Hybrid Renewable Energy Systems are pivotal for the sustainable energy transition, yet their design and operation present complex optimization challenges due to diverse components, stochastic resources, and multifaceted objectives. This systematic review formalizes the HRES optimization problem space and identifies critical research gaps. Employing the PRISMA 2020 guidelines, it comprehensively analyzes the literature (2015–2025) from Scopus, IEEE Xplore, and Web of Science, focusing on architectures, mathematical formulations, objectives, and solution methodologies. The results reveal a decisive shift from single-objective to multi-objective optimization (MOO), increasingly incorporating environmental and emerging social criteria alongside traditional economic and technical goals. Metaheuristic algorithms (e.g., NSGA-II, MOPSO) and AI techniques dominate solution strategies, though challenges persist in scalability, uncertainty management, and real-time control. The integration of hydrogen storage, vehicle-to-grid (V2G) technology, and multi-vector energy systems expands system boundaries. Key gaps include the lack of holistic frameworks co-optimizing techno-economic, environmental, social, and resilience objectives; disconnect between long-term planning and short-term operation; computational limitations for large-scale or real-time applications; explainability of AI-based controllers; high-fidelity degradation modeling for emerging technologies; and bridging the “valley of death” between simulation and bankable deployment. Future research must prioritize interdisciplinary collaboration, standardized social/resilience metrics, scalable and trustworthy AI, and validation frameworks to unlock HRESs’ potential.

This article conducts a comprehensive PEST (Political, Economic, Social, Technological) and SNW (Strengths, Neutrals, Weaknesses) analysis on adopting liquid hydrogen as a motor fuel in the aviation industry. The urgency for sustainable aviation fuels is accentuated by the escalating environmental concerns and the aviation sector's significant carbon footprint. Liquid hydrogen, recognized for its high energy density and zero carbon emissions at the point of use, emerges as a promising alternative to conventional aviation fuels. Through a PEST analysis, the article examines the multifaceted external factors influencing the feasibility of liquid hydrogen in aviation, including supportive policies, economic considerations, societal attitudes towards green aviation, and the technological challenges and advancements in hydrogen fuel technologies. The SNW analysis delves into the intrinsic aspects of liquid hydrogen's application in aviation, highlighting its strengths such as environmental benefits and renewable production potential, its neutral factors that may neither significantly impede nor accelerate its adoption, and its weaknesses including storage and transportation challenges. The article concludes with strategic recommendations to mitigate the identified deficiencies, leverage strengths, and transform neutrals into opportunities for the widespread adoption of liquid hydrogen in aviation. This study aims to provide stakeholders in the aviation sector with insightful analyses to navigate the complexities of introducing liquid hydrogen as a sustainable aviation fuel, contributing to the broader goal of achieving carbon-neutral aviation. Keywords: transport, aviation, liquid hydrogen, motor fuel, sustainable aviation fuels, energy efficiency, electrical equipment.

The development of "green" energy in Ukraine involves an increasingof the amount of electricity generated by photovoltaic modules (PMs). However, PMs have disadvantages associated with the inconsistency of electric generation in time due to the diurnal and annual motion of the Sun and to the shading of the modules. In order to maintain steady generation during the day and the year, there are two ways to minimize the impact of these factors.First one is to install an excess capacity which means higher cost of the solar plant and using an additional area.Second one isto apply a system of orientation PMs perpendicular to the sun's rays. In the article three cases of solar panels installation are considered: usinga two-axistracking system, using aheight tracking system and anazimuth tracking system. There wasgiven the method and algorithms of calculation and analysis the parameters of theuniaxialand biaxial tracking system when installed in Kyiv.The algorithm involves calculation the coordinates of Sun in any moment of time for the considered location, pass-through and absorptive capacityof the protective glass, estimation the amount of the direct and diffuse solar radiation and their impact on the total radiation on the surface of the photoconverter. There was made an estimation of energy usage efficiency levels for the considered systemsusing the proposed algorithm.

У статті наведено та проаналізовано чинне законодавство в частині регулювання якості електроенергії. Акцентовано на дотриманні стандартів. Серед основних вимог – допустимі відхилення напруги, обмеження гармонічних спотворень, контроль флікера та складових зворотної послідовності. Пристрої регулювання напруги мають підтримувати її рівень у межах 100–105 % номінального значення залежно від навантаження. Було охарактеризовано особливості сонячної та вітрової енергетики. Так, сонячні системи (ФЕС) поділяються на мережеві, автономні й гібридні. Генерація залежить від інсоляції, кута падіння променів, ККД панелей та погоди. Типовий профіль виробництва має піки вдень, що не збігається з вечірніми максимумами споживання. Вітрові установки класифікуються за типом осі ротора (HAWT, VAWT). Потужність вітрогенераторів визначають за формулою, що враховує швидкість вітру, густину повітря та коефіцієнт потужності Cₚ (0,2–0,5 для HAWT). Генерація відрізняється високою мінливістю, особливо в умовах нестабільних вітрів. Крім того, було запропоновано технології підвищення надійності, зокрема накопичувачі енергії, та проаналізовано способи прогнозування генерації. Інтеграція ВДЕ вимагає адаптації інфраструктури до їхньої мінливості.