考虑制氢效率特性的风氢系统容量优化

针对利用风电制氢导致电解槽间歇式运行的问题,提出了考虑制氢效率特性的风氢系统容量配置优化方法。首先研究了电解槽的制氢效率特性,评估电解槽的最优工作区间;在此基础上,采取电网辅助购电策略,维持电解槽的最优运行;考虑售电收益、售氢收益、投资运维成本和弃风成本,以风氢系统联合收益最大化为目标,计及风氢系统稳定运行约束和风电出力爬坡约束,合理地分配风电上网功率和制氢功率。文章联合风电外送输电工程进行了风氢系统容量配置优化,为风氢系统的容量优化提供新思路。     

Unit sizing and cost analysis of stand-alone hybrid wind/PV/fuel cell power generation systems

An economic evaluation of a hybrid wind/photovoltaic/fuel cell (FC) generation system for a typical home in the Pacific Northwest is performed. In this configuration the combination of a FC stack, an electrolyser, and hydrogen storage tanks is used as the energy storage system. This system is compared to a traditional hybrid energy system with battery storage. A computer program has been developed to size system components in order to match the load of the site in the most cost effective way. A cost of electricity, an overall system cost, and a break-even distance analysis are also calculated for each configuration. The study was performed using a graphical user interface programmed in MATLAB.     

Optimal techno-enviro-economic analysis of a hybrid grid connected tidal-wind-hydrogen energy system

The study deals with the techno-enviro-economic aspects of hydrogen production using polymer electrolyte membrane electrolysers powered by a hybrid grid-connected tidal-wind energy system. System modelling is presented initially. The energy management strategies for hydrogen production are then analysed as rule-based approach and as optimised approach. An objective function to maximise the operating profit under optimal system operation is formulated considering the variable energy costs, capital and maintenance expenditure, and real system constraints. A comprehensive cost analysis of the system is obtained by comparing two different optimisation approaches based on fixed cost and levelised cost factors, respectively. Towards reaching this goal, the use of mixed integer genetic algorithm optimisation is investigated. The operation of electrolyser in terms of its different operating modes, namely stop, running, and stand-by is presented. The dynamic optimisation of an electrolyser capable of working at up to twice its nominal rating for a limited duration is also analysed in the study. The results of the optimisation approach are 41.5% and 47% higher than the rule-based approach in terms of the annualised profit and carbon emission savings, respectively. In addition, the recurrent switching of electrolyser unit operating modes is avoided with the optimisation approach, reducing the associated energy consumption of about 27.2 MWh annually. The proposed model can be used as a generic tool for hydrogen production analysis under different contexts and it is especially applicable in high green energy potential sites with constrained grid facilities.     

Optimal energy management strategy of fuel-cell battery hybrid electric mining truck to achieve minimum lifecycle operation costs

Proton exchange membrane fuel cell (PEMFC) electric vehicle is an effective solution for improving fuel efficiency and onboard emissions, taking advantage of the high energy density and short refuelling time. However, the higher cost and short life of the PEMFC system and battery in an electric vehicle prohibit the fuel cell electric vehicle (FCEV) from becoming the mainstream transportation solution. The fuel efficiency-oriented energy management strategy (EMS) cannot guarantee the improvement of total operating costs. This paper proposes an EMS to minimize the overall operation costs of FCEVs, including the cost of hydrogen fuel, as well as the cost associated with the degradations of the PEMFC system and battery energy storage system (ESS). Based on the PEMFC and battery performance degradation models, their remaining useful life (RUL) models are introduced. The control parameters of the EMS are then optimized using a meta-model based global optimization algorithm. This study presents a new optimal control method for a large mining truck operating on a real closed-road operation cycle, using the combined energy efficiency and performance degradation cost measures of the PEMFC system and lithium-ion battery ESS. Simulation results showed that the proposed EMS could improve the total operating costs and the life of the FCEV.     

A flexible analytical model for operational investigation of solar hydrogen plants

Hydrogen will become a dominant energy carrier in the future and the efficiency and lifetime cost of its production through water electrolysis is a major research focus. Alongside efforts to offer optimum solutions through plant design and sizing, it is also necessary to develop a flexible virtualised replica of renewable hydrogen plants, that not only models compatibility with the “plug-and-play” nature of many facilities, but that also identifies key elements for optimisation of system operation. This study presents a model for a renewable hydrogen production plant based on real-time historical and present-day datasets of PV connected to a virtualised grid-connected AC microgrid comprising different technologies of batteries, electrolysers, and fuel cells. Mathematical models for each technology were developed from chemical and physical metrics of the plant. The virtualised replica is the first step toward the implementation of a digital twin of the system, and accurate validation of the system behaviour when updated with real-time data. As a case study, a solar hydrogen pilot plant consisting of a 60 kW Solar PV, a 40 kW PEM electrolyser, a 15 kW LIB battery and a 5 kW PEM fuel cell were simulated and analysed. Two effective operational factors on the plant's performance are defined: (i) electrolyser power settings to determine appropriate hydrogen production over twilight periods and/or overnight and (ii) a user-defined minimum threshold for battery state of charge to prevent charge depletion overnight if the electrolyser load is higher than its capacity. The objective of this modelling is to maximise hydrogen yield while both loss of power supply probability (LPSP) and microgrid excess power are minimised. This analysis determined: (i) a hydrogen yield of 38–39% from solar DC energy to hydrogen energy produced, (ii) an LPSP <2.6 × 10^?4 and (iii) < 2% renewable energy lost to the grid as excess electricity for the case study.     

Prospects for solar only operation of the hybrid sulphur cycle for hydrogen production

The hybrid sulphur process is one of the most promising thermochemical water splitting cycles for large scale hydrogen production. While the process includes an electrolysis step, the use of sulphur dioxide in the electrolyser significantly reduces the electrical demand compared to conventional alkaline electrolysis. Solar operation of the cycle with zero emissions is possible if the electricity for the electrolyser and the high temperature thermal energy to complete the cycle are provided by solar technologies.This paper explores the possible use of photovoltaics (PV) to supply the electrical demand and examines a number of configurations. Production costs are determined for several scenarios and compared with base cases using conventional technologies. The hybrid sulphur cycle has promise in the medium term as a viable zero carbon production process if PV power is used to supply the electrolyser. However, the viability of this process is dependent on a market for hydrogen and a significant reduction in PV costs to around $1/W_p.     

Flexible production of green hydrogen and ammonia from variable solar and wind energy: Case study of Chile and Argentina

We report a techno-economic modelling for the flexible production of hydrogen and ammonia from water and optimally combined solar and wind energy. We use hourly data in four locations with world-class solar in the Atacama desert and wind in Patagonia steppes. We find that hybridization of wind and solar can reduce hydrogen production costs by a few percents, when the effect of increasing the load factor on the electrolyser overweighs the electricity cost increase. For ammonia production, the gains by hybridization can be substantially larger, because it reduces the power variability, which is costly, due to the need for intermediate storage of hydrogen between the flexible electrolyser and the less flexible ammonia synthesis unit. Our modelling reveals the crucial role in the synthesis of flexibility, which cuts the cost of variability, especially for the more variable wind power. Our estimated near-term production costs for green hydrogen, around 2 USD/kg, and green ammonia, below 500 USD/t, are encouragingly close to competitiveness against fossil-fuel alternatives.     

Power-to-liquid hydrogen: Exergy-based evaluation of a large-scale system

Hydrogen as an energy vector is seen as a key for the energy transition. Recently, more than 30 countries have launched their hydrogen strategies and roadmaps. Hydrogen storage and transportation are challenging steps of the hydrogen economy since all available options have significant drawbacks. This paper evaluates a power-to-liquid hydrogen process; the system is “charged” with electricity from renewable sources to produce hydrogen via water electrolysis; the produced hydrogen gas is liquefied and stored at ambient pressure and cryogenic temperature. The purpose of this paper is to report the first evaluation results of a system including a polymer electrolyte membrane electrolyser and a hydrogen liquefier. The evaluation was conducted using exergy-based methods, i.e. exergetic, exergoeconomic and exergoenvironmental analyses. The process of hydrogen liquefaction was simulated with the aid of the Aspen Plus software. The exergetic efficiencies for the liquefaction process and for the electrolyser are 42% and 47%, respectively. While the total exergetic efficiency of the power-to-liquid hydrogen system amounts to 44%. The total exergy destruction for the liquefier amounts to 9.3 MW and for the polymer electrolyser membrane electrolyser amounts to 19.3 MW. The electrolyser followed by the hydrogen compressors were identified as the components with the highest exergy destruction values and investment costs, while the compressors and the recuperators account for the highest exergoenvironmental impact. The sensitivity analysis shows that the specific liquefaction cost of hydrogen strongly varies with the electricity price and the cost of green hydrogen.     

The development of a PEMFC hybrid power electric vehicle with automatic sodium borohydride hydrogen generation

This paper describes the development of a hybrid Proton Exchange Membrane Fuel Cell (PEMFC) electric vehicle consisting of a 3 kW PEMFC, PV arrays, secondary battery sets, and a chemical hydrogen generation system. We first integrate a hybrid PEMFC electric vehicle and design power management strategies. The on-board hydrogen generation system can provide sufficient hydrogen for continuous operation of the PEMFC, and the performance tests demonstrate the effectiveness of the integrated system in providing sustainable power for driving. We then use Matlab/SimPowerSystem? to develop a simulation model and adjust the model parameters using experimental data. The results indicated that the model can effectively predict system responses and can be used for performance evaluation. We also use the simulation model to estimate the mileage and costs of the developed electric vehicle, and we discuss the impacts of component sizes on system costs and travelling ranges.     

Reducing the hydrogen production cost by operating alkaline electrolysis as a discontinuous process in the French market context

The possible reduction of the hydrogen production cost when operating alkaline electrolysers in a discontinuous way, in order to benefit from low electricity prices, is investigated. Beside the insights about the electricity market (prices do not correlate the demand; they are related to the supply-and-demand hardness), advances in modelling discontinuous operation are proposed. An optimum production cost is found that induces a profit of 4%, with regard to a plant that would work continuously. Specific attention should be given to related overcosts: additional degradation due to frequent transitions from the minimum electrolyser load to the nominal one, higher maintenance needs, and hydrogen storage costs. Such an operating mode would also greatly benefit from a reduction of the electrolyser prices. However, the state-of-the-art as regards the electrolyser minimum loads and transition time appears satisfactory.     

Rapid sizing of a hydrogen-battery storage for an offshore wind farm using convex programming

This paper carries out a comprehensive analysis on an offshore wind farm equipped with a hybrid storage comprised of hydrogen and battery, from the perspective of economic effectiveness. To rapidly evaluate the system economy, a computationally efficient convex program that takes the nonlinear storage efficiencies into account is provided, which can simultaneously and synergistically optimize the storage sizing and energy management over a long offshore wind cycle. In the analysis, a case study on the optimal configuration and operation of the hybrid storage is thoroughly investigated, answering what the scalings are and how the storage functions in the offshore wind farm. Comparisons to other offshore wind farms with none or only one storage type further demonstrate the advantage of combining hydrogen plant and battery. Influences of the offshore wind electricity price of grid parity and hydrogen price on the system economies, in the terms of total annual cost, net annual profit and hydrogen production cost, are also discussed, revealing sensitivity and dependency of the scalings. Finally, this paper presents the future potential of applying hydrogen plant in the offshore wind farm, from the angles of hydrogen production cost and energy saving.     

Dynamic modeling of hybrid energy storage systems coupled to photovoltaic generation in residential applications

A model of a photovoltaic (PV) powered residence in stand-alone configuration was developed and evaluated. The model assesses the sizing, capital costs, control strategies, and efficiencies of reversible fuel cells (RFC), batteries, and ultra-capacitors (UC) both individually, and in combination, as hybrid energy storage devices. The choice of control strategy for a hybrid energy storage system is found to have a significant impact on system efficiency, hydrogen production and component utilization. A hybrid energy storage system comprised of batteries and RFC has the advantage of reduced cost (compared to using a RFC as the sole energy storage device), high system efficiency and hydrogen energy production capacity. A control strategy that preferentially used the RFC before the battery in meeting load demand allows both grid independent operation and better RFC utilization compared to a system that preferentially used the battery before the RFC. Ultra-capacitors coupled with a RFC in a hybrid energy storage system contain insufficient energy density to meet dynamic power demands typical of residential applications.     

Techno-economic assessment of hydrogen production from seawater

Population growth and the expansion of industries have increased energy demand and the use of fossil fuels as an energy source, resulting in release of greenhouse gases (GHG) and increased air pollution. Countries are therefore looking for alternatives to fossil fuels for energy generation. Using hydrogen as an energy carrier is one of the most promising alternatives to replace fossil fuels in electricity generation. It is therefore essential to know how hydrogen is produced. Hydrogen can be produced by splitting the water molecules in an electrolyser, using the abondand water resources, which are covering around ? of the Earth's surface. Electrolysers, however, require high-quality water, with conductivity in the range of 0.1–1 μS/cm. In January 2018, there were 184 offshore oil and gas rigs in the North Sea which may be excellent sites for hydrogen production from seawater. The hydrogen production process reported in this paper is based on a proton exchange membrane (PEM) electrolyser with an input flow rate of 300 L/h. A financially optimal system for producing demineralized water from seawater, with conductivity in the range of 0.1–1 μS/cm as the input for electrolyser, by WAVE (Water Application Value Engine) design software was studied. The costs of producing hydrogen using the optimised system was calculated to be US$3.51/kg H₂. The best option for low-cost power generation, using renewable resources such as photovoltaic (PV) devices, wind turbines, as well as electricity from the grid was assessed, considering the location of the case considered. All calculations were based on assumption of existing cable from the grid to the offshore, meaning that the cost of cables and distribution infrastructure were not considered. Models were created using HOMER Pro (Hybrid Optimisation of Multiple Energy Resources) software to optimise the microgrids and the distributed energy resources, under the assumption of a nominal discount rate, inflation rate, project lifetime, and CO₂ tax in Norway. Eight different scenarios were examined using HOMER Pro, and the main findings being as follows:The cost of producing water with quality required by the electrolyser is low, compared with the cost of electricity for operation of the electrolyser, and therefore has little effect on the total cost of hydrogen production (less than 1%).The optimal solution was shown to be electricity from the grid, which has the lowest levelised cost of energy (LCOE) of the options considered. The hydrogen production cost using electricity from the grid was about US$ 5/kg H₂.Grid based electricity resulted in the lowest hydrogen production cost, even when costs for CO₂ emissions in Norway, that will start to apply in 2025 was considered, being approximately US$7.7/kg H₂.From economical point of view, wind energy was found to be a more economical than solar.     

Comparison of hydrogen storage with diesel-generator system in a PV–WEC hybrid system

Hydrogen as a storage medium in renewable energy systems has been the subject of various studies in recent years. Such a system consists of a long-term and a short-term storage system. In a battery, energy is stored for short term whereas the electrolyser, H₂-tank and fuel cell combination is used for long-term energy storage to increase the reliability of supply. The same purpose can be achieved by introducing a diesel generator instead of long-term storage. The advantage of such a system is that it needs low investment cost. However, the main disadvantage is that it needs to supply fuel for the operation of the generator. The advantage of hydrogen-based long-term storage over a diesel generator is that it does not need any supply of fuel. In photovoltaic–wind–diesel hybrid systems, the surplus energy during the good season is not stored.In the present study, the possible sites for renewable applications are specified depending on the seasonal renewable energy variation and fuel cost at the site of application. The critical fuel cost is calculated depending on the seasonal solar and wind energy difference. The actual fuel cost at the site of application is compared with critical fuel cost. To find out the actual fuel cost at the location of application, the transportation cost is also included. If the actual fuel cost is higher than the critical fuel cost, the location is cost-effective for hydrogen-based storage. Otherwise, the site is suitable for a diesel-generator backup system. It is found that at present hydrogen storage is not cost-effective compare to a diesel-generator-based system. In the near future when the target cost of the electrolyser and the fuel cell is achieved, the scope of the hydrogen-based storage system will also increase and it will also be cost competitive with diesel-generator system for remote applications.     

Numerical analysis of an energy storage system based on a metal hydride hydrogen tank and a lithium-ion battery pack for a plug-in fuel cell electric scooter

This work investigates on the performance of a hybrid energy storage system made of a metal hydride tank for hydrogen storage and a lithium-ion battery pack, specifically conceived to replace the conventional battery pack in a plug-in fuel cell electric scooter. The concept behind this solution is to take advantage of the endothermic hydrogen desorption in metal hydrides to provide cooling to the battery pack during operation.The analysis is conducted numerically by means of a finite element model developed in order to assess the thermal management capabilities of the proposed solution under realistic operating conditions.The results show that the hybrid energy storage system is effectively capable of passively controlling the temperature of the battery pack, while enhancing at the same time the on-board storage energy density. The maximum temperature rise experienced by the battery pack is around 12 °C when the thermal management is provided by the hydrogen desorption in metal hydrides, against a value above 30 °C obtained for the same case without thermal management. Moreover, the hybrid energy storage system provides the 16% of the total mass of hydrogen requested by the fuel cell stack during operation, which corresponds to a significant enhancement of the hydrogen storage capability on-board of the vehicle.     

Simulation-based sensitivity analysis of an on-site hydrogen production unit in Hungary

This article examines the additional profit that can be achieved with the integrated operation of an on-site electrolyser, a hydrogen tank, a photovoltaic system, and a wind power plant based on Hungarian data from 2019. The results of the optimisation show that the system economically reduces the volatility of weather-dependent renewable production, so there is a promising demand-side management potential in coordination. We found that the operating profit is highest in April at EUR 19,416, 18,932 in July, and lowest at EUR 17,075 in January. The production curve of photovoltaic capacities is better matched to fuel demand, so increasing the share of solar energy results in lower balancing activity but higher profits. Increasing the size of the hydrogen storage and electrolyser, with constant hydrogen demand and prices, will cause a convergent increase in profits, however above a 10 kg storage capacity or 350 kW electrolyser capacity there is no substantial profit increase. In the case of the economically optimal asset size, there is a slight competition between the electricity market and the hydrogen distribution activity. The choice between the two activities depends on current electricity and hydrogen prices and the cost of unmet hydrogen demand.     

Long-term optimization based on PSO of a grid-connected renewable energy/battery/hydrogen hybrid system

This paper presents and evaluates three energy management systems (EMSs) based on Particle Swarm Optimization (PSO) for long-term operation optimization of a grid-connected hybrid system. It is composed of wind turbine (WT) and photovoltaic (PV) panels as primary energy sources, and hydrogen system (fuel cell –FC–, electrolyzer and hydrogen storage tank) and battery as energy storage system (ESS). The EMSs are responsible for making the hybrid system produce the demanded power, deciding on the energy dispatch among the ESS devices. The first PSO-based EMS tries to minimize the ESS utilization costs, the second one to maximize the ESS efficiency, and the third one to optimize the lifetime of the ESS devices. Long-term simulations of 25 years (expected lifetime of the hybrid system) are shown in order to demonstrate the right performance of the three EMSs and their differences. The simulations show that: 1) each EMS outperforms the others in the designed target; and 2) the third EMS is considered the best EMS, because it needs the least ESS devices, and presents the lowest total acquisition cost of hybrid system, whereas the rest of parameters are similar to the best values obtained by the other EMSs.     

An optimum dispatch strategy using set points for a photovoltaic (PV)–diesel–battery hybrid power system

This paper presents dispatch strategies for the operation of a solar photovoltaic (PV)–diesel–battery hybrid power system using ‘set points’. This includes determination of the optimum values of set points for the starting and stopping of the diesel generator to minimise the overall system costs. A computer program for a typical dispatch strategy has been developed to predict the long-term energy performance and the lifecycle cost of the system.     

Transient electrolyser response in a renewable-regenerative energy system

In a renewable-regenerative electrolyser/fuel-cell system, the electrolyser performs the critical function of converting excess renewable input energy into hydrogen. Electrolyser operation on time scales and duty cycles that are relevant to common renewable resources (e.g., wind and solar) were probed using an experimental residential-scale system. Experimental results indicate that the electrolyser's transient characteristics have a significant impact on the efficiency of the conversion process. Two key findings are presented. First, a reduction in electrolyser hydrogen production, relative to steady-state levels, is observed due to the thermal transient and time-dependent decay in current draw. These time-dependent aspects are typically not addressed in the theoretical models proposed to date for electrolyser operation. Second, it was found that maintaining a minimum electrolyser current is critical to avoid performance decline induced by dynamic operation. The requirement for a minimum operating current (and therefore minimum power input) places constraints on the common operating methodology for renewable-regenerative systems.     

Sustainability of hydrogen refuelling stations for trains using electrolysers

Hydrogen has the potential to become a powerful energy vector with different applications in many sectors (industrial, residential, transportation and other applications) as it offers a clean, sustainable, and flexible alternative. Hydrogen trains use compressed hydrogen as fuel to generate electricity using a hybrid system (combining fuel cell and batteries) to power traction motors and auxiliaries. This hydrogen trains are fuelled with hydrogen at the central train depot, like diesel locomotives. The main goal of this paper is to perform a techno-economic analysis for a hydrogen refuelling stations using on-site production, based on PEM electrolyser technology in order to supply hydrogen to a 20 hydrogen-powered trains captive fleet. A sensitivity analysis on the main parameters will be performed as well, in order to acquire the knowledge required to take any decisions on implementation regarding electricity cost, hydrogen selling price, number of operation hours and number of trains for the captive fleet.The main methodology considers the evaluation of the project based on the Net Present Value calculation and the sensitivity analysis through standard method using Oracle Crystal Ball. The main result shows that the use of hydrogen as an alternative fuel for trains is a sustainable and profitable solution from the economic, environmental and safety points of view.The economic analysis concludes with the need to negotiate an electricity cost lower than 50 €/MWh, in order to be able to establish the hydrogen selling price at a rate higher than 4.5€/kg. The number of operating hours should be higher than 4800 h per year, and the electrolyser system capacity (or hydrogen refuelling station capacity) should be greater than 3.5 MW in order to reach a Net Present Value of 7,115,391 € with a Return of Investment set to 9 years. The result of the multiparametric sensitivity analysis for the Net Present Value (NPV) shows an 85.6% certainty that the project will have a positive result (i.e. profitability) (NPV> 0). The two main variables with the largest impact on Net Present Value are the electrolyser capacity (or hydrogen refuelling station capacity) and the hydrogen selling price. Moreover, a margin of improvement (higher NPV) could be reached with the monetization of the heat, oxygen by-product and CO₂ emission reduction.