Hydrogen production from offshore wind power in South China

Wind power hydrogen production is the direct conversion of electricity generated by wind power into hydrogen through water electrolysis hydrogen production equipment, which produces hydrogen for convenient long-term storage through water electrolysis. With the development of offshore wind power from offshore projects, construction costs continue to rise. Turning power transmission into hydrogen transmission will help reduce the cost of offshore wind power construction. This paper analyses the methods of producing hydrogen from offshore wind power, including alkaline water electrolysis, proton exchange membrane electrolysis of water, and solid oxide electrolysis of water. In addition, this paper outlines economic and cost analyses of hydrogen production from offshore wind power. In the future, with the development and advancement of water electrolysis hydrogen production technology, hydrogen production from offshore wind power could be more economical and practical.     

浮式风电制氢装置设计研究

对浮式风电制氢装置工程化进行了研究,并基于8～10 MW的浮式风电平台,设计了3MW独立式风电制氢装置,制定了利用风机发电提供的能源,提取海水进行纯化和电解水制氢的技术路线,提出了关键设备的技术要求,并进行了系统的布置及初步的安全性和经济性分析。结果表明,由于经济性差,海工应用还不成熟,目前海上浮式制氢的工程化还需要一个过程,进行工程试验是大规模工程化的前提。     

PEM electrolysis for production of hydrogen from renewable energy sources

PEM electrolysis is a viable alternative for generation of hydrogen from renewable energy sources. Several possible applications are discussed, including grid independent and grid assisted hydrogen generation, use of an electrolyzer for peak shaving, and integrated systems both grid connected and grid independent where electrolytically generated hydrogen is stored and then via fuel cell converted back to electricity when needed. Specific issues regarding the use of PEM electrolyzer in the renewable energy systems are addressed, such as sizing of electrolyzer, intermittent operation, output pressure, oxygen generation, water consumption and efficiency.     

Seismic fragility analysis of 5 MW offshore wind turbine

Considering nonlinear soil–pile interaction, seismic fragility analysis of offshore wind turbine was performed. Interface between ground soils and piles were modeled as nonlinear spring elements. Ground excitation time histories were applied to spring boundaries. Two methods of applying ground motion were compared. Different time histories from free field analysis were applied to each boundary in the first loading plan (A). They were compared with the second loading plan (B) in which the same ground motion is applied to all boundaries. Critical displacement for wind turbine was proposed by using push-over analysis. Both the stress based and the displacement based fragility curves were obtained using dynamic responses for different peak ground accelerations (PGAs). In numerical example, it was shown that seismic responses from loading plan A are bigger than from plan B. It seems that the bigger ground motion at surface can cause less response at wind turbine due to phase difference between ground motions at various soil layers. Finally, it can be concluded that layer by layer ground motions from free field analysis should be used in seismic design of offshore wind turbine.     

Economics of producing hydrogen as transportation fuel using offshore wind energy systems

Over the past few years, hydrogen has been recognized as a suitable substitute for present vehicular fuels. This paper covers the economic analysis of one of the most promising hydrogen production methods—using wind energy for producing hydrogen through electrolysis of seawater—with a concentration on the Indian transport sector. The analysis provides insights about several questions such as the advantages of offshore plants over coastal installations, economics of large wind-machine clusters, and comparison of cost of producing hydrogen with competing gasoline. Robustness of results has been checked by developing several scenarios such as fast/slow learning rates for wind systems for determining future trends. Results of this analysis show that use of hydrogen for transportation is not likely to be attractive before 2012, and that too with considerable learning in wind, electrolyzer and hydrogen storage technology.     

Development of a viability assessment model for hydrogen production from dedicated offshore wind farms

Dedicated offshore wind farms for hydrogen production are a promising option to unlock the full potential of offshore wind energy, attain decarbonisation and energy security targets in electricity and other sectors, and cope with grid expansion constraints. Current knowledge on these systems is limited, particularly the economic aspects. Therefore, a new, integrated and analytical model for viability assessment of hydrogen production from dedicated offshore wind farms is developed in this paper. This includes the formulae for calculating wind power output, electrolysis plant size, and hydrogen production from time-varying wind speed. All the costs are projected to a specified time using both Discounted Payback (DPB) and Net Present Value (NPV) to consider the value of capital over time. A case study considers a hypothetical wind farm of 101.3 MW situated in a potential offshore wind development pipeline off the East Coast of Ireland. All the costs of the wind farm and the electrolysis plant are for 2030, based on reference costs in the literature. Proton exchange membrane electrolysers and underground storage of hydrogen are used. The analysis shows that the DPB and NPV flows for several scenarios of storage are in good agreement and that the viability model performs well. The offshore wind farm – hydrogen production system is found to be profitable in 2030 at a hydrogen price of €5/kg and underground storage capacities ranging from 2 days to 45 days of hydrogen production. The model is helpful for rapid assessment or optimisation of both economics and feasibility of dedicated offshore wind farm – hydrogen production systems.     

Assessment of offshore liquid hydrogen production from wind power for ship refueling

Green hydrogen from electrolysis has become the most attractive energy carrier for making the transition from fossil fuels to carbon-free energy sources possible. Especially in the naval sector, hydrogen has the potential to address environmental targets due to the lack of low-carbon fuel options. This study aims at investigating an offshore liquefied green hydrogen production plant for ship refueling. The plant comprises a wind farm for renewable electricity generation, an electrolyzer stack for hydrogen production, a water treatment unit for demineralized water production, and a hydrogen liquefaction plant for hydrogen storage and distribution to ships. A pre-feasibility study is addressed to find the optimal capacities of the plant that minimize the payback time. The model results show that the electrolyzer capacity shall be set equal to a value between 80% and 90% of the wind farm capacity to achieve the minimum payback times. Additionally, the wind farm capacity shall be higher than about 150 MW to limit the payback time to values lower than 11 years for a fixed hydrogen price of 6 €/kg. The Levelized Cost of Hydrogen results to be below 4 €/kg for a wide range of plant capacities for a lifetime of the plant of 25 years. Thus, the model shows that this plant is economically feasible and can be reproduced similarly for different locations by rescaling the different selected technologies. In this way, the naval sector can be decarbonized thanks to a new infrastructure for the production and refueling of liquified green hydrogen directly provided on the sea.     

Pressurized PEM water electrolysis: Efficiency and gas crossover

In this study the influence of cathodic and anodic pressures during polymer electrolyte membrane water electrolysis on the gas crossover is simulated and compared to in-situ measurements of the anodic hydrogen content at differential and balanced pressure operation. The efficiency losses due to the reduced Faraday efficiency caused by crossover, ohmic loss of the membrane and pressurized hydrogen and oxygen evolution are estimated. Therefore, the correlated dependencies on the current density, membrane thickness, anodic and cathodic pressures, membrane conductivity and permeabilities are quantified. In addition, pressurized electrolysis is compared to adiabatic and isothermal subsequent compression in focus of efficiency. The outcome of this study can be utilized as a powerful computational tool to optimize the membrane thickness with respect to the operating pressures.     

An electrochemical study of a PEM stack for water electrolysis

The electrochemical properties of a proton exchange membrane (PEM) stack electrolyzer (9 cells of 100 cm² geometrical area) were investigated at different temperatures. An amount of H₂ of ∼270 l h⁻¹ was produced at 60 A (600 mA cm⁻²) and 70 °C under 876 W of applied electrical power. The corresponding specific energy consumed in the process was 3.24 Wh·l⁻¹H₂. The Faradic and electrical efficiencies were determined. Overall stack efficiencies of 73% and 85%, at 60 A and 70 °C, with respect to the low and high heating value of hydrogen, respectively, were obtained. These results confirmed the successful scale-up of a previous lab-scale device.     

Optimizing hybrid offshore wind farms for cost-competitive hydrogen production in Germany

Nearly 96% of the world's current hydrogen production comes from fossil-fuel-based sources, contributing to global greenhouse gas emissions. Hydrogen is often discussed as a critical lever in decarbonizing future power systems. Producing hydrogen using unsold offshore wind electricity may offer a low-carbon production pathway and emerging business model. This study investigates whether participating in an ancillary service market is cost competitive for offshore wind-based hydrogen production. It also determines the optimal size of a hydrogen electrolyser relative to an offshore wind farm. Two flexibility strategies for offshore wind farms are developed in this study: an optimal bidding strategy into ancillary service markets for offshore wind farms that build hydrogen production facilities and optimal sizing of Power-to-Hydrogen (PtH) facilities at wind farms. Using empirical European power market and wind generation data, the study finds that offshore-wind based hydrogen must participate in ancillary service markets to generate net positive revenues at current levels of wind generation to become cost competitive in Germany. The estimated carbon abatement cost of “green” hydrogen ranges between 187 EUR/tonCO₂e and 265 EUR/tonCO₂e. Allowing hydrogen producers to receive similar subsidies as offshore wind farms that produce only electricity could facilitate further cost reduction. Utilizing excess and intermittent offshore wind highlights one possible pathway that could achieve increasing returns on greenhouse gas emission reductions due to technological learning in hydrogen production, even under conditions where low power prices make offshore wind less competitive in the European electricity market.     

Investigating the aerodynamic performance of a model offshore floating wind turbine

Understanding the impact of wave-induced dynamic effects on the aerodynamic performance of Offshore Floating Wind Turbines (OFWTs) is crucial towards developing cost-effective floating wind turbines to harness wind energy in deep water sites. The complexity of the wake of an OFWT has not yet been fully understood. Measurements and numerical simulations are essential. An experiment to investigate the aerodynamics of a model OFWT was undertaken at the University of Malta. Established experimental techniques used to analyse fixed HAWTs were applied and modified for the floating turbine condition. The effects of wave induced motions on the rotor aerodynamic variables were analysed in detail. An open source free-wake vortex code was also used to examine whether certain phenomena observed in the experiments could be reproduced numerically by the lifting line method. Results from hot wire measurements and free-wake vortex simulations have shown that for OFWTs surge-induced torque fluctuations are evident. At high λ a discrepancy in the mean C_P between the fixed and floating conditions was found from measurements and numerical simulations.     

Energy and exergy analyses of hydrogen production via solar-boosted ocean thermal energy conversion and PEM electrolysis

Energy and exergy analyses are reported of hydrogen production via an ocean thermal energy conversion (OTEC) system coupled with a solar-enhanced proton exchange membrane (PEM) electrolyzer. This system is composed of a turbine, an evaporator, a condenser, a pump, a solar collector and a PEM electrolyzer. Electricity is generated in the turbine, which is used by the PEM electrolyzer to produce hydrogen. A simulation program using Matlab software is developed to model the PEM electrolyzer and OTEC system. The simulation model for the PEM electrolyzer used in this study is validated with experimental data from the literature. The amount of hydrogen produced, the exergy destruction of each component and the overall system, and the exergy efficiency of the system are calculated. To better understand the effect of various parameters on system performance, a parametric analysis is carried out. The energy and exergy efficiencies of the integrated OTEC system are 3.6% and 22.7% respectively, and the exergy efficiency of the PEM electrolyzer is about 56.5% while the amount of hydrogen produced by it is 1.2 kg/h.     

Achieving high-efficiency hydrogen production using planar solid-oxide electrolysis stacks

Steam electrolysis in solid oxide electrolysis cells (SOECs) is considered as an effective method to achieve high-efficiency hydrogen production. In the present investigation, samples of 1-cell, 2-cell and 30-cell SOEC stacks were tested under electrolysis of steam to give a practical evaluation of the SOEC system efficiency of hydrogen production. The samples were tested at 800 °C under various operating conditions up to 500 h without significant degradation, and obtained steam conversion rates of 12.4%, 23% and 82.2% for the 1-cell, 2-cell and 30-cell stacks, respectively. System efficiencies of hydrogen production were calculated for the samples based on their real performance. A maximum efficiency value of 52.7% was achieved in the 30-cell stack.     

Investigation of multi-metal catalysts for stable hydrogen production via urea electrolysis

It has been shown that urea electrolysis is a viable method for wastewater remediation and simultaneous production of valuable hydrogen. Inexpensive nickel catalyst is optimal for the oxidation of urea in alkaline media but improvements are needed to minimize surface blockage and increase current density. Multi-metal catalysts were investigated by depositing platinum group metals on a nickel substrate. Rhodium and nickel proved synergistic to reduce surface blockage and increase catalyst stability. Rh-Ni electrodes reduced the overpotential for the electro-oxidation of urea and improved the current density by a factor of 200 compared to a Ni catalyst.     

H2 production by PEM electrolysis,assisted by textile effluent treatment and a solar photovoltaic cell

In this paper a new approach for H₂ production by PEM electrolysis, assisted by effluent treatment in the anolyte is proposed. H₂ is produced, in the catholyte, by proton reduction at a Fe-cathode, in an acid medium (1 M H₂SO₄). While in the anolyte, a mixture of Fe²⁺/Fe³⁺ is produced from the oxidation of an iron anode. The overall energy required (≤1.00 V) is less than that required by conventional water electrolysis, and is delivered by solar panels. In the anolyte, iron ions can be used in favor of a Fenton-type process, in the presence of H₂O₂. This approach is used in effluent treatment. The oxidation efficiency of dyes reactive black 5 (RB 5) and acid green 25 (AG 25) was investigated, in mild conditions, during H₂ production. The main experimental results show that it is possible to oxidize 0.00024 M RB 5 or 0.0002 M AG 25 in the anolyte, in 20 min.     

A geospatial method for estimating the levelised cost of hydrogen production from offshore wind

This paper describes the development of a general-purpose geospatial model for assessing the economic viability of hydrogen production from offshore wind power. A key feature of the model is that it uses the offshore project's location characteristics (distance to port, water depth, distance to gas grid injection point). Learning rates are used to predict the cost of the wind farm's components and electrolyser stack replacement. The notional wind farm used in the paper has a capacity of 510 MW. The model is implemented in a geographic information system which is used to create maps of levelised cost of hydrogen from offshore wind in Irish waters. LCOH values in 2030 spatially vary by over 50% depending on location. The geographically distributed LCOH results are summarised in a multivariate production function which is a simple and rapid tool for generating preliminary LCOH estimates based on simple site input variables.     

Hydrogen production by advanced proton exchange membrane (PEM) water electrolysers—Reduced energy consumption by improved electrocatalysis

Proton exchange membrane (PEM) water electrolysis systems offers several advantages over traditional technologies including greater energy efficiency, higher production rates, and more compact design. Normally in these systems, the anode has the largest overpotential at typical operating current densities. By development of the electrocatalytic material used for the oxygen evolving electrode, great improvements in efficiency can be made. We find that using cyclic voltammetry and steady state polarisation analysis, enables us to separate the effects of true specific electrocatalytic activity and active surface area. Understanding these two factors is critical in developing better electrocatalytic materials in order to further improve the performance of PEM water electrolysis cells. The high current performance of a PEM water electrolysis cell using these oxides as the anode electrocatalyst has also been examined by steady state polarisation measurements and electrochemical impedance spectroscopy. Overall the best cell voltage obtained is 1.567 V at 1 A cm⁻² and 80 °C was achieved when using Nafion 115 as the electrolyte membrane.     

Simulation of a hydrogen production and purification system for a PEM fuel-cell using bioethanol as raw material

A process to produce “fuel-cell grade” hydrogen from ethanol steam reforming is analyzed from a thermodynamic point of view. The hydrogen purification process consists of WGS and COPROX reactors. Equations to evaluate the efficiency of the system, including the fuel cell, are presented. A heat exchange network is proposed in order to improve the exploitation of the available power. The effect of key variables such as the reformer temperature and the ethanol/water molar feed ratio on the fuel-cell efficiency is discussed. Results show that it is feasible to carry out the energy integration of the hydrogen catalytic production and purification—PEM fuel-cell system, using ethanol as raw material. The technology of “fuel-cell grade” hydrogen production using ethanol as raw material is a very attractive alternative to those technologies based in fossil fuels.     

On the production of hydrogen via alkaline electrolysis during off-peak periods

This article studies the opportunity for producing hydrogen via alkaline electrolysis from electricity consumption during off-peak periods. Two aspects will be discussed: electricity spot markets and nuclear electricity production in France.

From a market point of view, when there is a significant fluctuation in electricity prices, the use of an electrolysis installation during off-peak periods makes it possible to make quite considerable savings in production costs. Savings vary enormously from one market to the next; some highly fluctuating markets offer very low off-peak prices and allow for viable hydrogen production, even if average electricity prices first appear to be quite high. Very fluctuating spot prices market may be difficult to predict and makes operations of an electrolysis installation more complicated and risky. For other more stable markets, the use of an electrolysis installation during off-peak periods does not appear to be a relevant proposition.

From the point of view of French electricity production, the availability of current nuclear power plants and the estimation of available energy for mass production of hydrogen show that the installations studied would not be viable. For “peak period” use, it would certainly be more useful to have electrolysers with a lower investment proportion, even if this means slightly higher operating costs. Research into large-capacity electrolysers should, therefore, both develop low-production-cost electrolysers, for use in base load mode where dedicated production means are concerned, and highly flexible electrolysers, with low investment costs, which could easily be viable with low rates of use.