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As a mainstream power storage and supply device, batteries are continuously upgraded. The microfluidic fuel cell has great development potential, and the paper-based microfluidic fuel cell is the latest achievement of its lightweight, which can be applied in the field of medical and biological detection. In this work, the cell models with various folding forms and unconventional absorption pads are creatively constructed, then the influence mechanism on cell performance is revealed by numerical simulation. Both transient and steady-state simulation methods are employed to monitor the whole process of paper-based microfluidic fuel cell. Conclusions show that the cell performance decreases with the increase of folding angle, the peak power density is as low as 1.71 mW/cm2, and the corresponding fuel utilization is only 2.73%. The changes in the absorbent pad shapes have little improvement on cell performance, thus the most direct way is increasing the absorbent pad volume. Moreover, materials with better water absorption capacity can increase the maximum current density to 28.70 mA/cm2, and the appropriate increase of operating temperature can also increase the peak power density to 2.36 mW/cm2, but the effect on the cell is significantly weakened if the temperature exceeds a certain limit. [ABSTRACT FROM AUTHOR]

The global energy sector is currently undergoing a fundamental transformation as it shifts away from fossil fuels towards renewable energy sources. Green hydrogen is one of the most promising energy carriers of the future in the worldwide effort to reduce the carbon footprint of energy systems. The advancement and uptake of green hydrogen technologies depend on various technological, environmental, and economic factors. In this paper, a comprehensive review of recent studies in green hydrogen energy systems (GHES) is conducted, highlighting technoeconomic aspects from the component to the technology and broader system level. Firstly, the technological principles and recent progress of different green hydrogen generation, storage, and utilization technologies are summarized. Subsequently, an in-depth analysis of various technoeconomic modeling and experimental activities focused on integrated GHES is undertaken. By examining applications in the stationary and transport sectors, this review paper offers an assessment of the current state-of-the-art in terms of development and integration options. The technical challenges, key factors, and future research directions of green hydrogen technologies and systems are outlined, demonstrating that an effective, intelligent, and innovative integration of GHES with other technologies will encourage a more efficient use of resources and enhanced energy system flexibility, resilience, and energy security. • Characteristics, components and configurations of green hydrogen systems are presented. • Technoeconomic studies are collected in tabulated form and exhaustively analyzed. • State-of-the-art applications in stationary and transport sectors are discussed. • A critical review is provided to assess green hydrogen economic viability potential. • Challenges and prospects are evaluated, and future research directions are suggested. [ABSTRACT FROM AUTHOR]

Renewable energy communities with members which own electric vehicles (EVs) can benefit financially from the flexibility that EVs provide to distributed energy resources, such as photovoltaic generators. However, in residential environments, this benefit is often lost because during working hours, most EVs are not plugged in at the premises of the community. In this paper, we hypothesize that such communities can regain some of this lost benefit by offering membership to outside EV owners which are interested in charging their vehicles using the community's charging stations during these periods. This paper introduces an optimization model for energy communities consisting of prosumers, electric vehicles, and EV chargers. The model aims to evaluate the potential advantages of integrating external EV owners into an energy community. A hypothetical community representing a multi-apartment building is analyzed, considering scenarios both with and without external members. The analysis focuses on assessing the technical and economic benefits. The findings indicate that the economic benefits for the examined community are relatively small. However, a notable increase in these benefits is observed when the community is incentivized to share energy among members in the form of a flat network charge reduction for shared energy. [ABSTRACT FROM AUTHOR]

Hydropower has played an important role in Europe in recent decades, offering a unique combination of safe, low-cost, and clean power generation. Today, it is still one of the largest renewable energy sources (RES), accounting for about 35 % of RES electricity generation. However, grid stability is threatened by the increasing amount of undispatchable RES. Flexibility and dynamics such as energy storage and rapid response are urgently needed to achieve EU policy goals. In such a context, hydropower can play a key role, not only as a provider of regulated renewable energy but also due to its ability to balance a renewable energy system in the short term and the medium/long term by pumped storage technology. All these aspects underline the new role of hydropower, which aims to strengthen grid stability and power supply resilience and to enable higher penetration of volatile RES. In this context, the aim of this paper is to demonstrate the role of hydropower at the European level as well as the needs and opportunities of modernization to fully exploit its potential. In particular, this study provides, the assessment of the today flexibility offered by hydropower to the power system at the European level by leveraging a database of information collected through the participants to the working groups of the COST Action Pen@Hydropower which includes stakeholders in the hydropower sector of 34 European countries. The study confirms the key role of hydropower in future energy scenarios with 30 % of the flexibility demand at all time scales met by hydropower. Furthermore, the paper presents a review of the digitalization solutions and innovative technologies that support the growth of a new generation of sustainable hydropower together with the modernization opportunities for existing hydropower plants. The results of this work have practical implications for stakeholders in the hydropower sector and policymakers as it provides evidence at the European scale of the role of hydropower technology in balancing the power system and the need to have supportive frameworks and adequate markets to fully exploit the European hydropower potential to achieve the energy transition goals. [ABSTRACT FROM AUTHOR]

The carbon neutrality goal places greater demands on integrated energy system (IES) in rural areas. In line with this trend, a multi-objective stochastic-robust based selection-allocation-operation cooperative optimization model is established for planning of rural IES in this paper. Firstly, this paper construct three typical IESs at three levels (user, township and user-township interaction) and make economic selection. Secondly, in order to coordinate the objectives of technology-economy-environment and solve the multiple uncertainties existing in the system, a multi-objective stochastic-robust planning model is proposed. In the model, the objective function introduces indicators such as total cost, primary energy resource efficiency and renewable energy consumption rate. Then constructing stochastic hierarchical scenarios to characterize the stochastic uncertainty of parameters in the time dimension. And introducing typical scenarios into the box sets which characterize the supply-demand sides uncertainty. Finally, a sensitivity analysis is performed to discuss the influence of robustness parameters and biogas prices. The annual total cost of the user-township interaction system is 53.8 % and 8.4 % lower than that of the other two systems, respectively. And from the allocation results of selected system, primary energy resource efficiency is 0.57, total cost is 1.81 × 106 USD and renewable energy consumption rate is 99.46 %. In addition, from the operation results, it is analyzed that the output of the equipment is perfectly balanced with the user's load. Finally, it is obtained by sensitivity analysis that uncertainty budget and biogas price have an impact on the selection of discrete equipment, the capacity of continuous equipment and the total cost. And the optimal capacity of the system under different situations is given. [ABSTRACT FROM AUTHOR]

Increasing the demand for water and energy resources as well as the clean energy policies and the need for pollution emission reduction has developed the research on the renewable energy resources. This paper reviews the recent advances in multi-generation units for heat, electricity, and desalinated water production. It tries to investigate the new papers in this arena which were not mentioned in the previous reviews. The main parts of this work introduce the co-generation systems for the production of "water and electricity", "heat and water", and "electricity, water, and heat". The results show that among the solar energy receiving devices, Photovoltaic/Thermal panels (PV/Ts) and parabolic trough solar collectors are the most used in co-generation systems. On the other hand, a combination of solar collectors and power cycles makes them a suitable choice for the establishment of a large-scale co-generation plant. Therefore, solar collector-based electricity and water co-generation systems have at least 10 times more output capacity than PV- or PV/T-based systems. On the other hand, most heat and water co-generation systems can achieve an output temperature of 60 °C or more and produce around 10000 kg/year of freshwater based on system size. Examining the co-generation systems of water, electricity and heat also shows that these systems have a high production capacity compared to other co-generation systems. Systems based on heliostat solar tower can produce maximum powers of more than 18 MW and fresh water of 90 kg/s. • Recent advances in solar multi-generation units are reviewed. • PV/Ts and parabolic trough solar collectors are most used collectors in cogeneration systems. • RO and MED have more applications in solar-based co-generation units. • Using waste heat can increase technical and economic performance of system. [ABSTRACT FROM AUTHOR]

Integrating biomass, photovoltaic, and other renewable energy sources for hydrogen production can form a biomass-photovoltaic-hydrogen integrated energy system (BPH-IES). The system features multi-energy storage and joint supply, as well as cascaded utilization, is a promising co-generation way to meet the system's electricity, heat and hydrogen needs, and has significant energy-exergy-economy-environment (4E) performance. Therefore, scientific and effective evaluation of the BPH-IES is an important prerequisite for promoting its development. Firstly, by analyzing the structure of the BPH-IES system, this paper constructs a comprehensive performance evaluation index system of the system from the 4E dimensions. Secondly, a hybrid multi-criterion decision making (MCDM) framework for the 4E comprehensive performance evaluation of the BPH-IES is constructed, in which the anti-entropy weighting method is used to determine the objective weights, the subjective weights are determined by the decision making trial and evaluation laboratory method improved by intuitionistic fuzzy sets, and the final combined weighting results are obtained based on a game-theoretic method that the objective and subjective weights' heterogeneity can be fully minimized. The grey-relation-analysis-based measurement alternatives and ranking according to the compromise solution method is proposed to determine the ranking of alternatives. This paper selected 8 typical BPH-IES cases for 4E evaluation analysis. The results showed that energy performance is the core dimension that reflects the 4E performance of the system, and system's economy indicators such as energy supply income and energy supply cost will also significantly affect the system's 4E performance. Therefore, the 4E performance of BPH-IES can be effectively improved by expanding the system's demand and supply scale and increasing the system's installed proportion of clean energy and hydrogen penetration. Finally, the ranking consistency test, Leave-One-Out analysis and sample separation test demonstrate that the developed hybrid MCDM can ensure robustness meanwhile improve the decision efficiency. [ABSTRACT FROM AUTHOR]

In recent years, the government has attached great importance to promoting innovation in new energy technologies, particularly in the area of solar power generation. Photovoltaic (PV) power generation has become an essential factor in the promotion of renewable energy due to its inherent safety, environmental sustainability and abundant solar energy resources. The efficiency and stability of PV generation systems are closely related to the accurate prediction of real-time global horizontal irradiance (GHI). However, some existing research methods have made some progress in hourly resolution, but the multi-step prediction accuracy and model generalization ability in high time resolution are still unsatisfactory. Therefore, this paper proposes a novel minutely multi-step irradiance forecasting based on all-sky images using LSTM-InformerStack hybrid model with dual feature enhancement scheme. In this scheme, the advantages of both LSTM and InformerStack models are combined to further enhance the global and local features, which can better capture the short-term time series patterns and long-term dependencies and improve the accuracy of the time series. The experimental validation results show that the performance of this prediction scheme is improved by 11.2%, and 26.0% for nRMSE and R2, respectively, and the 24-step prediction can be improved up to 26.1% vs. the persistent model. Meanwhile, the prediction scheme of this paper is also expected to provide a reference in future multi-step time series accurate prediction with higher resolution. [ABSTRACT FROM AUTHOR]

This paper proposes a cam frequency-increasing hybrid piezoelectric electromagnetic energy harvester with center symmetric structure (C-HEH). The use of the cam structure allows the harvester to increase the efficiency of energy harvester per unit time, while the center symmetric structure of the entire harvester allows for maximum energy output in a limited size. This paper studies the influence of the number of cam protrusions and the length of the cylindrical permanent magnet on the output voltage signal at different rotation speeds. When the number of cam protrusions is 3 and the length of the cylindrical magnet is 10 mm, the maximum peak-to-peak voltages of the piezoelectric and the electromagnetic power generation unit are 53.74 V and 3.16 V, respectively. The effective value power of the hybrid energy harvester can be obtained as 1.49 mW. A series of application experiments were carried out to verify the performance of the C-HEH. The hybrid energy harvester can easily light up 86 light-emitting diodes (LEDs) lights and make the scientific calculators work stably after rectification. These results demonstrate the giant prospect of piezoelectric-electromagnetic energy harvesters for supplying wireless sensor networks and low-power electronic devices. [ABSTRACT FROM AUTHOR]

In many countries distributed energy resources (DER) (e.g. photovoltaics, batteries, wind turbines, electric vehicles, electric heat pumps, air-conditioning units and smart domestic appliances) are part of the 'Green Deal' to deliver a climate neutral society. Policy roadmaps, despite providing a framework and penetration targets for DER, often lack the network planning strategies needed to transition from passive to active distribution networks. Currently, DER's dynamic performance parameters and location identification techniques are not fully standardised. In fact, it can be very ad hoc. Standardised distributed load modelling and non-intrusive load monitoring (NILM) for equipment manufacturers, installers and network operators is critical to low and medium voltage network management in order to facilitate better balancing, flexibility and electricity trading across and within the power system for mass DER deployment. The aim of this paper is to fill this load modelling and NILM knowledge gap for DERto inform the 'Green Deal' transition and support standardisation. In the paper, existing load modelling techniques and NILM methodologies are critically examined to inform and guide research activity, equipment development and regulator thinking, as well as network operators. Seven key findings that need urgent attention are identified to support a smooth power system reconfiguration. [Display omitted] • A thorough review of existing monitoring and modelling methods for DER on distribution networks is provided. • Efficacies between 65% and 95% for conventional load identification exist. • Increasing DER penetrations are creating technological challenges in distribution networks. • Optimum DER integration in low voltage networks is vital for electric networks reliability. • Seven aspects to enable massification of DER on distribution networks are established. [ABSTRACT FROM AUTHOR]

The overall operational costs of home energy systems (HES) has been considered as an objective function (OF) by many articles. This paper shows that considering the energy cost as OF can lead to a decrease in the load elasticity against the electricity price, which can lead to demand response programs failure. So the distribution system operator (DSO) must stop this decline. A new index is introduced to calculate the responsiveness of the PV-integrated HES, based on which a new OF for home energy management system is proposed. This index shows the load elasticity against the electricity price. The relation between energy cost and load responsiveness index is investigated, and several scenarios are analyzed to demonstrate the applicability of the proposed approach in real cases. The proposed method is implemented to a PV- and ESS- integrated HES. The results show the relation between the responsiveness of the loads and the operational costs of home. A sensitivity analysis is added to the paper to show the robustness of the proposed control scheme. • Considering the energy cost leads to a decrease in load elasticity against price. • A new index is proposed to calculate the responsiveness of HEMS, based on a new OF. • Home loads responsiveness index relation with the energy supply cost is discussed. • Roles of ESS to improving the responsiveness of residential loads are investigated. • ESS roles to reduce negative effect of PV in increasing PAR of HES are investigated. [ABSTRACT FROM AUTHOR]

Distributed energy systems are becoming increasingly popular worldwide. The 100% renewable energy system can be an important energy supply alternative to reduce the carbon emissions and address energy shortage, especially for remote areas. However, the performance of 100% renewable energy system (RES) at community level needs further detailed analysis, which is affected by the climates, availability of renewable energy and local energy markets. This paper proposes a design optimization framework of 100% renewable energy systems for low-density communities and investigates the system performance. To investigate the integration and performance of 100% RES, thirty typical cities located in different regions of China were chosen considering different climates, geographical features, and renewable energy distributions. By taking the economic performance as the optimization objective, the optimal design for the 100% RES is obtained, and the energy and economic performance is analyzed. Results show that, under the current energy market conditions, the 100% RES is feasible for low-density communities in most regions of China. The payback periods of the systems in most cities are less than six years. When the cost of PV is reduced by half considering future technological developments, the payback period of a 100% RES can be reduced by 30%–60%. This paper would provide design suggestions and application recommendations in regard to promoting 100% RES in China. • Application of 100% renewable energy system at community level is studied. • 30 zones are selected considering climates, renewable energy sources and markets. • Solar energy and biomass can contribute to over 90% of the total energy supply. • Investment of 100% RES can be paid back in 6 years for most regions. • Payback periods can be reduced by 30%–60% when PV technology is further developed. [ABSTRACT FROM AUTHOR]

Hydropower plants play an integral role in energy supply and are one of the main renewable energy sources. The efficiency of hydropower reservoir systems is controlled by operating rules that need to be optimized to maximize energy production. Here, a novel optimization algorithm, influential flower pollination algorithm (IFPA), is developed in this paper. IFPA has three enhancements: an efficient exploration mechanism based on an adaptive coefficient, a new exploitation mechanism around the best solution, and a rank-based strategy to smoothly transition from exploration to exploitation. IFPA is tested in two benchmark multi-reservoir systems and a real-world five-reservoir hydropower system in Iran. The results show IFPA outperforms other advanced methods in terms of convergence speed and preciseness to achieve the global solution. The tested algorithms include adaptive guided differential evolution (AGDE), composite DE (CODE), hybridizing sum-local search optimizer (HSLSO), improved teaching learning-based optimization (ITLBO), self-adapting control parameters in DE (jDE), self-adaptive TLBO (SATLBO), and a multi-strategy hybrid of DE and particle swarm optimization (MS-DEPSO). IFPA also achieved better total power production in the real-world case study compared to other algorithms. Overall, IFPA can provide better solutions with less power deficit and shows as a promising method for optimizing hydropower reservoir problems. [ABSTRACT FROM AUTHOR]

In this paper, the authors present a two-step model to obtain quasi-optimal solutions for the storage and transportation of renewable energy as its installation becomes more widespread in remote areas. The model is formulated as a total cost minimization linear programming problem and considers both renewable energy facilities and the energy supply and demand of the entire country. The first step of the model optimizes the entire country, while the second step determines the marginal capacity of energy storage and transportation facilities when the excess production capacity of remote renewable energy is added. This approximation for reducing computational complexity is shown to be sufficiently accurate under realistic conditions. The authors apply the model to analyze energy storage and hydrogen production at renewable energy power plants in Japan in 2050. The study shows that photovoltaic power generation uses storage batteries attached to the power plant for electricity transmission. In contrast, wind power generation transmits most electricity directly without storage batteries and converts some into hydrogen for consumers. The proposed lightweight model allows for numeral sensitivity analyses, which provide valuable insight into optimizing energy storage and transport of renewable energy. • We developed a 2-step model for quasi-optimization of equipment at VRE site. • This model optimizes energy storage and transport with VRE deployment. • If additional VRE is sufficiently small, the model division retains sufficient accuracy. • Energy supply costs minimized by combining power transmission and H 2 transportation. • PV has large LIB, while WT has direct transmission and H 2 production. [ABSTRACT FROM AUTHOR]

The fundamental way for China to achieve carbon peak and carbon neutrality is to continuously improve the penetration of renewable energy (RE) in the power system and establish an electricity mix dominated by RE power. According to China's 14th Five-Year Plan, the proportion of non-fossil energy power generation should reach about 39% by 2025. However, the impact of the increase in share of RE power on carbon emissions of the electricity sector remains to be estimated. To this end, the purpose of this paper is to capture the nonlinear characteristics of RE on electricity-related carbon emissions by using panel smooth transition regression (PSTR) model and provincial panel data covering the period 1991–2020 under the background of provincial RE quota system. The estimation results indicate that, (i) in the four transition variables of PSTR model such as the installed capacity of power generation, substation equipment capacity, total electricity consumption and total power generation, the nexus between RE deployment and electricity-related carbon emissions was detected as nonlinear. (ii) The heterogeneous RE carbon abatement effect is reflected in its increasing penetration in provincial power systems. (iii) Carbon abatement performance of RE generation decreases in the negative range with the increase of transition variables. (iv) The estimation coefficient of RE is positive at the higher value of the transition variable in the PSTR model of carbon emissions per capita. As a result, the RE quota with the best emission abatement performance should be designed based on the provincial power resource endowment and the medium and long-term expected electricity consumption. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of the wave climate and a characterization of the wave energy resources in American Samoa, a U.S. territory covering seven south central Pacific islands and atolls. A numerical wave model based on WAVEWATCH III® and unstructured SWAN was developed, validated, and executed for 1979–2020 to generate a hindcast dataset suitable for resource characterization. Model-data comparisons were performed with measurements collected in situ and from satellite-based altimeters. The model was found to perform well with a bias in significant wave height of −0.14 m and −0.06 m against buoy and altimeters, respectively. The multimodal sea state of American Samoa is investigated by identifying the sources of energy reaching the islands and partitioning the wave spectrum accordingly. The wave resources characterization follows the International Electrotechnical Commission Technical Specifications to be compatible with studies performed for other U.S. regions. The average omnidirectional wave power at 2 km from shore around Tutuila, the main island of American Samoa, is 14 kW/m. Locations east and west of the islands have a more consistent resource throughout the year because the northwest and southwest swells that are dominant during different seasons complement each other. • A wave model covering the American Samoa EEZ was developed and validated. • The first wave resources characterization of American Samoa following international standards. • Wave power averages 15 kW/m with a standard deviation of 12 kW/m 2 km from shore. • Wave power has low monthly variability on the east and west shores of the main islands. [ABSTRACT FROM AUTHOR]

The power system transition to large penetrations of renewable generation has become a core target of decarbonisation roadmaps in many countries. However, switching from synchronous to variable inverter-based resources has prompted technical concerns linked to the reduction in system inertia and short circuit levels. This may result in significant deviations in frequency and bus voltages during fault events. Hence, this paper provides a comprehensive review of power system stability challenges when integrating up to 100% inverter-based resources. The potential solutions from several enabling technologies (i.e., energy storage, controllable loads, wind, solar PV, etc.) are also assessed to mitigate anticipated issues. The review further details the role of grid codes and international standards in maintaining dynamic stability in power systems with extremely high up to 100% variable renewable generation. Finally, discussion and recommendation pathways are provided to inform industries and accelerate a secure power system transition to meet Net Zero targets. [ABSTRACT FROM AUTHOR]

At present, energy represents a key element in the social and economic development of a territory. This is particularly true for fragile territories that are not interconnected, such as small island states. As is true for many of the Small Island Developing States (SIDS) worldwide, the energy situation of the Comoros is substantially based on fossil fuel imports. The socioeconomic development of this archipelago is overwhelmingly dependent on energy security from sustainability, availability and affordability perspectives. As a forward-looking response to energy vulnerability, the deployment of renewables to diversify the generation of electricity appears to be an essential prerequisite for guaranteeing a sustainable future. Nevertheless, despite a high potential for renewable energy, only 3.8% of the electricity supply in the Comoros is provided by hydropower. This paper provides a comprehensive overview of the energy situation throughout the Comoros and focuses on renewable energy opportunities to facilitate the supply of green power. This study ultimately shows that renewable energies are rarely exploited despite the powerful potential of different resources. Finally, this paper attempts to provide recommendations for the Comoros to pursue a more sustainable future. • Analysis of the current energy situation of Comoros. • Defining renewable potential and ongoing actions. • Analysis of the specific barriers and policy to the development of RES in the Comoros. [ABSTRACT FROM AUTHOR]

This paper presents an overview of current electricity generation and consumption patterns in the Arctic. Based on published data and new data collection this paper provides an overview of the installed capacity per energy source. A more detailed view of electricity systems is also presented, showing how different types of resources can be used and combined within Arctic communities. The paper briefly discusses which aspects of transmission systems are of special interest under the harsh climatic conditions of the Arctic. A description is given of the various electricity generation technologies that have been proven to be effective for use in Arctic environment, and those that are currently in use, including diesel, hydropower, photovoltaic, and wind power, in addition to discussion of different back-up options. Furthermore, for a more holistic view concerning such energy systems the socio-economic dimension is addressed with a focus on energy security, through an investigation of energy availability and affordability in the Arctic. The availability of energy in the harsh Arctic environments can be crucial for survival and affordability, and can have a huge impact among low-income communities. • Overview of current electricity generation and consumption patterns in the Arctic. • Potential use of different energy resources in the Arctic. • Arctic Energy security. • Socio-economic dimension of energy systems in the Arctic. [ABSTRACT FROM AUTHOR]

The increasing demand for renewable energy sources has led to the development of HRES that combine multiple sources of renewable energy to provide a reliable and efficient energy supply. However, renewable energy sources typically come with higher costs than conventional energy production methods. Hence, the optimal sizing of HRES is essential to prevent the oversizing of the system while ensuring a reliable supply of load demand, accommodating variations in meteorological conditions and changes in power demand. Numerous research papers addressing the optimal sizing problem are available in the literature. However, none of the mentioned studies take into account the power degradation of all renewable sources. The degradation of renewable sources, such as PV and WT, can have a significant impact on the performance of HRES. The degradation of PV panels can result in reduced efficiency and output, leading to a decrease in the overall energy production of the HRES. Similarly, WT may experience wear and tear over time, leading to reduced performance and output. The reduction in the output of renewables in the standalone system causes an increase in the loss of power supply probability (LPSP). This paper analyzes the optimal sizing of the HRES, considering the degradation of the sources. Further, analysis has also been carried out based on the number of BESS to be added to HRES to meet the derived constraints and their impact on the cost of energy as well. [Display omitted] [ABSTRACT FROM AUTHOR]

The increasing demand for renewable energy sources has led to the development of HRES that combine multiple sources of renewable energy to provide a reliable and efficient energy supply. However, renewable energy sources typically come with higher costs than conventional energy production methods. Hence, the optimal sizing of HRES is essential to prevent the oversizing of the system while ensuring a reliable supply of load demand, accommodating variations in meteorological conditions and changes in power demand. Numerous research papers addressing the optimal sizing problem are available in the literature. However, none of the mentioned studies take into account the power degradation of all renewable sources. The degradation of renewable sources, such as PV and WT, can have a significant impact on the performance of HRES. The degradation of PV panels can result in reduced efficiency and output, leading to a decrease in the overall energy production of the HRES. Similarly, WT may experience wear and tear over time, leading to reduced performance and output. The reduction in the output of renewables in the standalone system causes an increase in the loss of power supply probability (LPSP). This paper analyzes the optimal sizing of the HRES, considering the degradation of the sources. Further, analysis has also been carried out based on the number of BESS to be added to HRES to meet the derived constraints and their impact on the cost of energy as well. [Display omitted] [ABSTRACT FROM AUTHOR]

With the development of multi-energy systems and the urgent demand for low-carbon energy provision, the regional integrated energy system (IES) is considered an efficient paradigm to improve energy efficiency and carbon emission reduction. The optimal capacity planning of different IES components is considered a non-trivial task due to the uncertainties of renewable power generation and various demands (e.g., electricity, heating and cooling) as well as the carbon emission constraints. This paper addresses this challenge and presents a scenario-based robust optimal planning solution for the regional low-carbon IES fully considering the economic cost, carbon emission and energy supply reliability. The operational uncertainties of different forms of energy sources and demands are characterized by a controllable generative adversarial network (GAN). The proposed method is extensively assessed based on an IES case study in China through a comparative analysis, the numerical results show that compared with the traditional planning method, the proposed capacity planning solution can reduce the total cost by 4.24% and the carbon emissions by 42.61%, the effectiveness and benefits of the planning solution have been effectively confirmed. • A scenario-based robust capacity planning solution of IES with carbon emission consideration is proposed. • A controllable GAN-based scenario generation is adopted for operational uncertainty characterization. • The proposed solution can reduce both the total cost and carbon emissions. [ABSTRACT FROM AUTHOR]

Renewable energy attracts increasing attention from both industry and academia under the context of carbon neutrality. For wind and solar energy, the strong dependence on natural processes results in the imbalance between energy production and real demands. Energy storage technologies, e.g., Compressed Air Energy Storage (CAES), are promising solutions to increase the renewable energy penetration. However, the CAES system is a multi-component structure with multiple energy forms involved in the process subject to high temperature and high-pressure working conditions. The CAES system is a complex process flowsheet consisting of charging and discharging process. The process should be optimized to achieve the best thermodynamic and economic performance. Under the optimal design conditions, it might lead to severe consequences once a failure occurs, e.g., harm to humans, the environment, and assets. Limited attention and scarce available information have been paid to the CAES system risk management yet. Hence, this paper applies the System-Theoretic Process Analysis (STPA), which is a top-down method based on system theory, to identify the CAES system safety hazards. The results are expected to provide a preliminary guideline for practitioners regarding the safety and reliability of the CAES system. As a result, a more reliable CAES system can contribute to a more flexible energy system with more efficient and economic utilization of fluctuating renewable energy. [ABSTRACT FROM AUTHOR]

The growing energy demand places its focus on renewable energy resources as a sustainable energy resource. Wind Power is one of the important sources of renewable energy. However, it exhibits challenges in the form of stability and control when integrating with the conventional grid. Though the connection of wind power plants does not require any major redesign, it is, however, necessary to ensure that issues are taken care of through control and compensative devices, to enable the grid to recover from grid faults and system disturbances. One such proposal is discussed here. This paper analyses the design and implementation of Proportional-Integral (PI) controlled Static Synchronous Compensator (STATCOM) controllers and is compared with Fuzzy Logic Controlled(FLC) STATCOM controllers. These controllers are primarily used to stabilize the voltage in wind power plants by preventing tripping of Wind Generators (WG) in the event of a grid side disturbance or fault and can recover from the fault by injecting reactive power in the grid. This paper applies STATCOM for restoring the voltage levels at the terminals of the wind power plants and simulated using MATLAB Simulink. It is observed from the simulation results, that STATCOM with fuzzy logic controls tends to reduce the voltage fluctuation and ensure the stability of the system as compared to STATCOM with PI. • STATCOM with PI controller improves voltage regulation. • Enhanced performance with the usage of STATCOM with Fuzzy Logic controller. • Enhanced gain stability in the event of network disturbances. • Improves transient performance. [ABSTRACT FROM AUTHOR]

This paper assesses the effects of inserting solar and wind power in a hydro-dominated electricity system that has been at risk of outages in the short term. The extent to which renewables could contribute to overcoming potential critical conditions has not received much attention given the intermittency of the sources. In this context, this paper proposes a robust optimization model that, under different scenarios, estimates the implications of building new power plants based on renewables and traditional technologies. It considers costs, average construction times, and blackout events. Hidroituango, a mega hydroelectric project – prone to non-completion due to failures during its construction phase – is considered here because it threatens Colombia's future energy security of supply. Model results indicate that investing in hydro or thermal power units could be risky and twice as expensive as investing in renewables. Findings show that solar and wind technologies, in a ratio of 2.5 to 1, make part of the optimal and secure expansion plan for the Colombian power system. Besides reducing the CO 2 emissions of the electricity sector, in the scenarios analyzed, these renewables show fewer blackouts (between 15 and 40% less) than the traditional technologies and more water savings in reservoirs. • Solar and wind power (RES) are the best options to face the Hidroituango crisis. • RES should replace Hidroituango's missing capacity rather than hydro, coal or gas. • RES scenarios could be twice as cheaper as the business as usual scenarios. • RES would allow more water savings in reservoirs than traditional technologies. • RES scenarios show lower blackout probabilities than traditional technologies. [ABSTRACT FROM AUTHOR]

This paper presents and compares three approaches to deal with the uncertain nature of energy supply and demand in the problem of optimal sizing of a stand-alone, reliability-constrained hybrid renewable energy system. The system is composed of wind turbines, photovoltaic solar panels, a battery bank, and a diesel generator. The proposed approaches are: (a) adaptive robust optimization with unmet demand as the (un)-reliability metric, (b) scenario-based robust satisficing, and (c) stochastic-free robust satisficing. A column-and-constraint generation algorithm is developed to solve the adaptive robust optimization problem. Furthermore, the theoretical connection between the proposed approaches is drawn, and their numerical performances are compared, in terms of optimal solution cost and reliability, through computational experimentation on a realistic case study. Numerical results show that both the computational times and the out-of-sample performances of the optimal solutions obtained from the two proposed robust satisficing approaches outperform that of the adaptive robust optimization approach, providing a strong justification for their application • Robust optimal design of a stand-alone hybrid renewable energy system. • Adaptive robust optimization versus robust satisficing optimization. • Optimization under the uncertainty of demand and supply. [ABSTRACT FROM AUTHOR]

In the context of increasing integration and relevance of distributed energy resources, this paper proposes an advanced public policy to maximize their long-term benefits through optimal regulated electricity market management. More specifically, the focus is on renewable distributed generation and energy storage systems. The proposed policy arises from three models or techniques, i.e., the optimized tariff model (regulated electricity market model), Bass diffusion model (long-term forecasting of the integration of distributed energy resources), and random walk (risk assessment technique), along with a stochastic optimization problem. The policy leads to socioeconomic welfare maximization while ensuring fairness for all the market players and enhanced control by the regulatory agency on the integration of distributed energy resources. By applying the policy to a concession area located in northeastern Brazil, where photovoltaic distributed generation systems dominate the market share, results demonstrate that it is highly valuable as a 156 (MR$) mean socioeconomic welfare gain was achieved when optimizing the design variables (compared to a non-optimal solution). [Display omitted] [ABSTRACT FROM AUTHOR]

This paper proposes an optimal sizing design and cost-benefit evaluation framework for stand-alone renewable microgrid system to serve rural community load usage in Northeast China. The microgrid system combines Photovoltaic arrays (PV), Wind turbines (WT), Tidal turbines (Tid), Battery (Bat) storage and hydrogen storage, respectively. The optimal component sizing is determined based on the actual local hourly meteorological data and load demand during a year using Chameleon swarm algorithm (CSA), with minimum Total net present cost (TNPC) of the microgrid system as the optimization objective and the reliability constraint is considered as Loss of power supply probability (LPSP). Meanwhile, a cost-benefit index is further introduced for conveniently evaluating the overall effectiveness of the microgrid systems. The results of the simulation experiments under the benchmark scenario reveal that the PV/WT/Tid/Bat system is the most viable approach for local load supply among different versions of the microgrid. Additionally, a thorough sensitivity investigation of the optimal sizing of two exemplary microgrid systems based on different energy storage is carried out under different techno-economic scenarios. This study can provide a more efficient and clean electrification scheme and insightful reference for investment in the power-starved Northeast China. [ABSTRACT FROM AUTHOR]

The coordinated scheduling of the cascade hydro-photovoltaic hybrid system can significantly alleviate the adverse impact from the intermittence of solar energy resources and hence improve the overall stability of bundled power output. The traditional short-term scheduling strategy of cascade hydro-photovoltaic systems is generally based on a fixed time step, which cannot efficiently adapt to the ever-changing photovoltaic output. In this paper, a novel artificial intelligence-assisted short-term scheduling model with hybrid time steps is proposed, where the time-frequency characteristics of photovoltaic output are taken into consideration. The photovoltaic output is estimated by a data-driven long short-term memory network. The Hilbert-Huang transform is used to analyze the time-frequency characteristics of the photovoltaic power. The hybrid scheduling time steps are determined according to the analyzed instantaneous frequency of photovoltaic power. A short-term optimal scheduling model based on data-driven photovoltaic output evaluation and hybrid time intervals is established to minimize the operational fluctuation of hydropower units and to track the planned output curve simultaneously. Finally, a comprehensive index involving the safety, economy, and operational efficiency is established to compare the overall performance of the hybrid time step model and that of the fixed time step models. The results demonstrate that the proposed hybrid time step model yields the lowest comprehensive ranking score of 1.00, obviously better than the figures for the fixed 60-minuite step model (2.86) and the fixed 15-min step model (2.20). It indicates that the proposed model can achieve the optimal compromise of overall performance via adaptive scheduling time steps. [ABSTRACT FROM AUTHOR]

This paper presents the first comprehensive hourly-resolution scenario study of the Indian electricity system with a view to investigate the transition from fossil to renewable energy-based power generation. Currently, India is 76% dependent on coal for power generation, however ambitious goals exist. Energy organisations including International Renewable Energy Agency and The Energy and Resources Institute, have presented scenarios but neither with support of dynamic simulation nor with assessment of optimal renewable energy contributions. In this paper, the optimal electricity system is analyzed in comparison with these. Results show that an optimal scenario could supply the hourly electricity by (i) increasing production capacity to about 615 GW, which is a 98.3% increase compared to the 310 GW in 2016, (ii) improving capacity factor of wind power and photovoltaic to 27% and 21% respectively, (iii) increasing wind power production to 433 TWh/yr (from 46 GWh/yr in 2016), solar photovoltaic to 290 TWh/yr (12 GWh/yr in 2016), river hydro to 42 TWh/yr (7.7 GWh/yr in 2016), biomass and nuclear power of 15 GW each. The costs of the identified optimal scenario are lower than of the previous scenarios. Finally, simulations show that inclusion of optimal proportion of biomass and nuclear could avoid any import dependency. • Design and analysis of renewable energy scenarios for India. • Evaluation of the cost structure of renewable energy scenarios. • Comparison with official Indian scenarios. • Proposes the Renewable Nuclear Dependency Index (RNDI) for evaluating scenarios. [ABSTRACT FROM AUTHOR]

The development and utilization of renewable energy sources can not only effectively reduce carbon dioxide emissions, but also provide access to electricity to more parts of the world. A standalone hybrid system based on renewable sources is a promising way to supply reliable and continuous power in remote areas to which the grid has not extended. This paper designs and investigates a photovoltaics (PV)-wind-hydropower station with pumped-storage installation (HSPSI) hybrid energy system in Xiaojin, Sichuan, China as case of study. HSPSI can use the available flow of the river and store surplus energy generated from wind and PV by pumping water from the lower reservoir to the upper one. From the perspective of the investors, the techno-economic index is usually used to design the PV-wind-HSPSI hybrid energy system which aims to find the optimal configure with maximum power supply reliability and minimum investment cost. The trade-off analysis between the two objectives is based on Pareto optimality theory by means of Multi-Objective Particle Swarm Optimization (MOPSO). Besides, this paper takes the curtailment rate (CR) of the wind and PV power into consideration due to policy requirements. The relationship between the two objectives under various CR are analyzed and compared. Several results can be obtained as follows: 1) Comparing with the PV-HSPSI and wind-HSPSI hybrid energy system, the levelized cost of energy (LCOE) of the PV-wind-HSPSI hybrid energy system can reduce by 32.8% and 45.0% respectively. 2) For the PV-wind-HSPSI hybrid energy system, the LCOE can be as low as 0.091 $/kWh when 5% LPSP can be acceptable. 3) The policy of CR is unfavorable for the investors which leads to a higher investment cost. 4) Particle Swarm Optimization (PSO) performs better than genetic algorithm (GA) and Simulated Annealing method (SA) with a least LCOE. 5) both MOPSO and weighted sum approach (WSA) have a good performance to find the Pareto fronts and its hypervolume indicator (HV) is calculated. • A real PV-wind-HSPSI hybrid system is designed in Xiaojin, Sichuan, China. • The curtailment rate is introduced into the techno-economic index. • The LCOE can be as low as 0.091 $/kWh when 5% LPSP can be acceptable. [ABSTRACT FROM AUTHOR]

The ambient energy as an available and harvestable energy source which has a high potential to generate electricity for powering electronics devices. Piezoelectric materials, as one of the well-known energy harvesting mechanisms, play a significant role in converting ambient energy into electrical energy, particularly in small electronic devices such as measuring devices in remote or hostile environments where batteries are not an acceptable option. For this reason, piezoelectric energy harvester (PEH) can help to optimize the weight of structures. In addition, PEH can produce an output voltage in response to the inputs such as thermal, electrical, mechanical and electromagnetic energies. This paper provides a holistic review of the energy harvesting techniques from fluid flow using piezoelectric materials. To this end, the recently conducted research studies in the context of energy harvesting based on the fluid flow motion have been reviewed, considering various modeling and methods for improving the PEH efficiency. Various types of energy harvesting mechanisms, based on vibration by using piezoelectric, have been investigated to identify their opportunities and challenges. • Energy harvesting techniques related to fluid flow is reviewed. • The survey is focused on harvesting internal and external flow by piezoelectric. • Such alternative energy can supply energy for fluid flow at different sizes. • Totally, 199 papers are reviewed and suggestions are presented for future works. [ABSTRACT FROM AUTHOR]

This paper presents a harvester that collects vibrational energy. The piezoelectric sheet deforms under mass inertia and then generates electricity according to the piezoelectric effect. At the same time, when designing the equipment, the incentive model is selected as the non-contact type to avoid mechanical collision and wear inside the structure and improve the service life of the device. An equivalent damping analysis is performed for the cantilever and combined with the control equations of the Lagrangian. The simulation analysis obtains the native frequency of the rectangular and circular piezoelectric sheets under the mode analysis. Through experimental proof that the device reaches the maximum output voltage 67.19 V when magnet 1 in the mass mutually repels magnet 1 in the housing and magnet 2 in the mass and magnet 2 in the housing. For an external resistance of 10 KΩ, the maximum power output of the device is 165 mW. The device can convert the vibrational energy in the environment into electricity and supply power to other devices through circuit storage. [ABSTRACT FROM AUTHOR]

The reliable supply of electricity and freshwater is linked to the living quality of local residents in remote islands. A renewable driven standalone combined power and water supply system with cascade electricity and heat storage is proposed in this paper. The hybrid wind-solar power system acts as the energy source and the humidification dehumidification (HDH) desalination is employed for freshwater production. The underwater compressed air energy storage (UW-CAES) is introduced to smooth the renewable fluctuations, whereas the heat storage system for heat addition purpose of HDH desalination is utilized to reduce dumped power during UW-CAES charging. The simulated results show that the suggested system can satisfy electricity and freshwater demand well. The lower loss of power supply probability (LPSP) or loss of water supply probability (LWSP) requires larger renewable installed capacity. At same threshold situation, the renewable configuration of LWSP is larger than that of LPSP. The performance comparison among different system structures implies that this system has lower renewable configuration and total dumped energy. Moreover, the coefficient of performance of heat pump (COP), the heat storage system capacity, the basic freshwater demand, the flexible energy bag volume and the humidifier seawater inlet temperature have obvious effect on system performance. [ABSTRACT FROM AUTHOR]

This article analyzed the location and concentration of forest bioelectricity in Brazil, from 2000 to 2019, available from the National Electric Energy Agency (ANEEL) and used the following indicators: Location Quotient (QL), Concentration Index [CR (k)], Herfindahl-Hirschman Index (HHI), Hoover Index (H) and Coefficient of Gini (G). The main results showed that the supply of electricity from Brazilian forest biomass increased from 562.90 MW and 11 thermoelectric plants in 2000 to 3532.61 MW and 115 thermoelectric plants in 2019, providing an average growth of 10.15% yy of the granted installed power and 13.20% p.a. of thermoelectric power plants. The QL inferred a high concentration of energy supply from black liquor (Rio Grande do Sul, Paraná, Espírito Santo, Bahia, Maranhão and Mato Grosso do Sul) and forest residues in several states, mainly in the North region. At the state level, the CR (4), CR (8) and HHI indexes indicated a deconcentration trend. The identification of the location and concentration pattern that the greatest offer was associated with industrial pulp and paper complexes. These results can indicate to investors the impact of electric power generation in the sector and the most relevant location for the installation of new thermoelectric plants. [ABSTRACT FROM AUTHOR]

Hydroelectric power plants have been losing competitiveness to renewable resources in Brazil, specifically wind and solar power resources, given the current water crisis in the country, which has left main reservoirs in the Brazilian hydroelectric power system depleted. However, other renewable energy resources show disadvantages in terms of intermittence and energy storage. Pumped Hydropower Storage (PHS) can help mitigate this problem, supplying energy with fewer variations. This paper studied using PHS concepts together with solar and/or wind renewable resources to recover water levels at the Furnas reservoir in terms of energy and economic performance. The energy studies were developed by sizing the PHS and identifying solar and wind resource potential for supplying energy for pumps in the hydropower plant. The economic analyses considered three different scenarios (I; II and III), and used the NPV (Net Present Value), and LCOE (Levelized Cost of Electricity) methods for a period of 30 years. Energy calculations showed that 1692 MWh/day of energy could be generated using PHS. However, 2729 MWh/day of energy would be needed to store generated energy, and a 1037 MWh negative energy balance will be compensated for by using daily wind and/or solar photovoltaic power production. This would allow the Furnas reservoir to regain 0.45 m of its water level per year. The economic studies showed economic viability for PHS scenarios I and III, with estimated NPV at 151.5 million dollars, and 64.5 million dollars for the last year of the project, respectively. Scenario II was unviable, giving rise to several strong discussions on this application within Brazil. • Wind and solar sources were considered for the pump energy supply. • The proposed system can recover 0.45 m/year of the level in the Furnas reservoir. • The energy production of the reversible power plant was estimated as 1,692MWh/day. • Economic feasibility was evaluated in many scenarios using NPV and LCOEmethods. • Market regulation is required for the diffusion of this technology in Brazil. [ABSTRACT FROM AUTHOR]

The exploitation and utilisation of solar energy is challenging because of both diurnal and seasonal variation. Seasonal thermal energy storage is a prominent solution to solve the problem of seasonal variation of solar production. This paper investigates both the optimal design and energy management of a renewable energy plant with seasonal thermal energy storage. As a case study, the thermal, cooling and electrical energy demands of a university campus during one year are considered. Three scenarios, characterized by a different available area (20,555 m2, area covered at present; 50,000 m2, potentially available area by exploiting the entire rooftop and parking area; unlimited area) for solar thermal collectors and photovoltaic panels are investigated. In the first two scenarios, the exploitation of solar energy allows a primary energy saving of 31% and 57%, respectively compared to the use of a conventional plant. The seasonal storage reaches an overall efficiency (thus considering both charging and discharging) up to 84%. Finally, the analysis of the third scenario shows that the feasibility of meeting the energy demands by only exploiting solar energy is technically challenging because a large area equal to about 100,293 m2 is needed for solar thermal collectors and photovoltaic panels. [ABSTRACT FROM AUTHOR]

— Seasonal and location dependence of renewable energy resources have limited their applications in power generation. Energy storage systems are promising solutions to the intermittence of renewable energy resources. Rural electricity grids are faced with economic sustainability challenges due to low power demand and poverty. A rural grid design around economic drivers like agriculture and micro industries can mitigate poverty and improve economic sustainability of rural grids. This paper presents an integrated design for photovoltaic power generation with a pumped hydro storage system for irrigation and community utilization. The design explored the natural availability of water body in an elevated settlement area that offers a natural storage height for hydro energy storage. A photovoltaic generation plant was designed to power a pump as a turbine system for water storage and generation. HOMER® energy simulation software was deployed in the simulation. The result shows a satisfactory net present cost for the possible integration of a pumped hydro storage system in a photovoltaic generation plant as the most viable option to provide power at a power supply probability of 99.9% and water for irrigation. The benefits from the irrigation and water supply will enhance the community's socio-economic development and sustain the investment. [Display omitted] • We proposed a strategy to help an African community to have access to electricity. • The scheme will provide irrigation facilities and water supply to the community. • Photovoltaic Generation System was deployed as the primary energy source. • Intermittence of renewable energy was addressed through pumped hydro storage. • The result shows a satisfactory net present cost and 99.9% power supply probability. [ABSTRACT FROM AUTHOR]

The disordered energy use in traditional agricultural production has resulted in high energy purchase costs and carbon emissions. The coupling of integrated energy systems with agriculture offers the potential for flexible coordination of agricultural loads while agricultural loads are highly influenced by changes in the natural environment. In this context, this paper proposes a low-carbon and economic scheduling optimization method for agricultural integrated energy system (AIES), which comprehensively takes temperature, light intensity, and the coordination of agricultural loads into consideration. Firstly, solar and biomass resources are integrated through energy conversion equipment to support energy supply from both the electrical distribution network (EDN) and the gas network. At the same time, the modelling process of agricultural load is refined, which is divided into crop irrigation, greenhouse temperature control and residential consumption. The models of agricultural multi-energy complementary and energy storage equipment are established to achieve flexible conversion between different energy sources. In addition, the distributionally robust optimization (DRO) method based on multiple discrete scenarios is adopted to deal with the uncertainties arising from environmental condition fluctuations during the optimization process. Finally, the proposed model is tested on 4 various regions and 2 different seasons. Numerical results show that the proposed model can effectively enhance the economic and environmental performance of the AIES. [ABSTRACT FROM AUTHOR]

The transfer of energy-intensive projects to areas abundant in clean energy resources holds promise for optimizing the energy structure. After obtaining specific information on transferred projects of listed energy-intensive firms through search or phone contact, this paper innovatively constructs a three-dimensional panel containing 1,859,220 observations to empirically examine the attraction of clean energy to energy-intensive projects under the carbon intensity constraint policy (CICP). Our findings reveal that: (1) the CICP promotes the transfer of gray energy-intensive projects, leading to the transfer structure trending towards graying. (2) Furthermore, we observe a positive correlation between the proportion of thermal power in transfer-out areas and the outflow of gray energy-intensive projects. Conversely, areas with higher wind power and photovoltaics attract a greater inflow of gray energy-intensive projects. (3) Notably, clean energy predominantly attracts the inflow of gray projects rather than green projects. Our findings provide micro evidence and valuable insights into the transfer of energy-intensive industries, informing the design and implementation of future environmental policies for policymakers and stakeholders. [ABSTRACT FROM AUTHOR]

The integration of renewable energy sources (RES) based distributed energy resources (DER) lead to reduction in overall system inertia which causes large voltage and frequency fluctuations during any intermittency. This necessitates the integration of fast and robust controllers for low-inertia microgrids. Therefore, this paper proposes disturbance observer based control (DOBC) approach for frequency and voltage regulation of microgrid consisting of solar PV and diesel generator (DG) based hybrid microgrid under islanding situations. The DOBC is included as feed-forward control to the synchronous generator-based DG, which handles the real-time power mismatches and regulates frequency and voltage of islanded microgrid. To demonstrate the operational resilience of the designed controller under real-time uncertainties in PV and load, the controller has been evaluated under the most extreme uncertainty scenarios. The suggested controller has been implemented on a MATLAB/Simulink platform, and results have been validated utilising the real-time simulator OPAL-RT. In addition, the efficacy of the suggested control strategy has been evaluated in the presence of communication delays and noisy load circumstances. Results demonstrate the controller's dynamic performance in regulating the frequency and voltage for low-inertia microgrids. Finally, the proposed control technique has been executed on laboratory-scale microgrid to demonstrate the potential of developed controller. • Robust auxiliary DOBC for frequency & voltage regulation of PV-Diesel Microgrid. • Robust handling of real-time generation & load uncertainty through polyhedral sets. • Performance verification in presence of communication delay & noisy load conditions. • Real-time testing on OPAL-RT & hardware implementation on lab-scale microgrid setup. [ABSTRACT FROM AUTHOR]

The "virtual" pump without power supply is a potential replacement for the electrically-driven pump in the conventional Organic Rankine Cycle (ORC) system. In this paper, a pumpless module and a 10 kW ORC system are designed and constructed, and the optimization for the system control method is studied with the performance evaluation of the pumpless module. The experimental results show that the generated power fluctuates periodically with applying the pumpless module. There exists an optimal liquid level range of (280–340) mm in a pumping cycle to stabilize the output power near the peak. By optimizing the input vapor flowrate, pressure balance time, and upper and lower limits of the liquid level of the pumpless module, the liquid flowrate and the average power generation can reach 1.25 kg/s and 11.76 kW respectively. In addition, the heat consumption and the equivalent power consumption of the pumpless module are analyzed. The heat consumption as a percentage of the total input heat increases from 4.2% to 14.7% as the heat source temperature increases from 90 °C to 130 °C, and its equivalent power consumption can save 36.1% at 90 °C compared to the electrically-driven pump while consumed 7.8% more than the electrically-driven pump at 130 °C. • A pumpless module is proposed and applied to an Organic Rankine Cycle system. • An optimal liquid level interval of (280–340) mm is found for the peak flowrate. • The largest average flowrate and power are 1.25 kg/s and 11.76 kW, respectively. • The pumpless module can saves 36.1% power compared to the conventional pump. [ABSTRACT FROM AUTHOR]

Abstract Although hydropower and thermal power constitute the two pillars of China's power supply, the relationship between them has always been a controversial topic. Based on the panel data of China's provincial level covering the period 1991–2015, this paper tried to reveal the relationship between hydropower and thermal power under the framework of autoregressive distributive lag (ARDL) model. Taking the panel unit root and panel cointegration tests as the premise, the PMG estimators implemented under the maximum likelihood method provide unbiased results for this paper. Collectively, In the long run, China's hydropower and thermal power complement each other in ensuring a stable power supply, whereas in the short run, they are competitive to a certain extent, even if factors such as precipitation, grid infrastructure and economic conditions are taken into account. The Granger causality test further reveals the one-way relationship between hydropower and thermal power in short run. That is, thermal power is dominant while hydropower is subordinate and passive, giving an empirical interpretation for the specific phenomenon that discarded water from hydropower plants in China during seasonal water-rich period which has been seriously concerned by policymakers and researchers and appeal for impartial dispatching mechanism. Highlights • Cointegration exists between hydropower and thermal power. • The PMG estimator is employed for panel ECM. • In long run, a 1% increase of thermal power increases 0.5% of hydropower. • The short-term structure exhibits dominant thermal power and subordinate hydropower. [ABSTRACT FROM AUTHOR]

This paper evaluates the influence of atmospheric stability and topography on wind turbine performance and wake properties in complex terrain. To assess atmospheric stability effects on wind turbine performance, an equivalent wind speed calculated with the power output and the manufacture power curve is proposed and calibrated with the mast hub-height wind speed. After estimating the thrust coefficient and turbulence dissipation, this paper examines wind turbine performance curves and wake profiles segregated by atmospheric stability. Results show that the equivalent wind speed at a given mast wind speed can increase by 2% under stable conditions and decrease by 5% under unstable conditions as compared with that under neutral conditions, yielding about 16% reductions of power output and thrust coefficient from stable conditions to unstable conditions. Due to the lower thrust coefficient and the enhanced turbulence, the wind turbine wakes are found to recover faster under unstable conditions than under other stability conditions. Differences in wind turbine performance and asymmetric wake profiles due to topographic effects are also observed. Results suggest that atmospheric stability and topography have significant influences on wind turbine performance and wake properties. Considering effects of atmospheric stability and topography will benefit the wind resource assessment in complex terrain. [ABSTRACT FROM AUTHOR]

The power output obtained from the hydrokinetic renewable system fluctuates with changes in weather conditions, which could cause adverse effects on the voltage, frequency and stability of the electrical grid. In this article, an evaluation of power smoothing is performed for a renewable hydrokinetic on grid system using a supercapacitor. The power fluctuations are mitigated and smoothed by the proposed energy control and supplied to the utility grid and household load. Moreover, this paper studies the impact of the temporal resolution of data sampling with respect to the self-consumption of prosumers under technical, economic and environmental parameters using Matlab/Simulink software. The simulation results show that the fluctuations of the hydrokinetic turbine output power can be significantly mitigated, using the supercapacitor based storage system for different temporal resolutions reducing up to 90% of power peaks and power fluctuations produced by the hydrokinetic turbine and the load. Besides, the use of supercapacitors allows increasing the self-consumption of prosumers up to 17.27% for time resolutions of 1 min. Finally, the proposed control reduces up to 0.54 kgCO 2 /day at cost of energy 0.15 USD/kWh. [Display omitted] [ABSTRACT FROM AUTHOR]

Ocean thermal energy conversion (OTEC) provides a feasible solution for sustainable and stable power supply in remote islands. In this paper, a thermodynamic model of the OTEC system is developed to study the dynamic response of power output and superheating degree to manipulated variables. Afterward, a control strategy of load following for the island OTEC system is proposed. Finally, two controllers, MPC and PI, are designed and compared under fast and slow load changes as well as disturbance rejection test. The results indicate that the power output of OTEC system is sensitive to the speed of working-fluid pump, reaching the adjustment range of 14.7 kW when the nominal speed decreases by 30%. In addition, model predictive control (MPC) shows better performance in both rapid and slow load-change modes. Especially, in the rapid load-change mode, the MPC controller could always keep the evaporator outlet superheating in the range of 2–4.5 °C, while the PI controller may introduce no superheat that may cause liquid impact. Both MPC and PI controller can stabilize the power output at the set point under one day's measured disturbance, while MPC controller makes the superheating degree of evaporator outlet within smaller temperature fluctuations (<0.2 °C). [ABSTRACT FROM AUTHOR]

Renewable energy integration becomes an important criterion for the sustainable generation of electrical power. The high introduction of wind power plants into the power system leads to some inconveniences in the power system operators' work due to the unpredictable and variable nature of the wind speed and the power generated by wind farms. Even though the power generated at the wind power plants is not regulated by the system operator, the accurate predicting of the wind speed and the angle of its direction could solve such problems leading to improving the reliability of power supply systems. This paper considers the prediction of both the speed and direction of wind flows for the Far East coast. It is proposed to use autoregression based on the fuzzy systems concept. The goal of this study is to find a regression model that satisfies all observable fuzzy data within the specified optimality criterion. Thus, the regression coefficients are fuzzy numbers that can be expressed as interval numbers with membership values. As result, the electric power generated by wind power plants could provide additional energy accumulation function, if the wind flow velocity fluctuations will be considered. • A novel predicting method of wind speed was proposed based on a fuzzy regression. • The developed method allows assessing the maximum power output of a wind turbine. • The obtained computation results showed acceptable accuracy 3 h ahead. • The consideration of the wind flow velocity fluctuations provides additional energy accumulation in the wind power plants. • The proposed method allows to increase the reliability of the power supply. [ABSTRACT FROM AUTHOR]

Although renewable energy has been emphasized to mitigate carbon emissions, energy policies may require rearrangement. This paper aims to suggest the possibility of needs in energy policy rearrangement by revealing if the mitigation impact of the renewable energy supply has been diminished with a case study on Organization for Economic Cooperation and Development (OECD) countries. Adopting the idea of the environmental Kuznets curve hypothesis, the study investigates the nonlinear relationship between the renewable energy supply and carbon emissions. We collected the longest panel data possible for 34 OECD countries from 1971 to 2019. While the cointegrating equation results suggest that renewable energy has contributed to carbon mitigation, nonlinear estimation and quantile regression propose that the marginal mitigation impact from renewable energy might be weakening. 1% increase in renewable energy supply and the share of renewable in energy mix has mitigated carbon emissions by 0.134% and 1.260%, respectively. The empirical results insist that policymakers discover alternatives to decarbonize the energy sector, other than renewable energy expansion. Options to achieve carbon neutrality include heat expansion via unused heat, that is, national energy system innovation towards wasted energy utilization. [ABSTRACT FROM AUTHOR]

Renewable energy-based mini-grids have become increasingly popular over the last two decades. They have become crucial for increasing electricity access in developing countries, particularly in more remote locations. However, while access to such services can significantly contribute to socio-economic development, the functionality of mini-grid schemes is often poor. Many attributes of off-grid energy projects that contribute to sustainability have been considered within the literature. However, there has been minimal integration of these attributes across the different aspects of sustainability. Furthermore, the interaction between the sustainability dimensions, and the relative importance of these project attributes driving the sustainable performance of such mini-grids have been under-discussed. In this paper we use Partial Least Squares-Structural Equation Modelling (PLS-SEM) and analyse a quantitative dataset obtained from a survey of 175 micro-hydro projects. A theoretical framework of attributes that contribute to the sustainable performance of mini-grid projects is presented, and the empirical analysis provides evidence supporting 14 hypothesised relationships between 10 project attributes and five sustainability dimensions. The results provide insight into how remote mini-grid projects, with stability of power supply and demand, can achieve a self-reinforcing economic cycle in the village, and thus, maintain economically and environmentally sustainable outcomes. [ABSTRACT FROM AUTHOR]

This paper proposes the operation of "U" type heat exchangers to harness the remaining heat/geothermal energy in a non-producing well and use it in an absorption cooling system. The operational proposals are obtained with a previously validated numerical model that allows modifying geometric and functional parameters of the heat exchanger, in addition to considering information from the well and the absorption cooling system to estimate the temperature of the fluid along the tubes. By taking information from the well, such as the geothermal gradient, the thickness of each stratum, and its thermophysical properties, in addition to the requirements of the absorption cooling system, it is possible to reach more realistic results compared to omitting or assuming any information. In total, 31 different simulations were carried out in which one of the following five parameters was modified: fluid velocity, diameter and total length of the heat exchanger, thickness and length of the insulating material. As a result, 4 different operation proposals are obtained that meet the requirements of the absorption cooling system. In this way, it is possible to combine in a novel way the properties of the well, the characteristics of the absorption cooling system, and the operating parameters of the "U" type heat exchanger. [Display omitted] [ABSTRACT FROM AUTHOR]