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Review of Thermochemical Technologies for Water and Energy Integration Systems: Energy Storage and Recovery
Jun 2022
Publication
Thermochemical technologies (TCT) enable the promotion of the sustainability and the operation of energy systems as well as in industrial sites. The thermochemical operations can be applied for energy storage and energy recovery (alternative fuel production from water/wastewater in particular green hydrogen). TCTs are proven to have a higher energy density and long-term storage compared to standard thermal storage technologies (sensible and latent). Nonetheless these require further research on their development for the increasing of the technology readiness level (TRL). Since TCTs operate with the same input/outputs streams as other thermal storages (for instance wastewater and waste heat streams) these may be conceptually analyzed in terms of the integration in Water and Energy Integration System (WEIS). This work is set to review the techno-economic and environmental aspects related to thermochemical energy storage (sorption and reaction-based) and wastewater-to-energy (particular focus on thermochemical water splitting technology) aiming also to assess their potential into WEIS. The exploited technologies are in general proved to be suitable to be installed within the conceptualization of WEIS. In the case of TCES technologies these are proven to be significantly more potential analogues to standard TES technologies on the scope of the conceptualization of WEIS. In the case of energy recovery technologies although a conceptualization of a pathway to produce usable heat with an input of wastewater further study has to be performed to fully understand the use of additional fuel in combustion-based processes.
A Positive Shift in the Public Acceptability of a Low-Carbon Energy Project After Implementation: The Case of a Hydrogen Fuel Station
Apr 2019
Publication
Public acceptability of low-carbon energy projects is often measured with one-off polls. This implies that opinion-shifts over time are not always taken into consideration by decision makers relying on these polls. Observations have given the impression that public acceptability of energy projects increases after implementation. However this positive shift over time has not yet been systematically studied and is not yet understood very well. This paper aims to fill this gap. Based on two psychological mechanisms loss aversion and cognitive dissonance reduction we hypothesize that specifically people who live in proximity of a risky low-carbon technology—a hydrogen fuel station (HFS) in this case—evaluate this technology as more positive after its implementation than before. We conducted a survey among Dutch citizen living nearby a HFS and indeed found a positive shift in the overall evaluation of HFS after implementation. We also found that the benefits weighed stronger and the risks weaker after the implementation. This shift did not occur for citizens living further away from the HFS. The perceived risks and benefits did not significantly change after implementation neither for citizens living in proximity nor for citizens living further away. The societal implications of the findings are discussed.
Integrating a Top-Gas Recycling and CO2 Electrolysis Process for H2-Rich Gas Injection and Reduce CO2 Emissions from an Ironmaking Blast Furnace
Mar 2022
Publication
Introducing CO2 electrochemical conversion technology to the iron-making blast furnace not only reduces CO2 emissions but also produces H2 as a byproduct that can be used as an auxiliary reductant to further decrease carbon consumption and emissions. With adequate H2 supply to the blast furnace the injection of H2 is limited because of the disadvantageous thermodynamic characteristics of the H2 reduction reaction in the blast furnace. This paper presents thermodynamic analysis of H2 behaviour at different stages with the thermal requirement consideration of an iron-making blast furnace. The effect of injecting CO2 lean top gas and CO2 conversion products H2–CO gas through the raceway and/or shaft tuyeres are investigated under different operating conditions. H2 utilisation efficiency and corresponding injection volume are studied by considering different reduction stages. The relationship between H2 injection and coke rate is established. Injecting 7.9–10.9 m3/tHM of H2 saved 1 kg/tHM coke rate depending on injection position. Compared with the traditional blast furnace injecting 80 m3/tHM of H2 with a medium oxygen enrichment rate (9%) and integrating CO2 capture and conversion reduces CO2 emissions from 534 to 278 m3/tHM. However increasing the hydrogen injection amount causes this iron-making process to consume more energy than a traditional blast furnace does.
A Comparative Study of CFD-Modelling for Lean Premixed Hydrogen Deflagrations in Large-scale Vented Vessels
Sep 2021
Publication
Hydrogen combustion inside a post-accident nuclear reactor containment may pose a challenge to the containment integrity which could alter the fission-product release source term to the public. Combustion-generated overpressures may be relieved by venting to adjacent compartments through relief panels or existing openings. Thus an improved understanding of the propagation of lean hydrogen deflagrations in inter-connected compartments is essential for the development of appropriate management strategies. GOTHIC is a general purpose lumped parameter thermal-hydraulic code for solving multi-phase compressible flows which is accepted as an industry-standard code for containment safety analyses. Following the Fukushima accident the application of three-dimensional computational fluid dynamics methods to high-fidelity detailed analysis of hydrogen combustion processes has become more widespread. In this study a recently developed large-eddy-simulation (LES) capability is applied to the prediction of lean premixed hydrogen deflagrations in large-scale vented vessels of various configurations. The LES predictions are compared with GOTHIC predictions and experimental data obtained from the large-scale vented combustion test facility at the Canadian Nuclear Laboratories. The LES methodology makes use of a flamelet- or a progress-variable-based combustion model. An empirical burning velocity model is combined with an advanced finite-volume framework and a mesh-independent subfilter-scale model. Descriptions of the LES and GOTHIC modelling approaches used to simulate the hydrogen reactive flows in the vented vessels along with the experimental data sets are given. The potential and limitations of the lumped parameter and LES approaches for accurately describing lean premixed hydrogen deflagrations in vented vessels are discussed.
Can Green Hydrogen Production Be Economically Viable under Current Market Conditions
Dec 2020
Publication
This paper discusses the potential of green hydrogen production in a case study of a Slovenian hydro power plant. To assess the feasibility and eligibility of hydrogen production at the power plant we present an overview of current hydrogen prices and the costs of the power-to-gas system for green hydrogen production. After defining the production cost for hydrogen at the case study hydro power plant we elaborate on the profitability of hydrogen production over electricity. As hydrogen can be used as a sustainable energy vector in industry heating mobility and the electro energetic sectors we discuss the current competitiveness of hydrogen in the heating and transport sectors. Considering the current prices of different fuels it is shown that hydrogen can be competitive in the transport sector if it is unencumbered by various environmental taxes. The second part of the paper deals with hydrogen production in the context of secondary control ancillary service provided by a case study power plant. Namely hydrogen can be produced during the time period when there is no demand for extra electric power within a secondary control ancillary service and thus the economics of power plant operation can be improved.
Climate Action: Prospects of Green Hydrogen in Africa
Feb 2022
Publication
Africa is rich with an abundance of renewable energy sources that can help meeting the continent’s demand for electricity to promote economic growth and meet global targets for CO2 reduction. Green Hydrogen is considered one of the most promising technologies for energy generation transportation and storage. In this paper the prospects of green hydrogen production potential in Africa are investigated along with its usage for future implementation. Moreover an overview of the benefits of shifting to green Hydrogen technology is presented. The current African infrastructure and policies are tested against future targets and goals. Furthermore the study embraces a detailed theoretical environmental technological and economic assessment putting the local energy demands into consideration.
Evolutions in Hydrogen and Fuel Cell Standardization: The HarmonHy Experience
Dec 2007
Publication
HarmonHy is a European Union-funded Specific Support Action aiming to make an assessment of the activities on hydrogen and fuel cell regulations codes and standards (RCS) on a worldwide level. On this basis gaps have been identified and potential conflicts between regulations codes and standards have been investigated. Types of document to be referred to include international regional and national standards EU directives UNECE regulations… Particular attention will be paid to the identification of the needs for standards as perceived by the industry as well as to actions aiming to ensure concordance between standards codes and regulations. Standards and regulations require harmonization. HarmonHy pursues the elaboration of an action plan and a roadmap for future work on harmonizing regulations codes and standards on hydrogen and fuel cells on an international level.
Spherically Expanding Flame Simulations in Cantera Using a Lagrangian Formulation
Sep 2021
Publication
A Lagrangian-based one-dimensional approach has been developed using Cantera to study the dynamics of spherically expanding flames. The detailed reaction model USC-Mech II has been employed to examine flame propagating in hydrogen-air mixtures. In the first part our approach has been validated against laminar flame speed and Markstein number data from the literature. It was shown that the laminar flame speed was predicted within 5% on average but that discrepancies were observed for the Markstein number especially for rich mixtures. In the second part a detailed analysis of the thermo-chemical dynamics along the path of Lagrangian particles propagating in stretched flames was performed. For mixtures with negative Markstein lengths it was found that at high stretch rates the mixture entering the reaction-dominated period is less lean with respect to the initial mixture than at low stretch rate. This induces a faster rate of chemical heat release and of active radical production which results in a higher flame propagation speed. Opposite effects were observed for mixtures with positive Markstein lengths for which slower flame propagation was observed at high stretch rates compared to low stretch rates."
Uncertainty of Acceleration of a Premixed Laminar Unstable Hydrogen Flame
Sep 2021
Publication
Unstable hydrogen-air flame behavior randomities are important for industrial safety hydrogen infrastructure safety and nuclear power plant hydrogen safety problems. The paper is devoted to an experimental and theoretical study of the uncertainty in the acceleration of a premixed laminar unstable hydrogen flame. The results of experiments on spherical flame propagation in hydrogen-air mixtures with a hydrogen content of 10 to 60% are presented. The experiments were repeated up to 30 times in the same mixtures. A statistical analysis of the experimental results has been carried out. The scatter of the experimental data depending on the hydrogen content in the mixture was estimated. It was found to be between 8 to 17% for different mixtures with the same flame radius and mixture composition. Similar results were obtained using the numerical integration of the Sivashinsky equation of flame propagation.
Review of the Liquid Hydrogen Storage Tank and Insulation System for the High-Power Locomotive
Jun 2022
Publication
Hydrogen has been attracting attention as a fuel in the transportation sector to achieve carbon neutrality. Hydrogen storage in liquid form is preferred in locomotives ships drones and aircraft because these require high power but have limited space. However liquid hydrogen must be in a cryogenic state wherein thermal insulation is a core problem. Inner materials including glass bubbles multi-layer insulation (MLI) high vacuum and vapor-cooled shields are used for thermal insulation. An analytic study is preferred and proceeds liquid hydrogen tanks due to safety regulations in each country. This study reviewed the relevant literature for thermodynamic modeling. The literature was divided into static dynamic and systematic studies. In summary the authors summarized the following future research needs: The optimal design of the structure including suspension baffle and insulation system can be studied to minimize the boil-off gas (BOG). A dynamic study of the pressure mass flow and vaporizer can be completed. The change of the components arrangement from the conventional diesel–electric locomotive is necessary.
Effect of Heat Transfer through the Release of Pipe on Simulations of Cryogenic Hydrogen Jet Fires and Hazard Distances
Sep 2021
Publication
Jet flames originated by cryo-compressed ignited hydrogen releases can cause life-threatening conditions in their surroundings. Validated models are needed to accurately predict thermal hazards from a jet fire. Numerical simulations of cryogenic hydrogen flow in the release pipe are performed to assess the effect of heat transfer through the pipe walls on jet parameters. Notional nozzle exit diameter is calculated based on the simulated real nozzle parameters and used in CFD simulations as a boundary condition to model jet fires. The CFD model was previously validated against experiments with vertical cryogenic hydrogen jet fires with release pressures up to 0.5 MPa (abs) release diameter 1.25 mm and temperatures as low as 50 K. This study validates the CFD model in a wider domain of experimental release conditions - horizontal cryogenic jets at exhaust pipe temperature 80 K pressure up to 2 MPa abs and release diameters up to 4 mm. Simulation results are compared against experimentally measured parameters as hydrogen mass flow rate flame length and radiative heat flux at several locations from the jet fire. The CFD model reproduces well experiments with reasonable engineering accuracy. Jet fire hazard distances established using three different criteria - temperature thermal radiation and thermal dose - are compared and discussed based on CFD simulation results.
Fuel Cell Solution for Marine Applications
Sep 2021
Publication
With future regulations on the horizon port authorities and ship owners/operators are looking at alternative propulsion solutions to reduce emission. Fuel cell technology provides an attractive zeroemission solution to generate electric power on board using hydrogen as a fuel. Fuel cell systems are scalable from 200kW to multi-MW providing high efficiency dispatchable clean quiet power generation. Several innovative pilot projects are on the way to demonstrate the marine application of this proven technology. Electrification of propulsion systems is advancing and fuel cell technology provides the opportunity to produce on board large quantity of power with zero-emission using hydrogen as a fuel. We will present the value proposition of having a fuel cell power generator on board of an electric vessel while discussing the safety considerations with the fuel cell module and the onboard fuel storage. We will present some of our current fuel cell marine projects and review some of the product development considerations including system architecture and safety as well as hydrogen supply and on-board fuel storage.
Low Temperature Autoignition of Diesel Fuel Under Dual Operation with Hydrogen and Hydrogen-carriers
Mar 2022
Publication
While electrification of light duty vehicles is becoming a real solution to abate local pollutant as well as greenhouse gases emission heavy duty applications (such as long distance freight and maritime transport) will keep requiring fuel-based propulsion systems. In these sectors dominated by compression ignition engines research on alternative biofuels and new combustion modes is still highly necessary. Dual-fuel combustion appears as a very promising concept to replace conventional diesel fuel by sustainable ones. Among the latter hydrogen-derived fuels (the so-called electrofuels or e-fuels) are maybe the most interesting. This work addresses the effect of partial substitution of diesel fuel by hydrogen and hydrogen-carriers (ammonia and methane) on the autoignition process under low temperature conditions. Tests were carried out in a constant volume combustion chamber at different temperatures (535 600 and 650 ◦C) and pressures (11 16 and 21 bar). While the cool flames timing and intensity was only slightly affected by the low reactivity fuel energy content the main ignition was delayed this effect being much more noticeable for ammonia followed by hydrogen and finally methane. Kinetic simulations showed a clear competition for active radicals between both fuels (diesel and low reactivity fuel). The combustion duration also increased with the hydrogen or hydrogen-carrier content which greatly points to the need of modifications in the injection strategy of compression ignition engines operating under dual mode. A correlation was proposed for estimating the autoignition delay time for dual-fuel lean combustion at low temperature.
Numerical Investigation of Thermal Hazards from Under-expanded Hydrogen Jet Fires using a New Scheme for the Angular Discretization of the Radiative Intensity
Sep 2021
Publication
In the context of a numerical investigation of thermal hazards from two under-expanded hydrogen jet fires results from a newly-developed thermal radiation module of the ADREA-HF computational fluid dynamics (CFD) code were validated against two physical experiments. The first experiment was a vertical under-expanded hydrogen jet fire at 170 bar with the objective of the numerical investigation being to capture the spatial distribution of the radial radiative heat flux at a given time instant. In the second case a horizontal under-expanded hydrogen jet fire at 340 bar was considered. Here the objective was to capture the temporal evolution of the radial radiative heat flux at selected fixed points in space. The numerical study employs the eddy dissipation model for combustion and the finite volume method (FVM) for the calculation of the radiative intensity. The FVM was implemented using a novel angular discretization scheme. By dividing the unit sphere into an arbitrary number of exactly equal angular control volumes this new scheme allows for more flexibility and efficiency. A demonstration of numerical convergence as a function the number of both spatial and angular control volumes was performed.
Numerical Investigation on the Flame Structure and CO/NO Formations of the Laminar Premixed Biogas–Hydrogen Impinging Flame in the Wall Vicinity
Nov 2021
Publication
The near-wall flame structure and pollutant emissions of the laminar premixed biogashydrogen impinging flame were simulated with a detailed chemical mechanism. The spatial distributions of the temperature critical species and pollutant emissions near the wall of the laminar premixed biogas–hydrogen impinging flame were obtained and investigated quantitatively. The results show that the cold wall can influence the premixed combustion process in the flame front which is close to the wall but does not touch the wall and results in the obviously declined concentrations of OH H and O radicals in the premixed combustion zone. After flame quenching a high CO concentration can be observed near the wall at equivalence ratios (ϕ) of both 0.8 and 1.2. Compared with that at ϕ = 1.0 more unburned fuel is allowed to pass through the quenching zone and generate CO after flame quenching near the wall thanks to the suppressed fuel consumption rate near the wall and the excess fuel in the unburned gases at ϕ = 0.8 and 1.2 respectively. By isolating the formation routes of NO production it is found that the fast-rising trend of NO concentration near the wall in the post flame region at ϕ = 0.8 is attributed to the NO transportation from the NNH route primarily while the prompt NO production accounts for more than 90% of NO generation in the wall vicinity at ϕ = 1.2. It is thus known that thanks to the effectively increased surface-to-volume ratio the premixed combustion process in the downsized chamber will be affected more easily by the amplified cooling effects of the cold wall which will contribute to the declined combustion efficiency increased CO emission and improved prompt NO production.
Hydrogen Emissions from the Hydrogen Value Chain-emissions Profile and Impact to Global Warming
Feb 2022
Publication
Future energy systems could rely on hydrogen (H2) to achieve decarbonisation and net-zero goals. In a similar energy landscape to natural gas H2 emissions occur along the supply chain. It has been studied how current gas infrastructure can support H2 but there is little known about how H2 emissions affect global warming as an indirect greenhouse gas. In this work we have estimated for the first time the potential emission profiles (g CO2eq/MJ H2HHV) of H2 supply chains and found that the emission rates of H2 from H2 supply chains and methane from natural gas supply are comparable but the impact on global warming is much lower based on current estimates. This study also demonstrates the critical importance of establishing mobile H2 emission monitoring and reducing the uncertainty of short-lived H2 climate forcing so as to clearly address H2 emissions for net-zero strategies.
Exergy Estimate of a Novel Hybrid Solar-gas Power and Organic Rankine Cycle-based Hydrogen-production System
Mar 2022
Publication
This study proposes a novel hybrid solar-gas power and hydrogen-production system which is comprised by the solar tower thermal system gas-steam turbine combined cycle and organic Rankine cycle-based hydrogen-production system. Based on the Ebsilon code the operation processes of the hybrid system are simulated. The results show that the output power and electric efficiency of the hybrid system are 103.9 MW and 41.3% and the daily hydrogen output is 62.2 kg. The operation simulation results of the hybrid system reveal that the gas-steam combined cycle and solar island can both achieve stable operations and the power generation section and hydrogen-production device can both work effectively which means the hybrid system is technically feasible. The exergy estimate results of the hybrid system show that the combustion chamber and solar receiver have the two largest exergy destructions which are 56.5 MW and 45.3 MW. That means the performances of the two components can be further improved. For the hydrogen-production system the exergy destructions of the proton exchange membrane electrolyzer turbine condenser and evaporator of the organic Rankine cycle are 0.156 MW 0.111 MW 2.338 MW and 1.891 MW and the corresponding exergy efficiencies are 51.2% 92.6% 80.7% and 79.5% respectively.
The NREL Sensor Laboratory: Status and Future Directions for Hydrogen Detection
Sep 2021
Publication
The NREL Hydrogen Sensor Laboratory was commissioned in 2010 as a resource for the national and international hydrogen community to ensure the availability and proper use of hydrogen sensors. Since then the Sensor Laboratory has provided unbiased verification of hydrogen sensor performance for sensor developers end-users and regulatory agencies and has also provided active support for numerous code and standards development organizations. Although sensor performance assessment remains a core capability the mission of the NREL Sensor Laboratory has expanded toward a more holistic approach regarding the role of hydrogen detection and its implementation strategy for both assurance of facility safety and for process control applications. Active monitoring for detection of unintended releases has been identified as a viable approach for improving facility safety and lowering setbacks. The current research program for the Sensor Laboratory addresses both conventional and advanced developing detection strategies in response to the emerging large-scale hydrogen markets such as those envisioned by H2@Scale. These emerging hydrogen applications may require alternative detection strategies that supplement and may ultimately supplant the use of traditional sensors for monitoring hydrogen releases. Research focus areas for the NREL Sensor Laboratory now encompass the characterization of released hydrogen behavior to optimize detection strategies for both indoor and outdoor applications assess advanced methods of hydrogen leak detection such as hydrogen wide area monitoring for large scale applications implement active monitoring as a risk reduction strategy to improve safety at hydrogen facilities and to provide continuing support of hydrogen safety codes and standards. In addition to assurance of safety detection will be critical for process control applications such as hydrogen fuel quality verification for fuel cell vehicle applications and for monitoring and controlling of hydrogen-natural gas blend composition.
Thermochemical Recuperation to Enable Efficient Ammonia-Diesel Dual-Fuel Combustion in a Compression Ignition Engine
Nov 2021
Publication
A thermochemical recuperation (TCR) reactor was developed and experimentally evaluated with the objective to improve dual-fuel diesel–ammonia compression ignition engines. The novel system simultaneously decomposed ammonia into a hydrogen-containing mixture to allow high diesel fuel replacement ratios and oxidized unburned ammonia emissions in the exhaust overcoming two key shortcomings of ammonia combustion in engines from the previous literature. In the experimental work a multi-cylinder compression ignition engine was operated in dual-fuel mode using intake-fumigated ammonia and hydrogen mixtures as the secondary fuel. A full-scale catalytic TCR reactor was constructed and generated the fuel used in the engine experiments. The results show that up to 55% of the total fuel energy was provided by ammonia on a lower heating value basis. Overall engine brake thermal efficiency increased for modes with a high exhaust temperature where ammonia decomposition conversion in the TCR reactor was high but decreased for all other modes due to poor combustion efficiency. Hydrocarbon and soot emissions were shown to increase with the replacement ratio for all modes due to lower combustion temperatures and in-cylinder oxidation processes in the late part of heat release. Engine-out oxides of nitrogen (NOx) emissions decreased with increasing diesel replacement levels for all engine modes. A higher concentration of unburned ammonia was measured in the exhaust with increasing replacement ratios. This unburned ammonia predominantly oxidized to NOx species over the oxidation catalyst used within the TCR reactor. Ammonia substitution thus increased post-TCR reactor ammonia and NOx emissions in this work. The results show however that engine-out NH3 -to-NOx ratios were suitable for passive selective catalytic reduction thus demonstrating that both ammonia and NOx from the engine could be readily converted to N2 if the appropriate catalyst were used in the TCR reactor.
Review of the Effects of Fossil Fuels and the Need for a Hydrogen Fuel Cell Policy in Malaysia
Feb 2023
Publication
The world has relied on fossil fuel energy for a long time producing many adverse effects. Long-term fossil fuel dependency has increased carbon emissions and accelerated climate change. In addition fossil fuels are also depleting and will soon be very costly. Moreover the expensive national electricity grid has yet to reach rural areas and will be cut off in inundation areas. As such alternative and carbon-free hydrogen fuel cell energy is highly recommended as it solves these problems. The reviews find that (i) compared to renewable energy such as solar biomass and hydropower a fuel cell does not require expensive transmission through an energy grid and is carbon-free and hence it is a faster agent to decelerate climate change; (ii) fuel cell technologies have reached an optimum level due to the high-efficiency production of energy and they are environmentally friendly; (iii) the absence of a policy on hydrogen fuel cells will hinder investment from private companies as they are not adequately regulated. It is thus recommended that countries embarking on hydrogen fuel cell development have a specific policy in place to allow the government to fund and regulate hydrogen fuel cells in the energy generation mix. This is essential as it provides the basis for alternative energy governance development and management of a country.
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