Renewable biohydrogen production from straw biomass – Recent advances in pretreatment/hydrolysis technologies and future development

Straw is an abundant natural bioresource, especially in developing and agricultural countries. Bio-hydrogen production from this renewable biomass through biological methods is an active research area. Because of its distinctive characteristic of being rich in cellulose, straw has been extensively considered as a promising raw material for clean energy production. In this paper, the recent progress of bio-hydrogen production from straw was reviewed with the emphasis on the advances in pretreatment and hydrolysis technologies. The future development of straw-based biohydrogen production was also analyzed. Based on the physicochemical properties of straw biomass and mechanisms of bio-hydrogen fermentation, various pretreatment procedures have been developed to make the straw substrate more available for hydrogen-producing bacteria to realize large-scale bio-hydrogen production from straw. This review summarized the recent technologies of straw pretreatment and hydrolysis as well as elaborated on the bottlenecks in the field of straw biotransformation in great detail. Furthermore, based on the current technology status and potential, the challenges, prospects and future directions of the production methods were further proposed.     

Optimization of hybrid – ground coupled and air source – heat pump systems in combination with thermal storage

Ground coupled heat pumps are attractive solutions for cooling and heating commercial buildings due to their high efficiency and their reduced environmental impact. Two possible ideas to improve the efficiency of these systems are decoupling energy generation from energy distribution and combining different HVAC systems. Based on these two ideas, we present several HVAC configurations which combine the following equipments: a ground coupled heat pump, an air to water heat pump and a thermal storage device. These HVAC configurations are linked to an office building in a cooling dominated area in order to evaluate in these conditions the total electrical consumption of each configuration to obtain which one satisfy the thermal demand more efficiently. The results of our simulations show that the electrical energy consumption obtained when the system employs a suitable configuration is of around the 60% compared with an HVAC system driven by an air to water heat pump and around the 82% compared with an HVAC system driven by a ground coupled heat pump.     

Sustainability assessment of wood-based bioenergy – A methodological framework and a case-study

The sustainability of the utilization of wood biomass for energy and other purposes has been widely assessed in different studies. Especially discrete methods from the family of Multi-Criteria Decision Analysis (MCDA), such as Outranking methods, Multi-Attribute Utility Theory, and Analytic Hierarchy Process (AHP) are often applied. AHP is considered one of the most promising options to be used in sustainability assessments, because it is comprehensible to apply and it incorporates the preferences of decision-makers in an advanced manner. In this study, we present a theoretical multi-dimensional framework based on a modified version of AHP for assessing sustainability and apply it in a case of wood-based bioenergy production in eastern Finland. The framework includes four dimensions of sustainability and life cycle phases from the acquisition of raw material to manufacturing the final product. The production systems used in the empirical sustainability assessments are a local heat production plant, a combined heat and power production plant, and a wood pellet processing plant. Local sustainability experts identified indicators relevant at the regional scale. The impact assessment data were obtained from literature, by interviewing the managers of the bioenergy plants, and from a postal survey administered to local people. The local heat provider received the highest sustainability index; however, there were no considerable differences between the sustainability indexes. None of the bioenergy production systems can be considered the most sustainable regardless of the assumptions employed in the framework. The framework provided the basis for a quantitative, interdisciplinary approach to assess sustainability.     

Optimization of hydrogen production via coupling of the Fischer–Tropsch synthesis reaction and dehydrogenation of cyclohexane in GTL technology

In this study, a thermally-coupled reactor containing the Fischer–Tropsch synthesis reaction in the exothermic side and dehydrogenation of cyclohexane in the endothermic side has been modified using a hydrogen perm-selective membrane as the shell of the reactor to separate the produced hydrogen from the dehydrogenation process. Permeated hydrogen enters another section called permeation side to be collected by Argon, known as the sweep gas. This three-sided reactor has been optimized using differential evolution (DE) method to predict the conditions at which the reactants’ conversion and also the hydrogen recovery yield would be maximized. Minimizing the CO₂ and CH₄ yield in the reactor’s outlet as undesired products is also considered in the optimization process. To reach this goal, optimal initial molar flow rate and inlet temperature of three sides as well as pressure of the exothermic side have been calculated. The obtained results have been compared with the conventional reactor data of the Research Institute of Petroleum Industry (RIPI), the membrane dual – type reactor suggested for Fischer–Tropsch synthesis, and the membrane coupled reactor presented for methanol synthesis. The comparison shows acceptable enhancement in the reactor’s performance and that the production of hydrogen as a valuable byproduct should also be considered.     

Analysis of the potential production and the development of bioenergy in the province of Mendoza – Bio-fuels and biomass – Using geographic information systems

In this work, the partial results of the potential production of energy, starting from the biomass and the development of the crops, directed to the production of bio-fuels (Colza and Topinamur) in the North irrigation oasis of Mendoza, Argentina within the National Program of Bio-energy developed by INTA is presented.     

A 3E,hydrogen production,irrigation, and employment potential assessment of a hybrid energy system for tropical weather conditions – Combination of HOMER software,shannon entropy,and TOPSIS

The increasing threat to environmental sustainability as a result of greenhouse gas (GHG) emissions from fossil fuel base power plants has necessitated the need to find sustainable energy sources to meet the world's energy demands. This study focuses on assessing the potential of a hybrid power plant for the production of electricity, hydrogen for the production of fertilizer for agricultural activities, farmland irrigation, environmental impact as well as its employment potential in northern Ghana. The Shannon entropy weight and TOPSIS multi-criteria decision-making approach were adopted to rank and identify the optimal configuration out of five possible options for the study area. Results from the simulation show that the winning system, i.e., Hydro + Battery system would generate a total electricity of 1,095,679 kWh/year. A cost of electricity of 0.06 $/kWh with an operating cost (OC) of $18,318 was recorded for the winning system. The total produced hydrogen by the optimum configuration is 8816 kg/year at a levelized cost of hydrogen (LCOH) of 4.47 $/kg. The quantity of low-carbon fertilizer that can be produced from the produced hydrogen is also assessed. The optimum configuration also recorded an employment potential of 4 persons in 25 years. A total GHG equivalence of 383.49 metric tons of CO₂ equivalent indicating the level of emissions that will be avoided should the optimum system be used to meet the demands specified in this study was obtained.     

Life cycle assessment of nuclear-based hydrogen production via a copper–chlorine cycle: A neural network approach

A comparative environmental study is reported of nuclear-based hydrogen production using thermochemical water decomposition cycles. The investigation uses a life cycle assessment (LCA) as is an analytical tool to evaluate and reduce the environmental impact of the system or product. The LCA results are presented in terms of acidification potential and global warming potential. Since LCA often utilizes software to model and analyse the system, an artificial neural network (ANN) method can be advantageous. Here, an ANN method is applied to a nuclear-based hydrogen production system. Using an ANN method in this study eliminates the need to use LCA software separately and facilitates the determination of the impacts of altering input parameters of a system (e.g., heat, work, production capacity and plant lifetime). The neural network approach to identify the best system option, consistent with LCA software results, is developed here using ten neurons in the hidden layers.     

Optimization of multiple heaters in a vented enclosure – A combined numerical and experimental study

This paper discusses the results of an experimental and numerical study of fluid flow and heat transfer in an enclosure where multiple heaters are arranged in a staggered fashion. Experiments were carried out for Reynolds numbers, in the range 1800 ≤ Re ≤ 4500 and Grashof numbers in the range 2.5 × 10⁴ ≤ Gr ≤ 3 × 10⁵. Numerical simulations were carried out for two dimensional, steady, incompressible turbulent flow and the results of the numerical study are compared with the experimental results. The temperature distribution gives an insight into the power management among the heaters, so that the “coolest” heater can be loaded most to maximize the total heat dissipation, for a prescribed temperature excess, for all the heaters. Two methods are used to achieve the target temperature for all heaters, namely (i) trial and error method and (ii) the response surface method. The latter method was adopted, to simultaneously maximize the heat input and minimize the temperature deviation from the target temperature, by employing a composite objective function. The numerically obtained optimal solution was finally verified by carrying out experiments. The method of response surface was found to be effective in optimizing the total heat transfer for a given target temperature.     

Order reduction via balancing and suboptimal control of a fuel cell – Reformer system

In this paper we first perform system balancing of an eighth-order mathematical model of a polymer electrolyte membrane fuel cell (PEMFC) dynamic coupled with a tenth-order mathematical model of a hydrogen gas reformer. Based on that information we determine reduced-order mathematical models of the original eighteen-order model by eliminating state variables that have negligible contribution to the model dynamics. Having obtained the reduced-order models, we study their step and impulse responses, and compare them to those of the original full-order model. In addition, we design corresponding suboptimal feedback controllers based on the reduced-order models. Comparing the obtained suboptimal controllers (that require a reduced number (only six or even five) of feedback loops making them easy for implementation) we find that their suboptimal performances are very close to the optimal performance of the full-state optimal feedback controller. It is important to emphasize that the full-order state feedback controller requires the same number of the feedback loops as the dimension of the original full-order state space model (in this case eighteen), which makes it complex and sometimes impractical to implement.     

Optimization of a Darrieus vertical-axis wind turbine using blade element – momentum theory and evolutionary algorithm

Wind turbine design procedures usually involve the adoption of the blade element – momentum theory. Nevertheless, its use is limited by the lack of extended database regarding the aerodynamic coefficients for most used airfoils. In the present work, an extended database generation procedure for symmetric profiles is discussed and validated with the aim of adopting numerical optimization methods for vertical-axis wind turbine design.Evolutionary algorithms are thereby utilized to provide optimal configurations for different design objectives. The pure performance and the annual energy production are here considered in order to show the capabilities of the numerical code. A relevant increase in performance is achieved for all the obtained results, showing that the numerical optimization can be successfully adopted in vertical-axis wind turbine design procedures.     

Optimization of hydrogen production via toluene steam reforming over Ni–Co supported modified-activated carbon using ANN coupled GA and RSM

Hydrogen (H₂) is a clean fuel that can be produced from various resources including biomass. Optimization of H₂ production from catalytic steam reforming of toluene using response surface methodology (RSM) and artificial neural network coupled genetic algorithm (ANN-GA) models has been investigated. In RSM model, the central composite design (CCD) is employed in the experimental design. The CCD conditions are temperature (500–900 °C), feed flow rate (0.006–0.034 ml/min), catalyst weight (0.1–0.5 g) and steam-to-carbon molar ratio (1–9). ANN model employs a three-layered feed-forward backpropagation neural network in conjugation with the tangent sigmoid (tansig) and linear (purelin) as the transfer functions and Levenberg-Marquardt training algorithm. Best network structure of 4-14-1 is developed and utilized in the GA optimization for determining the optimum conditions. An optimum H₂ yield of 92.6% and 81.4% with 1.19% and 6.02% prediction error are obtained from ANN-GA and RSM models, respectively. The predictive capabilities of the two models are evaluated by statistical parameters, including the coefficient of determination (R²) and root mean square error (RMSE). Higher R² and lower RSME values are reported for ANN-GA model (R² = 0.95, RMSE = 4.09) demonstrating the superiority of ANN-GA in determining the nonlinear behavior compared to RSM model (R² = 0.87, RMSE = 6.92). These results infer that ANN-GA is a more reliable and robust predictive steam reforming modelling tool for H₂ production optimization compared to RSM model.     

Design and performance analysis of a solar-geothermal-hydrogen production hybrid generation based on S–CO2 driven and waste-heat cascade utilization

In the present paper, a multi-energy complementary power generation is designed. It's a hybrid plant of solar power, geothermal power and hydrogen power based on S–CO₂ and T-CO₂ brayton cycle driven. The thermal power for hydrogen production is gained from the extracting S–CO₂ of solar power side and power consumption is 0.2% of PEM. The hybrid plant has the novel feature of time and energy complementarity. Through the thermodynamic analysis, the results reveal that energy efficiency and exergy efficiency could reach 78.14% and 84.04%, comparing with some other hybrid plans, the values have increased by about 20% and 30%, respectively. Through a sensitivity analysis, three optimal split radios have been put forward and the values are 0.68, 0.93 and 0.96, respectively. The Mg–Cl thermochemical cycle is used to hydrogen production and producing hydrogen energy is about 0.902 GJ/h. The economic analysis is investigated by COE_S and CRF, and the net economic profit is at least 42.11 million USD. The proposal system is based on the S–CO₂ and T-CO₂ driven and the daily average CO₂ circulating flow could get 55.0 × 10⁶ kg, it could decrease lots of greenhouse-gas emissions.     

Sustainable hydrogen society – Vision,findings and development of a hydrogen economy using the example of Austria

Based on technical, environmental, economic and social facts and recent findings, the feasibility of the transition from our current fossil age to the new green age is analyzed in detail at both global and local level. To avert the threats of health problems, environmental pollution and climate change to our quality and standard of life, a twofold radical paradigm shift is outlined: Green Energy Revolution means the complete change from fossil-based to green primary energy sources such as sun, wind, water, environmental heat, and biomass; Green Hydrogen Society means the complete change from fossil-based final energy to green electricity and green hydrogen in all areas of mobility, industries, households and energy services. Renewable energies offer a green future and are in combination with electrochemical machines such as electrolysers, batteries and fuel cells able to achieve higher efficiencies and zero emissions.     

Stability of nickel catalyst supported by mesoporous alumina for hydrogen iodide decomposition and hybrid decomposer development in sulfur–iodine hydrogen production cycle

We propose a hybrid HI decomposer, which combines a high-temperature catalytic decomposition reactor with a dual bed temperature-swing decomposer. For the high temperature step, we screened and identified a catalyst that is stable above 700 °C by preparing nickel catalysts supported on mesoporous alumina and evaluating their activity toward the high-temperature catalytic decomposition reaction. The catalysts achieved HI decomposition yields up to 23% at 650 °C and maintained over 20% yield after 100 h of operation. For the temperature-swing process, we investigated the adsorption, desorption, and regeneration efficiency, and the optimal regeneration temperature of nickel catalysts supported on silica/alumina adsorbents. The optimal regeneration temperature was 400 °C. Based on these results, we propose hybrid HI decomposers in two configurations: 1) residual HI decomposer and 2) HI concentrator. The residual HI decomposer improves the overall conversion efficiency to levels above the thermodynamic limit, while the HI concentrator increases the concentration of HI by simple temperature control, even at below-azeotropic HI concentrations.     

Design and reliability assessment of control systems for a nuclear-based hydrogen production plant with copper–chlorine thermochemical cycle

The thermochemical Copper–Chlorine (Cu–Cl) cycle is an emerging new method of nuclear-based hydrogen production. In the process, water is decomposed into hydrogen and oxygen through several physical and chemical processes. In this paper, a Distributed Control System (DCS) is designed for the thermochemical Cu–Cl cycle. The architecture and the communication networks of the DCS are discussed. Reliability of the DCS is assessed using fault trees. In the assessment, the impact of the malfunction of the actuators, sensors, controllers and communication networks on the overall system reliability is investigated. This provides key information for the selection of control system components, and determination of their inspection frequency and maintenance strategy. The hydrogen reactor unit, which is one of the major components in the thermochemical Cu–Cl cycle, is used to demonstrate the detailed design and analysis.     

Time-dependent climate impact of heat production from Swedish willow and poplar pellets – In a life cycle perspective

Sweden has the potential to increase fuel pellet production from alternative raw materials, such as willow and poplar, and also to use former agricultural land for energy crop production. This study used a life cycle perspective to investigate district heat production from pellets produced from willow or poplar cultivated on fallow land in Sweden. The energy efficiency and global warming potential of the systems was evaluated, additionally was the climate impact, expressed in global mean surface temperature change, evaluated from annual greenhouse gas data, including the most relevant fossil and biogenic sources and sinks. The systems were also compared with a fossil fuel alternative in which coal was assumed to be used for heat production. The results showed that the systems investigated had a cooling effect on both global mean surface temperature and global warming potential within the 100-year study period owing mainly to an increase in live biomass and a more long-term increase in soil organic carbon (C), which shows the importance of land use. At the same time, the systems produced renewable energy. The poplar system contributed to a larger cooling effect than the willow system due to more C being sequestered in live biomass and soil in the longer growth periods between harvests and to higher yield. The energy efficiency of the willow and poplar systems used for pellet fuel production was about 11 times the energy input.     

Thermoeconomic assessment of a multi-engine,multi-heat-pump CCHP (combined cooling,heating and power generation) system – A case study

Design and operation of complex systems for combined cooling, heating and power generation (CCHP) are always a matter of matching performance and demand characteristics of a thermal system set to supply electrical, cooling and heating loads, according to specific usage demands. Equipment selection and operation require the characterization of power, heating and cooling load demands, and their time variation during years, seasons, months and even hours or minutes. The paper aims at utilizing a general model for complex CCHP systems. The proposed model is based on the general theory of exergy cost and structural coefficients of internal links. A general model is presented, and a simple hypothetical cogeneration case is studied. The system operates with two heat engines, with waste heat recovery driving a chiller, in order to meet electrical power and refrigeration loads.     

Economic impact of performances degradation on the competitiveness of energy storage technologies – Part 1: Introduction to the simulation-optimization platform ODYSSEY and elements of validation on a PV-hydrogen hybrid system

In this paper, a newly developed assessment platform Odyssey is introduced. This platform is dedicated to perform comprehensive techno-economic assessments of energy systems comprising renewable energy sources and energy storage units. The major strengths of this platform are described and it is then illustrated on an application example with the objective to provide elements of validation of the platform. This application case is related to the electrical energy supply of a weather station by the mean of a PV-hydrogen hybrid energy system combining PV modules and a hydrogen chain. Experimental results obtained on the fuel cell and electrolyser systems are confronted to simulation results.     

Enhanced hydrogen production via staged catalytic gasification of rice husk using Ca(OH)2 adsorbent and Ce–Ni/γAl2O3 catalyst in a fluidized bed

Hydrogen production from rice husk was carried out via a two-stage system combining CLG (calcium looping gasification) using Ca(OH)₂ adsorbent in a bubbling fluidized bed and catalytic reforming with Ce–Ni/γAl₂O₃ catalyst in a connected fixed bed. The results show that the maximum H₂ concentration (69.16 vol%) and H₂ yield (11.86 mmol g⁻¹rice husk) are achieved at Ca/C (Ca(OH)₂ to carbon molar ratio) = 1.5, H₂O/C (H₂O to carbon molar ratio) = 1.5, T_g (gasification temperature) = 500 °C, T_c (catalytic temperature) = 800 °C. The supplementation of fresh Ca(OH)₂ at Ca/C of 0.5 during calcination helps to activate the regenerated CaO by hydration, maintaining its carbonation activity and CO₂ adsorption. Ce–Ni/γAl₂O₃ catalyst promotes water gas shift (WGS), steam methane reforming (SMR), and C₂–C₃ hydrocarbons reforming, also exhibits excellent activity stability to maintain H₂ concentration and H₂ yield above 67.21 vol% and 11.67 mmol g⁻¹_{rice husk}, respectively, during 5 lifetime tests.