Production & Supply Chain

Water electrolysis (WE) is a highly promising approach to producing clean hydrogen. Medium-temperature WE (100–350 ◦C) can improve the energy efficiency and utilize the low-grade water vapor. Therefore a high-temperature proton-conductive membrane is desirable to realize the medium-temperature WE. Here we present a polyvinyl chloride (PVC)-poly(4vinylpyridine) (P4VP) hybrid membrane by a simple cross-linking of PVC and P4VP. The pyridine groups of P4VP promote the loading rate of phosphoric acid which delivers the proton conductivity of the PVC-P4VP membrane. The optimized PVC-P4VP membrane with a 1:2 content ratio offers the maximum proton conductivity of 4.3 × 10−2 S cm−1 at 180 ◦C and a reliable conductivity stability in 200 h at 160 ◦C. The PVC-P4VP membrane electrode is covered by an IrO2 anode and a Pt/C cathode delivers not only the high water electrolytic reactivity at 100–180 ◦C but also the stable WE stability at 180 ◦C.

A battolyser is a combined battery electrolyser in one unit. It is based on flow battery technology and can be adapted to produce hydrogen at a lower efficiency than an electrolyser but without the need for rare and expensive materials. This paper presents a method of determining if a battolyser connected to a wind farm makes economic sense based on stochastic modelling. A range of cost data and operational scenarios are used to establish the impact on the NPV and LCOE of adding a battolyser to a wind farm. The results are compared to adding a battery or an electrolyser to a wind farm. Indications are that it makes economic sense to add a battolyser or battery to a wind farm to use any curtailed wind with calculated LCOE at £56/MWh to £58/MWh and positive NPV over a range of cost scenarios. However electrolysers are still too expensive to make economic sense.

Energy supplies that are safe environmentally friendly dependable and cost-effective are important for society's long-term growth and improved living standards though political social and economic barriers may inhibit their availability. Constantly increasing energy demand is induced by substantial population growth and economic development putting an increasing strain on fossil fuel management and sustainability which account for a major portion of this rising energy demand and moreover creates difficulties because of greenhouse gas emissions growth and the depletion of resources. Such impediments necessitate a global shift away from traditional energy sources and toward renewables. Aside from its traditional role is viewed as a promising energy vector and is gaining international attention as a promising fuel path as it provides numerous benefits in use case scenarios and unlike other synthesized carbon-based fuels could be carbon-free or perhaps even negative on a life-cycle criterion. Hydrogen ( ) is one of the most significant chemical substances on earth and can be obtained as molecular dihydrogen through various techniques from both non-renewable and renewable sources. The drive of this paper is to deliver a technological overview of hydrogen production methods. The major challenges development and research priorities and potential prospects for production was discussed.

Biomass gasification for hydrogen (H2) production provides outstanding advantages in terms of renewable energy resources carbon neutral high efficiency and environmental benefits. However the factors influencing H2 production from biomass gasification are complex which makes determining the optimal operating conditions challenging. Biomass gasification also poses challenges owing to the high associated tar content and low gas yield which need to be overcome. This review summarizes the influence of the gasification parameters on H2 production. Catalytic gasification technology and some of the latest catalysts such as composites and special structure catalysts are also summarized herein based on the requirements of high-purity H2 production. Moreover novel technologies such as staged gasification chemical looping gasification and adsorption-enhanced reforming for producing H2 rich gas are introduced. Finally the challenges and prospects associated with biomass gasification for H2 production are presented.

To face the intensive use of natural gas and other fossil fuels to generate hydrogen water electrolysis based on renewable energy sources (RES) seems to be a viable solution. Due to their fast response times and high efficiency proton exchange membrane electrolyzer (PEM EL) is the most suitable technology for long-term energy storage combined with RES. Like fuel cells the development of fit DC-DC converters is mandatory to interface the EL to the DC grid. Given that PEM EL operating voltages are quite low and to meet requirements in terms of output current ripples new emerging interleaved DC-DC converter topologies seem to be the best candidates. In this work a three-level interleaved DC-DC buck converter has been chosen to supply a PEM EL from a DC grid. Therefore the main objective of this paper is to develop a suitable control strategy of this interleaved topology connected to a PEM EL emulator. To design the control strategy investigations have been carried out on energy efficiency hydrogen flow rate and specific energy consumption. The obtained experimental results validate the performance of the converter in protecting the PEM EL during transient operations while guaranteeing correct specific energy consumption.

This study investigates the optimal design of low-carbon hydrogen supply chains on a national scale. We consider hydrogen production based on several feedstocks and energy sources namely water with electricity natural gas and biomass. When using natural gas we couple hydrogen production with carbon capture and storage. The design of the hydrogen biomass and carbon dioxide (CO₂ ) infrastructure is performed by solving an optimization problem that determines the optimal selection size and location of the hydrogen production technologies and the optimal structure of the hydrogen biomass and CO₂ O2 networks. First we investigate the rationale behind the optimal design of low-carbon hydrogen supply chains by referring to an idealized system configuration and by performing a parametric analysis of the most relevant design parameters of the supply chains such as biomass availability. This allows drawing general conclusions independent of any specific geographic features about the minimum-cost and minimum-emissions system designs and network structures. Moreover we analyze the Swiss case study to derive specific guidelines concerning the design of hydrogen supply chains deploying carbon capture and storage. We assess the impact of relevant design parameters such as location of CO₂ storage facilities techno-economic features of CO₂ capture technologies and network losses on the optimal supply chain design and on the competition between the hydrogen and CO₂ networks. Findings highlight the fundamental role of biomass (when available) and of carbon capture and storage for decarbonizing hydrogen supply chains while transitioning to a wider deployment of renewable energy sources.

Biomass is plant or animal material that stores both chemical and solar energies and that is widely used for heat production and various industrial processes. Biomass contains a large amount of the element hydrogen so it is an excellent source for hydrogen production. Therefore biomass is a sustainable source for electricity or hydrogen production. Although biomass power plants and reforming plants have been commercialized it remains a difficult challenge to develop more effective and economic technologies to further improve the conversion efficiency and reduce the environmental impacts in the conversion process. The use of biomass-based flow fuel cell technology to directly convert biomass to electricity and the use of electrolysis technology to convert biomass into hydrogen at a low temperature are two new research areas that have recently attracted interest. This paper first briefly introduces traditional technologies related to the conversion of biomass to electricity and hydrogen and then reviews the new developments in flow biomass fuel cells (FBFCs) and biomass electrolysis for hydrogen production (BEHP) in detail. Further challenges in these areas are discussed.

Developing non-precious catalysts as Pt substitutes for electrochemical hydrogen evolution reaction (HER) with superior stability in acidic electrolyte is of critical importance for large-scale low-cost hydrogen production from water. Herein we report a CoCrFeNiAl high-entropy alloy (HEA) electrocatalyst with self-supported structure synthesized by mechanical alloying and spark plasma sintering (SPS) consolidation. The HEA after HF treatment and in situ electrochemical activation for 4000 cycles of cyclic voltammetry (HF-HEAa2) presents favourable activity with overpotential of 73 mV to reach a current density of 10 mA cm⁻² and a Tafel slope of 39.7 mV dec⁻¹. The alloy effect of Al/Cr with Co/Fe/Ni at atomic level high-temperature crystallization as well as consolidation by SPS endow CoCrFeNiAl HEA with high stability in 0.5 M H₂SO₄ solution. The superior performance of HF-HEAa2 is related with the presence of metal hydroxides/oxides groups on HEA.

Direct CO₂ hydrogenation to hydrocarbons is a promising method of reducing CO2 emissions along with producing value-added products. However reactor design and performance have remained a challenging issue because of low olefin efficiency and high water production as a by-product. Accordingly a one-dimensional non-isothermal mathematical model is proposed to predict the membrane reactor performance and statistical analysis is used to assess the effects of important variables such as temperatures of reactor (Tr:A) shell (Ts:B) and tube (Tt:C) as well as sweep ratio (θ:D) and pressure ratio (φ:E) and their interactions on the products yields. In addition the optimized operating conditions are also obtained to achieve maximum olefin yields. Results reveal that interacting effects comprising AB (TrTs) AC (TrTt) AE (Trφ) BC (TsTt) CE (Ttφ) CD (Ttθ) and DE (θφ) play important roles on the product yields. It is concluded that higher temperatures at low sweep and pressure ratios can maximize the yields of olefins while simultaneously the yields of paraffins are minimized. In this regard optimized values for Tr Ts Tt θ and φ are determined as 325 °C 306.96 °C 325 °C 1 and 1 respectively.

Photoelectrochemical splitting of water is potentially a sustainable and affordable solution to produce hydrogen from sun light. Given the infancy stage of technology development it is important to compare the different experimental concepts and identify the most promising routes. The performance of photoelectrochemical devices is typically measured and reported under ideal irradiation conditions i.e. 1 sun. However real-life operating conditions are very different and are varying in time according to daily and seasonal cycles. In this work we present an equivalent circuit model for computing the steady state performance of photoelectrochemical cells. The model allows for a computationally efficient yet precise prediction of the system performance and a comparison of different devices working in real operating conditions. To this end five different photo-electrochemical devices are modeled using experimental results from literature. The calculated performance shows good agreement with experimental data of the different devices. Furthermore the model is extended to include the effect of illumination and tilt angle on the hydrogen production efficiency. The resulting model is used to compare the devices for different locations with high and low average illumination and different tilt angles. The results show that including real illumination data has a considerable impact on the efficiency of the PV-EC device. The yearly average solar-to-hydrogen efficiency is significantly lower than the ideal one. Moreover it is dependent on the tilt angle whose optimal value for European-like latitude is around 40. Notably we also show that the most performing device through the whole year might not necessarily be the one with highest sun-to-hydrogen efficiency for one-sun illumination.