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Power-electronics-based power-hardware-in-loop (PHIL) simulator for water electrolyzer emulation with a nominal current of 405 A is developed to study the electrolyzer as part of a smart grid and to analyze the characteristics of various electrolyzer power supply electronics. A simplified model of a proton exchange membrane (PEM) electrolyzer is implemented into the PHIL simulator to describe the voltage and current characteristics of the electrolyzer stack. The model is verified comparing the current and the estimated hydrogen production of the PHIL simulator with the measured values of the commercial PEM electrolyzer following the measured solar photovoltaic (PV) system output power. [ABSTRACT FROM AUTHOR]

The pace at which the human population is growing raises serious concerns related to food security while at the same time conventional agriculture-based food production is becoming a major cause of environmental pollution and greenhouse gas emissions. Numerous solutions have been proposed to boost food production among which edible microbial biomass is considered a promising alternative to conventional sources of food and feed with lower environmental footprint. This work introduces the Neo-Carbon Food concept that is a pilot-scale hybrid biological–inorganic process suitable for the production of microbial biomass. The concept includes integrated hydrogen production by water electrolysis, direct air capture (DAC) of carbon dioxide, and its subsequent assimilation by autotrophic hydrogen-oxidizing bacteria (HOB). The hydrogen production with in situ electrolysis achieved specific energy consumption just below 100 kWh/kgH 2 while the specific energy consumption of DAC was around 20 kWh/kg CO 2. Image 1 • Microbial protein could be a sustainable source of protein. • A pilot-scale hybrid biological-inorganic system is presented. • Novel in situ water electrolysis stack is introduced. • Energy consumption of hydrogen production and direct air capture of CO2 is studied. [ABSTRACT FROM AUTHOR]

Owing to the ongoing energy crisis, increasing shares of renewables, and climate mitigation targets, a green hydrogen economy through water electrolysis has gained interest. Hydrogen can be directly utilised or converted via different Power-to-X pathways to produce fossil-free substitutable products; therefore, their life-cycle emissions were studied to determine whether these solutions could provide sustainable alternatives. Thus, understanding which Power-to-X solution can provide the greatest greenhouse gas emission reduction is crucial. This study provides nine meta-analyses of different pathways to compare climate emissions reductions based on the literature. The minimum, maximum, and average values were estimated for each investigated Power-to-X pathway. The direct use of hydrogen or its service to produce steel, biogas upgrading, protein, or ammonia resulted in over 10 kg CO2 kg H2 −1 reductions on average while using low-carbon energy sources. Co-electrolysis can potentially provide higher emission savings owing to lower electricity consumption compared with low-temperature electrolysers. In addition, the possibility of integrating electrochemical synthesis with hydrogen production has great potential, but the usability depends on the advancement of the technology in the future. Selections of carbon dioxide sources, substitutable products, and other assumptions of the investigated studies significantly impact the reduction potential. Low-emission-factor electric grid mixes containing fossil sources can result in emission savings in many Power-to-X systems. However, using grid mixes that result in emission savings is system-dependent, and the largest emission savings are achieved through renewables or nuclear energy. • Emission reductions were evaluated in the different pathways using hydrogen. • Power-to-X solutions using carbon dioxide resulted in the least reductions. • Co-electrolysis is an interesting option but is unmatured technology. • Green hydrogen is not the only hydrogen source capable of emission reduction. • LCA studies using primary data are desirable. [ABSTRACT FROM AUTHOR]

Green hydrogen production systems will play an important role in the energy transition from fossil-based fuels to zero-carbon technologies. This paper investigates a concept of an off-grid alkaline water electrolyzer plant integrated with solar photovoltaic (PV), wind power, and a battery energy storage system (BESS). The operation of the plant is simulated over 30 years with 5 min time resolution based on measured power generation data collected from a solar photovoltaic installation and a wind farm located in southeastern Finland. Levelized cost of hydrogen (LCOH) is calculated based on the capital expenditures (CAPEX), the operating expenses (OPEX), and the respective learning curves for each of the components. Component degradation and replacements during the operational lifetime are included in the model, and the capacity of the components and the system control are simultaneously optimized to obtain the minimum LCOH. A sensitivity analysis performed over different installation years and discount rates reveals that for the off-grid alkaline system, the implementation of a wind farm as the sole power supply is the most economical solution until the installation years 2035–2040. Solar PV and a BESS are found to increase the full-load hours of the electrolyzer and reduce the electricity curtailed in the off-grid plant to less than 8%. However, with the current component prices and the climate in the studied region, they are not economically beneficial. It is found that the cost of hydrogen can be reduced to 2 €/kg by the year 2030. • Optimal control and component capacities for a green hydrogen production plant. • Simulations use measured power from a solar PV installation and a wind farm. • Levelized cost of hydrogen is less than 2 €/kg by the year 2030. • Purely wind based system is the most cost-effective solution until the years 2035–2040. [ABSTRACT FROM AUTHOR]

The capacity of each component in an off-grid water electrolyzer hydrogen production plant integrated with solar photovoltaics and a battery energy storage system represents a significant factor affecting the viability and reliability of the system. This paper describes a novel method that optimizes simultaneously the component capacities and finite-state machine based control of the system to minimize the cost of green hydrogen production. The components and control in the system are referenced to a proton exchange membrane water electrolyzer stack with a fixed nominal power of 4.5 kW. The end results are thus scalable by changing the nominal power of the electrolyzer. Simulations are carried out based on data collected from a residential solar photovoltaic installation with 300 s time resolution. Optimization of the system is performed with particle swarm optimization algorithm. A sensitivity analysis performed over the prices of the different components reveals that the price of the water electrolyzer has the greatest impact on the green hydrogen production cost. It is found that the price of the battery has to be below 0.3 €/Wh to become a feasible solution as overnight energy storage. • System components and control are optimized simultaneously using PSO algorithm. • Simulations are based on data collected from an existing solar PV installation. • Electrolyzer price has the strongest effect on off-grid hydrogen production cost. • Overnight hydrogen production becomes economic below 0.3 €/Wh battery system price. [ABSTRACT FROM AUTHOR]