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The data imbalance problem extensively exists in wind turbine fault diagnosis, resulting in the compromise between learning attention to majority and minority classes. In this paper, a deep neural network method is proposed to resolve the mentioned problem. Specifically, convolutional and recurrent neural networks are designed to extract spatial and temporal features within supervisory control and data acquisition (SCADA) measurements. To improve the reliability of fault diagnosis results by collective decision, a coarse learner and multiple fine learners are established. With the consideration of data imbalance and learning diversity, fault-related information can be revealed. Moreover, a learner selection scheme is designed to ensure high computational efficiency. The effectiveness of the proposed method is demonstrated by experiments based on simulated data and real-world SCADA measurements from a wind farm. Experimental results show that the accuracy in identifying health conditions can be improved by the proposed method regardless of the data imbalance. On the two datasets, the proposed method outperforms four benchmark approaches as the learning attention to all classes can be enhanced. Therefore, the proposed method is a promising solution to wind turbine fault diagnosis. [ABSTRACT FROM AUTHOR]

In this paper a novel embedded system for remote monitoring and fault diagnosis of photovoltaic systems is introduced. The idea is to embed machine leaning algorithms into a low-cost edge device for real-time deployment. First, an artificial neural network is developed to detect faults. Then an effective stacking ensemble learning algorithm is developed to classify the nature of the fault. The method performance is evaluated through common error metrics such as RMSE, MAE, MAPE, r and confusion matrix. Additional algorithms are also embedded into the edge device in order to remotely control the photovoltaic array parameters. Users can be notified by email and SMS about the state of their photovoltaic array. The Blynk IoT platform is used to monitor remotely the photovoltaic array parameters. The experimental results demonstrate the ability of the proposed embedded system to diagnose and monitor the photovoltaic array with a good accuracy. • An embedded system for fault diagnosis of PV arrays was introduced. • An embedded stacking ensemble learning classifier is integrated into a microprocessor. • Experimental results showed the feasibility of the proposed embedded system. • A smart remote monitoring PV system was designed using the IoT technique. [ABSTRACT FROM AUTHOR]

Wave energy converters (WEC) use indirect drive hydraulic or turbine-type power take-off (PTO) mechanisms which consist of many moving parts, creating mechanical complexity and increasing the installation and maintenance costs. Linear generator-based direct drive wave energy converters could be a solution to overcome this problem, but the efficiency of the single conventional linear generator is not high enough, and it cannot work satisfactorily in the low-frequency range. In this paper, a novel dumbbell-shaped flux-switching linear generator has been proposed and studied as a power take-off unit for ocean wave energy conversion. The linear generator has a dumbbell-shaped stator, and the design is ameliorated by placing the permanent magnet rings of longitudinally alternating magnetic pole directions in the slots of its stator outer surface and is separated by thin wall steel ring shoulders. The linear generator also has a dumbbell-shaped translator. The stator is hollow where the translator slides inside axially inducing current in the coil. A long permanent magnet is inserted inside the hollow steel dumbbell core of the translator and a copper coil is wound around the outer surface of the moving translator core. The addition of permanent magnets on the outer slots of the stator is found to increase the output power significantly. To facilitate the investigation, the modified generator design has been compared to the conventional linear permanent magnet generator for their performances using the finite element method, as both machines are different in their structures. The results show that the double dumbbell-shaped flux-switching linear generator gives higher power output, magnetic flux density, branch current, and induced voltage. The double dumbbell-shaped flux-switching linear generator is then placed in a cylindrical buoy and investigated in a wave energy converter in the ocean environment. The hydrodynamic response of the cylindrical buoy has been investigated through ANSYS AQWA. The dynamic differential equations of the wave energy converter have been developed and solved for regular waves using Matlab codes. The peak output voltage, power, and the relative displacement of the linear generator translator with respect to the stator fixed with the buoy have been calculated through the Fourier Transform in the frequency domain using a Matlab code and through numerical integrations in the time domain using a Matlab Simulink code. The results in the time and frequency domains are compared and verified with each other. The relative displacement between the translator and stator buoy has been used as motion input of the ANSYS Maxwell simulation model, and the output voltage results of the ANSYS Maxwell simulation model have been compared and verified with those of the Matlab simulation models. The linear generator design in the wave energy converter under the regular wave excitation is further optimized for the maximum ratio of the peak output power to peak cogging force using the central composite design-based response surface method (RSM). The ANOVA analysis is used to validate the response surface model where its R 2 coefficient of 99.93% has indicated an excellent fit. The methods and results differ from those presented in previous studies. [ABSTRACT FROM AUTHOR]

A tidal turbine can benefit from exquisitely designed morphing blades with a flexible trailing edge by mitigating up to 90% of the load fluctuation in harsh ocean environments, which reduces the overall cost of tidal energy. However, existing fluid–structure interaction (FSI) methods of resolving flow-induced deformation of the blades is computationally expensive, which poses an important challenge to effective morphing blade design. This paper presents a novel static FSI tool based on deep learning to cost-efficiently analyze the fluid–structure coupling of a hydrofoil. Specifically, adopting a convolutional neural network (CNN) to predict the fluid force and finite element method (FEM) to solve the solid structure response, a new CNN-FEM framework with an iterative scheme for solving the FSI problem is developed to achieve equilibrium between the fluid and structural forces. The new framework is used to predict the elastic deformation of the flexible blade section of the hydrofoil to demonstrate its effectiveness in the FSI evaluation. Comparison of the results to those produced by commercially developed software (i.e., Ansys Workbench) shows that this method yields extremely close prediction results of average equivalent stress and an accuracy of more than 92%. Moreover, it is 100 times more computationally efficient than the commercial Ansys Workbench software, requiring less than 3s for one-way FSI calculation. Taking advantage of this cost-effectiveness, the CNN-FEM can be used to achieve the accurate prediction of the deformation characteristics of the flexible hydrofoil under various flow scenarios that lay a foundation for advanced morphing blade design in the future. [ABSTRACT FROM AUTHOR]

The poor stability of metal-organic frameworks (MOFs) limits their practical applications in many fields. Zeolitic imidazolate frameworks (ZIF-8) has been widely studied as an enzyme immobilization carrier. In this paper, the stability of ZIF-8-immobilized lipase in methanolysis for biodiesel production was studied. Fatty acids as conventional substances involved in lipase-mediated natural acylation were found to destroy the structure of ZIF-8 through ligand exchange mechanism. A new MOF was successfully constructed by using phthalic acid (pKa much smaller than 2-methylimidazole) as the exchange ligand. This novel MOF (abbreviated as LeZIF-8-PA X, X represents reaction hours) had dual stability in water and even in pure oleic acid. Lipase immobilized on LeZIF-8-PA 0.5 showed higher specific activity. FTIR analysis showed that enzyme molecule immobilized on Le-ZIF-8-PA 0.5 had higher conformational flexibility than that with ZIF-8 as the carrier. When applied to methanolysis for biodiesel production, ET 2.0/LeZIF-8-PA 0.5 maintained intact morphology while ET 2.0/ZIF-8 almost lost its original morphology, with enzyme activity of 81.5% and 60.2% retained respectively after 5 batch reactions. This work is anticipated to provide new ideas for constructing stable MOFs and promoting the application of MOFs-immobilized enzymes in many chemical and pharmaceutical industrial processes. [Display omitted] [ABSTRACT FROM AUTHOR]

Accurate and credible operation data sets of wind and solar power stations are the basis of many research works. However, such data sets often contain abnormal data due to failure, maintenance, energy curtailment, etc. The existing identification methods fail to consider the operating characteristics of power stations and the forms of abnormal data, resulting in low identification ability. Therefore, an adaptive identification method of abnormal data (AIMAD) in the wind and solar power stations is proposed in this paper, including the bidirectional one-sided quartile method and double DBSCAN method to deal with unevenly distributed abnormal data; the improved K-means clustering method based on the distance between the cluster center and benchmark power curve to process the abnormal data that are densely accumulated and closely connected with normal data in the power scatter diagram. The proposed method can adjust adaptively according to the forms of abnormal data to realize accurate identification and has strong robustness for power stations. The operation data of 30 wind farms and 8 solar plants in China are taken as examples to verify the effectiveness and superiority of the proposed method. • BOQ and d-DBSCAN are proposed to deal with unevenly distributed abnormal data. • Improved K-means method is proposed for identifying stacked abnormal data. • AIMAD is proposed to realize accurate identification of abnormal data. • Operation data in 38 stations are used to verify the effectiveness of AIMAD. [ABSTRACT FROM AUTHOR]

As the power demand increases, photovoltaic (PV) energy evolves with time, and besides the traditional ground-mounted and roof-based PV systems, floating photovoltaic (FPV) systems have gained popularity due to higher efficiency from lower module temperatures and water evaporation reductions. This paper estimates and compares the temperature of the floating PV module using thermal, empirical, and computational fluid dynamics (CFD) models. The dynamic thermal model considers a three-level energy-balance equation for the FPV module. From that, a simplified thermal model has been developed, which requires fewer parameters and is easier to estimate the module temperature. Secondly, the least squares regression was used to generate the empirical model, resulting in the smallest possible root mean square error when comparing the observed and predicted values. Finally, the FPV system has been developed in the COMSOL environment for CFD analysis using the same heat transfer method. The estimated results from the models were compared with the actual data collected from a Brazilian site and the existing FPV and ground-mounted temperature models. The RMSE performance of the FPV models was comparable to that of the data obtained from an installed FPV system and performed much better than other similar FPV models and their ground-based counterparts. [ABSTRACT FROM AUTHOR]

Offshore wind is becoming the way forward for green energy harnessing worldwide. However, frequent typhoons are a major constraint for the development of offshore wind power for some regions in Asia and North America. Typhoons may pose a huge challenge to offshore wind farm development in southern China. In this paper, a fully-coupled analysis was carried out for a 10 MW large-scale monopile offshore wind turbine (OWT) using SIMO-Riflex-Aerodyn (SRA) code. The response characteristics of the OWTs in different typhoon regions are investigated based on the measured typhoon conditions in China. The effect of aerodynamic damping on the response and the load effect is analyzed in detail. Two different distribution methods are used to statistically extrapolate the response value and get the short-term extreme response. Cumulative linear fatigue damage is evaluated by the rain-flow counting method to explore the possible failure modes of large wind turbines during typhoons. The results show that aerodynamic loads play an important role in large monopile OWTs during high wind speeds in parked conditions. The extreme response and fatigue analyses from this study indicate that fatigue is a dominant failure mode for the large OWT tower during typhoons, while buckling is unlikely. • The wind field at the wind turbine was analyzed when the typhoon passed by. • The response of large monopile wind turbine in each typhoon region of is analyzed. • Aerodynamic damping play an important role for the structural response of parked monopile OWT. • The extreme moments at the tower base follows the Gumbel distribution and lognormal distribution. • The cumulative fatigue damage during different typhoon stages is evaluated. [ABSTRACT FROM AUTHOR]

Waste terpenes from paper industry, pine resin tapping or citric industry are abundant feedstocks that can be used as components in diesel blends. However, terpenes such as turpentine or orange oil are highly reactive, tend to form deposits and show high sooting tendency. These drawbacks can be solved with hydrogenation, which reduces the degree of unsaturation of the molecule and thus, the formation of soot. In this work, blends at 20 vol % of hydrogenated turpentine and hydrogenated orange oil in diesel fuel were tested in a Euro 6 diesel engine following Worldwide harmonized Light-duty Test Cycle (WLTC). Engine performance, gaseous and particle matter emissions and combustion analysis from these blends were compared with those from diesel fuel. Engine performance was similar for all fuels, with slight differences in equivalence ratio and exhaust gas recirculation (EGR) rate. CO and HC emissions were increased whereas NOx emissions remained constant when blends were tested, with respect to diesel. Sooting tendency was improved since particle mass emissions were reduced despite the particle number emissions were similar to those from diesel. Combustion was quite similar between all fuels and only ignition delay was longer and combustion velocity higher for blends in comparison with diesel. • Blends with 20% hydrogenated terpenes can be used without penalty in emissions. • HC and CO emissions were higher due to high volatility of blends. • Nitrogen oxides emissions were similar to diesel. • Particle mass emissions were reduced despite increasing in number. • Molecular cycles greatly affect particle nucleation. [ABSTRACT FROM AUTHOR]

Deploying shallow geothermal solutions is critical for meeting energy demands while supporting decarbonisation targets. In densely populated areas, drilling large numbers of boreholes may lead to thermal interactions between closely located borehole heat exchangers. This paper presents a novel method termed the infinite borehole field model to estimate the technical shallow geothermal potential, especially in urban regions. The thermal interactions between boreholes are considered using finite element models simulating the operation of a single borehole in a larger field. Mathematical optimisation is used to find the amount of thermal energy that can be annually extracted while keeping the borehole wall temperature above freezing point of water. The method considers thermogeological details of geological formations including downward-increasing ground temperature, geothermal heat flux, thermal conductivity, heat capacity, porosity, density, and advective heat transfer. Results of our case study indicate that 100 m deep thermally independent boreholes can produce 14.20 MWh/a for 50 years on average. However, boreholes in an infinite borehole field spaced 20 m apart produce 7.80 MWh/a. A further investigation including advective heat transfer indicated that high velocity groundwater flow can significantly enhance borehole yield. Our method provides a generalised approach which can be beneficial prior to detailed site investigations. [ABSTRACT FROM AUTHOR]

With the increasing penetration of renewable energy, the traditional energy storage operation based on individual framework —users own and operate independently mode may become impracticable due to conflicting interests, insufficient utilization, and poor interoperability. Riding on the wave of the proliferation of sharing economy, storage energy sharing expands the existing storage energy without requiring costly and time-consuming infrastructure investments. However, the development path of shared energy storage (SES) mode is not clear due to the asymmetric decision-making of the owners of energy storage systems under bounded rationality. In this paper, the diffusion of the business model of SES among multiple renewable energy stations (the owners, RES) and its key factors are analyzed based on the evolutionary game. The goal is to maximize social welfare and ensure the continuous growth of the sharing market. The numerical simulation is carried out based on the data from northwest China to interpret the development path. The result shows that, in renewable energy cluster the stations with intermittent output or with the higher prediction accuracy are more willing to participate in sharing. The energy storage sharing mode fails when the energy storage capacity ratio of RES is less than 10%. While the high-level ratio (more than 30%) is not conducive to the diffusion of the sharing model in RESs with low power generation prediction accuracy. [Display omitted] [ABSTRACT FROM AUTHOR]

In this paper, the electrical and thermal performance of hybrid photovoltaic (PV/T) system works with an active cooling open water cycle has been improved. Experimental tests were conducted on the (PV/T) of two cases (with and without reflectors) and the reference photovoltaic (PV) in Iraq - Samarra located at latitude (34.26°N) and longitude (43.89 °C). Several experiments were carried out during June 2021 with a (0.014 kg/s) mass flow rate. Results manifested that the maximum daily electrical, thermal and overall PV/T collector efficiency with reflectors were 10.2%, 82.3%, 92.5%, respectively, with the highest improvement in the electrical power (EP) of 69.4%. This technique has proven its effectiveness in the hot climate that Iraq enjoys (suffers), and that the water jets played their role in decreasing the temperature of the hybrid panel despite the increase in the concentration of solar radiation throughout the presence of reflectors. [ABSTRACT FROM AUTHOR]

This paper studies the heat load-carrying capacity characteristics of a surface water body integrated with stagnant water and river water as a heat source for water source heat pumps in winter. In the cold climate, the influence of each variable on the surface water temperature was simulated and analyzed. The results showed that the solar radiation intensity, the air temperature at the water surface and the heat pump extraction time are important factors affecting the heat load-carrying capacity of surface water body. At a simulated solar radiation intensity of 500 W/m2, the water body provided the heat pump with 25 kg/s of extracted water to keep the surface water body temperature largely stable. The heat pump extraction time affects the water extraction flow rate. The flow rate for 24 h of heat extraction per day was only 0.4 times that of 10 h of heat extraction. The replenishment flow rate can change the rate of water temperature variation and the heat load-carrying capacity of the water body. When the solar radiation intensity was 0W/m2, the average temperature drop of the water body decreased from 0.23 °C to 0.15 °C by increasing the replenishment water flow rate from 0 to 10 kg/s. [ABSTRACT FROM AUTHOR]

Many subarctic communities rely entirely on fossil fuels for their energy needs. Solar-assisted ground-coupled heat pumps (SAGCHP) can be a solution to integrate renewable energy sources into their energy portfolios. However, it is currently unknown how such systems could operate in the context of the high North (cold ground, extreme mismatch between insolation and heating need, electricity from diesel). The objective of the paper is to develop a detailed model of a SAGCHP heating a house in Nunavik (Quebec, Canada) in order to gain a better understanding of its potential and limitations. The solar assistance is provided by PVs. Simulations with and without electric storage (batteries) were run. A complex tradeoff between four different modes of operation was obtained depending on the conditions of the system at each time step. For the test case, results show that the ground experiences a weak long-term thermal depletion partly compensated solar energy, but that a significant portion of the PV power production is preferably used by the compressor or stored in batteries rather than stored in the ground as heat. Over ten years, the SAGCHP system reduced fuel consumption respectively by 38.2% (without a battery) and 59.1% (with a battery). [ABSTRACT FROM AUTHOR]

Harvesting energy from the sun is a promising technology to resolve the ongoing energy crisis. Solar photovoltaic (PV) and photovoltaic/thermal (PV/T) systems are mainstream solar energy conversion technologies that enable duple functions to obtain both electrical and thermal energy. However, in practice, emerging problems (uneven temperature distribution, limited cooling effect, freezing issues, high initial costs, etc.) have hindered the development and progress of these technologies. To overcome the aforementioned barriers, a heat pipe was introduced as an effective heat transfer device with passive operation characteristics. The assimilation of cutting-edge thermoelectric (TE), phase change material (PCM) and the development of integrated photovoltaic (BIPV), heat pump, and nanotechnologies have also been explored to achieve higher overall efficiency. This paper focuses on the integration of various heat pipes with solar PV systems and innovative technologies from historical development and recent advancements. In addition, the major observations and challenges are highlighted, and the prospects for future development are corroborated. This work is dedicated to opening new horizons and providing suggestions in this research field, enabling in-depth and broad exploration. • Heat pipes based solar photovoltaic and photovoltaic/thermal systems are reviewed. • The combination of innovative technologies in these systems is summarized. • Using heat pipes in these systems leads to enhanced performance. • Challenges and future suggestions of such technologies are discussed. [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]

Air source heat pump is recognized as an effective environmental protection and energy-saving technology. The heating temperature lift is one of the key factors affecting the performance of heat pump systems. In this paper, an in-depth quantitative thermodynamic comparison of cascade heat pump, recuperative heat pump and CO 2 heat pump for direct-heating and space heating was conducted. Aspen HYSYS was used to invoke advanced genetic algorithm in MATLAB to optimize the system parameters. The temperature matching in heat exchangers was employed to reveal the essence of the performances of different heat pump systems. The recuperative heat pump is more suitable for direct-heating with the temperature lift 60 °C, and its COP is up to 4.81 at the ambient temperature of 20 °C. The cascade heat pump performs best in space heating with the maximum COP of 2.47. The exergoeconomic factor of the compressor is less than 7%, which illustrated that the investment in compressor should be increased to further improve the system efficiency. The annual CO 2 and SO 2 lowest emissions is 4431 kg and 130 kg of recuperative heat pump for direct-heating, and the cascade heat pump has the lowest annual 4234 kg CO 2 and 127 kg SO 2 emissions for space heating. [ABSTRACT FROM AUTHOR]

Various studies have assessed the energy performance alterations affected by the novel technology of Building-Integrated Photovoltaic in Double-Skin Facades (BIPV-DSF), while lighting performance tied to the BIPV-DSF has not received much attention. This paper provides numerical modelling to assess the effect of BIPV-DSF on both indoor visual condition and energy consumption for an office module under a typical climate in the United Kingdom. The proposed study was focused on the comparisons between a reference case (a DSF office module with both layers using clear double glazing) and a design case of the same office module with BIPV-DSF using semi-transparent Amorphous Silicon PV glazing. Results show a significant drop in maximum daylight illuminance of 73% by configuring the BIPV-DSF with reference to the regular DSF. It was also reported the resultant average and minimum daylight factors (0.65% and 0.00%) were not able to meet indoor visual comfort requirements for office environments. Furthermore, it was found that the use of BIPV-DSF resulted in a net increase of 8% in building energy consumption over the reference DSF. Therefore, it is concluded that in the present context the BIPV-DSF is not viable for a commercial installation under the UK's climate conditions. [ABSTRACT FROM AUTHOR]

By considering the significant role economic growth has played in environmental function between 1990 and 2019, this paper examines the relationships between renewable energy development, trade openness, and institutional quality in the development of green finance in South Asian countries. The effectiveness of institutions and trade transparency are factors in green finance. We use a panel data model to ascertain the cointegration among the variables. The study employs the OLS fixed pool method along with a quantile regression to assess the model and reveal that, although growth in renewable energy development and trade openness worsen the ecological environment, institutional quality and the use of renewable energy promotes green finance development. The findings indicate that trade openness and institutional quality have a positive link with green financing. Institutional quality drives the use of renewable energy, whereas gross domestic product (GDP) drives the environmental impact. In light of these findings, policymakers can put in place beneficial policies for renewable energy development as an economic instrument to minimize ecological footprints and enhance green finance development. • Trade openness. • Renewable energy development. • Green finance. • Institutional quality. [ABSTRACT FROM AUTHOR]

Although photovoltaic/thermal (PV/T) air collector has simple structure and strong pressure bearing capacity, there are problems such as low thermal efficiency, unstable output temperature, due to low heat transfer performance of air and fluctuating solar irradiation. To address the above issues, a concentrating photovoltaic/thermal air collector with phase change material and vacuum double-glazing (VDG-PCM-CPV/T) is proposed in this paper. The performance of VDG-PCM-CPV/T in three continuous days is studied and compared with the module with PCM and single-glazing (SG-PCM-CPV/T) and the module with single-glazing (SG-CPV/T) by establishing the mathematic model of the daytime and night. It is proven that VDG-PCM-CPV/T has certain advantages in alleviating the downward trend of air temperature caused by the decrease of solar irradiation, due to the constant temperature storage and heat release characteristics of PCM. At night, as the vacuum double-glazing has excellent heat preservation effect, the initial temperature of PCM in VDG-PCM-CPV/T is 5.00 °C higher than that of SG-PCM-CPV/T, enable VDG-PCM-CPV/T to obtain higher thermal efficiency in the next day. While, the electrical power of VDG-PCM-CPV/T is slightly lower than that of SG-PCM-CPV/T and SG-CPV/T. The exergy efficiency of VDG- PCM-CPV/T, SG-PCM-CPV/T and SG-CPV/T at peak is 1.70%, 1.10% and 2.00%, respectively. [ABSTRACT FROM AUTHOR]

To cooperate with new energy sources such as wind and solar, pumped storage units are required to frequently change conditions and operate under part loads, leading to the problem of violent pressure fluctuation and unit vibration. To meet this challenge, the next generation of pump-turbine runners will therefore have to be designed differently. The goal of this article is to construct a framework for broadening the operating range of pump-turbine to deep-part loads. In this study, a multi-objective optimization strategy for the runner with wider output range is suggested, wherein the blade control parameters, specifically the blade loading and blade lean angle, are optimized to enhance the efficiency, anti-cavitation, and stability of the pump-turbine runner. A runner with turbine output range of 40%–100% is optimized for a specific power station. Next, the impact of runner control parameters on runner performance is evaluated, and the runner geometric characteristics for different optimizing priorities such as the pump peak efficiency, cavitation performance, turbine rated efficiency, and turbine partial load efficiency, are concluded. The mutual restriction mechanism between the pump peak efficiency and cavitation performance of pump mode, as well as the turbine-rated efficiency and partial load efficiency of turbine mode, is revealed. The main contributions of this paper include putting forward an effective optimization design process for wide output pump-turbine, and pointing out the relationship between runner geometric characteristics and performance. The results indicate that the present approach can significantly improve the efficiency and stability of runners operating in deep-part loads. The blade loading pattern with hub section aft-loaded and shroud section fore-loaded, combined with negative blade lean angle, is recommended for such runners. Blades with a smaller wrap angle and lower arch are conducive to improving the pump peak efficiency and turbine-rated efficiency, while the opposite geometrical features are advantageous for improving the runner cavitation performance and efficiency performance under part load conditions. These findings can serve as an important guide for the development of runners with a wider output range. [ABSTRACT FROM AUTHOR]

The increasing penetration of renewable energies in power systems demands new services from renewable generation plants. System operators are concerned about system stability since renewable generators behave as constant power sources. Therefore, new requirements have been imposed to grid-following generators to improve their contribution to system stability acting as grid-supporting generators. Nevertheless, grid-supporting control can still compromise system stability for high penetration of renewables, and grid-forming control has arised to ensure proper operation. This paper proposes a novel grid-forming control scheme for doubly-fed induction generators, so they behave as real voltage sources. The proposed grid-forming control is based on the rotor flux orientation to a reference axis obtained from the emulation of the synchronous generator swing equation. The rotor flux is oriented to the reference axis by means of a flux controller that also controls the flux magnitude. The flux orientation in turn allows to control the doubly-fed induction generator torque, while the flux magnitude control allows to regulate the generator reactive power or terminal voltage. The proposed control system has been validated through a comprehensive real-time simulation with hardware in the loop, assessing its grid-forming capability. Moreover, small signal analysis has also been performed to assess system stability. [ABSTRACT FROM AUTHOR]

Sand erosion is usually severe for hydraulic turbine operated in sediment-laden river hydro-power plant. Continuous erosion and abrasion in hydro-turbine components not only deteriorate the turbine performance but also bring frequent maintenance work. Thus, special attentions should be paid to anti-erosion performance besides the efficiency and stability during the hydraulic design stage. In this paper, the performances of a prototype Francis turbine used for a high head heavy sediment power station were investigated by reducing the rotational speed and using splitter runner. The hydraulic performance, anti-erosion characteristics and cavitation performance were focused and analyzed. The results proved that the velocity in the runner can be effectively reduced by lower the rotational speed, but the rotational speed reduction was also limited by the efficiency and velocity near the guide vane. The splitter runner can significantly improve the disorder flow in runner by re-distributing the velocity field. The erosion resistance of guide vane can be improved by increasing the pitch diameter of the guide vane appropriately. 3100 h of operation after commissioning further confirmed the anti-erosion and stability performance of the designed Francis turbine. This research provide a good reference for the Francis turbine design operated in heavy sediment hydro-power plant. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to examine whether circular economy principles are applied in existing residential solar thermal systems, and to propose a pathway that will combine existing tools and methods for assessing life cycle data under proper design modifications and labelling options, to reach circular economy targets. The proposed holistic scheme covers various aspects (i.e., energy saving potential, environmental impacts, expected lifetime, recycling-reusing capabilities, use of advanced materials, and purchase cost) and comprises the implementation of eco-design principles based on life cycle assessment results and categorization of the final outcome via a circular economy modified label. Thus redesigned solar thermal systems will exhibit optimized characteristics being more lightweight and durable with minimized use of resources/waste and providing ease of disassembly of selected parts aiming for reuse options. • Examine if circular economy principles apply to residential solar thermal systems. • AsSessing LCA data under proper ED and EL options, to reach CE targets. • Use of LCA and EL in an ED implementation context in solar thermal systems. • Redesign solar thermal devices for optimized technical - environmental performance. [ABSTRACT FROM AUTHOR]

This paper studies the multi-objective control of transient process of hydropower plant with two turbines sharing one penstock under combined operating conditions (COCs). Firstly, the model of transient process of hydropower plant is presented. The illustration of four COCs is provided. Then, the multi-objective control strategy of transient process under COCs is designed. The decision variables and objective functions are selected. The control scheme and decision method are determined. Finally, the most favourable superposition time and the most unfavourable superposition time under COCs are determined. The results indicate that the objective function contains three objectives, i.e. spiral case outlet pressures, draft tube inlet pressures and rotational speeds of turbines. The most favourable superposition time under COC-1 can realize that the objectives reach control requirements simultaneously. The most favourable superposition time under COC-2 and the most unfavourable superposition time under COC-1 and COC-2 cannot realize that the objectives reach control requirements simultaneously, but can balance the objectives to the maximum extent. It is unnecessary to distinguish the most favourable superposition time and the most unfavourable superposition time strictly under COC-3. There is no the concepts of the most favourable superposition time and the most unfavourable superposition time under COC-4. [ABSTRACT FROM AUTHOR]

The lack of partnerships between biomass generating producers is one of the main barriers to efficient biogas production. Partnerships can help producers properly dispose of waste, assist in the supply of biodigesters, allow the union of properties with different potential biomass generators into clusters, and optimize operating costs. In this sense, new measures must be adopted with regard to the establishment of strategic partnerships between producers. Therefore, in this paper, we propose a new clustering algorithm, BiogasCluster , to decide the optimal number of clusters for generating a renewable energy community. To test the proposed algorithm's applicability, we implemented the algorithm in R language. Experiments with real databases showed that the BiogasCluster proved to be efficient in generating stable clusters for all considered scenarios. It was also found that the filters and criteria used in the proposed algorithm have not been used in previous studies. This study provides important guidance to creating strategic partnerships within bioenergy generation in addition to obtaining a preliminary assessment of the possibility of establishing clusters of rural properties with the aim of achieving energy security and adding value to their businesses. [ABSTRACT FROM AUTHOR]

The primary purpose of this paper is to evaluate the impacts of green finance on green energy deployment in China's tourism industry. To this end, the annual data over 1992–2021 through the ARDL (Autoregressive Distributed Lag) approach for the case of China are analyzed. The findings confirm that the issued green bonds positively impact the green efficiency of China's tourism industry in the long term. In contrast, the coefficient of issued green bonds is insignificant for the short-term approach. In addition, in the short and long term, the consumer price index also has a significant adverse effect on the green efficiency of China's tourism industry. The recommended practical policies are improving executive regulations and transparent market information, implementing green fiscal policies, green construction in hotels and tourist accommodations, green globalization, operational phases of innovation, adaptation, and stabilization (IAS), and eco-tourism regionalism. • Green bonds have a positive impact on the green efficiency of China's tourism. • Consumer price index has a negative effect on green efficiency of China's tourism. • Economic globalization index has a significant coefficient on green efficiency. [ABSTRACT FROM AUTHOR]

This paper investigates the validity of the environmental Kuznets curve (EKC) hypothesis for the G7 group of countries through the ecological footprint and its components (namely built-up land, carbon, cropland, fishing grounds, forest land, and grazing land). Most previous contributions rely on CO 2 emissions as a measure of environmental damage, whereas using disaggregated ecological footprint allows us to consider resource consumption and waste generation compared to nature's resource generation and waste absorption. The empirical application is based on a panel data analysis for G7 countries from 1980 to 2018. The results indicate that the EKC hypothesis is confirmed for the ecological footprint overall, but the impact of GDP growth is unequal across its components. Long-term elasticities point to renewable energy generation significantly improving environmental sustainability. Globalization also decreases pollution indicators, while economic complexity seems to contribute to environmental degradation. [ABSTRACT FROM AUTHOR]

This paper examines the neighbourhood-level spatial determinants of residential solar photovoltaic (PV) adoption in the Netherlands. We investigate the roles of place-specificities and spatial interaction effects by utilising high-resolution spatial data on 13,205 Dutch neighbourhoods. Unlike other studies, we use impact measures on the basis of a spatial Durbin model to distinguish between direct and indirect effects of the spatial determinants. We find significant neighbourhood-level spatial interaction effects in residential solar PV adoption. Where there is a spatial dependence, household income, property value, population density, housing type and household type are among the factors that influence residential solar PV adoption. • Spatial factors that influence residential solar photovoltaic (PV) adoption are identified. • Spatial econometric models are applied using high-resolution spatial data on 13,205 Dutch neighbourhoods. • Direct and indirect effects of the spatial determinants are distinguished. • Significant spatial interaction effects are identified. • Neighbourhood-level spatial differences influence solar PV adoption. [ABSTRACT FROM AUTHOR]

The thermal runaway (TR) of lithium-ion batteries (LIBs) has become a potential danger of serious fire and explosion, which threatens people's life and property safety. Therefore, the timely and effective methods are urgently needed to suppress this hazardous process. Therefore, it is of great significance to develop efficient TR inhibitors. Liquid nitrogen (LN) has been widely concerned as an efficient and environmentally friendly fire extinguishing medium. In this paper, TR device of LIBs in open space is investigated, and the effectiveness of LN in restraining the TR of LIBs is studied under different heating power, spray direction, state of charge (SOC) and spray time. The results show that LN has excellent inhibition effect on TR, and the mean cooling rate of LIBs surface temperature decreases with the increase of heating power. Vertical spraying is better than horizontal spraying for cooling and extinguishing. The average cooling rate of battery surface temperature decreases with the increase of SOC. The average cooling rate of battery surface temperature decreases with the shortening of the time. [ABSTRACT FROM AUTHOR]

The array configurations have gained a higher prominence and application in the solar PV system for reducing power losses during partial shading. However, additional wires can increase the vulnerability of these configurations to electrical faults affecting the performance and lifespan of the modules. Hence, this paper investigates the reliability of these configurations under various electrical faults in the MATLAB and prototype experiment platforms. Additionally, a powerline communication-based PV monitoring system along with fault detection through optimal sensors placement and a user-friendly web application are developed to monitor the performance, detect the presence of the fault and access the data during normal and faulty operation of the PV array respectively. The investigation is conducted for 3x3 array configurations, compared using power curves, and electrical parameters, and the performance along with detection is studied using the real-time data from the proposed monitoring system under normal and faulty conditions. From the analysis, the series-parallel has a higher average tolerance of 59.48% and 48.38% than honeycomb (54.16% and 47.43%), bridge-linked (52.56% and 43.96%), and total-cross-tied (53.66% and 37.48%). The proposed low-cost PV monitoring system has effectively monitored the system performance and is capable of detecting various types of faults in PV arrays and notifying the system with an alarm for proper diagnosis. [ABSTRACT FROM AUTHOR]

In this paper, a near-field thermophotovoltaic (TPV) system with a dual TPV cell design is considered and studied numerically. The fluctuational electrodynamics accompanied by the dyadic Green's function are utilized for calculating the radiation heat flux. The generated photocurrent and the conversion efficiency are obtained by solving the photon-coupled charge transport equations. It was discovered that the addition of the second TPV cell to the system, increases the generated photocurrent of the system due to the absorption of the low-energy photons and generation of the electron-hole pairs. By increasing the gap size between the emitter and Si TPV cell from 50 nm to 1 μm, the generated photocurrent decreases because of the reduction of the near-field thermal radiation effects. Finally, the tandem nano-gap TPV system shows higher conversion efficiency compared with the single Si TPV cell for different values of the vacuum gaps, and the gap size of d 1 = 200 nm is the optimum gap size due to the improvement of the conversion efficiency of the system. [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]

Over the past decades, the penetration of renewable energy sources is growing at a significant pace on a global scale. In parallel, the utilization of renewables could possibly act as the basis for the transition to a Circular Economy, which aims to reduce the use of finite resources. Compared to other European countries, Greece has achieved a significant share of renewables in its' energy mix and in parallel promotes various policies aiming to accomplish zero-carbon emissions by 2050. An important element of this procedure is the broader acceptance of renewables by the public. This paper investigates this concept by capturing citizens' view on renewable energy sources along with the overall concept of Circular Economy in Greece. By implementing a questionnaire analysis, empirical findings capture the intention of citizens to further develop and invest on renewable energy. Besides, our analysis identifies that as education level increases, the willingness to pay more for renewables and their acceptance from the public increases, as well. Finally, empirical findings indicate that Greek citizens are aware of the concept and the benefits arising from Circular Economy, yet additional efforts need to be addressed for the growth of this concept in Greece. • The study captures citizens' view on RES and Circular Economy in Greece. • Participants are aware and sensitive on environmental and climate change issues. • Participants accepted the existence of RES and are willing to pay additional cost. • As the level of education increased, willingness to pay for RES also increased. • Additional efforts need to be addressed for the growth of Circular Economy in Greece. [ABSTRACT FROM AUTHOR]

In this paper, the enhancement of melting behaviour in a shell and tube thermal energy storage (TES) device containing various structured fins is numerically investigated. Five innovative enhancement structures involving topology optimized fin, tree-shaped fin, snowflake fin, spiderweb fin, and a combined conventional fin and composite phase change material (CPCM) are quantitatively compared and evaluated. Two groups of experiments are carried out to validate the simulation codes for the devices containing topology optimized fin and CPCM, while the numerical models for the devices with longitudinal fin and pure PCM are verified by two sets of literature data. A comprehensive comparison is performed for these five enhanced configurations from multiple perspectives with the emphasis of investigation being placed on assessment of the economic efficiency of these structures through introducing a parameter of TES rate per unit cost. The results show that the use of enhanced structures achieves remarkable enhancement on the melting rate in a shell and tube device. Compared to the device containing no enhancement structure, the complete melting process can be accelerated respectively by 97.2%, 93.6%, 93%, 88% and 83.6% for the devices containing tree-shaped fin, spiderweb fin, snowflake fin, topology optimization fin, and joint longitudinal fin and CPCM. The implementation of tree-shaped fin provides the optimal economical solution to acquire the best utilization efficiency among the five structures, but the enhancement degree on the economic efficiency is intimately tied to the cost ratio of fin to PCM. In order to highlight the advantage of using tree-shaped fin on the improvement of heat transfer rate and economic efficiency, the cost ratio of fin to PCM in such enhanced structure is suggested to be controlled to less than 6.5. Moreover, fin material also presents a significant influence on the selection of performance enhanced structure since it affects not only the melting rate but also the material utilization efficiency within the device. Substituting aluminium alloy with cheaper steel as the fin manufacturing material makes the economic efficiency a whole declined. This indicates for achieving a combined improvement of melting performance and economic efficiency, the enhanced structure should be selected to have a high thermal conductivity and controllable cost that easy to manufacture. [ABSTRACT FROM AUTHOR]

To solve the problem of the lightweight design of metal fins and strengthen the heat transfer between phase change material (PCM) and lithium batteries, the synergistic design of fins and phase change material-battery thermal management system (PCM-BTMS) is particularly important. In this paper, 9 new branch fin design schemes were proposed based on the conventional straight fin. The reliability of the computational fluid dynamics model was verified through the heat transfer experiments at different discharge rates. Firstly, the thermal performances of 9 new fins and the conventional straight fin under 5C discharge rate were compared and analyzed, and the optimal model was selected. Secondly, the effects of transverse fin coverage area, number, arc length, thickness, and arc length of inner and outer arc fins on the thermal performance were analyzed considering the effects of different heat transfer coefficients. The results show that the preferred fins have less effect on the heat transfer coefficient enhanced thermal performance compared with the conventional fins; the average cell temperature is reduced by 3.14 K and 3.92 K respectively by increasing the fin coverage area and the number of transverse fins to increase the contact area with PCM to enhance heat dissipation; the average cell temperature changes more significantly with the inner arc fins, and the cell temperature of Case H6 was reduced by 7.2 K; while the transverse fin arc length extension reduced the thermal performance of the system in high temperature cases. The volume of system remained the same, and the thickness of the transverse fins decreased the heat storage capacity of the system when the thickness of the transverse fins was larger. The optimal fins could keep the average cell temperature within 318.15 K. The heat transfer capability was improved by 14.98%, the operating time was extended by 131.5%, and the system weight was reduced by 10.28%. [Display omitted] • 9 new branch metal fins are proposed to enhance the thermal performance of PCM. • The new branch fin structure can effectively reduce the cell temperature. • Coverage area, number, arc length, and thickness are key indices of transverse fins. • The inner and outer arc angles of fins greatly affect the heat transfer ability. • The new optimized branch fin structure better meets the lightweight design. [ABSTRACT FROM AUTHOR]

Concentrating and spectral beam splitting technology towards the efficient utilization of full-spectrum solar energy has been widely concerned. This paper proposes a novel non-confocal two-stage parabolic dish concentrating photovoltaic/thermal (NTPD-CPVT) hybrid system which offers access to the alleviation of photovoltaic heat load and the two-stage heating of heat transfer fluid through a specially developed spectral beam splitter. The thermodynamic and optical properties of the system are analyzed via the comprehensive model including ray tracing, energy flux evaluation and photovoltaic/thermal hybrid energy evaluation. Results indicate that the satisfied spot uniformity and optical efficiency of 80.7% could be obtained by non-confocal optimization, and the NTPD-CPVT hybrid system shows stable overall energy efficiency over 20.9% under different irradiance conditions. Based on the comprehensive comparison, the introduction of a spectral beam splitter promotes the photovoltaic/thermal module efficiency and the system exergy efficiency by 17.6% and 10.2%, and effectively shortens the payback period. Furthermore, the reference values of implemental parameters such as error tolerances and heat transfer coefficients are provided to guarantee the optical and economic performance of the system. The research results support the potential of the NTPD-CPVT hybrid system in improving the cascade use of solar spectrum and guide the construction of future prototypes. [Display omitted] [ABSTRACT FROM AUTHOR]

This study explored the concept of a floating offshore wind farm (FOWF) that self-reconfigures wind turbine (WT) positions. The self-reconfiguration (SR) mechanism moves degraded turbines to different farm positions to delay failures occurring and reduce power loss. A 40-turbine agent-based simulation was created utilising wind and turbine performance data. For the first time, the SR mechanism was designed and optimised with principles of self-engineering complexity. The paper demonstrates the effectiveness of the SR mechanism through an agent-based simulation approach. The optimised SR was used in FOWF simulations of 50 years of operation; SR balanced fatigue across the FOWF and led to an increased income of £5–40M at years 27–33 of operation; however, outside of these years, there is no net positive income, and by year 50 SR has cost the FOWF £4–7M more in movement costs. Lastly, simulations with repair and maintenance restricted to 10 months or less were conducted. SR delayed turbine failures, so they occurred in months when repair could be conducted. The SR reduced power loss and increased net income by up to £20M, indicating that SR could be useful when repair and maintenance times are limited. In the absence of significant operational data, a qualitative validation with experts confirmed the approach and the validity of the simulation model for a range of FOWF scenarios. [ABSTRACT FROM AUTHOR]

Light detection and ranging (LIDAR) sensors measure the free wind ahead of the rotor, enabling the use of new feedforward control strategies. However, there exist some sources of error inherent to the measuring process that should be considered during the design of LIDAR-based controllers. Typically, the coherence function is used for that purpose, but it is not compatible with some robust design methodologies. This paper presents an analytic relation between the coherence function and a non-parametric uncertainty model of LIDAR sensors, suitable for the design of controllers via μ -synthesis or Quantitative Feedback Theory. Such a relation is applied to a realistic LIDAR simulator. First, the linear non-parametric uncertainty model is identified using simulation data obtained from the well-known NREL 5 MW wind turbine. Then, it is validated against the coherence model by comparing linear predictions of the simulation outputs. • The squared coherence function is the standard measurement of LIDAR reliability. • Squared coherence is inversely proportional to a nonparametric uncertainty model. • The uncertain model is useful for analysis and robust controller design purposes. • The new model is compatible with design tools such as QFT and H ∞ control toolbox. • The new model has been validated against the FAST nonlinear simulator. [ABSTRACT FROM AUTHOR]

The most important challenge for both developed and developing countries is to ensure sustainability while struggling with environmental degradation. CO 2 emissions as a proxy for environmental degradation can be considered an obstacle to sustainability. There exist several significant works in the literature on the effects of solar energy use on environmental degradation/sustainability. In this study, the effects of the use of solar energy within different time and frequency dimensions on CO 2 emissions were examined with the methodology of the continuous wavelet transform. The paper investigated the association between solar energy consumption and total energy-related CO 2 emissions in the USA through Morlet wavelet analysis, which is one of the most advanced time-frequency analysis methods for the period 1990:1–2022:6. In the wavelet coherency computations, geothermal energy consumption, hydroelectric energy consumption, industrial production, and manufacturing industry production variables were also included as control variables. Empirical findings demonstrate that solar energy consumption can have reducing effects on CO 2 emissions at lower frequencies (longer-term cycles) and sub-time periods (2014:1–2022:1) in the USA. The findings can guide the energy and environmental policies of developed and developing countries that aim to struggle with global warming and/or climate change through the increase in solar energy usage. Source: The graphical abstract is a slightly modified version of Bilgili et al. (2022), Fig. 2. [Display omitted] • Investigates the impacts of solar energy use on CO2 emissions in the USA. • Follows wavelet/partial wavelet transform models. • Employs the control variables of industrial production, geothermal and hydro energy, as well. • The reducing effect of solar energy on CO 2 emissions appears at a lower frequency. • Solar energy is not effective in the reduction of CO 2 emissions at higher frequencies. [ABSTRACT FROM AUTHOR]

The emergence of new technologies, such as photovoltaic (PV) solar systems, household Battery Energy Storage Systems (BESS) and electric vehicles (EVs), has introduced challenges for the Distribution Network Operators (DNOs) in the operation of power distribution networks. Uncontrolled renewable energy generation and storage, and EV charging can cause over/under voltage problems. Recently, there has been much effort, from control and scheduling of BESSs and EVs to PV curtailment, to address these issues. However, the knowledge about how much penetration of these technologies can be well-tolerated by the grid when all charging/discharging are uncontrolled, would still be of interest to DNOs. There are many depending factors such as customer consumption profiles, grid conditions and network constraints. In this paper, we propose a framework to determine the critical balance between PV, BESS and EV in a distribution grid. Using real data from 4000 customers in Victoria, Australia, we find that in the absence of advanced control and scheduling algorithms, the best approach to prevent voltage violation in the grid is to keep the installation of PV and BESS balanced with the EV penetration. We also show that power export to the grid by EVs using the vehicle-to-home (V2H) technology may contribute to keeping the grid voltage in the standard range if 40%–80% of EVs are in the discharge mode in critical peak times. While complete coordination of PV, EV and BESS has not yet been fully realized in many networks, our methodology provides a framework for DNOs to perform optimised planning. [ABSTRACT FROM AUTHOR]

This paper presents a numerical study and experimental validation of humidification-dehumidification solar desalination unit. This unit consists of a solar evaporator and a tubular condenser. The design particularity of the evaporator is the integration of the humidifier in the solar air and water collectors. A mathematical model based on the heat and mass balances has been developed in the desalination unit. The finite difference method is adopted for discretization of the equations and the resolution is done by MATLAB software. Numerical results are compared with literature and experimental results. An acceptable agreement is observed. A parametric study was conducted to test the influence of the different operating parameters on the unit production and the Gained output ratio GOR. The production of the desalination system increases with air and water temperatures of the water in the evaporator and the inlet humid air temperature at the dehumidifier. It should be noted that the production reaches its maximum value for a feed water mass flow rate in the humidifier of 5.5 kg/h and a cooling water mass flow rate in the dehumidifier of 0.2 kg/s. [ABSTRACT FROM AUTHOR]

High-temperature steam is required to produce hydrogen with Solid Oxide Electrolysis Cells (SOEC), but generating steam can be power-consuming. Concentrated solar power is a good candidate for replacing electricity or fossil fuel in generating steam. This paper investigated the effect of spray on radiation transfer in a novel solar steam generator designed to utilize spray cooling to enhance heat transfer. The Monte Carlo ray-tracing technique, considering the absorption of droplets, absorption of water vapor, and multiple scattering of droplets, is employed to analyze the flux density at the focal plane and the spatial scattering power distribution of droplets. The results show that the total incident power transmittance is found to be in positive proportion to the mean droplet diameter while in reverse proportion to the spray volume fraction. Since the maximum difference in spectral transmittances is less than 1%, it is not feasible to adjust the wavelength for higher transmittance. The nozzle position seems highly affects the solar power distribution, and the central area is more affected than the outer area. Thus, increasing the spray volume fraction may uniform the flux density but reduce the transmittance. The spatial scattering power analysis indicates that increasing the droplet diameter can effectively improve the transmittance when the spray volume fraction keeps constant, which may be a solution when applied to a large-scale steam generator. [ABSTRACT FROM AUTHOR]

In this paper, a high-efficient and three-dimensional compact heat pump system integrated with the concentrated photovoltaic plus fins (CPV/fin-SAHP) is constructed and built. Smaller space occupation and higher energy utilization are realized. The mathematical model is completed and validated by experimental data. By changing the throttling device and adjusting the mass flow rate, the system performance is improved. From the results, the exergy efficiency, heating capacity, total output, COP PVT , and COP th of the CPV/fin-SAHP system are increased by 7.92%, 13.2%, 11.01%, 4.73%, and 7.12%. Moreover, compared with traditional single-source heat pumps, the CPV/fin-SAHP achieved the highest total output and COP PVT , showing great competitivity and potential. Then two-dimensional environmental variable coordinates are established to explore the compound impact of different ambient factors, and the capacities of the three systems with adjusted opening degrees are also comparatively analyzed. In general, wind speed and ambient temperature have greater impacts on the finned structure system, while the irradiance is dramatically affecting the PV-SAHP system. The compact CPV/fin-SAHP system is less dependent on a single ambient element, showing satisfied performance under various operating ambient and presenting the most potential in comprehensive ability. [ABSTRACT FROM AUTHOR]

Recycling spent lithium-ion batteries has received wide attention because the spent batteries are hazardous and contain high-grade and catalytic active heavy metals. Reductive roasting is an effective pretreatment method to recover valuable metals from the used batteries. In this paper, Crofton weed, which has been defined as an invasive plant in China, was suggested as a biomass pyrolysis additive for the reducing pretreatment of spent lithium-ion batteries powder (LiNi 0.6 Co 0.2 Mn 0.2 O 2). The process can reduce carbon consumption for the spent battery recycling industry. Meanwhile, the Ni, Co, and other metals in the cathode powder could catalyze biomass pyrolysis, reducing the reaction's activation energy. The effects of temperature, biomass ratio, heating rate, and roasting retention time on the reduction were studied. TG-DSC, XRD, and SEM were used to characterize the experimental results, and the pyrolysis reduction mechanism was analyzed. Under the optimum roasting conditions: temperature 800 °C, biomass ratio 30%, heating rate 5 °C/min, without retention time, Li in the powder is converted into Li 2 CO 3 , and the high valence Ni, Co, Mn are reduced to low valence and easily soluble Ni, Co, and MnO, respectively. This method provided an alternative technology solution for both spent lithium-ion battery treatment and controlling invasive plants in China, namely Crofton weed. [ABSTRACT FROM AUTHOR]

Climate change and scarcity of energy sources have put developing countries in a situation that demands emergency future planning for matured renewable technologies in order to continue sustainable progress and provide clean and cheap energy to masses. This paper provides a comprehensive structure of site suitability for utility scale solar PV and wind energy projects considering criteria critical to each technology while only using criteria with absolute necessity for varying scenarios incorporating Multi Criteria Decision Analysis (MCDA) along with Geographic Information System (GIS). A novel approach is also considered for far-off areas potentially deprived of electricity access for small scale solar PV implementation. A total of eight sub-criteria were considered in site selection process regarding wind and solar energy, analyzed using Analytical Hierarchy Process (AHP) in order to rank criteria depending on their importance to selection process. Resulting methodology was applied to case study of Pakistan, a developing country with growing climate change emergency and ongoing power crisis. End results showed 25.28% area suitable for utility scale solar PV farms, 5.93% area suitable for utility scale wind farms and 40.02% suitable area for small scale solar PV farms. [ABSTRACT FROM AUTHOR]

The combination of biomass and solar energy in the combined cooling heating and power (CCHP) system is conducive to reducing carbon dioxide emissions of the system. To improve the system's economic performance under the punishment of carbon tax, this paper optimizes the system from system design and operation strategies. A hybrid renewable energy CCHP system with shaft power distribution structure of an internal combustion engine (ICE) is proposed. By optimizing the shaft power distribution of ICE, the direct drive heat pump is realized, and the efficiency of the shaft power of ICE is improved. A double-layer optimization method considering the long and short-term benefits is proposed based on the system, fully improving the system economy in design and operation. The case study shows that the CCHP system reduces the annual cost by 40.37% and the CO 2 emission by 88.93% compared with the separate production system. Compared with the non-shaft power distribution system, the maximum daily operation cost is saved by 557.11CNY. Compared with the hourly optimization method, the proposed optimization method based on total daily benefit reduces the annual cost by 7.73% and CO 2 emission by 35.87%, and the utilization rate of the energy storage device is higher. [ABSTRACT FROM AUTHOR]

The alternation between cloudy and clear skies alters the photovoltaic production. This makes it necessary to anticipate these disturbances hours in advance for the correct operation of the electricity distribution plants and networks. In this paper, two short-term forecasting models (3 h) are developed to forecast the photovoltaic production in an integrated plant in the CIESOL building of the University of Almería. The methodology used is based on sky camera images and Artificial Intelligence techniques. Two models have been developed and compared applying artificial neural network (ANN) and support vector machine (SVM) techniques. The global irradiance predicted using sky camera images is used as an input variable in both models. In addition, the operational status of the plants has been included as an input parameter through the performance ratio. The results have shown that the errors made by ANN and SVM are very similar. For all sky conditions, the uncertainty of the production forecast differs by less than 2% from the uncertainty of the solar resource, which is the main source of error in the production models developed. [ABSTRACT FROM AUTHOR]

Sustainable microgrid is a feasible approach to handle environmental impacts and satisfy customer demand due to its economic, environmental, and social benefits. Due to the high initial investment cost, the installation rate of microgrids has been limited. Various studies investigated the influence of government subsidies on sustainable microgrid design to increase the installation rate. However, the effect of government subsidies, financial factors, and elasticity coefficient of demand under peer-to-peer energy trading has not been explored in the current sustainable microgrids design literature. To overcome this limitation, this paper investigates the sustainable microgrid design problem to simultaneously consider the effect of government subsidies, peer-to-peer energy trading, time value of money, elasticity coefficient of demand, and uncertainties. The objectives are to maximize total profit and minimize the total environmental cost to satisfy electric energy demand. Fuzzy multi-objective programming is applied to determine the optimal decisions on the number, location, type of renewable energy, the capacity of renewable distributed generation sources, electricity flows, price for selling electricity to demand areas and P2P energy trading, and government subsidy rates. A genetic algorithm and its hybrid versions to include tabu search and simulated annealing are then used to solve the proposed model. Numerical experiments used to evaluate the performance of the proposed model and algorithms show that the proposed genetic algorithm is most effective in maximizing total profit and minimizing environmental cost. Computational results demonstrate that on average, the inclusion of the peer-to-peer trading and government subsidies in the proposed model increases total profit by 13.23% and reduces total environmental cost by 6.29%. [Display omitted] • Sustainable microgrid design problem under impacted factors is investigated. • The effect of government subsidies and peer-to-peer energy trading are assessed. • Economic, environmental, and social objectives are considered under impacted factors. • Fuzzy multi-objective programming model is developed to handle the uncertainty. • Genetic algorithm and its hybrid versions are used to solve the propose model. [ABSTRACT FROM AUTHOR]

Direct-expansion solar-assisted heat pump (DX-SAHP) system has proven to be an effective energy-saving application. In view of the low output temperature and large radiant heat loss in the conventional flat plate type DX-SAHP, this paper proposed an evacuated tube type DX-SAHP system to realize performance enhancement. Then, an experimental prototype of the proposed system was originally designed and constructed in laboratory. Moreover, the thermodynamic performance of the system was thoroughly investigated and analyzed under different operating conditions. The results indicate that the thermodynamic performance of the proposed system is sensitive to the solar radiation intensity and collector area. About every 100 W m−2 increase of solar radiation intensity, the COP increases nearly 1.70% and the heat collection efficiency decreases nearly 8.44%. Increasing collector area (from 1.5 m2 to 3 m2) results in 8.81% increase of COP and 22.47% reduction of the system exergy efficiency. A higher circulating water temperature can effectively improve its exergy performance and higher ambient temperature can enhance its energetic performance. Additionally, the optimization of the evacuated tube collector-evaporator should be preferential to improve the system due to large exergy destruction and low exergy efficiency. [ABSTRACT FROM AUTHOR]