India: Solar Thermal Air Drying successfully implemented at Bicycle Factory

 solar air drying in India Glazed air collectors made in India: Planters Energy Network installed almost 300 m2 on the roof of the paint shop belonging to the bicycle factory of TI Cycles of India. It is therewith one of the largest solar air heating systems nationwide. Photo: TI Cycles

Tube Investments (TI) Cycles of India has been very satisfied with the performance of the solar air heating system installed by Planters Energy Network (PEN) in March 2009 at the factory in Chennai, in the state of Tamil Nadu. According to Chidambaram Palaniappan, Chief Executive and General Secretary of PEN, the cost of kerosene had been rising with time, prompting officials at TI Cycles to look into adopting alternative technology that would not only save fuel, but also provide a clean energy source. The strategy paid off for them: In reference to the first year's operational results, the estimated Indian Rupees (INR) 2 million investment will be repaid in less than two years, supported by a national capital subsidy of 1,750 INR/m2 of collector area. Moreover, the company profited from a 80 % accelerated depreciation on investment costs in this first year.

The system generates around 7,500 kg of hot air per hour, raising temperatures 30 to 55 °C above ambient. “IT Cycles saved 12,320 litres of kerosene in the first year,” states Palaniappan. Kerosene typically costs around 43 INR per litre.

And how does the system work in technical terms? The hot air generated by the field of glazed air collectors is used in the factory's paint shop for pre-heating the hot air of dryers and ovens, the machines that will then dry and cure painted bicycle parts. The air temperature for the curing process ranges from 80 to 150 °C. “If pre-heated air at 60 to 95 °C - depending upon the strength of the solar radiation - is provided to the dryer instead of cold air, fuel consumption can be reduced”, PEN explains on their homepage. A low volt blower with a power of 1.5 kW draws in the solar-heated air.

The solar thermal system works in combination with a heating system driven by fossil fuels since the aforementioned ovens operate 24 hours a day, all year round. The solar air collectors manufactured by PEN, based in Tamil Nadu, are 2 m2 in size and consist of a black-painted aluminium absorber and a hardened glass cover. Since its foundation in 1989, PEN has installed 10,000 m2 of solar collector area for drying such different things as tea leaves, spices, leather, ceramics, fish, cloth and salt or dehydrating fruits and vegetables.

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This text was written by Jaideep Malaviya, an expert in Solar Thermal based in India (


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