PERFORMANCE OPTIMIZATION OF HYBRID SOLAR HEATING SYSTEM USING THERMOELECTRIC GENERATOR

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1 International Journal of Advanced Research in Engineering and Technology (IJARET) Volume 7, Issue 2, March-April 216, pp. 9-2, Article ID: IJARET_7_2_2 Available online at ISSN Print: and ISSN Online: IAEME Publication PERFORMANCE OPTIMIZATION OF HYBRID SOLAR HEATING SYSTEM USING THERMOELECTRIC GENERATOR Sabah M. Hadi, Aed Ibrahim Owaid and Rasim Abbas Ahmmed Solar Researches Centre, Renewable Energies Directorate, Ministry of Science and Technology, Republic of Iraq ABSTRACT The hybrid solar system assumed to be consist of thermoelectric generator (TEG) and evacuated tube with extracted under standard condition of 1 w/m2and ambient temperature C, then the of hybrid system measured at different solar radiation and temperature. In addition the thermal and electrical are extracted. The study was done with different figure of merit (ZT) (.5, 1, 1.5, 2, 2.5, 3, 3.5, 4) of thermoelectric generator (TEG). The heat transfer coefficient of evacuated tube.89 W/k.m and temperature dependent that transfer coefficient.1w/k2. m the calculation and graphs were done by MATLAB program. Key words: Solar, Evacuated Tube, TEG,, MATLAB Cite this Article: Sabah M. Hadi, Aed Ibrahim Owaid and Rasim Abbas Ahmmed, Performance Optimization of Hybrid Solar Heating System Using Thermoelectric Generator. International Journal of Advanced Research in Engineering and Technology, 7(2), 216, pp INTRODUCTION The greatest advantage of solar as compared with other forms of is that it is clean and can be supplied without any environmental pollution. Over the past century fossil fuels have provided most of our because these are much cheaper and more convenient than from alternative sources, and until recently environmental pollution has been of little concern [1]. The solar is available in abundance and has potential to meet the current heating and electricity needs. However in most cases the solar systems are limited to providing either heat or electricity. Recently, hybrid systems are developed, either with photovoltaic or thermoelectric to generate both electrical power and thermal or heat [2]. Thermoelectric power generation is one of the current interests in clean research in view of direct solar power generation. Thermoelectric power generation be-comes an attractive application. Recent research analyses were 9 editor@iaeme.com

2 Sabah M. Hadi, Aed Ibrahim Owaid and Rasim Abbas Ahmmed proposed in the open literature to cover the various aspects of generation[3]thermoelectric have large potential to become an alternative power source for electrical power supply, as they could provide co-generation system anywhere thermal gradients exist. The most efficient way for improving the performance of thermoelectric power generation systems is to use it with hybrid systems. Thermoelectric module can be used with flat plate collectors, parabolic collectors and parabolic dish or evacuated tube collectors to generate heat and electricity simultaneously. Such hybrid system improves the overall performance of the thermoelectric power generation system which can be made cost effective [2]. This hybrid system takes several form using for example Fresnel lens which is concentrate the solar rays on the thermoelectric generator and produce the electrical power with electrical conversion of 15%from the incident solar. The hybrid system depend on three subsystem solar absorption system, thermoelectric system and electrical management [4, 5] also dish concentrator can be used within the hybrid system as the conversion and also it is highly suitable for isolated demand where the conventional grid is not feasible or available [6]. 2. THEORETICAL PART 2.1. The Hybrid System The conversion process of the solar indirectly can be done by several ways and by several kinds of the thermal units. Which depend on dish concentrator and the other on dish concentrator and so on. The thermal units convert the solar to thermal become electrical by mechanical way, so in order to prevent the mechanical way which needs special maintenances and another requirements, the researchers followed the way (STEG) which still in the process of research and training. This system consist of thermoelectric generator unit made of semiconductor materials with higher afford range of temperature than the stagnation temperature of the evacuated tube collector, which converts the solar to thermal. Figure 1 Schematic diagram of the System Arrangement. 1 editor@iaeme.com

3 Performance Optimization of Hybrid Solar Heating System Using Thermoelectric Generator Thermoelectric Generator (TEG) The global crisis has motivated researchers to explore alternative means of generating power. One approach to providing electrical is by direct conversion of heat to electricity using thermoelectric generators (TEGs). It is attractive to use TEGs because they have no mechanical parts, resulting in a power system that is silent, reliable, environment-friendly, and virtually unlimited lifetime [7]. The basic theory behind this TEG is "seebeck effect". Seebeck effect was discovered by Thomas Seebeck in When a temperature difference is recognized between the hot and cold junctions of two dissimilar materials (metals or semiconductors) a voltage is generated, this voltage is called Seebeck voltage. Indeed this phenomenon is applied to thermocouples that are extensively used for temperature measurements. When a Thermoelectric material (Thermoelectric Module or Thermocouple) held in-between temperature gradient it generate some voltage. In fact, this phenomenon is applied to thermocouples that are extensively used for temperature measurements. Base on this Seebeck effect, thermoelectric devices can act as electrical power generators [8].as shown in fig. (2)[9] Figure 2 Illustration of Seebeck effect Seebeck coefficient can be found by the equation (1) where ΔT, ΔV are temperature difference and potential difference respectively through the two junction between the two equations (2): α= T α= 2 T T As mentioned above the thermoelectric generator consist of two different materials, So the conversion of thermal depends on the physical properties of thermal conductivity and electrical conductivity for this materials, so find was associated with finding (Z)figure of merit which can be defined as it is one of the most important concepts of thermoelectric that is ability of heat conversion to electricity[1], So the finding of (Z) figure of Merit for any material concerning the thermoelectric generator must be found by the equation (3) so that(σ)represent the electrical conductivity and can be measured by ampere. volt -1. meter -1 and (λ) is thermal conductivity for the material and can be measured by watt.meter -1.kelvin -1 = editor@iaeme.com

4 Sabah M. Hadi, Aed Ibrahim Owaid and Rasim Abbas Ahmmed To find (ZT) unitless figure of merit without units by multiplying the parties of equation by (T) as shown below: = 4 2 Then the equation(3) will become as in (5) which represent (ZT) figure of merit which is unit less, this for one material but in case of two materials which the thermoelectric generator depends on, the equation will become (6) where ρρ represent the electrical resistance for the first and second material respectively: =! = [# $ % +#!! $ % ] 6 The conversion of the thermal to electrical for the thermoelectric generator can be expressed in the equation (7) where P,η,Q represent the electrical power,conversion,and thermal respectively. The of the thermoelectric generator depends on (ZT) figure of merit for two materials and on the temperature difference at both sides of the generator [4] and expressed by the equation (8), the first part of the equation represent Carnot : )=ƞ + ƞ=- T T 1+ZT+ T % T Evacuated Tube Each evacuated tube consists of two glass tubes made from extremely strong borosilicate glass. The outer tube has very low reflectivity and very high transitivity that radiation can pass through. The inner tube has a layer of selective coating that maximizes absorption of solar and minimizes the reflection, thereby locking the heat. The ends of the tubes connected to the copper header are fused together and a vacuum is created between them. This process is called as evacuation, as by definition, it means that the air is pumped out from the cavity. The vacuum is created to recreate the thermos flask effect as vacuum acts as an insulator and does not allow short wave radiation to escape through the glass tube. This traps the solar radiation much more effectively and hence higher temperatures can be achieved [11]. As shown in fig, (3). The resulted thermal from the evacuated tube collector can be found by the equation (9) and this equation is considered as a basic equation to find the thermal for several types of solar collector. + =3.4.5ƞ 6 $ Where Q coll, A, η ο,a 1,a 2,T m,t a, and G are the thermal emerging, the area of the thermal collector, the greatest, heat transfer coefficient,heat transfer coefficient in terms of the temperature, the average of the fluid temperature in the solar collector, the ambient temperature,and the solar radiation on the solar collector respectively [12] 12 editor@iaeme.com

5 Performance Optimization of Hybrid Solar Heating System Using Thermoelectric Generator 3. THE CALCULATION Figure 3 Photographic picture for evacuated tube Calculation of amount of change obtained with the difference in the temperature of the heat transfer fluid within the evacuated tube In order to calculate the amount of change in the produced by the solar thermal collector for the total area of 1 m 2 and with solar radiation of 1 w/m 2, ambient temperature ( C), heat transfer coefficient (.89 w/m 2 k), and heat transfer coefficient in term of temperature (.1 w/m 2 k), and using equation (9) with helping of the MATLAB program, the results would be shown in figure (4): 6 G=1 w/m 2 55 y = -.1*x *x + 5.9e+2 5 Collector [w/m 2 ] of mean collector fluid and ambient temperature C Figure 4 The Graph shown the change amount of the resulted from the evacuated tube collector of area (1m 2 ) with the change of temperature average of heat transfer fluid editor@iaeme.com

6 Sabah M. Hadi, Aed Ibrahim Owaid and Rasim Abbas Ahmmed 3.2. Calculation of the amount of change obtained with change of radiation intensity and with the change the difference in temperature of the heat transfer fluid. After getting the amount of change in the resulted from the assumed solar collector of a total aperture area (1m 2 ) with the change average of temperature difference for the heat transfer fluid with solar radiation (1W/m 2 ) under same conditions of aperture, ambient temperature, thermal conductivity coefficient, and thermal conductivity in terms of temperature but with solar radiation intensity from 1 W/m 2-9W/m 2 as shown in figure (5). Figure 5 Graph illustrated changing amount of change obtained with change of radiation intensity from 1W/m 2-9W/m 2 and with the change the difference in temperature of the heat transfer fluid. 4. Calculation of Hybrid System Through this study and from the resulted thermal by the solar thermal collector under the ambient temperature C, radiation intensity 1 W/m 2 and change in heat transfer fluid temperature, the thermal of the collector can be calculated,also the electrical for the (TEG) can be calculated by the equation (9), so the result can be shown in tables(1,2,3,4,5,6,7,8)with ZT figure of merit (.5, 1,1.5,2,2.5,3,3.5,4)respectively editor@iaeme.com

7 Performance Optimization of Hybrid Solar Heating System Using Thermoelectric Generator Table 1 Show the result of the electrical and thermal when the intensity is 1W/m2, temperature ᵒC and figure of merit Table 2 Show the result of the electrical and thermal when the intensity is 1W/m 2, temperature C, and figure of merit editor@iaeme.com

8 Sabah M. Hadi, Aed Ibrahim Owaid and Rasim Abbas Ahmmed Table 3 Show the result of the electrical and thermal when the intensity is 1W/m 2, temperature C, and figure of merit Table 4 Show the result of the electrical and thermal when the intensity is 1W/m2, temperature C, and figure of merit editor@iaeme.com

9 Performance Optimization of Hybrid Solar Heating System Using Thermoelectric Generator Table 5 Show the result of the electrical and thermal when the intensity is 1W/m2, temperature C, and figure of merit Table 6 Show the result of the electrical and thermal when the intensity is 1W/m 2, temperature C, and figure of merit editor@iaeme.com

10 Sabah M. Hadi, Aed Ibrahim Owaid and Rasim Abbas Ahmmed Table 7 Show the result of the electrical and thermal when the intensity is 1W/m 2, temperature C, and figure of merit Table 8 Show the result of the electrical and thermal when the intensity is 1W/m 2, temperature C, and figure of merit From the data in tables the maximum electrical at different values of figure of merit and at average of heat transfer fluid temperature equal to ᵒC, as illustrated in figure (6), and The maximum total at different values of figure of merit and at average of heat transfer fluid temperature equal to 5ᵒC this is explain in figure (7) editor@iaeme.com

11 Performance Optimization of Hybrid Solar Heating System Using Thermoelectric Generator.16 maximum electrical y = -.62*x *x +.35 R square =.99 data 1 quadratic ZT Figure 6 Graph represents the increasing amount the maximum electrical at different values of figure of merit and at average of heat transfer fluid temperature equal to C maximum total ZT Figure 7 Graph represent amount of maximum total at different values of figure of merit and at average of heat transfer fluid temperature equal to 5ᵒC. 6. CONCLUSION After studying the basic of the evacuated tube and thermoelectric generator working and after the knowledge of of conversion for each one under defined measurement conditions to produce these types of generator (the evacuated tube convert the solar to thermal, and the thermoelectric generator convert the thermal to electricity)it was conclude the following: Within the considering measurement conditions the amount of and temperature must be matched within the production range of the electrical power for the thermoelectric generator. It was noted that from the specifications of the 19 editor@iaeme.com

12 Sabah M. Hadi, Aed Ibrahim Owaid and Rasim Abbas Ahmmed thermoelectric generator and the solar collector get near in terms of operating age and environmental friendly. The highest electrical when the averages of heat transfer fluid temperature equal to C. The highest total when the averages of heat transfer fluid temperature equal to 5 C. It was shown that electrical power generated from this hybrid collector is enough electrical power to turn the heat transfer fluid, so that no need to use the external electric source. REFERENCES [1] Soteris A. Kalogirou, 24, Solar thermal collectors and applications, Progress in and Combustion Science, 3, pp [2] N.S.Sathawane, Dr. P.V.Walke, 214, A review on solar thermoelectric cogenerator with evacuated tube solar collector, IJARSE, 3, pp [3] Jarman T. Jarman1, Essam E. Khalil, Elsayed Khalaf, 213, Analyses of Thermoelectric Renewable Sources "Open Journal of, 2, pp [4] M. L. Olsen, E. L. Warren, P. A. Parilla, E. S. Toberer, 214, A hightemperature, high- solar thermoelectric generator Prototype, Procedia,49, pp [5] Lauryn L. Baranowski,a G. Jeffrey Snyder, 212, Concentrated solar thermoelectric generators, Environ. Sci., 5, pp [6] M.Eswaramoorthy, S.Shanmugam, AR.Veerappan,213, Experimental Study on Solar Parabolic Dish Thermoelectric Generator, International Journal of Engineering (IJEE) Jun., 3, PP [7] Babu.Uppalapati, Design and Anlysis of Modified Hybrid Solar System Using Nano Fluids. International Journal of Design and Manufacturing Technology, 6(2), 215, pp [8] Mahendra Pratap Singh and Dr. Anil Kumar Sharma, Eyes Detection Using Morphological Image Processing Through Matlab. International Journal of Advanced Research in Engineering and Technology, 4(7), 213, pp [9] Maria Theresa de Leon, Harold Chong, and Michael Kraft, 212, Design and Modeling of SOI-based solar thermoelectric generators, Procedia Engineering, 47, pp editor@iaeme.com