High Temperature Steam Electrolysis Process Research Articles

Technoeconomic assessment of hydrogen cogeneration via high temperature steam electrolysis with a light-water reactor

Increased electricity production from renewable energy resources, coupled with low natural gas (NG) prices, has caused existing light-water reactors (LWRs) to experience diminishing returns from the electricity market. This reduction in revenue is forcing LWRs to consider alternative revenue streams, such as introduction hydrogen production or desalination, to remain profitable. This paper performs a technoeconomic assessment (TEA) regarding the viability of retrofitting existing pressurized-water reactors (PWRs) to produce green hydrogen (H2) via high-temperature steam electrolysis (HTSE). Such an integration would allow nuclear facilities to expand into additional markets that may be more profitable in the long term and eliminate CO2 emissions from the hydrogen production process. To accommodate such an integration, a detailed single market levelized cost of hydrogen (LCOH) and multimarket analyses were conducted of HTSE process operation, requirements, costing, and flexibility. Alongside this costing analysis, market analyses were conducted on the electric and hydrogen markets in the PJM interconnect.Utilizing a novel stochastic, dispatch optimization approach results suggest that a positive gain is achievable, and by operating in multiple markets, the nuclear facility can avoid the sale of electricity during times of low electricity market pricing, while maintaining the ability to capitalize on the high electricity market pricing. It should be noted that the analysis conducted is a differential cash flow analysis and, as such, does not present profit levels. LCOH analysis results demonstrate the potential exists to produce hydrogen at a cost as low as $1.20/kg. This price is lower than traditional steam methane reforming (SMR) allowing nuclear based hydrogen production to disrupt the existing hydrogen production market.

Net energy and carbon footprint analysis of solar hydrogen production from the high-temperature electrolysis process

This paper assesses the viability of the solar-based high-temperature steam electrolysis (HTSE) process by estimating the cumulative energy demand (CED) and carbon emission footprint (CEF) of hydrogen. In the analysis, photovoltaic (PV) and concentrated solar power (CSP) plants are considered as the source of electricity. The trend of variation in CED and CEF with the changing temperature and current density of the solid oxide electrolyzer is obtained. The requirements for the feasibility of the HTSE process is established by comparing the results with the solar-based alkaline electrolysis process. Monte Carlo simulation is done to capture the effects of data and performance uncertainties. The carbon footprint of the solar-based high-temperature and alkaline electrolysis processes are also compared with the renewable, nuclear and hydrocarbon-based routes for hydrogen production. The CED of the PV and CSP based HTSE processes are 15.1–28 MJ/kg of hydrogen and 18.8–30.1 MJ/kg, respectively. This implies a net energy gain of 90–104 MJ/kg of hydrogen. The carbon footprint of the PV and CSP driven processes are 1.03–1.87 kg CO2/kg of hydrogen and 1.05–1.67 kg/kg, respectively. The carbon footprint of the steam methane reforming (SMR) process, solar-based alkaline electrolysis, and thermochemical cycles are 10.6 kg/kg, 2–2.3 kg/kg and 4.3–4.5 kg/kg respectively. Thus, the solar-HTSE process is a sustainable alternative not only to the SMR route but also to other solar technologies like alkaline electrolysis and thermochemical cycles. It is recommended that the solar-HTSE route should be further explored by demonstrating the technology on a pilot scale.

Dynamic performance analysis of a high-temperature steam electrolysis plant integrated within nuclear-renewable hybrid energy systems

A high-temperature steam electrolysis (HTSE) plant is proposed as a flexible load resource to be integrated with a light water reactor (LWR) in nuclear-renewable hybrid energy systems (N-R HESs). This integrated energy system is capable of dynamically apportioning electrical and thermal energy on an industrial scale to meet both grid demand and energy needs in the HTSE plant without generating greenhouse gases. A dynamic performance analysis of such a system is carried out to evaluate its technical feasibility and benefits, and safety operating under highly variable conditions requiring flexible output. To support the dynamic analysis, special emphasis is given here to the modeling and control design of the HTSE process, which employs planar solid oxide electrolysis cells, coupled to an LWR. The proposed model includes practical constraints, such as operating limits of equipment, and allows the simulation of transient response of the LWR/HTSE integration case with high penetration of renewable resources. Simulation results involving several case studies show that the HTSE integrated N-R HESs could lead to efficient utilization of clean energy generation sources at levels that maximize profits, i.e., steady-state operation of a nuclear reactor and high penetration of solar or wind energy without curtailment, by providing dispatchable electricity to the grid and producing alternative value-added products (hydrogen and oxygen). The results also indicate that the system can provide various types of ancillary services (i.e., regulation, operating reserves, and load following) to support grid stability while satisfying its operating constraints and control objectives; thus, it is capable of effectively and economically mitigating the increasing levels of dynamic variability and uncertainty introduced by renewables.

Economic assessment of hydrogen production from solar driven high-temperature steam electrolysis process

Abstract A key prerequisite for the hydrogen economy is cost-effective renewable hydrogen supply. This paper provides a framework for the thermodynamic and economic assessment of solar hydrogen production from the high-temperature steam electrolysis (HTSE) route. A system configuration for the solar-driven steam electrolysis plant is proposed. The thermodynamic and economic analysis is done for varying temperature and current density conditions of the solid oxide electrolyzer powered by concentrated solar (CSP) and photovoltaic (PV) power plants. Based on the expected reductions in the cost of plant components, the levelized cost of hydrogen (LCOH2) for the 2030 scenario is evaluated. Conditions for the viability of this route are checked by comparing the results with the polymer electrolyte membrane electrolysis (PEME) process. The optimum energy efficiency of a PV driven process increases from 9.1% at 873 K, 1500 A/m2 to 12.1% at 1273 K, 8000 A/m2. For the electrolyzer operating at 873 K, the optimum LCOH2 of 22 $/kg is obtained at 6000 A/m2. For the electrolyzer temperature of 1073 K, LCOH2 drops from 16 $/kg at 5000 A/m2 to 12.1 $/kg at 10000 A/m2. When compared to PEME, this route becomes viable beyond 973 K, 6000 A/m2 for PV and 923 K, 3000 A/m2 for CSP driven processes. With the current state of economics, this process is not competitive with the industrial steam methane reforming route. However, the cost target of 6–8 $/kg is achievable if the component costs reduce to 2030 level. Thus, the process has potential to be commercially viable and should be pursued further by creating prototype and pilot scale demonstrations.

Exergy analyses of green hydrogen production methods from biogas-based electricity and sewage sludge

In this study, five models are considered for the use of biogas-based electricity and sewage sludge obtained from a municipal wastewater treatment plant for green hydrogen production. These models include alkaline, PEM, high temperature water electrolysis, alkaline hydrogen sulfide electrolysis and dark fermentation biohydrogen production processes. Energy and exergy analyses are performed on these models by applying thermodynamic procedures and the results are compared. The daily hydrogen production rates of the models are found as 594, 625.4, 868.6, 10.8 and 56.74 kg and the exergetic efficiencies of the models are calculated as 19.81, 20.66, 25.83, 24.86 and 60.54%, respectively. In terms of the exergetic efficiency, the dark fermentation biohydrogen production process is found to be superior to the other models, followed by the high temperature steam electrolysis process. This paper aims to determine the most appropriate model for a wastewater treatment plant among the considered models in terms of exergy efficiency.

Progress of the IAHE Nuclear Hydrogen Division on international hydrogen production programs

This paper presents recent activities of the IAHE Nuclear Hydrogen Division and associated research advances in Canada, China, France, Germany, Poland, and Romania on programs and major initiatives on large-scale hydrogen production and utilization. Germany and France have made significant advances in high temperature steam electrolysis (HTSE). Germany is going to demonstrate a 3-kW steam electrolyzer and 100-kW Hybrid Sulfur Cycle powered by solar energy soon. France operated several HTSE 25-cell stacks at various operating points. Recently, a HTSE packaged system has been built, containing this 25-cell stack and other Balance of Plant components. At 700 °C, this system produces 1.2 Nm3/h of H2 with a total electrical consumption of 3.9 kWh/Nm3, achieving 92% of efficiency (electrical consumption of the system vs HHV of the produced hydrogen). It demonstrates that a 150 °C heat source temperature is sufficient for the steam generation, and that a slightly exothermic operating mode of the stack is sufficient to preheat the inlet gas up to 700 °C and compensate the heat losses of the system. China has also made significant progress in developing the HTSE process at a hydrogen production rate of 105 dm3/h and the thermochemical Sulfur–Iodine (SI) cycle at the rate of 60 dm3/h, which already achieved the goal of China's HTR-PM Demonstration Nuclear Power Plant Project. The components and facilities were developed and tested in Tsinghua University. Romania is collaborating with Canada on nuclear hydrogen production with the thermochemical Cu–Cl cycle. The individual unit operations of the Cu–Cl cycle have been verified experimentally. Research on integration of a laboratory scale system to produce 3 kg of hydrogen per day is underway at the University of Ontario Institute of Technology in Oshawa, Ontario. Poland has developed advanced simulation capabilities for Solid Oxide Fuel/Electrolysis Cells for hydrogen peak energy storage as well as laboratory scale experiments focused on solid oxide and molten carbonate fuel cells. This paper presents a review of activities of members of the IAHE Nuclear Hydrogen Division in these six countries.

Solar power tower as heat and electricity source for a solid oxide electrolyzer: a case study

High-temperature steam electrolysis (HTSE) consists of the splitting of steam into hydrogen and oxygen at high temperature in solid oxide electrolyzers. Performing the electrolysis process at high temperatures offers the advantage of achieving higher efficiencies as compared to the conventional water electrolysis. Furthermore, this allows the direct use of process heat to generate steam. This paper is related to the FCH JU (Fuel Cells and Hydrogen Joint Undertaking) project ADEL (ADvanced ELectrolyser For hydrogen Production with Renewable Energy Sources), which investigates different carbon-free energy sources to be coupled to the HTSE process. Renewable energy sources are able to provide the high-temperature steam electrolysis (HTSE) process with heat and power. This paper investigates the capability of Concentrating Solar Power (CSP) technologies to provide the HTSE process with the necessary energy demand. The layout of the plant is shown in the following figure. The design of commercial-scale high-temperature steam electrolysis has been carried out. The HTSE plant is coupled to an air cooled solar tower. The configuration and the operating parameters of the solar tower are based on those of the solar tower of Jülich (Germany), which is operated by DLR. This paper presents the results of process analysis performed to evaluate the hydrogen production from a HTSE plant coupled to an 80MWth air solar tower. Additionally, the dynamic behavior of the system during energy fluctuations has been analyzed. The receiver-to-hydrogen efficiency (based on the Higher Heating Value of hydrogen) is 26% at a hydrogen production rate of 680 kg/h in steady-state operation. The overall solar-to-hydrogen efficiency is calculated to be at 18%. Moreover, the analysis under transient conditions shows that a steady-state operation of the plant is only possible for 8 h. Copyright © 2015 John Wiley & Sons, Ltd.

Hydrogen Co-Production From Subcritical Water-Cooled Nuclear Power Plants In Canada

Subcritical water-cooled nuclear reactors (Sub-WCR) operate in several countries including Canada providing electricity to the civilian population. The high-temperature-steam-electrolysis process (HTSEP) is a feasible and laboratory-demonstrated large-scale hydrogen-production process. The thermal and electrical integration of the HTSEP with Sub-WCR-based nuclear-power plants (NPPs) is compared for best integration point, HTSEP operating condition and hydrogen production rate based on thermal energy efficiency. Analysis on integrated thermal efficiency suggests that the Sub-WCR NPP is ideal for hydrogen co-production with a combined efficiency of 36%. HTSEP operation analysis suggests that higher product hydrogen pressure reduces hydrogen and integrated efficiencies. The best integration point for the HTSEP with Sub-WCR NPP is upstream of the high-pressure turbine.

Simulation of a syngas from a coal production plant coupled to a high temperature nuclear reactor

In light of the rapid depletion of the world’s oil reserves, concerns about energy security prompted the exploration of alternative sources of liquid fuels for transportation. One such alternative is the production of synthetic fuel using an indirect coal liquefaction process or coal-to-liquids (CTL) process. In this process, coal is gasified in a gasifier in the presence of steam and oxygen to produce a synthesis gas or syngas consisting mainly of hydrogen and carbon monoxide. The syngas is then converted to liquid fuels and a variety of useful chemicals in a Fischer Tropsch-type synthesis reactor. However, the traditional process for syngas production also produces substantial amounts of carbon dioxide. In fact, only about one third of the carbon in the coal feedstock ends up in the liquid fuel product using traditional CTL technology. If more hydrogen was available than the hydrogen produced during the gasification step, the carbon utilisation of the process could be improved significantly. The high temperature reactor (HTR) is a gas cooled Generation IV nuclear reactor ideally suited to provide power and high temperature heat for carbon neutral production of hydrogen via high temperature electrolysis. The integration of an HTR into a CTL process therefore provides an opportunity to improve the thermal and carbon efficiency of the CTL process significantly. This paper presents a possible process flow scheme for a nuclear assisted CTL process. The system is evaluated in terms of its thermal or syngas production efficiency (defined as the ratio of the heating value of the produced syngas to the sum of the heating value of the coal plus the HTR heat input) as well as its carbon utilisation. If the hydrogen production plant is sized to produce only enough associated oxygen to supply the needs of the gasification plant, syngas is produced at about 63% thermal efficiency, while 71.5% of the carbon is utilised in this process. It was found that the optimum HTR outlet temperature to produce hydrogen with a high temperature steam electrolysis process is 850°C. If enough process heat and power are available and process equipment capacities are sufficient, the carbon utilisation of the process could be improved even further to values in excess of 90%.

Characteristics of the Hydrogen Electrode in High Temperature Steam Electrolysis Process

YSZ-electrolyte supported solid oxide electrolyzer cells (SOECs) using LSM-YSZ oxygen electrode but with three types of hydrogen electrode, Ni–SDC, Ni–YSZ and LSCM–YSZ have been fabricated and characterized under different steam contents in the feeding gas at 850°C. Electrochemical impedance spectra results show that cell resistances increase with the increase in steam concentrations under both open circuit voltage and electrolysis conditions, suggesting that electrolysis reaction becomes more difficult in high steam content. Pt reference electrode was applied to evaluate the contributions of the hydrogen electrode and oxygen electrode in the electrolysis process. Electrochemical impedance spectra and over potential of both electrodes were measured under the same testing conditions. Experimental results show that steam contents mainly affect the behavior of the hydrogen electrode but have little influence on the oxygen electrode. Further, contribution from the hydrogen electrode is dominant in the electrolysis process for Ni–based SOECs, but this contribution decreases for LSCM–based SOECs.

Economics of hydrogen production and liquefaction by geothermal energy

Seven models are considered for the production and liquefaction of hydrogen by geothermal energy. In these models, we use electrolysis and high-temperature steam electrolysis processes for hydrogen production, a binary power plant for geothermal power production, and a pre-cooled Linde–Hampson cycle for hydrogen liquefaction. Also, an absorption cooling system is used for the pre-cooling of hydrogen before the liquefaction process. A methodology is developed for the economic analysis of the models. It is estimated that the cost of hydrogen production and liquefaction ranges between 0.979 $/kg H2 and 2.615 $/kg H2 depending on the model. The effect of geothermal water temperature on the cost of hydrogen production and liquefaction is investigated. The results show that the cost of hydrogen production and liquefaction decreases as the geothermal water temperature increases. Also, capital costs for the models involving hydrogen liquefaction are greater than those for the models involving hydrogen production only.

Status and research of highly efficient hydrogen production through high temperature steam electrolysis at INET

Hydrogen generation through high temperature steam electrolysis (HTSE) using solid oxide electrolysis cells (SOEC) has recently received increasingly international interest in the large-scale, highly efficient nuclear hydrogen production field. The research and development of HTSE technology was initiated in INET of Tsinghua University from 2005 as one of the approaches in National Key Special Projects for HTGR which aims at promoting highly efficient and sustainable application of nuclear process heat in the future. In the past three years, the research team mainly focused on preliminary investigation, feasibility study, equipment development and fundamental research. Currently, two bench-scale equipments for the study of HTSE process and SOEC components have been designed and constructed. In addition, the research group made rapid progress in the development of novel anode materials, effective microstructure control of cathodes and theoretically quantitative analysis of hydrogen production efficiency through HTSE coupled with HTGR.

Development of the Pure Hydrogen Production Process from Reductive Gas by Using the Solid Oxide Electrolysis Cells

Our research and development aims to develop an efficient process technology for high-purity hydrogen production with simple system component by using various reductive gases especially by using low calorie gases such as biogas. This process is a high temperature steam electrolysis process using solid oxide electrolysis cells with reductive gas supplied into the anode of the cells. For developing the high performance electrolysis cells, tubular electrolysis cells with thin electrolyte of yttria stabilized zirconia(YSZ) were fabricated. The performance of the electrolysis cell was evaluated by an electrolysis test for single cell using a simulated gas, determining that electrolysis could be achieved at lower voltage than 0.4V with a current density of 320mA/cm2 at 730 degree C. Then, a cell stack of 7 tubular electrolysis cells connected in series was fabricated and the low voltage electrolysis with the cell stack and the hydrogen production from the biogas were successfully demonstrated.

Two-dimensional simulation and critical efficiency analysis of high-temperature steam electrolysis system for hydrogen production

High-temperature steam electrolysis (HTSE) is a promising method for highly efficient large-scale hydrogen production. The HTSE process not only reduces the amount of thermodynamic electrical energy requirement but also decreases the polarization losses, which improves the overall efficiency of hydrogen production. In this paper, a two-dimensional simulation method of the efficiency of the HTSE system integrated with high-temperature gas-cooled nuclear reactor (HTGR), which changes two parameters simultaneously in a reasonable range while keeping one parameter constant, was presented. Compared with one-dimensional analysis method, the effects of electrical efficiency ( η el), electrolysis efficiency ( η es,), and thermal efficiency ( η th) on overall efficiency ( η overall) were investigated more objectively and accurately. Moreover, the critical concepts of η es and η th were put forward originally, which were very important to determine the optimum electrolysis voltages and operation temperatures in the actual HTSE processes. The calculated critical value of η es was Δ G( T)/Δ H( T) and the actual η es should be higher than the theoretically calculated one in order to maintain the high hydrogen production efficiency of HTSE system. Also, it was very interesting to find that the critical η es was the theoretical maximum efficiency in SOFC mode. Furthermore, the critical value of η th was equal to the value of η el, which means the overall efficiency decreases with the η es increasing if the η th in the actual HTSE process is less than the critical value of η th. Therefore, it is very important to control the η th higher than the critical value in the actual HTSE process to get high overall system efficiency.

The feasibility of using geothermal energy in hydrogen production

A feasibility study exploring the use of geothermal energy in hydrogen production is presented. It is possible to use a thermal energy to supply heat for high temperature electrolysis and thereby substitute a part of the relatively expensive electricity needed. A newly developed HOT ELLY high temperature steam electrolysis process operates at 800 – 1000°C. Geothermal fluid is used to heat fresh water up to 200°C steam. The steam is further heated to 900°C by utilising heat produced within the electrolyser. The electrical power of this process is reduced from 4.6 kWh per normalised cubic meter of hydrogen (kWh/Nm 3 H 2) for conventional process to 3.2 kWh/Nm 3 H 2 for the HOT ELLY process implying electrical energy reduction of 29.5%. The geothermal energy needed in the process is 0.5 kWh/Nm 3 H 2. Price of geothermal energy is approximately 8–10% of electrical energy and therefore a substantial reduction of production cost of hydrogen can be achieved this way. It will be shown that using HOT ELLY process with geothermal steam at 200°C reduces the production cost by approximately 19%.