The present paper focuses on the high-pressure metal-organic vapor phase epitaxy (MOVPE) upside-down vertical reactor (where the inlet of cold gases is below a hot susceptor). This study aims to investigate thermo-kinetic phenomena taking place during the GaN (gallium nitride) growth process using trimethylgallium and ammonia at a pressure of above 2 bar. High pressure accelerates the growth process, but it results in poor thickness and quality in the obtained layers; hence, understanding the factors influencing non-uniformity is crucial. The present investigations have been conducted with the aid of ANSYS Fluent finite volume method commercial software. The obtained results confirm the possibility of increasing the growth rate by more than six times through increasing the pressure from 0.5 bar to 2.5 bar. The analysis shows which zones vortexes form in. Special attention should be paid to the transitional flow within the growth zone as well as the viewport. Furthermore, the normal reactor design cannot be used under the considered conditions, even for the lower pressure value of 0.5 bar, due to high turbulences.

This paper examined the impact of optical fiber sensor design, and its integration to PVC (polyvinyl chloride) sheet piles, on deflection and strain monitoring. Optical fiber sensors based on Brillouin light backscattering (BLS) were prepared, as they can provide accurate strain and deflection measurement results. However, depending on the application of sheet piles systems, high deformation of PVC elements can be observed. Therefore, a fiber sensor design is not trivial. Three types of optical fiber coatings and their integration with PVC sheet piles were investigated. The effect on the value of compressive and tensile strain were analyzed. It has been experimentally proven that PVC sheet piles monitoring, based on BLS method, can be realized using optical fibers with 250 µm, 900 µm, and 3 mm coating diameter. Achieved results are in line with theory. Correction coefficient necessary for 900 µm and 3 mm coatings has been proposed and used to ensure proper strain measurement. It was found that 250 µm coating fiber based sensors can be utilized for PVC strain measurement under low deflection (>1.2 m beam length). On the other hand, sensors based on 3 mm coating fiber, due to a high level of linearity, can be applied to deflection distance measurement under high deformation.

The present study introduces a novel design for lensed, chemically etched optical fibers (LEOFs) designed for efficient coupling with multicore fibers (MCFs). Experimental characterization at a wavelength of 1550 nm yielded an average coupling loss of approximately 0.76 dB under direct physical contact and 0.40 dB when the fiber end was positioned at an optimal working distance. Moreover, it was experimentally demonstrated that LEOFs exhibit high tolerance to longitudinal displacement and minimal wavelength-dependent variation in coupling efficiency. Based on this approach, fiber-in–fiber-out (FIFO) multicore couplers were fabricated using bundles of LEOFs that had been aligned to MCF cores. Bidirectional measurements yielded average insertion losses of 3.23–3.30 dB in TX and 3.20–3.27 dB in RX transmission directions at 1550 nm, with core-resolved losses as low as 1.09 dB for well-aligned channels. The results confirm the viability of LEOF-based multicore free-space coupling, with further improvements expected from enhanced fabrication accuracy.

Numerical analysis of the trimethylgallium (TMGa) decomposition during epitaxy growth process was analysed. The main aim is to compare previously published trimethylgallium decomposition models. Hence, thermo-fluidic and species transport simulations of the MOVPE (metal-organic vapour phase epitaxy) reactor were performed. Study is focused on a simplified, but most crucial mechanism of epitaxy growth: chemical model of a TMGa decomposition. Analysis of species densities and pyrolysis speed for different approaches were beneficial to understand emerging phenomena during epitaxy growth and to choose most applicable method for future consideration. Analysis have been conducted with the aid of Ansys Fluent software. Numerical simulations depict extreme results, indicating that selecting correct model as a base for the growth process modelling is crucial.

PV/T modules, or hybrid solar modules, allow generating electricity and heat in one component. An important aspect of designing such modules is the cooling efficiency of the structure. Using CFD simulations, the application of micro- and minichannel liquid coolers in the collector part of the modules were compared. Results indicate advantage of the minichannel solutions within the context of cooling efficiency in hybrid solar modules.

Hybrid photovoltaic thermal (PVT) modules have gained more attention because of their benefits of higher total efficiency and lower gross area of installation in comparison with photovoltaic (PV) or solar thermal collectors (T). Although international standards for separate panels, photovoltaics, or thermal collectors are available, the lack of testing procedures for PVT panels is a problem, especially if a high level of integration between the two parts is implemented. In the paper, a new stand to test new PVT minimodules is proposed and verified. It allows a reduction of the influence of environmental conditions on the tested T or PVT structures. Research conducted on lamp configurations confirms the possibility of achieving a high uniformity of light intensity, with values close to the AM1.5 spectrum standard (1049 ± 34 W/m²). The first measurements of new PVT minimodules have proven their usefulness, as well as the potential of a new hybrid solution.