Applications & Pathways

Hybrid energy storage systems (HESS) are considered for use in renewable residential DC microgrids. This architecture is shown as a technically feasible solution to deal with the stochasticity of renewable energy sources however the complexity of its design and management increases inexorably. To address this problem this paper proposes a fuzzy logic-based energy management system (EMS) for use in grid-connected residential DC microgrids with HESS. It is a hydrogen-based HESS composed of batteries and multi-stack fuel cell system. The proposed EMS is based on a multivariable and multistage fuzzy logic controller specially designed to cope with a multi-objective problem whose solution increases the microgrid performance in terms of efficiency operating costs and lifespan of the HESS. The proposed EMS considers the power balance in the microgrid and its prediction the performance and degradation of its subsystems as well as the main electricity grid costs. This article assesses the performance of the developed EMS with respect to three reference EMSs present in the literature: the widely used dual-band hysteresis and two based on multi-objective model predictive control. Simulation results show an increase in the performance of the microgrid from a technical and economic point of view.

The reduction of greenhouse gas emissions is one of the greatest global challenges through 2050. Besides greenhouse gas emissions air pollution such as nitrogen oxide and particulate matter emissions has gained increasing attention in agglomerated areas with transport vehicles being one of the main sources thereof. Alternative fuels that fulfill the greenhouse gas reduction goals also offer the possibility of solving the challenge of rising urban pollution. This work focuses on the electric drive option for heavy and light duty vehicle freight transport. In this study fuel cell-electric vehicles battery-electric vehicles and overhead catenary line trucks were investigated taking a closer look at their potential to reduce greenhouse gas emissions and air pollution and also considering the investment and operating costs of the required infrastructure. This work was conducted using a bottom-up transport model for the federal state of North Rhine-Westphalia in Germany. Two scenarios for reducing these emissions were analyzed at a spatial level. In the first of these selected federal highways with the highest traffic volume were equipped with overhead catenary lines for the operation of diesel-hybrid overhead trucks on them. For the second spatial scenario the representative urban area of the city of Cologne was investigated in terms of air pollution shifting articulated trucks to diesel-hybrid overhead trucks and rigid trucks trailer trucks and light duty vehicles to battery-electric or fuel cell-electric drives. For the economic analysis the building up of a hydrogen infrastructure in the cases of articulated trucks and all heavy duty vehicles were also taken into account. The results showed that diesel-hybrid overhead trucks are only a cost-efficient solution for highways with high traffic volume whereas battery overhead trucks have a high uncertainty in terms of costs and technical feasibility. In general the broad range of costs for battery overhead trucks makes them competitive with fuel cell-electric trucks. Articulated trucks have the highest potential to be operated as overhead trucks. However the results indicated that air pollution is only partially reduced by switching conventional articulated trucks to electric drive models. The overall results show that a comprehensive approach such as fuel cell-electric drives for all trucks would most likely be more beneficial.

The production of fat steel products is commonly linked to highly integrated sites which include hot metal generation via the blast furnace basic oxygen furnace (BOF) continuous casting and subsequent hot-rolling. In order to reach carbon neutrality a shift away from traditional carbon-based metallurgy is required within the next decades. Direct reduction (DR) plants are capable to support this transition and allow even a stepwise reduction in CO2 emissions. Nevertheless the implementation of these DR plants into integrated metallurgical plants includes various challenges. Besides metallurgy product quality and logistics special attention is given on future energy demand. On the basis of carbon footprint methodology (ISO 14067:2019) diferent scenarios of a stepwise transition are evaluated and values of possible CO2equivalent (CO2eq) reduction are coupled with the demand of hydrogen electricity natural gas and coal. While the traditional blast furnace—BOF route delivers a surplus of electricity in the range of 0.7 MJ/kg hot-rolled coil; this surplus turns into a defcit of about 17 MJ/ kg hot-rolled coil for a hydrogen-based direct reduction with an integrated electric melting unit. On the other hand while the product carbon footprint of the blast furnace-related production route is 2.1 kg CO2eq/kg hot-rolled coil; this footprint can be reduced to 0.76 kg CO2eq/kg hot-rolled coil for the hydrogen-related route provided that the electricity input is from renewable energies. Thereby the direct impact of the processes of the integrated site can even be reduced to 0.15 kg CO2eq/ kg hot-rolled coil. Yet if the electricity input has a carbon footprint of the current German or European electricity grid mix the respective carbon footprint of hot-rolled coil even increases up to 3.0 kg CO2eq/kg hot-rolled coil. This underlines the importance of the availability of renewable energies.

The integration of electrolyzers and fuel cells can cause voltage fluctuations within microgrids if not properly scheduled. Therefore controlling voltage and reactive power becomes crucial to mitigate the impact of fluctuating voltage levels ensuring system stability and preventing damage to equipment. This paper therefore seeks to enhance voltage and reactive power control within reconfigurable microgrids in the presence of innovative power-to-hydrogen technologies via electrolyzers and hydrogen-to-power through fuel cells. Specifically it focuses on the simultaneous coordination of an electrolyzer hydrogen storage and a fuel cell alongside on-load tap changers smart photovoltaic inverters renewable energy sources diesel generators and electric vehicle aggregation within the microgrid system. Additionally dynamic network reconfiguration is employed to enhance microgrid flexibility and improve the overall system adaptability. Given the inherent unpredictability linked to resources the unscented transformation method is employed to account for these uncertainties in the proposed voltage and reactive power management. Finally the model is formulated as a convex optimization problem and is solved through GUROBI version 11 which leads to having a time-efficient model with high accuracy. To assess the effectiveness of the model it is eventually examined on a modified 33-bus microgrid in several cases. Through the results of the under-study microgrid the developed model is a great remedy for the simultaneous operation of diverse resources in reconfigurable microgrids with a flatter voltage profile across the microgrid.

Hydrogen offers an effective pathway for the large‑scale storage of renewable energy. For a tourist city located in a plateau region rich in renewable energy hydrogen shows great potential for reducing carbon emissions and utilizing uncertain renewable energy. Herein the wind–solar–hydrogen stand‑alone and grid‑connected systems in the plateau tourist city of Lijiang City in Yunnan Province are modeled and techno‑economically evaluated by using the HOMER Pro software (version 3.14.2) with the multi‑criteria decision anal‑ ysis models. The system is composed of 5588 kW solar photovoltaic panels an 800 kW wind turbine a 1600 kW electrolyzer a 421 kWh battery and a 50 kW fuel cell. In addi‑ tion to meeting the power requirements for system operation the system has the capacity to provide daily electricity for 200 households in a neighborhood and supply 240 kg of hydrogen per day to local hydrogen‑fueled buses. The stand‑alone system can produce 10.15 × 106 kWh of electricity and 93.44 t of hydrogen per year with an NPC of USD 8.15 million an LCOE of USD 0.43/kWh and an LCOH of USD 5.26/kg. The grid‑connected system can generate 10.10 × 106 kWh of electricity and 103.01 ton of hydrogen annually. Its NPC is USD 7.34 million its LCOE is USD 0.11/kWh and its LCOH is USD 3.42/kg. This study provides a new solution for optimizing the configuration of hybrid renewable en‑ ergy systems which will develop the hydrogen economy and create low‑carbon‑emission energy systems.

Population growth and economic development have significantly increased global energy demand. Hence it has raised concerns about the increase in the consumption of fossil fuels and climate change. The present work introduced a new approach to using carbon-free energy sources such as nuclear and renewable to meet energy demand. The idea of using the Nuclear-Renewable Hybrid Energy System (N-R HES) is suggested as a leading solution that couples a nuclear power plant with renewable energy and hydrogen-based storage systems. For this purpose using a meta-heuristic method based on Newton’s laws the configuration of the N-R HES is optimized from an economic and reliability point of view. The optimal system is selected from among six cases with different subsystems such as wind turbine photovoltaic panel nuclear reactor electrolysis fuel cell and hydrogen storage tank. Furthermore the performance of hydrogen-based energy storage systems such as hightemperature electrolysis (HTE) and low-temperature electrolysis (LTE) is evaluated from technical and economic aspects. The results of this work showed that using nuclear energy to supply the base load increases the reliability of the system and reduces the loss of power supply probability to zero. More than 70 % of the power is produced by nuclear reactors which includes more than 80 % of the system costs. The key findings showed that despite HTE’s higher efficiency using LTE as a storage system in N-R HES is more cost-effective. Finally due to recent developments and the safer design of nuclear reactors they can play an important role in combination with renewable energies to support carbon-free energy sectors especially in remote areas for decades to come.

Sustainability goals include the utilization of renewable energy resources to supply the energy needs in addition to wastewater treatment to satisfy the water demand. Moreover hydrogen has become a promising energy carrier and green fuel to decarbonize the industrial and transportation sectors. In this context this research investigates a wind-photovoltaic power plant to produce green hydrogen for hydrogen refueling station and to operate an electrocoagulation water treatment unit in Ostrava Czech Republic’s northeast region. The study conducts a techno-economic analysis through HOMER Pro® software for optimal sizing of the power station components and to investigate the economic indices of the plant. The power station employs photovoltaic panels and wind turbines to supply the required electricity for electrolyzers and electrocoagulation reactors. As an offgrid system lead acid batteries are utilized to store the surplus electricity. Wind speed and solar irradiation are the key role site dependent parameters that determine the cost of hydrogen electricity and wastewater treatment. The simulated model considers the capital operating and replacement costs for system components. In the proposed system 240 kg of hydrogen as well as 720 kWh electrical energy are daily required for the hydrogen refueling station and the electrocoagulation unit respectively. Accordingly the power station annually generates 6997990 kWh of electrical energy in addition to 85595 kg of green hydrogen. Based on the economic analysis the project’s NPC is determined to be €5.49 M and the levelized cost of Hydrogen (LCH) is 2.89 €/kg excluding compressor unit costs. This value proves the effectiveness of this power system which encourages the utilization of green hydrogen for fuel-cell electric vehicles (FCVs). Furthermore emerging electrocoagulation studies produce hydrogen through wastewater treatment increasing hydrogen production and lowering LCH. Therefore this study is able to provide practicable methodology support for optimal sizing of the power station components which is beneficial for industrialization and economic development as well as transition toward sustainability and autonomous energy systems.

Growing interest in sustainable energy has gathered significant attention for alternative technologies with hydrogen-based solutions emerging as a crucial component in the transition to cleaner and more resilient energy systems. Following that hydrogenbased microgrids integrated with renewable energy sources including wind and solar have gained substantial attention as an upcoming pathway toward long-term energy sustainability. Hydrogen produced through processes such as electrolysis and steam methane reforming can be stored in various forms including compressed gas liquid or solid-state hydrides and later utilized for electricity generation through fuel cells and gas turbines. This dynamic energy system offers highly flexible scalable and resilient solutions for various applications. Specifically hydrogen-based microgrids are particularly suitable for offshore and islanded applications with geographical factors adverse environmental conditions and limited access to conventional energy solutions. This is critical for energy independence long-term storage capacity and grid stability. This review explores topological and functional-based classifications of microgrids advancements in hydrogen generation storage and utilization technologies and their integration with microgrid systems. It also critically evaluates the key challenges of each technology including cost efficiency and scalability which impact the feasibility of hydrogen microgrids.

Solid oxide cells (SOC) play a major role in strategic visions to achieve decarbonization and climate-neutrality. With its multifuel capability this technology has received rapidly growing amount of attention from researchers worldwide. Due to the great flexibility of SOCs with respect to the fuels that can be used not only hydrogen but also biogas natural gas diesel reformates and many other conventional and alternative fuels can be used. This makes it possible to couple SOCs with diverse sustainable fuel sources to generate electricity or to generate valuable fuels such as syngas when utilizing renewable electricity. In this paper the reader is provided with a review of the existing knowledge about solid oxide fuel cell (SOFC) and solid oxide electrolysis (SOE) systems and how to safely operate them over the long-term placing a special focus on real-world operating environments. Both the utilization and generation of real commercially available fuels are taken into consideration. Different failure modes can appear during the system operation under real-world conditions and reduce the SOC lifetime an aspect that is extensively discussed in this review. Firstly a detailed discussion of the difference between carbon-free and carbon-containing fuels is presented considering different impurities and their impacts on the SOC performance stability and lifetime. Secondly unfavorable operating conditions are presented and possibilities for the early identification of different failure modes are explored. An overview of available conventional and non-conventional diagnostic tools and their applications is provided here. Overall this review paper presents a guideline for all relevant degradation issues related to SOCs operated in a real-world environment describing (i) how these issues appear and how to understand them (ii) how to predict them (iii) how to identify them and (iv) how to prevent them as well as if required how to reverse them. To achieve this goal individual chapters specifically address failure modes degradation prediction degradation prevention and performance regeneration. The reader is provided with necessary knowledge about the long-term and short-term operating stability and the degradation provoked in a compact summary. The available knowledge about specific process frequencies is summarized in one diagram which is a novel contribution of this review. This enables researchers to rapidly identify all occurring process mechanisms with SOFCs and SOECs. Moreover suggestions for how to accelerate degradation and how to regenerate performance are summarized in several tables.

Integrating electric technologies such as battery energy storage systems and electric propulsion has become an appealing option for reducing fuel consumption and emissions in the transportation sector making these technologies increasingly popular for research and industrial application in the maritime sector. In addition hydrogen is a promising technology for reducing emissions although hydrogen production technologies significantly influence the overall impact of hydrogen-powered systems. This paper proposes an optimizationbased strategy to minimize the environmental impact of a hybrid propulsion system over a given load profile while furthermore considering the environmental impact resulting from the hydrogen production chain. The propulsion system includes diesel generators hydrogen-powered fuel cells batteries and electric motors; mathematical models and assumptions are discussed in detail. The paper applies the proposed strategy and compares different hybrid solutions considering equivalent CO2 emissions discussing a test case applied to a short-range ferry operating in a marine protected area an area particularly sensitive to the problem of atmospheric emissions. The results demonstrate that the proposed strategy can reduce greenhouse gas emissions by up to 73% compared to a conventional mechanical propulsion system.