International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 2, Issue 12, December 2012) 539 Study on Design of an Evacuated Tube Solar Collector for High Temperature Steam Generation Dr.S.P.Vendan 1 , L.P.A.Shunmuganathan 2 , T.Manojkumar 2 , C.Shiva Thanu 2 1 Associate Professor, Department of Mechanical Engineering, PSG CT. 2 Student, Department of Mechanical Engineering, PSG CT. Abstract—The eco-friendly and non-polluting solar energy can be used for direct conversion into electricity by photo- voltaic conversion and into thermal energy by using Flat Plate Collectors (FPC) or Evacuated Tube Collectors (ETC). Evacuated Tube Collectors are more efficient compared to Flat Plate Collectors as the former eliminates the convective heat losses. This paper discusses design calculations involved in the development of an Energy Efficient Solar Thermal System for generating steam at atmospheric pressure. This finds applications such as Steam cooking, laundry etc. It includes calculation of collector area and number of evacuated tubes required. It also reports comparison of its performance with the conventionally used steam boilers in terms of fuel usage and carbon emissions. Keywords— Evacuated Tube Collectors, Flat plate collectors, Steam Generation, Low pressure steam applications, Design of ETC. I. INTRODUCTION In present scenario, the energy crisis is predominant as conventional sources of power such as fossil fuels are depleting at a faster rate. Also, the usage of these fuels, adversely affect our environment resulting in Global warming, Ozone layer depletion, Acid rain etc. Hence, there is a necessity to shift the focus towards other non- conventional and renewable energy sources. Solar energy finds its application over diverse fields. This paper focuses on how solar energy can be used in ironing process of laundry. The steam generated at 175 o C serves this purpose. Steam, generated using boilers or electrical systems can be replaced by cost-effective solar thermal collector. The selection of appropriate solar collector, design calculation to estimate the approximate collector area and experimental setup required to determine the collector performance are discussed in this paper. II. COMPARISION BETWEEN FPC AND ETC An evacuated tube collector is slightly more efficient than a flat plate system due to lower heat losses. With less heat loss through the vacuum air layer in the evacuated tubes, these systems are more efficient at lower ambient air temperatures. Compared to flat plate collectors, evacuated tube collectors are less expensive. Require a smaller roof area than comparable flat plate collectors. Maintaining vacuum is difficult in case of evacuated tube collector. For low temperature applications, flat plate collectors are more efficient compared to evacuated tube collectors. But, for the purpose of high temperature applications like steam generation, evacuated tube collectors are best suited because of its minimum heat loss as shown in Figure. 1. Figure 1 Comparison between FPC and ETC III. EVACUATED TUBE COLLECTOR ETC’s are built to reduce convective and heat conduction loss (vacuum is a heat insulator). Each evacuated tube consists of two glass tubes. The outer tube is made of extremely strong transparent glass that is able to withstand changing climatic conditions. The inner tube is also made of glass, but coated with a special selective coating (ALN/AIN-SS/CU) which features excellent solar heat absorption and minimal heat reflection properties. The air is evacuated from the space between the two glass tubes to form a vacuum.