Solar Water Heater

CHAPTER 1: INTRODUCTION 1.1 Project Definition This project is intended to design a water heating system by using solar technology. There are various design and manufacturing constraints but here the most general and efficient way would be used. It includes thorough study of the mechanism of the solar water heater. After designing such mechanism, the heater would be manufactured, and the results would be presented. Solar energy technology is used in various places in different ways. It is used to produce electricity and it provides energy which is used to cook food. Solar systems are designed in such a way that water can be heated to any temperature. But at domestic levels water can be heated up to 60 ⁰C. Evacuated types of solar heaters and glazed plate heaters are the most common types of solar powered water heaters used in the world. Some of the systems are active and others are passive. Active systems are divided into direct and indirect solar systems. In this project indirect solar system will be designed. The mechanism of our solar heater will resemble as shown in figure 1. Figure 1 Solar Heater system 10 1.2 Objectives of the project The main objectives of the project are as follows:  Study, design, and analysis of the active solar water heating system according to the domestic applications.  Modern techniques would be used to choose the economical and easily available techniques to design the solar heating system.  Design calculations would be done where needed with the help of research and analysis.  Fabrication of the solar heating system with the economical and easily available materials. 1.3 Project Specifications There are many aspects which would be looked after while designing a safe and economical systems. For the solar heater following are the main sections.  Heat Collection  Heat transfer  Heat storage  Heat backup  Extreme temperature protection. These aspects are explained in the figure 2. 11 Following are the main components of the solar heater.  Solar collector panel  Storage tank  Heat Exchanger  Expansion tank  Control System While the collector panel consists of absorber plates, tubes, glazing, thermal insulations and casing. 1.4 Applications Solar water heater can be used in domestic, commercial, and industrial applications. They are enlisted below: Figure 2 Main aspects of Solar Heater 12  Domestically hot water is used in bathing, washing of utensils and clothes and cleaning floors. Water requirement for a house depends on the number of family members. For a 4 members family, each consuming approximately 25 liters, on average above 100 liters are required.  In commercial applications, a large quantity of water is required. For this purpose, large scale heating systems are used.  In industries water is used to preheat the boiler water. Hot water is also used in food processing industries. 13 CHAPTER 2: LITERATURE REVIEW 2.1 Background From the beginning of the life on earth, sun has been the most powerful force of nature. It is one of the reasons of the existence of life on earth and contributing a lot as a basic energy source. Due to its large benefits and size, it is regarded as the god in some of the religions. In the past no major benefit was taken by humanity. But as the needs of the human are increasing and other reliable sources are decreasing. Now humans are shifting towards renewable energy sources and sun is one of the biggest sources of renewable energy. In the same way solar energy is used to heat water in the industries, steam is produced by using modern techniques. In California, first solar water heater was utilized to heat the pool water in 1970 (Bennet T, 2007). To get benefit of solar energy first started by Romans and Greeks. They built their house in such a way that solar light directly falls in and warmed their houses. But modern applications of solar energy started in 1883 as the Charles Frits developed first solar cell. In 1970s Europe and Israel invested in solar technology and reduced the cost of photovoltaic cell to compete the oil sector which was dominated by the Arab countries (Ken Butti, John Perlin, 1980). In 1983 about 60% of the households in Israel were using solar heaters to warm the water. By now around 90% of the houses in Israel are using solar water heaters. European countries are investing in solar energy and after China, Germany is producing solar energy. In the 19th century people used wood and other exhausted sources to heat the water. In some areas it was difficult to heat water as the availability of coal, wood and gas was not enough or some areas did not have access to these sources. So, a black painted container was filled with water and 14 exposed to sun. But the main flaw in this system was as the sun set, the water got cooled (Charles Smith, 1995). Solar heaters are divided into two main types. One is passive while the other is active. In passive systems, radiation or heat of the sun is directly used. This heat is either drops on the storage tanks or this heat is transferred to tank which is placed above collectors (Roger Taylor, 2006). Active solar systems are divided into two types. One is direct and other is indirect. In direct active systems, heat is absorbed by the collectors. These collectors may be in any shape. Water is being pushed with the help of pumps to circulate in the pipes surrounding the heat collectors. After heating the water is taken back to the storage tanks. In indirect systems, water is heated with the help of some heat exchanger. In domestic indirect solar heaters, water is heated inside the heat exchanger and then transferred to the storage tank (Harrison J. Tiedman T. 1997). Performance of the solar water heater is affected by the many factors. These includes ambient conditions, collector arrangement and fluid flow rate. It the atmosphere is clear, then sun will fall directly on the collector. Temperature determines the thermal loss from the collector. Area of solar collector and its orientation determine the absorption capacity of collector. In direct systems, if the flow rate of fluid is low then water is heated evenly while low heat transfer occurs if the flow rate is high (Kalogirou, S.A, 2004). 2.2 Previous Work As discussed previously that there are two types of solar heaters. One is active and passive. Passive heaters circulate water by using natural means like gravity or natural circulation. These systems are less expensive. While the active solar heaters use pumps and other equipment to force the flow 15 rate and thus it is costly and difficult to repair. Some of the research work done on these is discussed below: Soteris A. Kalogirou presented a paper which discussed the various types of collectors and their uses. The applications of the solar systems are dependent on the type of solar collectors used in the system. Solar collectors include flat-plate, compound parabolic, evacuated tubes, fresnel lens, parabolic trough and heliostat field collectors. These different types of collectors are used in different applications in domestic, commercial and industrial uses. Following is the comparison presented by him for different collectors (Kalogirou, S.A, 2004). K. Sivakumar used elliptical flat heat collector and placed this collector at 11⁰ to the horizontal. In this experiment condenser to evaporator length ratio, different flow rates and many inlet conditions were analyzed. Five evacuated pipes made of stainless steel were used. Tube was made of copper while the methanol was used as a working fluid for this setup. The experiment analyzed that ratio of lengths of condenser to evaporator of 0.1764 achieved greater efficiency (K. Sivakumar, 2005). Figure 3 Comparison of different collectors 16 Hussain Al-Madani presented research on evacuated and cylindrical tubes. Collectors consist of copper coils and water circulates in them. Different experiments were taken, and it was concluded that maximum difference of temperature occurred has a value of 27.8 ⁰C. This value shows the efficiency of 42 % (Hussain, Al-Madani, 2006). K. S. Ong worked on different solar water heaters. He and his friends used different collectors and tanks with various sizes and designs. They used short and long terms experiments and performances of different solar collectors was assessed. They concluded that in natural convection hear pipe system water was heated up to 100 ⁰C. They used different absorber and collector types and give the results as shown in the figure 4. (K. S. Ong W. L. Tong, 2011). Figure 4 Collector data with different collector types 17 2.3 Comparative Study As we have discussed various works of different researchers. They all used different criteria to assess the performance of solar water heater systems. They all used different criteria to assess the quality and efficiency of solar heater. In this project the aim of our project is to build a solar heater which is active in nature and the flow rate is caused by indirectly. Flat plate collectors will be used. Now we are in the study period, so further design constraints and material availability will affect the solar heater final product. When we will reach the final product, then suitable procedure and analysis will be carried out and will be compared with the work presented in the literature review.