Integration of Photocatalytic Hydrogen Production with a Pem Fuel Cell-Based Off-Grid Cold Storage System: Thermodynamic, Dynamic Solar, and Environmental Performance Analysis across Three Technology Readiness Scenarios

Abstract

This study presents a thermodynamic, dynamic solar, and environmental performance analysis of an integrated off-grid system combining photocatalytic hydrogen (H2) production with a proton exchange membrane (PEM) fuel cell and a vapor-compression cold storage unit (R290) for a representative Mediterranean site (Adana, Türkiye, 37.0°N). A critical methodological advance over prior simulations is the adoption of a three-scenario framework explicitly grounded in real outdoor pilot data: Scenario S1 (STH = 0.9%, TiO2-CuO/P25); Scenario S2 (STH = 2.81%, Pd/TiO2); and Scenario S3 (STH = 10%, Z-scheme heterojunction, DOE 2030 target). All three scenarios share the same 20m2 reactor aperture derived from a closed energy-balance calculation requiring the S2 system to meet the full annual cooling demand of a 400-L cabinet and identical system architecture; only the photocatalytic efficiency differs. Dynamic simulation uses 8760 hourly TMY data points from PVGIS-SARAH2. First- and second-law analyses employ the Petela solar exergy model and the Gouy - Stodola theorem. The primary objective is to determine the minimum solar-to-hydrogen (STH) efficiency at which the integrated system becomes carbon-competitive with a diesel reference, rather than to propose a deployment-ready design. A central finding is the identification of a carbon break-even STH of approximately 1.04%: below this threshold the system produces a higher lifecycle carbon footprint than the diesel reference it replaces; above it, meaningful GHG savings accumulate. S1 (STH = 0.9%), which represents the current state of practice at pilot scale, sits marginally below this threshold (system GWP = 0.356 kg CO2-eq/kWh; carbon payback 19.6 years). S2 (STH = 2.81%) crosses the threshold convincingly: system GWP = 0.184 kg CO2-eq/kWh; 42.9% GHG reduction versus diesel; carbon payback 6.3 years. S3 achieves system GWP = 0.023 kg CO2-eq/kWh and 92.9% GHG reduction. These findings provide quantitative technology targets and identify photocatalyst development as the sole rate-limiting factor for deployment.

Keywords

• Photocatalytic hydrogen production
• PEM fuel cell
• Off-grid cold storage
• Thermodynamic and exergy analysis
• Carbon break-even
• R290 refrigeration system

Ethical Statement

Ethics committee approval was not required for this study because there was no study on animals or humans.

Thanks

The author acknowledges the European Commission Joint Research Centre for providing the PVGIS-SARAH2 database used in this study.

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