Johnson Matthey Technology Review - Volume 69, Issue 4, 2025

In power grid modernisation, optimal network use is essential to preserving acceptable voltage profiles, boosting voltage stability, reducing power losses, and strengthening system security and dependability. This can be accomplished by strategically placing reactive power compensation devices within transmission and distribution networks, such as capacitor banks, synchronous condensers, flexible alternating current transmission system (FACTS) devices and custom power devices. The optimal location and size of these devices are essential for effective investment, but previous research has mostly concentrated on a variety of methods for this goal, using different indices to evaluate power loss, voltage stability, voltage profile and line loadability. Despite these initiatives, there is still a lack of a thorough analysis of how current indices and methodologies are applied to all varieties of reactive power compensation devices. This paper offers a detailed literature review on the ideal placement and sizing of these devices, encompassing analytical, conventional and hybrid-based techniques. It discusses key objectives such as power loss reduction, voltage deviation (VD) mitigation, voltage stability enhancement and improvements in system reliability and security. Additionally, the paper examines the relevance of reactive power for stakeholders, including transmission system operators (TSOs), distribution system operators (DSOs) and power generating companies, and explores the mathematical modelling of optimal reactive power dispatch (ORPD), considering the impact of renewable energy sources (RESs) and the role of FACTS devices.

The inherent variability and the sporadic and unpredictable nature of solar irradiance limit the efficiency of photovoltaic (PV) arrays in consistently achieving maximum power output. This paper addresses the technical challenge of enhancing power extraction efficiency from PV systems by implementing and conducting a comparative study of various maximum power point tracking (MPPT) algorithms. The various algorithms which are considered for analysis purpose are perturb and observe algorithm (P&O), incremental conductance algorithm (INC) and fuzzy logic-based algorithm (FLC). The objective is to identify the most effective algorithm to maintain PV array operation near its maximum power point (MPP) under dynamic environmental conditions. The methodology involves configuring a direct current (DC) DC-DC converter with precise duty cycle adjustments to optimise energy conversion and transfer. Additionally, the extracted energy is directed to a battery or energy storage unit via a secondary converter. The system is simulated in MATLAB^® to test and compare the performance of different MPPT algorithms. This facilitates the determination of which algorithm most efficiently optimises power extraction from the PV system.

By combining formulae known from the literature that relate thermoelectric parameters, the expression n ≅ 1.13·10¹⁹e^Sr–2/rH(e^Sr–2–0.17) is obtained. That is, the concentration of charge carriers can be determined using the Hall resistance (rH) and reduced Seebeck coefficient. Since these two parameters are calculated using the Seebeck coefficient (S), this coefficient is sufficient to determine the concentration. To demonstrate the use of the obtained new formula, experimental data on silicon-germanium thermoelectric are discussed.

This two-part review delves into the production of sustainable aviation fuels (SAF) derived from biomass and residual wastes through pyrolysis. Part I addresses the challenges associated with the pyrolysis of wastes and provides an overview of both conventional and emerging pyrolysis technologies, the diverse forms of biomass and its significant economic benefits on a global scale. Approximately half of the global population relies on biomass as their primary energy source. Three types of biomass energy are biogas, bio-liquid and bio-solid. In the domains of transportation and energy, it can serve as a substitute for fossil fuels. The primary focus of this study is to examine the data, explore the potential of biomass and analyse the mechanisms of pyrolysis carried out using various processes, technologies (such as pyrolysis speed and temperature) and different types of reactors to produce bio-oil.

Part II of this review examines the current state and forthcoming obstacles of the pyrolysis process in addition to the diverse array of pyrolysis byproducts. Based on this research, it can be inferred that the characteristics of pyrolysis products are influenced by the diversity of materials utilised. Furthermore, pyrolysis products, such as bio-oil, have the potential to make a lucrative contribution to the expanding economy. To overcome future problems, further exploration is ultimately necessary. The primary factors of significance in pyrolysis technology are government subsidies and scientific advancements. The discussion emphasises the significant barriers posed by the energy efficiency and capital costs involved in converting biomass and residual wastes into aviation fuels, hindering widespread adoption. To meet the aviation industry’s greenhouse gas reduction targets by 2050, there is a pressing need for further advancements in technology development, highlighting the critical role of advanced technologies in overcoming these barriers.