Thermochemical Water Decomposition Research Articles

An analysis of the economic production and use of green hydrogen

The paper studies technological and economic details of green hydrogen production. Among all hydrogen categories defined by the ratio between production technology and CO2 environmental pollution, for energy applications, only green hydrogen has a future. The same projection can be seen in the transport sector. An analysis of the H2 thermochemical formation technologies showed that ecological hydrogen, called blue hydrogen, can be obtained only by a total separation of hydrogen from CO2, to be recirculated. The thermochemical decomposition of water involves the use of three types of electrolysis cells, of which the solid acid cell (SOEC) is the most economical. Membrane-free water electrolysis is considered as a technology of the future. Production costs are related to storage, compression and distribution. The environmental tax through CO2 emission was also included in the production cost calculation. A numerical application related to the green hydrogen production is also presented, as well as the achievements in field in EU and Romania, along with future perspectives.

Hydrogen production using nuclear power plants

In the coming years, the global demand for hydrogen can be expected to grow gradually, with increasing pressure to produce without the use of natural gas or oil. As a result, possible ways to produce hydrogen that will have a lower carbon footprint are being sought. Apart from the use of renewable energy sources, nuclear energy appears to be another possible source. This article provides an overview of available and suitable technologies that use nuclear energy. These include in particular water electrolysis, thermochemical decomposition of water or hybrid cycles. The article also includes an overview of individual research programs in the world. A nuclear power plant, in conjunction with hydrogen production, could serve as a backup flexible energy source in addition to coal and gas power plants to stabilize fluctuations in the electrical transmission system due to the operation of renewable energy sources.

Engineering of Electrodes and Operating Conditions for Pure-Water-Fed Anion Exchange Membrane Water Electrolyzers

Many industrial processes such as petroleum refining, ammonia production, and metal refining have hydrogen gas as a feedstock. Hydrogen gas can be produced via fossil fuel reforming, photo-electrochemical conversion, thermochemical water decomposition, as well as water electrolysis. Among the various water electrolysis technologies, anion exchange membrane water electrolyzers (AEMWEs) possess possible qualities that will allow for them to out-compete incumbent alkaline electrolyzers and proton exchange membrane electrolyzers PEMWEs). AEMWEs have to possibility to combine platinum group metal–free (PGM-free) catalysts, low-cost cell components and operation at high pressure. It is also desirable for AEMWEs to be operated with a pure water feed, high performance and long life – all of which has been elusive thus far. In this presentation, we will demonstrate device engineering pathways to achieve high performance with pure-water-fed AEMWEs. This was accomplished by optimizing the type and amount of electrocatalyst on both anode and cathode alongside the flow conditions and operating temperature. The optimized pure-water-fed AEMWEs have been successfully operated at steady-state at a voltage below 1.90 V at 1.0 Acm-2 at 80 °C. Differences will be highlighted between DI water and electrolyte-fed systems. The importance of pre-treatment to ensure pure DI-water operation will also be discussed. This work emphasizes the importance of engineering electrodes and operating conditions to reach the highest performance of pure-water-fed AEMWEs, which is expected to allow these devices to out-compete existing water electrolysis technologies.

A super-efficient method for hydrogen production from seawater

A hybrid system to produce hydrogen from the seawater is proposed and the best condition of that to have the highest efficiency is found here. The hybrid system consists of parabolic trough collectors, reverse osmosis (RO) desalination system, and a thermochemical water decomposition unit with heat dissipation system by cooling towers. The main process is based on the cuprous chloride (five-step) cycle that is optimized compared to previous research works. The RO and Cu–Cl processes are simulated by ROZA and Aspen HYSYS software programs, respectively, which are linked to the developed MATLAB codes for other components. The optimum area of the parabolic trough collectors is found 2964.6 m2. Furthermore, the foremost dimensions for two cooling towers are 40 and 20 m height, and 50 and 35 m base diameter, respectively. Additionally, according to the results, the proposed hybrid system enjoys a high level of both energy and exergy efficiency values at the same time. The total energy efficiency of the hybrid H2 production system is 18%, while it has the exergy efficiency of 30%.

Performance Assessment Study on the Na‐O‐H Thermochemical Water Splitting Cycle for Hydrogen Generation

AbstractThe sodium‐oxygen‐hydrogen (Na‐O‐H) thermochemical cycle is investigated, as one of the potential methods of thermochemical water decomposition and hydrogen generation. The hydrogen production reaction, metal separation reaction, and hydrolysis reaction, forming the Na‐O‐H thermochemical cycle, are examined by RGibbs reactor modeling. The parameters for the three reactions are optimized in terms of hydrogen yield, pressure, temperature, and heat requirement. The metal separation reaction is carried out under vacuum pressure, while other reactions can be conducted under atmospheric pressure.

Analysis and assessment of the integrated generation IV gas-cooled fast nuclear reactor and copper-chlorine cycle for hydrogen and electricity production

This paper proposes the conceptual integration of a Generation IV nuclear reactor, the gas-cooled fast nuclear reactor, and the thermo-electrochemical copper-chlorine cycle, a Brayton cycle, and a Rankine cycle for hydrogen and electricity production. This paper analyzes the developed system thermodynamically, and energy and exergy efficiencies are used to measure the system performance. Here, the four-step thermo-electrochemical copper-chlorine cycle produces hydrogen through thermochemical water decomposition, and electricity via the Rankine and Brayton cycles. The produced hydrogen is then compressed to reduce its storage volume. The proposed system uses a heat exchanger network, which is incorporated within the hydrogen producing copper-chlorine cycle. With the heat recovery network, the heat from the nuclear reactor is delivered to only two reactors of the four-step copper-chlorine cycle. The proposed system is modeled and simulated with engineering process simulation software (Aspen Plus). The overall energy and exergy efficiencies of the system are 14.1% and 20.7%, respectively.

Comparative studies of Cu-Cl Thermochemical Water Decomposition Cyles for Hydrogen Production

This research focuses on thermodynamic analysis of the copper chlorine cycles. The cycles were simulated using Aspen Plus software. All thermodynamic data for all the chemical species were defined from literature and the reliability of other compounds in the simulation were ascertained. The 5-step Cu–Cl cycle consist of five steps; hydrolysis, decomposition, electrolysis, drying and hydrogen production. The 4-step cycle combines the hydrolysis and the drying stage of the 5-step cycle to eliminate the intermediate production and handling of copper solids. The 3-step cycle has hydrolysis, electrolysis and hydrogen production stages. Exergy and energy analysis of the cycles were conducted. The results of the exergy analysis were 59.64%, 44.74% and 78.21% while that of the energy analysis were 50%, 49% and 35% for the 5-step cycle, 4-step cycle and 3-step cycle respectively. Parametric studies were conducted and possible exergy efficiency improvement of the cycles were found to be between 59.57-59.67%, 44.32-45.67% and 23.50-82.10% for the 5-step, 4-step and 3-step respectively. The results from the parametric analysis of the simulated process could assist ongoing efforts to understand the thermodynamic losses in the cycle, to improve efficiency, increase the economic viability of the process and to facilitate eventual commercialization of the process.

Analysis and assessment of a hydrogen production plant consisting of coal gasification, thermochemical water decomposition and hydrogen compression systems

A novel hydrogen production plant is proposed, including a thermochemical water decomposition cycle, a pressurized entrained flow gasifier, a water gas shift membrane reactor, a cryogenic air separation unit, a hydrogen-fueled combined cycle for power production and a hydrogen compression system. The syngas produced by the pressurized entrained flow gasifier undergoes the shift reaction in the water gas shift membrane reactor. The stripping of hydrogen is done simultaneously with the shift reaction in the water gas shift membrane reactor to capture more hydrogen and increase the shift reaction conversion percentage. The remaining syngas is combusted in the Brayton cycle and power is produced through Brayton cycle gas turbine. The hot exhausts exiting the Brayton cycle gas turbine goes to the heat recovery steam generation unit where steam is produced. The generated steam goes to the copper-chlorine cycle to produce hydrogen. Part of the power generated by the Brayton cycle is used for the electrolysis reactor in the copper-chlorine cycle. Then, a small part of the hydrogen produced passes to the combined cycle to overcome the needed work rate by the components in the plant. The remaining larger portion of the hydrogen produced goes to the compression system to compress hydrogen to 700 bar for storage. The hydrogen production plant is developed and modeled in the Aspen Plus software package. Energy and exergy analyses are performed on the hydrogen production integrated system. The overall energy and exergy efficiencies of the proposed hydrogen production plant are found to be 51.3% and 47.6% respectively.

Development of an integrated system for electricity and hydrogen production from coal and water utilizing a novel chemical hydrogen storage technology

A coal gasification-based integrated system is proposed to produce electrical power and hydrogen. The hydrogen produced is stored in a chemical storage medium, which is ammonia. The integrated system contains a water gas shift membrane reactor, a hybrid thermochemical water decomposition cycle based on the chemical couple copper and chlorine and a multistage ammonia production system. A hydrogen fueled supporting combined cycle is used to meet the electrical requirement of the integrated system. Coal is gasified, and the resulting syngas is water shifted in a membrane reactor, which produces hydrogen. The remaining syngas is combusted to generate power through a gas turbine, and the turbine hot exhaust is used to provide the required thermal energy of the water decomposition cycle. The hydrogen outputs from the coal gasification and the water decomposition cycle are fed to the ammonia production system and the supporting combined cycle. The ammonia production system contains multiple stages to achieve a high conversion percentage of hydrogen. The nitrogen fed to the ammonia reactor is provided by the cryogenic air separation unit, which also provides oxygen to the gasifier. The proposed system is simulated with the process simulation software Aspen Plus. The system performance is evaluated through energy and exergy efficiencies. The integrated system is found to have an energy efficiency of 48.7% and an exergy efficiency of 48.4%. The system is capable of producing 0.18kg/s of hydrogen and 1.2MW of power per 1.5kg/s of coal.

Assessment and analysis of hydrogen and electricity production from a Generation IV lead-cooled nuclear reactor integrated with a copper-chlorine thermochemical cycle

Summary An integrated system for compressed hydrogen and electrical power production based on a Generation IV nuclear reactor (a lead-cooled reactor) is proposed. The hydrogen is produced by the integrated system through a hybrid thermochemical and electrical water decomposition cycle. The water decomposition cycle is based on copper and chlorine compounds and decomposes water through four main steps. The electrical power is produced by the Rankine cycle, which also contributes to cooling the compressed hydrogen between the compression stages as well as providing the electrical power required by the electrolysis step in the water decomposition cycle. In the proposed system, a heat recovery network is incorporated within the water decomposition cycle so that only the hydrolysis and the oxygen production reactors in the cycle receive thermal energy from the lead-cooled nuclear reactor. The integrated system is modeled and simulated by using engineering process simulation software (Aspen Plus). The performance of the integrated system is assessed with energy and exergy analyses, and the overall energy and exergy efficiencies are found to be 25.4% and 40.6%, respectively. The integrated system produces 3.45 g/s of compressed hydrogen ready for shipping and 467.2 kW of electrical power.

Development and assessment of a new solar heliostat field based system using a thermochemical water decomposition cycle integrated with hydrogen compression

A new hydrogen production plant that produces hydrogen at high pressures is proposed. The proposed plant utilizes an electrical and thermochemical hybrid water decomposition cycle. The source of thermal energy for hydrogen production plant is a heliostat-based solar farm with a generation capacity of 1MWe. The aim of this article is to integrate the thermochemical hybrid water decomposition cycle with the heliostat solar farm and with a hydrogen compression system. The plant electrical energy requirement is covered by the supporting Rankine cycle, which provides the required electrical compression power. The produced hydrogen is compressed to 700bar for usage and storage purposes. The hydrogen production plant is modeled and simulated with Aspen Plus software except for the solar farm, which is developed with engineering equation solver software. Both energy and exergy analyses are performed of the hydrogen production plant, and its overall energy and exergy efficiencies are found to be 12.6% and 20.7% respectively. The energy and exergy efficiencies of the proposed and simulated five-step thermochemical water-decomposition cycle are obtained to be 38.2% and 89.4%, respectively.

Performance analysis of a supercritical water-cooled nuclear reactor integrated with a combined cycle, a Cu-Cl thermochemical cycle and a hydrogen compression system

A novel integration is proposed and analyzed of a thermochemical water decomposition cycle with a supercritical water-cooled nuclear reactor, a combined cycle, and a hydrogen compression system. The supercritical water-cooled reactor in the integrated system has been investigated extensively in Canada. The integrated system uses a compression system to compress the product hydrogen. The hydrogen is produced via a hybrid thermochemical and electrical water decomposition cycle that utilizes the chemical couple of copper and chlorine. The integrated system is modeled and simulated on Aspen Plus, except for the steam circuit, which is simulated on Aspen Hysys. The hydrogen production rate from the proposed system is 3.56kg/s. Both energy and exergy analyses are performed of the integrated system, and its overall energy and exergy efficiencies are, in this regard, found to be 16.9% and 27.8%, respectively.

2-3.UT-3熱化学分解法による水素製造(未来を担う水素エネルギー,Session(2)水素エネルギー)

2-3.UT-3熱化学分解法による水素製造(未来を担う水素エネルギー,Session(2)水素エネルギー)

Chemical process systems analysis using thermodynamic balance equations with entropy generation

Systematic analyses of chemical process systems with steady-state balance equations for Material, Energy and Entropy can yield insights about energy efficiency and property model consistency, with entropy generation being the indicator quantity. Calculations of different sets of independent overall and subsection variables can reveal inefficient locations as well as the impacts of changes in process configuration and conditions. Demonstration is also made of how the analysis tests properties models because values of entropy generation must be positive, and the sum of heat rejections and entropy generations from sections must equal those from an overall analysis. Examples focus on chemical processes with internal circulation of complex mixtures, including thermochemical decomposition of water, and three different carbon-capture processes having essentially the same flue gas feed and gaseous products. Ranking of the CO2 capture processes is made, while negative entropy generation is encountered with some property models.

Development and assessment of a novel integrated nuclear plant for electricity and hydrogen production

A novel nuclear-based integrated system for electrical power and compressed hydrogen production is proposed. The hydrogen is produced through the four-step Cu-Cl cycle for water decomposition. A Rankine cycle is used to generate the power, part of which is used for the electrolysis step in the hybrid thermochemical water decomposition cycle and the hydrogen compression system. In the proposed design of the four-step thermochemical and electrical water decomposition cycle, only the hydrolysis and the oxygen production reactors receive thermal energy from the nuclear reactor. The nuclear thermal energy is delivered to the integrated system in the form of a supercritical fluid. The nuclear reactor, which is based on the supercritical water-cooled reactor, is responsible for delivering the thermal energy to the system, which is simulated using Aspen Plus and assessed with energy and exergy analyses. It is determined that the energy and the exergy efficiencies of the proposed system are 31.6% and 56.2% respectively, and that the integrated system is able to produce 2.02kg/s of highly compressed hydrogen and 553MW of electrical power.

Hydrogen production using high temperature nuclear reactors: Efficiency analysis of a combined cycle

The high temperature nuclear reactor provides a new way to produce hydrogen with high efficiency. In the present work, the feasibility of using a VHTR for both electricity generation and hydrogen production is analyzed. The nuclear reactor is combined with a gas turbine, a steam turbine and a system for the delivery heat for high-, medium- and low-temperature processes. Industrial-scale hydrogen production via thermochemical water decomposition is considered, using high- and medium-temperature processes. Specifically, sulphur-iodine (SI) and copper-chlorine (CuCl) thermochemical cycles are examined. These water splitting cycles permit the conversion of water into hydrogen and oxygen at much lower temperatures than the direct thermal decomposition of water. Both cycles are considered promising routes for continuous, efficient, large-scale and environmentally benign hydrogen production without CO2 emissions. The results show that the combination of a high temperature helium reactor, with a combined cycle for electric power generation and hydrogen production, may reach an efficiency of around 50%. The power plant cycle analyzed in the present paper is complex and it is difficult to determine conditions under which all target objectives are fulfilled: high thermodynamic efficiency for combined production of electricity and high-temperature heat which can be used to produce hydrogen.

Investigation of an integrated hydrogen production system based on nuclear and renewable energy sources: Comparative evaluation of hydrogen production options with a regenerative fuel cell system

Hydrogen has risen as a sustainable and efficient energy carrier option in reducing environmental pollution, and is seen as a potential solution for the current energy crisis. Hydrogen production via water decomposition is a potential process for direct utilization of nuclear thermal energy to increase efficiency and thereby facilitate energy savings. While many of the available renewable energy resources are limited due to their reliability, quality, quantity and density, nuclear energy has the potential to contribute a significant share of energy supply with very limited impacts to climate change. The proposed model in this study is an integrated hydrogen production system combining both nuclear and solar energy sources. This integrated system includes storage of hydrogen and its conversion to electricity by a regenerative fuel cell system when needed. There are many matured water splitting processes that can be linked with the nuclear and solar energy sources to decompose water to its constituents, among which is hydrogen. In this regard, a comparative study is carried out to evaluate an optimal and feasible hydrogen production/storage process with a regenerative fuel cell that can be linked to this integrated system. Studies conducted here on hydrogen production processes show the thermochemical water decomposition to be the better option for producing hydrogen, comparing to electrolysis, due to its high efficiencies and low costs. Energy and exergy efficiencies of various hydrogen production processes, and fuel cell systems are evaluated and compared. Also, a parametric study is conducted on these efficiencies to see the effect of various operating conditions.

水の熱化学分解

水の熱化学分解

Process simulation and analysis of a five-step copper-chlorine thermochemical water decomposition cycle for sustainable hydrogen production

SUMMARY A process model of a five-step copper–chlorine (Cu–Cl) cycle is developed and simulated with the Aspen Plus simulation code. Energy and mass balances, stream flows and properties, heat exchanger duties, and shaft work are determined. The primary reactions of the five-step Cu–Cl cycle are assessed in terms of varying operating and design parameters. A sensitivity analysis is performed to examine the effect of parameter variations on other variables, in part to assist optimization efforts. For each cycle step, reaction heat variations with such parameters as process temperature are described quantitatively. The energy efficiency of the five-step Cu–Cl thermochemical cycle is found to be 44% on the basis of the lower heating value of hydrogen, and a parametric study of potential efficiency improvement measures is presented. Copyright © 2014 John Wiley & Sons, Ltd.

Shadow imaging of particle dynamics and dissolution rates in aqueous solutions for hydrogen production

This paper presents experimental studies of particle dynamics, dissolution and transport processes for hydrogen production and thermochemical water decomposition. The processes involve multiple steps, some consisting of multiphase reaction systems. It examines the importance of design optimization of gas–solid–liquid phase systems and process integration of a thermochemical copper–chlorine cycle for hydrogen production. The dissolution of copper (I) chloride particle in hydrochloric acid is examined. This dissolution step is investigated in order to provide a predictive modeling method for more complex multiphase reacting systems.