Performance Characterization of a Hybrid PV-CSP-TES-PCM-SOEC System with Renewable Integration for Sustainable Hydrogen Production across Indian Climate Zones

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Original abstract

Continuous green hydrogen production from solar energy faces two fundamental challenges. Solar resources are inherently intermittent. At the same time, solid oxide electrolysis cells (SOECs) require a stable, high-temperature thermal input around the clock. This study proposes a hybrid photovoltaic-concentrated solar power-thermal energy storage-solid oxide electrolysis cell (PV-CSP-TES-SOEC) system. The system uses anhydrous magnesium chloride (MgCl₂) as a high-temperature phase-change material (melting point ≈ 714 °C; latent heat 452 kJ kg⁻¹). This material bridges overnight thermal energy deficits and enables uninterrupted SOEC operation without grid support. Five Indian climate zones were investigated - Jodhpur, Ladakh, Nagpur, Bengaluru, and Kochi, using a full 8760-hour hourly dynamic simulation with NSRDB SUNY TMY data, preceded by static sizing to establish baseline component requirements. Static sizing shows that PV area varies by 22% across sites, while CSP aperture varies by up to 55%. The required MgCl₂ mass ranges from 190 to 240 t under baseline conditions. After optimisation, the required PCM mass increases to 325.7-823.9 t. Nagpur requires the highest due to prolonged monsoon-related solar suppression. Under constant-load SOEC operation, hourly reliability reaches only 62.1 to 68.7%. Hydrogen output drops to 729-788 kg day⁻¹, which is 27-33% below the 1080 kg day⁻¹ target. This shortfall is caused entirely by TES depletion during pre-dawn hours. A three-period flexible scheduling strategy is introduced. The SOEC operates at 0.6× load at night, 1.0× during shoulder hours, and 1.5-1.8× during the solar peak. This strategy restores full hydrogen output and increases reliability to 95.1-95.7% across all five sites. This corresponds to an improvement of 26-34 percentage points compared to constant-load operation. The results demonstrate that demand-side scheduling optimisation, rather than infrastructure oversizing, is the decisive factor enabling near-continuous grid-independent solar hydrogen production across climatically diverse locations.

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