Thank you for sharing your research in Hydrogen. I would like to share my observations and highlight a few issues I noticed in your article, “Hydrogen Production from Wave Power Farms to Refuel Hydrogen-Powered Ships in the Mediterranean Sea”:
1) Assumptions on Wave Energy Efficiency
The reported hydrodynamic efficiency values for the Wave Dragon converters (25–35%) are derived from secondary sources and generalized for the Mediterranean region. However, the Mediterranean’s mild wave climate presents unique challenges, and the absence of localized experimental or simulated validation raises questions about the applicability of these efficiency values. Could the authors clarify if Mediterranean-specific tests or calibrations were conducted?
2) Economic Feasibility Projections
The estimated reduction of the levelized cost of hydrogen (LCOH) to 3.6 €/kg assumes aggressive CAPEX reductions for wave energy converters and electrolyzers by 2050. However, benchmarks from current literature suggest that such reductions might be overly optimistic, particularly for nascent wave energy technologies. Could the authors provide more detailed justification or sensitivity analysis for these projections?
3) Constant Efficiency Assumptions
The assumption of a constant calibration coefficient (α = 0.9) for calculating the energy wave period (Te) is not explicitly validated. This simplification may not adequately reflect temporal and spatial variations in Mediterranean wave dynamics. Has the impact of this assumption on the results been quantified, or have alternative methods been considered?
4) Limited Discussion of Downtime and Intermittency
The potential for operational downtime and hydrogen shortages during low-wave-energy periods is underexplored, despite being a critical factor in the economic and logistical feasibility of hydrogen production systems. Including downtime or intermittency in the analysis could significantly affect the levelized cost estimates and overall feasibility. Could the authors elaborate on how these issues were addressed?
5) Representation of Results and References
The paper claims to uniquely assess the techno-economic feasibility of wave-powered hydrogen refueling stations in the Mediterranean. However, several studies cited (e.g., Friedrich et al., 2020; Bonacina et al., 2022) appear to address similar topics. Additionally, the exclusion of recent datasets and comparative benchmarks (e.g., solar or wind-powered hydrogen systems) limits the context of this analysis. How does this study differ substantively, and could recent data or comparative analyses be included to strengthen the conclusions?
6) Transparency in Supporting Data
Several key components of the study, such as the hydrodynamic performance of WECs, boil-off rate calculations, and cost breakdowns, lack detailed supporting data or references. For example, the method for deriving shading coefficients (nshading) is unclear and could benefit from more transparency or additional experimental validation. Could the authors provide further clarification or supplementary data?
These observations are intended to enhance the clarity and robustness of the study. I look forward to hearing your thoughts on these points and appreciate your contributions to this field. Thank you for considering these observations.