When Bigger Is Not Greener: Ensuring the Sustainability of Power- to-Gas Hydrogen on a National Scale

As the prices of photovoltaics and wind turbines continue to decrease, more renewable electricity-generating capacity is installed globally. While this is considered an integral part of a sustainable energy future by many nations, it also poses a significant strain on current electricity grids due to the inherent output variability of renewable electricity. This work addresses the challenge of renewable electricity surplus (RES) utilization with target-scaling of centralized power-to-gas (PtG) hydrogen production. Using the Republic of Korea as a case study, due to its ambitious plan of 2030 green hydrogen production capacity of 0.97 million tons year-1, we combine predictions of future, season-averaged RES with a detailed conceptual process simulation for green H2 production via polymer electrolyte membrane (PEM) electrolysis combined with a desalination plant in six distinct scale cases (0.5-8.5 GW). It is demonstrated that at scales of 0.5 to 1.75 GW the RES is optimally utilized, and PtG hydrogen can therefore outperform conventional hydrogen production both environmentally (650-2210 Mton CO2 not emitted per year) and economically (16-30% levelized cost reduction). Beyond these scales, the PtG benefits sharply drop, and thus it is answered how much of the planned green hydrogen target can realistically be if on an industrial scale

Economic evaluation with sensitivity and profitability analysis for hydrogen production from water electrolysis in Korea

Economic evaluation for water electrolysis compared to steam methane reforming has been carried out in terms of unit hydrogen production cost analysis, sensitivity analysis, and profitability analysis to assess current status of water electrolysis in Korea. For a hydrogen production capacity of 30 Nm(3) h(-1), the unit hydrogen production cost was 17.99, 16.54, and 20.18 $kg H-2(-1) for alkaline water electrolysis (AWE), PEM water electrolysis (PWE), and steam methane reforming (SMR), respectively with 11.24, 10.66, and 11.80 for 100 Nm(3) h(-1) and 8.12, 7.72, and 7.59$kg H-2(-1) for 300 Nm(3) h(-1). With sensitivity analysis (SA), the most influential factors on the unit hydrogen production cost depending on the hydrogen production capacity were determined. Lastly, profitability analysis (PA) presented a discounted payback period (DPBP), net present value (NPV), and present value ratio (PVR) for a different discount rate ranging from 2 to 14% and it was found that a discounted cash flow rate of return (DCFROR) was 14.01% from a cash flow diagram obtained for a hydrogen production capacity of 30 Nm(3) h(-1)

Economic feasibility studies of high pressure PEM water electrolysis for distributed H-2 refueling stations

In this paper, we report economic feasibility studies focusing on profitability analysis of high pressure polymer electrolyte membrane (PEM) water electrolysis for distributed H-2 refueling stations in Korea. From capital and operating costs, a unit H-2 production cost of 6.24 $kgH(2)(-1) was obtained for a H-2 capacity of 700 m(3) h(-1), which is equivalent to handling about 300 fuel cell electric vehicles. Based on cost estimations, profitability analysis using cash flow diagrams was performed to assess the economic feasibility of high pressure PEM water electrolysis and various key economic indicators like net present value (NPV), discounted payback period (DPBP), and present value ratio were obtained for both different discount rates and capacity factors. In conclusion, employment of high pressure PEM water electrolysis was found to be economically profitable showing reasonably high NPVs (16-52 MM$) and short DPBPs (4-7 years)

Economic evaluation with uncertainty analysis using a Monte-Carlo simulation method for hydrogen production from high pressure PEM water electrolysis in Korea

Economic analysis with uncertainty analysis based on a Monte-Carlo simulation method was performed for hydrogen production from high pressure PEM water electrolysis targeting a hydrogen production capacity of 30 Nm(3) h(-1) in Korea. With key economic parameters obtained from sensitivity analysis (SA), a cumulative probability curve was constructed for a unit H-2 production cost fully reflecting unpredictable price fluctuations in H-2 production equipment, construction, electricity, and labor from +/- 10% to +/- 50%. In addition, economic analysis for a net present value (NPV) with uncertainty analysis for revenue (REV), fixed capital investment (FCI), and cost of manufacturing (COM) provided cumulative probability curves with different discount rates and more reliable NPVs (-$69,000 similar to$1,308,000) for high pressure PEM water electrolysis under development in Korea. This economic analysis based on uncertainty can serve as important economic indicators suitable for premature technology like high pressure PEM water electrolysis currently being in progress in Korea

Three-dimensional CFD simulation of proton exchange membrane water electrolyser: Performance assessment under different condition

Hydrogen produced by the electrochemical water splitting is essential for expanding and utilizing renewable power sources and establishing a sustainable energy society. As renewable energy network widely established, the produced hydrogen can be utilized by connecting the energy demand and energy supply. The proton exchange membrane (PEM) water electrolyser technology is one of the ideal candidates for direct coupling with renewable energy sources. In recent years, bench-scale experiments, and computational fluid dynamics (CFD) simulation-based approaches are used to accelerate the advances in performance and cost of the technology. We studied the influence of the key performance parameter of a PEM water electrolyser, and a single channel-based three-dimensional CFD model was developed. The PEM water electrolyser CFD model is validated against inhouse experiments, where the developed model successfully predicts the current-voltage polarization curve. The developed CFD model is then used to analyze the influence of temperature, cathode pressure, membrane thickness, porous transport layer porosity and water feed rate. The main observation from the numerical study was discussed to provide insight into the factors affecting the PEM water electrolyser performance

Systematic assessment of the anode flow field hydrodynamics in a new circular PEM water electrolyser

In this work, we investigated the key underlying flow characteristics of a circular unit cell proton exchange membrane (PEM) water electrolyser. In particular, we focused on investigating anode flow field design using computational fluid dynamics (CFD) tool. Transient, 3D single phase fluid flow simulation results were presented, and in-house experiments were conducted for validation against CFD simulation data identifying key performance parameters of the PEM water electrolyser: uniform water distribution, pressure drop and hydraulic retention time. The effects of the water flow rate, inlet and outlet sizing and different number of inlet and outlet configurations were considered. The main observation from the study was discussed to provide insight into the factors affecting the flow pattern. Among the studied flow field design cases, it was found that the average pressure drop decreased with increase in number of inlets, also flow profile can be grouped into different set, depending on number of inlets. The correlation between pressure drop and mean velocity profile for different inlet and outlet configurations provides a useful basis to properly design the high performance PEM water electrolyser. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved