This thesis would not have been possible without the guidance and the help of several individuals who contributed in one way or another and provided their valuable help in the preparation and completion of this study. We would like to thank the help and cooperation provided by the office of the Department of Mechanical Engineering, Military Institute of Science and Technology (MIST) that allowed us to use the facilities of the department. Finally, we express our gratitude to the staff in Mechanical Engineering, for the use of facilities in the Machine Tool Laboratory and for extending their helping hand for the completion of this thesis work.
Parabolic solar concentrators are a low-cost implementation of concentrated solar technology that uses parabolic trough-shaped mirrors to concentrate the incident direct normal radiation onto a receiver tube placed at the focal line of the trough. The efficiency and cost of the parabolic solar concentrator designs are affected by structural stiffness, choice of materials, mounting tolerances, mirror finish and wear. When designing parabolic solar concentrator, we tried to ensure that it should be socially acceptable, cheap, withstand rough handling and can heat effectively.
The parabolic trough collector could heat water up to 780 C in the month of September. The average experimental efficiency was 2.44% in the month of September and 2.09% in the month of October.
INTRODUCTION
GENERAL
The current installed capacity of solar PV is 15 MWe which is only 0.33% of the total power generation. PV would be a better choice to set up CSP plants for using solar energy on a large scale to minimize the current and future energy crisis in Bangladesh. Instead of generating electricity, parabolic trough collectors can be used for domestic hot water, swimming water or space heating.
OBJECTIVES OF PRESENT STUDY
AVAILABILITY OF SOLAR ENERGY IN BANGLADESH
LITERATURE REVIEW
LITERATURE
He also sold the patent rights of the Day and Night Solar Water Heater to a Florida firm. The Oil Embargo of 1973 and the subsequent dramatic rise in the price of petroleum revived the local solar water heater industry. By this time, the Japanese had chosen solar water heaters very similar to the type invented in 1909 by William J.
The government mandated the use of solar water heaters on all buildings under 27 meters in height. Currently, Israel shares with Cyprus the highest per capita consumption of solar water heaters in the world, and more than 90 percent of Israeli households heat their water with the sun. The real goliath of solar water heaters, based on the sheer number of solar water heaters in use, is China.
Almost every household in Rizhao - located in the oil-rich Shandong province - now uses a solar heater. Globally, solar water heaters have the capacity to produce as much energy as more than 140 nuclear weapons.
DEVELOPMENT OF SOLAR COLLECTORS
Experts predict that by 2010 the number of solar water heaters installed in China will be equal to the thermal equivalent of the electrical capacity of 40 large nuclear power plants. Solar water heaters saved, in 2005, the consumption of almost 70 million barrels of oil and reduced carbon emissions by tons - not bad for a technology so simple that it can be built in a tool shop that will celebrate its centennial next year next, born in America but now used mostly elsewhere. 1964) did an experiment in Dhaka to use solar energy for water heating and cooling. If the temperature difference between the collector and the ambient air exceeds 6.5 First, the integrated type solar water heater proposed by Tanishta, I. 1964), is considered to be an improvement over conventional collectors due to its reduced size General. cost, heat loss, etc.
Gupta and Grag (1968) performed a computer model for predicting the thermal performance of domestic solar water heaters using thermosiphon circulation between the collector and the insulated storage tank. Grag, HP (1974) implemented an improved solar water heater that performs a dual function of absorbing heat and storing the heated water in Joodpur. 1995) used built-in storage type (BSWH) solar water with a flat absorber plate in Dhaka during the month of January, February and March 1992.
1996) conducted a test and compared compound parabolic concentrator with flat plate collectors. 1997) studied an experimental investigation of the effect of corrugated absorber plate on the performance of collector-cum-storage solar water heater at Dhaka during the months of November, December 1994 and January, February and March 1995. Both the collectors were 114 liters in capacity a , 1998b, 1999) reported extensive research work on solar water heaters using transient method, dynamic method and dynamic method with variable weather conditions. 2000) studied flat plate collector and without glass cover with color black, blue, red and brown.
THEORETICAL ASPECTS
- METHODS OF USING SOLAR ENERGY
- Photovoltaic cells
- Active solar energy
- Passive solar energy
- Concentrating solar power systems
- ADVANTAGES OF SOLAR POWER
- TYPES OF SOLAR WATER HEATING SYSTEMS
- Types of solar water heating system
- DIFFERENT TYPES OF SOLAR COLLECTORS
- Flat Plate Collectors (FPC) Based Solar Water Heaters
- Evacuated Tube Collectors (ETC) based Solar Water Heaters
- Transpired air collectors based solar water heater
- Concentric collectors
Solar dish systems use a mirror dish to track the sun and focus solar energy onto a receiver, mounted at the focal point of the dish. However, because they are not insulated, a large part of the absorbed heat is lost, especially when it is windy and not warm outside. The heat from the hot end of the heating pipes is transferred to the transfer fluid (water or an antifreeze mixture - typically propylene glycol) in a domestic hot water space heating system in a heat exchanger called a "manifold".
This tracking method works well for spring focusing light at other times of the year. the magnitude of this error varies throughout the day, with its smallest value at solar noon). An error due to the daily movement of the sun across the sky is also introduced, this error also reaches a minimum at solar noon. The heliostats direct concentrated sunlight, magnified up to 600 times, onto a receiver that sits atop the tower.
The heated fluid is responsible for transferring the heat to the rest of the power plant.. flows into a thermal storage tank where it is stored, and finally pumped to a steam generator. Both the systems, storage and hybridization seek an improvement in the number of working hours.
EXPERIMENT
SET UP
- Design Consideration
- Concentrator
- Receiver or absorber plate
- Variable Inclined Stand
The function of the absorber plate is to absorb the solar radiation as efficiently as possible. It must convert the solar radiation into thermal energy and deliver it to the heat transfer medium (water or thermal fluid) with minimal losses. The absorption of the receiving surface for short wavelength depends on the type and color of the coating and the glazing.
Appropriate electrolyte or chemical treatments can produce a surface with high solar radiation absorption values and low long-wave radiation. In principle, receiver surfaces typically consist of a thin top layer, which is highly absorbent to short-wave solar radiation, but relatively transparent to long-wave thermal radiation, deposited on a surface with high reflectance and low emittance for long-wave radiation. Much of the progress in recent years has been based on the implementation of vacuum techniques.
It should be very thin, just enough to hide the metal surface and as uniform as possible. A glass tube is used, which is permeable to solar radiation through the surface of the solar absorber. This cannot be achieved with a fixed inclination because the direction of the sun's altitude changes throughout the year.
PROCEDURE
ANALYTICAL STUDY
PERFORMANCE ANALYSIS
Reflection loss or specular reflection is defined as the part of the incident beam which is reflected so that the angle of reflection is equal to the angle of incidence. Metal deposits or coatings may be used on the front surfaces or on the black glass. Reflection losses can be reduced by etching from 4 percent of the surface to about 1 percent at normal incidence.
The correct value of the transmission and absorption product must be obtained by integrating the radiation passing through the cover and incident on the receiver from all parts of the concentrator. Good design should make it possible to keep all angles of incidence less than 60° by shaping the receiver. The interception factor represents the function of the specularly reflected radiation intercepted by the energy-absorbing surface.
It has a major influence on the determination of stored energy and represents a significant factor in the energy balance. The intercept factor in a property of the concentrator and its orientation when produced in an image and of the receiver and its positioning relative to the concentrator when intercepting part of that image. Focusing solar collectors differ in their thermal behavior from the flat type because for receivers the shapes are very variable, the temperatures are higher, the edge effects are more significant, the conduction conditions are quite high and the radiation flux on the receivers is not uniform.
The effect of variation in direct solar radiation, selective and non-selective coatings, absorber tube material and configuration, insulation and orientation of concentrator, etc., on collector performance can be analyzed experimentally. The collector performance is described by an energy balance with the incident energy divided into optical losses, thermal losses from the receiver and the useful energy gain. In mass production, etching the cover glass for the receiver will always be cost-effective because of the relatively small area and because this glass is sufficiently well protected from the environment not to be degraded by dirt accumulation.
In concentrated collectors, the angle of incidence of some rays on the absorber will strongly deviate from the normal direction. The shell and supporting structure affect the cut-off factor and the performance of the collector depends on the ability of the structure to maintain the shape and orientation of the reflector. The shell and structure must be supported in different positions so that they have minimum distortion due to its weight.
RESULTS AND DISCUSSIONS
The centers show the temperature of the center of the receiver or absorber. From Table 6.1, the negative experimental efficiency means that the temperature decreases from its initial value.
CONCLUSIONS AND RECOMMENDATIONS
CONCLUSIONS
RECOMMENDATIONS
T1 = Fluid temperature at one end of the receiving tube (°C) T2 = Fluid temperature at the center of the receiving tube (°C) T3 = Fluid temperature at the other end of the receiving tube (°C).
