In India, cooking accounts for 36% of primary energy consumption. In most developing countries, wood, charcoal and dung cakes are predominantly used for cooking in rural areas, whereas LPG (Liquefied Petroleum Gas) and electricity are prevalent in urban areas. For a country blessed with generous sunshine, India can effectively utilize solar cookers to meet its domestic cooking energy requirement. Solar cookers are inexpensive and environment-friendly, but they have several limitations.
For instance, conventional box type solar coolers are difficult to use for cooking. They can only be used outdoors, in rural areas, and on roof tops, in urban areas. They can only be used during periods of clear skies and the rate of cooking cannot be controlled. Such barriers limit the scope of interactive cooking, which is widespread in Indian kitchens, where several members of the household cook together in the kitchen.
To counter these restrictions, Dr. Prasanna U R and Dr. L Umanand from the Centre for Electronic Design and Technology at the Indian Institute of Science, Bangalore have developed a hybrid solar cooking device. According to Dr. Prasanna, “the basic objective of this device is to bring the solar energy to the kitchen directly.” The hybrid device essentially transfers solar energy to the kitchen as a supplement to the conventional LPG source.
A solar thermal collector placed on the roof top transfers solar energy to a curved concentrating collector which absorbs the solar energy to increase the temperature of heat transfer fluid which is being circulated through the collector. Heat transfer fluid is special kind of fluid whose temperature can go up to 300°C, It is stored in a thermally insulated tank. A heat exchanger is positioned in the kitchen which transfers the heat from the fluid to the food that is meant to be cooked. A pump is used to regulate the heat transfer from the collector to the heat storage tank.
“This cooker can be used indoors within the kitchen, reduces usage of conventional energy and can be used at any time of the day or night,” explains Dr. Prasanna.
To store the energy extracted from the sun, an insulated tank will be used, whose size depends on the amount of energy that needs to be stored. This energy can be later on used to cook late at nights or early in the morning when the sun isn’t out yet. Using solar energy in concurrence with LPG reduces the time required for cooking, compared to the previous box type solar cookers. This device allows heat to transfer from the solar collector to the food meant to be cooked at an optimal rate.
Despite the apparent advantages of the hybrid solar cooker, “the market is not ready for this type of technology. There are still some challenges in the technology like the development of heat exchangers and concentrating collectors,” explains Dr. Prasanna. “People still need to design this device better so that everything can be installed at homes cost effectively and quickly.”
About the researchers:
Dr. Prasanna U R was a PhD scholar at the Department of Electronic Systems Engineering at the Indian Institute of Science, Bangalore during the publication of this research (July, 2010).
Dr. Umanand L was his thesis advisor during this research.
Email: email@example.com (Prasanna U R)