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• A new multi-energy combined system utilizes abundant wind/PV to produce hydrogen. • The refined coupling model of the system is simulated and realized. • The judgment matrix method is used to evaluate the system performance. • The optimal capacity of pumped storage achieves the system stability and economy. To achieve "carbon neutrality", clean energy such as wind and solar energy is being developed, but due to the random and intermittent characteristics of wind energy and photovoltaics, the instability of grid connections and the abandoning wind and photovoltaics need to be addressed urgently. This paper proposes a method to solve the problems of grid connection and abandonment in wind and photovoltaic generation systems, that is, to establish a combined pumped storage/wind/photovoltaic/hydrogen production system through the pumped storage and hydrogen production system. The system consists of a pumped storage/wind/photovoltaic complementary subsystem and a hydrogen production subsystem. First, different models in the system are modelled using Simulink and the characteristics of the models are analysed. Subsequently, the wind turbine model and the PV model are simulated to derive the wind-PV complementary characteristic curves, and it is found that the load demand cannot be met by relying on wind-PV complementary power generation alone. To achieve system stability and economy, pumped storage is configured to smooth the output of wind power and PV. After comprehensive consideration, the optimal pumped storage capacity is determined to be 1000 MW. Then, through the simulation of the pumped storage/wind/photovoltaic system, it is found that even though pumped storage can absorb the wind and photovoltaic outputs, there is still a surplus when the wind and photovoltaic outputs are in excess. Therefore, this surplus energy is used for hydrogen production and the configuration of the hydrogen production system is optimized using a particle swarm algorithm to minimize the cost per unit of hydrogen production. After particle swarm optimization, it was determined that the unit cost of hydrogen production was minimized to 3.54 CNY/ Nm 3 for the configuration of 55 electrolysis tanks of 4 MW and 219 lead-acid tanks of 1 MW/2 MWh. Meanwhile, the electrolysis tank simulation model and the lead-acid battery simulation model were used to obtain maps of their operating conditions, hydrogen production and hydrogen storage tank pressure. In view of the addition of an energy storage system to the wind and photovoltaic generation system, this paper comprehensively considers the two energy storage modes of pumped storage and hydrogen production, and proposes a corresponding capacity optimization configuration scheme, which has reference value for improving the consumption and stability of wind and photovoltaics and realizing the sustainable utilization of clean energy. [ABSTRACT FROM AUTHOR]

Graphical abstract System output power along with solar irradiance and SWP power. Highlights • Isolated continuous power generation system at constant voltage using solar energy. • A novel technique using PHES with solar photovoltaic system for reliable and quality power. • Power generation absolutely unaffected by variations or absence of solar irradiation. • System is suitable for rural as well as other areas having open well or other water sources. • Mathematical modelling and simulation using real solar irradiation for performance evaluation. Abstract A novel off-grid small power generation system using locally available sources is proposed in this paper for the areas, where the open-wells or the permanent sources of water are available. Although, the system can be installed anywhere, but its installation in remote and rural areas, where there is no access of electricity, can be an interesting application. The proposed system comprises of a solar photovoltaic (SPV) system, solar water pump, pico-hydro turbine-generator and pumped-hydro energy storage system. Its operation is quite different from all other existing SPV power generating systems. In this paper, an innovative power generation technique is developed, due to which the output power of the proposed system is absolutely unaffected by the changes that occur in solar irradiation. The proposed system does not require the use of batteries, inverter, transformer, and charging or controlling circuits at all. The attractive features of the system are simplicity, reliability and ability to generate continuous power at constant voltage irrespective of variations or absence of solar irradiation. The mathematical model of the proposed system has been developed in the paper. The simulation is carried out using real solar irradiation for performance evaluation of the proposed model. [ABSTRACT FROM AUTHOR]

• Sunbelt countries can develop reliable solar-dominant grids in the absence of wind. • Policymakers should be highly sceptical of low solar technical potential estimates. • Zero energy emissions Malaysia requires about 0.7 TW solar, 2 TWh pumped hydro. • Sarawak-Peninsular Malaysia interconnection reduces storage needs, but not costs. • Inclusion of about 0.4% hydrogen or synthetic methane reduces storage needs and cost. Three-quarters of the global population lives in the sunbelt region (±35o latitude) with excellent access to solar resources. Wind resources at the equator are very limited, while supply chain and permitting delays are slowing wind deployment at a global scale. This paper investigates the potential for solar photovoltaic-dominant 100% renewable grids to be developed in sunbelt countries through a case study of Malaysia. It was expected that the technical potential for solar photovoltaics and off-river pumped hydro would be far in excess of what is required to decarbonise Malaysia's electricity grids. A Geographic Information System analysis determined that Malaysia has the potential to deploy approximately 8.5 Terawatts of terrestrial photovoltaics and 25 Terawatts of marine floating solar on calm oceans. There are roughly 450 Terawatt-hours of energy storage available in the form of off-river (closed-loop) pumped hydro energy storage. A least-cost, 16-year hourly energy balance model was used to determine that an affluent, fully electrified, highly interconnected Malaysia could greatly reduce emissions through the deployment of 660 Gigawatts of photovoltaics and 2200 Gigawatt-hours of pumped hydro, supported by small amounts of hydrogen-based gas peaking. All-in costs for such a fully decarbonised energy system were modelled to be in the range of 95–103 USD per Megawatt-hour. A Sarawak-Peninsular Malaysia interconnected grid could produce a similar electricity cost to two separate grids while reducing the long-term energy storage needs by approximately 33%. Inclusion of about 3 Terawatt-hours (0.1% of average annual generation at 20 Megawatt-hours/capita/year demand) of hydrogen, synthetic methane, or legacy fossil fuels could further reduce long-term energy storage needs by about 30% by helping to ride through occasional prolonged cloudy periods. Policymakers in sunbelt countries should be highly sceptical of technical potential estimates that suggest limited area for solar photovoltaics. Sunbelt countries can comfortably proceed with the development of cheap, reliable solar-dominant grids primarily supported by pumped hydro energy storage and inter-regional transmission. [ABSTRACT FROM AUTHOR]

• Two novel hybrid MPPT techniques, ZOA-ANFIS and GTO-ANFIS, are introduced and evaluated for instantaneous maximum power extraction from solar and wind energy sources. • The Hybrid ZOA-ANFIS-based MPPT technique uses Zebra Optimization Algorithm for optimal power point tacking and ANFIS for enhanced tracking precision through a logical control scheme. • The Hybrid GTO-ANFIS-based MPPT technique uses the Gorilla Troop Optimizer algorithm to optimize wind energy system control parameters, accurately tracking its maximum power point. • The integration of various optimization algorithms with ANFIS-based control systems significantly enhances the advancement and effectiveness of renewable energy utilization. • The research provides a detailed analysis of the system structure and modelling, highlighting the potential applications of hybrid MPPT techniques in renewable energy integration. This paper presents an effective hybrid renewable energy system. This system utilizes primary energy sources represented by both photovoltaic (PV) and wind energy conversion system (WECS). In addition, integrating the battery energy storage system (BESS), the hydrogen energy storage system (HESS), and the supercapacitor energy storage system (SESS), as backup sources which providing reliable simultaneous power supply and loading. A new design for a wind energy conversion system based on a hybrid excitation permanent magnet synchronous generator (HEPMSG) is proposed, and then artificial intelligence strategies are utilized to determine the optimal flow of energy when the system is operating immediately. Moreover, new hybrid maximum power point tracking (MPPT) techniques have been proposed including zebra optimization algorithm (ZOA)-ANFIS-based MPPT and gorilla troops optimizer (GTO)-ANFIS-based MPPT to obtain the maximum power of solar panels and wind turbines, which leads to enhancing the performance of these energy sources. The implemented power flow management (PFM) model is designed by MATLAB/Simulink, considering three various operating cases to evaluate the performance and effectiveness of various backup system configurations under different operating scenarios. According to the results, power can be generated, and load requirements can be efficiently met by applying the proposed PFM strategy, and this leads to the system operating at optimal performance. When comparing two optimization techniques, it will become clear that both give robust performance, but ZOA technique significantly outperforms the GTO technique in the computation time (26.17 % reduction) for the photovoltaic system. On the other hand, in the case of the wind energy conversion system, the ZOA technique achieves a significant reduction in calculation time by 35.5 %. The ZOA technique achieves computation times of 1616.80 s and 672.43 s for the photovoltaic and wind energy conversion system, respectively. [ABSTRACT FROM AUTHOR]

In the last years, the technological development and the increasing market competitiveness of renewable energy systems, like solar and wind energy power plants, create favorable conditions to the switch of the electricity generation from large centralized facilities to small decentralized energy systems. The distributed electricity generation is a suitable option for a sustainable development thanks to the environmental impact reduction, the load management benefits and the opportunity to provide electricity to remote areas. Despite the current cut off of the national supporting policies to the renewables, the photovoltaic (PV) systems still find profitable conditions for the grid connected users when the produced energy is self-consumed. Due to the intermittent and random nature of the solar source, PV plants require the adoption of an energy storage system to compensate fluctuations and to meet the energy demand during the night hours. This paper presents a technical and economic model for the design of a grid connected PV plant with battery energy storage (BES) system, in which the electricity demand is satisfied through the PV-BES system and the national grid, as the backup source. The aim is to present the PV-BES system design and management strategy and to discuss the analytical model to determine the PV system rated power and the BES system capacity able to minimize the Levelized Cost of the Electricity (LCOE). The proposed model considers the hourly energy demand profile for a reference year relating the analysis to the hourly irradiation and the temperature trend for the installation site. Furthermore, the proposed model is applied to design the grid connected PV-BES system installed at the new buildings of the Engineering and Architecture School of the Bologna University, Italy. A multi-scenario analysis is assessed varying the PV-BES system rated power and capacity. The results highlight the technical feasibility and the economic profitability of such a system for the proposed context. A reduction of 25.5% of the electricity cost respect to the grid electricity price benchmark is among the key outcomes discussed in the present paper. [ABSTRACT FROM AUTHOR]

• Solar photovoltaics stored by using cheap and abundant materials. • The Calcium-Looping process is integrated as electricity stored system (40% efficiency) • Electric-to-electric performance of the whole system reaches 57%. • A notable cost reduction could be achieved as alternative to batteries. Solar photovoltaic plants are today a competitive alternative to power plants based on fossil fuels. Cost reduction in photovoltaics modules, scalability and ease of installation of these plants are enabling a rapid worldwide expansion of the technology. Nevertheless, dispatchability still remains as the major challenge to overcome due the intrinsic variability of solar energy. Most of the current solar photovoltaic facilities at large scale lack energy storage while those with storage systems rely on expensive batteries. Batteries are based on elements such as nickel, lithium or cadmium whose scarcity hinder their sustainability for storing energy in the large scale. This manuscript presents a novel concept to integrate thermochemical energy storage in photovoltaic plants. Furthermore, the concept is also directly adaptable to wind power plants to store surplus energy. The paper analyses the suitability of the Calcium-Looping process as thermochemical energy storage system in solar photovoltaics plants. The system works as follows: part of the power produced in the solar plant provides electricity to the grid while the rest is used to supply heat for calcination of calcium carbonate. After calcination, the products of the reaction – calcium oxide and carbon dioxide- are stored separately. When power production is required, the stored products are brought together in a carbonation reactor wherein the exothermic reaction releases energy for power production. The overall system is simulated to estimate the process behaviour and results show that storage efficiencies of ∼40% can be achieved. Moreover, an economic analysis is developed to compare the proposed system with batteries. Due to the low price of natural calcium oxide precursors, such as limestone, and the expected longer lifetime of equipment as compared to batteries, the Calcium-Looping process can be considered as a potential alternative for improving dispatchability in solar photovoltaic plants. [ABSTRACT FROM AUTHOR]

• Hybrid solar photovoltaic-electrical energy storage systems are reviewed for building. • Global status of electrical energy storage for photovoltaic systems is highlighted. • Technical, economic, environmental performances of the hybrid systems are summarized. • Optimization methods and criteria of the hybrid systems are elaborated. Solar energy is globally promoted as an effective alternative power source to fossil fuels because of its easy accessibility and environmental benefit. Solar photovoltaic applications are promising alternative approaches for power supply to buildings, which dominate energy consumption in most urban areas. To compensate for the fluctuating and unpredictable features of solar photovoltaic power generation, electrical energy storage technologies are introduced to align power generation with the building demand. This paper mainly focuses on hybrid photovoltaic-electrical energy storage systems for power generation and supply of buildings and comprehensively summarizes findings of authorized reports and academic research outputs from literatures. The global installation capacity of hybrid photovoltaic-electrical energy storage systems is firstly examined to show the significant progress in emerging markets. Particularly, the latest installation status of photovoltaic-battery energy storage in the leading markets is highlighted as the most popular hybrid photovoltaic-electrical energy storage technology for building applications. The research progress on photovoltaic integrated electrical energy storage technologies is categorized by mechanical, electrochemical and electric storage types, and then analyzed according to the technical, economic and environmental performances. Moreover, extensive research on hybrid photovoltaic-electrical energy storage systems is analyzed and discussed based on the adopted optimization criteria for improving future applications in buildings. It is indicated that the lithium-ion battery, supercapacitor and flywheel storage technologies show promising prospects in storing photovoltaic energy for power supply to buildings. Potential research topics on the performance analysis and optimization evaluation of hybrid photovoltaic-electrical energy storage systems in buildings are identified in aspects of the local adaption, flexible control, grid integration, as well as building resilience and intelligence. This study provides an insight of the current development, research scope and design optimization of hybrid photovoltaic-electrical energy storage systems for power supply to buildings and can serve as an explicit guide for further research in the related area. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel system is proposed for heating, electricity, fresh water, and ammonia production. • The PCMs are incorporated into the system to avoid performance fluctuations. • The effects of different parameters on the system outputs are investigated. • The solar-driven ammonia production shows a good potential for stabilizing non-dispatchable systems. This research paper designs and analyzes a novel integrated solar-driven system for ammonia synthesis, freshwater production and power generation. The trigeneration system contains a solar thermal subsystem, a thermal energy storage system where the molten salt is used as a heat transfer fluid and storage medium, a solar energy-driven Rankine cycle, a multistage flash distillation, a proton exchange membrane electrolyser array, and an ammonia synthesis unit. The proposed integrated system uses solar energy to charge the molten salt, which flows through a heat exchanger and generates steam for the topping cycle. The exhaust stream of the steam turbine provides heat for the multistage flash distillation (MFD) process. A 20 stage MFD unit is proposed where the seawater is utilized as the feedwater in this study. A portion of the produced freshwater is sent to the PEM electroylzer array for hydrogen production, which is used for ammonia production via the Haber-Bosch process. The thermodynamic analysis of the solar driven multigeneration system is analyzed through the Engineering Equation Solver (EES) and Aspen Plus software packages. The novelty of this study relies on the development of a new solar energy-based integrated system and its application for a selected community with over 10,000 residents to meet all of their needs to be self-sufficient and sustainable. Ammonia (for multiple purposes, such as fuel, energy carrier and feedstock), freshwater and electricity are the useful outputs as targeted in this paper. The study incorporates the phase change materials into the system for thermal energy storage purposes. The performance assessments based on energy and exergy efficiencies are carried out for the overall system and its components. Furthermore, the power, freshwater and ammonia production capacities are studied for better demand coverage. The overall exergy efficiency of the system is determined as 12.1 %, where the ammonia synthesis, power generation, and freshwater production capacities are 0.85 kg/s, 17.6 MW, and 143.97 kg/h respectively. Moreover, the study investigates the energy and exergy efficiencies with and without the presence of an air separation unit. The study results show that the air separation unit has less than 0.3% effect on the overall energy and exergy efficiencies. [ABSTRACT FROM AUTHOR]

Pumping water requires a significant quantity of energy and before the industrial revolution, mechanical pulse systems using natural energies were used. Nowadays, a large field of renewable energies is under exploration for autonomous applications such as solar energy to supply pumping systems. The major disadvantage of these systems occurs during periods of low irradiance. The electrochemical battery bank is one of the solutions that can be considered. This paper deals with the comparative assessment for the feasibility of storage bank in small-scale power photovoltaic pumping system for building application. Experimental analysis of PV pumping station with storage is investigated under two dynamic head levels. The obtained results are presented and discussed. [ABSTRACT FROM AUTHOR]

Solar energy being intermittent in nature, can provide a sustainable, steady and high density energy source when converted into electrolytic hydrogen. However, in current photovoltaic market trend with 99% conventional single junction PV panels, this cannot be achieved efficiently and economically. The advent of the multi-junction solar cells (MJCs), with cell-efficiency exceeding 46%, has yet to receive wide spread acceptance in the current PV market in form of concentrated photovoltaic (CPV) system, because of its system design complexity, limiting its application scope and customers. The objective of this paper is to develop a low cost compact CPV system that will not only eliminate its application and installation related restrictions but it is also introducing a highly efficient and sustainable photovoltaic system for common consumer, to convert intermittent sunlight into green hydrogen. The developed CPV system negates the common conviction by showing two times more power output than the flat plate PV, in tropical region. In addition, sunlight to hydrogen conversion efficiency of 18% is recorded for CPV, which is two times higher than alone electricity production efficiency of flat plate PV. [ABSTRACT FROM AUTHOR]

• Hydrogen storage systems enable flexible energy conversion and scheduling. • Hydrogen storage cost accounts for the largest proportion of system cost. • The hydrogen energy storage system has less demand for energy storage space. With global energy consumption increasing year by year, the industrial sectors of the world's countries have never been more urgent in achieving carbon reduction. Renewable energy plays a crucial role in the industrial decarbonization process. As the most mature renewable energy technology, wind and photovoltaic power generation have made significant progress in recent years. However, the intermittent characteristics hinder the efficient use of renewable energy. Existing research provides sufficient support for the flexible scheduling of large-scale renewable energy. Hence, this paper proposes a combined energy system composed of wind power-photovoltaic-energy storage salt cavern with hydrogen as the energy scheduling carrier. The system mainly realizes energy conversion through electrolytic water equipment and fuel cells. Then, Qianjiang City, Hubei Province, is taken as the analysis object, and the working conditions of each component in the system are optimized with the help of an improved particle swarm optimization algorithm. According to the results, the system's contribution to the energy system is discussed, and the system's economy and carbon reduction effect is studied. The analysis proves that the improved particle swarm optimization algorithm has a stronger solving ability. The combined energy system can effectively improve the economy and renewable energy utilization rate, meet the regional electricity demand, and significantly reduce carbon emissions. The economic analysis of the system shows that the operation and maintenance cost of hydrogen storage salt caverns accounts for the largest proportion of the total cost, about 60 %. Compared with several existing large-scale energy storage technologies, it is found that the energy efficiency of the whole system is only about 40 % due to the limitation of technology maturity. Nevertheless, the flexibility of the hydrogen storage system layout is relatively high. The required underground space volume is only equivalent to 1/6 and 1/2 of pumped storage and compressed air storage with the same scheduling capacity. The system will provide a theoretical support for the optimization of energy pattern and layout. [ABSTRACT FROM AUTHOR]

• Highlighting the local potential of Renewable energy resources. • Proposing an algorithm for optimal sizing of renewable energy power systems. • Optimal sizing of proposed PHS-integrated hybrid PV/Wind power system. • Introducing an economic analysis for estimation of levelised cost of energy. The intermittent nature of variable renewable energy resources in conjunction with the fluctuating energy demand of load require using an efficient long-term energy storage means. Pumped Hydroelectric Storage (PHS) has proved its commercial viability as electricity storage technology and eligibility to be coupled with the Renewable Energy Systems (RESs). This paper proposes a simple and efficient procedure for optimal sizing of PHS-integrated hybrid PV/Wind power system for providing sustainable supply of electricity to an urban community in Brack city (27 ° 32 ' N , 14 ° 17 ' E), Libya. The sizing procedure is considered as a constrained optimization problem. The constraints are developed to consider the operating conditions and the output uncertainty of RESs. The sizing algorithm and optimization procedure are explicitly described. Different operating scenarios were considered to identify the optimal size of the hybrid PV/Wind energy system and PHS. Using the measured date of climate conditions and load consumption, the energy production for different sizes of solar PV arrays and wind turbine farms were estimated by System Advisory Model (SAM) software. Based on the Levelized Cost Of Energy (LCOE), the optimum power capacity ratio of PV array to wind turbines farm was 1:5. For the system of optimal size, PHS contribute with a share of 15 % in covering the annual load energy. The obtained results revealed that coupling the hybrid RESs with PHS is cost competitive and reliable alternative for providing sustainable energy supply to urban areas of suitable topographical conditions and high potential of renewable energy resources. [ABSTRACT FROM AUTHOR]

• Solar and wind resources have a relevant temporal complementarity in the Brazilian NE. • Energy mix 40% wind and 60% solar requires minimal storage capacity to supply Brazilian NE load. • Role of storage in reducing the transmission infrastructure needs for renewable energy is evaluated. • Storage increases dispatchability of utility-scale wind and solar power plants. • _______________________________________________________________________________________________ Solar and wind sources together provided more than half of the Brazilian Northeast electricity generation in 2019. This growing share of renewable energies in the Brazilian energy matrix increases the importance of portfolio optimization and the energy storage management. This paper assesses the complementary nature between wind and photovoltaic generation in the Brazilian Northeast, and how this complementarity, together with energy storage, can reduce the shortcomings that the corresponding natural resource intermittency imposes on these sources. The work consists of two main analyses: (i) analysis of the capability in supplying the Brazillian Northeast region power demand with a hybrid wind + solar + storage power plant; and (ii) contingency optimization analysis for hybrid wind + solar + storage power plants. The results show that wind and solar resources are consistently complementary in the region, with a daily Pearson's Correlation Coefficient of −0.51. Also, the load supply analysis shows that a renewable energy mix based on a 40% wind and 60% solar share would require the equivalent of only 6% of its annual generation in storage capacity. An energy curtailment analysis showed that the complementary nature of the wind and solar resources, together with energy storage, can lead to a reduction of up to 11% in transmission capacity demand. [ABSTRACT FROM AUTHOR]