Solution Combustion Synthesis of Transparent Conducting Thin Films for Sustainable Photovoltaic Applications

Biotemplating of Al2O3-Doped, CaO-Based Material from Bamboo Fiber for Efficient Solar Energy Storage

The high-temperature sintering of CaO-based materials leads to the serious decay of energy storage performance during the calcination/carbonation cycle. To overcome the loss in porosity problem, an efficient CaO-based material for thermal energy storage was synthesized using bamboo fiber as the biotemplate. The synthesis parameters (bamboo fiber addition, pyrolysis, Al2O3 loading) and the energy storage reaction characteristics of CaO-based energy storage material were optimized on the basis of cyclic calcination/carbonation experiments. The results show that the sacrificed biotemplate enhances the porosity of the synthetic material, denoting improved energy storage density. The cumulative energy storage density of the templated material over 50 cycles is 24,131.44 kJ/kg higher than that of limestone. The carbonation conversion and energy storage density of the templated CaO-based material doped with 5 wt.% Al2O3 and 0.5 g bamboo fiber reach 0.75 mol/mol and 2368.82 kJ/kg after 10 cycles, respectively, which is 2.7 times as high as that of original limestone. The maximum apparent carbonation rate of the templated CaO-based materials in the 1st cycle corresponds to a 240% increment compared to limestone. The maximum calcination rate of the synthetic CaO-based material in the 12th cycle remains 93%, as compared with the initial cycle. The microstructure analysis reveals that the hierarchically-stable structure during the cycle is beneficial for a more effective exposure of surface reactive sites for CaO and inward/outward diffusion for CO2 molecules through CaO. The method using the sacrificed biological template provides an advanced approach to fabricate porous materials, and the composite CaO-based material provides high-return solar energy storage for a potential application in industrial scale.

Solution Combustion Synthesis of Hafnium-Doped Indium Oxide Thin Films for Transparent Conductors

Indium oxide (In₂O₃)-based transparent conducting oxides (TCOs) have been widely used and studied for a variety of applications, such as optoelectronic devices. However, some of the more promising dopants (zirconium, hafnium, and tantalum) for this oxide have not received much attention, as studies have mainly focused on tin and zinc, and even fewer have been explored by solution processes. This work focuses on developing solution-combustion-processed hafnium (Hf)-doped In₂O₃ thin films and evaluating different annealing parameters on TCO’s properties using a low environmental impact solvent. Optimized TCOs were achieved for 0.5 M% Hf-doped In₂O₃ when produced at 400 °C, showing high transparency in the visible range of the spectrum, a bulk resistivity of 5.73 × 10⁻² Ω.cm, a mobility of 6.65 cm²/V.s, and a carrier concentration of 1.72 × 10¹⁹ cm⁻³. Then, these results were improved by using rapid thermal annealing (RTA) for 10 min at 600 °C, reaching a bulk resistivity of 3.95 × 10 ⁻³ Ω.cm, a mobility of 21 cm²/V.s, and a carrier concentration of 7.98 × 10¹⁹ cm⁻³, in air. The present work brings solution-based TCOs a step closer to low-cost optoelectronic applications.

A Review of Control Techniques in Photovoltaic Systems

Complex control structures are required for the operation of photovoltaic electrical energy systems. In this paper, a general review of the controllers used for photovoltaic systems is presented. This review is based on the most recent papers presented in the literature. The control architectures considered are complex hybrid systems that combine classical and modern techniques, such as artificial intelligence and statistical models. The main contribution of this paper is the synthesis of a generalized control structure and the identification of the latest trends. The main findings are summarized in the development of increasingly robust controllers for operation with improved efficiency, power quality, stability, safety, and economics.