PV–wind hybrid system performance: A new approach and a case study

Until now, there is no internationally accepted guideline for the measurement, data exchange and analysis of PV–Wind Hybrid Systems. As there is a need for such a tool, so as to overcome the barrier that the lack of confidence due to the absence of reliability means for the development of the market of Hybrid Systems, an effort has been made to suggest one tool for PV–Wind Hybrid Systems. The suggested guidelines presented in this work are based on the existing guidelines for PV Systems, as a PV–Wind Hybrid system can be roughly thought of as a PV System to which wind generation has been added. So, the guidelines for PV Systems are valid for the PV–Wind System, and only the part referred to wind generation should be included. This has been the process followed in this work. The proposed method is applied to a case study, the CICLOPS Project, a 5 kW PV, 7.5 kW Wind Hybrid system installed at the Isolated Wind Systems Test Site that CIEMAT owns in CEDER (Soria, Spain). This system has been fully monitored through a year and the results of the monitoring activity, characterizing the long-term performance of the system are shown in this work.     

Wind energy–hydrogen storage hybrid power generation

In this theoretical investigation, a hybrid power generation system utilizing wind energy and hydrogen storage is presented. Firstly, the available wind energy is determined, which is followed by evaluating the efficiency of the wind energy conversion system. A revised model of windmill is proposed from which wind power density and electric power output are determined. When the load demand is less than the output of the generation, the excess electric power is relayed to the electrolytic cell where it is used to electrolyze the de‐ionized water. Hydrogen thus produced can be stored as hydrogen compressed gas or liquid. Once the hydrogen is stored in an appropriate high‐pressure vessel, it can be used in a combustion engine, fuel cell, or burned in a water‐cooled burner to produce a very high‐quality steam for space heating, or to drive a turbine to generate electric power. It can also be combined with organic materials to produce synthetic fuels. The conclusion is that the system produces no harmful waste and depletes no resources. Note that this system also works well with a solar collector instead of a windmill. Copyright © 2001 John Wiley & Sons, Ltd.     

The importance of control strategies in PV–hydrogen systems

The control strategy for a photovoltaic (PV) system with a hydrogen (H₂) subsystem consisting of an electrolyzer, pressurized hydrogen gas storage, and fuel cell has been investigated. Detailed computer simulation models for TRNSYS have been developed, tested, and verified against a reference system, namely the PHOEBUS plant in Jülich, Germany. The basic control strategy and main logical control variables for a PV–H₂ system are described. System performance indicators, parameters, and constraints that can be used to analyze the performance of PV–H₂ systems have been identified. The results from a time series simulation for a typical year are presented. Finally, the importance of selecting smart control strategies is demonstrated.     

A hybrid power generation system: solar‐driven Rankine engine–hydrogen storage

This paper reports on the feasibility of a hybrid power generation system consisting of a solar energy‐driven Rankine engine and a hydrogen storage unit. Solar energy, the power for the hybrid system, is converted into electrical power through a combination of a solar collector, a tracking device to maintain proper orientation with the sun and a Rankine cycle engine driving an electrical power generator. Excess electricity is utilized to produce hydrogen for storage through electrolysis of water. At the solar down time, the stored hydrogen can be used to produce high‐quality steam in an aphodid burner to operate a turbine and with a field modulated generator to supplement electric power. Case studies are carried out on the optimum configuration of the hybrid system satisfying the energy demand. A numerical example based on the actual measured solar input is also included to demonstrate the design potential. Copyright © 2001 John Wiley & Sons, Ltd.     

Study of a solar PV–diesel–battery hybrid power system for a remotely located population near Rafha, Saudi Arabia

This study presents a PV–diesel hybrid power system with battery backup for a village being fed with diesel generated electricity to displace part of the diesel by solar. The hourly solar radiation data measured at the site along with PV modules mounted on fixed foundations, four generators of different rated powers, diesel prices of 0.2–1.2US$/l, different sizes of batteries and converters were used to find an optimal power system for the village. It was found that a PV array of 2000 kW and four generators of 1250, 750, 2250 and 250 kW; operating at a load factor of 70% required to run for 3317 h/yr, 4242 h/yr, 2820 h/yr and 3150 h/yr, respectively; to produce a mix of 17,640 MWh of electricity annually and 48.33 MWh per day. The cost of energy (COE) of diesel only and PV/diesel/battery power system with 21% solar penetration was found to be 0.190$/kWh and 0.219$/kWh respectively for a diesel price of 0.2$/l. The sensitivity analysis showed that at a diesel price of 0.6$/l the COE from hybrid system become almost the same as that of the diesel only system and above it, the hybrid system become more economical than the diesel only system.     

Exergy analysis of a hybrid solar hydrogen system with activated carbon storage

A proposed hybrid solar hydrogen system with activated carbon storage for residential power generation is assessed using exergy analysis. Energy and exergy balances are applied to determine exergy flows and efficiencies for individual devices and the overall system. A ‘base case’ analysis considers the proposed system without modification, while a ‘modified case’ extends the base case by considering the possibility of multiple product outputs. It is determined that solar photovoltaic-based sub-systems have the lowest exergy efficiencies (14-18%) and offer the most potential for improvement. A comparison of these two scenarios shows that the additional outputs raise the exergy efficiency of the modified case (11%) relative to the base case (4.0%). An investigation of the energy and exergy efficiencies of separate devices illustrates how energy analyses can be misleading. The hybrid system is expected to have several environmental benefits, which may offset to some degree economic barriers to implementation.     

A solar hydrogen hybrid system with activated carbon storage

A solar hydrogen hybrid system has been developed to convert, store and use energy from renewable energy sources. The theoretical model has been implemented in a dynamic model-based software environment and applied to real data. A photovoltaic sub-system drives a residential load and, if a surplus of energy is available, an electrolyzer to produce hydrogen which is stored in a cluster of nitrogen-cooled tanks filled with activated carbons; when needed, hydrogen is used in a fuel cell to supply power to the load. Hydrogen storage is achieved through physisorption at low temperature and low pressures. Physisorption storage provides safer operations along with good gravimetric and volumetric capacities at costs comparable to or smaller than compression or liquefaction storage.     

Thermoeconomic analysis of a standalone solar hydrogen system with hybrid energy storage

A comprehensive thermoeconomic analysis is presented for a novel integrated solar hydrogen energy system for standalone operation. The proposed system includes a solar PVT module (photovoltaic thermal), a FC (Fuel cell) and a battery to meet the electrical load demand and domestic hot water over a year. The PVT component works as a primary energy source converting solar energy into electricity and heat. The excess electrical energy and hot water produced by PVT are consumed for producing hydrogen, which can be stored. The generated hydrogen is fed to the fuel cell to produce electricity and water to satisfy the demand. The proposed system is convenient for different seasons of the year because in all time, produced power satisfy the demand. The first and second laws of thermodynamics are used to evaluate the performance of each component and the overall system. Economic assessment of this system is also conducted considering the net present cost, and the system performance is optimized based on this parameter. The overall electrical efficiency of the system is obtained as 9% and the levelized cost of electricity is determined as $ 0.286/kWh. For a steady operation of system, integrating a battery system is convenient when solar energy is not available for a short term. When there is a longer-term shortage of solar radiation, up to 8 days, the electricity can be supplied by utilizing the hydrogen storage system.     

Performance investigation of a hybrid PV‐diesel power system for remote areas

Algeria is in a region with an enormous potential of solar energy for power generation. However, photovoltaic (PV) power plants have not yet been developed sufficiently in the country, and its applications such as PV pumping, solar distillation, and solar heating. The main problem is the high maintenance, operating costs, fossil‐fuel transportation, and CO₂ emission of Bordj Badji Mokhtar's (BBM's) diesel power plant that exhibits a noteworthy issue in south Algeria. This paper presents the results of a theoretical and experimental study for PV/diesel hybrid energy system (HES) considering the load demand profile and the solar radiation in isolated area of south Algeria. Suggested hybridization based on a renewable energy with a view to an improved environment is promising. Study results show the performance of PV/diesel system based on solar radiation. The experiment load curve in this typical area may conduct the diesel generator to operate at 60% to 70% of its nominal power with less fuel consumption, and it has been verified during this study that the implementation of a PV/diesel hybrid system is efficient for higher load and higher solar radiation. Results and discussions are encouraging considering less emission of greenhouse gases and less storage of fuel, which drives the government to draw a political arrangement for the improvement of cleaner forms of electricity generation.     

Weather data and energy balance of a hybrid photovoltaic-wind system with hydrogen storage

This article presents and discusses the results of measurements of solar radiation and wind speed obtained during the operation of a test-bed hybrid wind/solar generator with hydrogen support designed and constructed at the Industrial Engineering School at the University of Extremadura, Badajoz (Spain). An energy balance analysis is made of the different components of the system, calculating their conversion efficiencies, and proposing future improvements to increase the efficiency of the use of the surplus energy produced by the wind/solar generator. The continued collection of this data series will make it possible to perform energy and exergy analyses to allow extrapolation of the results to real stand-alone applications providing an uninterrupted power supply to receptors isolated from the grid.     

Evaluation of a hybrid photovoltaic-wind system with hydrogen storage performance using exergy analysis

This article presents and discusses the results of an exergy analysis conducted during the operation of a test-bed hybrid wind/solar generator with hydrogen support, designed and constructed at the Industrial Engineering School of the University of Extremadura, Badajoz (Spain). An exergy analysis is made of the different components of the system, calculating their exergy efficiencies and exergy losses, and proposing future improvements to increase the efficiency of the use of the surplus energy produced by the wind/solar generator. The results show the electrolyzer to have an acceptable efficiency (η_ex = 68.75%), but the photovoltaic modules a low exergy efficiency (η_ex = 8.39%) as also is the case, though to a lesser extent, for the fuel cell (η_ex = 35.9%).     

Optimization of diesel engine performances for a hybrid wind–diesel system with compressed air energy storage

Electricity supply in remote areas around the world is mostly guaranteed by diesel generators. This relatively inefficient and expensive method is responsible for 1.2 million tons of greenhouse gas (GHG) emission in Canada annually. Some low- and high-penetration wind-diesel hybrid systems (WDS) have been experimented in order to reduce the diesel consumption. We explore the re-engineering of current diesel power plants with the introduction of high-penetration wind systems together with compressed air energy storage (CAES). This is a viable alternative to major the overall percentage of renewable energy and reduce the cost of electricity. In this paper, we present the operative principle of this hybrid system, its economic benefits and advantages and we finally propose a numerical model of each of its components. Moreover, we are demonstrating the energy efficiency of the system, particularly in terms of the increase of the engine performance and the reduction of its fuel consumption illustrated and supported by a village in northern Quebec.     

A wind–diesel system with hydrogen storage: Joint optimisation of design and dispatch

We compare two models to determine the size of grid units and dispatch in a wind-diesel power system with hydrogen storage. Both take as data 1-year time series of hourly wind speed and electricity demand, and their objective is to minimise cost. Our first model, based on linear programming, generates as output a combination of capacities and a year time series for the dispatch variables. Our second model runs a fixed dispatch rule over several capacity combinations and selects the cheapest option. The dispatch rule can then be improved through comparison with the linear programming solution. At present costs, the hydrogen storage-conversion system is excluded from the solutions, so the interesting operation rules associated with the option of harvesting do not arise. However, the costs of hydrogen storage technologies are decreasing with investment. By running our model with prospective costs for year 2010, we see storage emerge in the optimum, and thus a sample of the operation patterns that will occur in a renewable dominated grid.     

Dynamic simulation of a novel nuclear hybrid energy system with large-scale hydrogen storage in an underground salt cavern

In this study, a nuclear hybrid energy system (NHES) with large-scale hydrogen storage integrated with a gas turbine cycle is proposed as a flexible system for load following. The proposed system consists of a nuclear reactor, a steam Rankine cycle, a hydrogen electrolyzer, a storage system for hydrogen in an underground salt cavern, and a Brayton cycle that uses hydrogen as fuel to generate additional electricity to meet peak demand. A dynamic mathematical model is developed for each subsystem of the NHES. To evaluate the potential benefits of the system, a one-year study is conducted, using scaled grid demand data from ISO New England. The dynamic simulation results show that the system is capable of meeting the demand of the grid without additional electricity from outside sources for 93% of the year, while decreasing the number of ramping cycles of the nuclear reactor by 92.7%. There is also potential for economic benefits as the system only had to ramp up and down 7.4% of the year, which increased the nuclear capacity factor from 86.3% to 98.3%. The simulation results show that the proposed hybrid system improves the flexibility of nuclear power plants, provides more electricity, and reduces greenhouse gas emissions.     

A novel hybrid energy system for hydrogen production and storage in a depleted oil reservoir

Renewable and carbon free energy relates to the sustainable development of human beings while hydrogen production by renewables and hydrogen underground storage ensure the stable and economic renewable energy supply. A hybrid energy system combining hydrogen production by offshore wind power with hydrogen storage in depleted oil reservoirs was constructed along with a mathematical model where the Weibull distribution, Wind turbine power function, Faraday's law, continuity equation, Darcy's law, state equation of real gas, Net Present Value (NPV) and the concept of leveling were adopted to clarify the system characteristics. For the case of a depleted oil field in the Bohai Bay, China, the annual hydrogen production, annual levelized cost of hydrogen and payback period are 2.62 × 10⁶ m³, CNY 34.6/kgH₂ and 7 years, respectively. Sensitivity analysis found that the wind speed impacted significantly on system NPV and LCOH, followed by hydrogen price and stratum pressure.     

A hybrid hydrolytic hydrogen storage system based on catalyst‐coated hollow glass microspheres

Hydrogen‐pressurized hollow glass microspheres (HGMs) in combination with a hydride bear the potential of storing hydrogen in feasible amounts. Therefore, the approximately 20‐µm diameter spheres are heated up and pressurized with hydrogen at a pressure of 85 MPa, so hydrogen diffuses into the spheres. After the spheres are cooled down, hydrogen can be stored at room temperature without excessive security measures. To release the stored hydrogen, heat has to be applied again to reach temperatures of about 250 °C (523.15 K). To reach this temperature, it is suggested in this work to use an exothermal chemical reaction, which produces hydrogen as a by‐product. In this case, an NaBH₄–water reaction will be discussed, which has to be initialized by a catalyst deployed on the HGMs. It will be shown that hydrogen storage densities of up to 20 wt% and 50 kg/m³ can be theoretically achieved with the proposed hydrogen storage system consisting of hydrogen‐pressurized HGMs and a hydride, that is, NaBH₄. Volumetric storage density and other aspects, such as water management, temperature restriction, stoichiometric restriction and hydrogen diffusion through glass, will be discussed. Due to resulting high water vapour pressures, a pressure vessel will still be needed in the concept. This paper shall give an overview of theoretically achievable storage densities with the proposed system. Experiments were carried out regarding catalytic promoted hydrolysis with HGMs, and resulting storage densities were determined. These experiments show good agreement with theory. However, they will be addressed only briefly in the outlook of the paper because a detailed discussion would go beyond the scope of this work. Copyright © 2016 John Wiley & Sons, Ltd.     

Thermodynamics analysis of a hybrid system based on a combination of hydrogen fueled compressed air energy storage system and water electrolysis hydrogen generator

In front of the opportunity of the rapid development of renewable energy power generation, energy storage is playing a more important role in improving its utilization efficiency. In this paper, a hybrid energy system based on combination of hydrogen fueled compressed air energy storage system and water electrolysis hydrogen generator is proposed. The superfluous renewable energy power is charged by compressing the air and/or producing hydrogen through water electrolysis. A hydrogen combustor is introduced to raise the air temperature in the discharging process. A thermodynamic model of the proposed system is built. Energy and exergy analysis found that under the design condition, the proposed system can achieve a round trip efficiency of 65.11%, an exergy efficiency of 79.23%, and an energy storage density of 5.85 kWh/m³. The exergy loss of water electrolysis hydrogen generator and hydrogen combustor rank in the top two of all components. Sensitivity analysis indicates that the outlet temperature of hydrogen combustor and specific energy consumption of water electrolysis hydrogen generator are the crucial influencing factor of system performance.     

Electrochemical hydrogen storage characteristics of Mg–Pd–Ni ternary alloys

Mg_1?xPd_xNi (x = 0.03, 0.05, 0.06, 0.07, 0.08, 0.10, 0.20) type alloys were synthesized by mechanical alloying and their electrochemical hydrogen storage characteristics were investigated. The XRD studies showed that Mg₆Pd and Mg–Pd phases form in the high-Pd-containing alloys. The discharge capacities of the alloys increased sharply up to 15 h milling. Further increase up to 25 h did not cause change in the discharge capacities considerably. Among the Mg_1?xPd_xNi ternary alloys, Mg_0.93Pd_0.07Ni alloy was observed to exhibit the best charge/discharge cyclic performance. The hydrogen storage capacity of the high-Pd-containing alloys (Mg_1?xPd_xNi; x > 0.07) deteriorated as Pd content of the alloy increased. This observation was attributed to the Mg–Pd phase formations. According to the EIS experiments as Pd atomic ratio increased up to 0.07 the charge transfer resistances of the alloys decreased. Further increase in Pd atomic ratio, however, brought about the increase in the charge transfer resistances.     

Design of a grid-connected PV system with hybrid energy storage

由于国内的储能技术起步较晚,分布式电源中应用单一储能介质很难满足系统运行要求.基于某公司的光伏储能并网系统示范项目,以具有快速响应特性的超级电容器和具有大容量储能特性的锂离子电池为混合储能系统,以储能控制器为控制核心统一协调控制,使电能以可控功率按需送入电网.该系统可有效提高储能系统的功率输出能力,优化储能系统的充放电过程,延长储能电池的使用寿命,具有良好的应用及推广价值.     

Electrospray‐deposited nickel ferrite thin film electrode for hydrogen production in PV‐assisted water electrolysis system

Nanocrystalline Ni ferrite thin film was prepared by electrospray deposition technique and characterized by different analytical techniques at different annealing temperatures. All these films were studied by photovoltaic‐assisted water electrolysis system for solar to hydrogen production efficiency measurement. Highly dense and uniform surface morphology was observed in as‐deposited film, which changed into agglomerated nanocrystalline grains of irregular size and shape with change in annealing temperature. The X‐ray photoelectron spectroscopy study showed that the as‐deposited film was a mixture of an oxyhydroxide form of iron and an Ni₂O₃ form of nickel, whereas it changed into ferrite phase with change in annealing temperature. The as‐deposited film was observed to be of amorphous phase, which changed to crystalline cubic spinel structure with change in annealing temperature. The solar to hydrogen production efficiency was found to increase in a film with an increase in annealing temperature. The film annealed at 500°C showed a high solar to hydrogen production efficiency (8.29%) with constant performance of up to initial 500 h. Thereafter, the performance slowly declined by 11% when up to 1000 h. Copyright © 2011 John Wiley & Sons, Ltd.