Photoelectrochemical water splitting is a promising route for the renewable production of hydrogen fuel. This work presents the results of a technical and economic feasibility analysis conducted for four hypothetical, centralized, large-scale hydrogen production plants based on this technology. The four reactor types considered were a single bed particle suspension system, a dual bed particle suspension system, a fixed panel array, and a tracking concentrator array. The current performance of semiconductor absorbers and electrocatalysts were considered to compute reasonable solar-tohydrogen conversion efficiencies for each of the four systems. The U.S. Department of Energy H2A model was employed to calculate the levelized cost of hydrogen output at the plant gate at 300 psi for a 10 tonne per day production scale. All capital expenditures and operating costs for the reactors and auxiliaries (compressors, control systems, etc.) were considered. The final cost varied from $1.60-$10.40 per kg H 2 with the particle bed systems having lower costs than the panel-based systems. However, safety concerns due to the cogeneration of O 2 and H 2 in a single bed system and long molecular transport lengths in the dual bed system lead to greater uncertainty in their operation. A sensitivity analysis revealed that improvement in the solar-to-hydrogen efficiency of the panel-based systems could substantially drive down their costs. A key finding is that the production costs are consistent with the Department of Energy's targeted threshold cost of $2.00-$4.00 per kg H 2 for dispensed hydrogen, demonstrating that photoelectrochemical water splitting could be a viable route for hydrogen production in the future if material performance targets can be met. Broader contextAs global energy consumption continues to rise, it is imperative that we develop renewable alternatives to the fossil fuel energy sources that currently power our civilization, curb CO 2 emissions, and secure a permanent energy supply for the future. Although the solutions to these global challenges are likely to consist of many different energy storage and conversion technologies, sustainably produced chemical fuels will likely play an important role due to their high energy density. Hydrogen gas is an especially promising energy carrier, but current hydrogen production processes such as steam methane reforming are unsustainable. Photoelectrochemical (PEC) water splitting is an alternative process that enables sustainable hydrogen production from water using the energy from sunlight. PEC water splitting has been demonstrated on the laboratory scale, but it has never been implemented on a large scale relevant to the global energy demand, so the prospects for scaling up this process have remained controversial. The present paper addresses the technical and economic feasibility of plants producing hydrogen via PEC water splitting. We establish practical operating efficiencies for PEC reactors, detail four potential reactor and centralized plant designs, and discuss the...

A techno-economic analysis was conducted for metal–organic framework (MOF) adsorbents, which are promising candidates for light-duty vehicle on-board natural gas and hydrogen storage. The goal of this analysis was to understand cost drivers for large-scale (2.5 Mkg/year) MOF synthesis and to identify potential pathways to achieving a production cost of less than $10/(kg of MOF). Four MOFs were analyzed with four different metal centers and three different linkers: Ni2(dobdc) (dobdc4– = 2,5-dioxido-1,4-benzenedicarboxylate; Ni-MOF-74), Mg2(dobdc) (dobdc4– = 2,5-dioxido-1,4-benzenedicarboxylate; Mg-MOF-74), Zn4O­(bdc)3 (bdc2– = 1,4-benzenedicarboxylate; MOF-5), and Cu3(btc)2 (btc3– = 1,3,5-benzenetricarboxylate; HKUST-1). Baseline costs are projected to range from $35/kg to $71/kg predicated on organic solvent (solvothermal) syntheses using an engineering scale-up of laboratory-demonstrated synthesis procedures and conditions. Two alternative processes were analyzed to evaluate the cost impact of reducing solvent usage: liquid assisted grinding (LAG) and aqueous synthesis. Cost projections from these alternative synthesis approaches range from $13/kg to $36/kg (representing 34–83% reductions), demonstrating the large impact of solvent on the baseline analysis. Finally, sensitivity studies were conducted to identify additional opportunities for achieving MOF production costs of less than $10/kg.

Several application fields can benefit from solar-hydrogen technologies via specific short-term and long-term pathways.

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