A Multipurpose Solar Cook Stove

A multipurpose solar cook stove (MSCS) has been developed for drying and cooking of food and vegetable products to meet the requirements of a family. The cost of cook stove was works out in the range of Rs 2,700-2,800. Its pay back period ranges 1.3 to 1.86 years depending upon the fuel it replaced for the user.

Solar drying and cooking is a feasible proposition in most part of India where solar radiation is quite abundant. India receives on an average of 5 kWh/m2/day for about 300 days/year. This energy can be utilized for various thermal applications including drying and cooking. Solar energy appliances are often employed in various uses for single operation and they remain idle when not is use. If the solar appliances are developed to perform more than one function their versatility and reliability can be increased without reducing the quality of product. Keeping this in view, this multipurpose solar cook stove (MSCS) has been designed, developed and tested by Department of Renewable Energy Sources, CTAE, Udaipur. It is capable to cook food and dry the food products and vegetables for meeting the requirements of a family of 5-6 persons.

The MSCS is based on hot-box principle having two reflectors. It consists of a collector unit with a net effective area of 0.36 m2. It also engages the natural circulation of dried air from the dryer. The unit consists of a closed chamber (front glazing), black metallic absorber, insulation drying chamber, trays, reflectors and inlet/outlet openings with lids. Three plenum chambers of size 350 mm x 600 mm x 140 mm, 350 mm x 600 mm x 160 mm and 350 mm x 600 mm x 50 mm are provided below the drying tray for air circulation. The chambers are also painted dull black from outside to receive solar insolation. Three perforated wire mesh trays having 560 mm x 290 mm size were provided for supporting the material to be dried. The inlet-outlet openings are provided with lids for airflow, which could be opened and closed according to need. For drying, good products are kept in the trays and air circulation is maintained by the openings provided at the top and the bottom. Two reflectors of size 350 mm x 600 mm are hinged at either side of the box, provided for increasing the temperature inside chamber. While using the unit as cooker, the openings are closed with the help of lids and the whole device becomes airtight. In this condition, the food products kept in the container, inside the chamber can be easily cooked. Castor wheels are provided for easy movement of the unit. It is installed facing towards south having an inclination of 40o from the horizontal.

The multipurpose cook stove was tested extensively for dryer and cooker by measuring stagnation air temperature in the chamber. The performance of solar cooker was carried out in accordance with IS 13429 : 1992.

Energy conservation and pay back period

By analyzing during of bright sunshine hours it has been estimated that cook stove is capable of drying and cooking for about 280 days in a year at Udaipur.

The energy for cooking and drying 2.3 MJ of fuel equivalent per meal and drying. The multipurpose cook stove is capable of drying and cooking for about 6 persons and it will save 50% of fuel per time.

Accordingly energy saving per year was calculated and its pay back period was estimated without considering interest, maintenance etc.

The performance of multipurpose cook stove was comparable with a commercial fuel for cooking and drying operations. The relatively short pay back period (1.3 to 2.6 years) shows that it is economical.

Acknowledgement

Authors are highly thankful to Ministry of Non-conventional Energy Sources for providing the financial assistance to carry out the research work. They are also thankful to the Department of Renewable Energy sources, College of Technology and Engineering, Udaipur for providing all sorts of required facilities for the study.

Source: Invention Intelligence, May - June 2006