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The cost of manufacturing and electricity consumption are key considerations in encouraging the adoption of solar air heaters (SAH) in sunny and low‐income areas. These parameters can have a significant impact on promoting the use of these devices. In this study, solar air heating was designed with the objective of achieving the highest possible efficiency/cost ratio. It is a corrugated channel SAH whose structure is equipped with two barriers perforated with a sufficient number of holes for a good airflow distribution. A new model was developed to evaluate the qualitative parameters that describe the thermos‐energetic behavior of a heating system. These parameters were measured using experimental data obtained under real operating conditions. The thermal model assumes a uniform temperature for the glass, absorber, and insulation of the collector, while the temperature of the circulating air is assumed to vary linearly along the collector. To ensure that these assumptions were valid, the collector was cut into a number of 0.1 m sections in the direction of flow. By comparing the numerical results with the experimental data, the model was validated and then used to calculate the temperature profiles of the different elements of the collector, as well as to estimate the impact of certain operational parameters on its thermal performance. Relative percentage error values, between the numerical and the experimental results, of 1.7517%, 1.0750%, 0.8577%, 2.2371%, and 2.3637% for absorber plate temperature, outlet airflow temperature, useful power, thermal, and effective efficiencies, respectively, are recorded. [ABSTRACT FROM AUTHOR]

This paper presents the design of highly efficient rectifiers that can operate at WiFi frequencies (2.45 GHz and 5.8 GHz) and match low input power. The designed dual-band rectifiers use multi-stage dickson voltage multipliers (DVM) (from 1 to 6 stages), and the main idea of this paper is to find the number of stages that offers the best performance and that can be used by applications that operate within the same constraints (operating frequencies, input power). The efficiency and the output voltage (Vout) are the parameters studied to analyze the designed rectifiers. The results showed that as the number of DVM stages increased, the efficiency curves for both frequencies shifted to the higher input power range, even when using the same diode (SMS7630) and the same load (5 KO). We concluded that the rectifier with 1-stage DVM is the most suitable to be used for low input power at the selected frequencies since it provides an efficiency of 57.734% at 0 dBm for 2.45 GHz and 36.225% at 1 dBm of input power for 5.8 GHz. [ABSTRACT FROM AUTHOR]

In this manuscript, we have theoretically reanalyzed data prepared and already published by Foroughi et al. (RSC Adv 2016;6:46427–32). These data concern the thermal energy dependence of the electrical conductivity of the samples: graphene fiber, graphene/poly(3,4-ethylenedioxythiophene) (graphene/PEDOT), graphene/carbon nanotube (graphene/CNT) and graphene/carbon nonotube/poly(3,4-ethylenedioxythiophene) (graphene/CNT/PEDOT) composite fibers. We investigate the behavior of the thermal conductivity for these four samples. These samples are considered as thermoelectric materials or green energy conversion materials using the Seebeck effect to transform heat into electrical energy and vice versa. In this context, the optimization of the merit factor ZT remains a challenge for the scientific community. The objective of this investigation is to evaluate and characterize the thermoelectric efficiency of the above-mentioned samples. We confront the experimental data with the existing theoretical models. The thermoelectric efficiency is generally characterized by the merit factor ZT. The maximum ZT of about 1,2 is obtained in the graphene fiber and between 0,1 and 0,2 in the others samples. The performance of the material depends on ZT; indeed a high ZT (⁠|$\mathrm{ZT}\ge 1$|⁠) corresponds to a better optimization of the composite. [ABSTRACT FROM AUTHOR]