Availability,supply technology and costs of residual forest biomass for energy – A case study in northern China

In theory, China has vast potential forest resources for production of energy, but utilization on an industrial scale has been negligible. We assessed the practical possibilities and barriers for a forest energy business in a case study in northern China. The specific objectives of the study were 1) to assess the availability of forest biomass for energy production, 2) to determine feasible supply chains, and 3) to estimate the biomass fuel supply costs. Based on the case study results, the stand-level removals of the intended feedstock were low and the supply costs were relatively high. Suggestions for increasing the raw material basis, lowering the costs and further research and development were given. We conclude that although the case study area may not be promising from the feedstock point of view, the development could be started with small steps and proven technology. In order to avoid expensive mistakes further research for transfer of know-how and technology is needed.     

Rail transportation by hydrogen vs. electrification – Case study for Ontario,Canada, II: Energy supply and distribution

Locomotives offer an efficient mode of transportation when compared to buses, personal vehicles or airplanes for mass transportation over frequent intercity distances. For example, a Bombardier Regina EMU train with 272 seats and a load factor of 53% will consume under 0.07 kWh/passenger-km, which is typically much lower than corresponding values for other transportation modes in similar circumstances. European countries have invested significantly over the years in train electrification. Environmentally friendly methods of transferring power to the wheels are direct electrification and hydrogen fuel cells. Various methods to produce hydrogen for utilization with fuel cell train operation are examined in this paper.     

Comparison of the renewable transportation fuels,hydrogen and methanol formed from hydrogen,with gasoline – Engine efficiency study

The use of hydrogen derived methanol in spark-ignition engines forms a promising approach to decarbonizing transport and securing domestic energy supply. Methanol can be renewably produced from hydrogen in combination with biomass or CO₂ from the atmosphere and flue gases. From well to tank studies it appears that hydrogen derived methanol compares favourably with liquid or compressed hydrogen both in terms of production cost and energy efficiency. Since existing well to wheel studies are based on outdated technology, this paper tries to provide efficiency figures for state-of-the-art hydrogen and methanol engines using published data and measurements on our own flex-fuel engine.     

Estimating future costs of power-to-gas – a component-based approach for technological learning

Technological learning is a major aspect in the assessment of potential cost reductions for emerging energy technologies. Since the evaluation of experience curves requires the observation of production costs over several magnitudes of produced units, an early estimation of potential future technology implementation costs often presumes a certain degree of maturity. In this paper, we propose a calculation model for learning curves on the component or production process level, which allows to incorporate experience and knowledge on cost reduction potentials on a low level. This allows interchangeability between similar technologies, which is less feasible on a macro level. Additionally, the model is able to consider spill-over effects from concurrent technology usages for the inclusion of peripheral standard components for the assessment in an overall system view. The application of the model to the power-to-gas technology, especially water electrolysis, has shown, that the results are comparable to conventional approaches at the stack level, while providing transferability between different cell designs. In addition, the investigations made at the system level illustrate that the consideration of spill-over effects can be a relevant factor in the evaluation of cost reduction potentials, especially for technologies in an early commercial state with low numbers of cumulative productions.     

Integration of hydrogenation and dehydrogenation system for hydrogen storage and electricity generation – simulation study

The present study combines methylcyclohexane dehydrogenation and toluene hydrogenation systems to produce steam for power generation. Methylcyclohexane dehydrogenation requires heat input, which has been accomplished using heat, released from toluene hydrogenation system, and heat exchange with steam, produced from the steam generator. The integration of these systems results in the generation of 5 MW electricity, which is used to run the electrolysis unit. The overall process does not require an extra source of energy, decreasing the external utility requirement. Both the systems have been investigated against various catalysts for the selection of best catalyst, thus enhancing overall process efficiency. The study has been carried out using Aspen HYSYS v 9. Aspen Energy Analyzer v 9 has been used to do the energy analysis of the system. Overall plant costing has been carried out using Aspen Economic Analyzer v 9.     

Rail transportation by hydrogen vs. electrification – Case study for Ontario Canada,I: Propulsion and storage

Cities around the world are expanding their passenger train operations to address concerns with GHG pollution, noise and high costs of commuter transportation. Locomotives offer an attractive mode of transportation in terms of energy consumption per passenger kilometre of travel. This paper compares hydrogen against electrification as cleaner alternatives to power diesel locomotives. Disadvantages of electrification include the capital investment to install electrical substations and catenaries, together with a lack of flexibility for locomotives to move into other service areas not covered by electrification. This paper specifically analyzes the implementation and operation of hydrogen passenger locomotives in the GO Transit Lakeshore corridor, through Toronto, between Oshawa and Hamilton, Ontario. A sensitivity analysis is performed over a range of operational costs for a hydrogen train, with variability of feedstock prices, fuel cell power density and expected return on capital investment. Various methods of propulsion and storage are compared against electrification. The installation and operational costs in dollars per train-km are analyzed for various train scenarios and results are presented.     

A flexible techno-economic analysis tool for regional hydrogen hubs – A case study for Ireland

The increasing urgency with which climate change must be addressed has led to an unprecedented level of interest in hydrogen as a clean energy carrier. Much of the analysis of hydrogen until this point has focused predominantly on hydrogen production. This paper aims to address this by developing a flexible techno-economic analysis (TEA) tool that can be used to evaluate the potential of future scenarios where hydrogen is produced, stored, and distributed within a region. The tool takes a full year of hourly data for renewables availability and dispatch down (the sum of curtailment and constraint), wholesale electricity market prices, and hydrogen demand, as well as other user-defined inputs, and sizes electrolyser capacity in order to minimise cost. The model is applied to a number of case studies on the island of Ireland, which includes Ireland and Northern Ireland. For the scenarios analysed, the overall LCOH ranges from €2.75–3.95/kgH₂. Higher costs for scenarios without access to geological storage indicate the importance of cost-effective storage to allow flexible hydrogen production to reduce electricity costs whilst consistently meeting a set demand.     

Evaluation of the introduction of a hydrogen supply chain using a conventional gas pipeline–A case study of the Qinghai–Shanghai hydrogen supply chain

A large-scale hydrogen supply chain is an alternative for the transportation of energy generated from a renewable energy source. Utilizing this technology would drastically improve the generation of clean energy. Therefore, an analysis method to estimate the economic and environmental benefits of the introduction of a hydrogen supply chain using an existing pipeline is developed. The proposed method first estimates the energy and exergy flows in the system to calculate the overall efficiency of these quantities. Afterward, the payback period is estimated based on the overall energy efficiency using the discounted cash flow (DCF) method. The overall efficiency of the system, based on the energy analysis presented, would seem to be the final delivered electrical, fuel and useable heat energy delivered to end use divided by the input solar and wind energy. Furthermore, the environmental effects due to the introduction of the systems are evaluated considering the reduction of global warming and air pollution gases, such as CO₂ and PM2.5. The proposed analysis method was applied considering a natural gas pipeline that connects Qinghai and Shanghai. As a result, conversion ratios of 24.9% for electricity and 17.5% for heat were achieved, with the overall efficiency of the system of 42.4% based on the electricity obtained from photovoltaics. 3.02 Gt of CO₂, 104 kt of SO_x, and 134 kt of NO_x, which represent 3.3%, 0.5%, and 0.6% of the annual discharge in China, respectively, and 8.66 kt of PM2.5 would be reduced every year. Furthermore, a reduction of 953 Mt in coal consumption is expected. The payback period of the proposed system using the DCF method is 4.17 and 2.28 years for the two alternatives evaluated in this work. The cash flow of the DCF is influenced by installation cost and operation cost of equipment.     

Biofuels,electrofuels, electric or hydrogen?: A review of current and emerging sustainable aviation systems

Climate neutrality is becoming a core long-term competitiveness asset within the aviation industry, as demonstrated by the several innovations and targets set within that sector, prior to and especially after the COVID-19 crisis. Ambitious timelines are set, involving important investment decisions to be taken in a 5-years horizon time. Here, we provide an in-depth review of alternative technologies for sustainable aviation revealed to date, which we classified into four main categories, namely i) biofuels, ii) electrofuels, iii) electric (battery-based), and iv) hydrogen aviation. Nine biofuel and nine electrofuel pathways were reviewed, for which we supply the detailed process flow picturing all input, output, and co-products generated. The market uptake and use of these co-products was also investigated, along with the overall international regulations and targets for future aviation. As most of the inventoried pathways require hydrogen, we further reviewed six existing and emerging carbon-free hydrogen production technologies. Our review also details the five key battery technologies available (lithium-ion, advanced lithium-ion, solid-state battery, lithium-sulfur, lithium-air) for aviation. A semi-quantitative ranking covering environmental-, economic-, and technological performance indicators has been established to guide the selection of promising routes. The possible configuration schemes for electric propulsion systems are documented and classified as: i) battery-based, ii) fuel cell-based and iii) turboelectric configurations. Our review studied these four categories of sustainable aviation systems as modular technologies, yet these still have to be used in a hybridized fashion with conventional fossil-based kerosene. This is among others due to an aromatics content below the standardized requirements for biofuels and electrofuels, to a too low energy storage capacity in the case of batteries, or a sub-optimal gas turbine engine in the case of cryogenic hydrogen. Yet, we found that the latter was the only available option, based on the current and emerging technologies reviewed, for long-range aviation completely decoupled of fossil-based hydrocarbon fuels. The various challenges and opportunities associated with all these technologies are summarized in this study.     

Modeling of a catalytic membrane reactor for CO removal from hydrogen streams – A theoretical study

Typical industrial hydrogen streams arising from reforming processes contain about 1% of carbon monoxide (CO). For fuel cell applications hydrogen should contain less than 10 ppm of CO, since it poisons the platinum catalysts in the electrodes. Traditionally, this is carried out through a selective oxidation reactor – PROX reactor. However, the parallel oxidation of hydrogen to water should be avoided. This work proposes the use of a catalytic membrane reactor (MR) whose design is based on a CO permselective membrane containing the selective catalyst loaded in the permeate side. It is considered plug-flow pattern and segregated feed of CO and oxygen. This strategy should improve the selective oxidation, as the permselective membrane enhances the CO/H₂ ratio at the catalyst surface.     

Systematic approach for recognizing limiting factors for growth of biomethane use in transportation sector – A case study in Finland

In this paper, limiting factors for increased use of biomethane as a transportation fuel are studied. The aim of this research is to recognize and estimate the limiting factors for biomethane utilization in the transportation sector. The limiting factors are studied by using calculation models from Life cycle perspective and literature reviews. According to the results, the main limiting factors can be classified into the following categories: production potential, technology, economy or policy. For biomethane utilization in Finland, the main limiting factors seem to be the lack of distribution infrastructure in northern parts of the country and the uncertain economical feasibility for agricultural biomass producers and for vehicle owners. From the political perspective, the external costs for petrol operated vehicles are higher than for biomethane operated vehicles. Reductions from the external costs could be used by political decisions as a base to support the growth of biomethane in the transportation sector which could lead to GHG emission reductions. A similar systematic approach can also be used to study limiting factors for other transportation energy systems.     

Life cycle analysis of hydrogen – A well-to-wheels analysis for Portugal

A life cycle analysis of hydrogen is presented involving several processes of H₂ production. The main goal was to adapt the GREET 1.8c model in order to represent the European reality and more specifically the Portuguese energy sector. GEMIS model was used in order to obtain energy consumption and pollutant emissions related to the production of photovoltaic panels and wind towers, since GREET model consider zero emissions in renewable technologies. The integration between these two models generated MACV2H₂ model that was calibrated.     

Coiled-tube heat exchanger for High-Pressure Metal Hydride hydrogen storage systems – Part 1. Experimental study

This two-part study explores the development and thermal performance of a coiled-tube heat exchanger for hydrogen fuel cell storage systems utilizing High-Pressure Metal Hydride (HPMH). The primary purpose of this heat exchanger is to tackle the large amounts of heat released from the exothermic hydriding reaction that occurs when the hydrogen is charged into the storage vessel and is absorbed by the HPMH. The performance of heat exchanger was tested using 4 kg of Ti_1.1CrMn at pressures up to 280 bar. Tests were performed to assess the influence of different operating conditions on the effectiveness of the heat exchanger at removing the heat in a practical fill time (time required to complete 90% of the hydriding reaction). It is shown that distance of metal hydride particles from the coolant tube has the most dominant influence on hydriding rate, with particles closer to the tube completing their hydriding reaction sooner. Faster fill times were achieved by reducing coolant temperature and to a lesser extent by increasing pressurization rate. By comparing tests with and without coolant flow, it is shown that the heat exchanger reduces fill time by 75% while occupying only 7% of the storage pressure vessel volume. The second part of this study will present a 3D computational heat transfer model of the storage vessel and heat exchanger, and compare the model predictions to the experimental data.     

Experimental and modeling study of performance and emissions of SI engine fueled by natural gas–hydrogen mixtures

Based on CFD software and reaction kinetics software, multi-dimensional CFD Model coupled with detail reaction kinetics is built to study the combustion process in H₂/CNG Engine. Detail reaction mechanism is used to simulate the chemistry of combustion and a combustion model considering the turbulent mixing effects was also applied. To reduce the computation time, the coupled software is reprogrammed to have the function of parallel computing and the revised software is computed in a Massively Parallel Processor. The model is validated using the experiment data from a modified diesel engine. The results show: cylinder pressure from simulation has a good agreement with experiment data and CO and NO_x emission is well predicted by the model in a wide range.     

The value chain of green hydrogen for fuel cell buses – A case study for the Rhine-Main area in Germany

As an immanent necessity to reduce global greenhouse gas emissions, the energy transition poses a major challenge for the next 30 years, as it includes a cross-sectoral increase of fluctuating renewable energy production, grid extension to meet regional electricity supply and demand as well as an increase of energy storage capacity. Within the power-to-gas concept, hydrogen is considered as one of the most promising solutions.The paper presents a scenario-based bottom-up approach to analyse the hydrogen supply chain to substitute diesel with fuel cell buses in the Rhine-Main area in central Germany for the year 2025. The analysis is based on field data derived from the 6 MW power-to-gas plant “Energiepark Mainz” and the bus demonstration project “H₂-Bus Rhein-Main”. The system is modelled to run simulations on varying demand scenarios. The outcome is minimised hydrogen production costs derived from the optimal scheduling of a power-to-gas plant in terms of the demand. The assessment includes the energy procurement for hydrogen production, different hydrogen delivery options and spatial analysis of potential power-to-gas locations.     

An interval full-infinite mixed-integer programming method for planning municipal energy systems – A case study of Beijing

In this study, an interval full-infinite mixed-integer municipal-scale energy model (IFMI-MEM) is developed for planning energy systems of Beijing. IFMI-MEM is based on an integration of existing interval-parameter programming (IPP), mixed-integer linear programming (MILP) and full-infinite programming (FIP) techniques. IFMI-MEM allows uncertainties expressed as determinates, crisp interval values and functional intervals to be incorporated within a general optimization framework. It can also facilitate capacity-expansion planning for energy-production facilities within a multi-period and multi-option context. Then, IFMI-MEM is applied to a real case study of energy systems planning in Beijing. The results indicate that reasonable solutions have been generated. They are helpful for supporting (a) adjustment of the existing demand and supply patterns of energy resources, (b) facilitation of dynamic analysis for decisions of capacity expansion and/or development planning, and (c) coordination of the conflict interactions among economic cost, system efficiency, pollutant mitigation and energy-supply security.     

A feasibility study on solar-wall systems for domestic heating – An affordable solution for fuel poverty

A Solar Wall Heating (SWH) system was developed to provide low cost space heating in traditional solid stone-walled tenement buildings in Scotland. The SWH system uses the internal solid walls to store the solar heat collected during the day and heat the bedrooms during the night.A physical laboratory model with attached solar hot water system and a computational model of it were developed to investigate the dynamic performance of the system in use and test the cost benefits of iterations of its modes of use. The temperatures throughout the wall structure were measured under the variant solar input of a 24-h cycle. An unsteady state CFD model was developed and validated using the measured data and setup to test a number of key variables of the solar wall heating system in use. These included optimisation control strategies and maximisation strategies for the collection and storage of solar heat under various conditions. This paper presents the modelled results of the solar thermal storage and optimisation system and strategies for internal solid stone walls in a typical Scottish tenement flat in the Scottish climate.In addition the study analysed the solar availability, heating demand and domestic water supply of two typical dwellings based on two reliable methods: (a) a purpose built dynamic thermal model and (b) data collected in previous studies.The study demonstrated that the solar collection of current solar hot water systems can be improved upon so that, even in Scotland, more solar power can be harvested to contribute not only to domestic hot water, but also domestic space heating, particularly in buildings occupied over 24 h with heavy thermal mass. The cost analysis of the system in use suggested a 16 year payback period for such a system for a tenement flat.     

A solution to renewable hydrogen economy for fuel cell buses – A case study for Zhangjiakou in North China

Fuel cell vehicles fueled with renewable hydrogen is recognized as a life-cycle carbon-free option for the transport sector, however, the profitability of the H₂ pathway becomes a key issue for the FCV commercialization. By analyzing the actual data from the Zhangjiakou fuel cell transit bus project, this research reveals it is economically feasible to commercialize FCV in areas with abundant renewable resources. Low electricity for water electrolysis, localization of H₂ supply, and curtailed end price of H₂ refueling effectively reduce the hydrogen production, delivery and refueling cost, and render a chance for the profitability of refueling stations. After the fulfillment of the intense deployment of both vehicles and hydrogen stations for the 2022 Winter Olympics, the H₂ pathway starts to make a profit thereafter. The practices in the Zhangjiakou FCB project offer a solution to the hydrogen economy, which helps to break the chicken-egg dilemma of vehicles and hydrogen infrastructure.     

Hydrogen quality for fuel cell vehicles – A modeling study of the sensitivity of impurity content in hydrogen to the process variables in the SMR–PSA pathway

As fuel cell vehicles approach wide-scale deployment, the issue of the quality of hydrogen dispensed to the vehicles has become increasingly important. The various factors that must be considered include the effects of different contaminants on fuel cell performance and durability, the production and purification of hydrogen to meet fuel quality guidelines, and the associated costs of providing hydrogen of that quality to the fuel cell vehicles. In this paper, we describe the development of a model to track the formation and removal of several contaminants over the various steps of hydrogen production by steam-methane reforming (SMR) of natural gas, followed by purification by pressure-swing adsorption (PSA). We have used the model to evaluate the effects of setting varying levels of these contaminants in the product hydrogen on the production/purification efficiency, hydrogen recovery, and the cost of the hydrogen. The model can be used to track contaminants such as CO₂, CO, N₂, CH₄, and H₂S in the process. The results indicate that a suggested specification of 0.2 ppm CO would limit the maximum hydrogen recovery from the PSA under typical design and operating conditions. The steam-to-carbon ratio and the process pressure are found to have a significant impact on the process efficiency. Varying the CO specification from 0.1 to 1 ppm is not expected to affect the cost of hydrogen significantly, although the cost of gas analysis to comply with such stringent requirements may add 2–10 cents/kg to the cost of hydrogen.     

Spark spread – A screening parameter for combined heating and power systems

Combined heating and power (CHP) systems may be considered for installation if they produce savings over conventional systems with separate heating and power. For a CHP system with a natural gas engine as the prime mover, the difference between the price of natural gas and the price of purchased electricity, called spark spread, is an indicator as to whether a CHP system might be considered or not. The objective of this paper is to develop a detailed model, based on the spark spread, that compares the electrical energy and heat energy produced by a CHP system against the same amounts of energy produced by a traditional, or separate heating and power (SHP) system that purchases electricity from the grid. An expression for the spark spread based on the cost of the fuel and some of the CHP system efficiencies is presented in this paper as well as an expression for the payback period for a given capital cost and spark spread. The developed expressions allow determining the required spark spread for a CHP system to produce a net operational savings over the SHP in terms of the performance of system components. Results indicate that the spark spread which might indicate favorable payback varies based on the efficiencies of the CHP system components and the desired payback period. In addition, a new expression for calculating the payback period for a CHP system based on the CHP system capital cost per unit of power output and fuel cost is proposed.