Renewable electrolytic hydrogen potential in Algeria

The present paper deals with the assessment of the renewable hydrogen production potential in Algeria. The studied system produces hydrogen by electrolysis of water; electricity is supplied by a photovoltaic generator. Adequate mathematical models were used to calculate the electrolytic hydrogen production. Detailed hourly simulations were used to assess the potential for the entire country and to draw it maps. Throughout this study, the influence of the tilt angle of a photovoltaic generator has been investigated. It has been observed that the tilt angle has an impact on solar energy received by the photovoltaic generator, the produced solar electrical power and the rate of hydrogen production. We have calculated the optimal angles to maximize each element. We were particularly interested in the optimal angle to maximize hydrogen production. We found that the solar hydrogen potential for Algeria varies from 0.10 Nm³/m²/d to 0.14 Nm³/m²/d. This potential is quite significant, especially in the arid region of southeastern Algeria. The lowest potential is located in the northeast region. For stand-alone systems, it is important to assess the minimum available level, as their sizing takes into account the most unfavorable case. This level is between 0.07 Nm³/m²/d and 0.13 Nm³/m²/d. This shows that, even for a stand-alone system, the potential is quite high. Finally, we provide robust correlations that allow calculating the potential and the angle of inclination maximizing it for the whole of Algeria.     

Analytical model as a tool for the sizing of a hydrogen production system based on renewable energy: The Mexican Caribbean as a case of study

The main advantage of the hybrid system compared with separate array solar photovoltaic and stand-alone wind turbine is the possibility of the surplus energy storage by transforming it to hydrogen that can be use in fuel cells. However the design and sizing of this kind of technologies need to meet the local microclimate in order to reach higher efficacies. A tool based on an analytical model to sizing, analyze and assess the feasibility of the hybrid wind/photovoltaic/H₂ energy conversion systems using real weather data is presented in this work. The model considers an energy balance analysis and electrical variables of the system components; the tool calculates the subsystems efficacy and proposes the improvements to increase the efficiency of the use in surplus energy produced by the hybrid system. To validate the analytical model, simulation based on wind speed and solar radiation measurements from meteorological monitoring station in a Mexican Caribbean City is discussed.     

Analytical model for predicting the performance of photovoltaic array coupled with a wind turbine in a stand-alone renewable energy system based on hydrogen

We present the results of an analysis of the performance of a photovoltaic array that complement the power output of a wind turbine generator in a stand-alone renewable energy system based on hydrogen production for long-term energy storage. The procedure for estimating hourly solar radiation, for a clear sunny day, from the daily average solar insolation is also given. The photovoltaic array power output and its effective contribution to the load as well as to the energy storage have been determined by using the solar radiation usability concept. The excess and deficit of electrical energy produced from the renewable energy sources, with respect to the load, govern the effective energy management of the system and dictate the operation of an electrolyser and a fuel cell generator. This performance analysis is necessary to determine the effective contribution from the photovoltaic array and the wind turbine generator and their contribution to the load as well as for energy storage.     

Optimization of the photovoltaic-hydrogen supply system of a stand-alone remote-telecom application

Hydrogen is considered as the optimal carrier for the surplus energy storage from renewable resources. Although hydrogen and its application in fuel cell is considered as a high-cost energy system, some cost-efficient solutions have been found for their use in stand-alone applications, which usually depend on the variability of renewable sources that have to be oversized in order to reduce their dependence on external energy sources. This paper shows the results from the simulation of several alternatives of introducing hydrogen technologies to increase the independence of a remote-telecom application fed by photovoltaic panels. Hydrogen is obtained by electrolysis and it is used in a fuel cell when the renewable energy source is not enough to maintain the stand-alone application. TRNSYS simulation environment has been used for evaluating the proposed alternatives. The results show that the best configuration option is that considering the use of hydrogen as a way to storage the surplus of radiation and the management system can vary the number of photovoltaic panels assigned to feed the hydrogen generation, the batteries or the telecom application.     

Dynamic modeling of a photovoltaic hydrogen fuel cell hybrid system

The objective of this paper is to mathematically model a stand-alone renewable power system, referred to as “Photovoltaic–Fuel Cell (PVFC) hybrid system”, which maximizes the use of a renewable energy source. It comprises a photovoltaic generator (PV), a water electrolyzer, a hydrogen tank, and a proton exchange membrane (PEM) fuel cell generator. A multi-domain simulation platform Simplorer is employed to model the PVFC hybrid systems. Electrical power from the PV generator meets the user loads when there is sufficient solar radiation. The excess power from the PV generator is then used for water electrolysis to produce hydrogen. The fuel cell generator works as a backup generator to supplement the load demands when the PV energy is deficient during a period of low solar radiation, which keeps the system's reliability at the same level as for the conventional system. Case studies using the present model have shown that the present hybrid system has successfully tracked the daily power consumption in a typical family. It also verifies the effectiveness of the proposed management approach for operation of a stand-alone hybrid system, which is essential for determining a control strategy to ensure efficient and reliable operation of each part of the hybrid system. The present model scheme can be helpful in the design and performance analysis of a complex hybrid-power system prior to practical realization.     

Design and set up of a hybrid power system (PV-WT-URFC) for a stand-alone application in Mexico

The Mexican territory has a large potential for renewable energy development, such as geothermal, hydro, biofuels, wind and solar. Thus, a 2.5 kW hybrid power system (solar, wind and hydrogen) was designed and installed to meet the power demand for a stand-alone application at the University of Zacatecas. The hybrid unit integrates three power energy sources –a photovoltaic system (PV), a micro-wind turbine (WT), a prototype of a unitized regenerative fuel cell (URFC) and energy storage devices (batteries)– in addition to their interaction methodology. The main contribution of this work is the URFC integration to a hybrid power system for the production of H₂ (water electrolyzer mode) and energy (fuel cell mode). These three energy technologies were connected in parallel, synchronized to the energy storage system and finally coupled to a power conversion module. To achieve the best performance and energy management, an energy management and control strategy was developed to the properly operation of the power plant. A meteorological station that has wireless sensors for the temperature, the humidity, the solar radiation and the wind speed provides the necessary information (in real time) to the monitor and control software, which computes and executes the short and mid–term decisions about the energy management and the data storage for future analysis.     

Model for energy conversion in renewable energy system with hydrogen storage

A dynamic model for a stand-alone renewable energy system with hydrogen storage (RESHS) is developed. In this system, surplus energy available from a photovoltaic array and a wind turbine generator is stored in the form of hydrogen, produced via an electrolyzer. When the energy production from the wind turbine and the photovoltaic array is not enough to meet the load demand, the stored hydrogen can then be converted by a fuel cell to produce electricity. In this system, batteries are used as energy buffers or for short time storage. To study the behavior of such a system, a complete model is developed by integrating individual sub-models of the fuel cell, the electrolyzer, the power conditioning units, the hydrogen storage system, and the batteries (used as an energy buffer). The sub-models are valid for transient and steady state analysis as a function of voltage, current, and temperature. A comparison between experimental measurements and simulation results is given. The model is useful for building effective algorithms for the management, control and optimization of stand-alone RESHSs.     

Model-based optimal control of a hybrid power generation system consisting of photovoltaic arrays and fuel cells

Hybrid renewable energy systems are expected to become competitive to conventional power generation systems in the near future and, thus, optimization of their operation is of particular interest. In this work, a hybrid power generation system is studied consisting of the following main components: photovoltaic array (PV), electrolyser, metal hydride tanks, and proton exchange membrane fuel cells (PEMFC). The key advantage of the hybrid system compared to stand-alone photovoltaic systems is that it can store efficiently solar energy by transforming it to hydrogen, which is the fuel supplied to the fuel cell. However, decision making regarding the operation of this system is a rather complicated task. A complete framework is proposed for managing such systems that is based on a rolling time horizon philosophy.     

Dynamic modeling and sizing optimization of stand-alone photovoltaic power systems using hybrid energy storage technology

Economic and environmental concerns over fossil fuels encourage the development of photovoltaic (PV) energy systems. Due to the intermittent nature of solar energy, energy storage is needed in a stand-alone PV system for the purpose of ensuring continuous power flow. Three stand-alone photovoltaic power systems using different energy storage technologies are studied in this paper. Key components including PV modules, fuel cells, electrolyzers, compressors, hydrogen tanks and batteries are modeled in a clear way so as to facilitate the evaluation of the power systems. Based on energy storage technology, a method of ascertaining minimal system configuration is designed to perform the sizing optimization and reveal the correlations between the system cost and the system efficiency. The three hybrid power systems, i.e., photovoltaic/battery (PV/Battery) system, photovoltaic/fuel cell (PV/FC) system, and photovoltaic/fuel cell/battery (PV/FC/Battery) system, are optimized, analyzed and compared. The obtained results indicate that maximizing the system efficiency while minimizing system cost is a multi-objective optimization problem. As a trade-off solution to the problem, the proposed PV/FC/Battery hybrid system is found to be the configuration with lower cost, higher efficiency and less PV modules as compared with either single storage system.     

Sizing optimization,dynamic modeling and energy management strategies of a stand-alone PV/hydrogen/battery-based hybrid system

This paper presents a sizing method and different control strategies for the suitable energy management of a stand-alone hybrid system based on photovoltaic (PV) solar panels, hydrogen subsystem and battery. The battery and hydrogen subsystem, which is composed of fuel cell (FC), electrolyzer and hydrogen storage tank, act as energy storage and support system. In order to efficiently utilize the energy sources integrated in the hybrid system, an appropriate sizing is necessary. In this paper, a new sizing method based on Simulink Design Optimization (SDO) of MATLAB was used to perform a technical optimization of the hybrid system components. An analysis cost has been also performed, in that the configuration under study has been compared with those integrating only batteries and only hydrogen system. The dynamic model of the designed hybrid system is detailed in this paper. The models, implemented in MATLAB-Simulink environment, have been designed from commercially available components. Three control strategies based on operating modes and combining technical-economic aspects are considered for the energy management of the hybrid system. They have been designed, primarily, to satisfy the load power demand and, secondarily, to maintain a certain level at the hydrogen tank (hydrogen energy reserve), and at the state of charge (SOC) of the battery bank to extend its life, taking into account also technical-economic analysis. Dynamic simulations were performed to evaluate the configuration, sizing and control strategies for the energy management of the hybrid system under study in this work. Simulation results show that the proposed hybrid system with the presented controls is able to provide the energy demanded by the loads, while maintaining a certain energy reserve in the storage sources.     

Optimal sizing of stand-alone hybrid systems based on PV/WT/FC by using several methodologies

This paper presents a comparative study of four sizing methods for a stand-alone hybrid generation system integrating renewable energies (photovoltaic panels and wind turbine) and backup and storage system based on battery and hydrogen (fuel cell, electrolyzer and hydrogen storage tank). Two of them perform a technical sizing. In one case, the sizing is based on basic equations, and in the other case, an optimal technical sizing is achieved by using Simulink Design Optimization. The other two methods perform an optimal techno-economical sizing by using the hybrid system optimization software HOMER and HOGA, respectively. These methods have been applied to design a stand-alone hybrid system which supplies the load energy demand during a year. A MATLAB-Simulink model of the hybrid system has been used to simulate the performance of hybrid system designed by each method for the stand-alone application under study in this work. The results are reported and discussed in the paper.     

Optimal sizing of photovoltaic systems based green hydrogen refueling stations case study Oman

Green hydrogen reduces carbon dioxide emission, advances the dependency on fossil fuels and improves the economy of the energy sector, especially in developing countries. Hydrogen is required for the green transportation sector and many other industrial applications. However, the high cost of green hydrogen production reduces the fast development of renewable energy projects based on hydrogen production. So, sizing by optimization is required to determine the optimum solutions for green hydrogen production. In this context, this paper aims to analyze three methods that can be developed and implemented for the production of green hydrogen for refueling stations using photovoltaic (PV) systems. Techno-economic models are adopted to calculate the Levelized Hydrogen Cost (LHC) for the PV grid-connected system, stand-alone PV system with batteries, and stand-alone PV system with fuel cells. The photovoltaic systems based green hydrogen refueling stations are optimized using Homer software. The optimization results of the Net Profit Cost (NPC), and the LHC permit the comparison of the three cases and the selection of the optimal solution. The analysis has shown that a 3 MWp grid-connected PV system represents a promising green hydrogen production at an LHC of 5.5 €/kg. The system produces 58 615 kg of green hydrogen per year reducing carbon dioxide emission by 8209 kg per year. The LHC in the stand-alone PV system with batteries, and stand-alone PV system with fuel cells are 5.74 €/kg and 7.38 €/kg, respectively.     

Domestic hydrogen production using renewable energy

A brief review shows that domestic production of hydrogen to fuel a car is feasible by using various means. Among these, the solar––photovoltaic electricity––electrolysis process seems to be the most practical if a renewable energy source is to be used. A simplified model has been developed to determine and optimize the thermal and economical performance of domestic photovoltaic-electrolyzer systems, either with fixed or sun tracking panels using annual total solar radiation on a horizontal surface and climatic data. Twelve locations in the United Sates from four climatic zones (tropical-sub tropical, dry, temperate, cool snow-forest) have been selected. Simulations have been carried out to produce data for hydrogen production for these various locations and the resulting data have been correlated to obtain hydrogen production in kg/kW_p/year photovoltaic system as a function of total annual solar radiation on horizontal surface. The economical feasibility has been studied by taking the photovoltaic and electrolyzer systems' price as variable parameters. It is assumed that the necessary capital is 100% borrowed from a financial institution to pay back in monthly installments. It has been found that the hydrogen production with fixed photovoltaic panels varies from 26 to 42 kg/kW_p/year and the cost from 25 to 268 $/GJ.     

An integrated system of zinc oxide solar panels,fuel cells,and hydrogen storage for heating and cooling applications

Due to the production of hydrogen, using fuel cells for energy conversion and storing encounters safety problems. Combining high-temperature solid oxide fuel cells with photovoltaic solar panels or zinc oxide solar panels can be a good candidate to produce/convert and store the energy more efficiently for using at peak times. The current paper intends to analyze the efficiency of integration of zinc oxide solar panels and fuel cells to produce hydrogen directly. Therefore, the excess step of converting electricity to hydrogen and re-converting it to electricity, which is customarily used for the integration of the photovoltaic and solid oxide fuel cells, could be skipped. The new method paves the way for providing the required energy for heating/cooling through the floor heating and ceiling cooling systems as well as generating electricity. The article also demonstrates that it is possible to have heat during the day and night for an area of 1920 m² and 542 m². It is also possible to create coolness during the day and night for an area of 925 m² and 260 m².     

Data results and operational experience with a solar hydrogen system

A solar hydrogen system is presented able to provide uninterrupted 200 W_e power to an isolated application. It is composed of a photovoltaic generator, a battery set, an electrolyser, a metal-hydride system for hydrogen storage and a fuel cell. Batteries are charged with the photovoltaic array and the fuel cell, and discharged with the electrolyser and the application load. The fuel cell switches on when the state of charge of the batteries is low, until they are recovered to a predetermined level. The electrolyser produces H₂ at 30 bar, enough to feed directly the metal hydrides, avoiding pressurization steps. Metal hydrides work under pressure control in the temperature range 0–40 °C. Kinetics of absorption–desorption of hydrogen is observed as an important limiting aspect for this kind of storage. The system is able to convert about 6–7% of total solar energy irradiated in 1 year. Results and evaluation after 1-year operation are shown. Energy management is found to be a critical issue to improve the behavior of the system.     

Design and analysis of stand-alone hydrogen energy systems with different renewable sources

One of the most interesting developments of energy systems based on the utilization of hydrogen is their integration with renewable sources of energy (RES). In fact, hydrogen can operate as a storage and carrying medium of these primary sources. The design and operation of the system could change noticeably, depending on the type and availability of the primary source. In this paper, the results obtained considering a model of a stand-alone energy system supplied just with RES and composed by an electrolyzer, a hydrogen tank and a proton exchange membrane fuel cell are exposed. The energy systems have been designed in order to supply the electricity needs of a residential user in a mountain environment in Italy during a complete year. Three different sources have been considered: solar irradiance (transformed by an array of photovoltaic modules), hydraulic energy (transformed by a micro-hydro turbine in open-flume configuration) and wind speed (transformed by a small-size wind generator). It has been checked that, in that specific location, it is absolutely not convenient to use the wind source; the solar irradiance has a nearly constant availability during the year, and therefore the seasonal storage of the RES in form of hydrogen is the lowest; the availability of the micro-hydro source is less constant than in case of solar irradiance, requiring a higher hydrogen seasonal storage, but its advantage is linked to the higher efficiency of the turbine and the fact that the RES is directly sent to the user with high frequency (for these reasons it is the best plant option).     

The benefits of the transition from fossil fuel to solar energy in Libya: A street lighting system case study

The Libyan economy is dominated by the oil and the gas industry which are considered as the primary energy sources for the generating power plants. With the increased energy demands in the near future, Libya will be forced to burn more oil and gas. This, in turn will result in reducing the country revenue, threatening the economy and increasing the CO₂ emission. This triggers the alarm for Libya to an urgent plan to diversify the energy sources through using sustainable energy. The sun showers Libya every day by a huge amount of sunshine, especially during the peaks in the summer days. Recently, the country has been struggling to satisfy its escalating energy demands. The residential and street lighting loads constitute more than 50% of the electricity demands in Libya. Street lighting consumes more than 3.996 TW h, which is around one fifth of the energy demands in Libya. Energy conservation and transition from fossil fuel to renewable energy could have significant profit on the energy sector in Libya. For example, Libya is still relying on the old-fashioned, inefficient and unsustainable street lighting systems. Replacing the old technology lighting systems with up-to-date solar powered lighting system can achieve energy saving and sustainability. In this paper, improving the energy situation in Libya through replacing the high pressure sodium street lighting systems with solar powered LED street lighting systems is investigated. A four km road is chosen as a case study. Four alternatives are analyzed; grid-powered high pressure sodium lamp street lighting system, grid-powered LED lamp street lighting system, stand-alone solar powered LED street lighting system and grid-connected solar powered LED street lighting system. The four options are compared in terms of the capital cost, maintenance cost, total cost, fuel cost and the CO₂ emission. Replacing the high pressure sodium lamp system with LED lamp system saves 75% of energy and reduces the CO₂ emission by 75%. The stand-alone solar powered LED lighting system cuts the CO₂ emission, saves the fuel and is economically feasible. Furthermore, improvement is attained if the solar powered lighting system is connected to the grid where the excess energy is fed to the grid. The two solar powered options are economically feasible and sustainable.     

Monitoring and control of a hydrogen production and storage system consisting of water electrolysis and metal hydrides

Renewable energy sources such as wind turbines and solar photovoltaic are energy sources that cannot generate continuous electric power. The seasonal storage of solar or wind energy in the form of hydrogen can provide the basis for a completely renewable energy system. In this way, water electrolysis is a convenient method for converting electrical energy into a chemical form. The power required for hydrogen generation can be supplied through a photovoltaic array. Hydrogen can be stored as metal hydrides and can be converted back into electricity using a fuel cell. The elements of these systems, i.e. the photovoltaic array, electrolyzer, fuel cell and hydrogen storage system in the form of metal hydrides, need a control and monitoring system for optimal operation. This work has been performed within a Research and Development contract on Hydrogen Production granted by Solar Iniciativas Tecnológicas, S.L. (SITEC), to the Politechnic University of Valencia and to the AIJU, and deals with the development of a system to control and monitor the operation parameters of an electrolyzer and a metal hydride storage system that allow to get a continuous production of hydrogen.     

Design and assessment of a solar energy based integrated system with hydrogen production and storage for sustainable buildings

The current study investigates a holistically developed solar energy system combined with a ground-sourced heat pump system for stand-alone usage to produce power, heat, and cooling along with domestic hot water for residential buildings. An integrated system is proposed where three types of building-integrated photovoltaic plant orientation are considered and integrated with a vertical-oriented ground-sourced heat pump system as well as an anion exchange membrane electrolyser for hydrogen-based energy storage along with proton exchange membrane fuel cells. The ground-sourced heat pump system covers the heating requirements and exploits the available thermal energy under the ground. Hydrogen subsystem enables the integrated system to be used anytime by compensating the peak periods with stored hydrogen via fuel cell and exploiting the excess energy to produce hydrogen via electrolyser. The photovoltaic plant orientations are extensively designed by considering geometries of three different applications, namely, rooftop photovoltaic, building-integrated photovoltaic façade and photovoltaic canopy. The shading and geometrical losses of photovoltaic applications are extensively identified and considered. In addition, the openly available high-rise building load profiles are obtained from the OpenEI network and are modified accordingly to utilize in the current study. The building requirements are considered for 8760 h annually with meteorological data and energy usage characteristics of the selected regions. The integrated system is assessed via thermodynamic-based approach from energy and exergy points of views. In order to increase generality, the proposed building energy system is analyzed for five different cities around the globe. The obtained results show that a 20-floor building with approximately 62,680 m² residential area needs between 550 kWp and 1550 kWp of a photovoltaic plant in five different cities. For Ottawa, Canada, the overall energy and exergy efficiencies are found as 18.76% and 10.49%, respectively, in a typical meteorological year. For the city of Istanbul in Turkey, a 20-floor building is found to be self-sufficient by only using the building's surface area with a 495 kWp BIPV façade and a 90 kWp rooftop PV.     

Optimisation of solar-hydrogen power system for household applications

A numerical method was developed for optimising solar–hydrogen energy system to supply renewable energy for typical household connected with the grid. The considered case study involved household located in Diyala Governorate, Iraq. The solar–hydrogen energy system was designed to meet the desired electrical load and increase the renewable energy fraction using optimum fuel cell capacity. The simulation process was conducted by MATLAB based on the experimental data for electrical load, solar radiation and ambient temperature at a 1-min time-step resolution. Results demonstrated that the optimum fuel cell capacity was approximately 2.25 kW at 1.8 kW photovoltaic power system based on the average of the daily energy consumption of 6.8 kWh. The yearly renewable energy fraction increased from 31.82% to 95.82% due to the integration of the photovoltaic system with a 2.25 kW fuel cell used as a robust energy storage unit. In addition, the energy supply, which is the economic aspect for the optimum system, levelised electricity cost by approximately $0.195/kWh. The obtained results showed that the proposed numerical analysis methodology offers a distinctive property that can be used effectively to optimise hybrid renewable energy systems.