Optimal design of wind-powered hydrogen refuelling station for some selected cities of South Africa

The transport sector is considered as one of the sectors producing high carbon emissions worldwide due to the use of fossil fuels. Hydrogen is a non-toxic energy carrier that could serve as a good alternative to fossil fuels. The use of hydrogen vehicles could help reduce carbon emissions thereby cutting down on greenhouse gases and environmental pollution. This could largely be achieved when hydrogen is produced from renewable energy sources and is easily accessible through a widespread network of hydrogen refuelling stations. In this study, the techno-economic assessment was performed for a wind-powered hydrogen refuelling station in seven cities of South Africa. The aim is to determine the optimum configuration of a hydrogen refuelling station powered by wind energy resources for each of the cities as well as to determine their economic viability and carbon emission reduction capability. The stations were designed to cater for 25 hydrogen vehicles every day, each with a 5 kg tank capacity. The results show that a wind-powered hydrogen refuelling station is viable in South Africa with the cost of hydrogen production ranging from 6.34 $/kg to 8.97 $/kg. These costs are competitive when compared to other costs of hydrogen production around the world. The cities located in the coastal region of South Africa are more promising for siting wind powered-hydrogen refuelling station compared to the cities located on the mainland. The hydrogen refuelling stations could reduce the CO₂ and CO emissions by 73.95 tons and 0.133 tons per annum, respectively.     

Safety studies of a hydrogen refuelling station: Determination of the occurrence frequency of the accidental scenarios

At present, the hydrogen vehicles technology appears to have future prospective for reduction in greenhouse gas emissions. Nevertheless, the development of such a technology requires appropriate infrastructures for production, storage and refuelling stages in a refuelling station. This one presents safety challenges due to the hydrogen chemicophysical characteristics. So, to avoid hazards, it is necessary to implement safety practices that, if early adopted in the development of a fuelling station project, can allow very low impact, safety being incorporated in the project itself. However, a drawback is the not sufficient experience and the scarcity of the relevant data collection. To deepen studies about the risk in the above mentioned field, in this paper, for the moment, safety analyses of a high-pressure storage equipment in hydrogen gas refuelling station have been carried out by the integrated use of FMEA, HAZOP and FTA techniques. The work is intended to assess if the refuelling station design taken into consideration is safe enough, at least from the occurrence frequency point of view, as well to constitute a basis for further more refined studies which also consider the consequences aspects, allowing the plant risk assessment.     

Refuelling scenarios of a light urban fuel cell vehicle with metal hydride hydrogen storage. Comparison with compressed hydrogen storage counterpart

The high price of hydrogen fuel in the fuel cell vehicle refuelling market is highly dependent on the one hand from the production costs of hydrogen and on the other from the capital cost of a hydrogen refuelling station's components to support a safe and adequate refuelling process of contemporary fuel cell vehicles. The hydrogen storage technology dominated in the vehicle sector is currently based on high-pressure compressed hydrogen tanks to extend as much as possible the driving range of the vehicles. However, this technology mandates the use of large hydrogen compression and cooling systems as part of the refuelling infrastructure that consequently increase the final cost of the fuel. This study investigated the prospects of lowering the refuelling cost of small urban hydrogen vehicles through the utilisation of metal hydride hydrogen storage. The results showed that for low compression hydrogen storage, metal hydride storage is in favour in terms of the dispensed hydrogen fuel price, while its weight is highly comparable to the one of a compressed hydrogen tank. The final refuelling cost from the consumer's perspective however was found to be higher than the compressed gas due to the increased hydrogen quantity required to be stored in fully empty metal hydride tanks to meet the same demand.     

Design of a solar hydrogen refuelling station following the development of the first Croatian fuel cell powered bicycle to boost hydrogen urban mobility

Hydrogen refuelling stations are important for achieving sustainable hydrogen economy in low carbon transport and fuel cell electric vehicles. The solution presented in this paper provides us with a technology for producing carbon dioxide free hydrogen, which is an approach that goes beyond the existing large-scale hydrogen production technologies that use fossil fuel reforming. Hence, the main goal of this work was to design a hydrogen refuelling station to secure the autonomy of a hydrogen powered bicycle. The bicycle hydrogen system is equipped with a proton exchange membrane fuel cell stack of 300 W, a DC/DC converter, and a metal hydride storage tank of 350 NL of hydrogen. The hydrogen power system was made of readily available commercial components. The hydrogen station was designed as an off-grid system in which the installed proton exchange membrane electrolyzer is supplied with electric energy by direct conversion using photovoltaic cells. With the hydrogen flow rate of 2000 cc min⁻¹ the hydrogen station is expected to supply at least 5 bicycles to be used in 20 km long city tourist routes.     

Techno-economic assessment of a hydrogen refuelling station powered by an on-grid photovoltaic solar system: A case study in Morocco

The present work sheds light on the green hydrogen future in Morocco. A detailed techno-economic assessment and evaluation of a hydrogen refuelling station powered by an on-grid photovoltaic system are presented and discussed. This station is designed to supply the fleet of taxis in a Moroccan city by assuming different scenarios to replace the current taxi system with fuel-cell electric vehicles. A model is proposed to estimate the daily demand for hydrogen, which is used to determine the sizing of the station's components. An economic analysis is then conducted to calculate the cost of hydrogen production. The technical results demonstrate that about 152 kg/day is required to supply the total fleet, while only 30.4 kg/day is enough to provide 20%. It is also found that the costs of hydrogen produced are inversely proportional to the capacity of the hydrogen refuelling station, and the hydrogen cost is about 9.18 $/kg for the larger station and 12.56 $/kg for the smaller one. The proposed system offers an attractive solution to enhance the country's development and reduce the consumption of hydrocarbon fuels.     

Experimental study on hydrogen explosions in a full-scale hydrogen filling station model

In order for fuel cell vehicles to develop a widespread role in society, it is essential that hydrogen refuelling stations become established. For this to happen, there is a need to demonstrate the safety of the refuelling stations. The work described in this paper was carried out to provide experimental information on hydrogen outflow, dispersion and explosion behaviour. In the first phase, homogeneous hydrogen–air mixtures of a known concentration were introduced into an explosion chamber and the resulting flame speed and overpressures were measured. Hydrogen concentration was the dominant factor influencing the flame speed and overpressure. Secondly, high-pressure hydrogen releases were initiated in a storage room to study the accumulation of hydrogen. For a steady release with a constant driving pressure, the hydrogen concentration varied as the inlet airflow changed, depending on the ventilation area of the room, the external wind conditions and also the buoyancy induced flows generated by the accumulating hydrogen. Having obtained this basic data, the realistic dispersion and explosion experiments were executed at full-scale in the hydrogen station model. High-pressure hydrogen was released from 0.8 to 8.0 mm nozzle at the dispenser position and inside the storage room in the full-scale model of the refuelling station. Also the hydrogen releases were ignited to study the overpressures that can be generated by such releases. The results showed that overpressures that were generated following releases at the dispenser location had a clear correlation with the time of ignition, distance from ignition point.     

Techno-economical evaluation of a hydrogen refuelling station powered by Wind-PV hybrid power system: A case study for İzmir-Çeşme

Hydrogen fuelling station is an infrastructure for the commercialisation of hydrogen energy utilising fuel cells, particularly, in the automotive sector. Hydrogen fuel produced by renewable sources such as the solar and wind energy can be an alternative fuel to depress the use of fuels based on fossil sources in the transport sector for sustainable clean energy strategy in future. By replacing the primary fuel with hydrogen fuel produced using renewable sources in road transport sector, environmental benefits can be achieved. In the present study, techno-economic analysis of hydrogen refuelling station powered by wind-photovoltaics (PV) hybrid power system to be installed in ?zmir-Çe?me, Turkey is performed. This analysis is carried out to a design of hydrogen refuelling station which is refuelling 25 fuel cell electric vehicles on a daily basis using hybrid optimisation model for electric renewable (HOMER) software. In this study, National Aeronautics and Space Administration (NASA) surface meteorology and solar energy database were used. Therefore, the average wind speed during the year was assessed to be 5.72 m/s and the annual average solar irradiation was used to be 5.08 kW h/m²/day for the considered site. According to optimisation results obtained for the proposed configuration, the levelised cost of hydrogen production was found to be US $7.526–7.866/kg in different system configurations. These results show that hydrogen refuelling station powered by renewable energy is economically appropriate for the considered site. It is expected that this study is the pre-feasibility study and obtained results encougare the hydrogen refuelling station to be established in Turkey by inventors or public institutions.     

全球加氢站产业、技术及标准进展综述

以美国、欧洲、日本、中国的加氢站作为考察对象,就产业投资运营、主要设备商、相关标准进行梳理,结果表明：在加氢站投资及运营管理方面,美国、欧洲、日本具有较为成熟的经验;在氢增压、储存、加注等技术方面,德国、日本保持领先地位。在诸多氢气和液氢的技术领域,美国保持领先地位;在一些细分技术领域,英国、法国、挪威、俄罗斯具有优势;在加氢站标准方面,美国、日本具有较为完善的标准体系。中国已解决70 MPa氢气增压、加注、储存等领域的部分技术难题,但与其他国家相比,离子液式氢压缩机、液氢泵、液氢储罐、液氢加氢枪等产品的研发仍需持续推进。     

The simulation and analysis of leakage and explosion at a renewable hydrogen refuelling station

The number of hydrogen refuelling stations (HRSs) is steadily growing worldwide. In China, the first renewable hydrogen refuelling station has been built in Dalian for nearly 3 years. FLACS software based on computational fluid dynamics approach is used in this paper for simulation and analysis on the leakage and explosion of hydrogen storage system in this renewable hydrogen refuelling station. The effects of wind speed, leakage direction and wind direction on the consequences of the accident are analyzed. The harmful area, lethal area, the farthest harmful distance and the longest lethal distance in explosion accident of different accident scenarios are calculated. Harmful areas after explosion of different equipments in hydrogen storage system are compared. The results show that leakage accident of the 90 MPa hydrogen storage tank cause the greatest harm in hydrogen explosion. The farthest harmful distance caused by explosion is 35.7 m and the farthest lethal distance is 18.8 m in case of the same direction of wind and leakage. Moreover, it is recommended that the hydrogen tube trailer should not be parked in the hydrogen refuelling station when the amount of hydrogen is sufficient.     

Improving hydrogen refueling stations to achieve minimum refueling costs for small bus fleets

Fuel cell vehicles using green hydrogen as fuel can contribute to the mitigation of climate change. The increasing utilization of those vehicles creates the need for cost efficient hydrogen refueling stations. This study investigates how to build the most cost efficient refueling stations to fuel small fleet sizes of 2, 4, 8, 16 and 32 fuel cell busses. A detailed physical model of a hydrogen refueling station was built to determine the necessary hydrogen storage size as well as energy demand for compression and precooling of hydrogen. These results are used to determine the refueling costs for different station configurations that vary the number of storage banks, their volume and compressor capacity.It was found that increasing the number of storage banks will decrease the necessary total station storage volume as well as energy demand for compression and precooling. However, the benefit of adding storage banks decreases with each additional bank. Hence the cost for piping and instrumentation to add banks starts to outweigh the benefits when too many banks are used. Investigating the influence of the compressor mass flow found that when fueling fleets of 2 or 4 busses the lowest cost can be reached by using a compressor with the minimal mass flow necessary to refill all storage banks within 24 h. For fleets of 8, 16 and 32 busses, using the compressor with the maximum investigated mass flow of 54 kg/h leads to the lowest costs.     

Effects of congestion and confining walls on turbulent deflagrations in a hydrogen storage facility-part 1: Experimental study

If the general public is to use hydrogen as a vehicle fuel, customers must be able to handle hydrogen with the same degree of confidence, and with comparable risk, as conventional liquid and gaseous fuels. Since hydrogen is stored and used as a high-pressure gas, a jet release in a confined or congested area can create an explosion hazard. Therefore, hazards associated with jet releases from leaks in a vehicle-refuelling environment must be considered. As there was insufficient knowledge of the explosion hazards, a study was initiated to gain a better understanding of the potential explosion hazard consequences associated with high-pressure leaks from hydrogen vehicle refuelling systems. Our first paper [1] describes the release and subsequent ignition of a high-pressure hydrogen jet in a simulated dispensing area of a hydrogen vehicle refuelling station. In the present paper, an array of dummy storage cylinders with confining walls (to represent isolation from the forecourt area) was used to represent high-pressure hydrogen cylinder storage congestion. Experiments with ignition of premixed 5.4 m × 6.0 m × 2.5 m hydrogen-air clouds and hydrogen jet releases up to 40 MPa pressures were performed. The results are presented and discussed in relation to the conditions giving the highest overpressures. We concluded from the study that the ignition of a jet release gives much higher local overpressure than in the case of ignition of a homogeneous mixture inside the cylinder storage congestion area. The modelling of these results will be presented in Part 2 of this paper.     

Safety studies on high-pressure hydrogen vehicle refuelling stations: Releases into a simulated high-pressure dispensing area

If the general public is to use hydrogen as a vehicle fuel, customers must be able to handle hydrogen with the same degree of confidence, and with comparable risk, as conventional liquid and gaseous fuels. The hazards associated with jet releases from leaks in a vehicle-refuelling environment must be considered if hydrogen is stored and used as a high-pressure gas since a jet release in a confined or congested area can create an explosion hazard. As there was insufficient knowledge of the explosion hazards, a study was initiated to gain a better understanding of the potential explosion hazard consequences associated with high-pressure leaks from hydrogen vehicle refuelling systems. This paper describes the experiments with a dummy vehicle and dispenser units to represent refuelling station congestion. Experiments with ignition of premixed 5.4 m × 6.0 m × 2.5 m hydrogen–air clouds and hydrogen jet releases up to 40 MPa (400 bar) pressure are described. The results are discussed in terms of the conditions leading to the greatest overpressures and overall conclusions are made from these.     

Integration of a light mobility urban scale hydrogen refuelling station for cycling purposes in the transportation market

Road transportation consists of a significant contributor to total greenhouse gas emissions in developed countries. New alternative technologies in transportation such as electric vehicles aim to reduce substantially vehicle emissions, particularly in urban areas. Incentives of using two-wheel electric vehicles such as bicycles in big cities centres are promoted by local governments, and in fact, some countries are already trying to adopt this transition. An interesting case consists of the use of hydrogen fuel cells in such vehicles to increase their driving range under short refuelling times. To this end, this paper investigated the social and financial prospects of hydrogen infrastructure for city-oriented fuel cell electric vehicles such as bicycles. The results of the research indicated that a light mobility urban hydrogen refuelling station able to provide refuelling processes at pressures of 30 bar with a hydrogen fuel cost of 34.7 €/kgH₂ is more favourable compared to larger stations.     

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.     

Operating characteristics of a LH2-fuelled automotive vehicle and of a semi-automatic LH2-refuelling station

Based on earlier papers, new test results and experiences are reported about the refuelling of LH₂ automobile tanks by means of a semi-automatic refuelling station described in an earlier paper. This refuelling unit, designed and constructed only for the purpose of demonstration of liquid hydrogen handling by untrained people, has now been tested for refuelling of a LH₂-car. A specially designed LH₃-tank was mounted on the car as described earlier. The engine was converted for hydrogen fuel, but a switchback to gasoline fuel is possible by means of a very simple manipulation. The vehicle and the refuelling station were tested successfully and are now in continuous operation to demonstrate safe handling of LH₂-fuel. The experiences encountered are encouraging and enable suggestions and recommendations for the design and construction of safe LH₂-fuelled cars.     

Techno-economic analysis of PSA separation for hydrogen/natural gas mixtures at hydrogen refuelling stations

Logistics of hydrogen is one of the bottlenecks of a hydrogen economy. In this study, a pressure swing adsorption (PSA) system is proposed for the separation of hydrogen from natural gas, co-transported in the natural gas grid. The economic feasibility of hydrogen supplied by a PSA system at a refuelling station is assessed and compared with other alternatives. The adsorbent material is key to the design of a PSA system, which determines the operation performance and cost. It is concluded that a refuelling station with hydrogen supplied by a PSA system is economically feasible. The final hydrogen price including hydrogen supply, compression, storage, and dispensing is compared with two other hydrogen supply methods: on-site electrolysis and tube-trailer transported hydrogen. Currently, PSA supplied hydrogen is a more economical option. On-site electrolysis can become a more economical option in the future with improved cell efficiencies and reduced electricity prices. Tube-trailer transported hydrogen is highly influenced by the distance travelled. The findings of this study will help with more efficient distribution of hydrogen.     

Multi-objective optimization of cascade storage system in hydrogen refuelling station for minimum cooling energy and maximum state of charge

Compared with single-stage hydrogen storage refuelling, cascade storage refuelling has more advantages and significantly reduces cooling energy consumption. In the cascade system, the parameters of cascade storage tanks are critical, especially the initial pressure and volume. This article analyzes the thermodynamic processes in a cascade hydrogen refuelling station (HRS) and establishes the simulation model in Matlab/Simulink platform. The state of charge (SOC) of the onboard storage tank and the cooling energy consumption of the refuelling system are obtained from different initial pressures and volumes of the cascade storage tanks by using the simulation model. These data are introduced into the artificial neural networks in Matlab to generate a relationship between the decision variables and objective functions. The decision variables are optimized to minimize the cooling energy consumption and maximize the SOC through the genetic algorithm and Pareto optimization. So that optimal initial pressure and volume of the cascade storage tanks are determined. The research shows that when the ambient temperature is 293.15 K, and the SOC is 0.98–0.99, using the optimal initial pressure and volume of the cascade storage tanks can reduce the cooling energy consumption by up to 11.43%, compared with the baseline situation. Among the factors affecting cooling energy consumption and SOC, initial pressure is more sensitive than volume, so optimizing initial pressure, especially for the high-pressure cascade storage tank, seems more meaningful than volume. This research is instructive for the construction of the cascade HRS.     

Thermal management of hydrogen refuelling station housing on an annual level

A housing insulation of hydrogen refuelling station is vital from the aspect of safe operation of equipment in an environment that is installed. To secure hydrogen supply during the whole year, this work brings the solution for both cooling and heating insulation equipment inside of hydrogen refuelling station installed in Croatia, Europe. This hydrogen refuelling station was designed as an autonomous photovoltaic-hydrogen system. In the interest of improving its energy efficiency, an optimal thermal management strategy was proposed. To select the best technological solution for thermal management design which will maintain optimal temperature range inside the housing in cold and warm months, a detailed analysis of the system components thermodynamic parameters was performed. Optimal operating temperatures were established to be 25 °C in summer and 16 °C in winter, considering components working specifications. Insulation, type of cooling units, and heaters have been selected according to the HRN EN 12831 and VDI 2078 standards, while the regime of the heating and cooling system has been selected based on the station's indoor air temperature. The annual required heating and cooling energy were calculated according to HRN EN ISO 13790 standard, amounting to 1135.55 kW h and 1219.55 kW h, respectively. Annual energy share obtained from solar power plant used for the heating and cooling system resulted in 5%. The calculated thermal management system load turned out to be 1.437 kW.     

Techno-economic assessment of green hydrogen valley providing multiple end-users

A techno-economic analysis of a hydrogen valley is carried out in this paper. A hydrogen generator fed by a wind farm (WF) and/or a photovoltaic (PV) plant supplies four end-users: a stationary fuel cell, a hydrogen refuelling station, the injection in the natural gas pipeline and, in case of sufficient hydrogen surplus, a biological hydrogen methanation (BHM) process.The results demonstrated that an efficiency improvement and a reduction in hydrogen production costs arise from a balanced supply from wind and solar energy. Without the inclusion of a BHM process, hydrogen production costs lower than 7 €/kg were achieved by a hydrogen generator using 10–12% of the PV + WF annual energy with a PV share of 20%–50%. The hydrogen production costs were further reduced to 5 €/kg by introducing a BHM process and increasing the percentage of electrical energy supplied by the PV + WF system to 25% of its overall production.     

Analysis of operator human errors in hydrogen refuelling stations: Comparison between human rate assessment techniques

The use of hydrogen as an energy carrier for road transport appears to be an optimal solution for the reduction of greenhouse gas emissions. Nevertheless, the development of this technology depends on the growth and diffusion of production, storage and refuelling infrastructures together with accurate risk analyses to appropriately design the safety and management systems used in these plants. Moreover, to improve safety standards, it is also important to focus attention on the estimation of hazards related to human factors, as this is one of the major causes leading to accidental events, especially in complex industrial technology. The paper reports a case study relevant to operator errors that occur during maintenance procedures on safety venting devices in refuelling station hydrogen storage systems performed using first- and second-generation Human Rate Assessment (HRA) techniques. HEART (Human Error Assessment and Reduction Technique) methodology, a first-generation HRA method, which was modified on the basis of the fuzzy set concept, was employed to evaluate the probability of erroneous actions. The obtained results have been compared with results obtained using CREAM (second-generation) methodology. The critical analyses of the obtained results have also allowed to provide procedural recommendations and suggestions regarding safety equipment and procedures which can be adopted to reduce the risk of accidents.