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The escalating demand for renewable energy solutions and the imperative for efficient energy storage mechanisms have catalyzed the evolution of Power-to-X (PtX) technologies. Germany has the most PtX projects, accounting for 44% of all projects that have been reported. PtX encompasses a spectrum of processes engineered to convert surplus renewable energy into versatile energy carriers or chemical commodities, such as hydrogen, methane, or synthetic fuels. The Paramount to this domain is to synergistically harness renewable energy sources and hydrogen carriers to curtail waste and bolster sustainability. Central to achieving this synergy is the effective control of PtX processes, ensuring optimal performance, cost efficiency, and seamless integration within existing energy frameworks. This paper delves into the control processes and environmental prerequisites within the PtX landscape, elucidating key challenges, and strategies within this dynamic realm. While providing an initial overview of fundamental PtX process chains, this paper accentuates the critical role of geographical considerations. Subsequently, it conducts a thorough analysis of equipment modeling challenges, addressing performance metrics, operational requisites, and capital investments, particularly focusing on methanol and hydrogen production and storage. Through holistic examination, this paper endeavors to delineate the evolving landscape of PtX control processes and conditions, advancing our understanding of this expanding field. [Display omitted] • Comprehensive overview of PtX control process, challenges, strategies, and advancements. • Overview of PtX process chains and geographical conditions. • Analysis of equipment modeling challenges for methanol and hydrogen. • Addressing crucial storage challenges in PtX system. • Exploration of diverse influences on PtX control processes. [ABSTRACT FROM AUTHOR]

Renewable hydrogen is considered as one of the key technologies that may be needed to fully decarbonise our economies, providing the high-temperature heat, fuels and feedstock that might not be possible to electrify. Several pilot projects are underway, and some assessments of the economics of green hydrogen have been published. However, most of them have assessed the costs of producing renewable hydrogen in large-scale, grid-connected units. Another option, pointed by many as a robust strategy in the early stages, is to produce hydrogen locally, in "hydrogen valleys", to serve industrial demand. In this paper, the economics of the different technical configurations and strategies that might be used for this decentralised, variable-demand option are analysed, accounting for the impact that a non-constant operation may cause on the operational efficiency of electrolysers, and for the potential benefits of local hydrogen storage. Our results show that when hydrogen demand is variable, production costs are higher compared to the constant demand case, due to the higher electrolyser size required. Electricity price optimization plus hydrogen storage can be a valuable option in some cases, although the cost benefit is negligible (about 1%) unless price volatility in the market increases with higher RES shares, or investment costs decrease significantly. Sourcing electricity exclusively from a dedicated renewable power plant can only become competitive if electricity market prices rise as observed recently or triggered by increasing CO 2 prices. • Different production strategies are compared to minimise H 2 production costs. • Faraday efficiency increases costs for variable electricity generation. • Electricity price optimization is best for H2 valleys, although compression costs may change this. • Direct H 2 production from renewable plants is not competitive with current prices. [ABSTRACT FROM AUTHOR]

Nowadays, renewable energy sources are integral to programs for the development of electric power systems. It is established that modern renewable generation units and energy storage systems utilize power electronic-based interfaces, such as voltage source converters, to convert power. On the one hand, the utilization of a voltage source converter provides certain advantages, such as the absence of a direct link to the network, the ability to operate on all quadrants of the PQ diagram, and the possibility of connecting renewable generation units to a weak network. On the other hand, the widespread use of renewable generation units utilizing voltage source converters reduces the overall inertia of the electric power system. However, excessive use of power electronic converters in the network leads to a significant increase in harmonic pollution, thereby introducing fresh challenges to ensuring safe and stable operation of the electric power system. To ensure the dependable operation of an electric power system with renewable energy sources units and energy storage systems based on the voltage source converter, it is essential to update the control system of the voltage source converter to meet the requirements for traditional generation as part of the electric power system. This paper presents the outcome of the power oscillation damping controller application implemented in the voltage source converter, which enhances the electric power system's stability. [ABSTRACT FROM AUTHOR]

Designing self-sufficient renewable energy systems is becoming a key issue in the energy sector due to modern energy goals. Due to the variability of renewable energy sources, very often it is necessary to adopt hybrid configurations of renewable energy systems and advanced energy storage to achieve self-sufficiency. However, the adoption of complex and novel systems, including technologies as photovoltaic, wind turbines, biomass gasifiers, hydrogen energy storage, must to be founded on a comprehensive analysis of the system operation under different conditions and its energy and economic performance in the investigated case study. Therefore, the aim of the present paper is carry out a comprehensive feasibility analysis of a novel hybrid renewable energy system achieving a high self-sufficiency level. The system integrates a wind turbine and photovoltaic panels to match the energy load of a tourist resort in Agkistro, Greece. Energy exceeding the load is directed to the energy storage system based on the battery and hydrogen tank. As backup energy source, a wood gasifier is used. The investigation is performed by means of a numerical model developed in TRNSYS software allowing one to simulate dynamically the system and to assess its energy and economic performance. The goal achieved during the simulation of the system was to ensure at least 97% of energy demand from renewable sources. Moreover, a parametric analysis of the storage system is presented. It is found that payback period of the installation varies in the range between 11 and 15 years, for systems configurations allowing to satisfy 90–98% of the users energy yearly demand from renewables. The achieved results allows one to evaluate the feasibility of the proposed system from both an energy and economic point of view. • Island energy systems in Greece. • Hybrid energy system with both battery and hydrogen energy storage. • 97% reduction of energy produced from fossil fuels with 30% of energy curtailed. • Parametric study concerning sizes of the energy storage. [ABSTRACT FROM AUTHOR]

Green hydrogen, proposed as a sustainable alternative for conventional fuels, has gained utmost importance due to its reduced carbon footprint and potential application in maintaining balance between energy generation and demand. Utilization of hydrogen-based systems are challenged by cost effective storage methods. Bio-hydrogen storage technologies using cryogenic and adsorptive methods are discussed in this review paper, along with their operating conditions and storage capacities. An analysis of operational challenges and recent advancements in hydrogen storage techniques is presented. With a storage pressure of 70 MP, cryogenic hydrogen is almost twice as dense as compressed hydrogen. Technical challenges such as material cost and explosion risk can be addressed by hydrogen adsorption on activated carbon active sites. Maximum hydrogen storage capacity are reported by activated carbon obtained from Chitosan (6.77 wt%), Bamboo (6.6 wt%) and African palm shell (6.5 wt%) at 77 K and 4–20 Mpa. Further, nanotechnology approaches are presented in detail for increasing hydrogen storage capacity in pristine Si and Mg. The future perspectives in terms of technological, and economic aspects are discussed. • Detailed review on hydrogen storage methods is presented. • Role of cryogenics and adsorptive media are discussed. • The comparative performance of various methods is tabulated. • Existing research gap and future perspectives are analyzed. [ABSTRACT FROM AUTHOR]

Economical hydrogen storage and transportation contribute to hydrogen energy utilization. In this paper, for economically distributing hydrogen from the hydrogen plant to the terminal hydrogen refueling station, considering the daily hydrogen demand and transportation distance, firstly a comprehensive techno-economic analysis of the point-to-point hydrogen storage and transportation system based on compressed gas hydrogen (GH), liquid hydrogen (LH), pipeline hydrogen (PH), and liquid organic hydrogen carriers (LOHC) is investigated, respectively. The optimal economical point-to-point energy storage and transportation modes under various transportation distance and daily hydrogen demand are obtained. Then the economic analysis of different hydrogen storage and transportation modes under 1-to-N hydrogen storage and transportation scenario is conducted, which can significantly decrease the cost of LH storage and transportation mode. To step further, the 1-to-N relay hydrogen storage and transportation scenario is constructed to improve the applicability and reduce the unit cost. The economic analysis of 14 kinds of feasible combinations of hydrogen storage and transportation modes is systematically assessed. Regarding to the transportation distance and daily hydrogen demand, the optimal economical 1-to-N relay energy storage and transportation modes are identified. This study may contribute to rationally design and application for economic hydrogen storage and transportation systems. [Display omitted] • The economics of point-to-point hydrogen storage and transportation scenario is investigated. • The economics of the 1-to-N hydrogen storage and transportation scenario is analyzed. • 1-to-N relay hydrogen storage and transportation scenario is constructed to improve economic applicability. • 1-to-N relay hydrogen storage and transportation scenarios may exhibit obvious economic advantage. [ABSTRACT FROM AUTHOR]

The safety of hydrogen directly affects the use of hydrogen refueling stations and public acceptance of hydrogen energy. This paper presented a methodology for the optimal design of the minimum height, width, and safety distance of the firewall of the hydrogen refueling station under various leakage pressures. The obtained relationship between distances and different hydrogen storage pressures is essential for directing the design of hydrogen refueling stations and firefighters to carry out the rescue. Results from numerical simulation showed that the firewall should be 2 m taller than the leakage hole to prevent the hydrogen jet fire from spreading back. The distance before and behind the firewall presented a linear relationship with the leakage pressure. The specific safe distances behind the firewall were 8.4, 8.5, 9.2, and 9.3 m. The firewall width exhibited a non-linear relationship with the leakage pressure. The specific values were 2.5 m for 35 or 45 MPa and 3 m for 70 or 90 MPa. • Methodology for the optimal design of firewalls in hydrogen refueling stations is determined. • The firewall should be 2 m higher than the leakage hole. • Firewalls can deflect flames and prevent them from spreading behind walls. • The distance before and behind the firewall increases with the increase of hydrogen storage pressures. [ABSTRACT FROM AUTHOR]