Solar energy is conquering more territories with increasing industrial application. In Theni district, it has become popular among dhal mills. Besides conserving considerable fossil fuel, solar heating used in the processing of dhal also helps to keep the environment around the Western Ghats clean.
Solar heat processor developed by Planters’ Energy Network (PEN) is now used in big dhal processing units in Theni. The process starts with harvesting of solar energy through huge roof-top panels. The energy is conveyed to the point of usage using a blower.
J. Murugesan of AMRR Dhal Mill explains that solar heating has considerably brought down diesel consumption and also saved on area used in conventional open drying. In the past, the mill used 18 litres of diesel to process 50 bags of urad dhal of 100 kg each.
Now only solar energy is used to process 300 bags of urad dhal a day.
The traditional process involved drying dhal under sunlight in the open before sending it for removal of pods. Now drying and removal of pods happen simultaneously.
C. Palaniappan, founder-member of PEN, says India, as a major pulses producing country, has over 1,400 pulses processing units that provide employment for rural and semi-urban population.
After shifting from conventional drying, the processing units use diesel to generate heat at 60 to 65 degree C. Application of solar drying will bring down fuel consumption (firewood or diesel) by 60 to 80 per cent, he says.
Theni dhal mills use their roofs to harvest solar energy. The system does not require much maintenance. It is enough if two people are engaged to clean the solar panels once a week, Dr. Palaniappan says. The switchover from solar heating to conventional heating on rainy days is also easy.
At Sanga Dhal Mill, its roof, measuring 167 square metres, serves as the solar energy harvester. The hot air conveyed to the point of usage by an insulated metal duct is blown into the dryer. The system, installed in 2002, saves 60 to 90 litres of diesel a day, he says. Inspired by its performance, other dhal mills in the town have taken the solar path.
According to Dr. Palaniappan, a subsidy of Rs 2,400 per square metre is available for installation of solar heaters using flat plate air collectors.
An accelerated depreciation of 80 per cent is also allowed on total investment.
