Production & Supply Chain
The Route from Green H2 Production through Bioethanol Reforming to CO2 Catalytic Conversion: A Review
Mar 2022
Publication
Currently a progressively different approach to the generation of power and the production of fuels for the automotive sector as well as for domestic applications is being taken. As a result research on the feasibility of applying renewable energy sources to the present energy scenario has been progressively growing aiming to reduce greenhouse gas emissions. Following more than one approach the integration of renewables mainly involves the utilization of biomass-derived raw material and the combination of power generated via clean sources with conventional power generation systems. The aim of this review article is to provide a satisfactory overview of the most recent progress in the catalysis of hydrogen production through sustainable reforming and CO2 utilization. In particular attention is focused on the route that starting from bioethanol reforming for H2 production leads to the use of the produced CO2 for different purposes and by means of different catalytic processes passing through the water–gas shift stage. The newest approaches reported in the literature are reviewed showing that it is possible to successfully produce “green” and sustainable hydrogen which can represent a power storage technology and its utilization is a strategy for the integration of renewables into the power generation scenario. Moreover this hydrogen may be used for CO2 catalytic conversion to hydrocarbons thus giving CO2 added value.
Storage Batteries in Photovoltaic-electrochemical Device for Solar Hydrogen Production
Aug 2021
Publication
Hydrogen produced by water electrolysis and electrochemical batteries are widely considered as primary routes for the long- and short-term storage of photovoltaic (PV) energy. At the same time fast power ramps and idle periods in PV power generation may cause degradation of water splitting electrochemical (EC) cells. Implementation of batteries in PV-EC systems is a viable option for smoothening out intermittence of PV power. Notably the spreading of PV energy over the diurnal cycle reduces power of the EC cell and thus its overpotential loss. We study these potential advantages theoretically and experimentally for a simple parallel connected combination of PV EC and battery cells (PV-EC-B) operated without power management electronics. We show feasibility of the unaided operation of PV-EC-B device in a relevant duty cycle and explore how PV-EC-B system can operate at higher solar-to-hydrogen efficiency than the equivalent reference PV-EC system despite the losses caused by the battery.
Dynamic Electric Simulation Model of a Proton Exchange Membrane Electrolyzer System for Hydrogen Production
Sep 2022
Publication
An energy storage system based on a Proton Exchange Membrane (PEM) electrolyzer system which could be managed by a nanoGrid for Home Applications (nGfHA) is able to convert the surplus of electric energy produced by renewable sources into hydrogen which can be stored in pressurized tanks. The PEM electrolyzer system must be able to operate at variable feeding power for converting all the surplus of renewable electric energy into hydrogen in reasonable time. In this article the dynamic electric simulation model of a PEM electrolyzer system with its pressurized hydrogen tanks is developed in a proper calculation environment. Through the calculation code the stack voltage and current peaks to a supply power variation from the minimum value (about 56 W) to the maximum value (about 440 W) are controlled and zeroed to preserve the stack the best range of the operating stack current is evaluated and hydrogen production is monitored.
Potential Renewable Hydrogen from Curtailed Electricity to Decarbonize ASEAN’s Emissions: Policy Implications
Dec 2020
Publication
The power generation mix of the Association of Southeast Asian Nations (ASEAN) is dominated by fossil fuels which accounted for almost 80% in 2017 and are expected to account for 82% in 2050 if the region does not transition to cleaner energy systems. Solar and wind power are the most abundant energy resources but contribute negligibly to the power mix. Investors in solar or wind farms face high risks from electricity curtailment if surplus electricity is not used. Employing the policy scenario analysis of the energy outlook modelling results this paper examines the potential scalability of renewable hydrogen production from curtailed electricity in scenarios of high share of variable renewable energy in the power generation mix. The study found that ASEAN has high potential in developing renewable hydrogen production from curtailed electricity. The study further found that the falling cost of renewable hydrogen production could be a game changer to upscaling the large-scale hydrogen production in ASEAN through policy support. The results implied a future role of renewable hydrogen in energy transition to decarbonize ASEAN’s emissions.
Economic Conditions for Developing Hydrogen Production Based on Coal Gasification with Carbon Capture and Storage in Poland
Sep 2020
Publication
This study documents the results of economic assessment concerning four variants of coal gasification to hydrogen in a shell reactor. That assessment has been made using discounting methods (NPV: net present value IRR: internal rate of return) as well as indicators based on a free cash flow to firm (FCFF) approach. Additionally sensitivity analysis has been carried out along with scenario analysis in current market conditions concerning prices of hard coal lignite hydrogen and CO2 allowances as well as capital expenditures and costs related to carbon capture and storage (CCS) systems. Based on NPV results a negative economic assessment has been obtained for all the analyzed variants varying within the range of EUR −903 to −142 million although the variants based on hard coal achieved a positive IRR (5.1–5.7%) but lower than the assumed discount rates. In Polish conditions the gasification of lignite seems to be unprofitable in the assumed scale of total investment outlays and the current price of coal feedstock. The sensitivity analyses indicate that at least a 20% increase of hydrogen price would be required or a similar reduction of capital expenditures (CAPEX) and costs of operation for the best variant to make NPV positive. Analyses have also indicated that on the economic basis only the prices of CO2 allowances exceeding EUR 40/Mg (EUR 52/Mg for lignite) would generate savings due to the availability of CCS systems.
Thermodynamic Assessment of a Hybrid Methane Cracking System for Liquified Hydrogen Production and Enhanced Oil Recovery Using CO2
Oct 2022
Publication
Hydrogen fuel production from methane cracking is a cleaner process compared to steam methane reforming due to zero greenhouse gas emissions. Carbon black that is co-produced is valuable and can be marketed to other industries. As this is a high-temperature process using solar energy can further improve its sustainability. In this study an integrated solar methane cracking system is proposed and the efficient utilization of the hydrogen and carbon products is explored. The carbon by-product is used in a direct carbon fuel cell and oxy- combustion. These processes eliminate the need for carbon capture technologies as they produce pure CO2 exhaust streams. The CO2 produced from the systems is used for enhanced oil recovery to produce crude oil. The produced turquoise hydrogen is liquified to make it suitable for exportation. The process is simulated on Aspen Plus® and its energy and exergy efficiencies are evaluated by carrying out a detailed thermodynamic analysis. A reservoir simulation is used to study the amount of oil that can be produced using the captured CO2. The overall system is studied for oil production over 20 years and energy and exergy of efficiencies 42.18% and 40.18% respectively were found. Enhanced oil recovery improves the recovery rate from 24.8% to 64.3%.
Dynamic Emulation of a PEM Electrolyzer by Time Constant Based Exponential Model
Feb 2019
Publication
The main objective of this paper is to develop a dynamic emulator of a proton exchange membrane (PEM) electrolyzer (EL) through an equivalent electrical model. Experimental investigations have highlighted the capacitive effect of EL when subjecting to dynamic current profiles which so far has not been reported in the literature. Thanks to a thorough experimental study the electrical domain of a PEM EL composed of 3 cells has been modeled under dynamic operating conditions. The dynamic emulator is based on an equivalent electrical scheme that takes into consideration the dynamic behavior of the EL in cases of sudden variation in the supply current. The model parameters were identified for a suitable current interval to consider them as constant and then tested with experimental data. The obtained results through the developed dynamic emulator have demonstrated its ability to accurately replicate the dynamic behavior of a PEM EL.
Gasification of Solid Fuels (Coal, Biomass and MSW): Overview, Challenges and Mitigation Strategies
Jun 2022
Publication
Currently hydrogen energy is the most promising energy vector while gasification is one of the major routes for its production. However gasification suffers from various issues including slower carbon conversion poor syngas quality lower heating value and higher emissions. Multiple factors affect gasification performance such as the selection of gasifiers feedstock’s physicochemical properties and operating conditions. In this review the status of gasification key gasifier technologies and the effect of solid-fuel (i.e. coal biomass and MSW) properties on gasification performance are reviewed critically. Based on the current review the co-gasification of coal biomass and solid waste along with a partial utilisation of CO2 as a reactant are suggested. Furthermore a technological breakthrough in carbon capture and sequestration is needed to make it industrially viable
A Promising Cobalt Catalyst for Hydrogen Production
Mar 2022
Publication
In this work a metal cobalt catalyst was synthesized and its activity in the hydrogen production process was tested. The substrates were water and ethanol. Activity tests were conducted at a temperature range of 350–600 °C water to ethanol molar ratio of 3 to 5 and a feed flow of 0.4 to 1.2 mol/h. The catalyst had a specific surface area of 1.75 m2/g. The catalyst was most active at temperatures in the range of 500–600 °C. Under the most favorable conditions the ethanol conversion was 97% the hydrogen production efficiency was 4.9 mol (H2)/mol(ethanol) and coke production was very low (16 mg/h). Apart from hydrogen and coke CO2 CH4 CO and traces of C2H2 and C2H4 were formed.
Hollow CdS-Based Photocatalysts
Oct 2020
Publication
In recent years photocatalytic technology driven by solar energy has been extensively investigated to ease energy crisis and environmental pollution. Nevertheless efficiency and stability of photocatalysts are still unsatisfactory. To address these issues design of advanced photocatalysts is important. Cadmium sulphide (CdS) nanomaterials are one of the promising photocatalysts. Among them hollow-structured CdS featured with enhanced light absorption ability large surface area abundant active sites for redox reactions and reduced diffusion distance of photogenerated carriers reveals a broad application prospect. Herein main synthetic strategies and formation mechanism of hollow CdS photocatalysts are summarized. Besides we comprehensively discuss the current development of hollow-structured CdS nanomaterials in photocatalytic applications including H2 production CO2 reduction and pollutant degradation. Finally brief conclusions and perspectives on the challenges and future directions for hollow CdS photocatalysts are proposed.
Electrical Double Layer Mechanism Analysis of PEM Water Electrolysis for Frequency Limitation of Pulsed Currents
Nov 2021
Publication
This paper proposes a method for improving hydrogen generation using pulse current in a proton exchange membrane-type electrolyzer (PEMEL). Traditional methods of electrolysis using direct current are known as the simplest approach to produce hydrogen. However it is highly dependent on environmental variables such as the temperature and catalyst used to enhance the rate of electrolysis. Therefore we propose electrolysis using a pulse current that can apply several dependent variables rather than environmental variables. The proposed method overcomes the difficulties in selecting the frequency of the pulse current by deriving factors affecting hydrogen generation while changing the concentration generated by the cell interface during the pulsed water-electrolysis process. The correlation between the electrolyzer load and the frequency characteristics was analyzed and the limit value of the applicable frequency of the pulse current was derived through electrical modeling. In addition the operating characteristics of PEMEL could be predicted and the PEMEL using the proposed pulse current was verified through experiments.
Recent Developments on Hydrogen Production Technologies: State-of-the-Art Review with a Focus on Green-Electrolysis
Dec 2021
Publication
Growing human activity has led to a critical rise in global energy consumption; since the current main sources of energy production are still fossil fuels this is an industry linked to the generation of harmful byproducts that contribute to environmental deterioration and climate change. One pivotal element with the potential to take over fossil fuels as a global energy vector is renewable hydrogen; but for this to happen reliable solutions must be developed for its carbon-free production. The objective of this study was to perform a comprehensive review on several hydrogen production technologies mainly focusing on water splitting by green-electrolysis integrated on hydrogen’s value chain. The review further deepened into three leading electrolysis methods depending on the type of electrolyzer used—alkaline proton-exchange membrane and solid oxide—assessing their characteristics advantages and disadvantages. Based on the conclusions of this study further developments in applications like the efficient production of renewable hydrogen will require the consideration of other types of electrolysis (like microbial cells) other sets of materials such as in anion-exchange membrane water electrolysis and even the use of artificial intelligence and neural networks to help design plan and control the operation of these new types of systems.
Operation Potential Evaluation of Multiple Hydrogen Production and Refueling Integrated Stations Under DC Interconnected Environment
Feb 2022
Publication
Hydrogen production and refueling integrated station can play an important role in the development of hydrogen transportation and fuel cell vehicles and actively promote the energy transformation. By using DC system for hydrogen production and refueling the conversion links can be reduced and the system efficiency can be effectively improved. In this paper a new scheme of DC interconnection for hydrogen production and refueling integrated station is proposed and the modular modeling and operation capability evaluation method are proposed including the characteristic analysis of integrated station the modular modeling and evaluation method for multiple integrated stations under DC interconnection. The DC interconnection system of five integrated stations is constructed and operation capability improvement of integrated stations after adopting the innovative DC interconnection scheme is analyzed. On this basis the system simulation model based on MATLAB/Simulink and physical test platform are built to verify the effectiveness of the theoretical analysis.
Implementation of Transition Metal Phosphides as Pt-Free Catalysts for PEM Water Electrolysis
Mar 2022
Publication
Proton Exchange Membrane (PEM) water electrolysis (WE) produces H2 with a high degree of purity requiring only water and energy. If the energy is provided from renewable energy sources it releases “Green H2” a CO2 -free H2 . PEMWE uses expensive and rare noble metal catalysts which hinder their use at a large industrial scale. In this work the electrocatalytic properties of Transition Metal Phosphides (TMP) catalysts supported on Carbon Black (CB) for Hydrogen Evolution Reaction (HER) were investigated as an alternative to Platinum Group Metals. The physico-chemical properties and catalytic performance of the synthesized catalysts were characterized. In the ex situ experiments the 25% FeP/CB 50% FeP/CB and 50% CoP/CB with overpotentials of −156.0 −165.9 and −158.5 mV for a current density of 100 mA cm−2 showed the best catalytic properties thereby progressing to the PEMWE tests. In those tests the 50% FeP/CB required an overpotential of 252 mV for a current density of 10 mA cm−2 quite close to the 220 mV of the Pt catalyst. This work provides a proper approach to the synthesis and characterization of TMP supported on carbon materials for the HER paving the way for further research in order to replace the currently used PGM in PEMWE.
Towards Net-zero Compatible Hydrogen from Steam Reformation - Techno-economic Analysis of Process Design Options
Dec 2022
Publication
Increased consumption of low-carbon hydrogen is prominent in the decarbonisation strategies of many jurisdictions. Yet prior studies assessing the current most prevalent production method steam reformation of natural gas (SRNG) have not sufficiently evaluated how process design decisions affect life cycle greenhouse gas (GHG) emissions. This techno-economic case study assesses cradle-to-gate emissions of hydrogen produced from SRNG with CO2 capture and storage (CCS) in British Columbia Canada. Four process configurations with amine-based CCS using existing technology and novel process designs are evaluated. We find that cradle-to-gate GHG emission intensity ranges from 0.7 to 2.7 kgCO2e/kgH2 – significantly lower than previous studies of SRNG with CCS and similar to the range of published estimates for hydrogen produced from renewable-powered electrolysis. The levelized cost of hydrogen (LCOH) in this study (US$1.1–1.3/kgH2) is significantly lower than published estimates for renewable-powered electrolysis.
The Challenges of Integrating the Principles of Green Chemistry and Green Engineering to Heterogeneous Photocatalysis to Treat Water and Produce Green H2
Jan 2023
Publication
Nowadays heterogeneous photocatalysis for water treatment and hydrogen production are topics gaining interest for scientists and developers from different areas such as environmental technology and material science. Most of the efforts and resources are devoted to the development of new photocatalyst materials while the modeling and development of reaction systems allowing for upscaling the process to pilot or industrial scale are scarce. In this work we present what is known on the upscaling of heterogeneous photocatalysis to purify water and to produce green H2. The types of reactors successfully used in water treatment plants are presented as study cases. The challenges of upscaling the photocatalysis process to produce green H2 are explored from the perspectives of (a) the adaptation of photoreactors (b) the competitiveness of the process and (c) safety. Throughout the text Green Chemistry and Engineering Principles are described and discussed on how they are currently being applied to the heterogeneous photocatalysis process along with the challenges that are ahead. Lastly the role of automation and high-throughput methods in the upscaling following the Green Principles is discussed.
Prospects and Technical Challenges in Hydrogen Production through Dry Reforming of Methane
Mar 2022
Publication
Environmental issues related to greenhouse gases (GHG) emissions have pushed the development of new technologies that will allow the economic production of low-carbon energy vectors such as hydrogen (H2 ) methane (CH4 ) and liquid fuels. Dry reforming of methane (DRM) has gained increased attention since it uses CH4 and carbon dioxide (CO2 ) which are two main greenhouse gases (GHG) as feedstock for the production of syngas which is a mixture of H2 and carbon monoxide (CO) and can be used as a building block for the production of fuels. Since H2 has been identified as a key enabler of the energy transition a lot of studies have aimed to benefit from the environmental advantages of DRM and to use it as a pathway for a sustainable H2 production. However there are several challenges related to this process and to its use for H2 production such as catalyst deactivation and the low H2/CO ratio of the syngas produced which is usually below 1.0. This paper presents the recent advances in the catalyst development for H2 production via DRM the processes that could be combined with DRM to overcome these challenges and the current industrial processes using DRM. The objective is to assess in which conditions DRM could be used for H2 production and the gaps in literature data preventing better evaluation of the environmental and economic potential of this process.
Pulsed-Supplied Water Electrolysis via Two-Switch Converter for PV Capacity Firming
Mar 2022
Publication
Hydrogen constitutes the only carbon-free fuel that can be used for energy conversion producing water as the only by-product. With water being one of the most abundant and inexhaustible raw materials in the world and the required electricity input being provided by renewable resources the produced hydrogen via water electrolysis constitutes a green pathway towards sustainability. In this work a hybrid PV power-to-hydrogen storage and fuel cell system is proposed to satisfy the domestic load of a residential building. Identifying alkaline as a mandatory electrolysis technology the performance of alkaline electrolysis cells is assessed considering the inclusion of a two-switch buck-boost converter. Following a comprehensive formulation with respect to each distinguished system component the balance condition at DC and AC buses is determined. The proposed configuration is evaluated taking into account PV systems of different ratings namely 3 kW 5 kW and 7 kW. Based on actual data relating to both PV generation and domestic load for the year 2020 the obtained results from the annual simulations are compared with feed-in tariff and net-metering schemes. According to the results PV capacity firming is achieved creating great opportunities for autonomy enhancement not only for electricity but also in other energy sectors.
Techno-economic Analysis of Hydrogen Electrolysis from Off-Grid Stand-Alone Photovoltaics Incorporating Uncertainty Analysis
Oct 2020
Publication
Solar-driven electrolysis of water to generate hydrogen is emerging as a viable strategy to decarbonize the global energy economy. However this direction is more expensive than traditional fossil fuel generation of hydrogen and effective pathways to lower this cost need to be identified. Here we report a Monte Carlo approach to explore a wide range of input assumptions to identify key cost drivers targets and localized conditions necessary for competitive stand-alone dedicated PV powered hydrogen electrolysis. We determine the levelized cost of hydrogen (LCOH) considering historical weather data for specific locations to model our PV system and optimize its size compared to the electrolyzer. This analysis and its methods show the potential for green hydrogen production using off-grid PV shows the merits of remote systems in areas of high solar resource and provides cost and performance targets for electrolyzer technologies.
Black TiO2 for Solar Hydrogen Conversion
Feb 2017
Publication
Titanium dioxide (TiO2 ) has been widely investigated for photocatalytic H2 evolution and photoelectrochemical (PEC) water splitting since 1972. However its wide bandgap (3.0–3.2 eV) limits the optical absorption of TiO2 for sufficient utilization of solar energy. Blackening TiO2 has been proposed as an effective strategy to enhance its solar absorption and thus the photocatalytic and PEC activities and aroused widespread research interest. In this article we reviewed the recent progress of black TiO2 for photocatalytic H2 evolution and PEC water splitting along with detailed introduction to its unique structural features optical property charge carrier transfer property and related theoretical calculations. As summarized in this review article black TiO2 could be a promising candidate for photoelectrocatalytic hydrogen generation via water splitting and continuous efforts are deserved for improving its solar hydrogen efficiency.
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