dryer and collector. The dryer was composed of drying chamber, drying tray, and outlet. The collector was made for maximum utilization of solar energy. The black body material was used for increasing the efficiency of collector. Kalogirou (2009) stated that the best slope (tilt angle) for the flat plat collector was equals to the latitude of the physical location. Similar statement was made by Sulaiman et al. (2005) in their solar electricity generation works. In Bangladesh average tilt angle of solar collector should be 23.5⁰C for maximum exposure of solar radiation (Bala, 1998). To design the solar dryer the following assumptions were made. The design of solar dryer was done by Auto CAD software. The overall design was done in three dimensional modes (3D). The data was taken from 8:00 am to 5:00 pm at one hour interval. The data of solar radiation was taken by a solar meter (UVA 18573, USA). The velocity of air was measured by an anemometer (TA 430, England). The ambient and exhaust temperature was recorded by a digital thermometer (K202, Germany). The upper tray and lower tray temperature was also recorded by the thermometer. The hygrometer (GM 1360, China) was used to record the relative humidity of inside and outside of the dryer and upper or lower tray of the dryer. Three samples were taken at the upper tray and another three samples were taken at the lower tray. These samples were weighed at one hour interval by an electric balance outside of the dryer in order to get moisture data of seeds. The balance was surrounded by glass so that flowing air can not affect the weighted value. The data was recorded to know their drying kinetics. In this case of solar drying both dryer chamber and solar collector was attached as a whole body to dry the samples. The chilli in addition to other spices crops such as fenugreek, fennel, and onion were used for seed drying. The fresh weight of the samples was recorded by an electric balance. The samples were then taken to the drying chamber. After completion drying the final weight of the samples were also recorded. The drying of fenugreek needed 2 days whereas 3 days needed for drying fennel and onion at April 2014. The drying of red chilli needed 5 days at June 2014. The open sun drying was also done at this particular time for each of the crops. The shading was done retarding the excessive sunshine heat in the dryer. It was mainly applied to the collector. A tarpaulin was used as shading materials. Whenever sunshine intensity exceeds the safe drying temperature the tarpaulin was placed to reduce the excessive heat. The drying of chilli started at February, 2015 and needed 6 days to dry in the dryer. At the same time the open sun drying was conducted and there needed 8 days to dry in the open sun. The collector was the mobile part of the dryer. It was attached to the dryer with nut and bolt and can be easily parted. In this case of drying the solar collector was separated from the dryer. Hence the only energy source was sunshine ray trapping by transparent polythene cover. The drying of chilli started at April, 2015 and needed 7 days to dry in the dryer. At the same time the open sun drying was conducted and there needed 8 days to dry in the open sun. The seeds were soaked by normal water for one hour to initiate seed germination. Ten number of petridish were taken and each filled with 100 number of seeds. They were fixed by tissue paper and filled with water up to saturation. The germinating temperature was maintained 20-30⁰C and first counting of germination was after 7 days and final counting of germination was counted after 14 days. (Aswathiah et al.)

Source of Information: Annual Research Report, FMPE, BARI--2014-15

Article Link (Online Journal):

Funding Source:

1.

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The data were taken from 8:00 am to 5:00 pm of one hour interval. The average ambient temperature, ambient relative humidity, upper tray temperature, lower tray temperature, temperature at collector outlet, exhaust temperature, exhaust relative humidity, solar radiation, and air velocity, was found 36.22°C, 35.62%, 43.89°C, 39.04°C, 51.84°C, 36.07°C, 37.22% , 3.4 mW/cm² and 1 m/s respectively for drying of chilli. In about to every case the average dryer temperature was significantly (P <0.01) higher than that of ambient temperature. The two trays showed insignificant (P >0.01) temperature difference which was desirable. The collector showed significant (P <0.01) temperature differences than outside temperature which was desirable and enhance drying progress. Temperature had linear relation with solar radiation. In fifth hour of drying, the solar intensity was low and the ambient, upper, lower and exhaust temperature was also low. The temperatures increased whenever the solar intensity increased. The relative humidity had inverse relation with solar radiation. The cloudy weather existed at the fifth hour of drying. In this time the solar radiation was low and the ambient and exhaust relative humidity was high. Air flow rate was very low at that particular time. Again whenever sunny weather was existed the air velocity increased and relative humidity’s was also decreased. Chilli drying at solar dryer with solar collector was the quicker way of drying but harmful to seed germination. The germination percentage was found only 55% in the dryer whereas 76% was found at open sun with drying time of 3 and 8 days respectively. Again in case of chamber drying without collector the germination was found 75% in the dryer with drying time of 8 days and 73% in open sun with drying time of 9 days. In this case the drying time between dryer and open sun was not significant but there found similar germination rate. The last option on drying technique was shading the collector partially when there is excessive heat. The germination percentages of dryer with partial shade of solar collector and open sun was found 71% and 74% with 6 and 8 days of drying time. In this case germination percentage was good and there found reduction of drying time than that of open sun drying.

Knowledge Management: Report/Proceedings