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Open accessJournal ArticleDOI: 10.1155/2014/757618

Study on Effect of Number of Transparent Covers and Refractive Index on Performance of Solar Water Heater

01 Sep 2014-Vol. 2014, pp 1-11
Abstract: Liquid flat plate collector (solar flat plate collector) is one of the important applications in solar thermal system. The development in solar photovoltaic is an emerging challenge for the solar thermal system. In the current work an attempt has been made to optimize the number of transparent covers and refractive index to improve the optical efficiency and thermal efficiency for the collector. Performance of the liquid flat plate collector at VIT University Vellore has been simulated numerically for January 21st at an interval of half an hour with different numbers of transparent covers (0–3) and different refractive index values ranging from 1.1 to 1.7. The formulation and solutions are developed with simple software Microsoft Office Excel to result the performance characteristics. The result shows that the efficiency of the flat plate collector increases with an increase in number of covers and decreases after an optimum number of covers. It also decreases with an increase in refractive index. The combination of optimum number (two) and lower refractive index (1.1) results improved useful heat.

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Topics: Photovoltaic system (54%)
Citations
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Journal ArticleDOI: 10.1016/J.EST.2019.101118
B. Kalidasan1, A.K. Pandey2, Syed Shahabuddin3, Mahendran Samykano4  +2 moreInstitutions (4)
Abstract: Solar thermal systems (STSs) are gaining boom in the globalized market since last two decades to combat the menace of global warming. Considerable research has been carried out in the field of solar thermal system for efficiency enhancement. Improvement in terms of efficiency and performance would make solar thermal systems a better option for replacing the conventional energy systems. Phase change Materials (PCMs) have emerged as an alternative to enhance the performance of the solar heating systems by acting as thermal storage batteries. In this review article an attempt has been made to consolidate the global trends and practices that has been underwent incorporating Phase change materials (PCMs) in solar thermal systems. Research on PCM based solar cooker has found to be extinct. PCM based PCM based high temperature power plant applications are on current trends of research. Application of phase change materials for low, medium and high temperature solar thermal systems are comprehensively reviewed and discussed in this article. As well the environmental benefits in terms decline in CO2 emission, due to the use of STS in day-today life and the economic analysis of PCM based STS in terms of cost and payback period is presented.

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Topics: Thermal energy storage (57%), Power station (50%)

61 Citations


Open accessJournal Article
Abstract: Solar energy can be converted into useful energy in the form of thermal energy. One of the most efficient methods is to harvesting heat energy by using solar flat plate collector. The function of solar collector is to heat water from the atmospheric temperature. The heated water can be used for domestic and industrial applications etc. The efficiency of the solar collector is depend with many parameters such as  number of glass cover, wind velocity, space  between absorber plate to the glass cover and overall top loss heat transfer coefficient out of which top loss heat transfer coefficient top loss (U t ) plays an important role for design of solar collector. Taking this point under consideration the present work is to reduce the overall top loss heat transfer coefficient and improve the collector efficiency. A double glaze system was introduced and optimized the space between the absorber plate to glass cover (1) and glass cover (2)were considered to analysis the overall top loss heat transfer coefficient (U t ). The single and double glazing solar flat plate collectors were fabricated with same dimensions and installed at a latitude angle of 12 degree facing towards N-S direction. The experiment has been carried out between 10.00 AM to 4.00 PM with thermosyphon principle. The result shows that the efficiency of double glazing is higher compared to single glazing system with same solar intensity. The higher efficiency has obtained because of the overall top loss heat transfer coefficient was reduced in double glazing system. However, the efficiency of collector is not constant; it varies with wind velocity, convective, radiative heat transfer coefficient and solar intensity.Â

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22 Citations


Journal ArticleDOI: 10.1016/J.RENENE.2016.12.060
M. Natarajan1, Tangellapalli Srinivas1Institutions (1)
01 May 2017-Renewable Energy
Abstract: A novel gravity based passive solar tracking mechanism; suitable to a linear solar concentrating collector has been conceptualized, developed, simulated, analyzed and tested experimentally. Attempt has been made to minimize the tracking load and error by controlling in dripping rate or filling rate of liquid in the gravity system. The identified key influencing design parameters in the proposed mechanism are sprocket wheel radius, spring stiffness and tracking radius. Large sprocket wheel, low stiff spring and small tracking radius minimizes the tracking loads. The recommended sprocket wheel radius and tracking wheel radius are 125 mm and 60 mm respectively. The simulation studies are validated with the experimental results. Practically obtained collector’s incidence angle is compared with the minimum required (theoretical) incidence and found a satisfactory match. The improvement in thermal efficiency of the collector with the proposed tracking mechanism has been highlighted by comparing the efficiency of intermittent tracking collector.

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Topics: Sprocket (54%), Radius (52%), Tracking (particle physics) (51%)

8 Citations



Open access
01 Jan 2018-
Abstract: Solar energy can currently be transformed into electricity and heat through photovoltaics (PVs) and solar thermal collectors respectively, particularly in household and residential applications. However, the intermittent supply of solar energy - e.g. duri

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Topics: Solar energy (80%), Photovoltaics (65%)

References
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Journal ArticleDOI: 10.1016/J.SOLMAT.2005.04.011
Abstract: Fluorine-doped zinc oxide thin films, ZnO:F, were deposited by the spray pyrolysis technique on sodocalcic glass substrates. Two different zinc precursors were used separately, namely, zinc acetate and zinc pentanedionate. The effect of the zinc precursor type, the aging of the starting solution, the substrate temperature and a vacuum-annealing treatment on the electrical, morphological, structural and optical properties was studied, in order to obtain conductive and transparent ZnO:F thin films. The resistivity values of ZnO:F thin films deposited from aged solutions were lower than those films obtained from fresh solutions. The lowest resistivity values of as-grown films deposited at 500 °C, using a two-day aged starting solution of zinc acetate and zinc pentanedionate, were 1.4×10 −2 and 1.8×10 −2 Ω cm, respectively. After a vacuum annealing treatment performed at 400 °C for 30 min a decrease in the resistivity was obtained, reaching a minimum value of 6.5×10 −3 Ω cm for films deposited from an aged solution of zinc acetate. The films were polycrystalline, with a (0 0 2) preferential growth orientation in all the cases. Micrographs obtained by SEM show a uniform surface covers by rounded grains. No evident change in the surface morphology was observed with the different precursors used. The transmittance of films in the visible region was higher than 80%.

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Topics: Zinc (62%), Thin film (51%)

2,777 Citations


Open accessBook
13 Jan 2009-
Abstract: The revision of this text hallmark text on Solar Energy has been done keeping in mind the current scenario in Solar Energy requirements. As a result the book is updated with the energy scenario and the various applications of solar energy being used today. Numerous new topics comparison tables solved and unsolved problems, have been added and changes have been made to cater to the changing requirements of the students. In all it is the most updated and comprehensive yet concise book on the subject.

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Topics: Solar energy (62%)

563 Citations


Journal ArticleDOI: 10.1016/S0038-092X(98)00008-5
Andreas Gombert1, W. Glaubitt1, Klaus Rose1, J. Dreibholz1  +8 moreInstitutions (1)
01 Mar 1998-Solar Energy
Abstract: Different attempts have been made to produce anti-reflection (AR) layers for solar applications. The most promising solutions are based on the principle of mixing bulk material with air on a subwavelength scale in order to obtain the very low effective refractive indices suitable as AR coatings for glazing. Possibilities for achieving this are given by porous media and subwavelength surface-relief gratings. Subwavelength grating structures, which were embossed in organically modified sol-gel materials or acrylic materials, and porous sol-gel coatings were investigated and compared theoretically and experimentally by the Fraunhofer Institutes. It is shown, theoretically and experimentally, that an increase of solar transmittance of ≈3% per glass surface can be achieved with a porous sol-gel coating.

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Topics: Glazing (57%), Transmittance (54%), Porous medium (51%) ...read more

68 Citations


Journal ArticleDOI: 10.1016/J.SOLENER.2005.06.002
Maatouk Khoukhi1, Shigenao Maruyama1Institutions (1)
01 Jul 2006-Solar Energy
Abstract: A rigorous theoretical approach of a flat-plate solar collector with a black absorber considering the glass cover as an absorbing–emitting media is presented. The glass material is analyzed as a non-gray plane-parallel medium subjected to solar and thermal irradiations in one-dimensional case using the Radiation Element Method by Ray Emission Model (REM 2 ). The optical constants of a clear glass window proposed by Rubin have been used. These optical constants, 160 values of real part n and imaginary part k of the complex refractive index of a clear glass, cover the range of interest for calculating the solar and thermal radiative transfer through the glass cover. The computational time for predicting the thermal behavior of solar collector was found to be prohibitively long for the non-gray calculation using 160 values of n and k . Therefore a suitable semi-gray model is proposed for rapid calculation. The profile of the efficiency curve obtained in the present study was found to be not linear in shape. Indeed, the heat loss from the collector is a combination of convection and radiation and highly non linear. The effect of the outside convective heat transfer on the efficiency curve is also studied. In fact, when the convection is the dominant heat transfer mode compared with the radiation one, the profile of the efficiency curve is more or less straight line. Consequently, the heat loss coefficient could be calculated using Klein model. It has been also shown that the effect of the wind speed on the glass cover mean temperature is very important. This effect increases with the increase of the mean absorber temperature.

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Topics: Heat transfer (59%), Convective heat transfer (59%), Thermal (55%) ...read more

47 Citations


Naiem Akhtar1, S. C. Mullick2Institutions (2)
Abstract: Absorption of solar radiation in the glass cover(s) of a flat plate solar collector increases the temperature of cover(s) and hence changes the values of convective and radiative heat transfer coefficients. The governing equations for the case of single as well as double glazed collector have been solved for inner and outer surface temperatures of glass cover(s) with/without including the effect of absorption of solar radiation in the glass cover(s), with appropriate boundary conditions. The effects of absorption of solar radiation on inner and outer surface temperatures and consequently on convective and radiative heat transfer coefficients have been studied over a wide range of the independent variables. The values of glass cover temperatures obtained from numerical solutions of heat balance equations with and without including the effect of absorption of solar radiation in the glass cover(s) are compared. For a single glazed collector the increase in glass cover temperature due to absorption of solar radiation could be as high as 6°. The increase in temperatures of first and second glass covers of a double glazed collector could be as high as 14° and 11°, respectively. The effect on the convective heat transfer coefficient between the absorber plate and the first glass cover is substantial. The difference in the values of the convective heat transfer coefficients between the absorber plate and the first glass cover (hcp1) of a double glazed collector for the two cases: (i) including the effect of absorption and (ii) neglecting the effect of absorption in glass cover, could be as high as 49%. Correlations for computing the temperatures of inner and outer surfaces of the glass cover(s) of single and double glazed flat plate collectors are developed. The relations developed enable incorporation of the effect of absorption of solar radiation in glass cover(s) in the relations for inner and outer surface temperatures in a simple manner. By making use of the relations developed for inner and outer surface temperatures of glass cover(s) the convective and radiative heat transfer coefficients can be calculated so close to those obtained by making use of surface temperatures of glass cover(s) obtained by numerical solutions of heat balance equations that numerical solutions of heat balance equations are not required.

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Topics: Convective heat transfer (59%), Heat transfer coefficient (55%), Convection (53%) ...read more

45 Citations


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