ISSN: 2277-3754 ISO 9001:2008 Certified International Journal of Engineering and Innovative Technology (IJEIT) Volume 4, Issue 3, September 2014 1 Abstract -The performance evaluation of a thermo-syphon water heating system using a compound parabolic solar collector is presented. The system investigated consists of a compound parabolic collector, an absorber/receiver, a hot water storage tank, a cold water storage tank, water returning pipe and the support stand. Cold water is stored in an upper bigger cold water tank and this water flows by gravity through a pipe passing through the focus of a compound parabolic collector into a lagged lower tank where it is stored for use. Series of performance tests were carried out on the system under high intensity solar insolation using the prevailing climatic condition in Owerri, Imo state Nigeria. Results obtained show that the thermo syphon system can produce domestic heating water of temperature of about 90 0 C. The temperature profiles plotted indicate that the system designed is strongly dependent on the prevailing weather condition. Keywords: thermo-syphon, compound parabolic collectors, insolation, efficiency. I. INTRODUCTION Solar collectors are the key component of active solar water -heating systems. They gather the sun‟s energy, convert its radiation into heat, and then transfer that heat generated to a fluid. The heat generated could then be utilized in solar water-heating systems, solar pool heaters, and solar space-heating systems. There many types of collectors, prominent amongst them are the flat plate and Compound parabolic Concentrators (CPC) type. To achieve temperatures in excess of approximately 80°C from a solar collector, the solar radiation has to be concentrated. Because the relatively low temperatures attainable when flat plate collectors are used, therefore the concentration of solar radiation becomes necessary Rabl[1]. By using internal reflectors, the hot absorber area can be reduced and this reduces the heat losses. CPCs (Compound parabolic Concentrators) are here the optimal choice, since they have the capability of reflecting to the absorber all of the incident radiation. CPCs are non-imaging concentrators. They have the capability of reflecting to the absorber all of the incident radiation within wide limits. Their potential as collectors of solar energy was pointed out by Winston [2]. CPC solar collector can not only gather the solar beam to the receiver with a reflector/refractor but also utilize the beam and diffuse solar irradiation like a flat plate solar collector. Therefore, CPC solar collectors are always efficient than typical flat plate solar collector Yong et al [3] In this paper, the use of the compound parabolic collector in the operation of a thermo-syphon system is highlighted The solar thermo-syphon system basically has three components namely: the storage tank, the solar collector and the piping. Thermo-syphon systems do not have pumps rather circulation of the fluid depends on the siphoning principle occasioned by thermal effect due to density differential and gravity. Thus, the heating of a specific amount of liquid usually causes its expansion by volume and hence a reduction in its density. If that is the case, when a column is heated unequally, a density differential would result which causes the fluid being heated to flow without any external power source other than solar radiation. II. SYSTEM DESCRIPTION Schematic diagram of the thermo-syphon system under analysis is illustrated in Fig (1). It is made a CPC collector, an absorber pipe, two water storage tanks, return pipe and a support stand. The CPC has a compound parabolic reflecting surface whose line focuses on a cylindrical copper receiver/absorber surrounded by a glass envelope. The receiver is used to receive incident radiation energy is covered with a selective surface of high solar absorptance (αr) and low emittance (εr ), whilst the reflector is consist of several mirror sheets cut into size with high reflectance (ρm) and glued on the surface of the curvature .The absorber pipe is made of a copper tube painted black with inner and outer diameters of 13mm and 15mm respectively. The location of the absorber is at the focal point of the CPC collector. This is to facilitate the heat transfer between incident solar radiation and the absorber material. To further enhance the heat transfer from the concentrated ray to the receiver, the receiver was covered with a glass tube and insulators at the edges to minimize heat conduction the receiver and the reflector. The Water used as heat transfers medium flows through the receiver tube and the tank. To suppress convection losses from the receiver a glass envelope is placed around it. A transparent cover is fitted to protect the reflector surface from deterioration; and also it reduces the rates of heat loss from the receiver envelope configuration. On the other hand to reduce heat losses to the ambient the underside of the reflector is covered in insulation. The present system operation is very simple, when water is Evaluation of the Thermal Performance of a Thermo Syphon Water Heating System Using a Compound Parabolic Solar Collector Okoronkwo C.A, Nwufo, O.C, Ogueke, N.V, Nwaigwe, K.N, Anyanwu E.E Department of Mechanical Engineering, Federal University of Technology, Owerri Department of Agricultural Engineering, Federal University of Technology, Owerri Imo State Nigeria