Overview of hydrogen production research in the Clean Energy Research Laboratory (CERL) at UOIT

This paper discusses new hydrogen production methods that have been actively investigated both theoretically and experimentally at UOIT and some recent findings through experimental measurements and analysis. A major cluster of activities at UOIT has developed novel hydrogen production systems from electrolysis to thermochemical cycles and from integrated cycles to solar-light based hydrogen production processes. The results confirm that both thermochemical cycles and photochemical processes offer promising potential for sustainable hydrogen production.     

Performance assessment of solar-driven integrated Mg–Cl cycle for hydrogen production

The present study develops a new solar energy system integrated with a Mg–Cl thermochemical cycle for hydrogen production and analyzes it both energetically and exergetically for efficiency assessment. The solar based integrated Mg–Cl cycle system considered here consists of five subsystems, such as: (i) heliostat field subsystem, (ii) central receiver subsystem, (iii) steam generation subsystem, (iv) conventional power cycle subsystem and (v) Mg–Cl subsystem. Also, the inlet and outlet energy and exergy rates of all of subsystems are calculated and illustrated accordingly. We also undertake a parametric study to investigate how the overall system performance is affected by the reference environment temperature and operating conditions. As a result, the overall energy and exergy efficiencies of the considered system are found to be 18.18% and 19.15%, respectively. The results show that the Mg–Cl cycle has good potential and attractive overall cycle efficiencies over 50%.     

Canadian advances in the copper–chlorine thermochemical cycle for clean hydrogen production: A focus on electrolysis

Hydrogen is a clean energy carrier that can help mitigate greenhouse gas (GHG) emissions if it is used to replace fossil fuels for power production. One way to produce hydrogen on a large scale is through the use of water splitting thermochemical cycles such as the hybrid copper chlorine (Cu–Cl) cycle. Canadian Nuclear Laboratories Ltd. (CNL) chose to develop the Cu–Cl cycle because the highest temperature required by this cycle is about 530 °C, compatible with the Canadian Super Critical Water Reactor (SCWR) or some small modular reactors (SMR). The on-going effort at CNL is to demonstrate a fully integrated Cu–Cl cycle at laboratory scale with a hydrogen production rate of 50 L/h. Some recent experimental results of the electrolysis step, one of the main steps of the cycle, are discussed in this paper.The anode reaction of CuCl oxidation was investigated using a three-electrode electrochemical cell. Half-cell experiments found that CuCl oxidation did not require noble metals as catalyst. The CuCl oxidation on carbon was found to be a mass-transfer controlled process. Hence the limiting current density increased with increasing turbulence on the electrode surface. Increasing the CuCl concentration and the solution temperature also resulted in higher limiting current densities. A current density of 0.53 A/cm² was achieved for a 1.0 M CuCl solution at 80 °C.Single cells with electrode areas up to 100 cm² were used to establish the operating conditions for the electrolysis step. The effects of flow rate, temperature, and current density on the cell voltage were studied. A hydrogen production rate of 50 L/h was successfully achieved at 0.4 A/cm² in a 2.0 M CuCl solution at 80 °C. The electrolysis step is fully developed for integration in a laboratory-scale demonstration of the Cu–Cl cycle.     

Energy and exergy analyses of a solar based hydrogen production and compression system

In this study, a solar thermal based integrated system with a supercritical-CO₂ (sCO₂) gas turbine (GT) cycle, a four-step Mg–Cl cycle and a five-stage hydrogen compression plant is developed, proposed for applications and analyzed thermodynamically. The solar data for the considered solar plant are taken for Greater Toronto Area (GTA) by considering both daily and yearly data. A molten salt storage is considered for the system in order to work without interruption when the sun is out. The power and heat from the solar and sCO₂-GT subsystems are introduced to the Mg–Cl cycle to produce hydrogen at four consecutive steps. After the internal heat recovery is accomplished, the heating process at required temperature level is supplied by the heat exchanger of the solar plant. The hydrogen produced from the Mg–Cl cycle is compressed up to 700 bar by using a five-stage compression with intercooling and required compression power is compensated by the sCO₂-GT cycle. The total energy and exergy inputs to the integrated system are found to be 1535 MW and 1454 MW, respectively, for a 1 kmol/s hydrogen producing plant. Both energy and exergy efficiencies of the overall system are calculated as 16.31% and 17.6%, respectively. When the energy and exergy loads of the receiver are taken into account as the main inputs, energy and exergy efficiencies become 25.1%, and 39.8%, respectively. The total exergy destruction within the system is found to be 1265 MW where the solar field contains almost 64% of the total irreversibility with a value of ～811 MW.     

Exergoeconomic machine-learning method of integrating a thermochemical Cu–Cl cycle in a multigeneration combined cycle gas turbine for hydrogen production

Integrating new technologies into existing thermal energy systems enables multigenerational production of energy sources with high efficiency. The advantages of multigenerational energy production are reflected in the rapid responsiveness of the adaptation of energy source production to current market conditions. To further increase the useful efficiency of multigeneration energy sources production, we developed an exergoeconomic machine-learning model of the integration of the hydrogen thermochemical Cu–Cl cycle into an existing gas-steam power plant. The hydrogen produced will be stored in tanks and consumed when the market price is favourable. The results of the exergoeconomic machine-learning model show that the production and use of hydrogen, in combination with fuel cells, are expedient for the provision of tertiary services in the electricity system. In the event of a breakdown of the electricity system, hydrogen and fuel cells could be used to produce electricity for use by the thermal power plant. The advantages of own or independent production of electricity are primarily reflected in the start-up of a gas-steam power plant, as it is not possible to start a gas turbine without external electricity. The exergy analysis is also in favour of this, as the integration of the hydrogen thermochemical Cu–Cl cycle into the existing gas-steam power plant increases the exergy efficiency of the process.     

Evaluation and comparison of hydrogen production potential of the LIFE fusion reactor by using copper–chlorine (Cu–Cl), cobalt–chlorine (Co–Cl) and sulfur–iodine (S–I) cycles

In this paper, the hydrogen production and neutronic analysis of the Laser Inertial Confinement Fusion-Fission Engine (LIFE) fusion reactor have been analyzed. The potential of hydrogen production from unit integrated of the reactor with three different hydrogen production methods which has copper-chlorine (Cu–Cl) cycle, cobalt-chlorine (Co–Cl) cycle and sulfur-iodine (S–I) cycle have been investigated. Neutronic performance analysis for various parameters was calculated statically by using Monte Carlo N-Particle Nuclear Code and determined optimum reactor operation conditions. The hydrogen production potential for all conditions was investigated as statically. And also, the production potential with determining optimum conditions was performed over operation plant. Tristructural isotropic (TRISO) coated thorium carbide (ThC) was used as fuel of LIFE fusion reactor. Natural lithium and FLiNaBe (LiF + NaF + BeF₂) were used first and second coolant, respectively. In the statistical analysis, effects of ThC fuel ratio, 1st and 2nd coolant zone thicknesses were examined. As a consequence of the neutronic analysis, tritium breeding values and energy multiplication values (M) was attained and according to M values, hydrogen production amount, required thermal power and thermal power ratios were acquired. Among the used hydrogen production methods, Cu–Cl cycle produced the highest hydrogen amount, while the Co–Cl cycle has the lowest H₂ amount. At the end of the reactor operation time for determining optimum conditions, the produced hydrogen amounts are 9.00, 4.80 and 7.36 kg/s for Cu–Cl, Co–Cl and S–I cycles, respectively.     

Energy and exergy analyses of magnesium-chlorine (Mg-Cl) thermochemical cycle

In this paper, we conduct energy and exergy analyses of the magnesium-chlorine (Mg-Cl) thermochemical cycle for hydrogen production and examine the respective cycle energy and exergy efficiencies. We also undertake a parametric study to investigate how the overall cycle performance is affected by changing the reference environment temperature and operating conditions. The results show that Mg-Cl cycle offers a good potential due to its high energy and exergy efficiencies as 63.63% and 34.86%, respectively, based upon the conditions and parameters considered. In this regard, Mg-Cl cycle appears to be a promising low temperature thermochemical cycle. It may, therefore, compete with other low temperature thermochemical and hybrid cycles such as the copper–chlorine cycle.     

Energy and exergy analyses and optimization study of an integrated solar heliostat field system for hydrogen production

In this paper, we propose an integrated system, consisting of a heliostat field, a steam cycle, an organic Rankine cycle (ORC) and an electrolyzer for hydrogen production. Some parameters, such as the heliostat field area and the solar flux are varied to investigate their effect on the power output, the rate of hydrogen produced, and energy and exergy efficiencies of the individual systems and the overall system. An optimization study using direct search method is also carried out to obtain the highest energy and exergy efficiencies and rate of hydrogen produced by choosing several independent variables. The results show that the power and rate of hydrogen produced increase with increase in the heliostat field area and the solar flux. The rate of hydrogen produced increases from 0.006 kg/s to 0.063 kg/s with increase in the heliostat field area from 8000 m² to 50,000 m². Moreover, when the solar flux is increased from 400 W/m² to 1200 W/m², the rate of hydrogen produced increases from 0.005 kg/s to 0.018 kg/s. The optimization study yields maximum energy and exergy efficiencies and the rate of hydrogen produced of 18.74%, 39.55% and 1571 L/s, respectively.     

Energy and exergy analyses of integrated hybrid sulfur isobutane system for hydrogen production

This paper analyzes an integrated HyS cycle (hybrid sulfur cycle), isobutane cycle and electrolyzer for hydrogen production. The operating parameters such as concentration, pressure and temperature are varied to investigate their effects on the energy and exergy efficiencies of the system with/without heat recovery and integration, as well as the decomposer and rate of hydrogen produced. A new heat exchanger network is also developed to recover heat within the HyS cycle in the most efficient manner. The exergy destruction rate in each component is analyzed and discussed. From the results, increasing the pressure is beneficial up to 3222 kPa, after which the performance remains constant. The exergy efficiency varies more significantly with operating parameters than the energy efficiency. The maximum exergy destruction occurs in the heat exchanger so this component should be the focus to enhance the overall performance of the system.     

Thermodynamic viability of a new three step high temperature Cu-Cl cycle for hydrogen production

A new three step high temperature Cu-Cl thermochemical cycle for hydrogen production is presented. The performance of the proposed cycle is investigated through energy and exergy approaches. Furthermore, the effects of various parameters, such as the temperatures of the steps of the cycle and power plant efficiency, on various energy and exergy efficiencies are assessed with parametric studies. The results show that the exergy and energy efficiencies of the proposed cycle are 68.3% and 32.0%, respectively. In addition, the exergy analysis results reveal that the hydrogen production step has the maximum specific exergy destruction with a value of 150.9 kJ/mol. The results suggest that proposed cycle may provide enhanced options for high temperature thermochemical cycles by improving thermal management without causing a sudden temperature jump/fall between the hydrogen production step and other steps.     

Exergy analysis of Cobalt–Chlorine thermochemical hydrogen production cycle: A kinetic approach

Increasing energy needs and reducing greenhouse gas emissions require immediate studies on carbon-free energy solutions, namely hydrogen. There are numerous methods among the production methods of hydrogen in a green manner. Hydrogen, which is then primarily obtained as a result of the separation of water with thermochemical cycles, is an environmentally friendly and sustainable hydrogen production method. In this study, the Cobalt–Chlorine (Co–Cl) cycle, which is one of the new thermochemical cycles, is examined in detail in terms of thermodynamics. There are four reactions in the Co–Cl thermochemical cycle. These are listed as the hydrolysis reaction in which hydrogen is obtained, the thermolysis reaction in which oxygen is obtained, the reduction reaction and finally the hydrochlorination reaction. According to the results of the analysis performed kinetically with the Aspen Plus software, the exergy efficiency of the cycle is calculated as 33%. When the exergy destruction of all reactions is compared, it is seen that the greatest exergy destruction occurs in the hydrolysis reaction, and the lowest exergy destruction occurs in the hydrochlorination reaction. The fact that the exergy efficiency is high when evaluated in terms of kinetics shows that the cycle is feasible in terms of thermodynamics. In addition, the costs of the cycle are to be considered in the future studies as it is an important criterion.     

Development and assessment of a solar,wind and hydrogen hybrid trigeneration system

A solar-wind hybrid trigeneration system is proposed and analyzed thermodynamically through energy and exergy approaches in this paper. Hydrogen, electricity and heat are the useful products generated by the hybrid system. The system consists of a solar heliostat field, a wind turbine and a thermochemical copper-chlorine (Cu-Cl) cycle for hydrogen production linked with a hydrogen compression system. A solar heliostat field is employed as a source of thermal energy while the wind turbine is used to generate electricity. Electric power harvested by the wind turbine is supplied to the electrolyzer and compressors and provides an additional excess of electricity. Hydrogen produced by the thermochemical copper-chlorine (Cu-Cl) cycle is compressed in a hydrogen compression system for storage purposes. Both Aspen Plus 9.0 and EES are employed as software tools for the system modeling and simulation. The system is designed to achieve high hydrogen production rate of 455.1 kg/h. The overall energy and exergy efficiencies of the hybrid system are 49% and 48.2%, respectively. Some additional results about the system performance are obtained, presented and discussed in the paper.     

Advances in hydrogen production by thermochemical water decomposition: A review

Hydrogen demand as an energy currency is anticipated to rise significantly in the future, with the emergence of a hydrogen economy. Hydrogen production is a key component of a hydrogen economy. Several production processes are commercially available, while others are under development including thermochemical water decomposition, which has numerous advantages over other hydrogen production processes. Recent advances in hydrogen production by thermochemical water decomposition are reviewed here. Hydrogen production from non-fossil energy sources such as nuclear and solar is emphasized, as are efforts to lower the temperatures required in thermochemical cycles so as to expand the range of potential heat supplies. Limiting efficiencies are explained and the need to apply exergy analysis is illustrated. The copper–chlorine thermochemical cycle is considered as a case study. It is concluded that developments of improved processes for hydrogen production via thermochemical water decomposition are likely to continue, thermochemical hydrogen production using such non-fossil energy will likely become commercial, and improved efficiencies are expected to be obtained with advanced methodologies like exergy analysis. Although numerous advances have been made on sulphur–iodine cycles, the copper–chlorine cycle has significant potential due to its requirement for process heat at lower temperatures than most other thermochemical processes.