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ABSTRACT: In this study, the performances of three modules have been determined. The measured data of the three photovoltaic modules (50W,100W and 17W), such as their open circuit voltage(V oc),short circuit current (I sc), ambient temperature (T amb) , module average temperature(Tm av) and global solar radiation on horizontal surfaces have been investigated for studying of the performance of these solar modules. These measurements have been carried out at the top of the Faculty of Science, Tanta University, of Latitude (1 4 30 ¢ o) and longitude of (30 99) during the period (March 2008– February 2009). The module efficiency (η m), Fill Factor (FF), series resistance (R s) and shunt resistance (R p) for these modules have been calculated. Also, the hourly solar radiation values (I t) on the three modules with tilting angle 30.68 o facing south have been calculated from the measured global solar radiation on horizontal surfaces. Good performance results have been obtained for the position of sun tracking rather than facing south in most cases.
International Journal of Renewable Energy Research. 01/2011; 1:26-40.
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ABSTRACT: In this paper, the double pass-finned plate solar air heater was investigated theoretically and experimentally. An analytical model for the air heater was presented. Numerical calculations had been performed under Tanta (latitude, 30° 47'N and longitude, 31°E) prevailing weather conditions. The theoretical predictions indicated that the agreement with the measured performance is fairly good. Comparisons between the measured outlet temperatures of flowing air, temperature of the absorber plate and output power of the double pass-finned and v-corrugated plate solar air heaters were also presented. The effect of mass flow rates of air on pressure drop, thermal and thermohydraulic efficiencies of the double pass-finned and v-corrugated plate solar air heaters were also investigated. The results showed that the double pass v-corrugated plate solar air heater is 9.3-11.9% more efficient compared to the double pass-finned plate solar air heater. It was also indicated that the peak values of the thermohydraulic efficiencies of the double pass-finned and v-corrugated plate solar air heaters were obtained when the mass flow rates of the flowing air equal 0.0125 and 0.0225 kg/s, respectively.
Applied Energy. 88(5):1727-1739.
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ABSTRACT: In this paper, the thermal performance of a shallow solar-pond (SSP) under the batch mode of heat extraction has been investigated theoretically and experimentally. A transient mathematical model has been proposed. A computer program has been developed based on an analytical solution of the energy-balance equations of different elements of the pond. Numerical calculations have been carried out to study the effects of various configurational and operational parameters on the pond's performance. To improve the pond's performance, an outer mirror is hinged outside the pond to increase the amount of solar radiation incident on the pond cover. Optimization of various dimensions of the pond has been carried out. Effects of the pond's water-depth Xw, wind speed V, the sides' Xs and back Xb insulation thicknesses as well as the height C and width W of the outer mirror have been investigated. The influence of the number of glass covers over the pond during the night have also been studied. Comparisons between experimental and theoretical results showed that good agreement has been achieved. Experiments indicated that the pond could provide 88 l of hot water at a maximum temperature of 60 °C at sunset. The pond can retain hot water till 7.00 a.m. next day at a temperature of 47 °C: this is suitable for domestic applications.
Applied Energy. 78(2):159-177.
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ABSTRACT: A transient analytical model is presented for a flat-plate solar air heater with and without thermal storage. The flowing air temperature is assumed to vary with time and space coordinates. Analytical expressions are obtained for various temperatures of the air heater elements as well as for the temperature of the storage material. The performance of the air heater is investigated by computer simulation using the climatic conditions of Tanta (Lat. 30° 47′ N, Egypt). Effects of design parameters of the air heater such as length (L), width (b), gap spacing between the absorber plate and glass cover (df), mass flow rate (ṁ) and thickness and type of the storage material (sand, granite and water) on the outlet and average temperatures of the flowing air are studied. It is found that as L and b increase the average temperature of flowing air (Tfav) increases up to typical values for these parameters. Typical values for L and b are obtained as 3 and 2 m, respectively. The outlet temperature (Tfo) of flowing air is found to decrease with increasing gap spacing and mass flow rate of air. Improvements in the heater performance with storage have been achieved at the optimum thickness (0.12 m) of the storage material. Therefore, the air heater can be used as a heat source for drying agricultural products and the drying process will continue during night, instead of re-absorption of moisture from the surrounding air. Comparisons between experimental and theoretical results indicated that the proposed mathematical model can be used for estimating the thermal performance of flat-plate solar air heaters with reasonable accuracy.
Renewable Energy.
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ABSTRACT: In an attempt to improve the daily productivity of the single effect solar stills, a single-slope single-basin solar still integrated with a shallow solar pond (SSP) was studied to perform solar distillation at a relatively high temperature. The energy balance equations of various elements of the considered system were formulated and solved analytically. Suitable computer programs were prepared for optimizing and predicting the thermal performance of the considered system. Numerical calculations were carried out on typical summer and winter days in Tanta (latitude 30° 47′N) for different thicknesses and mass flow rates of the flowing water to study the effect of these parameters on the daily productivity and efficiency of the system. To validate the proposed theoretical model, comparisons between calculated and measured results were carried out. Good agreement has been achieved. The year-round performances of the still with and without the SSP were also investigated. The optimum values of the flowing water thickness and the mass flow rate for this typical configuration of the SSP-active solar still were obtained as 0.03 m and 0.0009 kg/s. The annual average values of the daily productivity and efficiency of the still with the SSP were found to be higher than those obtained without the SSP by 52.36% and 43.80%, respectively.
Energy Conversion and Management 49(10):2839-2848. · 2.22 Impact Factor
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ABSTRACT: An indirect type natural convection locally made solar dryer, consisting of a flat-plate solar air heater connected to a drying chamber, has been investigated experimentally and theoretically. The system is used for drying fruits and vegetables such as seedless grapes, figs, green peas, tomatoes and onions. The experimental data are used to calculate the drying constants k for the selected products. The obtained values of k are then correlated with the drying product temperature Tdp. Linear correlations between k and Tdp are found to satisfactorily describe the drying curves of the materials under study. Furthermore, the characteristics constants c and n of Henderson’s equation are determined for the selected crops using the experimentally measured relative humidity of the drying air. A simple mathematical model is presented for the drying chamber based on the energy and mass balance equations and employing the proposed correlations for k as well as the values of the constants c and n. Numerical calculations are performed on typical summer and winter days in Tanta. Comparisons between experimental and theoretical results showed that good agreement has been achieved. The effect of the mass of the drying product mdp on the dryer performance is also investigated by computer simulation.
Energy.
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A.A. El-Sebaii
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ABSTRACT: A transient mathematical model is presented for a triple-basin solar still. It is based on an analytical solution of the energy-balance equations for the various elements of the still. The energy-balance equations are solved analytically using the elimination technique. System performance was investigated by computer simulation. Numerical calculations were performed on typical summer and winter days in Tanta (latitude 30°47′ N) for different water masses in each effect of the still and also for various wind speeds (V) to study the effect of these parameters on the daily productivity of the system. It was observed that the daily total productivity of the still decreases with the increase of water mass in each basin. The total productivity was a maximum for the least water mass in both the lower and middle basins without dry spots over the base of each effect. Moreover, it was found that the daily total productivity of the still increases with the increase of V up to a typical velocity (Vt), beyond which the increase in productivity becomes insignificant. The value of Vt is independent of the water mass in each effect, but it showed some seasonal dependence. On a typical summer day, the daily total productivity of the still was found to be 12.635 kg/m2/d, which agrees well with the results reported in the literature for triple-effect solar stills.
Desalination.
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ABSTRACT: A single basin solar still (SBSS) is designed and constructed. A simple transient mathematical model is presented for the still. It is based on analytical solution of the energy-balance equations for different parts of the still. Analytical expressions for temperatures of different components have been obtained. The thermal performance of the still has been investigatedboth experimentally and theoretically. Good agreement between experimental and theoretical results is observed. The influence of cover slope on the daily productivity of the still was investigated. Effect of heat capacity of basin water on the daylight and overnight productivities was also studied. It is inferred that, the productivity of the still decreases with an increase of heat capacity of basin water during daylight and the reverse is the case overnight. The optimum tilt angles of the still cover were found to be 10 and 50° during the summer and winter seasons, respectively, in Tanta (30° 47′ N). The daily efficiency of the still is about 27%.
Renewable Energy.
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ABSTRACT: In this paper, the thermal performance of a shallow solar-pond (SSP) under the batch mode of heat extraction has been investigated theoretically and experimentally. A transient mathematical model has been proposed. A computer program has been developed based on an analytical solution of the energy-balance equations of different elements of the pond. Numerical calculations have been carried out to study the effects of various configurational and operational parameters on the pond's performance. To improve the pond's performance, an outer mirror is hinged outside the pond to increase the amount of solar radiation incident on the pond cover. Optimization of various dimensions of the pond has been carried out. Effects of the pond's water-depth Xw, wind speed V, the sides’ Xs and back Xb insulation thicknesses as well as the height C and width W of the outer mirror have been investigated. The influence of the number of glass covers over the pond during the night have also been studied. Comparisons between experimental and theoretical results showed that good agreement has been achieved. Experiments indicated that the pond could provide 88 l of hot water at a maximum temperature of 60 °C at sunset. The pond can retain hot water till 7.00 a.m. next day at a temperature of 47 °C: this is suitable for domestic applications.
Applied Energy.
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ABSTRACT: The thermal performance of a double-glass double-pass solar air heater with a packed bed (DPSAHPB) above the heater absorber plate was investigated experimentally and theoretically. Suitable computer program was developed for the analytical solution of the energy-balance equations for the various elements of the system. Limestone and gravel were used as packed bed materials. Numerical calculations were carried out, on typical summer days of 2003, to study the effect of different operational and configurational parameters on the heater performance. Effects of the mass flow rate of air and the mass and porosity of the packed bed material were also studied. It was inferred that for increasing the outlet temperature Tflo of the flowing air after sunset, it is advisable to use the packed bed materials with higher masses and therefore with low porosities. The thermohydraulic efficiency ηTH was found to increase with increasing until a typical value of 0.05 kg/s beyond which the increase in ηTH becomes insignificant. It is recommended to operate the system with packed bed with values of equal 0.05 kg/s or lower to have a lower pressure drop across the system. To validate the proposed mathematical model, comparisons between experimental and theoretical results showed that good agreement was achieved.
Energy.
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ABSTRACT: Solar pond was discovered as a natural phenomena around the turn of the last century in the Medve Lake in Transylvania in Hungary. In this lake, temperatures up to 70 °C were recorded at a depth of 1.32 m at the end of the summer season. The minimal temperature was 26 °C during early spring. The bottom of this lake had a salt NaCl with concentration of 26 percent. Solar pond is artificially constructed. To prevent convection, salt water is used in the pond. Those ponds are called "salt gradient solar pond". Nowadays, mini solar ponds are also being constructed for various thermal applications. It was concluded that the optimum value of salinity in the mini solar pond is 80 g/kg of water.
Renewable and Sustainable Energy Reviews 15(6):3319-3325. · 6.02 Impact Factor
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ABSTRACT: We have designed and constructed a box-type solar cooker with multi-step inner reflectors. The inner reflectors were arranged in a three-step fashion to create different angles with respect to the horizontal. A transient mathematical model is presented for the cooker. It is based on an analytical solution of the energy-balance equations for different components of the cooker. The cooker was tested in the laboratory with a solar simulator under different solar insolation. To validate the present model, numerical calculations have been carried out using the same conditions of indoor tests. The transient performance of the cooker was studied by computer simulation for typical summer (15 July) and winter (15 December) days in Tanta, latitude 30 ° 47′N, Egypt. Good agreement between experimental and theoretical results is observed. It is evident that the cooker is able to boil 1 kg of water in 24 min when its aperture area equals 1 m2. The cooker can be used three times a day in summer and twice a day in winter for cooking consecutively with an overall utilization efficiency of about 30%.
Energy.
