Synergistic roles of off-peak electrolysis and thermochemical production of hydrogen from nuclear energy in Canada

Hydrogen as a clean energy carrier is frequently identified as a major solution to the environmental problem of greenhouse gases, resulting from worldwide dependence on fossil fuels. However, most of the world's hydrogen (about 96%) is currently produced from fossil fuels, which does not address the issue of greenhouse gases. Although there is a large motivation of the “hydrogen economy”, for improvement of urban air quality, energy security, and integration of intermittent renewable energy sources, CO₂ free energy sources are critical to hydrogen becoming a significant energy carrier. Two technologies, applied in tandem, have a promising potential to generate hydrogen without leading to greenhouse gas emissions: 1) electrolysis and 2) thermochemical decomposition of water. This paper will investigate their unique complementary roles to reduce costs of hydrogen production. Together they have a unique potential to serve both de-centralized hydrogen needs in periods of low-demand electricity, and centralized base-load production from a nuclear station. Thermochemical methods have a significantly higher thermal efficiency, but electrolysis can take advantage of low electricity prices during off-peak hours, as well as intermittent and de-centralized supplies like wind, solar or tidal power. By effectively linking these systems, water-based production of hydrogen can become more competitive against the predominant existing technology, SMR (steam-methane reforming).     

On the production of hydrogen via alkaline electrolysis during off-peak periods

This article studies the opportunity for producing hydrogen via alkaline electrolysis from electricity consumption during off-peak periods. Two aspects will be discussed: electricity spot markets and nuclear electricity production in France.

From a market point of view, when there is a significant fluctuation in electricity prices, the use of an electrolysis installation during off-peak periods makes it possible to make quite considerable savings in production costs. Savings vary enormously from one market to the next; some highly fluctuating markets offer very low off-peak prices and allow for viable hydrogen production, even if average electricity prices first appear to be quite high. Very fluctuating spot prices market may be difficult to predict and makes operations of an electrolysis installation more complicated and risky. For other more stable markets, the use of an electrolysis installation during off-peak periods does not appear to be a relevant proposition.

From the point of view of French electricity production, the availability of current nuclear power plants and the estimation of available energy for mass production of hydrogen show that the installations studied would not be viable. For “peak period” use, it would certainly be more useful to have electrolysers with a lower investment proportion, even if this means slightly higher operating costs. Research into large-capacity electrolysers should, therefore, both develop low-production-cost electrolysers, for use in base load mode where dedicated production means are concerned, and highly flexible electrolysers, with low investment costs, which could easily be viable with low rates of use.     

Performance evaluation of hydrogen production based on off-peak electric energy of the nuclear power plant

The article investigates the efficiency of commercial hydrogen production by water electrolysis on the base of NPP excess energy with its additional purification higher than 99.9999%, considering its transport. The competitive high purity hydrogen release price has been determined as compared to the market price. Besides, the use of high duty electrolysis plants has been suggested. Moreover, the advantages of water electrolysis cyclic operation while consuming electric energy from NPP as compared to the continuous mode have been presented in the paper.     

The pricing of off-peak power

Benefit-cost analysis is used to show that even with only one electricity production technique, marginal cost pricing of electricity in a firm off-peak period might reduce social welfare rather than improve it. This may occur when there are more periods with dissimilar demands for power than feasible prices for electricity. Thus the conclusion is reinforced that it may be more important to charge a higher price for electricity during periods of peak demand than a price equal to marginal running costs during the most off-peak hours.     

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.     

Co-production of electricity and hydrogen from wind: A comprehensive scenario-based techno-economic analysis

The aim of this study is to investigate the economic prospects of producing electricity and hydrogen using wind energy under different scenarios. For this, the most essential criteria to investors including Levelized Cost of Wind-generated Electricity (LCOWE), Levelized Cost of Wind-based Hydrogen (LCOWH), payback period, and rate of return are examined. Technical and environmental impacts are factored into the LCOWE formulation to obtain comprehensive insight. Owing to the uncertain nature of future, five degradation rates concerned with wind turbine performance and five likely rates as to the future value of money are investigated under the scenarios of I) utilizing wind electricity to replace fuel oil electricity, II) to replace natural gas electricity and III) without considering environmental penalties. The results indicate that LCOWE would be in the range of 0.0325–0.0755 $/kWh, while the corresponding LCOWH being in the range of 1.375–1.59 $/kg. Moreover, payback period of the related LCOWE and LCOWH would be in the range of 2.55–9.48 yr during the lifetime of wind power plant and 3.91–8.41 yr during that of hydrogen production system, respectively. The corresponding rate of return pertinent to the above-mentioned ones would be respectively in the range of 14.15–23.54% and of 9.87–21.55%.     

Integrated gasification combined cycle based hydrogen electricity plants

Abstract

Integrated gasification combined cycle (IGCC) systems may become the coal technology of choice, because of their superior environmental performance and efficiency. Moreover, the compatibility of IGCC systems with carbon capture and the potential to produce hydrogen and electricity from the same plant opens a broad range of future possibilities. The key technical features of such a plant are reviewed and contrasted with those of more standard forms of IGCC.     

Safety concept of nuclear cogeneration of hydrogen and electricity

There is a significant potential for nuclear combined heat and power (CHP) in quite a number of industries. The reactor concepts of the next generation would be capable to open up, in particular, the high temperature heat market where nuclear energy is applicable to the production processes of hydrogen (or liquid fuels) by steam reforming or water splitting. Due to the need to locate a nuclear facility near the hydrogen plant, an overall safety concept has to deal with the question of safety of the combined nuclear/industrial system by taking into account a qualitatively new class of events characterized by interacting influences. Specific requirements will be determined by such factors as the reactor type, the nature of the industrial process, the separation distances of the industrial facility and population centers from the nuclear plant, and prevailing public attitudes. Based on the Japanese concept of the GTHTR300C nuclear reactor for electricity and hydrogen cogeneration, theoretical studies were conducted on the release, dispersive transport, and explosion of a hydrogen cloud in the atmosphere for the sake of assessing the required minimum separation distance to avoid any risk to the nuclear plant's safety systems. In the case of sulfur-iodine water splitting, the accidental release of process intermediates including large amounts of sulfur dioxide, sulfur trioxide, and sulfuric acid need to be investigated as well to estimate the potential risk to nuclear installations like the operators' room and estimate appropriate separation distances against toxic gas propagation. Results of respective simulation studies will be presented.     

Building and interconnecting hydrogen networks: Insights from the electricity and gas experience in Europe

This paper aims to investigate the transition to a new energy system based on hydrogen in the European liberalized framework. After analyzing the literature on the hydrogen infrastructure needs in Europe, we estimate the size and scope of the transition challenge. We take the theoretical framework of network economics to analyze early hydrogen infrastructure needs. Therefore, several concepts are applied to hydrogen economics such as demand club effects, scale economies on large infrastructures, scope economies, and positive socio-economical externalities. Based on the examples of the electricity and natural gas industry formation in Europe, we argue for public intervention in order to create conditions to reach more rapidly the critical size of the network and to prompt network externalities, allowing for the market diffusion of and, thus, an effective transition to the new energy system.     

Wind energy,electricity, and hydrogen in the Netherlands

The curbing of greenhouse gases (GHG) is an important issue on the international political agenda. The substitution of fossil fuels by renewable energy sources is an often-advocated mitigation strategy. Wind energy is a potential renewable energy source. However, wind energy is not reliable since its electricity production depends on variable weather conditions. High wind energy penetration rates lead to losses due to power plant operation adjustments to wind energy. This research identifies the potential energetic benefits of integrated hydrogen production in electricity systems with high wind energy penetration. This research concludes that the use of system losses for hydrogen production via electrolysis is beneficial in situations with ca. 8 GW or more wind energy capacity in the Netherlands. The 2020 Dutch policy goal of 6 GW will not benefit from hydrogen production in terms of systems efficiency. An ancillary beneficial effect of coupling hydrogen production with wind energy is to relieve the high-voltage grid.     

Appropriate technologies for large-scale production of electricity and hydrogen fuel

Appropriate technology for energy supply requires the use of the most effective energy resources and conversion technologies that will also result in the minimum acceptable impact upon the environment. A useful parameter for evaluation of energy resources for large-scale production of electricity and hydrogen fuel is the specific energy of the appropriate energy resources. Available resources for such large-scale applications must come from some mixture of renewable, fossil, and nuclear energy. Analysis is made of the appropriate use of solar energy, chemical combustion fuels, and nuclear energy on the basis of their specific energy. The results show that the most appropriate resources for large-scale production of electricity and hydrogen are low-specific solar photovoltaic and wind turbine energy for large numbers of distributed small-scale applications and high-specific nuclear energy for smaller numbers of large-scale applications.     

Methanol opportunities for electricity and hydrogen production in bioelectrochemical systems

An anodic syntrophic consortium (exoelectrogenic plus fermentative bacteria) able to use methanol as sole carbon source was developed for the first time in a bioelectrochemical system. In this frame, promising results were obtained in single chamber MFC, comparable to those obtained with readily biodegradable substrates. Regarding MEC operation, the presence of homoacetogenic bacteria led to electron recycling, avoiding net hydrogen production in single chamber MEC. In a double chamber MEC, satisfying results (in terms of coulombic efficiency and cathodic gas recovery) were obtained even though energy recovery still restrained the feasibility of the process. The approach used in this work with methanol opens a new range of possibilities for other complex substrates as electron donors for bioelectrosynthesis.     

An economic analysis of the production of hydrogen from wind-generated electricity for use in transport applications

Wind-generated electricity is often considered a particularly promising option for producing hydrogen from renewable energy sources. However, the economic performances of such systems generally remain unclear because of unspecified or favorable assumptions and operating conditions. The aim of this paper is to clarify these conditions by examining how the hydrogen produced is used. The analysis that has been conducted in the framework of the HyFrance 3 project concerns hydrogen for transport applications. Different technical systems are considered such as motorway hydrogen filling stations, Hythane®-fueled buses or second-generation biofuels production, which present contrasted hydrogen use characteristics. This analysis reveals considerable variations in hydrogen production costs depending on the demand profiles concerned, with the most favorable configurations being those in which storage systems are kept to a minimum.     

Integration of large-scale hydrogen storages in a low-carbon electricity generation system

This study investigates the overall feasibility of large energy storages with hydrogen as energy carrier onsite with a pre-combustion carbon capture and storage coal gasification plant and assesses the general impacts of such a backup installation on an electricity generation system with high wind power portion. The developed system plant configuration consists of four main units namely the gasification unit, main power unit, backup power unit including hydrogen storage and ancillary power unit. Findings show that integrating a backup storage in solid or gaseous hydrogen storage configuration allows to store excessive energy under high renewable power output or low demand and to make use of the stored energy to compensate low renewable output or high power demand. The study concludes that the developed system configuration reaches much higher load factors and efficiency levels than a plant configuration without backup storage, which simply increases its power unit capacity to meet the electricity demand. Also from an economical point of view, the suggested system configurations are capable to achieve lower electricity generation costs.     

Large-scale compressed hydrogen storage as part of renewable electricity storage systems

Storing energy in the form of hydrogen is a promising green alternative. Thus, there is a high interest to analyze the status quo of the different storage options. This paper focuses on the large-scale compressed hydrogen storage options with respect to three categories: storage vessels, geological storage, and other underground storage alternatives. In this study, we investigated a wide variety of compressed hydrogen storage technologies, discussing in fair detail their theory of operation, potential, and challenges. The analysis confirms that a techno-economic chain analysis is required to evaluate the viability of one storage option over another for a case by case. Some of the discussed technologies are immature; however, this does not rule out these technologies; rather, it portrays the research opportunities in the field and the foreseen potential of these technologies. Furthermore, we see that hydrogen would have a significant role in balancing intermittent renewable electricity production.     

Electricity portfolio management: Optimal peak/off-peak allocations

Electricity purchasers manage a portfolio of contracts in order to purchase the expected future electricity consumption profile of a company or a pool of clients. This paper proposes a mean-variance framework to address the concept of structuring the portfolio and focuses on how to optimally allocate positions in peak and off-peak forward contracts. It is shown that the optimal allocations are based on the difference in risk premiums per unit of day-ahead risk as a measure of relative costs of hedging risk in the day-ahead markets. The outcomes of the model are then applied to show (i) that it is typically not optimal to hedge a baseload consumption profile with a baseload forward contract and (ii) that, under reasonable assumptions, risk taking by the purchaser is rewarded by lower expected costs.     

Clean hydrogen production and electricity from coal via chemical looping: Identifying a suitable operating regime

In this paper, a chemical looping combustion (CLC) system, using haematite (Fe₂O₃) as an oxygen carrier, has been simulated in conjunction with a steam–coal gasification process. The analysis has assumed thermodynamic equilibrium throughout. Full heat integration was considered for a range of operating conditions (e.g. by varying oxygen carrier recycle rate). It was found that for low to moderate flows of oxidising steam, it was possible to operate within a regime which could be fully heat-integrated. Furthermore, the size of this operating regime increases with the recycle rate of oxygen carrier. The peak exergetic efficiencies achieved for fully heat-integrated systems were 48.4% and 58.3% at operating pressures of 1 atmosphere and 10 atmospheres respectively, and these were increased respectively to 53.7% and 59.7% when a bottoming steam turbine cycle was included to utilise waste heat. These values compare favourably with those achieved by hydrogen production via steam reformation of methane. The range of suitable operating conditions available at both pressures was encouraging, and showed considerable promise for the successful coupling of a chemical looping system with a gasifier.