TiO₂ nanotube layers (TNT) are prepared by electrochemical anodization of Ti foil in an electrolyte composed of ethylene glycol, ammonium fluoride and water. The surface of TNT is modified by iron using spin-coating of Fe(NO₃)₃/IPA (isopropyl alcohol) solution of different concentrations. The as-prepared materials are annealed at 450 °C for 2 h to form crystalline Fe-TNT. The phase identification and surface morphology of the materials are investigated by XRD and SEM, respectively, while the energy bandgap (E_g) is analysed by DRS. The novelty of this work is based on the investigation of different photochemical processes that could occur simultaneously, and it includes photocatalysis but also Fenton-based processes since iron is a Fenton-active element. To this end, the degradation of organic pollutants (e.g., caffeine) is performed under solar-like radiation at pH = 3 using different systems that are Fe-TNT material, radical precursors (H₂O₂), and Fe-TNT combined with H₂O₂. It is worth noting the degradation mechanism of the organic pollutants is an advanced oxidation process where hydroxyl radicals have been identified by UV-visible fluorescence spectroscopy (using coumarin as probe molecule) as the main reactive oxygen species. One of the main goals of this work is to determine the contribution of the different involved photochemical processes (photocatalysis, photo-Fenton and photolysis) along with the potential synergy between all these processes. To resume, this work provides new insights into the concept of photochemical versatility, which is scarcely described in the literature.

Tracers are specific materials and compounds that are widely used in the modern oil and gas industry for monitoring well drilling and construction operations, oil production, reservoir characterization, and gas storage procedures.

In the downhole oil and gas applications, tracers are utilized as a surveillance tool to obtain information about the connectivity of the reservoirs, determination of fluids flow pathways, estimation of residual oil saturation of the formation, and efficiency of reservoir intervention along with such methods as monitoring of oil production rate, 4D seismic, well logging and others. The important information that can be obtained through the tracer’s tests is well-to-well connectivity, residual oil saturation, maps of the fluids’ flow paths, and others.

Current industrially used tracers are isotopes (stable and radioactive), dyes, organic chemicals, polymers, nanoparticles, gases, ions, and salts. Tracers are injected into the reservoir with injection fluids, follow the fluid paths, and are detected and quantified at the production or wellhead zone via various analytical methods such as scintillation counting, ion chromatography, GCMS, LCMS, FTIR and spectrofluorometry, and other. Cost-efficient tracers with fast and simple detection and quantification method at low detection limit via on-site detection is a current industrial target for state-of-the-art tracers’ tests.

To bridge the gap between the desired tracers’ properties and detection limits, we developed a broad spectrum of robust cost-efficient fluorophores to innovate the current reservoir management practices. These developed fluorescent tracers not only have low detection limit of fluorescent spectroscopy techniques but also allow for the automated detection at concentrations up to ppt level. Thus, our developed tracers open the horizon to detect in real-time the drilling depth to enhance the hydrocarbon recovery. To conclude, our innovative fluorescent tracing approach would 1) reduce the drilling depth correlation uncertainty, 2) optimize well placement, and 3) maximize oil production.

Photovoltaic (PV) systems are utilized all over the world for clean energy production. Photovoltaic simulation software is used to predict the energy produced by photovoltaic array structures. Due to Pakistan's geographical location in the equatorial region, the prospect of harnessing photovoltaic energy is too high. In the context of this fact, this work conducted extensive research to optimize photovoltaic energy output by using different PV modules sizes. For fixed areas where photovoltaic modules are installed, the output energy would remain more or less the same for any size of PV modules with insignificant differences in PV modules efficiency or quality. Moreover, in this research, it is found that by using different PV module sizes (i.e. 250 watt to 540 watt) at a time, while keeping all other parameters and conditions constant, a large variation in the output energy of the system can be observed. This difference in output energy with the change of PV modules sizes raises fundamental concerns about how to choose the right PV modules size to generate maximum output energy at any given location. This study intends to emphasize the fact that when designing an On-Grid photovoltaic system, relatively little consideration is given to selecting the appropriate type and size of PV modules, which can result in significant energy loss of the system. In this research, different PV modules of various sizes and power ratings with nearly identical efficiencies were analyzed in four selected locations. HelioScope simulation software is used to simulate all PV systems having PV modules power rating to analyze their monthly, annual energy generation, and system losses. The simulation results show that the appropriate PV modules size must be determined in order to generate the maximum output energy from the proposed PV system.

Introduction. In recent years, the search for alternative renewable energy sources has been actively carried out. Considerable attention of scientists is attracted by energy generation methods based on the mixing of electrolyte solutions of different concentrations ‒ Blue Battery systems. Among these methods, a promising system is reverse electrodialysis, the principle of which is the generation of electrical potential over a stack of ion-selective membranes when a concentrated and diluted electrolyte is passed at different sides of the membranes in the RED stack. The development and testing of membranes are among the main trends for RED optimization. Due to the outstanding transport properties, it was suggested that grafted membranes could be potentially effective in the RED process. In this study, synthesized grafted cation and anion exchange membranes based on functionalized polystyrene grafted onto UV-oxidized polymethylpentene films was tested in lab-scale reverse electrodialysis stacks.

Results and Discussion. The synthesized grafted membranes provided the highest power density of lab-scale stacks with a total active membrane area of 72 cm² with the use of 0.1 Ðœ/1 Ðœ NaCl (0.67 W/m²) and 0.1 Ðœ/5 Ðœ NaCl (2.1 W/m²) solutions. The use of grafted membranes with a low resistance ~0.5 Ω cm² (0.5 Ðœ NaCl, 25 °C) did not benefit the stack resistance; the low selectivity of such membranes resulted in a lower open-circuit voltage of stacks and high non-selective diffusion losses. Higher power densities and current efficiencies in model systems were observed for grafted membranes with moderate conductivity and high permselectivity.

A strong correlation between the calculated and experimental stack resistances was found for the 0.1 M/1 М NaCl electrolyte system. In the case of a 0.1 M/5 М NaCl stack, this correlation is markedly poorer, which may be attributable, first, to a considerable change in the concentration of dilute electrolyte in the dilute feed channel caused by the high diffusive flux of the electrolyte and the high osmotic flux of water and, second, to the effect of concentration polarization. The correlations between the measured membrane potential and the open circuit voltage for the stacks in both electrolyte systems are very strong. The results of the study were published in the following article [1].

Acknowledgments. This study was funded by Russian Science Foundation (project no. 21-73-20229).

1. Golubenko D.V., Van der Bruggen B., Yaroslavtsev A.B. Ion exchange membranes based on radiation-induced grafted functionalized polystyrene for high-performance reverse electrodialysis // J. Power Sources. Elsevier B.V., 2021. Vol. 511, â„– March. P. 230460.

Composite nanofilms based on biopolymers (PLA, PVA etc.) and ZnO are alternative materials for “green” food packaging. The combination of the useful features of the both biopolymer (compostability and biodegradability) and good barrier, antioxidant and antibacterial properties of Zn-containing materials (hydrozincite, HZ) make these materials attractive for different applications [1].

The biocomposite films of PLA and PLA/PVP containing 5wt% hydrozincite powders have been obtained by sol-gel method. The Mentha Arvensis – mediated hydrothermal synthesis was applied to obtain the HZ powders [2].

The photocatalytic activity and antibacterial efficacy against Escherichia coli (food pathogen) of the synthesized nanofilms were investigated. The X-ray diffraction analysis and Fourier-transform infrared spectroscopy were used to determine the phase composition and functional groups.

The comparative photocatalytic investigations about degradation of two model dyes – Malachite Green (MG) and Reactive Black 5 (RB5) in aqueous solution (5 ppm) under UV light were performed. The PLA/Hydrozincite and PLA/Hydrozincite/PVP photocatalysts have higher discoloration degree towards MG dye after 150 minutes UV irradiation (31 and 87 % resp.) than those towards RB5 dye (about 25%). The both nanofilms exhibit high antibacterial effects. The bacterial concentration decreased by about 99% and 97% for PLA/Hydrozincite/PVP and PLA/Hydrozincite nanofilms, respectively after 1 hour of contact.

The obtained composites could be used as an alternative of standart food package materials.

References

[1] A. Marra, C. Silvestre, D. Duraccio, S. Cimmino, Polylactic acid/zinc oxide biocomposite films for food packaging application, International Journal of Biological Macromolecules 88 (2016) 254–262.

[2] D. Stoyanova, I. Stambolova, V. Blaskov, P. Georgieva, M. Shipochka, K. Zaharieva, O. Dimitrov, P. Markov, V. Dyakova, Y. Kostova, R. Mladenova, G. Tzvetkov, N. Boshkova, N. Boshkov, Modified approach using Mentha arvensis in the synthesis of ZnO nanoparticles—textural, structural, and photocatalytic properties, Appl. Sci. 12 (2022) 1096.

Kodkin V L, professor at SUSU (Russia)

Is it possible to stably manage complexes of unstable aggregates?

The transition to green energy is widely discussed by economists, journalists and politicians. As often happens, the engineers are almost inaudible. Is it confidence in their omnipotence? Or misunderstanding...

Meanwhile , there are problems . If green energy is based on wind turbines, as the most important and powerful power units, then the problem of sustainability in such an energy system will be extremely acute.

Now it is not there, because wind energy is being added to a very stable nuclear, or carbon, one. But what if these power engineers do not remain?!

Wind turbines themselves are unstable for many reasons - because of the instability of the wind, in the first place. If the parameters of the generated energy do not correspond to the network, the wind turbine is disconnected from the network. And if all installations of the power system behave this way?

All criteria for the stability of complex multidimensional systems begin with the words “All elements of the system must be stable in autonomous modes of operation ...” And if this condition is not present?

Is there a need for a power system at all if the energy sources themselves are distributed? Is it necessary to keep tight network parameters, if almost all consumers still regulate both the frequency and amplitude of the voltage during operation?

The report proposes several provisions that analyze the conditions for the operation of wind power complexes from the point of view of ensuring their sustainability as multidimensional complex dynamic systems and proposes theoretical approaches to solving the problem.

One of the global problems of our time is ecology; environmental pollution caused by the growing number of emissions from the combustion of hydrocarbon fuels, including vehicles with an internal combustion engine, which is growing every year . One of the promising directions in this regard is the transfer of transport to hydrogen-oxygen fuel cells, which effectively convert the chemical energy of hydrogen into electrical energy, releasing only water vapor into the atmosphere. At present, fuel cells with a proton exchange membrane (Proton Exchange Membrane fuel cell, PEMFC) are the most promising for transport [2]. However, their application requires the use of ultrapure hydrogen, since even small amounts of CO (at the level of several ppm) in hydrogen, usually obtained by reforming hydrocarbons, poison the electrocatalysts and reduce the efficiency of the fuel cell. The solution to this problem can be the production of ultrapure hydrogen using hydrogen-selective membranes.

This work is devoted to the study of the transport characteristics of nickel hydrogen-selective membranes (nickel industrial capillaries of various thicknesses). In this work, the hydrogen permeability of nickel capillaries of various thicknesses was measured; studies of the mechanism of hydrogen transport through nickel capillaries were carried out using computer simulation.

In recent years, the use of hydrogen for various applications such as energy storage in microgrids [1], vehicle fuel [2] or other industrial processes has led to the proliferation of PEM electrolyzers based on water electrolysis (PEM WE) as hydrogen generators. On the other hand, a digital twin serves as a replica of the physical device within a virtual environment, whose aim is to mimic the behaviour of the physical device. By means of this digital replica, it is possible to study the behaviour of the PEM WE within the intended system or application in a controlled and safe way, without involving the other components of the system [3]. Typically, the monitoring and control processes of a physical system are supported by graphical user interfaces (GUI) [4]. These graphical tools serve as an interactive bridge between the user and the system, facilitating the monitoring of the system as well as the acquisition and presentation of information resulting from its operation . MATLAB is a programming and computing platform that provides users with a variety of applications and toolboxes with very specific functions. Among them is AppDesigner, an application focused on GUI design and development [5,6]. On the other hand, the Simulink simulation environment allows the design of models and their simulation. This paper describes the design and implementation of a MATLAB/Simulink-based application that embeds a digital replica of a PEM WE and a GUI dedicated to its control, all framed in the operation of a smart microgrid powered by photovoltaic energy and supported by hydrogen generation and storage.

References

1. González, I.; Calderón, A.J.; Andújar, J.M. Novel remote monitoring platform for RES-hydrogen based smart microgrid. Energy Convers. Manag. 2017, 148, 489–505, doi:10.1016/j.enconman.2017.06.031.
2. He, H.; Wang, X.; Chen, J.; Wang, Y.-X. Regenerative Fuel Cell-Battery-Supercapacitor Hybrid Power System Modeling and Improved Rule-Based Energy Management for Vehicle Application. J. Energy Eng. 2020, 146, 04020060, doi:10.1061/(asce)ey.1943-7897.0000708.
3. Zhao, D.; He, Q.; Yu, J.; Guo, M.; Fu, J.; Li, X.; Ni, M. A data-driven digital-twin model and control of high temperature proton exchange membrane electrolyzer cells. Int. J. Hydrogen Energy 2022, doi:10.1016/j.ijhydene.2021.12.233.
4. Mancera, J.J.C.; Manzano, F.S.; Andújar, J.M.; Vivas, F.J.; Calderón, A.J. An optimized balance of plant for a medium-size PEM electrolyzer. Design, control and physical implementation. Electron. 2020, 9, doi:10.3390/electronics9050871.
5. Pérez-Rubio, M.C.; Hernández, Á.; Gualda-Gómez, D.; Murano, S.; Vicente-Ranera, J.; Ciudad-Fernández, F.; Villadangos, J.M.; Nieto, R. Simulation Tool and Online Demonstrator for CDMA-Based Ultrasonic Indoor Localization Systems. Sensors 2022, 22, 1038, doi:10.3390/s22031038.
6. Broden, D.A.; Paridari, K.; Nordstrom, L. Matlab applications to generate synthetic electricity load profiles of office buildings and detached houses. In Proceedings of the 2017 IEEE Innovative Smart Grid Technologies - Asia: Smart Grid for Smart Community, ISGT-Asia 2017; Institute of Electrical and Electronics Engineers Inc., 2018; pp. 1–6.

The accurate estimation of the current state of a bioprocess is important for a proper process control scheme. As a lot of variables of interest require substantial effort and time to measure or sometimes are not measurable at all, a direct measurement is not always an option. Instead an indirect chemometric approach based on some other easier to measure variable such as spectroscopy is commonly used to estimate the state of a bioprocess.

In this contribution we present another much cheaper solution for S. cerevisiae cultivations where the only direct measurement were ethanol measurements in the headspace of the bioreactor based on metal oxide gas sensors. For the current state prediction, a process model and an extended Kalman filter was used. The basic idea is to apply the model to predict the process state, and then use the ethanol measurements to correct and change the model prediction online. The main advantage of this approach is, that metal oxide gas sensors are dead cheap and in contrast to spectroscopic approaches, no expensive calibration is required. The knowledge required is the process model and a rough estimation of the kinetic parameter values.

Robustness and reliability are two of the most factors that identify the superior performance of a controller. Power system stability and control has always been and will continue to be a field that needs continuous attention from researchers due to the increase in the complexity of power systems. This is a consequence of the increase in the capacity and the high penetration of renewable energy resources. This study proposes a new Fuzzy Logic Control (FLC) design for Load Frequency Control (LFC) in power systems. The structure of this design offers a satisfactory level of reliability as well as excellent robustness performance. The proposed fuzzy design is employed as an LFC system in a hybrid dual area power system based on a photovoltaic renewable energy plant in area one and a thermal generation unit in area two. In order for achieving the best possible dynamic performance of the proposed structure, Teaching Learning Based Optimisation (TLBO) algorithm is suggested to optimally tune the scaling factor gains of the proposed fuzzy configuration, the well-known Integral Time Absolute Error (ITAE) objective function is considered for this matter. The superiority of the suggested fuzzy control design is investigated by conducting a comparative study between this design and other controllers based on different theories. Also, the robustness validation of the proposed fuzzy controller is examined against parametric uncertainties of the testbed hybrid power system. Simulation results revealed that the fuzzy Logic Controller introduced in this study is reliable, robust, superior and appropriately handled the problem of frequency variation.