Study on Selection of a Suitable Material and The Parameters for Designing a Portable Flat Plate Base-Thermal Cell Absorber (FPBTCA)

Several types of flat plate solar collectors have been designed and developed with various technical parameters involved in the design. The inappropriate flat plate solar collector parameter design and material chosen will affect its performance. Investigation on the effect of flat plate absorber collector material, glass thickness, air gap distance, thermal cell absorber thickness, and flat plate absorber base collector thickness on the performance of solar thermal collectors was conducted in this work. The experiment was performed using the solar simulator with solar radiation of 450 and 750 W/m2. The flat plate absorber collector materials used in this experiment were stainless steel 304 and aluminum. The glass thickness used in this experiment was 2.0, 3.0, 4.0, 5.0, and 10.0 mm. The air gap between the flat plate absorber and glass used in this experiment was 0, 5.0, 10.0, 20.0, and 30.0 mm. The stainless steel thermal cell absorber thickness applied in this experiment was 0.5, 1.0, and 2.0 mm. Meanwhile, the aluminum flat plate base absorber base collector thickness was 0.5, 0.8, and 1.0 mm. The results showed that the 2.0 mm glass thickness has the maximum flat plate absorber temperature (88.1 oC at t = 600 s), high heat gain rate (0.097 oC/s), and the highest total heat gain (1207.33 J). The results also revealed that the air gap distance of 10 mm achieved the maximum flat plate absorber temperature (64.6 oC at t = 600 s), the highest heat gain rate (0.058 oC/s), and the highest total heat gain (4750.92 J). The stainless steel thermal cell absorber thickness of 1.0 mm has the thermal cell absorber temperature of 76.2 oC at t = 600 s and a high heat gain rate at 0.08 oC/s. The aluminum flat plate base absorber achieved the highest flat plate absorber temperature (67.2 oC at t = 600 s) and the highest heat gain rate (0.062 oC/s). By using double glass as glass cover increase the flat plate absorber temperature (76.3 oC at t = 600 s) and the highest heat gain rate (0.077 oC/s). This research aims to produce a flat plate absorber with better energy storage, i.e., the performance of the stainless steel plate absorber is better than aluminum with the same thickness. Although the stainless steel flat plate absorber collector showed a lower temperature than aluminum, it has a higher temperature drop than the latter.

Performance Evaluation of a Hybrid Solar Collector in Two Different Climates

The solar hybrid collector (PV/T) modules are a beneficial approach that simultaneously transforms solar radiation into heat and electric power. This work examined the performance of a PV/T module with flat-plate absorber type and water-cooled by optimizing the PV/T model under two significantly different climate conditions. The first is for Stuttgart city, and the second is for Kabul. According to what has been conducted in this study, Kabul has a higher percentage of the received heat energy than Stuttgart, at more than 50.4%. Furthermore, Kabul's electrical efficiency is 48.3% higher than Stuttgart's. As a matter of fact, the annual radiation of Kabul is more than Stuttgart city by 49.12%. Thus, Kabul city seems to be more convenient than Stuttgart for the PV/T applications.

Performance Assessment of an NH3/LiNO3 Bubble Plate Absorber Applying a Semi-Empirical Model and Artificial Neural Networks

In this study, ammonia vapor absorption with NH3/LiNO3 was assessed using correlations derived from a semi-empirical model, and artificial neural networks (ANNs). The absorption process was studied in an H-type corrugated plate absorber working in bubble mode under the conditions of an absorption chiller machine driven by low-temperature heat sources. The semi-empirical model is based on discretized heat and mass balances, and heat and mass transfer correlations, proposed and developed from experimental data. The ANN model consists of five trained artificial neurons, six inputs (inlet flows and temperatures, solution pressure, and concentration), and three outputs (absorption mass flux, and solution heat and mass transfer coefficients). The semi-empirical model allows estimation of temperatures and concentration along the absorber, in addition to overall heat and mass transfer. Furthermore, the ANN design estimates overall heat and mass transfer without the need for internal details of the absorption phenomenon and thermophysical properties. Results show that the semi-empirical model predicts the absorption mass flux and heat flow with maximum errors of 15.8% and 12.5%, respectively. Maximum errors of the ANN model are 10.8% and 11.3% for the mass flux and thermal load, respectively.

Performance and Design Optimization of Two-Mirror Composite Concentrating PV Systems

The reflectors of a linear solar concentrator investigated in this work consisted of two plane mirrors (2MCC), and they were designed in such a way that made all radiation within the acceptance angle (θa) arrive on flat-plate absorber, after less than two reflections. To investigate the performance of an east–west aligned 2MCC-based photovoltaic (PV) system (2MCPV), a mathematical procedure was suggested based on the three-dimensional radiation transfer and was validated by the ray-tracing analysis. Analysis indicated that the performance of 2MCPV was dependent on the geometry of 2MCC, the reflectivity of mirrors (ρ), and solar resources in a site, thus, given θa, an optimal geometry of 2MCC for maximizing the annual collectible radiation (ACR) and annual electricity generation (AEG) of 2MCPV in a site could be respectively found through iterative calculations. Calculation results showed that when the ρ was high, the optimal design of 2MCC for maximizing its geometric concentration (Cg) could be utilized for maximizing the ACR and AEG of 2MCPV. As compared to similar compound parabolic concentrator (CPC)-based PV systems, the 2MCPV with the tilt-angle of the aperture yearly fixed (1T-2MCPV), annually generated more electricity when the ρ was high; and the one with the tilt-angle adjusted yearly four times at three tilts (3T-2MCPV), performed better when θa < 25° and ρ > 0.7, even in sites with poor solar resources.

Intensification of a flat solar collector efficiency

An experimental study was carried out to investigate the intensification of the efficiency of a flat solar collector. To achieve this aim, we investigated the effect of the thickness of the air gap between the glazing cover and the plate absorber and the effect of presence of transparent partitions in the air gap. Indeed, when the thickness of the air gap is increased, the natural convection is intensified, which induces high thermal losses on the front part of the collector. The result of this study highlights that thicknesses larger than the reference one, given by the manufacturer, decrease the efficiency, while thicknesses smaller than the reference one increase the efficiency. The presence of transparent partitions in the air gap leads to the weakening of the natural convection and thus to the enhancement of the solar collector efficiency. Two situations were studied. In the first one, only transverse partitions were placed in the air gap; in the second one, longitudinal partitions were added to the transverse ones to form a crossed structure of partitions. The obtained results showed that in both situations the enhancement of the efficiency is significant and that the crossed structure induces the better efficiency.