High Temperature Water Electrolysis Using Metal Supported Solid Oxide Electrolyser Cells (SOEC)

Metal supported cells as developed according to the DLR SOFC concept by applying plasma deposition technologies were investigated for use as solid oxide electrolyser cells (SOEC) for high temperature steam electrolysis. Cells consisting of a porous ferritic steel support, a diffusion barrier layer, a Ni/YSZ hydrogen electrode, a YSZ electrolyte and a LSCF oxygen electrode were electrochemically characterised by means of i-V characteristics and electrochemical impedance spectroscopy measurements including a long-term test over 2000 hours. The cell voltage during electrolysis operation at a current density of -1.0 A cm-2 was 1.28 V at an operating temperature of 850 °C and 1.4 V at 800 °C. A long-term test run over 2000 hours with a steam content of 43% at 800 °C and a current density of -0.3 A cm-2 showed a degradation rate of 3.2% per 1000 hours. The impedance spectra revealed a significantly enhanced polarisation resistance during electrolysis operation compared to fuel cell operation which was mainly attributed to the hydrogen electrode

Self-sustainable protonic ceramic electrochemical cells using a triple conducting electrode for hydrogen and power production.

The protonic ceramic electrochemical cell (PCEC) is an emerging and attractive technology that converts energy between power and hydrogen using solid oxide proton conductors at intermediate temperatures. To achieve efficient electrochemical hydrogen and power production with stable operation, highly robust and durable electrodes are urgently desired to facilitate water oxidation and oxygen reduction reactions, which are the critical steps for both electrolysis and fuel cell operation, especially at reduced temperatures. In this study, a triple conducting oxide of PrNi0.5Co0.5O3-δ perovskite is developed as an oxygen electrode, presenting superior electrochemical performance at 400~600 °C. More importantly, the self-sustainable and reversible operation is successfully demonstrated by converting the generated hydrogen in electrolysis mode to electricity without any hydrogen addition. The excellent electrocatalytic activity is attributed to the considerable proton conduction, as confirmed by hydrogen permeation experiment, remarkable hydration behavior and computations

Comparative energetic assessment of methanol production from CO₂: chemical versus electrochemical process

Emerging emission-to-liquid (eTL) technologies that produce liquid fuels from CO₂ are a possible solution for both the global issues of greenhouse gas emissions and fossil fuel depletion. Among those technologies, CO₂ hydrogenation and high-temperature CO₂ electrolysis are two promising options suitable for large-scale applications. In this study, two CO₂ -to-methanol conversion processes, i.e., production of methanol by CO₂ hydrogenation and production of methanol based on high-temperature CO₂ electrolysis, are simulated using Aspen HYSYS. With Aspen Energy Analyzer, heat exchanger networks are optimized and minimal energy requirements are determined for the two different processes. The two processes are compared in terms of energy requirement and climate impact. It is found that the methanol production based on CO₂ electrolysis has an energy efficiency of 41%, almost double that of the CO₂ hydrogenation process provided that the required hydrogen is sourced from water electrolysis. The hydrogenation process produces more CO₂ when fossil fuel energy sources are used, but can result in more negative CO₂ emissions with renewable energies. The study reveals that both of the eTL processes can outperform the conventional fossil-fuel-based methanol production process in climate impacts as long as the renewable energy sources are implemented

Advanced solid electrolyte cell for CO2 and H2O electrolysis

A solid electrolyte cell with improved sealing characteristics was examined. A tube cell was designed, developed, fabricated, and tested. Design concepts incorporated in the tube cell to improve its sealing capability included minimizing the number of seals per cell and moving seals to lower temperature regions. The advanced tube cell design consists of one high temperature ceramic cement seal, one high temperature gasket seal, and three low temperature silicone elastomer seals. The two high temperature seals in the tube cell design represent a significant improvement over the ten high temperature precious metal seals required by the electrolyzer drum design. For the tube cell design the solid electrolyte was 8 mole percent yttria stabilized zirconium oxide slip cast into the shape of a tube with electrodes applied on the inside and outside surfaces

Hydrogen Energy For Indian Transport Sector - A Well-To-Wheel Techno-Economic and Environmental Feasibility Analysis

With the alarming rate of growth in vehicle population and travel demand, the energy consumption has increased significantly contributing to the rise of GHG emissions. Therefore, the development of a viable environmentally benign technology/fuel, which minimises both global and local environmental impacts, is the need of the hour. There are four interconnected reasons for propagating a shift towards alternative fuels/technologies : (i) Energy Supply : world oil reserves are rapidly diminishing, (ii) Environment : local pollution from vehicles is creating an atmosphere that is increasingly damaging public health and environment, (iii) Economic competitiveness : the cost of producing oil and regulating the by-products of oil consumption continues to increase, and (iv) Energy security : the military and political costs of maintaining energy security in international markets are becoming untenable. Hydrogen energy has been demonstrated as a viable alternative automotive fuel in three technological modes : internal combustion engines connected mechanically to conventional vehicles; fuel cells that produce electricity to power electric vehicles; and hybrids that involve combinations of engines or fuel cells with electrical storage systems, such as batteries The present study provides a well-to-wheel analysis of the economic and environmental implications of technologies to deliver the hydrogen energy to the vehicles. The main objectives of the study are : (i) prioritization of technologies of hydrogen production, transportation, storage and refueling, (ii) economic analysis of prioritized technology alternatives to estimate the delivered cost of hydrogen at the end-use point, and (iii) estimating the environmental impacts. To achieve the desired objectives, various quantitative life-cycle-cost analyses have been carried out for numerous pathways (i.e. technologies and processes) for hydrogen production, storage, transportation/distribution and dispensing. The total cost implications are arrived at by combining the costs of hydrogen (at end-use point) and the estimated demand for hydrogen for transport. The environmental benefits (potential to abate GHG emissions) of alternative hydrogen energy technology pathways have been worked out by using the standard emission factors. Finally, the GHG emission levels of hydrogen supply pathways are compared with those of diesel and petrol pathways. The application of this systematic methodology will simulate a realistic decision-making process.Hydrogen Energy, Indian Transport Sector, Feasibility Analysis

Survey of hydrogen production and utilization methods. Volume 1: Executive summary

The use of hydrogen as a synthetic fuel is considered. Processes for the production of hydrogen are described along with the present and future industrial uses of hydrogen as a fuel and as a chemical feedstock. Novel and unconventional hydrogen-production techniques are evaluated, with emphasis placed on thermochemical and electrolytic processes. Potential uses for hydrogen as a fuel in industrial and residential applications are identified and reviewed in the context of anticipated U.S. energy supplies and demands. A detailed plan for the period from 1975 to 1980 prepared for research on and development of hydrogen as an energy carrier is included