The Solar Energy Transfer Efficiency of a Flat-Plate Solar Energy Collector - Report Example

FLAT PLATE COLLECTOR Table of contents 1.0 Project background 3 1.1 Problem statement 9 1.2 Objectives 9 1.3 Scope of work 10 1.4Delimitations 10 1.5Assumptions 10 2.0 Methodology 11 2.1Theoretical framework 11 2.1.1Knowledge 11 2.1.2 Persuasion and decision 11 2.1.3 Implementing and confirming 12 2.2 Data required 12 2.2.1 Absorber plates 12 2.2.2 Thermal insulation 13 2.2.3 Selective absorber 13 2.2.4 Ethical consideration 14 2.2.5 Researcher qualification 14 References 15 Appendix 1:Research timeline 16 1.0 Project background All plants and animals including human beings depend on solar energy as their primary source of energy. The future of clean energy supply on the planet has its solution in harnessing solar power. Indeed the role played by energy in bringing about the modern civilization cannot be over emphasized, and in the modern civilization, there is even higher demand for energy both for domestic and industrial use. Solar radiation reaches the earth surface after transmission by electromagnetic waves (Kundu B.,2002). Solar radiation provides the planet with huge amount of energy and the energy and the solar energy has been put to use for many centuries in heating and drying. One of the most successful for of solar application is solar water heating that includes concentrating collectors, flat plate and evacuated tube. Flat plate collector (FPC) may thought of as being a special heat exchanger where there is transformation of solar radiation energy to internal energy by use of a working fluid mostly water. FPC is a popular solar collector in the market that is used in water heating which involves simple design, that are simple to operate and need minimum maintenance and it is thus common in a domestic home. When it come solar-energy, there is a lot of emphasis on developing what is considered to be passive solar energy system that is composed of a number of subsystems namely: the fluid transport and distribution systems, the flat plate collectors, the control systems and the heat storage containers. The flat plate collector is seen as the major component on the passive systems and it is responsible for absorption of the solar radiation, where the radiation is converted to heat at the absorbing surface and the heat is then transferred to the fluid (water for this case) that is flowing in the flat plate collector. The warmed water carries the heat directly to the hot water or to a storage subsystem and from this point the water can be utilized at night or when the conditions are cloudy both the conditions resulting to low temperature. From the beginning of the 20th century there have been many solar collector designs that have been found to be functional. With high energy crisis, there has been deliberate effort towards developing new energy sources as a way of solving energy problems and this has seen solar energy technologies receiving a lot of attention. Solar energy has not been put into full use as a method of large source of power can be generated. This is because the amount of energy that is generated from solar is highly dependent on time exposure to the sun and may only be useful as a secondary power supply source. In order for energy to be effectively to be harnessed from a moving energy source such as the sun it required equipment that costs considerably high amount of money and as a result the current cost of solar energy is found to be considerably high in comparison to other conventional energy sources such as hydro energy. However, with the ever increasing prices of fossil and nuclear, solar energy may come in to play a substantial role as a source of energy. This is possible if the efficiency of production is increased and the cost of equipment reduced and when looking at things from this angle solar energy may seen as one of the best energy sources that is easily available. There are a lot of ongoing research on utilization of the available solar energy to the full benefit of human kind. For the betterment of mankind, now a day for various applications with solar energy is in use still. Lot of research work is going on to use the available solar energy to maximum extent. One such area is tracking mechanism to obtain maximum energy. Just by keeping the collector fixed; it is not possible to get maximum energy from sun. It is possible to obtain the maximum energy only when it is rotated along the sun direction. In this context, tracking plays an important role. Tracking is desirable for orienting a solar device towards the sun there by collecting maximum solar energy and improving efficiency. This advantageous to water heater collector applications and this mechanism has been found more advantages than fixed flat plate collector. In this project there is investigation of increasing of efficiency for FPC through selection of materials and appropriate designs. The various parameters associated with various materials will be investigated to find out the impact on efficiency of the designs when various materials are chosen over the others. The project is to involve analysis that will be important in obtaining FPC efficiency for various material combinations. The effectiveness in this project is dependent on having knowledge of heat transfer as well as solar thermal. The principles behind FPC are making sure there is as much as possible absorption heat radiation from the sun through heat absorption process. There is transfer of the energy which has been collected by the working fluid (water) that is made to pass through conduit tubes which are appropriately placed next to absorber plates. The warmed water is carried to a storage subsystem or hot water system where it will be put to use at the time when the weather is cold (John A. Duffie and William Beckman, 2006). The ability of absorbing more energy is of great importance in FPC as it determines the level of performance with the heat absorber plate serving as the most vital component of the FPC (Sukhatme, S. P. 1984).). More absorption of heat from the sun by the absorber plate means a higher outlet temperature (Tout) can be obtained with the inlet temperature (Tin) being much lower (P. Rushi Prasad,2006). While there are many FPC concepts being developed, the simple FPC find the highest with its characteristics being known it is found to be the easiest and least expensive with regards to installation, fabrication and maintenance when compared to types of collectors. This FCP also has the uniqueness of being able to use the diffuse as well as direct beam solar radiation. With regards to residential and commercial use, FPC has the capability of producing heat temperatures high enough for heating swing pools, heating buildings; heating of domestic water in addition the system can also be used in operating a cooling system especially where there is use of a reflector in increasing the incident sunlight. Obtaining temperature ranges of 40 ºC to 70ºC is possible with FPC and with careful engineering by use of special surfaces reflecting surfaces for increasing the incident radiation incorporated with materials of high heat resistant materials it is possible to have the system operating at a much higher temperatures. With regards to the absorber plate the material selected should be able to absorb solar energy at a high rate and then transfer it within the shortest time to tubes or fins that are attached in a manner to enable a very good thermal bond. The glazing is another component of FPC which may consist at least one sheet of glass or a diathermanous material ie a material in which there can be transmission of radiation be it a plastic film or sheet. Figure 1 Source: Duffie, J.A. Beckman, W.A. (1991). Thermal insulation just beneath the tubes serves to ensure the heat loss down the plate is kept minimal while the cover strip serves solely as a structural component that holds all the other components in place and to make the assembly to be water tight. The water-type (hydronic) and air-type are the two classifications of FPTs: with the former involving use of water as the heat-transfer fluid while in the later as is the heat-transfer fluid. From figure 2 some of the flat plate solar collectors which are currently available both for hydronic type and air type. In the A (1,2) is an illustration of a conventional liquid heaters having tubes that are soldered or otherwise secured to the upper or lower surfaces of the metal sheets through fastening. Some of the devices that have been applied for securing the pipes include clips, twisted wires, clamps, thermal cements among others where varied success level has been achieved. In A3 we have bonded sheet design where there is integration of the tubes with the sheet, and this is guarantees good thermal connection of the tubes and absorber plates. This process is what is widely used in commercial production of radiators and other forms of heat radiators. In B and D there is a dispalay of a variety of ways of fastening galvanized steel sheets so as to come up containers that are completely water tight with individual passages being provided. In C there is illustration of application of parallel sheet of aluminium, galvanized steel or copper that are dimpled and then fastened together at appropriate intervals either by riveting of spot welding. Figure 2 Duffie, J.A. Beckman, W.A. (1991). 1.1 Problem statement The amount of heat that is absorbed by the heat absorber plate and maintenance is a key issue when it comes to the performance of FPC. The efficiency level of FPC is given as the ratio between the useful gain in some specified period of time over the total incident solar energy available over the same period of time (Carg H. P. ,1982). The amount of heat absorbed by FPC is dependent on the thermal properties exhibited by the material used as well as the design of the FPC components. The materials that the heat absorber place is made of plays a very important role with regards to absorption ability owing to their thermal properties. The thickness of the absorber plate, the length of the tubes used and their materials also are very important. In this project there will be analysis of the performance that is expected from FPC for a variety of materials and for various design types. The optimization of thickness and material used in the design of the FPC will yield the desired effect to maximize its efficiency. 1.2 Objectives The project is conducted with the following objectives to be achieved: ( i ) To establish the variation in efficiency in FPC for various materials for the same design ( ii) To analyze the effect of varying dimensions in flat plate collector efficiency. (ii) Establish the optimal size of material that will yield highest performance 1.3 Scope of work The project has to focus on the following scopes in order to achieve the objectives: ( i ) Conducting literature review regarding flat plate collector (FPC). ( ii ) Investigating the thickness effect of different material absorber plate on the flat plate collector (FPC). 1.4Delimitations 1. This study concentrates on only FPC and it does not feature other technologies like the concentrating collectors 2. The study will rely on information from previous experiment and that it will be assumed that this information is true 3. This study does not go into the extent of constructing the FPC 1.5Assumptions The project looks at different materials that can be used in design and the parameters used are those obtained from previous research. The assumption is that all the data all data is true and that the materials that conform to these parameters are readily available and can be used for FPC. In this project we look at the performance of different types of materials and the assumption is that all the materials can be available for practical design 2.0 Methodology 2.1Theoretical framework The study will be guided by Diffusion Innovation Model adapted by Rogers. Diffusion is the process by which an innovation is communicated through certain channel over time among the members of social systems (Rogers). The theory notes the part played by attitude of people when it comes to adapting to new technology. Rogers theory advocates that innovations diffusion is a process that takes time to occur and that it takes place in five stages. The five stages are: 2.1.1Knowledge According to Roger’s model the knowledge about the technology about the new technology is very important. In this study the knowledge of the people on FPC as a source of clean energy is important. The knowledge is found through the through publication of materials on FPC and demonstration of the technology to people at appropriate places like agricultural show grounds, science exhibitions etc. 2.1.2 Persuasion and decision Persuasion is important as it gives rise to the willingness to at least to attend to the innovation. The teachers and student will now be able to attend selectively to various aspects of the context within the innovation. The potential adapters of FPC technology will need to be convinced of the appropriateness of FPC technology with emphasis on it being a clean energy, simple and cost effective. 2.1.3 Implementing and confirming At this stage the potential recipient of a new technology will be convinced of its worthiness and will be fully be willing to adopt to it. At this point the recipient will convinced of the validity of the technology and will express their commitment to adapting to the technology. At this stage the recipient will also act as advocates of the FPC technology. 2.2 Data required The diathermonous materials (glazing) are an important component of the FPC. The glazing is the material that receives the solar energy and transmits inside the FPC. This project will look at the various characteristics of glazing which are reflection (ρ), absorption (α), and transmission (τ). For good performance of FPC materials where the first two parameters are low will be preferable while the later need be high in order to have better performance. 2.2.1 Absorber plates The absorber plate is a component of the FPC which should be made of materials that can absorb the highest possible radiation that is emanating from the glazing and with very little of the heat absorbed being lost back to the atmosphere or downwards at the back of the container but should retain the heat and transfer it the working fluid. The materials that are desirable for this function are to be selected on the basis of their thermal conductivity, availability and cost, their level of durability and ease of fabrication of handling. In most cases the absorber plate will be coated mostly with a black paint so as to increase the absorption ie absorptance α. The surfaces of the good absorber plates will be expected to withstand exposure to high levels of temperatures frequently without the material deteriorating or gassing. Ideally the surface of the absorber plate should behave like a black body having both the emittance ε and the absorptance α being 1. In practice we do not expect to have such material perfect material and in this project we will be investigating what materials are available their durability, cost performance. 2.2.2 Thermal insulation Insulation in FPC is important as it serves to reduce the amount of heat that is lost through conduction and convection either at the back or sides of the collector. When choosing the material that is to serve for this purpose , the dimensional and chemical stability at high temperatures is an important aspect and the material should be able to offer high resistance to weathering and dampness in condensation. Some of the issues that hinders use of certain materials such as melting at some high temperatures that are attainable in FPC and some materials being unstable at high temperatures will be looked into. Different solar system will differ in terms of the collector area, the absorber area, the coating used, the plate material to be used and their thickness, the tube materials and their diameter. With all this variation there is a high opportunity to improve the performance of existing designs or retain the performance but use cheaper materials or still use much more durable materials than are being used currently. 2.2.3 Selective absorber One of the challenges with having a high performance FPC is that we need to have materials with high absorptance but should be poor radiators. Most materials that have high absorptance will be found will be found to have high infrared emittance meaning that they are good heat radiators. A black paint on a flat surface will have high absorptance in the range of 0.96 but will equally give off substantial amount of the heat energy with the exact amount being dependent on the temperature level where the higher the temperature the higher the radiation level. The ideal situation is to have selective surfaces, with all the incident solar being absorbed and with zero emittance as this will ensure maximum heat transfer to the working fluid. The selective absorbers are manufactured and have some deviation for the ideal. This project will involve analysis of the available materials in terms of performance, durability and cost. 2.2.4 Ethical consideration In this research secondary data will play a great role and there will be minimal involvement with practical work or going to the field for data collection. This means that the need for observing ethical issues when collecting data at the field level does not apply. However there will be use of secondary data which will need to follow the right channel to obtain if not freely available on internet. It is expected that there will be no objection for using the data from the secondary sources bearing in mind that this is strictly for academic purposes. The data sources will be fully acknowledged through referencing. 2.2.5 Researcher qualification The research is well qualified in the research area since he is pursuing engineering degree. He also has great passion in clean energy production. References Carg H. P. (1982). Treatise on solar energy; Volume 1: Fundamentals of solar energy. John Wiley, New York Kundu B. (2002). Performance analysis and optimization of absorber plates of different geometry for a flat-plate solar collector: A comparative study, Applied Thermal Engineering 22 999–1012. Drago.P(2008) Solar energy. Duffie, J.A. Beckman, W.A. (1991). Solar Engineering of Thermal Process, Wiley Inter science, New York. Sukhatme, S. P. (1984). "Solar Energy-Principle of Thermal Collection and Storage", Tata McGraw Hill Pub, Co., Delhi, Rhushi Prasad (2006) Experiment Analysis of Flat Plate Collector and Comparison of Performance with Tracking Collector Appendix 1:Research timeline Task Month1 Month2 Month3 Month4 Month5 Month6 Month7 Proposal Start End Data collection Start End Data analysis Start End Discussion/conclusion Start End First Draft Start End Final draft Start End Read More

With the high energy crisis, there has been a deliberate effort towards developing new energy sources as a way of solving energy problems and this has seen solar energy technologies receiving a lot of attention. Solar energy has not been put into full use as a method of a large source of power can be generated. This is because the amount of energy that is generated from solar is highly dependent on time exposure to the sun and may only be useful as a secondary power supply source. For energy to be effective to be harnessed from a moving energy source such as the sun, it required equipment that costs a considerably high amount of money and as a result, the current cost of solar energy is found to be considerably high in comparison to other conventional energy sources such as hydro energy.

However, with the ever-increasing prices of fossil and nuclear, solar energy may come in to play a substantial role as a source of energy. This is possible if the efficiency of production is increased and the cost of equipment reduced and when looking at things from this angle solar energy may see as one of the best energy sources that are easily available. There is a lot of ongoing research on the utilization of the available solar energy to the full benefit of humankind.

For the betterment of mankind, now a day for various applications with solar energy is in use still. A lot of research work is going on to use the available solar energy to the maximum extent. One such area is the tracking mechanism to obtain maximum energy. Just by keeping the collector fixed; it is not possible to get maximum energy from the sun. It is possible to obtain the maximum energy only when it is rotated along the sun's direction. In this context, tracking plays an important role. Tracking is desirable for orienting a solar device towards the sun thereby collecting maximum solar energy and improving efficiency. This advantageous to water heater collector applications and this mechanism has been found more advantages than fixed flat plate collectors.

In this project, there is an investigation of increasing efficiency for FPC through a selection of materials and appropriate designs. The various parameters associated with various materials will be investigated to find out the impact on the efficiency of the designs when various materials are chosen over the others. The project is to involve analysis that will be important in obtaining FPC efficiency for various material combinations. The effectiveness of this project is dependent on having knowledge of heat transfer as well as solar thermal.

The principles behind FPC are making sure there is as much as possible absorption of heat radiation from the sun through the heat absorption process. There is the transfer of the energy which has been collected by the working fluid (water) that is made to pass through conduit tubes which are appropriately placed next to absorber plates.  The warmed water is carried to a storage subsystem or hot water system where it will be put to use at the time when the weather is cold (John A. Duffie and William Beckman, 2006). The ability to absorb more energy is of great importance in FPC as it determines the level of performance with the heat absorber plate serving as the most vital component of the FPC (Sukhatme, S. P.  1984).). More absorption of heat from the sun by the absorber plate means a higher outlet temperature (Tout) can be obtained with the inlet temperature (Tin)  being much lower  (P. Rushi Prasad,2006).

While many FPC concepts are being developed, the simple FPC find the highest with its characteristics being known it is found to be the easiest and least expensive with regards to installation, fabrication, and maintenance when compared to types of collectors. This FCP also has the uniqueness of being able to use diffuse as well as direct beam solar radiation. With regards to residential and commercial use, FPC has the capability of producing heat temperatures high enough for heating swing pools, heating buildings; heating domestic water, also, the system can be used in operating a cooling system, especially where there is the use a reflector in increasing the incident sunlight.

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