Food industry is an important sector in every economy, and India is no exception. The food industry in India plays an important role in the country’s economic development as a result of the vital linkages and synergies that it promotes between the industrial and the agricultural sector, the two most important sectors in the Indian economy. Presently, the world’s second largest producer of food products second only to China, India has the potential of being the largest producer, thereof surpassing China, given that India’s food and agricultural sector contributes are around 26% of the country’s annual GDP. The Indian food industry has shown signs of potential for higher growth and profitability in the coming years. There will be a phenomenal deployment of capital, human resources, modern technology, and finance of over INR 140 billion in this industry in the next decade. This industry can be identified as a prospective area for the application of Solar Thermal Energy Systems because the relatively lower temperature at which the processes are carried out here can be achieved easily through solar heating. The food industry and beverages sector has a large heat demand in the temperature range up to 150°C. Common processes are pasteurization of liquid goods at 65 to 100 °C, cooking at 100 °C in meat processing, blanching of vegetables or meat at 65 to 95 °C, drying and evaporation at 40 to 130 °C in fruit and vegetable processing or cleaning of products and production facilities at 60 to 90 °C. Taking into account its big share of the 11 industrial heat demand at low temperatures, the food industry has a great potential for the use of Solar Thermal Energy.
Application of solar energy in food processing industry was mainly limited to drying operations. Solar vegetable-fruit dryers, operating below 55 degree centigrade, are used for the purpose. But in recent years, many solar technologies have been developed for variety of applications. Different solar concentrators can provide excellent boiling, steaming, blanching and roasting capabilities while Solar Air Dryers/ Heaters can effectively remove moisture. Efforts are required to integrate knowledge of food processing with capabilities of available solar thermal gadgets Increasing population and high cost of fuels have created opportunities for using alternate renewable energies for postharvest processing of foods. There is a vast potential for use of solar energy devices / systems in industries for process heat and other thermal applications. Energy for these applications were being met mainly through fuel oil which is not only import dependent but is also creating huge GHG emissions in atmosphere resulting threat to our planet. India is consuming over 100 million tonnes of oil every year for various uses. Out of this, almost 40% is being consumed in the industrial sector alone. Further, 40-50% of this consumption is in thermal form alone with temperature range below 250°C which comes to around 15 million tonnes of fuel oil per annum. The applications include drying and canning in food industry, and various such applications in many more industries. The working fluid required for these applications is either pressurized hot water, steam or hot air in temperature range of 60-250°C.
Considered from the point of view of cleanliness and production, which are vital requirements in the food processing industry, the application of solar energy could be a big advantage for this industry. Solar energy is available abundantly in the country and can be used to good benefit in food production. There are number of solar energy technologies which can be used for such applications and reduce consumption of fuel oil mainly during day time. The technologies include solar water heating systems, steam generating systems and air heating systems based on flat plate or evacuated tube collectors and automatically tracked solar concentrating collectors.
Solar Food Processing Technologies
Solar food processing brings in two emerging technologies together to solve the two major problems the world facing in 21st century, namely: how to generate energy enough for an expanding global population; and how to feed the constantly expanding world population? This has a different connotation with respect to developing countries. Growing population and unequal wealth distribution in these countries has created a section of the society being left behind and chronically poor. Lack of reliable and affordable energy sources in these parts only complicates the matter. This situation also demands search for faster, cheaper and safer methods by which food can be conserved and distributed to the rural populations. In the face of such great demand for food to feed people, it is sad to note that 30–40 % of food goes waste in India every year for lack of a systematic post-harvest processing and preservation. The food processing industry in India accounts for only 2.2 % of the total.
Solar food processing is an emerging technology that provides good quality foods at low or no additional fuel costs. A number of solar dryers, collectors and concentrators are currently being used for various steps in food processing and value addition. With the help of concentrators, higher temperatures can be achieved and solar heating systems with concentrators can be effectively used in this particular industry. This basic principle is very simple but the development of such systems in India for this particular area of application has so far been overlooked by the solar energy technologists.
Society for Energy, Environment and Development (SEED)
developed Solar Cabinet Dryer with forced circulation which has been used for dehydration and development of value added products from locally grown fruits, vegetables, leafy greens and forest produce. Drying under simulated shade conditions using UVreducing blue filter helps retain nutrients better. It’s simple design and ease of handling makes SEED Solar Dryer an ideal choice for application of food processing in rural settings, closer to where the harvest is produced, eliminating the need for expensive transportation or storage of fresh produce. It also creates employment opportunities among the rural population, especially women. Other gadgets based on solar collectors and concentrators currently being used at various steps of food processing are reviewed.
Food Processing Technology is one of the priority sectors in our country. SEED integrated this technology with Solar Dryer and introduced the same at micro level in the villages to help the society. This approach finds a solution for preservation with long shelf life and for rural employment. It is noteworthy that technology will process the food products with zero energy cost. SEED has so far successfully developed about 70 products using fruits, vegetables, Non-Timber forest produces, spices, herbs using solar dryers on a commercial scale. In an effort to resolve the problem of wastage & preservation of agrihorticultural produces, SEED also designed and developed the much awarded Solar Cabinet Air Dryer. The credit to this innovative technology goes to Prof M. Ramakrishna Rao, Founder Secretary, SEED & formerly Prof of instrumentation, IISc., Bangalore. Under his guidance SEED R&D team developed different models of Cabinet Solar Air Dryers with different drying capacities like SMD 8, SDM 25, SDM 50, SDM 100 and SDM 200. SDM 500 for higher drying capacity is in R&D. Some of the food products processed using cabinet solar dryers are fruits, vegetables spices, forest produce, medicinal & herbal products, chemical powders and more like Vermicelli, Noodles, Pickled Chilies and Fish.
Solar air heating systems based on flat plate collectors have been found to be useful in food processing industries for drying of various food products. These industries generally require hot air at low temperature (50-800°C) as process heat for drying of products such as tea leaves/ coffee beans, and also for processing of fruits, spices, cereals, mushroom, papad, vegetables, fish, seafood etc. It is estimated that over 800 million Kg of tea leaves are being produced and dried in Southern states, Himachal Pradesh, West Bengal, Assam and North East States. Another 250 million Kg of coffee beans are also being produced and dried every year. Millions of tonnes of food and industrial products are also being dried annually in various industries in the country. The systems installed in industries for drying of various products have been saving a significant amount of fossil fuel, apart from improving the quality of end product and reducing GHG emissions.
A 500 Kg capacity solar fish drying unit is functioning at Vishakhapatnam, Andhra Pradesh since 1999. The system generates hot air from 60 sq. m. of roof integrated solar collectors which is sent to the recirculation drier being run on electricity. It has resulted in huge saving of electricity besides obtaining good quality of dry fi sh. Many more such systems for other applications are functioning in the country. The other technology which is very promising and is being widely accepted by the industry is Solar Concentrated Technology. Solar thermal energy is an extremely convenient source of heating; and a technology that does not rely on scarce, finite energy resources. Concentrated Solar Technology is a solar thermal concentrating technology that converts solar energy to heat energy. CST is a costeffective way to produce heat energy while reducing our dependence on foreign oil, improving domestic energy-price stability, reducing carbon emissions, cleaning our air, promoting economic growth, and creating jobs. CST at present is the need of the hour. It can provide steam up to a temperature of say 300°C which is the direct need of food industries. Solar Concentrator Technology has good potential for various applications, including power generation and process heating applications. Systems based on these technologies are being locally manufactured and are being promoted by 8-10 manufacturers. One of the technologies is based on fixed receiver East-West automatically tracked parabolic concentrators and the other is on fully tracked heat receiver and dish reflectors. While the first one is more user friendly and can provide low temperature steam at a temperature of say 120 to 200°C, the other one is little complex and could provide steam at higher temperature ranging to 300°C. Systems based on fixed receiver technology have been under installation for last many years. Fully tracked technology is under pilot scale demonstration and only 10 dishes, each of 160 sq. m. area have been in use till date. Both these technologies are mainly being used for community cooking and process heat applications in food industry.
The ARUN Solar Concentrator from Clique Solar, headquartered in Mumbai, harnesses solar power to heat water and air to high temperatures for industrial purposes. The ARUN solar dish occupies just 9 sq m and has an efficiency-rate of 60-65%, which is better than most rival technologies. The Solar Concentrator Systems can be used in ‘ADD ON’ mode and can be retrofitted to the existing boiler or heater system in the industry. In this mode it delivers thermal energy whenever beam radiation is available and saves fuel used. It needs cleaning of reflectors and no fuel at all. The thermal energy generated can be stored to supply energy requirements during evening and night. The unit is best suited for the industrial applications using thermal energy from electricity or liquid fossil fuels. The thermal medium can be high or low pressure process steam, water, air, thermic fluid or oil. It can be used for providing process heat for a wide range of applications using boilers or heaters. The Solar Concentrator Systems can find its usage in agro and food processing industries, food and fruits products, vegetable oil mills, Cold Storage Units for perishable food as well as units using vapor absorption refrigeration for space cooling.
There are no doubts that solar energy will make an essential contribution to a future, sustainable energy supply. The main use of solar radiation will be to produce thermal energy in a wide range of temperatures that will surely benefit the food industry in long run. Solar food processing is an innovative and multi-faceted technique capable of addressing various problems faced by people in the developing world. The implementation of technologies for food processing and conservation using solar energy can indirectly help to improve health conditions, create sustainable local economic opportunities, enhance productivity, and limit environmental damage by promoting the use of clean and renewable energy sources.