Production & Supply Chain
A Solar Thermal Sorption-enhanced Steam Methane Reforming (SE-SMR) Approach and its Performance Assessment
Feb 2022
Publication
This paper proposes an integration of concentrating solar power (CSP) with a sorption-enhanced steam methane reforming (SE-SMR) process and assesses its overall solar-to-fuel conversion performance. A thermodynamic treatment of the SE-SMR process for H2 production is presented and evaluated in an innovative two reactors system configuration using CSP as a heat input. Four metal carbonate/metal oxide pairs are considered and the equilibrium thermodynamics reveals that CaCO3/CaO pair is the most suitable candidate for this process. Additionally a reactor-scale thermodynamic model is developed to determine the optimum operating conditions for the process. For the carbonation step temperatures between 700 and 900 K and steam-to-methane ratio ≥4 are found to be the most favorable. Furthermore an advanced process model which utilizes operating conditions determined from the reactor-scale model is developed to evaluate the process efficiency. The model predicts that the proposed process can achieve a solar-to-fuel efficiency ~41% for calcination temperature of 1500 K and carbonation temperature of 800 K without considering any solid heat recovery. An additional 2.5% increase in the process efficiency is feasible with the consideration of the solid heat recovery. This study shows the thermodynamic feasibility of integrating the SE-SMR process with CSP technologies.
Sub-second and Ppm-level Optical Sensing of Hydrogen Using Templated Control of Nano-hydride Geometry and Composition
Apr 2021
Publication
The use of hydrogen as a clean and renewable alternative to fossil fuels requires a suite of flammability mitigating technologies particularly robust sensors for hydrogen leak detection and concentration monitoring. To this end we have developed a class of lightweight optical hydrogen sensors based on a metasurface of Pd nano-patchy particle arrays which fulfills the increasing requirements of a safe hydrogen fuel sensing system with no risk of sparking. The structure of the optical sensor is readily nano-engineered to yield extraordinarily rapid response to hydrogen gas (<3 s at 1 mbar H2) with a high degree of accuracy (<5%). By incorporating 20% Ag Au or Co the sensing performances of the Pd-alloy sensor are significantly enhanced especially for the Pd80Co20 sensor whose optical response time at 1 mbar of H2 is just ~0.85 s while preserving the excellent accuracy (<2.5%) limit of detection (2.5 ppm) and robustness against aging temperature and interfering gases. The superior performance of our sensor places it among the fastest and most sensitive optical hydrogen sensors.
Comparison Between Hydrogen Production by Alkaline Water Electrolysis and Hydrogen Production by PEM Electrolysis
Sep 2021
Publication
Hydrogen is an ideal clean energy source that can be used as an energy storage medium for renewable energy sources. The water electrolysis hydrogen production technology which is one of the mainstream hydrogen production methods can be used to produce high-purity hydrogen and other energy sources can be converted into hydrogen storage by electrolysis. Hydrogen production by alkaline water electrolysis and hydrogen production by PEM electrolysis are all water electrolysis hydrogen production technologies that have been industrially applied. From the application point of view the paper compares the working principle of the two kinds of electrolyzers the process flow of hydrogen production equipment advantages and disadvantages. This article provides a reference for relevant researchers.
Improved Hydrogen-Production-Based Power Management Control of a Wind Turbine Conversion System Coupled with Multistack Proton Exchange Membrane Electrolyzers
Mar 2020
Publication
This paper deals with two main issues regarding the specific energy consumption in an electrolyzer (i.e. the Faraday efficiency and the converter topology). The first aspect is addressed using a multistack configuration of proton exchange membrane (PEM) electrolyzers supplied by a wind turbine conversion system (WTCS). This approach is based on the modeling of the wind turbine and the electrolyzers. The WTCS and the electrolyzers are interfaced through a stacked interleaved DC–DC buck converter (SIBC) due to its benefits for this application in terms of the output current ripple and reliability. This converter is controlled so that it can offer dynamic behavior that is faster than the wind turbine avoiding overvoltage during transients which could damage the PEM electrolyzers. The SIBC is designed to be connected in array configuration (i.e. parallel architecture) so that each converter operates at its maximum efficiency. To assess the performance of the power management strategy experimental tests were carried out. The reported results demonstrate the correct behavior of the system during transient operation.
Exploring the Competitiveness of Hydrogen-fueled Gas Turbines in Future Energy Systems
Oct 2021
Publication
Hydrogen is currently receiving attention as a possible cross-sectoral energy carrier with the potential to enable emission reductions in several sectors including hard-to-abate sectors. In this work a techno-economic optimization model is used to evaluate the competitiveness of time-shifting of electricity generation using electrolyzers hydrogen storage and gas turbines fueled with hydrogen as part of the transition from the current electricity system to future electricity systems in Years 2030 2040 and 2050. The model incorporates an emissions cap to ensure a gradual decline in carbon dioxide (CO2) levels targeting near-zero CO2 emissions by Year 2050 and this includes 15 European countries. The results show that hydrogen gas turbines have an important role to play in shifting electricity generation and providing capacity when carbon emissions are constrained to very low levels in Year 2050. The level of competitiveness is however considerably lower in energy systems that still allow significant levels of CO2 emissions e.g. in Year 2030. For Years 2040 and 2050 the results indicate investments mainly in gas turbines that are partly fueled with hydrogen with 30e77 vol.-% hydrogen in biogas although some investments in exclusively hydrogen-fueled gas turbines are also envisioned. Both open cycle and combined cycle gas turbines (CCGT) receive investments and the operational patterns show that also CCGTs have a frequent cyclical operation whereby most of the start-stop cycles are less than 20 h in duration.
Catalytic Hydrogen Production, Storage and Application
Jul 2021
Publication
Hydrogen is a clean fuel for transportation and energy storage. It has several attractive features including a higher energy content by weight use in fuel cells that produces only water as a by-product storage in small and large quantities by various methods and established transportation and infrastructures. A hydrogen economy consists of three steps i.e. hydrogen production storage and applications. All three steps involved in a hydrogen economy can be divided into catalytic and non-catalytic approaches. For catalytic processes the efficiency highly depends on the type and physico-chemical characteristics of the catalysts. Therefore for the improvement of these catalytic processes the development of highly efficient and stable catalysts is highly required.
Kinetic Parameters Estimation via Dragonfly Algorithm (DA) and Comparison of Cylindrical and Spherical Reactors Performance for CO2 Hydrogenation to Hydrocarbons
Oct 2020
Publication
Climate change and global warming as well as growing global demand for hydrocarbons in industrial sectors make great incentives to investigate the utilization of CO2 for hydrocarbons production. Therefore finding an in-depth understanding of the CO2 hydrogenation reactors along with simulating reactor responses to different operating conditions are of paramount importance. However the reaction mechanisms for CO2 hydrogenation and their corresponding kinetic parameters have been disputable yet. In this regard considering the previously proposed Langmuir-Hinshelwood-Hougen-Watson (LHHW) mechanism which considered CO2 hydrogenation as a combination of reverse water gas shift (RWGS) and Fischer-Tropsch (FT) reactions and using a one-dimensional pseudo-homogeneous non-isothermal model kinetic parameters of the rate expressions are estimated via fitting experimental and modelling data through a novel swarm intelligence optimization technique called dragonfly algorithm (DA). The predicted reactants conversion using DA algorithm are closer to the experimental data (with about 4% error) comparing to those obtained by the artificial bee colony (ABC) algorithm and are in significant agreement with available literature data. The proposed model is used to assess the effect of reactor configuration on the performance and temperature fluctuations. Results show that axial flow spherical reactor (AFSR) and radial flow spherical reactor (RFSR) exhibiting the same surface area with that of the cylindrical reactor (CR) i.e. AFSR-2 and RFSR-2-i are the most efficient exhibiting hydrocarbons selectivity of 40.330% and 40.286% at CO2 conversion of 53.763% and 53.891%. In addition it is revealed that the location of the jacket has an essential role in controlling the reactor temperature.
An Autonomous Device for Solar Hydrogen Production from Sea Water
Feb 2022
Publication
Hydrogen production from water electrolysis is one of the most promising approaches for the production of green H2 a fundamental asset for the decarbonization of the energy cycle and industrial processes. Seawater is the most abundant water source on Earth and it should be the feedstock for these new technologies. However commercial electrolyzers still need ultrapure water. The debate over the advantages and disadvantages of direct sea water electrolysis when compared with the implementation of a distillation/purification process before the electrolysis stage is building in the relevant research. However this debate will remain open for some time essentially because there are no seawater electrolyser technologies with which to compare the modular approach. In this study we attempted to build and validate an autonomous sea water electrolyzer able to produce high-purity green hydrogen (>90%) from seawater. We were able to solve most of the problems that natural seawater electrolyses imposes (high corrosion impurities etc.) with decisions based on simplicity and sustainability and those issues that are yet to be overcome were rationally discussed in view of future electrolyzer designs. Even though the performance we achieved may still be far from industrial standards our results demonstrate that direct seawater electrolysis with a solar-to-hydrogen efficiency of ≈7% can be achieved with common low-cost materials and affordable fabrication methods.
Economic Analysis of Improved Alkaline Water Electrolysis
Feb 2017
Publication
Alkaline water electrolysis (AWE) is a mature hydrogen production technology and there exists a range of economic assessments for available technologies. For advanced AWEs which may be based on novel polymer-based membrane concepts it is of prime importance that development comes along with new configurations and technical and economic key process parameters for AWE that might be of interest for further economic assessments. This paper presents an advanced AWE technology referring to three different sites in Europe (Germany Austria and Spain). The focus is on financial metrics the projection of key performance parameters of advanced AWEs and further financial and tax parameters. For financial analysis from an investor’s (business) perspective a comprehensive assessment of a technology not only comprises cost analysis but also further financial analysis quantifying attractiveness and supply/market flexibility. Therefore based on cash flow (CF) analysis a comprehensible set of metrics may comprise levelised cost of energy or respectively levelized cost of hydrogen (LCH) for cost assessment net present value (NPV) for attractiveness analysis and variable cost (VC) for analysis of market flexibility. The German AWE site turns out to perform best in all three financial metrics (LCH NPV and VC). Though there are slight differences in investment cost and operation and maintenance cost projections for the three sites the major cost impact is due to the electricity cost. Although investment cost is slightly lower and labor cost is significantly lower in Spain the difference can not outweigh the higher electricity cost compared to Germany. Given the assumption that the electrolysis operators are customers directly and actively participating in power markets and based on the regulatory framework in the three countries in this special case electricity cost in Germany is lowest. However as electricity cost is profoundly influenced by political decisions as well as the implementation of economic instruments for transforming electricity systems toward sustainability it is hardly possible to further improve electricity price forecasts.
Multi-Criteria Optimization of a Biomass-Based Hydrogen Production System Integrated With Organic Rankine Cycle
Oct 2020
Publication
Biomass-based gasification is an attractive and promising pathway for hydrogen production. In this work a biomass-based hydrogen production system integrated with organic Rankine cycle was designed and investigated to predict the performance of hydrogen production yield and electricity generation under various operating conditions. The modified equilibrium model presented desirable results for the produced syngas compositions compared with the experimental data. Hydrogen yields from four types of biomass (wood chips daily manure sorghum and grapevine pruning wastes) were compared under the same operating condition with wood chips exhibiting the maximum hydrogen yield of 11.59 mol/kg. The effects of gasification temperature equivalence ratio and steam-to-biomass ratio on the hydrogen yield and electricity generation were investigated by using the response surface method. Furthermore the system was optimized using a genetic algorithm based on the response surface model. A preferred optimal solution with a hydrogen yield of 39.31 mol/kg and an output power of 3558.08 kW (0.99 kW h/kg) was selected by the linear programming technique for multidimensional analysis of the preference method.
Experimental and Numerical Study of Low Temperature Methane Steam Reforming for Hydrogen Production
Dec 2017
Publication
Low temperature methane steam reforming for hydrogen production using experimental developed Ni/Al2O3 catalysts is studied both experimentally and numerically. The catalytic activity measurements were performed at a temperature range of 500–700 ◦C with steam to carbon ratio (S/C) of 2 and 3 under atmospheric pressure conditions. A mathematical analysis to evaluate the reaction feasibility at all different conditions that have been applied by using chemical equilibrium with applications (CEA) software and in addition a mathematical model focused on the kinetics and the thermodynamics of the reforming reaction is introduced and applied using a commercial finite element analysis software (COMSOL Multiphysics 5.0). The experimental results were employed to validate the extracted simulation data based on the yields of the produced H2 CO2 and CO at different temperatures. A maximum hydrogen yield of 2.7 mol/mol-CH4 is achieved at 700 ◦C and S/C of 2 and 3. The stability of the 10%Ni/Al2O3 catalyst shows that the catalyst is prone to deactivation as supported by Thermogravimetric Analysis TGA results.
Bioanode as a Limiting Factor to Biocathode Performance in Microbial Electrolysis Cells
Mar 2017
Publication
The bioanode is important for a microbial electrolysis cell (MEC) and its robustness to maintain its catalytic activity affects the performance of the whole system. Bioanodes enriched at a potential of +0.2 V (vs. standard hydrogen electrode) were able to sustain their oxidation activity when the anode potential was varied from -0.3 up to +1.0 V. Chronoamperometric test revealed that the bioanode produced peak current density of 0.36 A/m2 and 0.37 A/m2 at applied potential 0 and +0.6 V respectively. Meanwhile hydrogen production at the biocathode was proportional to the applied potential in the range from -0.5 to -1.0 V. The highest production rate was 7.4 L H2/(m2 cathode area)/day at -1.0 V cathode potential. A limited current output at the bioanode could halt the biocathode capability to generate hydrogen. Therefore maximum applied potential that can be applied to the biocathode was calculated as -0.84 V without overloading the bioanode.
Exploring the Capability of Mayenite (12CaO·7Al2O3) as Hydrogen Storage Material
Mar 2021
Publication
We utilized nanoporous mayenite (12CaO·7Al2O3) a cost-effective material in the hydride state (H−) to explore the possibility of its use for hydrogen storage and transportation. Hydrogen desorption occurs by a simple reaction of mayenite with water and the nanocage structure transforms into a calcium aluminate hydrate. This reaction enables easy desorption of H− ions trapped in the structure which could allow the use of this material in future portable applications. Additionally this material is 100% recyclable because the cage structure can be recovered by heat treatment after hydrogen desorption. The presence of hydrogen molecules as H− ions was confirmed by 1H-NMR gas chromatography and neutron diffraction analyses. We confirmed the hydrogen state stability inside the mayenite cage by the first-principles calculations to understand the adsorption mechanism and storage capacity and to provide a key for the use of mayenite as a portable hydrogen storage material. Further we succeeded in introducing H− directly from OH− by a simple process compared with previous studies that used long treatment durations and required careful control of humidity and oxygen gas to form O2 species before the introduction of H−.
Study of the Effect of Addition of Hydrogen to Natural Gas on Diaphragm Gas Meters
Jun 2020
Publication
Power-to-gas technology plays a key role in the success of the energy transformation. This paper addresses issues related to the legal and technical regulations specifying the rules for adding hydrogen to the natural gas network. The main issue reviewed is the effects of the addition of hydrogen to natural gas on the durability of diaphragm gas meters. The possibility of adding hydrogen to the gas network requires confirmation of whether within the expected hydrogen concentrations long-term operation of gas meters will be ensured without compromising their metrological properties and operational safety. Methods for testing the durability of gas meters applied at test benches and sample results of durability tests of gas meters are presented. Based on these results a metrological and statistical analysis was carried out to establish whether the addition of hydrogen affects the durability of gas meters over time. The most important conclusion resulting from the conducted study indicates that for the tested gas meter specimens there was no significant metrological difference between the obtained changes of errors of indications after testing the durability of gas meters with varying hydrogen content (from 0% to 15%).
Study of the Co-production of Butanol and Hydrogen by Immobilizing Clostridium Acetobutylicum CICC8012
Mar 2019
Publication
Three kinds of carrier materials activated carbon bagasse and brick were used as immobilizing carriers during fermentation by Clostridium acetobutylicum CICC8012. Compared with cell suspended fermentation enhanced fermentation performance was achieved during immobilizing cell fermentation with shorter fermentation time required. During the experiments hydrogen and butanol appear to be competitive events. The best fermentation performance of butanol was obtained in the case of bagasse as immobilizing carrier (5.804g/L of butanol production 0.22g/g of yield and 0.44g/L/h of productivity) while the hydrogen yield was just 1.41 mol/mol. The highest hydrogen productivity (402mL/L/h) and yield (1.808mol/mol glucose) could be obtained in the case of brick as immobilizing carrier while the butanol yield was 0.18 g/g. The highest hydrogen concentration of 66.76 % was obtained in the case of activated carbon as immobilizing carrier.
A Direct Synthesis of Platinum/Nickel Co-catalysts on Titanium Dioxide Nanotube Surface from Hydrometallurgical-type Process Streams
Aug 2018
Publication
Solutions that simulate hydrometallurgical base metal process streams with high nickel (Ni) and minor platinum (Pt) concentrations were used to create Pt/Ni nanoparticles on TiO2 nanotube surfaces. For this electrochemical deposition – redox replacement (EDRR) was used that also allowed to control the nanoparticle size density and Pt/Ni content of the deposited nanoparticles. The Pt/Ni nanoparticle decorated titanium dioxide nanotubes (TiO2 nanotubes) become strongly activated for photocatalytic hydrogen (H2) evolution. Moreover EDRR facilitates nanoparticle formation without the need for any additional chemicals and is more effective than electrodeposition alone. Actually a 10000-time enrichment level of Pt took place on the TiO2 surface when compared to Pt content in the solution with the EDRR method. The results show that hydrometallurgical streams offer great potential as an alternative raw material source for industrial catalyst production when coupled with redox replacement electrochemistry.
Origin of the Catalytic Activity at Graphite Electrodes in Vanadium Flow Batteries
Jun 2021
Publication
For many electrochemical devices that use carbon-based materials such as electrolyzers supercapacitors and batteries oxygen functional groups (OFGs) are considered essential to facilitate electron transfer. Researchers implement surface-active OFGs to improve the electrocatalytic properties of graphite felt electrodes in vanadium flow batteries. Herein we show that graphitic defects and not OFGs are responsible for lowering the activation energy barrier and thus enhance the charge transfer properties. This is proven by a thermal deoxygenation procedure in which specific OFGs are removed before electrochemical cycling. The electronic and microstructural changes associated with deoxygenation are studied by quasi in situ X-ray photoelectron and Raman spectroscopy. The removal of oxygen groups at basal and edge planes improves the activity by introducing new active edge sites and carbon vacancies. OFGs hinder the charge transfer at the graphite–electrolyte interface. This is further proven by modifying the sp2 plane of graphite felt electrodes with oxygen-containing pyrene derivatives. The electrochemical evolution of OFGs and graphitic defects are studied during polarization and long-term cycling conditions. The hypothesis of increased activity caused by OFGs was refuted and hydrogenated graphitic edge sites were identified as the true reason for this increase.
Pathways to Hydrogen as an Energy Carrier
Feb 2007
Publication
When hydrogen is used as an alternative energy carrier it is very important to understand the pathway from the primary energy source to the final use of the carrier. This involves for example the understanding of greenhouse gas emissions associated with the production of hydrogen and throughout the lifecycle of a given utilization pathway as well as various energy or exergy1 efficiencies and aspects involved. This paper which is based on a talk given at the Royal Society in London assesses and reviews the various production pathways for hydrogen with emphasis on emissions energy use and energy efficiency. The paper also views some aspects of the breaking of the water molecule and examines some new emerging physical evidence which could pave the way to a new and more feasible pathway.
Link to document download on Royal Society Website
Link to document download on Royal Society Website
Multi-Tubular Reactor for Hydrogen Production CFD Thermal Design and Experimental Testing
Jan 2019
Publication
This study presents the Computational Fluid Dynamics (CFD) thermal design and experimental tests results for a multi-tubular solar reactor for hydrogen production based on the ferrite thermochemical cycle in a pilot plant in the Plataforma Solar de Almería (PSA). The methodology followed for the solar reactor design is described as well as the experimental tests carried out during the testing campaign and characterization of the reactor. The CFD model developed for the thermal design of the solar reactor has been validated against the experimental measurements with a temperature error ranging from 1% to around 10% depending on the location within the reactor. The thermal balance in the reactor (cavity and tubes) has been also solved by the CFD model showing a 7.9% thermal efficiency of the reactor. CFD results also show the percentage of reacting media inside the tubes which achieve the required temperature for the endothermic reaction process with 90% of the ferrite pellets inside the tubes above the required temperature of 900 °C. The multi-tubular solar reactor designed with aid of CFD modelling and simulations has been built and operated successfully
Spin Pinning Effect to Reconstructed Oxyhydroxide Layer on Ferromagnetic Oxides for Enhanced Water Oxidation
Jun 2021
Publication
Producing hydrogen by water electrolysis suffers from the kinetic barriers in the oxygen evolution reaction (OER) that limits the overall efficiency. With spin-dependent kinetics in OER to manipulate the spin ordering of ferromagnetic OER catalysts (e.g. by magnetization) can reduce the kinetic barrier. However most active OER catalysts are not ferromagnetic which makes the spin manipulation challenging. In this work we report a strategy with spin pinning effect to make the spins in paramagnetic oxyhydroxides more aligned for higher intrinsic OER activity. The spin pinning effect is established in oxideFM/oxyhydroxide interface which is realized by a controlled surface reconstruction of ferromagnetic oxides. Under spin pinning simple magnetization further increases the spin alignment and thus the OER activity which validates the spin effect in rate-limiting OER step. The spin polarization in OER highly relies on oxyl radicals (O∙) created by 1st dehydrogenation to reduce the barrier for subsequent O-O coupling.
Hydrogen Production from Offshore Wind Parks: Current Situation and Future Perspectives
Jun 2021
Publication
With the increase in renewable energy connected to the grid new challenges arise due to its variable supply of power. Therefore it is crucial to develop new methods of storing energy. Hydrogen can fulfil the role of energy storage and even act as an energy carrier since it has a much higher energetic density than batteries and can be easily stored. Considering that the offshore wind sector is facing significant growth and technical advances hydrogen has the potential to be combined with offshore wind energy to aid in overcoming disadvantages such as the high installation cost of electrical transmission systems and transmission losses. This paper aims to outline and discuss the main features of the integration of hydrogen solutions in offshore wind power and to offer a literature review of the current state of hydrogen production from offshore wind. The paper provides a summary of the technologies involved in hydrogen production along with an analysis of two possible hydrogen producing systems from offshore wind energy. The analysis covers the system components including hydrogen storage the system configuration (i.e. offshore vs. onshore electrolyzer) and the potential uses of hydrogen e.g. Power to Mobility Power to Power and Power to Gas.
Cogeneration of Green Hydrogen in a Cascade Hydropower Plant
Apr 2021
Publication
Hydrogen is today an indispensable feedstock in various process industries but the method of its production is mostly not in line with accepted environmental guidelines. With emerging electro-energetic systems with a large share of renewable sources hydrogen is also becoming an important energy carrier which with the possibility of storing surplus energy ensures greater stability of power system operation and energy supply. Therefore the use of electricity from renewable sources is important for the production of green hydrogen using electrolysis. The first part of the article describes the possibilities for hydrogen cogeneration in one of the run-of-river hydropower plants in Slovenia. The implementation costs of the necessary equipment for hydrogen production in the case-study power plant its production costs and the profitability of hydrogen production compared to the sale of electricity are estimated. The criteria according to which the production of hydrogen is more profitable than the sale of electricity at current prices and guaranteed sales is also defined. In the second part of the article a scenario for the use of hydrogen for heating and mobility needs in the nearby local community is presented. For the regular supply of hydrogen in the range of up to 30 kg/h the necessary investment costs for the installation of the appropriate equipment in the hydropower plant are calculated along with an estimation of the payback period of the investment.
Techno-economic calculations of small-scale hydrogen supply systems for zero emission transport in Norway
Jun 2019
Publication
In Norway where nearly 100% of the power is hydroelectric it is natural to consider water electrolysis as the main production method of hydrogen for zero-emission transport. In a start-up market with low demand for hydrogen one may find that small-scale WE-based hydrogen production is more cost-efficient than large-scale production because of the potential to reach a high number of operating hours at rated capacity and high overall system utilization rate. Two case studies addressing the levelized costs of hydrogen in local supply systems have been evaluated in the present work: (1) Hydrogen production at a small-scale hydroelectric power plant (with and without on-site refuelling) and (2) Small hydrogen refuelling station for trucks (with and without on-site hydrogen production). The techno-economic calculations of the two case studies show that the levelized hydrogen refuelling cost at the small-scale hydroelectric power plant (with a local station) will be 141 NOK/kg while a fleet of 5 fuel cell trucks will be able to refuel hydrogen at a cost of 58 NOK/kg at a station with on-site production or 71 NOK/kg at a station based on delivered hydrogen. The study shows that there is a relatively good business case for local water electrolysis and supply of hydrogen to captive fleets of trucks in Norway particularly if the size of the fleet is sufficiently large to justify the installation of a relatively large water electrolyzer system (economies of scale). The ideal concept would be a large fleet of heavy-duty vehicles (with a high total hydrogen demand) and a refuelling station with nearly 100% utilization of the installed hydrogen production capacity.
Life-cycle Assessment of Hydrogen Technologies with the Focus on EU Critical Raw Materials and End-of-life Strategies
Aug 2020
Publication
We present the results of a life-cycle assessment (LCA) for the manufacturing and end-of-life (EoL) phases of the following fuel-cell and hydrogen (FCH) technologies: alkaline water electrolyser (AWE) polymer-electrolyte-membrane water electrolyser (PEMWE) high-temperature (HT) and low-temperature (LT) polymer-electrolyte-membrane fuel cells (PEMFCs) together with the balance-of-plant components. New life-cycle inventories (LCIs) i.e. material inputs for the AWE PEMWE and HT PEMFC are developed whereas the existing LCI for the LT PEMFC is adopted from a previous EU-funded project. The LCA models for all four FCH technologies are created by modelling the manufacturing phase followed by defining the EoL strategies and processes used and finally by assessing the effects of the EoL approach using environmental indicators. The effects are analysed with a stepwise approach where the CML2001 assessment method is used to evaluate the environmental impacts. The results show that the environmental impacts of the manufacturing phase can be substantially reduced by using the proposed EoL strategies (i.e. recycled materials being used in the manufacturing phase and replacing some of the virgin materials). To point out the importance of critical materials (in this case the platinum-group metals or PGMs) and their recycling strategies further analyses were made. By comparing the EoL phase with and without the recycling of PGMs an increase in the environmental impacts is observed which is much greater in the case of both fuel-cell systems because they contain a larger quantity of PGMs.
Opportunities and Challenges for Thermally Driven Hydrogen Production Using Reverse Electrodialysis System
Jul 2019
Publication
Ongoing and emerging renewable energy technologies mainly produce electric energy and intermittent power. As the energy economy relies on banking energy there is a rising need for chemically stored energy. We propose heat driven reverse electrodialysis (RED) technology with ammonium bicarbonate (AmB) as salt for producing hydrogen. The study provides the authors’ perspective on the commercial feasibility of AmB RED for low grade waste heat (333 K–413 K) to electricity conversion system. This is to our best of knowledge the only existing study to evaluate levelized cost of energy of a RED system for hydrogen production. The economic assessment includes a parametric study and a scenario analysis of AmB RED system for hydrogen production. The impact of various parameters including membrane cost membrane lifetime cost of heating inter-membrane distance and residence time are studied. The results from the economic study suggests RED system with membrane cost less than 2.86 €/m2 membrane life more than 7 years and a production rate of 1.19 mol/m2/h or more are necessary for RED to be economically competitive with the current renewable technologies for hydrogen production. Further salt solubility residence time and inter-membrane distance were found to have impact on levelized cost of hydrogen LCH. In the present state use of ammonium bicarbonate in RED system for hydrogen production is uneconomical. This may be attributed to high membrane cost low (0.72 mol/m2/h) hydrogen production rate and large (1281436 m2) membrane area requirements. There are three scenarios presented the present scenario market scenario and future scenario. From the scenario analysis it is clear that membrane cost and membrane life in present scenario controls the levelized cost of hydrogen. In market scenario and future scenario the hydrogen production rate (which depends on membrane properties inter-membrane distance etc.) the cost of regeneration system and the cost of heating controls the levelized cost of hydrogen. For a thermally driven RED system to be economically feasible the membrane cost not more than 20 €/m2; hydrogen production rate of 3.7 mol/m2/h or higher and cost of heating not more than 0.03 €/kWh for low grade waste heat to hydrogen production.
Evaluation of Sorbents for High Temperature Removal of Tars, Hydrogen Sulphide, Hydrogen Chloride and Ammonia from Biomass-derived Syngas by Using Aspen Plus
Jan 2020
Publication
Biomass gasification is a promising technology to produce secondary fuels or heat and power offering considerable advantages over fossil fuels. An important aspect in the usage of producer gas is the removal of harmful contaminants from the raw syngas. Thus the object of this study is the development of a simulation model for a gasifier including gas clean-up for which a fluidized-bed gasifier for biomass-derived syngas production was considered based on a quasi-equilibrium approach through Gibbs free energy minimisation and including an innovative hot gas cleaning constituted by a combination of catalyst sorbents inside the gasification reactor catalysts in the freeboard and subsequent sorbent reactors by using Aspen Plus software. The gas cleaning chain simulates the raw syngas clean-up for several organic and inorganic contaminants i.e. toluene benzene naphthalene hydrogen sulphide hydrogen chloride and ammonia. The tar and inorganic contaminants final values achieved are under 1 g/Nm3 and 1 ppm respectively.
The Merit and the Context of Hydrogen Production from Water and Its Effect on Global CO2 Emission
Feb 2022
Publication
For a green economy to be possible in the near future hydrogen production from water is a sought-after alternative to fossil fuels. It is however important to put things into context with respect to global CO2 emission and the role of hydrogen in curbing it. The present world annual production of hydrogen is about 70 million metric tons of which almost 50% is used to make ammonia NH3 (that is mostly used for fertilizers) and about 15% is used for other chemicals [1]. The hydrogen produced worldwide is largely made by steam CH4 reforming (SMR) which is one of the most energy-intensive processes in the chemical industry [2]. It releases based on reaction stoichiometry 5.5 kg of CO2 per 1 kg of H2 (CH4+ 2 H2O → CO2 + 4 H2). When the process itself is taken into account in addition the production [3] becomes about 9 kg of CO2 per kg of H2 and this ratio can be as high as 12 [4]. This results in the production of about one billion tons/year of CO2. The world annual CO2 emission from fossil fuels is however much larger: it is about 36 billion tons of which roughly 25% is emitted while generating electricity and heat 20% due to transport activity and 20% from other industrial processes. Because of the link between global warming and CO2 emissions there is an increasing move towards finding alternative approaches for energy vectors and their applications.
Shining the Light on Clean Hydrogen
Jun 2021
Publication
Clean hydrogen:
- What's driving the excitement?
- Will hydrogen stay on the main stage of the energy transition?
- What is the market for clean hydrogen today?
Catalyst Engineering for Electrochemical Energy Conversion from Water to Water: Water Electrolysis and the Hydrogen Fuel Cell
May 2020
Publication
In the context of the current serious problems related to energy demand and climate change substantial progress has been made in developing a sustainable energy system. Electrochemical hydrogen–water conversion is an ideal energy system that can produce fuels via sustainable fossil-free pathways. However the energy conversion efficiency of two functioning technologies in this energy system—namely water electrolysis and the fuel cell—still has great scope for improvement. This review analyzes the energy dissipation of water electrolysis and the fuel cell in the hydrogen–water energy system and discusses the key barriers in the hydrogen- and oxygen-involving reactions that occur on the catalyst surface. By means of the scaling relations between reactive intermediates and their apparent catalytic performance this article summarizes the frameworks of the catalytic activity trends providing insights into the design of highly active electrocatalysts for the involved reactions. A series of structural engineering methodologies (including nanoarchitecture facet engineering polymorph engineering amorphization defect engineering element doping interface engineering and alloying) and their applications based on catalytic performance are then introduced with an emphasis on the rational guidance from previous theoretical and experimental studies. The key scientific problems in the electrochemical hydrogen–water conversion system are outlined and future directions are proposed for developing advanced catalysts for technologies with high energy-conversion efficiency.
Multi-Objective Optimal Design of a Hydrogen Supply Chain Powered with Agro-Industrial Wastes from the Sugarcane Industry: A Mexican Case Study
Jan 2022
Publication
This paper presents an optimization modeling approach to support strategic planning for designing hydrogen supply chain (HSC) networks. The energy source for hydrogen production is proposed to be electricity generated at Mexican sugar factories. This study considers the utilization of existing infrastructure in strategic areas of the country which brings several advantages in terms of possible solutions. This study aims to evaluate the economic and environmental implications of using biomass wastes for energy generation and its integration to the national energy grid where the problem is addressed as a mixed-integer linear program (MILP) adopting maximization of annual profit and minimization of greenhouse gas emissions as optimization criteria. Input data is provided by sugar companies and the national transport and energy information platform and were represented by probability distributions to consider variability in key parameters. Independent solutions show similarities in terms of resource utilization while also significant differences regarding economic and environmental indicators. Multi-objective optimization was performed by a genetic algorithm (GA). The optimal HSC network configuration is selected using a multi-criteria decision technique i.e. TOPSIS. An uncertainty analysis is performed and main economic indicators are estimated by investment assessment. Main results show the trade-off interactions between the HSC elements and optimization criteria. The average internal rate of return (IRR) is estimated to be 21.5% and average payback period is 5.02 years.
Low-carbon Hydrogen Via Integration of Steam Methane Reforming with Molten Carbonate Fuel Cells at Low Fuel Utilization
Feb 2021
Publication
Hydrogen production is critical to many modern chemical processes – ammonia synthesis petroleum refining direct reduction of iron and more. Conventional approaches to hydrogen manufacture include steam methane reforming and autothermal reforming which today account for the lion's share of hydrogen generation. Without CO2 capture these processes emit about 8.7 kg of CO2 for each kg of H2 produced. In this study a molten carbonate fuel cell system with CO2 capture is proposed to retrofit the flue gas stream of an existing Steam Methane Reforming plant rated at 100000 Nm3 h−1 of 99.5% pure H2. The thermodynamic analysis shows direct CO2 emissions can be reduced by more than 95% to 0.4 to 0.5 kg CO2 /kg H2 while producing 17% more hydrogen (with an increase in natural gas input of approximately 37%). Because of the additional power and hydrogen generation of the carbonate fuel cell the efficiency debit associated with CO2 capture is quite small reducing the SMR efficiency from 76.6% without capture to 75.6% with capture. In comparison the use of standard amine technology for CO2 capture reduces the efficiency below 70%. This demonstrates the synergistic nature of the carbonate fuel cells which can reform natural gas to H2 while simultaneously capturing CO2 from the SMR flue gas and producing electricity giving rise to a total system with very low emissions yet high efficiency.
Design and Cost Considerations for Practical Solar-hydrogen Generators
Oct 2014
Publication
Solar-hydrogen generation represents a promising alternative to fossil fuels for the large-scale implementation of a clean-fuel transportation infrastructure. A significant amount of research resources has been allocated to the development of photoelectrochemical components (i.e. photovoltaic and water splitting catalysts) that are able to spontaneously split water in the presence of solar irradiation which has led to major advances in the solar-fuels field. At the same time only limited attention has been given to understanding the key aspects that drive economically viable solar-fuel generators. This study presents a generalized approach to understand the economic factors behind the design of solar-hydrogen generators composed of photovoltaic components integrated with water electrolyzers. It evaluates the underpinning effects of the material selection for the light absorption and water splitting components on the cost of the generated fuel ($ per Kg of H2). The results presented in this work provide insights into important engineering aspects related to the sizing of devices and the use of light concentration components that when optimized can lead to costs below $2.90 per kilogram of hydrogen after compression and distribution. Most significantly the analysis demonstrates that the cost of hydrogen is defined primarily by the light-absorbing component (up to 97% of the cost) while the material selection for the electrolysis components has to a large extent minor effects. The findings presented here can help direct research and development efforts towards the fabrication of deployable solar-hydrogen generators that are cost competitive with commercial energy sources.
Magnetron Sputter Deposited NiCu Alloy Catalysts for Production of Hydrogen Through Electrolysis in Alkaline Water
Jul 2018
Publication
NiCu alloy catalysts with varying composition for electrolysis in alkaline water have been prepared by DC magnetron co-sputtering under Ar gas environment at substrate bias of 60 V. Nanocrystallinity lattice parameters and grain size of the NiCu alloys have been measured by grazing incidence X-ray diffraction (GIXRD). Elemental and microstructural analysis of the NiCu alloy have been done by field emission scanning electron microscopy (FESEM) as well as transmission electron microscopy (TEM). To analyze the NiCu alloys activity towards hydrogen evolution reaction (HER) cyclic voltammetry measurements have been done in a 6 M KOH at room temperature and further HER activities have been correlated with the varying Cu concentration in NiCu alloy catalysts.
Highly Selective Porous Separator with Thin Skin Layer for Alkaline Water Electrolysis
Feb 2022
Publication
Advanced porous separators with thin selective skin layers to reduce the hydrogen permeation are developed for applications in alkaline water electrolysis. A thin skin layer based on crosslinked polyvinyl alcohol (cPVA) is fabricated on a porous substrate by a facile and scalable ultrasonic spray coating process. As the number of ultrasonic spraying cycles increases the resulting separator demonstrates a decrease in the large-diameter pore fraction an increase in the bubble-point pressure and a reduction in the hydrogen permeability without a significant increase in the areal resistance. As a result the optimized separator with a cPVA skin layer combines a low ionic resistance of 0.267 Ω cm2 a high bubble point pressure of 2.71 bar and a low hydrogen permeability of 1.12 × 10− 11 mol cm− 2 s − 1 bar− 1 . The electrolytic cell assembled with cPVAZ-30 achieves current densities of 861 mA cm− 2 and 1890 mA cm− 2 at 2.0 V and 2.6 V respectively in a 30 wt% KOH electrolyte solution at 80 ◦C.
Effect of Syngas Fuel Compositions on the Occurrence of Instability of Laminar Diffusion Flame
Dec 2020
Publication
The paper presents a numerical investigation of the critical roles played by the chemical compositions of syngas on laminar diffusion flame instabilities. Three different flame phenomena – stable flickering and tip-cutting – are formulated by varying the syngas fuel rate from 0.2 to 1.4 SLPM. Following the satisfactory validation of numerical results with Darabkhani et al. [1] the study explored the consequence of each species (H2 CO CH4 CO2 N2) in the syngas composition. It is found that low H2:CO has a higher level of instability which however does not rise any further when the ratio is less than 1. Interestingly CO encourages the heat generation with less fluctuation while H2 plays another significant role in the increase of flame temperature and its fluctuation. Diluting CH4 into syngas further increases the instability level as well as the fluctuation of heat generation significantly. However an opposite effect is found from the same action with either CO2 or N2. Finally considering the heat generation and flame stability the highest performance is obtained from 25%H2+75%CO (81 W) followed by EQ+20%CO2 and EQ+20%N2 (78 W).
A Critical Review on the Principles, Applications, and Challenges of Waste-to-hydrogen Technologies
Sep 2020
Publication
Hydrogen sourced from energy recovery processes and conversion of waste materials is a method of providing both a clean fuel and a sustainable waste management alternative to landfill and incineration. The question is whether waste-to–hydrogen can become part of the zero-carbon future energy mix and serve as one of the cleaner hydrogen sources which is economically viable and environmentally friendly. This work critically assessed the potential of waste as a source of hydrogen production via various thermochemical (gasification and pyrolysis) and biochemical (fermentation and photolysis) processes. Research has shown hydrogen production yields of 33.6 mol/kg and hydrogen concentrations of 82% from mixed waste feedstock gasification. Biochemical methods such as fermentation can produce hydrogen up to 418.6 mL/g. Factors including feedstock quality process requirements and technology availability were reviewed to guide technology selection and system design. Current technology status and bottlenecks were discussed to shape future development priorities. These bottlenecks include expensive production and operation processes heterogeneous feedstock low process efficiencies inadequate management and logistics and lack of policy support. Improvements to hydrogen yields and production rates are related to feedstock processing and advanced energy efficiency processes such as torrefaction of feedstock which has shown thermal efficiency of gasification up to 4 MJ/kg. This will affect the economic feasibility and concerns around required improvements to bring the costs down to allow waste to viewed as a serious competitor for hydrogen production. Recommendations were also made for financially competitive waste-to-hydrogen development to be part of a combined solution for future energy needs.
Catalytic and Photocatalytic Electrospun Nanofibers for Hydrogen Generation from Ammonia Borane Complex: A Review
Jul 2021
Publication
Hydrogen (H2) is a promising renewable energy source that can replace fossil fuels since it can solve several environmental and economic issues. However the widespread usage of H2 is constrained by its storage and safety issues. Many researchers consider solid materials with an excellent capacity for H2 storage and generation as the solution for most H2-related issues. Among solid materials ammonia borane (abbreviated hereafter as AB) is considered one of the best hydrogen storage materials due to its extraordinary H2 content and small density. However the process must be conducted in the presence of efficient catalysts to obtain a reasonable amount of generated H2. Electrospun nanofibrous catalysts are a new class of efficient catalysts that involves the usage of polymers. Here a comprehensive review of the ceramic-supported electrospun NF catalysts for AB hydrolysis is presented with a special focus on catalytic and photolytic performance and preparation steps. Photocatalytic AB hydrolysis was discussed in detail due to its importance and promising results. AB photocatalytic hydrolysis mechanisms under light were also explained. Electrospun catalysts show excellent activity for AB hydrolysis with good recyclability. Kinetics studies show that the AB hydrolysis reaction is independent of AB concentration and the first-order reaction of NF catalysts.
Rising To the Challenge of a Hydrogen Economy: The Outlook for Emerging Hydrogen Value Chains, From Production to Consumption
Jul 2021
Publication
For many a large-scale hydrogen economy is essential to a a clean energy future with three quarters of the more than 1100 senior energy professionals we surveyed saying Paris Agreement targets will not be possible without it.
DNV’s research Rising to the challenge of a hydrogen economy explores the outlook for emerging hydrogen value chains from production to consumption. It combines the wider view from the energy industry with commentary from business leaders and experts. Our research finds that the challenge is not in the ambition but in changing the timeline: from hydrogen on the horizon to hydrogen in our homes businesses and transport systems.
We see that the energy industry is rising to this challenge. By 2025 almost half (44%) of energy companies globally involved in hydrogen expect it to account for more than a tenth of their revenue rising to 73% of companies by 2030 – up significantly from just 8% of companies today. The research identifies infrastructure and cost as two of the biggest hurdles while the right regulations are deemed the most powerful enabler followed by carbon pricing. Proving the safety case will also be key to scaling the hydrogen economy.
Download your complimentary copy of DNV’s latest hydrogen research at their website link
DNV’s research Rising to the challenge of a hydrogen economy explores the outlook for emerging hydrogen value chains from production to consumption. It combines the wider view from the energy industry with commentary from business leaders and experts. Our research finds that the challenge is not in the ambition but in changing the timeline: from hydrogen on the horizon to hydrogen in our homes businesses and transport systems.
We see that the energy industry is rising to this challenge. By 2025 almost half (44%) of energy companies globally involved in hydrogen expect it to account for more than a tenth of their revenue rising to 73% of companies by 2030 – up significantly from just 8% of companies today. The research identifies infrastructure and cost as two of the biggest hurdles while the right regulations are deemed the most powerful enabler followed by carbon pricing. Proving the safety case will also be key to scaling the hydrogen economy.
Download your complimentary copy of DNV’s latest hydrogen research at their website link
Hydrogen Production by Steam Reforming of Ethanol on Rh-Pt Catalysts: Influence of CeO2, ZrO2, and La2O3 as Supports
Nov 2015
Publication
CeO2- ZrO2- and La2O3-supported Rh-Pt catalysts were tested to assess their ability to catalyze the steam reforming of ethanol (SRE) for H2 production. SRE activity tests were performed using EtOH:H2O:N2 (molar ratio 1:3:51) at a gaseous space velocity of 70600 h−1 between 400 and 700 °C at atmospheric pressure. The SRE stability of the catalysts was tested at 700 °C for 27 h time on stream under the same conditions. RhPt/CeO2 which showed the best performance in the stability test also produced the highest H2 yield above 600 °C followed by RhPt/La2O3 and RhPt/ZrO2. The fresh and aged catalysts were characterized by TEM XPS and TGA. The higher H2 selectivity of RhPt/CeO2 was ascribed to the formation of small (~5 nm) and stable particles probably consistent of Rh-Pt alloys with a Pt surface enrichment. Both metals were oxidized and acted as an almost constant active phase during the stability test owing to strong metal-support interactions as well as the superior oxygen mobility of the support. The TGA results confirmed the absence of carbonaceous residues in all the aged catalysts.
Review of Power-to-Gas Projects in Europe
Nov 2018
Publication
Core of the Power-to-Gas (PtG) concept is the utilization of renewable electricity to produce hydrogen via water electrolysis. This hydrogen can be used directly as final energy carrier or can be converted to e.g. methane synthesis gas liquid fuels electricity or chemicals. To integrate PtG into energy systems technical demonstration and systems integration is of mayor importance. In total 128 PtG research and demonstration projects are realized or already finished in Europe to analyze these issues by May 2018. Key of the review is the identification and assessment of relevant projects regarding their field of application applied processes and technologies for electrolysis type of methanation capacity location and year of commissioning. So far main application for PtX is the injection of hydrogen or methane into the natural gas grid for storing electricity from variable renewable energy sources. Producing fuels for transport is another important application of PtX. In future PtX gets more important for refineries to lower the carbon food print of the products.
Progress in Biofuel Production from Gasification
May 2017
Publication
Biofuels from biomass gasification are reviewed here and demonstrated to be an attractive option. Recent progress in gasification techniques and key generation pathways for biofuels production process design and integration and socio-environmental impacts of biofuel generation are discussed with the goal of investigating gasification-to-biofuels’ credentials as a sustainable and eco-friendly technology. The synthesis of important biofuels such as bio-methanol bio-ethanol and higher alcohols bio-dimethyl ether Fischer Tropsch fuels bio-methane bio-hydrogen and algae-based fuels is reviewed together with recent technologies catalysts and reactors. Significant thermodynamic studies for each biofuel are also examined. Syngas cleaning is demonstrated to be a critical issue for biofuel production and innovative pathways such as those employed by Choren Industrietechnik Germany and BioMCN the Netherlands are shown to allow efficient methanol generation. The conversion of syngas to FT transportation fuels such as gasoline and diesel over Co or Fe catalysts is reviewed and demonstrated to be a promising option for the future of biofuels. Bio-methane has emerged as a lucrative alternative for conventional transportation fuel with all the advantages of natural gas including a dense distribution trade and supply network. Routes to produce H2 are discussed though critical issues such as storage expensive production routes with low efficiencies remain. Algae-based fuels are in the research and development stage but are shown to have immense potential to become commercially important because of their capability to fix large amounts of CO2 to rapidly grow in many environments and versatile end uses. However suitable process configurations resulting in optimal plant designs are crucial so detailed process integration is a powerful tool to optimize current and develop new processes. LCA and ethical issues are also discussed in brief. It is clear that the use of food crops as opposed to food wastes represents an area fraught with challenges which must be resolved on a case by case basis.
Cross-regional Drivers for CCUS Deployment
Jul 2020
Publication
CO2 capture utilization and storage (CCUS) is recognized as a uniquely important option in global efforts to control anthropogenic greenhouse-gas (GHG) emissions. Despite significant progress globally in advancing the maturity of the various component technologies and their assembly into full-chain demonstrations a gap remains on the path to widespread deployment in many countries. In this paper we focus on the importance of business models adapted to the unique technical features and sociopolitical drivers in different regions as a necessary component of commercial scale-up and how lessons might be shared across borders. We identify three archetypes for CCUS development—resource recovery green growth and low-carbon grids—each with different near-term issues that if addressed will enhance the prospect of successful commercial deployment. These archetypes provide a framing mechanism that can help to translate experience in one region or context to other locations by clarifying the most important technical issues and policy requirements. Going forward the archetype framework also provides guidance on how different regions can converge on the most effective use of CCUS as part of global deep-decarbonization efforts over the long term.
Techno-economic Analysis on Renewable Energy Via Hydrogen, Views from Macro and Micro Scopes
Mar 2019
Publication
This paper addresses from both macro- and micro- areal coverage in introducing hydrogen system in terms of cost and performance where the produced hydrogen from surplus photovoltaic (PV) power is stored. Feed-in tariff in Japan had successful achievement for great expansion of renewable energy systems (RES) causing problematic operation due to excess power by overcapacity of RES. One of the candidate approaches to overcome this surplus energy by RES is Power to gas (P2G) system using electrolysis cells (ECs) fuel cells (FCs) or co-firing in gas turbines both for energy conversion as well as power balancing. Numerous studies had been investigated on P2G however within our knowledge no study had been addressed the system from both coverages with different capacity and scales. We investigate micro level (zero emission building in our university) and macro level (Kyushu one of big regions in Japan). We describe for macro side preliminary result on economic analysis of using surplus power of RES via production and storage of hydrogen while for micro side research design.
Improving the Efficiency of PEM Electrolyzers through Membrane-Specific Pressure Optimization
Feb 2020
Publication
Hydrogen produced in a polymer electrolyte membrane (PEM) electrolyzer must be stored under high pressure. It is discussed whether the gas should be compressed in subsequent gas compressors or by the electrolyzer. While gas compressor stages can be reduced in the case of electrochemical compression safety problems arise for thin membranes due to the undesired permeation of hydrogen across the membrane to the oxygen side forming an explosive gas. In this study a PEM system is modeled to evaluate the membrane-specific total system efficiency. The optimum efficiency is given depending on the external heat requirement permeation cell pressure current density and membrane thickness. It shows that the heat requirement and hydrogen permeation dominate the maximum efficiency below 1.6 V while above the cell polarization is decisive. In addition a pressure-optimized cell operation is introduced by which the optimum cathode pressure is set as a function of current density and membrane thickness. This approach indicates that thin membranes do not provide increased safety issues compared to thick membranes. However operating an N212-based system instead of an N117-based one can generate twice the amount of hydrogen at the same system efficiency while only one compressor stage must be added.
Hydrogen Generation by Photocatalytic Reforming of Potential Biofuels: Polyols, Cyclic Alcohols, and Saccharides
Jan 2018
Publication
We have studied hydrogen gas production using photocatalysis from C2-C5 carbon chain polyols cyclic alcohols and mono and di-saccharides using palladium nanoparticles supported on a TiO2 catalyst. For many of the polyols the hydrogen evolution rate is found to be dictated by the number of hydroxyl groups and available a-hydrogens in the structure. However the rule only applies to polyols and cyclic alcohols while the sugar activity is limited by the bulky structure of those molecules. There was also evidence of ring opening in photocatalytic reforming of cyclic alcohols that involved dehydrogenation and decarbonylation of a CC bond.
The Optimization of Hybrid Power Systems with Renewable Energy and Hydrogen Generation
Jul 2018
Publication
This paper discusses the optimization of hybrid power systems which consist of solar cells wind turbines fuel cells hydrogen electrolysis chemical hydrogen generation and batteries. Because hybrid power systems have multiple energy sources and utilize different types of storage we first developed a general hybrid power model using the Matlab/SimPowerSystemTM and then tuned model parameters based on the experimental results. This model was subsequently applied to predict the responses of four different hybrid power systems for three typical loads without conducting individual experiments. Furthermore cost and reliability indexes were defined to evaluate system performance and to derive optimal system layouts. Finally the impacts of hydrogen costs on system optimization was discussed. In the future the developed method could be applied to design customized hybrid power systems.
A Review of Recent Developments in Molecular Dynamics Simulations of the Photoelectrochemical Water Splitting Process
Jun 2021
Publication
In this review we provide a short overview of the Molecular Dynamics (MD) method and how it can be used to model the water splitting process in photoelectrochemical hydrogen production. We cover classical non-reactive and reactive MD techniques as well as multiscale extensions combining classical MD with quantum chemical and continuum methods. Selected examples of MD investigations of various aqueous semiconductor interfaces with a special focus on TiO2 are discussed. Finally we identify gaps in the current state-of-the-art where further developments will be needed for better utilization of MD techniques in the field of water splitting.
Comprehensive Study on Hydrogen Production via Propane Steam Reforming Inside a Reactor
Feb 2021
Publication
In the proton exchange membrane fuel cells the required hydrogen must be produced in some way. The power generators in the path of these fuel cells generally include a steam reactor that through other fuels provides the needed energy to produce hydrogen. This study investigates a steam reactor powered by propane fuel consisting of a shell and tube heat exchanger. The shell contains a catalyst that receives the mixture of propane and steam and the tubes embedded inside the reformer contain hot gases that provide a suitable substrate for the reaction. Velocity and temperature fields inside the reformer species concentration control and reaction rate are studied. The conversion of reactants and yield of products are investigated according to the reaction rate. The results show that the hydrogen production yield can vary from 77.5 % to 92.2 %. The reaction rate can be controlled by the velocity and temperatures of the hot gases. However for the T=900 K full propane consumption is achieved at the reformer outlet.
Using Solar Power Regulation to Electrochemically Capture Carbon Dioxide: Process Integration and Case Studies
Mar 2022
Publication
This work focuses on the use of solar photovoltaic energy to capture carbon dioxide by means of a combined electrolyzer–absorption system and compares operating results obtained in two cases studies (operation during one clear and one cloudy day in March) in which real integration of solar photovoltaics electrolyzer and absorption technologies is made at the bench-scale. The system is a part of a larger process (so-called EDEN⃝R Electrochemically-based Decarbonizing ENergy) which aims to regulate solar photovoltaic energy using a reversible chloralkaline electrochemical cell. Results demonstrate the feasibility of the sequestering technology which can produce chlorine and hydrogen but also the sequestration of CO2 and its transformation into a mixture of sodium chloride bicarbonate and carbonate useful as raw matter. Efficiencies over 70% for chlorine 60% for hydrogen and 90% for sodium hydroxide were obtained. The sequestration of carbon dioxide reached 24.4 mmol CO2/Ah with an average use of 1.6 mmol NaOH/mmol CO2. Important differences are found between the performance of the system in a clear and a cloudy day which point out the necessity of regulating the dosing of the electrochemically produced sodium hydroxide to optimize the sequestration of CO2.
Renewable Hydrogen Production from Butanol: A Review
Dec 2017
Publication
Hydrogen production from butanol is a promising alternative when it is obtained from bio-butanol or bio-oil due to the higher hydrogen content compared to other oxygenates such as methanol ethanol or propanol. Catalysts and operating conditions play a crucial role in hydrogen production. Ni and Rh are metals mainly used for butanol steam reforming oxidative steam reforming and partial oxidation. Additives such as Cu can improve catalytic activity in many folds. Moreover support–metal interaction and catalyst preparation technique also play a decisive role in the stability and hydrogen production capacity of catalyst. Steam reforming technique as an option is more frequently researched due to higher hydrogen production capability in comparison to other thermochemical techniques despite its endothermic nature. The use of the oxidative steam reforming and partial oxidation has the advantages of requiring less energy and longer stability of catalysts. However the hydrogen yield is less. This article brings together and examines the latest research on hydrogen production from butanol via steam reforming oxidative steam reforming and partial oxidation reactions. In addition the review examines a few thermodynamic studies based on sorption-enhanced steam reforming and dry reforming where there is potential for hydrogen extraction.
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