Design of greenhouse dryers for drying food crops in the rural parts of Karnataka
Student name: Mr Rohit Somanath
Guide: Mr Sapan Thapar
Year of completion: 2015
Host Organisation: Selco Foundation, Bengaluru
Supervisor (Host Organisation): Ms Deepthaa Kumar
Abstract: Solar energy has been used for the preservation of agricultural produce for centuries all
over the world. Recent research on drying reveals the shortcoming of the open sun drying.
In this paper, a detailed study about the crops was made through needs assessment in
selected districts of Karnataka. Crops like areca, red chilli and groundnut have been
shortlisted based on the immediate need for a sustainable solution. .Properties like
moisture content, the drying time, initial and final cost and temperature were considered.
While determining the solution for drying. Many farming communities and individual
farmers practise open sun drying and live on income earned through dried products,
however there are considerable problems and challenges to open sun drying. Unhygienic
drying conditions, slow drying times and loss of crop due to unseasonal rains cause
damage to the crops when they are dried under the sun. A solar dryer would help the
farmers mitigate these losses leading to increase in income.
Considering the above ground level conditions, a prototype was designed which is a
natural draft cum forced draft dryer. It works on Greenhouse effect created by the
polythene sheet which is UV Stabilised. It has a Transmissivity of 87%. The dryer can
accommodate 50 kgs of areca nut if dried on the floor of the dryer. This Greenhouse dryer
has achieved a temperature difference of up to 15º C compared to the ambient temperature.
The customised dome shaped roof will prevent the condensation inside the camber to
collect on the side thus eliminating the problem of remoisuturization of the food crop.
This prototype dryer was able to dry 500 grams of turmeric within 3 days in comparison to
7 days required under Open Sun Drying. The turmeric was reduced to nearly 10 % of its
initial weight. The drying time can further be reduced by employing supplementary
heating systems like flat plate air collector (FPC) , solar thermal water heat storage, PCM’s
(Phase change materials).
Keywords: Greenhouse dryers, FPC, PCM, Transmissivity, Polythene sheet, UV
stabilised, Farming, Areca, Turmeric, Crops.
