Solar Assisted Air Heating Process‐Implementing Solar Collectors in Sri Lankan Tea Industry
Sri Lanka is one of the greatest producers and exporters of quality tea in the world. The tea industry plays a key role in the economy and there is a great interest of continuously improving it in order to stay competitive. The process of drying tea requires thermal energy which currently is supplied through combustion of fuel woods on which the industry is highly dependent. With the rising prices on fuel woods over the past recent years it has become increasingly urgent to find substitutes, or complements to this source of energy. One potential solution would be to utilize solar thermal energy by implementing solar collectors in the tea manufacturing process. Sri Lanka is located close to the equator and has ideal conditions for harnessing solar energy, why solar applications would be highly suitable in this context. This report aims to study an existing simple system of flat plate solar collectors at the University of Peradeniya, Sri Lanka. The solar collectors are built using local inexpensive material. The objectives are to calculate the collector efficiency and perform a cost analysis in order to determine the potential economic benefits of utilizing solar thermal power as opposed to fuel woods. Finally the report will present suggestions on improvements for the existing collector design, taking the practical and economic feasibility into consideration. The collector efficiency of the existing design was calculated to be approximately 35 % and the energy produced by the flat plate solar collectors was found to be less expensive than combustion of fuel woods, despite the many imperfections of the collector design. Suggestions on refinements include improving the selectivity of the absorber surface with a black chrome coating, equipping the collector with a sun-tracking system, adding obstacles in the collector air duct, using a v-corrugated absorber plate, shifting to downward air blowing, changing heat transfer fluid and using multiple sheets of glass as glazing. Through these relatively simple and cost-effective improvements on the system the collector efficiency could increase substantially, thereby reducing energy costs. Moreover the implementation of solar collectors in the Sri Lankan tea manufacturing process would be beneficial from an environmental perspective.
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