Sustainable energy planning based on a stand-alone hybrid renewableenergy/hydrogen power system: Application in Karpathos island, Greece

This study presents the sustainable planning of a renewables-based energy system, which aims to fulfil the electric needs of the island by replacing the existing diesel generators with new wind farms, photovoltaic installations and hydrogen production systems. Electric system design and least cost planning analysis were concluded using historic data from both demand and supply sides. An optimal “sustainable island” scheme should ensure 100% use of renewable energy resources for power generation, while hydrogen production is ideal for covering storage and transportation needs. Due to its morphology and scale, Karpathos applies perfectly for wind and solar energy systems, due to increased solar resource (about 1790 kWh/m².year of global irradiation) and high wind potential (average of 9 m/s in specific locations). Therefore, this case study examines an increase in RES penetration up to 20% in the electric energy mixture, a hydrogen production plan just for the needs of transport and a more aggressive, 100% renewables scheme that ensures a self-fulfilling energy system based on indigenous renewable resources.     

Experimental characterization of a grid-connected hydrogen energy buffer: Hydrogen production

Energy storage becomes a necessity when a high penetration of renewable energy sources is desirable. Variability in the energy production from these types of energy sources can make the utility grid unstable, if the percentage of production is important. In order to minimize this problem, the HiDRENER project was designed to study the effect of combining different renewable energy sources with energy storage on grid stability. The system has a wind generator, a gasifying biomass power plant with syngas storage, a solar photovoltaic plant, and a hydrogen energy buffer. Controlling the entire system is very complex. This paper shows the results of the grid-connected hydrogen energy buffer characterization, considering hydrogen production in this first stage. The objective is to know the complete behavior of the system, which could help us to define the energy buffer control. This control is oriented toward consuming excess energy produced by the other sources in real time. This means that the hydrogen buffer control has to negotiate how much energy can be stored, and act on the production system. Thus, actuation variables and dynamic behavior have to be discovered.     

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).     

An optimization model for regional renewable energy development

This research effort details the modeling component of a comprehensive decision support system for energy planning that allows for combining existing electricity generating capabilities with increased use of renewable energy sources. It focuses on energy planning at the regional level, and it is illustrated by applying it to the greater southern Appalachian mountains of the eastern United States: a region that was chosen for analysis not only due to its heavy dependence on coal for electricity, but also because of its potential for increased use of wind and solar power. The paper specifically discusses the development of a multi-objective linear programming (MOLP) model that can be used to determine the optimal mix of renewable energy sources and existing fossil fuel facilities on a regional basis. This model allows a decision maker to balance annual generation costs against the corresponding greenhouse gas emissions, and it provides significant support for implementing a variety of different policy analyses.     

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.     

Assessment of solar and wind energy as motive for potential hydrogen production of Algeria country; development a methodology for uses hydrogen-based fuel cells

This study is based on method of storing the part of renewable energy in the hydrogen form for using in a fuel cell at the absence of solar radiation due to overcast day or in the night. In addition, the system advantage don't need a batteries compared with other systems. The present work is compared energy potential of the wind and solar with the results of hydrogen production and to address the various obstacles to study and evaluation. This work is assessment the renewable resources in various sites of Algeria, especially in Adrar area which is one regions of the high solar energy in the world, where the radiation rates exceed more than $2300kWh/m^2$ per year, the area is also characterized by high wind power. In fact, by these two energy sources (solar and wind) that it characterized by Adrar, it's interesting to combine electrical producing energy and hydrogen production. The studies indicate that there are the meteorological factors related to the nature of site (irradiation, temperature and wind speed) are linked to the generation of electricity by renewable energy. The results obtained showing that the hydrogen production related to the solar radiation values, where southern of Algeria has more hydrogen potential compared with the northern. The simulation results show that the energy supplied by a photovoltaic module type UDTS 50 can supply energy for ten electrolyzer cells which are connected in series with this module.     

Analysis of hydrogen production from combined photovoltaics, wind energy and secondary hydroelectricity supply in Brazil

In this work, the technical and economical feasibility for implementing a hypothetical electrolytic hydrogen production plant, powered by electrical energy generated by alternative renewable power sources, wind and solar, and conventional hydroelectricity, was studied mainly trough the analysis of the wind and solar energy potentials for the northeast of Brazil. The hydrogen produced would be exported to countries which do not presently have significant renewable energy sources, but are willing to introduce those sources in their energy system. Hydrogen production was evaluated to be around 56.26 × 10⁶ m³ H₂/yr at a cost of 10.3 US$/kg.     

The role of public policy in optimizing renewable energy development in the greater southern Appalachian mountains

This research presents a third component of a comprehensive decision support system for energy planning that allows for combining existing electricity generating capabilities with increased use of renewable energy sources. It focuses on energy planning at the regional level, and concentrates specifically on the greater southern Appalachian mountains of the eastern United States: a region that was chosen for analysis not only due to its heavy dependence on coal for electricity, but also because of its potential for increased use of wind and solar power. Previous research used a geographic information system (GIS) model for identifying renewable energy potential to provide input data for a multi-objective linear programming (MOLP) model to determine the optimal constrained mix of renewable energy sources and existing fossil fuel facilities by balancing annual generation costs against the corresponding greenhouse gas emissions. This new component of the system analyzes three potential public policies—renewable portfolio standard, carbon tax, and renewable energy production tax credit—that have been used to foster increased renewable energy usage. These policies require minor modifications to the MOLP model for implementation. The results of these policy cases were then analyzed to determine the impact that these policies have on generation cost and pollution emissions within the region.     

Levelized costs of energy and hydrogen of wind farms and concentrated photovoltaic thermal systems. A case study in Morocco

This work deals with the evaluation of levelized costs of energy and hydrogen of wind farms and concentrated photovoltaic thermal systems. The production of hydrogen is ensured by an alkaline water electrolyser supplied by the electric current generated by the renewable energy sources. The study is carried out on the basis of meteorological data from the Tangier region, in Morocco. Mathematical models are developed to assess the performance and efficiency of renewable sources in terms of energy and hydrogen production for different installed powers. The comparison between the current results and those of previous work shows that the discrepancy did not exceed 6% for both electrical and thermal efficiency of the concentrated photovoltaic/thermal system. The results show that the energy consumption ratios of the electrolyzer are 61 and 64 kWh.kg⁻¹ for wind and solar energy, respectively. Wind and solar hydrogen production efficiencies are also 66 and 62%, respectively. Results show that levelized costs of energy and hydrogen decrease with the increase in installed wind and photovoltaic capacity. The overall results also show that the Tangier region can produce energy and hydrogen at low cost using wind energy compared to concentrated photovoltaic installations. For the hybridization of the two green sources studied, this is highly recommended provided that the capacity of the electrolyzer to be installed is optimal in order to effectively improve the production of hydrogen.     

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.     

PSCAD/EMTDC modeling and simulation of solar-powered hydrogen production system

This paper presents an effective modeling and simulation scheme of solar-powered hydrogen production system (PV-SPE: Photovoltaic-Solid Polymer Electrolyte). Hydrogen can provide clean, reliable, and affordable energy supply, which can enhance world's economy, environment and security. In the coming decades, the world will need new energy supplies and an upgraded energy infrastructure to meet the growing demands for electric power and transportation fuels.Existing production technologies can produce vast amounts of hydrogen from hydrocarbons; unfortunately, they emit large amounts of carbon dioxide (CO₂) into the atmosphere. Renewable technologies such as solar and wind need to be further developed in order for hydrogen production to be more cost-competitive than other sources.In this paper, we focused on a renewable technology that can advance the commercial readiness of the solar-powered hydrogen production system. Software (PSCAD/EMTDC) based model of PV-SPE system is used to effectively simulate a hydrogen production system. To verify the simulation results, we implemented an actual PV-SPE system. The actual values obtained from the data acquisition system were compared to the simulation results.     

Estimating global hydrogen production from wind

It is likely that intermittent renewable sources such as wind and solar will provide the greatest opportunity for future large-scale hydrogen production. Here, on-shore wind is examined. Global wind energy is estimated by placing one 2 MW turbine/km² over the surface of the earth. Wind energy production is based on monthly mean wind speed data. Wind turbines are grouped to form arrays that are linked to local hydrogen generation and transmission networks. Hydrogen generation is done via low-pressure electrolysis and transmission via high-pressure gas pipelines. The wind/hydrogen system is considered within a global energy system that must not only provide hydrogen, but also energy for electricity consumption at the local generation site. The technical potential of the hydrogen produced is estimated to be 116 EJ. Uneven distribution of the hydrogen-rich sites results in the need to export much of the hydrogen produced to energy-poor regions. To overcome system losses, a combined wind/HVDC/hydrogen system is considered.     

An analysis of hydrogen production from renewable electricity sources

Three aspects of producing hydrogen via renewable electricity sources are analyzed to determine the potential for solar and wind hydrogen production pathways: a renewable hydrogen resource assessment, a cost analysis of hydrogen production via electrolysis, and the annual energy requirements of producing hydrogen for refueling. The results indicate that ample resources exist to produce transportation fuel from wind and solar power. However, hydrogen prices are highly dependent on electricity prices. For renewables to produce hydrogen at $2 kg⁻¹, using electrolyzers available in 2004, electricity prices would have to be less than $0.01 kWh⁻¹. Additionally, energy requirements for hydrogen refueling stations are in excess of 20 GWh/year. It may be challenging for dedicated renewable systems at the filling station to meet such requirements. Therefore, while plentiful resources exist to provide clean electricity for the production of hydrogen for transportation fuel, challenges remain to identify optimum economic and technical configurations to provide renewable energy to distributed hydrogen refueling stations.     

Potential of renewable hydrogen production for energy supply in Hong Kong

Hong Kong is highly vulnerable to energy and economic security due to the heavy dependence on imported fossil fuels. The combustion of fossil fuels also causes serious environmental pollution. Therefore, it is important to explore the opportunities for clean renewable energy for long-term energy supply. Hong Kong has the potential to develop clean renewable hydrogen energy to improve the environmental performance. This paper reviews the recent development of hydrogen production technologies, followed by an overview of the renewable energy sources and a discussion about potential applications for renewable hydrogen production in Hong Kong. The results show that although renewable energy resources cannot entirely satisfy the energy demand in Hong Kong, solar energy, wind power, and biomass are available renewable sources for significant hydrogen production. A system consisting of wind turbines and photovoltaic (PV) panels coupled with electrolyzers is a promising design to produce hydrogen. Biomass, especially organic waste, offers an economical, environmental-friendly way for renewable hydrogen production. The achievable hydrogen energy output would be as much as 40% of the total energy consumption in transportation.     

H2RES,Energy planning tool for island energy systems – The case of the Island of Mljet

When it comes to the energy planning, computer programs like H₂RES are becoming valuable tools. H₂RES has been designed as support for simulation of different scenarios devised by RenewIsland methodology with specific purpose to increase integration of renewable sources and hydrogen into island energy systems. The model can use wind, solar, hydro, biomass, geothermal as renewable energy sources and fossil fuel blocks and grid connection with mainland as back up. The load in the model can be represented by hourly and deferrable electricity loads of the power system, by hourly heat load, by hydrogen load for transport and by water load depending on water consumption. The H₂RES model also has ability to integrate different storages into island energy system in order to increase the penetration of intermittent renewable energy sources or to achieve a 100% renewable island. Energy storages could vary from hydrogen loop (fuel cell, electrolyser and hydrogen storage) to reversible hydro or batteries for smaller energy systems. The H₂RES model was tested on the power system of the Island of Porto Santo – Madeira, the islands of Corvo, Graciosa, and Terrciera – Azores, Sal Island – Cape Verde, Portugal, the Island of Mljet, Croatia and on the energy system of the Malta. Beside energy planning of the islands, H₂RES model could be successfully applied for simulation of other energy systems like villages in mountain regions or for simulation of different individual energy producers or consumers.     

Experimental performance assessment of an online energy management strategy for varying renewable power production suppression

Lately, interest in renewable sources, especially wind and solar energy, has shown a significant increase in all over the world that mostly depends on climate-threatening conventional fossil fuels. Besides, hybrid use of these power sources with suitable back-up units provides many advantages compared to sole use of these sources. In this regard, a hybrid system consisting of a wind turbine for utilizing the wind energy, photovoltaic panels for solar energy, fuel cell for providing back-up power and a battery unit for storing the possible excess energy production and supplying the transient load is considered in this study. Experimental assessment of this system in different case studies including the real time measured dynamic power demand of an office block is realized. The collaborative actions of the proposed hybrid system with a fuzzy logic based energy management strategy during fluctuations of renewable-based power production are investigated. Thus, results of this study may be valuable for evaluating the feasibility of stand-alone hybrid renewable energy units for future power systems.     

A review on copper vanadate‐based nanostructures for photocatalysis energy production

The economic, social, and environmental aspects are important that should be notable before the selection of a method for the production of energy. Various renewable energy sources are used like hydropower, biomass, biofuel, geothermal energy, and wind energy for the production of sustainable energy that are excellent approaches to fulfill energy environmental energy demands. Renewable sources of energy give an excellent chance to extenuate the gas emission in greenhouse and reduction of global warming with the help of renewable sources of energy. The importance and utilization of the variety of renewable sources of energy are elaborated in this article. The emerging and exploring technique for the production of energy is the photocatalysis. In photocatalysis, solar spectrum is the extraneous source that is used with water to produce hydrogen energy (green energy) by the water splitting under the shower of the solar spectrum. The solar spectrum contains heat and intensity of light from which light spectrum is the abundantly used for the splitting of water. The photocatalyst is the key factor to initiate the reaction depending upon the energy band gap by absorbing the energy from the spectrum of the sun. Semiconducting materials having lower forbidden energy band gap are the basic requirements to use them as a photocatalyst for photocatalysis. Copper vanadate and their composites are the promising materials that are used as photocatalyst for the production of hydrogen energy. Copper vanadate is the focusing material that can be used as photocatalyst. It is an n‐type semiconducting material with 2 eV indirect energy band gap having monoclinic structural phase which is tuned by the doping of metals like chromium, molybdenum, and silver to reduce the grain size and energy band gap and increase the surface area and optical absorption of solar light only to enhance the photocatalytic performance towards the production of hydrogen energy by water splitting in the presence of solar light.     

Power management strategies for a stand-alone power system using renewable energy sources and hydrogen storage

A stand-alone power system based on a photovoltaic array and wind generators that stores the excessive energy from renewable energy sources (RES) in the form of hydrogen via water electrolysis for future use in a polymer electrolyte membrane (PEM) fuel cell is currently in operation at Neo Olvio of Xanthi, Greece. Efficient power management strategies (PMSs) for the system have been developed. The PMSs have been assessed on their capacity to meet the power load requirements through effective utilization of the electrolyzer and fuel cell under variable energy generation from RES (solar and wind). The evaluation of the PMS has been performed through simulated experiments with anticipated conditions over a typical four-month time period for the region of installation. The key decision factors for the PMSs are the level of the power provided by the RES and the state of charge (SOC) of the accumulator. Therefore, the operating policies for the hydrogen production via water electrolysis and the hydrogen consumption at the fuel cell depend on the excess or shortage of power from the RES and the level of SOC. A parametric sensitivity analysis investigates the influence of major operating variables for the PMSs such as the minimum SOC level and the operating characteristics of the electrolyzer and the fuel cell in the performance of the integrated system.     

Modelling and control of hydrogen and energy flows in a network of green hydrogen refuelling stations powered by mixed renewable energy systems

The planning of a hydrogen infrastructure with production facilities, distribution chains, and refuelling stations is a hard task. Difficulties may rise essentially in the choice of the optimal configurations. An innovative design of hydrogen network has been proposed in this paper. It consists of a network of green hydrogen refuelling stations (GHRSs) and several production nodes. The proposed model has been formulated as a mathematical programming, where the main decisions are the selection of GHRSs that are powered by the production nodes based on distance and population density criteria, as well the energy and hydrogen flows exchanged among the system components from the production nodes to the demand points. The approaches and methodologies developed can be taken as a support to decision makers, stakeholders and local authorities in the implementation of new hydrogen infrastructures. Optimal configurations have been reported taking into account the presence of an additional hydrogen industrial market demand and a connection with the electrical network. The main challenge that has been treated within the paper is the technical feasibility of the hydrogen supply chain, that is mainly driven by uncertain, but clean solar and wind energy resources. Using a Northern Italian case study, the clean hydrogen produced can be technically considered feasible to supply a network of hydrogen refuelling stations. Results show that the demands are satisfied for each time period and for the market penetration scenarios adopted.