C Palaniappan, general secretary, Planters Energy Network (PEN), School of Energy Sciences, Madurai Kamaraj University, has developed and patented a solar hot air system and it has been found suitable for tea processing and drying spices economically.

PEN already has designed and commissioned around 3200 sqm area of solar air heating systems for tea processing, fruits dehydration and spices drying.

PEN has installed nine solar hot air units to pre heat air for tea processing, covering a total solar collector area of 2,400 sq metre. Two other solar driers covering 150 sqm, were also done for fruits by PEN. Based on the success in tea and fruits processing, PEN has installed two solar drying units -- 290 sqm for chillies and 210 sqm for coriander seeds -- at Eastern Condiments factory at Theni. The use of firewood by the factory has come down by 80 per cent and Rs 3 lakh is saved on this annually since 1996.

One of the major commercial venture for solar hot air system is being set up by the Erode-based Sakthi Masala Ltd. Two solar drying units covering 1032 sqm will be set up for the company. Indian Renewable Energy Development Agency (IREDA) is offering Rs 37 lakh as soft loan at 8.33 per cent interest for the Rs 44-lakh project. CFTRI, Mysore, is planning a pilot solar drying project at the proposed food park. PEN, in fact, is setting a trend for industries to come forward to adopt renewable technologies. It has signed an MoU with National Research Development Corporation (NRDC), for technology licensing and commercial exploitation, including upscaling of inventions, technologies, processes, knowhow and patents relating to the application of solar thermal energy and agro industries.

Palaniapan has transferred the technology of the solar air dryer system to NRDC, which promotes various commercialised enviro-friendly technologies among industries in home and abroad.

In the processing of tea, thermal energy is required for withering and drying. It is done through hot air of 100-140 degree celsius generated in an air heater heat exchange unit by burning fire wood, coal or oil, and fed to dryers. Against the theoretical requirement of 2.7 kwh thermal energy per kg tea, 4-5 kwh energy is consumed.

The large roof area, about 200 sqm, available in plantation sector, can be modified to make integrated solar heaters. The solar heating systems now in use in the plantation sector heats air to a temperature of about 70-80 degree celsius. The ambient air temperature is around 20-30 degree celsius in the hilly plantation areas. The industry needs air at 100-140 degree celsius temperature. The partially hot air is heated further by the conventional furnace. Hence, the present solar system is called `partial energy delivery' (PED) system. According to Palaniappan, "The economic analysis shows a pay back period of less than two years for profit making companies and less than four years for non-profit making companies."

The centre offers several concessions for the project. About 30 per cent of the system's capital cost of Rs 800 per sqm is paid by the government as capital subsidy. Besides, there is 100 per cent depreciation in the cost of the unit in the first year itself. IREDA provides a soft loan for 75 per cent of the system cost at 8.33 per cent.

The Solar Energy Brigade

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UNITS WITH SOLAR HOT AIR SYSTEM---------COLLECTOR AREA

-------------------------------------------- (sq.m)---

Manjolai Tea Estate, Tirunelveli--------------132-----

Kurinji organic Fruits------------------ 100 & 50-----

Golden Hills Tea Estates, Coonoor-------------212-----

UPASI demonstration unit, Nilgris-------------100-----

Havukal Tea Estate, Nilgris-------------------220-----

Kilkothagiri Tea Estate---------------------- 250-----

Brookland Tea Estate, Nilgris-----------------320-----

Parkside Tea Estates, Conoor------------------320-----

Pandiar Tea Estates, Cudalore-----------------516-----

Brookbond Tea Estates, Coonoor----------------290-----

Glendale Tea Estate, Coonoor------------------380-----

Eastern Contiments, Theni---------------290 & 210-----

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Sakthi Masala, Erode, and Duraisami Foods and Spices factory are setting up solar hot air projects in 572 sq m and 460 sqm, respectively.