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The Pareto frontier is extensively adopted in multi-objective optimization, especially in multi-carrier energy system modeling. Despite the various methodologies available to derive the frontier, it represents different optimal solutions, making the final selection non-trivial. The modeler's expertise is crucial in determining the weight factors assigned to each objective for selecting the final solution from the Pareto frontier. This study proposes a novel approach to support such decision-making, introducing an additional key performance indicator, the state of health of the battery, evaluated through physical battery modeling. By comparing different scheduling schemes in multi-objective multi-carrier energy systems, each with its distinct battery operational strategy, this newly introduced indicator has deployed to automatically identify the ultimate solution from the Pareto frontier, without additional weighting coefficients. Such an approach, therefore, automates the decision process, which supports easy engineering, especially for the small scale multi-energy systems such as smart homes, like the case study presented in this work that has four distinct energy carriers, adopting the 12 V 128 Ah LFP chemistry Li-ion battery modules, demonstrates the effectiveness of this automated selection process. Furthermore, when compared to the maximum values across the entire frontier, the automatically chosen solution exhibits reductions of 27.96% in CO2 emissions and 3.67% reduction in overall costs. Over long-term operation, this approach has the potential to extend battery lifespan by up to 26.67%, directly impacting the economics of multi-carrier energy systems.

To mitigate climate change, a stronger reliance on renewable energy sources is foreseen, and Power-to-Hydrogen systems can be adopted to minimize curtailment losses derived from the intermittent nature of wind and solar power. Among different alternatives, alkaline water electrolysis is the most mature process for hydrogen production using sustainable electricity as its main energy source. The mathematical modelling of the alkaline electrolysis process is a crucial tool to improve green hydrogen production, energy conversion efficiency, sizing (model-based design) and thermal energy management. Although several studies have investigated alkaline electrolysis modelling, these analyses often neglect property variations along the stack area and its economic implications. In this work, the need for increasing the modelling complexity in system models by introducing a one-dimensional model of the alkaline electrolyzer cell/stack is investigated. With this, several operation parameter variations can be modelled, and among these, the internal temperature variation plays a crucial role in both technical and economic aspects. Results show that efficiency could vary between 58-70% while the Levelized cost of hydrogen is within the range of 1.3-1.6 €/kg, when various inlet-outlet temperature differences are considered. Furthermore, from both technical and economic aspects, the optimal temperature control of alkaline electrolysis is to maintain a very low-temperature difference (~1°C), from inlet to outlet, controllable with the alteration of the electrolyte flow rate.

Herein, a novel methodology to perform optimal sizing of AC-linked solar PV-PEM systems is proposed. The novelty of this work is the proposition of the solar plant to electrolyzer capacity ratio (AC/AC ratio) as optimization variable. The impact of this AC/AC ratio on the Levelized Cost of Hydrogen (LCOH) and the deviation of the solar DC/AC ratio when optimized specifically for hydrogen production are quantified. Case studies covering a Global Horizontal Irradiation (GHI) range of 1400–2600 kWh/m2-year are assessed. The obtained LCOHs range between 5.9 and 11.3 USD/kgH2 depending on sizing and location. The AC/AC ratio is found to strongly affect cost, production and LCOH optimality while the optimal solar DC/AC ratio varies up to 54% when optimized to minimize the cost of hydrogen instead of the cost of energy only. Larger oversizing is required for low GHI locations; however, H2 production is more sensitive to sizing ratios for high GHI locations., QC 20221024

Herein, a novel methodology to perform optimal sizing of AC-linked solar PV-PEM systems is proposed. The novelty of this work is the proposition of the solar plant to electrolyzer capacity ratio (AC/AC ratio) as optimization variable. The impact of this AC/AC ratio on the Levelized Cost of Hydrogen (LCOH) and the deviation of the solar DC/AC ratio when optimized specifically for hydrogen production are quantified. Case studies covering a Global Horizontal Irradiation (GHI) range of 1400–2600 kWh/m2-year are assessed. The obtained LCOHs range between 5.9 and 11.3 USD/kgH2 depending on sizing and location. The AC/AC ratio is found to strongly affect cost, production and LCOH optimality while the optimal solar DC/AC ratio varies up to 54% when optimized to minimize the cost of hydrogen instead of the cost of energy only. Larger oversizing is required for low GHI locations; however, H2 production is more sensitive to sizing ratios for high GHI locations., QC 20221024

Herein, a novel methodology to perform optimal sizing of AC-linked solar PV-PEM systems is proposed. The novelty of this work is the proposition of the solar plant to electrolyzer capacity ratio (AC/AC ratio) as optimization variable. The impact of this AC/AC ratio on the Levelized Cost of Hydrogen (LCOH) and the deviation of the solar DC/AC ratio when optimized specifically for hydrogen production are quantified. Case studies covering a Global Horizontal Irradiation (GHI) range of 1400–2600 kWh/m2-year are assessed. The obtained LCOHs range between 5.9 and 11.3 USD/kgH2 depending on sizing and location. The AC/AC ratio is found to strongly affect cost, production and LCOH optimality while the optimal solar DC/AC ratio varies up to 54% when optimized to minimize the cost of hydrogen instead of the cost of energy only. Larger oversizing is required for low GHI locations; however, H2 production is more sensitive to sizing ratios for high GHI locations., QC 20221024

Herein, a novel methodology to perform optimal sizing of AC-linked solar PV-PEM systems is proposed. The novelty of this work is the proposition of the solar plant to electrolyzer capacity ratio (AC/AC ratio) as optimization variable. The impact of this AC/AC ratio on the Levelized Cost of Hydrogen (LCOH) and the deviation of the solar DC/AC ratio when optimized specifically for hydrogen production are quantified. Case studies covering a Global Horizontal Irradiation (GHI) range of 1400–2600 kWh/m2-year are assessed. The obtained LCOHs range between 5.9 and 11.3 USD/kgH2 depending on sizing and location. The AC/AC ratio is found to strongly affect cost, production and LCOH optimality while the optimal solar DC/AC ratio varies up to 54% when optimized to minimize the cost of hydrogen instead of the cost of energy only. Larger oversizing is required for low GHI locations; however, H2 production is more sensitive to sizing ratios for high GHI locations., QC 20221024

Herein, a novel methodology to perform optimal sizing of AC-linked solar PV-PEM systems is proposed. The novelty of this work is the proposition of the solar plant to electrolyzer capacity ratio (AC/AC ratio) as optimization variable. The impact of this AC/AC ratio on the Levelized Cost of Hydrogen (LCOH) and the deviation of the solar DC/AC ratio when optimized specifically for hydrogen production are quantified. Case studies covering a Global Horizontal Irradiation (GHI) range of 1400–2600 kWh/m2-year are assessed. The obtained LCOHs range between 5.9 and 11.3 USD/kgH2 depending on sizing and location. The AC/AC ratio is found to strongly affect cost, production and LCOH optimality while the optimal solar DC/AC ratio varies up to 54% when optimized to minimize the cost of hydrogen instead of the cost of energy only. Larger oversizing is required for low GHI locations; however, H2 production is more sensitive to sizing ratios for high GHI locations., QC 20221024