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Hydrogen energy storage system (HESS) has excellent potential in high-proportion renewable energy systems due to its high energy density and seasonal storage characteristics. After detailing the volatility of wind speed, irradiance and load, this paper proposes a bi-level optimization model to analyze the economic operation of the wind-photovoltaic-hydrogen hybrid system (WPH-HS). First, the relationship between the source-load output matching and operating conditions of HESS is studied, two evaluation indicators are described, which can be adjusted by wind-solar complementarity on the source side and demand response on the load side. Second, considering the levelized cost of storage (LCOS), the total annual cost (TAC) calculation method of WPH-HS is presented, and this paper provides a new hybrid optimization technology of chaotic search, particle swarm optimization and non-dominated sorting genetic algorithm2. Finally, the system is simulated with the MATLAB software to determine the optimal sizing of components and minimize the LCOS while ensuring the optimal TAC. The simulation results are elaborated in detail. In particular, the added source-load interaction reduces the TAC and LCOS by 7.3% and 10.3%. When two indicators reach 0.03 and 0.1745, the system is economically viable with the LCOS of 0.276 USD/kWh. The hybrid optimization algorithm can achieve better result in fewer iterations. • The cross-season utilization of the hydrogen energy storage system is discussed. • A price bi-level model about the levelized cost of storage and the total annual cost is established. • Evaluation indicators are presented to promote the source-load interaction. • Effects of wind speed, irradiance, and loads are investigated for the levelized cost of storage. • A hybrid optimization algorithm based on three common algorithms is designed. [ABSTRACT FROM AUTHOR]

Renewable energies are available as clean sources to replace fossil fuels. Providing continuous power without compromising the environment through hybridizing solar and biomass source is one of the promising solutions. This paper seeks to address thermodynamic, economic, and environmental analysis of a multi-generation system with the aim of supplying heating, cooling, electricity, fresh-water, and hydrogen. To do this, the considered system is divided into on-peak, mid-peak, and off-peak periods and modeled based on the consumption pattern at different hours of the day and night. Due to the availability of renewable energy during peak consumption periods, biomass, solar, and hybrid biomass-solar energies are used as energy sources. This leads to a reduction in biomass consumption and carbon dioxide emissions through storing approximately 10 tons of biomass during the day. A sensitivity analysis of the factors affecting the system's function indicated that a growth in solar radiation from 600 to 1000 W/m2, results in a 35% improvement in exergy efficiency, a 2.7% raise in the total cost rate, and a 32.4% drop in CO 2 emissions of the system. Moreover, by changing the biomass flow rate from 0.5 to 1.5 kg/s, the exergy efficiency and total cost rate improved by 9.28%, 1.3%, respectively, and the CO 2 emissions rate increased from 0.41 to 1.14 tons/MWh. In addition, focusing on addressing economic and environmental concerns, the optimization of the proposed hybrid system is performed in two categories of objective functions. In the second category optimization, exergy efficiency, fresh water production, total cost rate and CO 2 emissions are determined as 31.75%, 74.75 kg/s, 324.60 $/h and 3.55 tons/MWh, respectively. [Display omitted] [ABSTRACT FROM AUTHOR]

• This paper reviews the thermal system configurations for solar applications. • The solar energy collection techniques as an input for TEG systems are discussed. • Utilization of rejected heat from TEG for secondary usage is discussed. • Storage and reuse of TEG rejected heat for night-time operations are discussed. • PV-TEG hybrid systems and solar desalination with TEG are discussed. Thermoelectric generators (TEGs) have become a notable topic for research in the last three decades. TEG is a promising element in the field of renewable energy in this age of ever-increasing energy demands. A TEG is a compact, quiet, highly reliable and environment friendly device with no moving parts. Although TEG finds its place in various applications, enhancing its efficiency is a focus in the field of thermoelectrics. Various solar thermal system configurations increase the efficiency of TEG for a given thermoelectric material. This review work predominantly focuses on these configurations for the solar applications of TEG as a vital tool in the field of solar energy. The paper thus, summarizes earlier literature works done to improve the efficiency of TEG through thermal system configurations, provides an outlook of present trends in the applications of TEG in a solar thermal system configuration with an outline of future research in TEG. [ABSTRACT FROM AUTHOR]

Local energy sharing (LES) is a concept that enables sharing between distribution system participants such as consumers, producers, and prosumers at the local level in a transparent and cooperative manner. It can improve local supply-demand balancing, reduce voltage deviations, and improve social welfare. However, the feasibility of such an approach is highly dependent on the regulatory framework and implementation requires investment in an adequate information and communication infrastructure. This paper examines components for the implementation of LES within energy communities in the EU, with a focus on price-forming methods that can be integrated into a net-billing system and adopted for different regulatory set-ups. Further, a method for the assessment of impacts on market participants is provided. The approach is applied for the assessment of the opportunities for LES in the city of Križevci, considering local generation, flexibility options, and real-life regulatory requirements. It is shown that LES under appropriate regulatory provisions can be an effective market-based mechanism for stimulating local generation and flexibility activation, and that way support decarbonization and local self-sufficiency. All members can benefit from participating in the energy community, but the distribution of the benefits notably depends on the applied LES price-forming method. On the other hand, subject to regulatory setup, the trade-offs are reflected on reduced revenues for market participants that generate income based on transmission fees, taxes, and/or surcharges. • Components for local energy sharing (LES) implementation within energy communities. • Framework for feasibility evaluation of LES under different regulatory set-ups. • MILP LES market-clearing model with energy sharing compensation price method. • LES price-forming methods integrated into a net-billing system. • Simulation of LES as a market with a local energy sharing coordinator. [ABSTRACT FROM AUTHOR]

Due to the increase in electrical and cooling demands, the use of renewable resources for supplying these demands are subjected to more attention in recent years. This is while in the hot months of the year, due to the weather conditions, the need for electricity and cooling is increased. In this paper, a hybrid solar/wind system is proposed to satisfy the electrical and cooling demands, and hot water consuming of a building. Cooling demand is covered by combining absorption and compression chillers; so that, the primary energy of the compression chiller is supplied by a wind turbine and photovoltaic (PV) panels and the required thermal energy of the absorption chiller is supplied through evacuated tube collectors (ETCs). Considering the space limitation for installing solar systems, the main issue of this paper is focused on allocating the best space share for each of the PV panels and ETCs (in a case study building, 100 m2 of area is considered as a free space for solar systems). Three cases are assumed for the share of installation space as: 75% of area for ETC and 25% for PV (case 1), half share for both (case 2), 25% of area for ETC and 75% for PV (case 3). All of the defined cases are investigated by developing a comprehensive computational code based on energy, exergy, and economic analyses. The results show that although the first case with energy and exergy efficiencies of 50.60% and 18.5% has the best performance, the third case, with the highest net present value (NPV) has a payback period of nearly 7 years, is the eco-feasible case. Finally, by applying 7 different weights for the defined objective functions (energy efficiency, exergy efficiency, and NPV), a multi-objective optimization is applied to select the best system operation depending on the design requirements. Considering equal weight coefficients, the optimization results reports the case 3 as the optimum configuration. • A multi-generation system for providing electricity, cooling and hot water consuming is proposed. • The wind turbine, ETC and PV collectors and absorption and compression chillers are used. • Three defined cases are assumed for the share of collector installation space. • Energy and exergy efficiencies for first case are obtained 50.60% and 18.5%, respectively. • TOPSIS multi-objective optimization method is applied for selecting the best case. [ABSTRACT FROM AUTHOR]

Costly and eco-destructive diesel based systems are usually used for electrifying rural areas in Malaysia. Fuel transportation is another obstacle in this regard. Moreover, unpredictable fluctuation of fuel price makes the system cost unstable. The diesel based systems can be replaced with renewable energy (RE) based systems. Thus, a feasibility analysis is necessary to assess the potentiality of RE resources. This paper analyzes the potentiality of renewable energy in Sarawak, East Malaysia. The wind speed is insufficient, but solar energy is abundant at the location. Hence, the feasibility of photovoltaic (PV), Battery and Fuel Cell (FC) based systems are investigated for the load of a village longhouse comprising 50 families located in Kapit, Sarawak. Both systems, including FC (PV/Battery/FC) and excluding FC (PV/Battery) are analyzed and compared with conventional diesel based system. The analysis focuses on net present cost (NPC) and cost of energy (COE). Other cost parameters such as installation cost, operation and maintenance cost (O&M), operating cost are also analyzed. HOMER software provided by National Renewable Energy Laboratory (NERL) is used as an analyzing tool. This paper also focuses on the operational strategy and sensitivity analysis of the hybrid system for optimal performance. The HOMER optimization results and sensitivity analysis show that the PV/Battery system is economical and environmentally friendly with total net present cost of $ 335,297 and cost of energy of 0.323 $/kWh with no emission. Thus it can be a suitable replacement of diesel based system. The FC based system has higher costs; thus despite of its benefits, it is not suggested as the best system for the situation. [ABSTRACT FROM AUTHOR]

In this paper, the current and most recent applications of direct contact membrane distillation (DCMD) are discussed. Apart from its rapidly increasing use for the desalination of highly saline feed water, the DCMD is gradually becoming a preferred technology for produced water treatment, purification of groundwater, reclamation of industrial process water, removal of micropollutants from drinking water, juice concentration, and production of chemical products. The fundamentals of the DCMD and governing equations (from heat and mass transfer principles) that describe performance parameters are first explained. Current issues in the DCMD operations such as the influence of membrane type, membrane fouling, and operating conditions on the DCMD performance or productivity are also discussed in this paper. Hybrid systems and renewable energy integration with DCMD systems have been presented as viable solutions that would enhance the sustainability of the DCMD operations. [ABSTRACT FROM AUTHOR]

The maturation of distributed energy resources (DER) has prompted the exploration of their deployment in commercial building applications due to their potential to supply energy at lower costs and emissions rates compared to centralized generation. While several software tools exist for evaluating the techno-economic potential of integrated renewable energy and combined heat and power (CHP) systems for distributed generation applications, many suffer from poor accuracy in capturing off-design (part load and changes in ambient air temperature and pressure) performance characteristics of microturbines, combustion turbines, or internal combustion engines. Thus, this paper presents a methodology for integrating these off-design characteristics in the mixed-integer linear program within REopt, a hybrid DER screening tool. The economic impact of the CHP off-design performance is observed through several application studies of various hybrid system configurations in different climates. Each study indicates how CHP off-design performance influences optimal sizing and dispatch decisions and therefore overall system economic value. We observe through case studies that modeling without the off-design effects, depending on the CHP prime mover and site, can result in Net Present Value predictions of hybrid systems that can be overoptimistic in frequently hot climates (up to 52 %), too conservative in frequently cold climates (up to 11 %), or unaffected (＋/−1 %) in temperate climates. Cases also highlight several advantages of hybrid systems relative to non-hybrid systems such as total economic value and the systems' ability to mitigate potentially negative consequences attributed to off-design performance. • A methodology for off-design performance as a function of load and ambient conditions is presented. • Scenarios where different application climates affect optimal sizing and dispatch are provided. • Not including off-design CHP modeling can result in overly optimistic or conservative economics. • Higher economic values for hybrid systems compared to either renewable energy or CHP-only systems. [ABSTRACT FROM AUTHOR]

In this study, the optimization of a multisource hybrid photovoltaic (PV)/Wind/Diesel/Fuel cell (FC) system is performed to meet three realistic loads demand for heavy, medium and small activities observed at Figuil, Cameroon. This paper also examines and compares the techno-economic viability of an off-grid hybrid PV/Wind/Diesel/FC, PV/Diesel/FC and Wind/Diesel/FC systems in terms of net present cost (NPC), cost of energy (COE) and environmental emissions. The effectiveness of different evolutionary algorithms employed in the designing problem of the various hybrid systems is also investigated. The results revealed that, for maximum loss of power supply probability (LPSP) of 5% and minimum renewable energy fraction of 85%, the PV/Wind/Diesel/FC system is economically the best choice for supplying the three types of non-domestic loads demand with corresponding NPC, COE and LPSP values of 159319.4$, 1.087$/kWh and 0.0397 for heavy activity; 150185.8$, 1.753$/kWh and 0.0411 for medium activity; and 144588.0$, 2.384$/kWh and 0.0288 for small activity, respectively. The results also demonstrated that, in terms of pollution emissions minimization, the PV/Wind/Diesel/FC configuration is a preferable option, with an overall yearly CO 2 emissions of 2946.1 kg, 2043.6 kg and 1504.2 kg corresponding to an annual total fuel consumption of 1115.9L, 774.1L and 569.8L for heavy, medium and small activities, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • The most profitable system is on-grid PV-Wind Turbine system with an NPC of $52.8 M. • For 0% and 25% sale constrained systems low penetration systems are optimal. • For 50% sale constrained and unconstrained systems high penetration systems are preferred. • Fire hawk Optimizer, Grey Wolf Optimizer and Particle Swarm Optimizer are used to size the system by power flow analysis. Fire Hawk Optimizer is found to be usable in optimal power flow analysis and system sizing. • Increase in penetrations leads to enlargement of the system in the region with high load demand because of optimizations. Today, with a human population of 7.5 billion, increasing power consumption, and widespread use of high-technology equipment, the need for energy in the world is increasing day by day. The damage to nature caused by non-renewable energy resources and the economic and political disadvantages they cause in countries that must import these resources have led the world to search for alternative energy sources. One of the most important benefits of renewable energy sources is that they can create hybrid energy systems with other energy sources. Hybrid energy systems are structures in that more than one energy generation unit works together to feed the electrical load. In this paper, a hybrid system will be designed by using Homer PRO, to supply the energy consumed in the residential areas of Karaburun and Urla districts of Izmir province in Turkey with hybrid renewable energy systems. Systems of different sizes are designed for 50%, 75%, and 100% penetration rates, and sales to the grid are constrained to 0%, 25%, 50%, and no constraint on sales. Sensitivity analyses have been performed for 10% and 20% more power required by the load. Techno-economic analyses were done for the systems and the optimal system has been identified. The power flow of the optimal system is inspected by defining the network in Python and Fire Hawk Optimizer (FHO), Grey Wolf Optimizer (GWO), and Particle Swarm Optimization (PSO) are used for optimal sizing of the system. The optimal system has a Net Present Cost (NPC) of $52.3 M, 34 wind turbines, and 954 kW PV with conditions of 100% penetration and no restrictions on sales to the grid. FHO proposed 26 wind turbines and 780 kW PVs for Urla and 8 wind turbines, and 174 kW PVs for Karaburun. GWO proposed 25 wind turbines and 747 kW PVs for Urla, 9 wind turbines, and 165 PVs for Karaburun. PSO offered 24 wind turbines and 708 kW PVs for Urla, 10 wind turbines, and 246 kW PVs for Karaburun. When there is no sale to and 25% sales to the grid, it is seen that the optimal scenario is the system with a 50% penetration rate. In fully sale-constrained systems, NPCs are higher than the base system and they can never pay for themselves compared to the base system. It is concluded that smaller-sized systems are more suitable for systems with high constraints. The proposed FHO algorithm and GWO algorithm react to increasing penetration ratios by enlarging the system size in the regions with high load demand. PSO sizes the system like predictions by load demand. FHO reacts quicker to increasing penetrations than PSO and GWO. FHO algorithm is found to be usable to solve optimal power flow problems and optimal system sizing. [ABSTRACT FROM AUTHOR]

The concept of off-grid hybrid wind energy system is financially attractive and more reliable than stand-alone power systems since it is based on more than one electricity generation source. One of the most expensive components in a stand-alone wind-power system is the energy storage system as very often it is oversized to increase system autonomy. In this work, we consider a hybrid system which consists of wind turbines, photovoltaic panels, diesel generator and battery storage. One of the main challenges experienced by project managers is the sizing of components for different sites. This challenge is due to the variability of the renewable energy resource and the load demand for different sites. This paper introduces a sizing model that has been developed and implemented as a graphical user interface, which predicts the optimum configuration of a hybrid system. In particular, this paper focuses on seeking the optimal size of the batteries and the diesel generator usage. Both of these components are seen to be trade-offs from each other. The model simulates real time operation of the hybrid system, using the annual measured hourly wind speed and solar irradiation. The benefit of using time series approach is that it reflects a more realistic situation; here, the peaks and troughs of the renewable energy resource are a central part of the sizing model. Finally, load sensitivity and hybrid system performance analysis are demonstrated. [ABSTRACT FROM AUTHOR]

It is necessary to have an energy management system based on one or more control strategies to sense, monitor, and control the behavior of the hybrid energy sources. In renewable hybrid power systems containing fuel cells and batteries, the hydrogen consumption reduction and battery state of charge (SOC) utilizing are the main objectives. These parameters are essential to get the maximum befits of cost reduction as well as battery and hydrogen storage lifetime increasing. In this paper, a novel hybrid energy management system (HEMS) was designed to achieve these objectives. A renewable hybrid power system combines: PV, PEMFC, SC, and Battery was designed to supply a predetermined load with its needed power. This (REHPS) depends on the PV power as a master source during the daylight. It uses the FC to support as a secondary source in the night or shading time. The battery is helping the FC when the load power is high. The supercapacitor (SC) is working at the load transient or load fast change. The proposed energy management system uses fuzzy logic and frequency decoupling and state machine control strategies working together as a hybrid strategy where the switching over between both strategies done automatically based on predetermined values to obtain the minimum value of hydrogen consumption and the maximum value of SOC at the same time. The proposed HEMS achieves 19.6% Hydrogen consumption saving and 5.4% increase in SOC value compared to the results of the same two strategies when working as a stand-alone. The load is designed to show a surplus power when the PV power is at its maximum value. This surplus power is used to charge the battery. To validate the system, the results were compared with the results of each strategy if working separately. The comparison confirms the achievement of the hybrid energy management system goal. • Hybrid energy management system designed to minimize hydrogen consumption in FC. • Hybrid energy management system designed to optimize the battery state of charge. • A battery is helping the FC when the load power is high. • A supercapacitor (SC) is working at the load transient or load fast change. • The proposed management systems decreased hydrogen consumption by 20%. [ABSTRACT FROM AUTHOR]

This paper presents an optimal design for sustainable hybrid energy systems for the aquaculture sector, which inherently requires intensive energy. The designed system is energized by renewable resources to produce pure oxygen in situ through water electrolysis for oxygenation according to the changes of dissolved oxygen of species under culture. Moreover, the by-product hydrogen from the electrolysis process is used to generate backup power for an eventual power failure. The mathematical models of the system were developed for simulation and optimization to assess the performance of the system regarding technical, economic, and environmental aspects as multi-objective functions in autonomous mode as well as on-grid mode. The merits of the proposed system are demonstrated at a shrimp farm. Furthermore, the optimal results and their sensitivity analysis showed that the sustainable hybrid energy system operating in grid-connected mode, which possesses such attractive features as producing onsite pure oxygen for oxygenation and utilizing the by-product hydrogen for generating backup power, could bring significant benefits for farmers thanks to a notable reduction in the annualized cost of the system as well as CO 2 emission in comparison with the conventional system, which is powered by the national grid to run common paddlewheel aerators for oxygenation. • Green technology is applied to the aquaculture industry. • Pure oxygen produced onsite for oxygenation leads to higher yield and energy saving. • By-product hydrogen is used for backup power. • Optimal planning and design for an energy system help farmers save operation costs and reduce CO 2. • Useful guidelines to instruct optimum design and operation for aquaculture farms. [ABSTRACT FROM AUTHOR]

• A PV/T system is analyzed in 5 cities with different climate and energy costs. • The cost of energy is the most important aspect in the economic feasibility. • This work facilitates decision-making of where PV/T systems would be installed. • Returns on investment between 2-4.5 years are achieved only with financial subsidy. This paper presents the techno-economic study of a hybrid PV/T system for the simultaneous production of electric and thermal energy under different climate scenarios and energy tariffs. A simulator was developed and validated using TRNSYS software to perform a comparative energy study of five cities with different weather conditions and energy prices: Mexicali, Soria, Bigene, Fresno and Madison. Our work proposes an extended analysis with sites that have not been studied before, and complements the scope of previous work. Under same requirements of thermal energy for DHW demand, energy production was analyzed during an entire year of operation, using different numbers of PV/T modules. Results show that the city of Mexicali is the place where most energy, both thermal and electrical, is produced. In this same locality a solar thermal fraction of 80% can be reached with only three modules installed. Energy feasibility contrasts drastically with economic benefit, where Soria presents the most attractive investment returns and monetary savings of the scenarios analyzed. Moreover, a comparison of investment returns is presented, considering subsidies in the initial investment, where return of up to 1.8 years result with a 75% subsidy. In addition, a relation of the climatic conditions of the studied cities is presented, such as solar radiation and ambient temperature, in the performance of the PV/T technologies. The conclusions of the study help decision making and planning of financial support programs, since it was considered extreme climates and representative of most of the sites where PV/T systems would be installed. [ABSTRACT FROM AUTHOR]

In this paper, a different approach of standalone hybrid distributed generation has been shown. Due to the intermittent nature of the renewable energy resources, the reliability of the power system is decreased using single renewable energy source based electricity supply system. To overcome the problem the size of the storage system exceptionally large which increases the overall cost of the system and drastically reduces the flexibility. To resolve the problem a standalone hybrid power supply system is designed by integrating the solar and wind energy to generate electricity. The hybrid system increases the generation capacity without increasing the storage unit and maintains reliable electricity to the consumer. The proposed system has been modelled using Matlab/Simulink and verify under variable sources and load condition without compromising with the power quality issue. [ABSTRACT FROM AUTHOR]

As the costs of solar PV continuously decrease and pollution legislation imposes less burning of agricultural residues, decentralized renewable energy is increasingly affordable for providing electricity to one billion people lacking access to a power grid. This paper presents a techno-economic feasibility case study of biomass gasification in off-grid and grid-connected mini-grids for community-scale energy application in rural Uttar Pradesh, India. Energy demand data was collected through surveys in a village with irrigation and agro-processing loads and off-grid households and used to construct a seasonal load profile based on statistical methods. This was used to simulate single-source and hybrid mini-grids based on solar PV, biomass gasification and diesel generation using HOMER Pro. Hybrid PV-biomass or PV-diesel systems were found to offer the highest reliability for off-grid power at the lowest cost. Single-source PV was cheaper than biomass gasification, though the cost of electricity is highly sensitive to biomass supply and gasifier maintenance. Both renewable options were around half the cost of diesel generation. The findings held across grid-connected systems with weak, moderate and strong reliability of grid supply. This suggests that biomass gasification-based mini-grids are not cost-competitive with PV unless the two generation sources are combined in a hybrid system, though they require operational testing prior to implementation. Image 1 • Hybrid PV–biomass or PV–diesel systems offer higher reliability at lower cost. • PV is cheaper than biomass gasification mini-grids for productive energy provision. • Grid-connected PV offers lowest LCOE over 20 years for strong and weak grid supply. • LCOE of biomass systems is highly sensitive to biomass requirement and maintenance. • PV–biomass systems appear resilient to operating parameters but lack field testing. [ABSTRACT FROM AUTHOR]

• Effects of carbon reduction targets on the design of desalination systems are studied. • Obtaining carbon-free desalination systems via renewable sources were investigated. • PV-natural gas hybrid systems were efficient up to 80% net carbon reduction target. • The preference of renewable energy over carbon capture depends on the latter's cost. In light of the global concerns for increased greenhouse gas (GHG) emissions, the industrial market is shifting towards more environmentally friendly processes, to meet strict emission standards. Although many studies have addressed the problem of carbon footprint reduction in desalination processes through the replacement of standard fossil fuel options with renewable energy sources, to date, none of these assessment methods have captured the effects of imposing different carbon reduction targets on the optimal design of desalination systems, and their respective energy sources. This paper proposes an optimization-based technique for the design of cost-effective desalination networks, integrated with renewable energy sources, subject to different carbon reduction targets. The presented methodology is capable of identifying optimum configurations for an integrated system that combines desalination options with renewable/hybrid energy technologies, whilst ultimately satisfying the water and energy demand that is required from the entire system. The importance of this approach lies in its ability to guide decision-making activities for such networks. A Mixed Integer Nonlinear Program (MINLP) has been proposed, which ultimately allows for the selection of the best mix between desalination technologies, and associated energy sources, based on a required carbon emission target. The proposed model has been illustrated using a case study, and the sensitivity of attained designs has been studied with respect to a number of key operating parameters. [ABSTRACT FROM AUTHOR]

Off-grid, rural island communities seldom have access to electricity and for those that do, the quality and availability are unsatisfactory. Gilutongan Island is one of the many off-grid islands in the Philippines with very limited access to electricity. Residents are provided with electricity from 6:00 p.m. to 10:30 p.m. through a 194-kVA diesel generator, paying US$ 0.14 per bulb and US$ 0.16 per outlet. Payment for electricity is collected on a daily basis with collections usually amounting to US$ 74.32 per day. With consumption totalling to 276 kW for 4.5 h, this roughly translates to a cost of US$ 1.21 per kWh. Using Hybrid Optimisation Model for Electric Renewables (HOMER), this paper presents a techno-economic analysis of a proposed cost-effective power generation system for the island, aiming to provide electricity access to the residents 24 h a day with reduced energy cost. Two options are considered: diesel-solar hybrid and solar only. Considering location constraints of the island, the hybrid system proves to be more effective, reducing cost of energy by 70% to US$ 0.3556 per kWh. Determining the load profile of the island is imperative in creating the system, dictating its size and capacity, which in turn affects its sustainability. • Current cost of electricity of Gilutongan Island is at US$ 1.21 per kWh. • Multi-year analysis with HOMERPro used in simulation. • Cost-effective system is diesel-solar hybrid system. • Cost reduction is about 70% or US$ 0.3556 per kWh. [ABSTRACT FROM AUTHOR]

Abstract Providing electricity generation is a crucial indicator for development of a country's progress index. Renewable energy resources are rapidly being recognized as important alternatives for clean production of electricity. The present paper aimed to assess the wind and solar data from selected metrological stations in the province of Sistan and Baluchistan in Iran in order to produce hydrogen as a clean fuel. For using wind and solar energies, a detailed techno-economical analysis was presented. At first, the solar energy potential was assessed; indicating that the most part within the province possesses a high radiation intensity of more than 500 W/m2. Secondly, wind resources were examined, revealing the high power density of about 500 W/m2 in Lutak station. According to evaluation of hydrogen production from several small wind turbines, it was shown that the maximum amount of 39.7 ton-H 2 can be produced every year. It was observed that in the best conditions, the cost of 1 kWh electrical energy generated by wind turbine was 2 cents cheaper than the market energy unit price while this value is 8 cents cheaper by employing both wind and solar energies. GIS maps of hydrogen production, wind speed, wind power and global horizontal radiation were produced. Highlights • Wind/solar potentials in the province of Sistan & Baluchistan in Iran are assessed. • A detailed techno-economical analysis is presented using wind/solar energies. • Economical solar energy above 500 W/m2 is observed in several stations. • High hydrogen production of 39.7 ton-H 2 is observed in Lutak station. • The GIS maps of solar/wind/hydrogen are reported. [ABSTRACT FROM AUTHOR]

• A hierarchical model predictive controller is developed. • Little to no modification is required on the architecture of the existing system. • A stable power exchange between the renewable system and the grid is achieved. • Fast variations are completely removed from the battery power. • Increased utilization of intermittent renewable energy is achieved. This paper presents a two-layer control strategy designed for easy integration of supercapacitors in a grid-integrated solar photovoltaic-battery hybrid renewable system, initially controlled by a typical model predictive control method. To operate the upgraded energy system, either without or with little modifications of the pre-existing architecture, an additional control layer is applied at the bottom of the original control system. Considering the complementary characteristics of batteries and supercapacitors, the design of the new model predictive control layer and its coordination with the original one help to deliver a stable power flow between the hybrid renewable system and the utility grid, and remove fast variations from the battery power. Actual measurements of solar radiation in South Africa are used to test the effectiveness of the proposed strategy. Simulations carried out on a 1-MW photovoltaic plant confirm the benefits in terms of adherence to power quality regulations, improved conditioning of the power generated by the intermittent renewable sources, and lifetime extension of the battery. [ABSTRACT FROM AUTHOR]

Abstract Several islands around the world are facing common challenges in terms of high energy costs, local CO 2 emissions, security of supply and system stability. In EU, many islands have become sites of energy innovation, where betting on Renewable Energy Sources is a winning choice to meet their energy needs. In this framework, renewable energies play a key role for supporting the transition of small islands to an autonomous, cleaner and low-carbon energy system – in line with the overall EU Energy Union package and EU2030 goals. This study examines the suitability of using hybrid energy system comprising photovoltaic systems, wind turbines, biomass and diesel generators to meet the electricity demand of Favignana Island, to increase the penetration of renewables in the local electricity grid. Additionally, the energy scenarios simulation aimed at identifying foreseeable energy-environmentally improvements associated to the mutual merging of further energy sectors, such as transportation and heating sector. Consequently, the renewable capacity firming issues can be strongly mitigated by integrating new energy demand components. Thus, this work shows in a systemic overview all the outcomes related to the different energy mix layout, with varying the RES share values compatibly with the local grid electrotechnical constraints. Furthermore, this paper studies the impact that the introduction of electric vehicles into the island car fleet will have on the energy system. The smart energy system's components and sizes have been studied both from an energy and an economic point of view by means of two different software (i.e. EnergyPLAN and HOMER). Highlights • An economically optimised Smart Energy Systems in a small MED island is designed. • Discussion on the synergies of two energy simulation software is provided. • The most cost effective carbon avoidance energy system layout is analysed. • Dump charge and V2G electric vehicles have opposite effects on the electric grid. • 42% RES share in electricity leads to the most cost-effective carbon avoidance. [ABSTRACT FROM AUTHOR]

The field of Energy System Analysis (ESA) has experienced exponential growth in the number of publications in the last two decades. This paper presents a comprehensive bibliometric analysis on ESA by employing different statistical techniques to investigate the underlying science's structure, characteristics, and patterns. The focus of results is on quantitative indicators relating to the number and type of publication outputs, collaboration links between institutions, authors and countries, and dynamic trends within the field. The five and twelve most productive countries have 50% and 80% of ESA publications, respectively. The dominant institutions are even more concentrated within a small number of countries. A significant concentration of published papers within countries and institutions was also confirmed by analysing collaboration networks. These show dominant collaboration within the same university or at least the same country. There is also a strong link among the most successful journals, authors and institutions. Within the field, the Energy journal has had the most publications, its editor-in-chief is the author with both the highest overall number of publications and the most highly cited publications. In terms of the dynamics within the field in the past decade, recent years have seen a higher impact of topics related to flexibility and hybrid/integrated energy systems alongside a decline in individual technologies. This paper provides a holistic overview of two decades' research output and enables interested readers to obtain a comprehensive overview of the key trends in this active field. • A review of more than 12,000 papers in the field of Energy System Analysis (ESA). • Five countries with 50% of publications: USA, China, UK, Germany, Italy. • Strong link among the most successful journals, authors and institutions. • Collaboration networks predominantly include only institutions within the same country. • Strong Nordic influence related to region's energy culture and policy. [ABSTRACT FROM AUTHOR]

This paper proposes a methodology for sizing stand-alone hybrid photovoltaic-wind power generation systems. This methodology makes it possible to optimise the overall performance of the stand-alone system components, based on the premise of guaranteeing the power supply throughout the useful life of the installation at a minimum cost. The sizing is performed in two stages. Firstly, the components of the wind and photovoltaic power generation subsystem are obtained and, secondly, the size of the storage subsystem is determined. For the storage subsystem sizing, account is taken of the variation in efficiency according to the operating point and also the deterioration of the subsystem due to aging and, therefore, the loss of available energy during the useful life of the installation. This methodology is applied to a stand-alone traffic control system located on a secondary road in the Autonomous Community of Valencia (Spain). This system comprises wind and photovoltaic power generation components, a lithium battery bank and various traffic management components. Finally, an analysis of the proposed sizing is made. Satisfactory results are obtained, showing how the proposed methodology makes it possible to optimise the sizing of stand-alone systems with regard to the size of its components, cost and operation. [ABSTRACT FROM AUTHOR]

Distributed energy resources DERs are small scale energy system which could provide local supply when placed at customers' premises. They aggregate multiple local and diffuse production installations, consumer facilities, storage facilities and monitoring tools and demand management. The main challenges when assessing the performance of an off-grid hybrid micro-grid system HMGS are the reliability of the system, the cost of electricity production and the operation environmental impact. Hence the tradeoff between three conflicting objectives makes the design of an optimal HMGS seen as a multi-objective optimization task. In this paper, we consider the optimization and the assessment of a HMGS in different Swedish cities to point out the potential of each location for HMGS investment. The HMGS consists of photovoltaic panels, wind turbines, diesel generator and battery storage. The HMGS model was simulated under one-year weather conditions data. A multi objective particle swarm optimization is used to find the optimal system configuration and the optimal component size for each location. An energy management system is applied to manage the operation of the different component of the system when feeding the load. The techno economics analysis shows the potential of HMGS in the Swedish rural development. [ABSTRACT FROM AUTHOR]

• A green hybrid system based on liquid air energy storage, Kalina, and wind farm. • A comprehensive and systematic evaluation of the proposed hybrid concept. • Applying the monte carlo method and genetic algorithm for the whole proposed system. • Achieving the optimum round trip efficiency and total cost rate of 44.7% and 476 $/hr. • Reaching a payback period of 5.5 years, reducing to half in the reference design. The liquid air energy storage is a cutting-edge technology that covers the geographical drawbacks of other utility-scale energy storage alternatives. The coupling the liquid air storage system with renewable energies and heat recovery units can compensate the grid unstability and lack of their round trip efficiency, respectively. In the present paper, an off-shore wind farm including different wind turbines is assessed from technical, availability, and economic viewpoints to be combined with a liquid air energy storage unit, expolits a Kalina cycle for waste heat recovery. First, a comprehensive energy, exergy, and economic analyses are conducted for the integrated system; then, a coupling of artificial neural network and multi-objective genetic algorithm optimization method are carried out to find the optimum design condition. The findings show that around 93 MWh of the generated power in the wind site during off-peak period can be utilized to charge the system. Then, in addition to power generation in the wind farm, the reference system generates 76.4 MWh of extra power and 585 tons of domestic hot water during peak hours for peak shaving. Based on the optimization results, the round trip efficiency and total cost rate are 44.7% and 476 $/hr, repectively. The result of economic analysis demonstrated that the Enercon E-126 EP4 is the most cost-effective wind turbine for the proposed system, resulting in a period of 5.5 years. It has been also resulted that the existence of the LAES-KC system can half the paybacks. [Display omitted] [ABSTRACT FROM AUTHOR]

In order to effectively harvest solar energy and waste thermal, pulsating heat pipes (PHPs) could be utilized to promote the hot end temperature of the thermoelectric modules (TEMs) and thus enhance its conversion efficiency. This paper explored a novel approach of recovering low grade energy and conversion to electricity utilizing PHP assisted with TEG. This research fully analyzed the effects of various working fluids, input powers, filling ratios, inclination angles and air velocities on the thermo-hydrodynamic and electricity conversion performance of PHP-TEG hybrid system. Our results demonstrated that the peak-to-peak amplitude of output voltage mainly depends on heat inputs and working fluids, and independent of the filling ratios; the inclination angle (from 30° to 90°) has slight effects on the heat transfer performance and thermoelectric generation of PHP-TEG system, due to the advantages of surface tension. In addition, the inlet temperature and flow velocity of cooling water on the thermal recovery efficiency and thermo-electricity conversion performance were further investigated. These results indicated the best heat recovery performance of 80.12% and the maximum thermoelectric conversion efficiency of 1.22% were achieved simultaneously at the situation of 10 °C and 600 mL/min of cooling water. Present investigation could contribute to waste thermal recovery and electronic cooling applications. • A system with pulsating heat pipe (PHP) and thermoelectric generator (TEG) was developed. • Maximum output power was highly dependent on the thermal performance of PHP. • The best performance of this TEG-PHP system mainly depended on working fluid and filling ratio. • Inclination angle has slight influence on the comprehensive performance of PHP-TEG system. • This novel system of TEG-PHP could facilitate efficiently exploitation of solar energy. [ABSTRACT FROM AUTHOR]

This paper presents an Energy Management System (EMS) for hybrid systems (HS) composed by a combination of renewable sources with the support of different storage devices (battery and hydrogen system) that allow its operation without the necessity of grid connection (i.e. a stand-alone system). The importance of the proposed EMS lies in taking into account economic issues that affect to the decision of which device of the HS must operate in each moment. Linear programming was used to meet the objective of minimizing the net present value of the operation cost of the HS for its whole lifespan. The total operation costs depend largely on the reposition costs of its components. Instead of considering predefined reposition years for each component and calculate their net present cost from them (as is commonly considered in other works), in this work it was proposed to use lifetime degradation models - based on the well-known statement that the lifetime depends on the hours of operation and the power profiles that the components are subjected to- from which the repositions are made to check how they affect to the cost calculation and, consequently, to the EMS performance. The behavior of the proposed control is checked under a long term simulation, in MATLAB-Simulink environment, whose duration is the expected lifespan of the HS (25 years). A conventional state-machine EMS is used as a case study to validate and compare the results obtained. The results demonstrate that the proposed HS and EMS combination assures reliable electricity support for stand-alone applications subject to different techno-economic criteria (generation cost and sustenance of battery SOC and hydrogen levels), achieving to minimize the operation cost of the system and extend their lifespan. [ABSTRACT FROM AUTHOR]

Photovoltaic and wind power generations are currently seen as sustainable options of in rural electrification, particularly in standalone applications. However the variable character of solar and wind resources as well as the variable load demand prevent these generation systems from being totally reliable without suitable energy storage system. Several research works have been conducted on the use of photovoltaic and wind systems in rural electrification; however most of these works have not considered other ways of storing energy except for conventional battery storage systems. In this paper, an energy dispatch model that satisfies the load demand, taking into account the intermittent nature of the solar and wind energy sources and variations in demand, is presented for a hybrid system consisting of a photovoltaic unit, a wind unit, a pumped hydro storage system and a diesel generator. The main purpose of the developed model is to minimize the hybrid system’s operation cost while optimizing the system’s power flow considering the different component’s operational constraints. The simulations have been performed using “fmincon” implemented in Matlab. The model have been applied to two test examples; the simulation results are analyzed and compared to the case where the diesel generator is used alone to supply the given load demand. The results show that using the developed control model for the proposed hybrid system, fuel saving can be achieved compared to the case where the diesel is used alone to supply the same load patters. [ABSTRACT FROM AUTHOR]

In the last decade a high amount of photovoltaic and wind power generators have been connected to the electric grid, introducing operational problems for transmission and distribution system operators due to the variability and the non-programmability of solar radiation and wind. The paper concerns an analysis on the benefits in adopting storage systems to reduce the imbalance costs associated to renewable energy sources. An analysis on a photovoltaic system has been performed considering different battery technologies. Discrete-time Markov chains have been used to generate a 20 years' time series of irradiance, that has been used to calculate the PV power production. Markov simulation parameters have been deeply studied in order to optimize them and obtain reliable synthetic data of ground irradiance. This data was then used as input of a hybrid PV and storage model allowing to obtain realistic economic and technical results, improving thus the results respect to the methods based on probabilistic weather simulations. An imbalance tariff has been assumed and its cost has been analysed in relation to the storage system costs. An optimal size for the different battery technology has been investigated considering the reduction of variability of the photovoltaic production and the economic convenience of the hybrid system. The use of Markov chains for the optimization of the battery size can be considered as the major novelty of the proposed approach. [ABSTRACT FROM AUTHOR]

Diesel hybrid autonomous power systems present good potential for remote communities. Fuel consumption and emissions can be reduced by the use of Renewable Energy Sources (RESs) such as photovoltaic (PV) and wind. With a Battery Energy Storage System (BESS), power generation and consumption can be decoupled allowing further reductions in fuel consumption. An interesting scenario is when the diesel genset can be shut down and the load is supplied by the RESs and BESS. In this case, the latter has to form the grid, regulating voltage and frequency, what can be very challenging under highly unbalanced loads and single-phase RESs. This paper discusses the use of per-phase dq control in a grid forming BESS that provides good dynamic and steady-state response. Experimental results on a laboratory test bench of a BESS interface providing regulated balanced voltages under various demanding load conditions are presented. [ABSTRACT FROM AUTHOR]

Renewable systems are especially suited for electricity generation in remote areas but, where high reliability of the electricity supply is required, a hybrid system including electricity storage could be the only solution to avoid the lack of feasibility in single renewable systems. In this paper a hybrid system composed by photovoltaic panels, a biomass gasifier and a battery bank is presented. The system was designed and constructed at the Distributed Energy Resources Laboratory (LabDER) in order to supply electricity to a laboratory complex in the Institut Supérieur des Techniques Appliquées, Democratic Republic of Congo (ISTA-DRC). System behavior was also tested in LabDER prior being installed and operated in the final place. Design characteristics and commissioning results are presented together with the experimental verification of the capability to fulfill the demand with very low fluctuations in the generated electricity supply. [ABSTRACT FROM AUTHOR]

In this paper, a hybrid configuration of ant colony optimization (ACO) with artificial bee colony (ABC) algorithm called hybrid ACO–ABC algorithm is presented for optimal location and sizing of distributed energy resources (DERs) (i.e., gas turbine, fuel cell, and wind energy) on distribution systems. The proposed algorithm is a combined strategy based on the discrete (location optimization) and continuous (size optimization) structures to achieve advantages of the global and local search ability of ABC and ACO algorithms, respectively. Also, in the proposed algorithm, a multi-objective ABC is used to produce a set of non-dominated solutions which store in the external archive. The objectives consist of minimizing power losses, total emissions produced by substation and resources, total electrical energy cost, and improving the voltage stability. In order to investigate the impact of the uncertainty in the output of the wind energy and load demands, a probabilistic load flow is necessary. In this study, an efficient point estimate method (PEM) is employed to solve the optimization problem in a stochastic environment. The proposed algorithm is tested on the IEEE 33- and 69-bus distribution systems. The results demonstrate the potential and effectiveness of the proposed algorithm in comparison with those of other evolutionary optimization methods. [ABSTRACT FROM AUTHOR]

This paper presents a novel energy dispatching based on Model Predictive Control (MPC) for off-grid photovoltaic (PV)/wind turbine/hydrogen/battery hybrid systems. The renewable energy sources supply energy to the hybrid system and the battery and hydrogen system are used as energy storage devices. The denominated “hydrogen system” is composed of fuel cell, electrolyzer and hydrogen storage tank. The MPC generates the reference powers of the fuel cell and electrolyzer to satisfy different objectives: to track the load power demand and to keep the charge levels of the energy storage devices between their target margins. The modeling of the hybrid system was developed in MATLAB-Simulink, taking into account datasheets of commercially available components. To show the proper operation of the proposed energy dispatching, a simpler strategy based on state control was presented in order to compare and validate the results for long-term simulations of 25 years (expected lifetime of the system) with a sample time of one hour. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents two novel hourly energy supervisory controls (ESC) for improving long-term operation of off-grid hybrid systems (HS) integrating renewable energy sources (wind turbine and photovoltaic solar panels), hydrogen system (fuel cell, hydrogen tank and electrolyzer) and battery. The first ESC tries to improve the power supplied by the HS and the power stored in the battery and/or in the hydrogen tank, whereas the second one tries to minimize the number of needed elements (batteries, fuel cells and electrolyzers) throughout the expected life of the HS (25 years). Moreover, in both ESC, the battery state-of-charge (SOC) and the hydrogen tank level are controlled and maintained between optimum operating margins. Finally, a comparative study between the controls is carried out by models of the commercially available components used in the HS under study in this work. These ESC are also compared with a third ESC, already published by the authors, and based on reducing the utilization costs of the energy storage devices. The comparative study proves the right performance of the ESC and their differences. [Copyright &y& Elsevier]

High altitude long endurance (HALE) aircrafts are aerial platforms operating in the stratosphere, providing relay services for wireless communication networks. These platforms are an alternative to increase the effectiveness of future communication. Nevertheless, the power system is a key part that determines the implementation and feasibility of these platforms. One effective and renewable option to power an HALE aircraft is a photovoltaic system (PVS) with hydrogen storage. In this paper, the simulation of the solar/hydrogen closed loop system is carried out for a parametric combination of the subsystems power. Power consumption of the propeller was determined as a function of the aircraft weight in steady flight and in still air. In order to obtain the optimal nominal powers the efficacies are calculated at hourly intervals over the course of the year by means of an analytical energy balance. The proposed method was implemented in an algorithm, which allows fast estimation of the actual time of flight and the system efficiency. Finally, the energy system of three HALE aircrafts was analyzed in relation of their wing area and total and empty mass. [ABSTRACT FROM AUTHOR]

Interactions between different energy carriers (electricity, heat and gas) are considered beneficial for using renewable energy and reducing carbon emissions in the energy system. Nevertheless, the establishment of such hybrid grids or systems, also called multi-, integrated or smart energy systems, remains relatively unexplored. The concept is characterised by great complexity, questioning the common isolated view of energy grids. This paper analyses the changing requirements from historically grown, isolated energy grids towards renewable hybrid energy systems and the associated potential and challenges. A hybrid grid offers alternative use options, which make energy production and consumption more flexible. No peer-reviewed research provides quantitative analysis on the expected utilisation of the electricity, gas and thermal grid in a hybrid grids scenario. However, the traditional grids will compete among each other and increasingly with distributed power generation and consumption by prosumers. In addition, a reversal and reduction of the gas grid and possible new structures of a hydrogen network have to be considered. To achieve the desired savings in energy demand and carbon emissions while maintaining the security of supply and economic feasibility in hybrid energy systems, appropriate technologies, infrastructure financing, integrated system planning based on the relevant data and supportive market frameworks are required. • Historically built energy infrastructures is not ready for the future requirements. • Energy grid integration and information and communication technology enable the efficient use of renewable sources. • Renewable electricity will be at the heart of future energy systems. • Traditional energy grids will compete with each other and with prosumers. • Linking VRE generation with consumers requiring high full load hours at base load (P2G plants) remains challenging. [ABSTRACT FROM AUTHOR]

Hybrid polygeneration systems offer a great opportunity to meet growing energy demands with cost efficiency and environmental benefits. The identification of the optimal solution (configuration and operational strategy) is strongly affected by the relationship between the system and its surroundings. Previous studies have analyzed the influence of boundary conditions on the synthesis of polygeneration systems for buildings. However, local regulations are often disregarded or oversimplified in those studies. Therefore, this paper aims to evaluate the influence of legal conditions on the integration of renewable energy technologies in polygeneration systems for buildings. A comprehensive synthesis model is developed, including different types of legal conditions, such as power exchange modalities, subsidies/surcharges on energy prices and investment costs, and total ban on fossil fuels. Then, the model is applied to the case study of a Brazilian hospital. The current Brazilian net metering scheme is implemented. Results show that natural gas cogeneration is an attractive solution to cover the hospital's energy demands with or without the possibility of selling/exporting electricity. Also, the Brazilian net metering scheme, by itself, is not enough to ensure renewable energy deployment. An in-depth discussion about the conditions that would promote renewable energy integration is reported and recommendations are made on how current policies can be improved, including the need to explicitly address renewable technologies, the application of minimum renewable fractions, and the role of renewable heat/cooling. While the case study considers the specific circumstances in Brazil, it provides insights that can be extended to other countries or applications. • Synthesis model of hybrid renewable polygeneration systems for buildings. • Influence of legal constraints on the integration of renewable energy technologies. • Power exchange modalities, subsidies/surcharges, and fossil fuel ban are considered. • Technical, economic, and environmental analysis of a Brazilian hospital case study. • The Brazilian net metering scheme did not promote renewable energy technologies. [ABSTRACT FROM AUTHOR]

Accurate generation forecasting can effectively accelerate the use of renewable energy in hybrid energy systems, contributing significantly to the delivery of the net-zero emission target. Recently, neural-network-based quantile forecast models have shown superior performance on renewable energy generation forecasting, partially because they have subtly embedded quantile forecast evaluation metrics into their loss functions. However, the non-differentiability of involved metrics has rendered their metric-embedded loss functions not everywhere-derivable, resulting in inapplicability of gradient-based training approaches. Instead, they have resorted to heuristic searches for Neural Network (NN) training, bringing low training efficiency and a rigid restriction on the size of the resultant NN. In this paper, the Indicator Gradient Descent (IGD) is proposed to overcome the non-differentiability of involved metrics, and several metric-embedded loss functions are innovatively customized combining IGD, enabling NNs to be trained efficiently in a 'gradient-descent-like' manner. Moreover, the deep Bidirectional Long Short-Term Memory (BiLSTM) is adopted to capture the periodicity of renewable generation (diurnal and seasonal patterns), and the residual technique is used to improve the training efficiency of the deep BiLSTM. Finally, a Deep Quantile Forecast Network (DQFN) based on IGD and deep residual BiLSTM is developed for wind and solar power quantile forecasting. Practical experiments in four cases have verified the effectiveness and efficiency of DQFN and IGD, where DQFN has achieved the lowest average proportion deviations (all below 1.7%) and the highest skill scores. • First study on the differentiability of quantile forecast evaluation metrics. • The obstacles of applying deep learning to quantile forecast are revealed. • IGD is proposed to overcome the nondifferentiability of quantile evaluation metrics. • The IGD is GPU-compatible and time-efficient. • A deep-learning-based non-parametric quantile forecast model is developed. [ABSTRACT FROM AUTHOR]

In hybrid renewable energy sources containing different storage devices like fuel cells, batteries, and supercapacitors, minimizing the hydrogen consumption is the main target for economic aspects and operation enhancement. External energy maximization strategy (EEMS) is the most popular energy management strategy used with hybrid renewable energy sources. However, gradient-based method is employed in EEMS which has low convergence, moreover it doesn't guarantee the optimum solution. Therefore, this paper proposes for first time an energy management strategy based on recent metaheuristic optimizer of parasitism-predation algorithm employed in hybrid source comprises photovoltaic/fuel cell/battery/supercapacitor for supplying aircraft in emergency state during landing. The main target is hydrogen consumption minimization, this helps in enhancing the power durability to the aircraft in case of curtailment of the main power source. The selection of parasitism-predation algorithm (PPA) is due to requirement of less parameters defined by the user and its high convergence ability. The proposed strategy is compared to other conventional and programmed approaches of state machine control, water cycle algorithm, dynamic differential annealed optimization, spotted hyena optimizer, EEMS, marine predator algorithm, and mayfly optimization algorithm. The obtained results confirmed the superiority of the proposed method achieving efficiency of 95.34% and minimum hydrogen consumption of 15.7559 gm. • PPA based approach is proposed as EMS for hybrid PV/FC/battery/SC. • Hydrogen consumption minimization is selected as the target. • Comparison to SMC, WCA, DDAO, SHO, EEMS, MPA, and MA is conducted. • PPA based EMS robustness is confirmed with 95.34% efficiency and H 2 consumption of 15.7559 gm. [ABSTRACT FROM AUTHOR]

This paper is concerned with reliability based long-term performance assessment of hybrid solar/wind power system. In particular, an analytical expression is obtained for the theoretical distribution of the power output of the hybrid system by taking into account the reliability values of renewable energy components. An expression for the expected energy not supplied (EENS) is also derived and used to compute the energy index of reliability (EIR) that is directly related to EENS. Because the derived expressions involve reliability values which are related to mechanical states of the renewable energy components, the results enable us to evaluate properly the performance of the hybrid system. A numerical example is included to illustrate the results. • Performance assessment of hybrid solar/wind power system. • Expected energy not supplied (EENS) is calculated. • Energy index of reliability (EIR) is calculated. [ABSTRACT FROM AUTHOR]

To reduce greenhouse gas emissions from the conventional power plant, the role of renewable energy-based hybrid systems is essential. These hybrid systems require a proficient energy management system for efficiently managing the energy from different energy sources to maintain the load-supply power balance. This is vital to save energy, diminish energy costs and attain global emission targets. This paper proposes the design of a voting based smart energy management system (VSEMS) of a grid-connected solar-wind-biomass based hybrid energy system. VSEMS utilizes a novel rule-based energy management algorithm (EMA) for taking its decisions. The proposed approach increases customer participation in the decision-making related to their energy supply and also control the intermittency of renewable energy sources efficiently. The efficacy of the proposed algorithm in the real-world environment is validated by doing a case study analysis using yearly usage profile. Results demonstrate the viability and effectiveness of the proposed algorithm in energy management operation. Additionally, results show that the proposed system is economical and quite nature-friendly. • A program has developed to simulate the operation of solar-wind-biomass based hybrid energy system. • A novel voting based energy management system has been proposed. • Solar data, wind data, and biomass data were analyzed with a case study analysis in the location under consideration. • Demand response has been implemented to maintain the load-supply power balance. • The hybrid energy system is cost-effective, efficient, and quite environmentally friendly. [ABSTRACT FROM AUTHOR]

Power-to-gas (P2G) using excess renewable sources is an effective method to reduce renewable curtailment issues in microgrid system. The produced hydrogen is versatile green fuel for different energy sectors, such as electricity, heat and mobility. In recent researches, fuel cell-based system is considered as a promising technology to consume hydrogen (H 2) generated from P2G due to high efficiency and cleanness. However, its economic and thermodynamic adaptability when coupled with intermittent renewable sources remains an open question to be addressed carefully. One of the major challenges in optimizing such system is to simultaneously capture the intraday and seasonal variation of renewable sources & load, as well as the internal thermodynamic process of critical components in appropriate modeling detail. This paper presents a multi-energy system for microgrid in which a wind-powered P2G is coupled with a detailed thermoeconomic model of solid oxide fuel cell/gas turbine (SOFC/GT) hybrid system. A two-level multi-objective optimization of planning and operation together is proposed. For system planning, the optimal balance between the least wind curtailment rate and total life cycle cost (LCC) is determined. To facilitate the coordinate operation of system components, a power management strategy is proposed in response to fluctuations of wind power and electricity load with considerations of multiple thermodynamic safety criteria. Results show that in the selected case, the multi-energy system operates with low wind curtailment rate of 0.63% and high renewable penetration level of 90.1%. The optimized LCC of multi-energy system is £2,468,093 with wind power accounting for 68.35% of total capital investment. With the power management strategy applied, the SOFC/GT could operate under the maximum electrical efficiency of 67.1% with safety constraints satisfied, making up only half investment cost of P2G. To capture seasonal variations, both winter and summer scenarios are detailly analyzed, sensitivity analysis is also carried out to evaluate the interaction between capacities of MES components. • Designing an integrated multi-energy system of wind-powered P2G, storage and SOFC/GT. • Multi-objective optimization method coordinately integrating both design and operation levels by genetic algorithm. • Proposing a novel power management strategy to avoid subsystem unbalance problem. • Wind energy penetration of 90.1% is achieved with low curtailment rate of 0.63%. [ABSTRACT FROM AUTHOR]

• Mixed integer non-linear programming was used for optimization of system operation. • Economic benefits could be obtained by MPC compared to RBC and ON/OFF strategies. • Combine TES, solar PV, and MPC technologies improved the overall system yield. • Different climate conditions upon a MPC strategy were studied in a heating system. Thermal energy storage (TES) systems allow the user to store energy produced from renewable energy sources during lower consumption periods, and to consume it when the energy demand is higher. Moreover, the use of TES systems encourages the user to take advantage of the time-of-use (ToU) tariff structures in the electricity market. Framed in this goal, the present paper evaluated the economic impact of a novel model predictive control (MPC) strategy that employed an inner control algorithm (ICA) to contribute in the cost electricity reduction of 17 different climate zones while the accuracy in results was improved and the computational effort was maintained. The studied system was composed of an air-to-water heat pump (HP), photovoltaic (PV) panels, and a water TES tank. Its response was based on forecasting the weather conditions, grid electricity price, and heating demand as a dynamic controller. Its economic benefits were compared against a rule-based control (RBC) method and an ON/OFF strategy. The results showed that a good operation of the system was strongly linked with proper sizing of the water TES tank and PV panels, especially in the coldest zones. Nevertheless, using the proposed MPC strategy with its ICA, the system was able to reduce the energy cost between 16% and 22% in most heating demanding climates compared to the RBC strategy and between 17% and 46% compared to the ON/OFF one. Moreover, the energy purchased from the electricity grid during on-peak periods decreased dramatically with the MPC strategy, reaching around 90% reduction in almost all studied climates. [ABSTRACT FROM AUTHOR]

The utilization of seawater for drinking purposes is limited by the high specific energy consumption (SEC) (kW-h/m3) of present desalination technologies; both thermal and membrane-based. This is in turn exasperated by high water production costs, adding up to the water scarcity around the globe. Most technologies are already working near their thermodynamic limit, while posing challenges in further SEC reductions. Understanding the current energy status and energy breakdowns of leading desalination technologies will further help in realizing limitations and boundaries imposed while working for improved system performances. This paper comprehensively reviews the energy requirements and potential research areas for reduced SEC of various thermal, membrane-based and emerging desalination technologies. For thermal desalination processes, which consume a large chunk of energy for heating, renewable energy sources can be a viable option for bringing down the energy requirements. Hence, this review also focuses on the potential of desalination-renewable energy integrations. The review extends beyond conventional energy reduction possibilities to utilizing novel, advanced membranes and innovative techniques for energy offsets. The future of desalination for optimized energy requirements is projected to include ultra-high permeability membranes, fouling resistant membranes, hybrid systems, and renewable-energy driven desalination. Unlabelled Image • Improvements in desalination SEC are necessary for efficient system performances. • RO is operating very near to its thermodynamic limit. • Thermal technologies operate far from their current thermodynamic limit. • Desalination hybrids are attractive solutions for reduced energy consumptions. • RE sources can be used for supplying energy to various desalination processes. [ABSTRACT FROM AUTHOR]

• An optimal configuration model of multiport SSTs integrated AC/DC hybrid system is proposed. • A general multiport SST model is established for optimal planning of SST integrated system. • An optimal strategy of multiport SSTs in parallel operation is proposed. • A coordinate strategy of AC and DC cross-zone distributed energy storage is proposed. With the rapid growth in DC energy-using equipment and distributed DC power, traditional AC distribution networks increasingly have problems, such as high loss and poor flexibility. This paper studies an AC/DC hybrid system integrated with multiport solid-state transformers (SSTs) and distributed renewable energy and proposes an optimal configuration model for the AC/DC hybrid system based on a coordinate operation strategy of SSTs and energy storage. First, the composition and topology of the AC/DC hybrid system are proposed. Then, a realistic efficiency model of a multiport SST is established. Based on the minimum operating loss of the SST, a multiport SST dual-machine parallel optimal operation strategy is established. A multi-energy storage system collaborative optimization operation strategy is established based on the electricity price, grid-connected mode and synergistic relationship among each energy storage system. Finally, based on the proposed AC/DC hybrid system model, the optimization objective of the system life cycle net present cost (NPC), constraints and GA algorithm are set. The proposed method is verified by industrial scenarios. The simulation results show that the proposed model can improve the economic and efficiency of the SST integrated AC/DC hybrid system. [ABSTRACT FROM AUTHOR]

The integration of renewable energy technologies (solar, wind, biomass, ocean, geothermal energy) is gaining importance in the United Arab Emirates owing to the high energy demand and greenhouse gas (GHG) emissions. This paper presents the analysis and results of the performance and optimization of a stand-alone solar PV power system with single-axis (horizontal and vertical) and dual-axis solar trackers and a diesel generator (DG) for the city of Khorfakkan, Sharjah. The modeling, simulations, and optimization analysis of the hybrid energy system (HES) were performed with the HOMER software based on the daily energy consumption of 37.75 MWh in the study area. The simulation results show that employing an HES with dual-axis solar trackers is the best power system architecture considering the renewable fraction (48.55%) and levelized cost of energy (LCOE; 0.25 $/kWh). The proposed HES meets the annual energy demand of the city (13,778 MWh) without shortages and with an electricity excess of 9.81%. In addition, the sensitivity analysis shows that the HES with dual-axis solar PV tracking system provides lower electricity costs (250 $/MWh) and the highest GHG emission reduction (69.6%, which is equivalent to the GHG emission reduction of a diesel engine consuming 682,279 gallons of diesel fuel). • Design and modeling hybrid energy system (HES) consisting of tracking solar PV and diesel generator for Khorfakkan in UAE. • Compare different cases of solar PV tracking system based on the levelized cost of energy (LCOE) and renewable fraction. • Optimize the component size of HES to meet the AC primary load for Khorfakkan. • Perform optimization and sensitivity analysis for HES at the actual environmental conditions. [ABSTRACT FROM AUTHOR]

• A novel decision-making procedure for the hybrid system analysis is proposed. • A new set of dimensionless energy, economic and environmental indicators are defined. • A width parametric analysis for different system configurations and loads is made. • Multi-objective optimization with the selection of the best system configurations. • Impact of battery lifespan increase and incentives is evaluated. The development of hybrid renewable systems is an economically competitive solution to reach energy decarbonization and reduction of greenhouse gasses. Based on the literature, energy, economic and environmental indicators were rarely simultaneously employed in the optimization of a hybrid renewable system. In addition, there is no procedures or a set of indicators to be applied uniformly in all applications for the shared analysis. The paper presents a novel energy-economic-environmental multi-criteria decision-making in the optimization of a hybrid renewable system, based on a new set of dimensionless indicators, proposed as a standard for future applications. The procedure compares the entire PV-wind-battery system configuration with the PV-wind, PV-battery and wind-battery system sub-configurations. A width parametric and multi-optimization analysis permit the identification of the most proper nominal powers of each system component. The procedure proposed was applied in a Mediterranean residential building, demonstrating that some system configurations allow complying simultaneously with at least two of the three energy objectives proposed, the cost-optimal level and the maximum reduction of emissions, for specific values of the load. The solar source was the most suitable both from energy, environmental and economic point of view, while the use of the wind source leads to a greater system operating time in the nominal power conditions. The study pointed out and quantified that, for specific loads, PV, wind and battery powers, the development of specific incentives for wind systems and of battery systems with a higher lifespan can help to make the hybrid systems more economically competitive. [ABSTRACT FROM AUTHOR]

• Effects of different storage technologies on a hybrid renewable energy system. • Photovoltaic system, hydrokinetic system and diesel generator. • Five types of storage are considered. • The study is done in the HOMER Pro software. • Sensitivity analysis and variation of the minimum state of charge. This study analyzes the effects of different storage technologies on a hybrid renewable energy system composed of photovoltaic, hydrokinetic and diesel generator. Five types of storage are considered: lead acid, lithium ion, vanadium redox flow, hydrogen and hydrogen-vanadium redox flow. The analysis is mainly based on indicators such as Net Present Cost, Cost of Energy, unmet load and CO 2 emissions. HOMER software has been used in this paper with time-sampling models and sensitivity studies to determine the effects of each storage system. The results show that the vanadium redox flow batteries system presents a lower net present cost and cost of energy. The sensitivity analysis shows that the vanadium redox flow system presents a greater variation of the minimum state of charge (SOC) in relation to the net present cost. However, the system composed of hydrogen and fuel cell present the lowest variation. The two proposed strategies for energy control show the same performance. However, when using the Load Tracking Control, the variation of the minimum state of charge with respect to the net cost is greater than the variation obtained when applying the Load Cycle Control. [ABSTRACT FROM AUTHOR]