Design and Construction of a Solar Water Heater Based on the Thermosyphon Principle
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Ashdin Publishing Journal of Fundamentals of Renewable Energy and Applications ASHDIN Vol. 3 (2013), Article ID 235592, 8 pages publishing doi:10.4303/jfrea/235592 Research Article Design and Construction of a Solar Water Heater Based on the Thermosyphon Principle Nosa Andrew Ogie,1 Ikponmwosa Oghogho,2 and Julius Jesumirewhe3 1Mechanical Engineering Department, Petroleum Training Institute, P.M.B. 20, Effurun, Delta State, Nigeria 2Electrical and Information Engineering Department, Landmark University, P.M.B. 1001, Omu-Aran, Kwara State, Nigeria 3Mechanical Engineering Department, Igbinedion University, Okada, 1090 Edo State, Nigeria Address correspondence to Ikponmwosa Oghogho, [email protected] Received 4 June 2012; Revised 13 January 2013; Accepted 13 February 2013 Copyright © 2013 Nosa Andrew Ogie et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract A solar water heating system for domestic use has been de- problems of environmental conservation, and global climate signed and constructed using locally available materials. Solar energy change and other air pollution issues caused mainly by is received by a flat-plate collector consisting of a thin absorber plate, burning of these hydrocarbon as a source of heat energy, integrated with underneath grids of fluid carrying tubes, and placed in an insulated casing with a transparent glass cover having a cold and a has led to the drive to use environmentally friendly and hot water tank integrated in the system. The radiation emitted by the renewable alternative sources of heat energy to eliminate or absorber plate cannot escape through the glass, thus increasing its tem- minimize these negative effects. Presently, solar and other perature. The water gets heated and flows into a storage tank through alternative energy resources are being harnessed for various thermosyphon principle. Maximum fluid output temperature, the col- lector temperature, and insolation of 55 °C, 51 °C, and 1,480 W/m2, applications such as power generation, air-conditioning, respectively, were obtained on a sunny day. This solar water heating space heating, domestic hot water system, etc. [5]. system finds useful application and acts as a renewable energy resource Solar energy being transmitted from the sun through in regions where there is abundant and consistent sunlight. space to earth by electromagnetic radiation must be Keywords thermosyphon; heat; solar water heaters; solar energy; converted to heat before it can be used in a practical design and construction heating or cooling system. Since solar energy is relatively dilute when it reaches the earth, the size of a system used 1. Introduction to convert it to heat on a practical scale must be relatively Renewable energy resources of which the sun is a good large. Solar energy collectors, the devices used to convert example are those resources which undergo a faster the suns radiation to heat, usually consist of a surface replenishment rate within a relatively short time than that efficiently absorbs radiation and converts this incident the rate at which they are utilized or depleted. The energy flux to heat which raises the temperature of the absorbing of the sun is generated from the nuclear fusion of its material. A part of this energy is then removed from the hydrogen into helium, with a resulting mass depletion rate absorbing surface by means of heat transfer fluid that may of approximately 4.7 × 106 tons per second. The earth’s either be liquid or gaseous. One of the simple forms of solar population currently needs 15 terawatts of power in total, energy collectors built is the flat-plate collector. It differs in but the solar radiation that reaches the earth on a continuous several respects from more conventional heat exchangers. basis amounts to 120,000 terawatts; hence, just a fraction The later usually accomplish a fluid-to-fluid exchange with of the suns energy reaching the earth will cover the bulk of high heat transfer rates but with emitted radiation as an energy requirements [2]. unimportant factor. About 36 years ago, the world experienced a major Focusing systems have the following challenges which oil crisis which started a new way of energy thinking are absent in flat-plate collectors: complications of optical which focused on developing alternative energy resources, characteristics of concentrator, non-uniform fluxes on the which would be renewable and environmentally friendly. absorbers, wide variation in shape, temperature and ther- Several challenges such as the increase in oil demand mal loss characteristics of absorbers, and introduction of accompanied with oil price rise, depletion of oil reserve, additional optical factors into the energy balance. Flat-plate reduced availability of fossil fuel, ozone layer depletion, collectors unlike focusing systems are designed for applica- health hazards, relatively tangible problems of aesthetics to tions requiring energy delivery at moderate temperatures up 2 Journal of Fundamentals of Renewable Energy and Applications to perhaps 80 °C above ambient temperature. They have the part of the absorber plate are examples of systems which advantages of using beam and diffused solar radiation, not generate both thermal and electrical energy simultaneously requiring orientation toward the sun, no significant optical [8,10]. They can generate electricity and produce hot air or loss terms, and requiring little maintenance. hot water at the same time. Spiral flow absorber collectors, In a review of solar water heating systems for domestic which are designed in the form of a continuous coil or tube and industrial applications carried out by Ogueke et al. [13], having at least one inlet and outlet so as to allow fluid to water heating systems were grouped into two broad cate- enter and to exit from coil, respectively, help to improve gories (passive and active), each of them operating in either on the combined PV/T efficiency and the mass flow rate direct or indirect mode. They reported their performances, [8]. The study carried out by Ibrahim et al. [8]showed uses and applications, and factors considered for their selec- that spiral flow absorber collector at temperature of 55 °C tion. The active systems generally have higher efficiencies, (panel temperature) achieved the best mass flow rate at − their values being 35%–80% higher than those of the passive 0.011 kg sec 1 and generated combined PV/T efficiency systems. They are more complex and expensive. Accord- of 64%, with 11% of electrical efficiency and power ingly, they are most suited for industrial applications where maximum of 25.35 W; while a single-pass rectangular the load demand is quite high or in applications where the collector absorber obtained the best mass flow rate at − collector and service water storage tank need not be close to 0.0754 kg sec 1, when the surface temperature was 392 °C, each other or for the applications in which the load requires generated combined PV/T efficiency of 55%, with 10% of more than one solar collector. On the other hand, the passive electrical efficiency and maximum power of 22.45 W. systems of which this work is an example are less expensive Some countries like Nigeria have abundant available and easier to construct and install. They are most suitable solar energy from which useful energy can be harnessed for domestic applications and in applications where load for several purposes (despite the draw-back of night heat demand is low or medium. losses); hence, the development of this low cost solar water Chuawittayawuth and Kumar [3], in their work, pre- heater (constructed using a high percentage of locally sented details of experimental observations of temperature available materials) aimed at providing energy for heating and flow distribution in a natural circulation solar water water for domestic use with all the attendant advantages. heating system and its comparison with the theoretical mod- Being low cost, some features that will increase its cost were els. The measured profile of the absorber temperature near not integrated in the system so that it will be affordable by a the riser tubes (near the bottom and top headers) conformed larger population of the people. well with the theoretical models. The values at the riser 2. Materials and methods tubes near the collector inlet were found to be generally A careful study of already existing solar water systems much higher than those at the other risers on a clear day, was done; and a choice was made on the type of system while on cloudy days, these temperatures were uniform. The to be designed with focus on simplicity, installation, and mean absorber plate and mean fluid temperatures during a maintenance cost as well as durability [1,3,4,6,9,14]. Use day were estimated and compared with theoretical models. of locally available materials was made a matter of priority. The temperature of water near the riser outlets was found to A flat-plate collector was used as the absorber. It was inte- be fairly uniform especially in cloudy and partly cloudy days grated with underneath grids or coils of fluid carrying tubes at a given plane during a day. The temperature of water in and placed in an insulated casing with a glass or transparent the riser was also found to depend on its flow rate. Measure- cover. A cold water tank placed above and a hot water tank ments of glass temperature were also carried out in the work. below incorporated with a thermometer and a carriage are Michaelides et al. [11] presented experimental investi- integrated in the system. The water gets heated up and flows gation of the night heat losses of hot water storage tanks into a storage tank through thermosyphon principle.