Strategic planning with risk control of hydrogen supply chains for vehicle use under uncertainty in operating costs: A case study of Spain

In this paper we present a decision-support tool to address the strategic planning of hydrogen supply chains for vehicle use under uncertainty in the operating costs. Given is a superstructure of alternatives that embeds a set of available technologies to produce, store and deliver hydrogen. The objective of our study is to determine the optimal design of the production–distribution network capable of fulfilling a predefined hydrogen demand. The design task is formulated as a multi-scenario mixed-integer linear problem (MILP) that considers the uncertainty associated with the coefficients of the objective function of the model (i.e. operating costs, raw materials prices, etc.). The novelty of the approach presented is that it allows controlling the variation of the economic performance of the hydrogen network in the space of uncertain parameters. This is accomplished by using a risk metric that is appended to the objective function as an additional criterion to be optimized. An efficient decomposition method is also presented in order to expedite the solution of the underlying multi-objective model by exploiting its specific structure. The capabilities of the proposed modeling framework and solution strategy are illustrated through the application to a real case study based on Spain, for which valuable insights are obtained.     

Optimization and analysis of a hydrogen supply chain in terms of cost,CO2 emissions,and risk: the case of Turkey

The transportation sector, which is largely dependent on oil, is faced with many problems such as the danger of depletion of fossil fuels that are harmful to the environment. Moreover, the situations such as epidemics and war cause excessive fluctuations in oil prices. Therefore, there is a need for new solutions based on alternative energy sources for a sustainable transportation sector. Hydrogen fuel cell electric vehicles (HFCEV) are one of the significant alternatives for an efficient, zero emissions and sustainable transportation system. Considering the potential investment in HFCEV technology, the need for a cost effective, green, and low risk Hydrogen Supply Chain (HSC) network infrastructure is inevitable. In this study, the HSC design of the Turkish transportation sector over a 25-year period (2026–2050) is investigated. The problem is modeled using a multi-period mixed integer linear programming (MIP) model. Three objectives are addresses: cost, carbon dioxide (CO₂) emissions and safety risk. In order to consider the uncertainty in the hydrogen demand, five different scenarios are analyzed using fuzzy concept. There are four main results. First, unit hydrogen cost is found to be very high due to low demand and high capital cost in the initial period (2026–2031). Second, HSC network is established in a decentralized setting in all scenario solutions. The level of decentralization gets stronger over time and with increasing demand. Third, short-distance road transport is generally preferred for hydrogen transport. Fourth, since the aim is to minimize cost, CO₂ emissions, and risk level, a mixed production strategy based on cost-oriented SMR and zero-emissions-oriented Electrolysis (ELE) is observed in all scenarios.     

The costs of hydro power: Evidence on learning-by-doing,economies of scale and resource constraints in Austria

The paper investigates the costs of hydro power plants. Expansion of hydro power is accompanied by two contrary tendencies. First, learning-by-doing and technological progress for the industry as a whole which reduce costs over time, and second, resource constraints which tend to increase costs as more and more hydro power capacity is installed. Hence, a U-shaped cost curve should apply. In particular, hydro power expansion becomes increasingly costly once a substantial fraction of potential hydro power supply is exploited. This hypothesis is empirically applied to Austrian data.     

The effect of flow type patterns in a novel thermally coupled reactor for simultaneous direct dimethyl ether (DME) and hydrogen production

Dimethyl ether (DME) has gained wide interest in chemical industry regarding its use as a multi-source, multi-purpose fuel either for diesel engines or as a clean alternative for liquefied petroleum gas (LPG). The direct synthesis of DME from syngas would be more economical and beneficial in comparison to the indirect process via methanol dehydration. In this study, one type of the multifunctional auto-thermal reactors (the recuperative one) is selected in which the direct synthesis of dimethyl ether (DME) is coupled with the catalytic dehydrogenation of cyclohexane to benzene in a two fixed bed reactor separated by a solid wall, where heat is transferred across the surface of tube. Steady-state, heterogeneous, one-dimensional model has been used to describe the performance of this novel configuration. Both co-current and counter-current operating modes are investigated and the simulation results are compared with the available data of a pipe-shell fixed bed reactor for direct DME synthesis which operates at the same feed conditions. In addition, the influence of the molar flow rate of exothermic and endothermic stream on the reactor performance is also investigated. The results suggest that coupling of these reactions could be feasible and beneficial and the co-current mode has got better performance in DME and hydrogen production. In order to establish the validity and safety handling of the new concept, an experimental proof is required.     

Effect of Zr7Ni10 additive on hydrogen mobility in (TiCr1.8)1-xVx (x = 0.2, 0.4, 0.6, 0.8): An 1H NMR SFG study

In order to optimize hydrogen storage properties of bcc Ti–V–Cr alloys it was found that alloying with a few 4 at% of Zr₇Ni₁₀ results in acceleration the hydrogen sorption kinetics in the composite material. The novel intergranular phase plays a role of gate for hydrogen, leading parallel to its easy decrepitate, thus enhancing fast formation of Ti–V–Cr hydrides. Nevertheless, the question on how such a composite microstructure affects hydrogen mobility in the material is still open. Here we report on the results of the studies of hydrogen self-diffusion in hydrogenated (TiCr_1.8)_1-xV_x based alloys (x = 0.2, 0.4, 0.6 and 0.8) carried out using proton nuclear magnetic resonance diffusiometry in a static field gradient_. For all compounds the method has proved itself as a powerful tool to probe the microstructure of the multicomponent alloys with inhomogeneous element distribution in a few micrometer scale. It has been found that addition of Zr₇Ni₁₀ lowers the activation energy of hydrogen motion in (TiCr_1.8)_1-xV_x alloys and leads appear two different diffusion areas. They can be associated with a redistribution of elements within the intra-granular phase due to opposite substitution of Ti and Ni atoms during synthesis and blurring the boundaries between the intra-granular and inter-granular phases.     

Probability of occurrence of ISO 14687-2 contaminants in hydrogen: Principles and examples from steam methane reforming and electrolysis (water and chlor-alkali) production processes model

According to European Directive 2014/94/EU, hydrogen providers have the responsibility to prove that their hydrogen is of suitable quality for fuel cell vehicles. Contaminants may originate from hydrogen production, transportation, refuelling station or maintenance operation. This study investigated the probability of presence of the 13 gaseous contaminants (ISO 14687-2) in hydrogen on 3 production processes: steam methane reforming (SMR) process with pressure swing adsorption (PSA), chlor-alkali membrane electrolysis process and water proton exchange membrane electrolysis process with temperature swing adsorption. The rationale behind the probability of contaminant presence according to process knowledge and existing barriers is highlighted. No contaminant was identified as possible or frequent for the three production processes except oxygen (frequent for chlor-alkali membrane process), carbon monoxide (frequent) and nitrogen (possible) for SMR with PSA. Based on it, a hydrogen quality assurance plan following ISO 19880-8 can be devised to support hydrogen providers in monitoring the relevant contaminants.     

Modification of graphenylene nanostructure with transition metals (Fe,Sc and Ti) to promote hydrogen storage ability: A DFT-D3 study

Hydrogen, as a clean alternative to fossil fuels, has received much attention in recent years. But its utilizing requires to overcome storage problems. Here, we investigated the hydrogen adsorption behavior of graphenylene (GPY), a 2D carbon nanostructure, and Sc, Fe and Ti transition metal (TM) decorated GPY by spin-polarized DFT calculations. For TM-decoration of GPY, seven different sites and various distances from carbon sheet were investigated, carefully. Structural and electronic properties of the structures, adsorption energies, band gap values, and the most stable configurations were considered and discussed. Results showed that 6-membered ring (H2 site) is the best site for Sc, Fe, and Ti-decoration and corresponding E_ads was −3.95, −2.66, and −3.65 eV, respectively. Also, pristine GPY and Sc and Ti-decorated GPY have not magnetic character, unlike Fe-GPY. As well, entrance of Sc, Fe and Ti atoms in H2 site of the GPY structure causes its band gap increases from 0.033 eV to of 0.491, 0.080, and 0.372 eV, respectively. E_ads of the H₂ molecule onto pristine GPY is low (−0.160 eV), and must be improved for practical hydrogen storage applications. Sc, Fe, and Ti-decoration improves it about 2.23, 5.69 and 3.63 times. Because of this improvement, we could store up to 20H₂ molecules on TM-decorated GPY systems. These results indicate that TM-decorated GPY can be a suitable option for H₂ storage applications in the future.     

Metal-organic frameworks (MOFs)-based efficient heterogeneous photocatalysts: Synthesis,properties and its applications in photocatalytic hydrogen generation,CO2 reduction and photodegradation of organic dyes

Metal-organic frameworks (MOFs) are a new class of functional materials having porous structures that show extraordinary specific surface areas, and tunable surface chemistry; hence, they hold great potential as photocatalysts. This review describes the fundamentals of MOFs and possible new research directions in the area of heterogeneous MOFs that can provide enhanced photocatalytic performance, especially for hydrogen production, degradation of emerging organic pollutants, and CO₂ reduction. The role of MOFs as multifunctional photocatalysts for light-stimulated organic reactions through an effective combination of metal/ligand/guest-based photocatalysts is discussed. Recent literature is discussed critically on the design and selection of materials, with possible directions to improve their catalytic properties. Furthermore, this comprehensive review systematically discusses the current developments of various MOFs-based hybrid nanostructures as multifunctional photocatalysts from different points, including several synthetic methodologies, key features, photocatalytic mechanism, and various influencing parameters to enhance catalytic efficiency. The recent achievements are critically discussed in the designing and selection of MOFs-based functional materials, with directions to effectively improve their catalytic properties for various photocatalytic applications. The article also summarizes with challenges and future prospects for the cost-effective and large scale photocatalytic applications of MOFs-based heterostructured catalysts.     

Effects of nonmetal element (B,C and Si) additives in Mg2Ni hydrogen storage alloy: A first-principles study

Nonmetal atoms (B, C and Si) are designed to add into Mg₂Ni hydrogen storage alloy and its hydride. First-principles density-functional theory calculations have been performed to investigate their crystal structures, electronic and thermodynamic properties. The calculation results present that nonmetal additions in Mg₂NiH₄ show more effective destabilization than metal additions. Especially for B and C, the decreases of formation enthalpies of Mg₂NiH₄ reach 0.19 and 0.21 eV/atom. The NiH₄ structure near B or C in Mg₂NiH₄ hydride becomes the tripod-like NiH₃ structure. The results show that the thermodynamic stabilities of Mg₂Ni and Mg₂NiH₄ exhibit a nearly linear decrease with the increasing content of nonmetal atoms. The calculated dehydrogenation energies are 59.39, 58.12, 55.84 and 55.30 kJ/mol H₂ for Mg₂NiH₄, Mg₂NiB_0.5H₄, Mg₂NiC_0.5H₄ and Mg₂NiSi_0.5H_4, respectively. It is found that the addition of nonmetal atoms favors the dehydrogenation reaction for Mg₂Ni hydrogen storage material. In addition, the effects of nonmetals to the heat capacities and vibrational entropies of Mg₂Ni and Mg₂NiH₄ are also analyzed.     

Efficiency and economic benefit of dark-fermentative biohydrogen production in Asian circular economies: Evaluation using soft-link methodology with data envelopment analysis (DEA) and computable general equilibrium model (CGE)

This study combines a data envelopment analysis, a dynamic computable general equilibrium model with estimated secondary material flows for circular economy, based on economist Joseph Schumpeter's macroeconomic theory, to develop a novel soft-link model to determine the efficiency of forty-three dark-fermentative technology of biohydrogen, and technology improvement impacts on biohydrogen output and supply price for six major emerging Asian countries. The integrated model is found to be feasible.This study finds that efficiency of continuous technology significantly exceeds that of batch technology. Biomass substrate concentration is the most important input in the generation of biohydrogen statistically; pH influences the efficiency of the batch technology, and the efficiency of continuous production technologies significantly exceeds that of batch technologies, but still have a gap to improve to full production efficiency for most of continuous technologies. India and China generate highest output growth of biohydrogen in baseline scenario. Japan and India can most benefit from improvements in batch and continuous biohydrogen production technology. The models and results of this study provides guidelines and references for decision-makers in industry and government who are responsible for reforming future energy policy.     

Renewable energy sources (RES) projects and their barriers on a regional scale: The case study of wind parks in the Dodecanese islands, Greece

The increasing energy challenges faced, in particular, by isolated communities, such as insular communities, call for an integrated, flexible and easy-to-apply methodology aiming at providing a list of renewable energy sources) (RES) projects capable to reduce green house gas (GHG) emissions, satisfy future energy forecasts and reach the objectives of international/national energy directives and obligations, as, for example, the ones set by the Kyoto Protocol by 2010. The EU project EMERGENCE 2010 developed such a methodology that is implemented here in the case study of wind parks in the Dodecanese islands in Greece. The results obtained consist of a final list of financially viable RES wind projects, for which various barriers have been previously identified and assessed. The additional advantages of the proposed methodology is that besides providing as an end result a comprehensive list of RES projects adopted to specific criteria and regional priorities, it also allows space for involving – from early stages – the local community and stakeholders in the decision-making process (participatory planning); in this way, the EMERGENCE 2010 methodology may assist towards the RES promotion and public acceptance, the profitability of RES investments and the regional sustainable development.