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

Understanding of Polarization-Induced Threshold Voltage Shift in Ferroelectric-Gated Field Effect Transistor for Neuromorphic Applications

A ferroelectric-gated fin-shaped field effect transistor (Fe-FinFET) is fabricated by connecting a Pb(Zr0.2Ti0.8)O3-based ferroelectric capacitor into the gate electrode of FinFET. The ferroelectric capacitor shows coercive voltages of approximately −1.5 V and 2.25 V. The polarization-induced threshold voltage shift in the Fe-FinFET is investigated by regulating the gate voltage sweep range. When the maximum positive gate to source voltage is varied from 4 V to 2 V with a fixed starting negative gate to source voltage, the threshold voltage during the backward sweep is increased from approximately −0.60 V to 1.04 V. In the case of starting negative gate to source voltage variation from −4 V to −0.5 V with a fixed maximum positive gate to source voltage of 4 V, the threshold voltage during the forward sweep is decreased from 1.66 V to 0.87 V. Those results can be elucidated with polarization domain states. Lastly, it is observed that the threshold voltage is mostly increased/decreased when the positive/negative gate voltage sweep range is smaller/larger than the positive/negative coercive voltage, respectively

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 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

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)

Prediction Model for Random Variation in FinFET Induced by Line-Edge-Roughness (LER)

As the physical size of MOSFET has been aggressively scaled-down, the impact of process-induced random variation (RV) should be considered as one of the device design considerations of MOSFET. In this work, an artificial neural network (ANN) model is developed to investigate the effect of line-edge roughness (LER)-induced random variation on the input/output transfer characteristics (e.g., off-state leakage current (Ioff), subthreshold slope (SS), saturation drain current (Id,sat), linear drain current (Id,lin), saturation threshold voltage (Vth,sat), and linear threshold voltage (Vth,lin)) of 5 nm FinFET. Hence, the prediction model was divided into two phases, i.e., “Predict Vth” and “Model Vth”. In the former, LER profiles were only used as training input features, and two threshold voltages (i.e., Vth,sat and Vth,lin) were target variables. In the latter, however, LER profiles and the two threshold voltages were used as training input features. The final prediction was then made by feeding the output of the first model to the input of the second model. The developed models were quantitatively evaluated by the Earth Mover Distance (EMD) between the target variables from the TCAD simulation tool and the predicted variables of the ANN model, and we confirm both the prediction accuracy and time-efficiency of our model

Liquid-phase catalytic reactor combined with measurement of hot electron flux and chemiluminescence

Understanding the role of electronically nonadiabatic interactions during chemical reactions on metal surfaces in liquid media is of great importance for a variety of applications including catalysis, electrochemistry, and environmental science. Here, we report the design of an experimental apparatus for detection of the highly excited (hot) electrons created as a result of nonadiabatic energy transfer during the catalytic decomposition of hydrogen peroxide on thin-film metal-semiconductor nanodiodes. The apparatus enables the measurement of hot electron flows and related phenomena (e.g., surface chemiluminescence) as well as the corresponding reaction rates at different temperatures. The products of the chemical reaction can be characterized in the gaseous phase by means of gas chromatography. The combined measurement of hot electron flux, catalytic activity, and light emission can lead to a fundamental understanding of the elementary processes occurring during the heterogeneous catalytic reaction. © 2016 Author(s)3

Hot Electrons at Solid–Liquid Interfaces: A Large Chemoelectric Effect during the Catalytic Decomposition of Hydrogen Peroxide

The study of energy and charge transfer during chemical reactions on metals is of great importance for understanding the phenomena involved in heterogeneous catalysis. Despite extensive studies, very little is known about the nature of hot electrons generated at solid–liquid interfaces. Herein, we report remarkable results showing the detection of hot electrons as a chemicurrent generated at the solid–liquid interface during decomposition of hydrogen peroxide (H2O2) catalyzed on Schottky nanodiodes. The chemicurrent reflects the activity of the catalytic reaction and the state of the catalyst in real time. We show that the chemicurrent yield can reach values up to 10¢1 electrons/O2 molecule, which is notably higher than that for solid–gas reactions on similar nanodiodes. (c) 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim3

Impact of Chamber/Annealing Temperature on the Endurance Characteristic of Zr:HfO₂ Ferroelectric Capacitor

The endurance characteristic of Zr-doped HfO2 (HZO)-based metal–ferroelectric–metal (MFM) capacitors fabricated under various deposition/annealing temperatures in the atomic layer deposition (ALD) process was investigated. The chamber temperature in the ALD process was set to 120 °C, 200 °C, or 250 °C, and the annealing temperature was set to 400 °C, 500 °C, 600 °C, or 700 °C. For the given annealing temperature of 700 °C, the remnant polarization (2Pr) was 17.21 µC/cm2, 26.37 µC/cm2, and 31.8 µC/cm2 at the chamber temperatures of 120 °C, 200 °C, and 250 °C, respectively. For the given/identical annealing temperature, the largest remnant polarization (Pr) was achieved when using the chamber temperature of 250 °C. At a higher annealing temperature, the grain size in the HZO layer becomes smaller, and thereby, it enables to boost up Pr. It was observed that the endurance characteristics for the capacitors fabricated under various annealing/chamber temperatures were quite different. The different endurance characteristics are due to the oxygen and oxygen vacancies in ferroelectric films, which affects the wakeup/fatigue behaviors. However, in common, all the capacitors showed no breakdown for an externally applied pulse (up to 108 cycles of the pulse)