Energy options for rice drying
What is energy in rice drying used for?
A mechanical dryer for rice needs energy for two purposes:
Why is the energy source important?
Energy cost constitutes the largest cost item in mechanical drying and therefore choosing the most appropriate energy source has the highest potential to reduce drying cost. Some forms of energy are also more environmentally friendly than others.
How much energy is needed?
The desired drying rate for optimum dryer use and grain quality is 1% moisture content per hour. To achieve this, around 1m3 of air with a temperature of 43°C needs to be moved through each ton of grain. For each ton dryer capacity this requires 0.7−1 kW motor power for the blower and around 50 kJ/h energy for heating the air.
Energy options for moving the air
An electric motor is the ideal power source for fan.
B. Diesel or gasoline
When electricity is not available, a stationary, combustion engine can be used.
C. Free convection
A long chimney in which hot air moves upward can generate sufficient draft to move air through thin layers of grain.
For a mechanical dryer: Electric motor and rice husk furnace or diesel engine and rice husk furnace.
For the farm level: The Solar Bubble Dryer.
Energy options for heating the drying air
Kerosene is commonly used for rice drying.
Consumption: 1.8−2 Liters/h and per ton of paddy.
2. Rice hull
Rice hull is a by-product in the milling process and is often considered waste.
3. Solar energy using solar collectors
Solar energy is freely available during the day and is environmentally friendly. Assuming an average solar radiation of 500 W/m3 and 70% collector efficiency, one square meter of solar panel can generate 1,260 kJ/h or roughly 15,000 kJ/d.
A promising new technology: The Solar Bubble Dryer
Solar-powered fans inflate the Solar Bubble Dryer and move air over the rice inside the tunnel to remove the evaporated water. Sunrays entering through the transparent top heat up the drying air.
Developed by M Gummert