Exergy and environmental impact assessment of solar photoreactors for catalytic hydrogen production
2012
Baniasadi, E. | Dincer, I. | Naterer, G.F.
In this paper, a new photo-catalytic energy conversion system is analyzed for continuous production of hydrogen at a pilot-plant scale. Two methods of photo-catalytic water splitting and solar methanol steam reforming are investigated as two potential solar-based methods of catalytic hydrogen production. The exergy efficiency, exergy destruction, environmental impact and sustainability index are investigated for these systems, as well as exergoenvironmental analyses. A Compound Parabolic Concentrator (CPC) is presented for the sunlight-driven hydrogen production system. This study shows that an optimum water flow rate exists, where the exergy efficiency of the photo-catalytic hydrogen production is maximized. The amount of CO₂ emissions that are reduced by this process increases at higher flow rates. The light intensity is one of the key parameters in design optimization of the photo-reactors, in conjunction with light absorptivity of the catalyst. The results show that a trade-off exists in terms of exergy efficiency improvement and CO₂ emissions of the photo catalytic hydrogen production system. The optimal working condition of solar methanol reforming to satisfy the exergy–environmental considerations is found to be light intensity range of 530Wm⁻²<J<600Wm⁻² and water–methanol mole ratio of 1.5–2. An optimum methanol feeding rate associated with CO₂ emissions of methanol steam reforming is determined in order to establish the required solar flux for photo-catalytic conversion of methanol to hydrogen.
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