Search

Solar photovoltaic thermal system (SPTS) can fully tap solar energy resources to realize thermal and electric supply for users simultaneously, but the volatility and uncertainty of renewable energy and load cause the imbalance of energy supply. This paper proposes a multi-time scale optimal scheduling method for SPTS based on event-triggered model predictive control (ET-MPC) considering battery performance deterioration. Firstly, SPTS is divided into day-ahead and day-in optimization layers from different time scales. Day-ahead scheduling takes the minimization economic cost as the optimization function to obtain pre-scheduling plan, and day-in scheduling adapts rolling optimization scheme based on model predictive control (MPC) to reduce power fluctuations and achieve optimal scheduling adjustment. Moreover, the battery performance decay parameter is introduced into the MPC model and embedded into the optimization problem to prolong the cyclic life deterioration, and an event-triggered mechanism is introduced into MPC to improve the computational efficiency and reduce the communication frequency. Finally, the results show that the proposed double-layer scheduling method improves 4.15 %, 66 % and 13.39 % respectively regarding cost, power fluctuation and battery maintenance, and improve the calculation efficiency of 48.89 % compared with standard MPC method, which indicates that the proposed method has good economy, stability and execution efficiency. • This paper proposed energy scheduling for solar photovoltaic thermal system (SPTS). • Double-layer optimal scheduling is proposed to realize the economy and stability. • Battery service time is prolonged through defining performance index. • An event-triggered mechanism is introduced to MPC to reduce the communication burden. • The proposed method improves performance from different perspectives. [ABSTRACT FROM AUTHOR]

The increasing expansion of photovoltaic power generation leads to unpredictable fluctuations in electricity supply, which can potentially jeopardize the stability of the power grid and escalate the costs associated with grid imbalances. As a result, precise forecasts of photovoltaic power generation play a vital role in optimizing capacity deployment, enhancing consumption levels, improving planning strategies, and maintaining grid balance within systems characterized by significant penetration of solar energy. This paper proposes a structural adaptive grey seasonal model based on data reorganization. Solar photovoltaic power generation data typically exhibit seasonal fluctuations, which pose a challenge to existing prediction techniques. Therefore, this paper adopts the idea of data reorganization to eliminate the seasonal fluctuations of observations, and the adaptive accumulation operator can accurately simulate the change trend of the original data in different periods, overcoming the defect of insufficient adaptability of the traditional accumulation operator. Subsequently, the time trend items are incorporated into the model structure to identify the trend characteristics of system development, which can effectively explain the power generation trend of photovoltaic systems at different time periods and improve the prediction accuracy of the model. In addition, the compatibility and unbiased nature of the proposed model have been demonstrated to help us better perceive the model. The Grey Wolf Optimizer (GWO) is used to optimize the adaptive parameters of the model, endowing it with higher flexibility and stronger adaptability. In order to verify the effectiveness of the model, three practical cases (namely quarterly solar power generation in the United States, Japan, and Germany) were compared with existing econometric techniques, artificial neural networks, and grey prediction methods. The experimental results show that the new model outperforms other benchmark models in both simulation and prediction performance, and enjoys high robustness. • A novel grey seasonal model with data reorganization is established. • The proposed model can grasp nonlinear and fluctuant in various datasets. • The robustness analysis of the novel model is established. • Comparative study shows that the novel model is superior to other models. • Relevant suggestions are put forward according to the prediction results. [ABSTRACT FROM AUTHOR]

The utilization of supercritical carbon dioxide (sCO 2) in the Brayton cycle presents several advantages, such as compact equipment, high efficiency, and rapid response time. The sCO 2 power cycle can be applied in coal-fired power, solar thermal power, and nuclear power systems. Over the past 10 years, many scholars have researched sCO 2 power systems. The compression (pressurization) process is a core thermodynamic process in sCO 2 power cycles, achieved through the use of compressors. Therefore, compressors are important components in sCO 2 power systems. This paper provides a summary of recent studies on compression processes and compressors for sCO 2 power systems. The impact of near-critical-point characteristics of the compression process on equipment and sCO 2 power cycle systems is discussed. The investigations of the performance parameters, design considerations, design methods, and performance prediction methods of sCO 2 compressors are reviewed. The typical research results on CO 2 condensation at the compressor inlet, the effects of operating conditions on compressor performance, as well as optimization of design parameters, are also summarized. Additionally, it provides a summary of sCO 2 compressor prototypes developed by research institutes worldwide and experimental studies. Finally, the current issues with sCO 2 compressors are addressed, and the main future research directions are proposed. This paper will contribute to the development of compressors and promote the acceleration of the commercialization of sCO 2 power systems. • Summary of recent studies on compression processes for sCO 2 power systems. • Near-critical-point characteristics of compression process is discussed. • Summary of compressor prototypes by research institutes and experimental studies. • Current issues and future research directions on sCO 2 compressors are presented. [ABSTRACT FROM AUTHOR]

Accurate photovoltaic (PV) power forecast is crucial to power systems. Solar irradiance forecast is the fundamentals of PV power forecast. Current researches merely focus on improving the forecast accuracy. There hasn't been comprehensive study on the spatial-temporal characteristics of solar irradiance forecast errors. Thus, this paper analyzed the error characteristics of solar irradiance forecast provided by European Centre for Medium-Range Weather Forecasts (ECMWF), one of the most accurate numerical weather prediction (NWP) products. ECMWF's forecasts were compared with ERA5 solar irradiance reanalysis data to reveal the error distribution characteristics. Four-year (2017–2020) data from the geographical region bounded by 63°N, −126°W, 21°S, and 36°E (covering most parts of Europe and North America) were studied. Experiments show that solar irradiance forecast errors peak at noon of the local time. Furthermore, correlations between solar irradiance forecast errors and other weather variables were also revealed. Experiments show that solar irradiance forecast errors have negative correlation with low cloud cover forecast errors and positive correlation with air temperature forecast errors. The possible reasons for the correlation relationship were also analyzed in detail. This paper systematically reveals the spatial-temporal characteristics of solar irradiance forecast errors and provides a useful guideline for solar PV system operation. • Error distribution of ECMWF's solar irradiance forecast in Europe and North America is revealed. • Solar irradiance forecast errors in Europe are smaller than those in North America. • Solar irradiance forecast errors peak at noon of local time. • Solar irradiance forecast errors have slight seasonal and monthly differences. • Correlation between solar irradiance forecast errors and other weather variables is revealed. [ABSTRACT FROM AUTHOR]

New materials and designs have been developed and proposed to enhance the thermal and electrical performance of photovoltaic-thermal (PV/T) systems in recent years. Despite the significant attention received by PV/T technology, the available PV/T modules are scarce due to complex system designs, environmentally unfriendly working fluids, and low thermal efficiency. In this paper, a highly efficient water-based PV/T system is proposed by combining an innovatively designed cooling system with a PV module. An experimental evaluation of the designed PV/T system was carried out in laboratory conditions. The test results of the PV/T system showed that when the inlet mass flow rate and temperature were 0.0458 kg/s and 11.90 °C, the PV/T system reached the maximum thermal efficiency of 96.47 ± 1.40 %. The increase in mass flow rate from 0.0042 kg/s to 0.0375 kg/s and the decrease in inlet temperature from 17.70 °C to 11.40 °C led to a 12 % improvement in thermal efficiency of the PV/T system showing that the inlet mass flow rate and temperature have a significant influence on thermal efficiency. The developed 3-D numerical model accurately estimated the outlet temperature of the PV/T system. A maximum of 3.43 % error occurred between the experimental results and model output. • The paper proposes a novel, highly efficient, state-of-the-art PV/T system. • The designed PV/T system achieves a maximum thermal efficiency of 96.47 ± 1.40 %. • The designed cooling system reduces the PV module temperature by 40.72 °C. • The electrical conversion efficiency of the PV module is enhanced by 18.32 %. [ABSTRACT FROM AUTHOR]

Traditional flat PV heat pumps has low irradiation density, large PV area, and the PV evaporators are always fixed, causing large area occupation and lots of irradiation missing, which limit the application and system efficiency. To solve the problems, a novel concentrated PV-air dual-source heat pump system (CPV-DSHP) was proposed in the previous paper, but the annual performance and economic comparison with flat PV-DSHP (FPV-DSHP) are still blank, which are extremely concerning to researchers. Besides, the paper also fills related content about the impact of irradiation composition on the system performance and economics, as well as the irradiation comparison on tracking CPV and fixed FPV surface. From the calculation of the validated model, it's found that the CPV-DSHP system could capture 6098 MJ and 2213 MJ more solar energy, and produce 282.21 kWh and 100.16 kWh more electricity in Garze and Hefei in a year. The annual concentration efficiency is 82.73 % in Garze where direct irradiation accounts for 68.89 %, which is only 73.15 % in Hefei with 39.84 %.The COP PVT is annually lifted by 0.40 in Garze. Although the two systems could both get payback in 5∼6 years, the CPV-DSHP only shows economic advantages in places with good direct irradiation conditions like Garze. • A novel concentrated PV-air dual-source heat pump system (CPV-DSHP) is presented. • The annual performance and economic comparison in different cities are supplemented. • The CPV-DSHP could produce 282.21 kWh more electricity in Garze in a year. • The annual concentration efficiency is 82.73 % in Garze with better direct irradiation. • Payback time is 5∼6 years but CPV-DSHP only shows economic advantage in Garze. [ABSTRACT FROM AUTHOR]

The solar-assisted heat pump (SAHP) systems are increasingly gaining attention for their potential feasibility in various fields due to their energy saving benefits. However, the available research shows that SAHP still has potential for improvement in drying filed, especially in terms of combining vapor compression heat pumps with solar energy. Consequently, this paper aims to summarize the development of SAHP technology and provide guidance for the application of SAHP technology in the drying field. The development of the SAHP systems is reviewed in this paper, including four ways to enhance the performance of SAHP systems are discussed: photovoltaic/thermal systems, collector optimization, energy storage and ejector enhancement. The technology of energy storage and ejector enhancement will inspire the development of SAHP technology. Additionally, research on optimizing the performance of hybrid heat source heat pump systems is also discussed, and a review of alternative refrigerants that could be used in SAHP systems. It could be found that R134a is the most widely used in SAHP systems currently, but it needs to be replaced soon for its high GWP. HFOs refrigerants are a good alternative. Furthermore, the application prospect of SAHP systems in drying field is also analyzed. Finally, based on the current research status of SAHP technology, the future development trend and research directions of solar-assisted heat pump drying (SAHPD) are proposed: developing suitable refrigerants for heat pump systems; researching high-efficiency heat storage technology; developing multi-heat source assisted heat pump systems; and optimizing the operation strategy of SAHPD using artificial intelligence. • Four ways to enhance SAHP systems are reviewed. • Study on optimization of hybrid heat source heat pump systems is summarized. • The alternative refrigerants in SAHP systems is investigated. • The application prospects of SAHP systems for drying field are analyzed. • The future development trend of SAHPD systems is proposed. [ABSTRACT FROM AUTHOR]

Photovoltaic double skin façade (PV-DSF) offers a versatile solution to address the escalating energy demands of buildings by combining power generation and indoor air temperature adjustment functionalities. Most prior research concentrated on its summer performance, while the winter season receives less attention. This paper concentrates on its operation performance in winter, to provide an experimental framework for its efficient operation. In this regard, the performance of internal circle and thermal buffer mode (both are possible operation modes in winter) were compared via control variable experiments, and the feasibility of mechanical ventilation is also examined regarding the trade-off between the energy consumption of fans and additional energy benefit. These experiments were performed in the full-size experiment rig at Harbin, China, a city with severe cold climate. The experiment results conclusively demonstrate that the internal circle mode can outperform the thermal buffer mode on a cold, sunny day by 10.9%, and the total energy-saving potential can be further increased by 12.6% if fans are activated to enhance cavity airflow. While the experimental data during partly cloudy emphasizes the significance of a suitable operation schedule and shows that PV-DSF can only be switched to internal circle mode when cavity air is fully heated. • The performance of photovoltaic double skin façade (PV-DSF) in winter is studied. • A fully-size experiment rig is constructed to perform comparison experiment. • The internal circle mode can outperform thermal buffer mode by 10.9% in clear day. • The fans can speed up cavity airflow and improve total energy efficiency by 12.6%. • The results of this paper emphasize the importance of a real-time control strategy. [ABSTRACT FROM AUTHOR]

A new absorber surface is designed for solar air heaters to make them compact and enhance heat transfer parameters. The current paper presents the novel absorber design using a tubular surface having three-pass in counter-flow. The absorber tubes are constructed from thin sheets of aluminium; 15 tubes are closely spaced in line with each other to establish three-pass, i.e. five tubes per pass. The research paper investigates numerically and experimentally the thermo-hydraulic performance of a Tubular Three-pass Solar Air Heater (TTPSAH). The numerical model was developed using MATLAB to predict the performance and outlet air temperature. The error in numerical and experimental evaluation is approximately 5%, showing promising results. It was found that the TTPSAH accelerates heat transfer in a compact surface area. The maximum thermal efficiency was evaluated as 60.04%, 41% and 33.3% for an airflow rate of 0.006 kg/s, 0.004 kg/s, and 0.002 kg/s respectively. Thermal enhancement with a maximum outlet air temperature of 110.6 °C, 91.4 °C and 80.2 °C was recorded at a mass flow rate of 0.002 kg/s, 0.004 kg/s and 0.006 kg/s in glazed conditions. Furthermore, the research includes an estimation of the energy cost per kilowatt-hour (kWh), which amounts to $0.017, $0.025, and $0.0311 for mass flow rates of 0.006 kg/s, 0.004 kg/s, and 0.002 kg/s, respectively. • To increase the applicability of solar energy a novel tubular three-pass solar air heaters was designed. • The mathematical model and experimental results are in good agreement. • The maximum outlet air temperature of 110.6 °C attained for a flow rate of 0.002 kg/s. • The thermohydraulic performance parameters of TTPSAH was also studied. [ABSTRACT FROM AUTHOR]

Water scarcity is a major global challenge, with 2.3 billion people living in water-stressed countries and the potential for 700 million people to be displaced by 2030 due to widespread water scarcity. The increasing effects of climate change and overpopulation are exacerbating the problem, particularly in arid and remote regions. One potential solution is the harvesting of atmospheric water, which is estimated to be a vast source of freshwater at 12,900 km3. This study aims to provide a comprehensive and up-to-date review of the latest research in the field of atmospheric water harvesting systems. The purpose of this review is to present the various types of harvested water, the use of solar energy, the methods of gathering it, and the mathematical models used in the literature. The paper has covered numerous types of atmospheric water harvesting techniques, including harvesting dew and fog. In addition, the paper has also discussed water harvesting technologies that rely on sorbent materials. The primary focus of the paper is to present recent advances in water harvesting systems, such as dehumidifying, condensing, vapor compression refrigeration cycles (VCRCs), thermoelectric coolers (TECs), air conditioning units, fuel cells, and integrated systems. The paper aims to provide a comprehensive understanding of the latest developments in atmospheric water harvesting systems. The paper also presents an assessment of the efficiency and effectiveness of these water harvesting systems. The paper concludes by comparing various approaches to provide accurate descriptive information regarding the amount of water harvested. Additionally, the article proposes suggestions to enhance current water harvesting systems and outlines potential future initiatives. • Water harvesting from fog and dew is a promising source of water. • Sorbent materials have the capacity to absorb moisture and generate water from the atmosphere. • TECs are suitable for collecting atmospheric water across many global regions. • Top water-collecting materials absorb moisture, convert it to water in few in minimal time. • VCRC-based devices offer substantial atmospheric water harvesting potential, analysis shows. [ABSTRACT FROM AUTHOR]

Improving the forecasting accuracy of wind power, solar power, and system load to support the source-load cooperative dispatch is an important direction to reduce the uncertainty at source and load sides. The current research mainly focuses on a single object, ignoring the interactive coupling relationship among them, which limits the improvement of forecasting accuracy. Therefore, this paper proposes a short-term integrated forecasting method of wind-solar-load. Firstly, a feature extraction module of linkage characteristics of wind-solar-load is built based on variable attention mechanism. Secondly, a multi-task learning model that can automatically calculate the optimal loss weights for different forecasting tasks is constructed to simultaneously accomplish the wind and solar power forecasting tasks through Fully Connected Neural Network. Finally, a load forecasting model which fuses historical load and power forecasting information is established based on Long Short-Term Memory. The operation data of 8 wind farms and 6 solar plants, and the load data of a nearby city are used for instance analysis. The results show that the power forecasting error (root mean square error) of each wind farm, solar plant, and system load is reduced by 4.84 %, 1.86 %, and 3.02 % on average, respectively, compared with the corresponding traditional methods. • Build a feature extraction module to max data value and reduce model complexity. • Construct a multi-task learning model that can auto calculate optimal loss weights. • A short-term integrated forecasting method of wind-solar-load is proposed. • Wind, solar, load prediction error is reduced by 4.84 %, 1.86 %, 3.02 % on average. [ABSTRACT FROM AUTHOR]

Energy efficiency is crucial for the sustainable operation of industrial and urban sectors. However, practicing engineers seldom have access to open-source tools that can readily evaluate and compare scenarios. In this work, a novel web-based tool called ROSMOSE is developed and proposed for analyzing the energy efficiency of industrial and urban systems and comparing potential process integration options. This optimization framework computes and graphically represents the minimum energy requirements, the pinch temperatures, and the Grand and integrated Carnot composite curves of process systems. Results are used to design utility systems that meet energy demands, while minimizing a specified objective function, such as total cost or environmental impacts. The Quarto environment, in which ROSMOSE is built upon, allows the integration of various open-source software and tools, such as database handling software, process modeling suites, and optimization solvers, along with interactive data visualization and reporting tools. This paper discusses the application of ROSMOSE for the energy integration and total site optimization of a dairy process consisting of milk treatment, and cream and cheese production to demonstrate the tool features. Other integration options, such as the use of heat pumps or solar panels, and the production of soft drinks or biogas as value-added byproducts, are also proposed and evaluated. As a result, from 75 % to 90 % in fuel savings and up to 80 % CO 2 emissions reduction in the dairy plant are identified by optimizing the utility systems integration. Moreover, complete electrification via heat pumps eliminates any fossil fuel needs and it results in 85 % energy savings and up to 96 % CO 2 emissions reduction. The activation of renewable electricity sources, such as solar power, made plausible this fully electrified scenario. Finally, optimized waste management strategies led to in-house fuel production and net export of biogas to the grid, but they also reduce cheese yield by prioritizing the biogas production from whey upgrading process. In this way, decision-makers have access to a clear performance comparison for a list of system configurations to draw informed trade-offs. A similar approach could be adopted to aid decision-making for the design and operation of other industrial and urban energy systems using ROSMOSE. [Display omitted] • ROSMOSE is an open-source energy integration, optimization and reporting tool. • Pinch analysis and other assessments of decarbonization strategies can be performed. • The process integration and waste valorization of a dairy plant is used as case study. • Above 75 % energy saving is achieved by process integration and optimal utility selection. • 96 % reduction in CO 2 emissions and on-site biogenic energy sources are identified. [ABSTRACT FROM AUTHOR]

Latent heat thermal energy storage based on phase change materials (PCM) is considered to be an effective method to solve the contradiction between solar energy supply and demand in time and space. The development of PCM composites with high solar energy absorption efficiency and high energy storage density is the key to solar thermal storage technology. In this paper, a green and simple method is proposed to fabricate a porous PCM with stable shape, low supercooling degree and excellent photo-thermal conversion performance. The novel PCM which combine porous expanded graphite as the carrier material, n-eicosane as the stabilizer and sodium acetate trihydrate (SAT) as phase change energy storage material are designed and prepared by melt blending method. The expanded graphite contributes to the stable shape of the composites, and provides excellent thermal conductivity channels and light absorption properties as well. The composite PCM sample containing 3.3 wt% expanded graphite achieves excellent performance, phase change enthalpy of 266.54 J/g and a photothermal conversion efficiency of 91.14 %, and shows low supercooling degree of 2.2 °C with almost no leakage at 90 °C. [Display omitted] • A porous PCM with excellent photo-thermal conversion performance was fabricated. • The novel PCM combines porous EG, n-eicosane and SAT. • Phase change enthalpy of 266.5 J/g and supercooling degree of 2.2 °C were achieved. [ABSTRACT FROM AUTHOR]

Scientists initiated a pursuit of more resilient and long-lasting energy sources due to the continuous deterioration of the environment and the substantial rise in the expense of conventional energy sources. Solar energy is one of the most cost-effective, environmentally friendly, and easily accessible sustainable energy sources. Photovoltaic/thermal (PV/T) solar modules are gaining popularity due to their ability to utilise more solar radiation to generate electric power and heat gain simultaneously. This study reviews recent advancements in PV/T modules, focusing on the dual conversion of solar radiation into electrical and thermal energy. The review highlights significant improvements, such as the use of nanoparticles, bi-fluid circulation, and innovative cooling techniques. The study examined the main categories of PV/T systems, including air-cooled, water-cooled, bi-fluid-cooled, nano-fluid-cooled, and ternary nanofluid-based units. This paper offers an in-depth analysis of various components within PV/T modules, covering aspects such as concepts, materials, and review techniques. However, challenges remain, including the trade-off between thermal and electrical efficiency and integration into existing infrastructure. Despite these limitations, PV/T systems show great potential for contributing to sustainable energy solutions and achieving global sustainable development goals. Future research directions include integrating an artificially intelligent approach for system optimization and expanding hybrid PV/T technologies. [Display omitted] • A graphical summary of the PV/T types is demonstrated. • Sustainability achievements by the PV/T modules are discussed. • Water, air, nanofluid, and bi-fluid-based coolants are summarised. • Ternary nanofluid-based PV/T is reviewed. [ABSTRACT FROM AUTHOR]

The solar-driven hollow fiber membrane dehumidification (SHFMD) system is a renewable, energy-saving, and highly effective dehumidification system. It provides an effective solution to the problem of air-entrained liquid droplets during the traditional solution dehumidification process. The system's mathematical model was established and the reliability of the mathematical model was verified by experimental data. To enhance the comprehensive performance of the system, the multi-objective particle swarm optimization (MOPSO) algorithm is used in this paper to optimize the multi-objective parameters of the system. The objective function is the total exergy destruction of the system and the dehumidification capacity of the system. The optimization variables are cold water temperature, cold water flow rate, solution flow rate, air flow rate, and hot water flow rate. The optimization is performed using the multi-objective particle swarm optimization (MOPSO) algorithm to obtain the Pareto front, and the points of the Pareto front are normalized. Finally, the optimal trade-off point of the Pareto frontier is obtained. Each operating parameter of the optimal point of the Pareto front is also analyzed. The results show that the air flow rate and cold water flow rate have the most influence on the conflict between the total exergy destruction of the system and the dehumidification capacity of the system. • Solar-driven hollow fiber membrane dehumidification system is modeled and validated. • The system's total exergy destruction and dehumidification capacity are optimized. • Air flow rate has a great impact on the conflict between system optimization. • Cold-water flow rate has a great impact on the conflict between system optimization. • The multi-objective particle swarm optimization algorithm is used. [ABSTRACT FROM AUTHOR]

In this paper, a direct-expansion heat pump water heater system integrated uninsulated micro-channel PV/T solar collector (UMC-PVT-SC) is proposed. This system can realize storage for both thermal energy and electricity, ensuring the supply of domestic hot water. The theoretical models of micro-channel PV/T solar collector, hot water storage tank, compressor and electronic expansion valve are established to investigate the performance of the micro-channel PV/T heat pump water heater system. R134a is used as refrigerant. The system performance is numerically simulated using MATLAB for different solar radiation intensity, ambient temperature and wind speed. The results show that solar radiation intensity has the largest influence on the system performance, followed by ambient temperature and wind speed. The coefficient of performance of the heat pump (COP HP) and the overall coefficient of performance (COP pvt) of the integrated system increase while the required operating time reduces, as solar radiation intensity and ambient temperature increase. The uninsulated micro-channel PV/T solar collector (evaporator) can absorb thermal energy from both ambient air and solar radiation and therefore achieve high COP HP , electric efficiency and COP pvt. Even under cold weather conditions, the proposed solar collector and heat pump heater demonstrate high efficiencies, heating and power generation capacities. When ambient temperature is −18.6 °C and solar irradiance is 322 W/m2, the collector efficiency and electric efficiency of UMC-PVT-SC are still at 0.718 and 0.244, respectively, and the COP HP and COP pvt of the heat pump heater are 3.5, 5.63, respectively. The present work is of potential value for delivering net zero. • A novel uninsulated micro-channel photovoltaic/thermal solar collector is designed. • The photovoltaic/thermal solar collector can absorb heat from air without sun. • The overall energy efficiency of photovoltaic/thermal solar collector can reach 1.86 in winter. • It is a simple and low-cost solution of the combination of solar energy and heat pump. • The solar assisted heat pump can operate independently without external electric power. [ABSTRACT FROM AUTHOR]

The characteristic of joint consumption creates complex linkage between metal markets, which helps provide new insights into the energy-metal nexus relationship. To this end, this paper analyzes the price spillover effects between clean energy metals with joint consumption properties and further captures clean energy market's role in this dynamic connectedness. The results show that: (1) There are significant spillover effects within the clean energy metal markets, mainly dominant by short-term factors. The price fluctuation risk in the wind energy metal markets is more easily transmitted than the solar energy metal markets. (2) Copper and Tellurium markets are the main sources of risk in the spillover network of solar energy metal markets, while Copper and Aluminum act as the centers of risk transmission in the spillover network of wind energy metal markets. (3) Clean energy markets significantly impact the spillovers of metal markets, and exhibit non-linear movements, altering the spillover roles of some metal markets in the spillover network. Our findings reveal the system-wide price fluctuation patterns in clean energy metal markets, helping provide targeted recommendations in the risk management of energy-metal nexus system. • Significant short-term spillover effects exist within the clean energy metal markets. • The price fluctuation risk in the wind energy metal markets is more easily transmitted than the solar energy metal markets. • The spillover behaviours between clean energy metal markets exhibit less sensitivity to financial market fluctuations. • Clean energy markets strongly impact the spillover effects of joint-consumed metal markets in a non-linear way. [ABSTRACT FROM AUTHOR]

Solar aided coal-fired power generation (SAPG) technology has been proven to be an effective way of renewable energy utilization. However, the efficiency of coal-fired units declines at partial loads, and solar inputs may further force the system to deviate from its design condition. In particular, part-load operation solutions for coal-fired units (PLOS) are conventionally applied to the SAPG system, a practice whose appropriateness has not yet been thoroughly evaluated. This paper, therefore, selects a 330 MW SAPG plant as a case study to conduct an exhaustive exergy analysis under off-design conditions. The findings indicate that the governing stage of the steam turbine and the slip-pressure operation are the main contributors to the efficiency degradation at partial loads. In addition, solar input resulted in significant changes in key operating parameters, such as exhaust flow rate and the pressure of each turbine stage. Merely adopting the PLOS for SAPG systems results in a marked increase in standard coal consumption by 0.99, 2.82, and 3.63 g/kWh at 50 %, 40 %, and 30 % load, respectively. However, the introduction of solar energy presents the potential to operate the unit more efficiently, particularly when valve point conditions are optimally adjusted. For instance, upon input of 28 MW solar thermal power, the #3 valve point condition shifted from a load of 321 MW–330 MW, achieving a reduction in standard coal consumption by 0.96 g/kWh, compared to the design condition of the original coal-fired unit. This study underscores the irrationality of directly applying PLOS from coal-fired units to SAPG system without tailored adjustments for solar integration. • Identifies the causes of efficiency decline in coal-fired units at partial loads. • Analyzes the impacts of solar inputs on exergy loss across processes in SAPG systems. • Highlights irrationality in using coal unit part-load solutions to SAPG systems. • Demonstrates potential efficiency improvements through strategic valve point changes. [ABSTRACT FROM AUTHOR]

In order to improve the utilization of renewable energy in energy applications and to solve the problem of intermittency in the process of solar energy application, this paper introduces a trans -critical CO 2 energy storage system integrating solar energy and heat supply, and thermodynamic analysis and advanced energy efficiency analysis of the system are carried out. The system demonstrates impressive performance under standard conditions, achieving an energy storage efficiency of 77.19 %, and an exergetic efficiency of 68.03 %. The system's maximum avoidable exergy destruction is 4.17 MW, representing 68.77 % of the total exergy destruction, indicating significant potential for improvement. When it comes to component optimization, there are disparities in the results obtained through conventional exergetic analysis and advanced exergetic analysis. Conventional exergetic analysis suggests that the Reheater 4 should be optimized initially, followed by expander 1 and intercooler 3 optimization. However, according to advanced exergetic analysis, the recommended sequence is to optimize the Reheater 4 first, followed by expander 1 and intercooler 3. Advanced exergetic analysis reveals a significant endogenous exergy destruction of 68.23 % within the system, indicating weak inter-component relationships. Consequently, the primary focus should be optimizing the components themselves, with special emphasis on the RE4 and intercooler 3, as they have the largest exergy destructions. [Display omitted] • A trans -critical CO 2 energy storage system integrated with heat supply and solar energy is proposed. • The thermodynamic and advanced exergy analysis of the proposed system is applied. • The energy storage efficiency of the system under standard operating conditions is 77.19 %, and the EGV is 17.22 kW-h/m3. • The maximum avoidable exergy destruction is 4.17 MW at an output power of 10 MW, which is 68.77 % of the total destruction. [ABSTRACT FROM AUTHOR]

The high proportion and volatility of renewable energy pose a significant challenge to efficient collaboration between photovoltaic/thermal and wind power in multi-energy systems. Therefore, this paper proposes a Regional Multi-Energy System (RMES) based on Medium-High Temperature Solar Thermal (MHTST) technology. The novelty of the solution integrates dispatchable photovoltaic and photothermal conversion pathways, facilitating flexible and controllable utilization of solar energy via installed Thermal Energy Storage (TES). A multi-objective optimization model is developed to ensure the optimal operation of the proposed system under typical seasonal scenarios. The method that combines Branch-and-Reduce with Multi-Learning-Task is used to handle the formulated Mixed Integer Nonlinear Programming (MINLP) and swiftly identify optimal Pareto solutions. Case studies are performed over the improved united communities of the Test Region for Energy Transition and Comprehensive Reform in Taiyuan, China. Compared with the conventional photovoltaic technology, the simulation results show that the proposed solution has superior performance in both winter-heating and summer-cooling operations across 24-hour scheduling periods: operating costs reduced by 12.5% and 18.7%, carbon emissions decreased by 7.4% and 21.4%, with local solar power accommodation increased by 263.89kW and 487.47kW, respectively. • A novel regional multi-energy system integrating medium-high temperature solar thermal is proposed. • The model solution combined branch-and-reduce with multi-learning-task is proposed. • The proposed strategy offers optimal energy schedules while reflecting renewable electricity trading. • System performances of photovoltaic and medium-high temperature solar thermal systems are compared. [ABSTRACT FROM AUTHOR]

The application of combined cooling, heating, and power (CCHP) systems to generate both electricity and heat is growing quickly due to their high potential of lessening primary energy utilization, cost, and negative environmental impacts. This paper introduces a comprehensive review of hybrid fuel-assisted-solar powered Stirling engine-based combined cooling, heating, and power (HFSDSS-CCHP) systems. This article summarizes the typical configurations of SDSS CCHP systems, their energetic, economic, and environmental performances, as well as their operation strategies. The advantages and disadvantages of each system have been discussed. Thermodynamic models for the system components of solar - powered Stirling engines for the CCHP system are briefly presented. Besides, the most widely accepted performance indicators for guiding the Stirling engine-based CCHP system improvements are highlighted. Moreover, this review discusses the recent developments and performance analyses of CCHP systems. It is anticipated that the data gathered in this review will shed light on the promising technology of the Stirling engine for micro-trigeneration to pave the way for their marketability and extend their worldwide applications. • Recent technologies of hybrid solar - powered Stirling engine-based CCHP) systems are presented. • Recent developments allowed them to high potential for market penetration. • Operational strategies should be further investigated. • Formal indicators for energetic, economic, and environmental performances should be developed. [ABSTRACT FROM AUTHOR]

Multi-area economic dispatch (MAED) incorporating renewable energy has become an important issue in the power system optimization. Existing intelligent optimization algorithms often suffer from poor solution accuracy or slow convergence when dealing with MAED problems. In this paper, a novel derivative search-based political optimization (DSPO) algorithm is proposed to handle the MAED problem incorporating renewable energy including wind and solar energy. In the renewable energy modeling, the Weibull and log-normal probability density functions are used to calculate available wind and solar power respectively. In order to improve the search performance, DSPO adopts two strategies: leader guide strategy and derivative search mechanism. The former adds the leader's global optimal information which can direct candidate solutions to more promising regions and speed up convergence. The latter derives neighborhood solutions around some high-quality solutions to improve the exploitation ability. The DSPO algorithm is applied to solve four MAED problems which take into account valve point effect, prohibited operating zone, power loss and so on. The simulation results show that the DSPO algorithm achieves the overall best results in terms of convergence speed, solution accuracy and stability when compared with several well-established algorithms. • Multi-area economic dispatch with wind and solar energy (MAEDWS) is studied. • Novel derivative search political optimization (DSPO) algorithm is developed. • A leader guide strategy and a derivative-search mechanism are embedded into DSPO. • DSPO achieves the best results regarding convergence, accuracy and stability. [ABSTRACT FROM AUTHOR]

Liquid air energy storage (LAES) presents a promising solution to effectively manage intermittent renewable energy and optimize power grid peaking. This paper introduces a LAES system integrating LNG cold energy to flexibly manage power peaking, including intermediate energy storage, power generation using organic Rankine cycle, multi-stage direct expansion, and solar energy for heating. Aiming to maximize the electrical round-trip efficiency, a genetic algorithm is employed to optimize the operational parameters of the proposed LAES system. The results indicate that the combined design of cold energy utilization, multi-stage direct expansion and solar heating for proposed LAES system significantly improve the power performance, achieving an energy capacity of 0.125 kWh/kg LNG and an electrical round-trip efficiency of 376.7 %. The exergy losses of heat exchange equipment are far larger than mechanical equipment in the LAES system, so the optimization design of heat exchange equipment is preferred to improve the exergy performance. The proposed system achieves both high efficiency and flexibility and hence contributes to the development of liquid air energy storage systems. • LNG cold energy is used for air cooling and liquefaction. • Solar energy is used to increase the maximum temperature of direct expansions. • An outstanding electrical round-trip efficiency of 376.7 % is achieved. • Energy capacity reaches 0.125 kWh/kg LNG. • Heat exchanger equipment optimization is priority to improve exergy performance. [ABSTRACT FROM AUTHOR]

Packed-bed latent heat storage (PBLHS) system has been widely studied in the solar energy application area due to its properties of solving the time-space mismatch of energy supply and demand. The paper delves into the cyclic thermal performance of PBLHS tanks, seamlessly integrated with flat-plate collectors, to manage building heat loads effectively. A 1D transient mathematic model of PBLHS integrated with the solar collector for a building is established using MATLAB which is validated with the experimental results from the literature. Based on this model, the effect of different sizes, flow rates, inlet temperature thresholds and different heating months are discussed. The results show that: 1). Building heat load can have a significant influence on the thermal performance of the PBLHS system. 2). The optimal size of the tank for a 96 m2 house is 1.0*1.0 m and the optimal flow rate is 0.05 kg/s 3). The weather data can significantly affect the thermal performance of PBLHS, the storage tank heating durations for one week in different heating months are 108.4h, 73.6h,70.8h and 81.7h. These insights are pivotal for the optimal design of PBLHS tanks, paving the way for more efficient building heating solutions. • PBLHS tank integrated with a flat plate operating under heat load is modelled. • Energetic and thermal performance assessments of a PBLHS tank are obtained. • The cyclic operation of the PBLHS system under long-term intermittent loads is presented. • Influences of different mass flow rates, inlet temperature limits and different size tanks are evaluated. • The operation of the PBLHS system under heating seasons is analyzed. [ABSTRACT FROM AUTHOR]

China's rural solar photovoltaic projects (SPVPs), as an innovative initiative to improve livelihoods through clean energy, have played a positive role in poverty reduction. However, whether this measure can enhance energy services for rural families remains unconfirmed. This paper employs a quasi-experimental method from the perspectives of energy service accessibility and affordability to quantify the net contribution of China's rural SPVPs to enhancing family energy services. The results indicate: (1) SPVPs can significantly improve family energy services, with a net effect of 14.7 % on the energy service accessibility and a net effect of 44.5 % on the energy service affordability. (2) SPVPs can increase the energy consumption capacity, energy supply capacity and energy equipment utilization rate by 2.6 %, 7.1 % and 5 %, respectively. Furthermore, these initiatives can effectively slash the energy costs of rural families by 4.3 %, bolster the energy access affordability by 3.9 %, and catapult energy investments by an impressive 44.9 %. (3) These projects also perform well in the family energy consumption cleanliness. (4) The effect of SPVPs in providing energy services presents a regional difference, with the best performance observed in 'Type III' solar resource areas. Meanwhile, the implementation of China's rural SPVPs does not involve "elite capture." • We analyze the changes of energy accessibility and affordability in rural China. • We quantify the energy services effect of solar PV projects (SPVPs). • SPVPs perform well in improving family energy consumption cleanliness. • The energy services effect of solar PV projects has spatial heterogeneity. • The implementation of China's rural SPVPs does not involve "elite capture.". [ABSTRACT FROM AUTHOR]

Photovoltaic energy is one of the clean and efficient energies which has been developing quickly in the last years. As the penetration of solar plants is increasing in the electricity network, new problems have arisen in network operation. This paper models a high penetration factor of solar energy in the electricity network and investigates the impact of solar energy growth on both the generation schedule of different power plants and in the natural gas transmission network. Fuel management of gas power plants is modeled through simulation of the natural gas transmission network. To this end, an increase in the penetration of solar energy in the electricity network inevitably leads to a sudden increase in the output of gas fired units and a linear and integrated model with the electricity and the natural gas transmission networks has been presented to analyze both of them at the same time to better depict the impact of a high penetration of the solar energy in natural gas transmission grids. In this method, natural gas transmission network and Security Constrained Unit Commitment (SCUC) are presented in a single level program. Gas network constraints are linearized and added to the SCUC problem. The stress imposed on the gas network due to a sudden increase in the load of the electricity network is investigated. Conclusions are duly drawn. • This paper models a high penetration factor of solar energy in electricity networks. • Fuel management of gas power plants is modeled by simulation of natural gas network. • Integrated model of electricity and natural gas transmission networks is presented. • Presenting a single level program for natural gas and security constrained unit commitment. • Studying the stress imposed on the gas network due to high penetration of the solar energy. [ABSTRACT FROM AUTHOR]

Abstract Solar aided (coal-fired) power generation (SAPG) system has been proved to be an efficient way to utilize the solar energy for power generation. Due to the instability of the solar radiation, a SAPG system generally operates under transient working conditions. In this paper, performance simulation sub-models of main components in a SAPG plant are established based on the lumped parameter assumption. A 330 MW SAPG power plant as a case study is simulated. The variations of the performances, main parameters of the plant with the solar field heat output and the dynamic responses under a typical day are analyzed. The results show that when the heat output of the solar field changes from 0 kJ/h to 2.13 × 108 kJ/h, the coal saving rate will increase to 6.4%, and the solar power generation share (the proportion of the power from the solar energy to the total power from the SAPG plant) will increase to 7.74%. During the analysis process, in order to optimize the solar field, the concept of the solar field equivalent efficiency (SFEE) is proposed and the optimal velocity of heat transfer fluid (HTF) in absorber tube is obtained. Highlights • The transient model of a solar aided power generation (SAPG) system is developed. • The concept of solar field equivalent efficiency (SFEE) is proposed in this paper. • The optimal velocity of heat transfer fluid in the absorb tube is obtained. • Performances of SAPG system with different solar field heat output are revealed. • The dynamic responses of the SAPG system under a typical day are analyzed. [ABSTRACT FROM AUTHOR]

Many attempts were made in solar energy to find advanced solar energy technology for solar cell which is with high power conversion efficiency; calculation output current by output voltage using a model of solar cells is very useful for this major aim. Although there are many models can be used to estimate current via voltage from solar cells, no one parameter in the models is a correlation to power conversion efficiency. One simplification of single diode model is proposed in this paper. Not only this model is in form of explicit function, but also one parameter as parallel conductance is correlation to power conversion efficiency. The accuracy of the proposed model is evaluated using thirty experimental data. It was found that in all experimental cases, very good match between measured and calculated is reached. The first important result indicates that power conversion efficiency independent on solar cell connection in series due to parallel conductance independent on solar cell connection in series. The major contribution is that the mathematical relationship between power conversion efficiency and parallel conductance is found in this paper. It is envisaged that the proposed methodology can be a very good route for researchers to discover advanced solar cell. • One simplification of single-diode model is proposed in this paper. • The accuracy of the proposed model is evaluated using twenty-nine experimental data. • Conductance that is responsible for the power conversion efficiency of solar cell. • Power conversion efficiency is quantitatively link to conductance is found. • Good application results are obtained. [ABSTRACT FROM AUTHOR]

Adding propane to CO 2 can improve the thermal efficiency of the supercritical Brayton cycle under high condensation temperatures. Integrating the thermal energy system in a direct-heated solar power tower plant can maximize the thermal utilization of solar energy. In this paper, the thermodynamic model of the plant is constructed, and an operation strategy is proposed to realize round-the-clock operation by flexible scheduling of solar, molten salt, and fossil fuel energy supply. Notably, the potential of adding propane to CO 2 in the plant was analyzed by comparing the off-design performance and the operation behavior under typical days. The results show that the thermal efficiency of the plant using CO 2 -propane is not only 1.63% higher than the original, but also the adequate utilization time of solar energy will be prolonged by 0.3 h. In addition, the hot molten salt filling rate of the CO 2 -propane system is more sensitive to changes with direct normal irradiance. However, the performance of the system will deviate from the optimal design value when the heating mode is switched. The achievements from this paper have testified the CO 2 -propane cycle is better than the initial cycle in the direct-heated solar power tower plant under off-design conditions. The system scheme and operation strategy can be regarded as valuable references for CO 2 -based mixtures application. • The CO 2 -propane is used as working fluid in a direct-heated solar power tower plant. • An operation strategy is proposed to realize all-weather stable operation. • The performance of the plant will deviate from the optimal design value at sunset. • The solar energy adequate utilization time will be prolonged after adding propane. [ABSTRACT FROM AUTHOR]

The paper aims to investigate the system behavior of a solar hybrid microturbine through dynamic simulation, relying on experimental data from existing literature. The focus of this evaluation is on assessing the systems response to changes in solar heat flow from the solar receiver to simulate dynamic operation. By evaluating various simulated operational scenarios, the systems performance was assessed by comparing the minimum, average, and maximum solar heat flow from the solar receiver during regular operation. The main objective of these evaluations is to determine the optimal configuration to ensure safe and efficient system operation. The study shows that the parallel configuration outperforms the serial configuration. Specifically, the parallel configuration achieves a peak thermal efficiency of 37%, while the serial configuration reaches 33%. Additionally, the fuel conversion rate for both configurations rises to over 90% at maximum Direct Normal Irradiance (DNI) and decreases to below 40% at minimum DNI. This studies provide valuable insights into the dynamic behavior and performance of the solar hybrid microturbine system, guiding the selection of the most suitable configuration for optimized operational outcomes. Moreover, the study underscores the importance of dynamic analysis in ensuring efficient and reliable power generation. • A comparison of dynamic operating behavior has been conducted for solar hybrid microturbine. • The impact of serial versus parallel configurations on system performance have been demonstrated. • The performance of the solar hybrid microturbine system has been evaluated under various DNI conditions. [ABSTRACT FROM AUTHOR]

With the increasing proportion of photovoltaic power generation, solar power prediction systems have become more important. Accurate photovoltaic power prediction can assist the grid dispatch department in formulating effective power scheduling plans, improving grid stability and the capacity to accommodate solar energy. To address the challenges in solar power generation forecasting, the paper proposes a new neural network model called Graph Convolutional Random Vector Functional Link (GCRVFL). The output layer of this model includes both nonlinear transformed features from the hidden layer and the original input features, while also considering the spatial characteristics among photovoltaic sites. Furthermore, Singular Spectrum Analysis (SSA) is utilized to decompose the original solar power time series, extracting different component sequences from the photovoltaic power time series. Opposite based learning and cross-mutation are employed to improve the original Equilibrium Optimizer (EO) algorithm, resulting in an Evolutionary Equilibrium Optimizer (EEO) algorithm. The EEO algorithm is employed to optimize the weight threshold of GCRVFL, leading to a novel photovoltaic power prediction model called SSA-EEO-GCRVFL. Through four datasets and eight control experiments, it can be observed that the proposed model achieves the best predictive performance and is capable of fulfilling the task of photovoltaic power prediction. • A novel photovoltaic power prediction model called GCRVFL has been proposed. • SSA has been applied to decompose photovoltaic power data. • EO has been improved by incorporating adversarial learning and crossover mutation. • The weight threshold of GCRVFL is optimized using EEO. [ABSTRACT FROM AUTHOR]

The development of efficient and clean heating technologies is profoundly significant for the reduction of carbon emissions in cold regions. This paper puts forth a novel solar-coupled air source heat pump system integrated with phase change heat storage technology, which is well-suited for regions with such climatic conditions. A numerical model of the components and coupled systems is established using the lumped parameter method, and an iterative method is employed for the computational solution in MATLAB software. A variety of system performance aspects are then simulated and analysed following the configuration of component structural parameters and initial operating conditions. The results of the simulations indicate that an increase in the phase change temperature interval of the phase change materials leads to a higher average heat release power. In particular, a 2 °C increase in the phase change temperature interval results in an increase in the heat release power of over 10 %. Furthermore, when the system is applied in typical cold regions, including Kunming, Hangzhou, Lhasa, and Harbin, the average coefficient of performance is 10.23, 8.87, 8.49, and 7.70, respectively. The proportion of solar energy input contributes to an increase in system efficiency across all regions. A case study of Hangzhou reveals that the incorporation of solar energy into the system results in an increase in efficiency of 70.91 %. This research provides valuable operational methods and site selection recommendations for engineering practices, laying a theoretical foundation for its widespread application in cold regions. • A novel solar-heat pump system with phase change heat storage is proposed for cold region. • Numerical models of system is established and its performance is simulated and analysed. • The melting point of PCM plays a crucial role in heat storage/release performance of system. • System's performance boost 70.91 % due to solar integration in Hangzhou, reaching 8.87. • This research offers valuable insights into system design and site selection in engineering practices. [ABSTRACT FROM AUTHOR]

A new renewable energy-driven advanced plant is designed and developed to produce multiple useful outputs, namely electricity, heat, cooling, hydrogen, and monomethylhydrazine (as space shuttle fuel) using solar and wind energies locally available. A specific location needed for this kind of unique work is identified as the Kennedy Space Center (KSC), which is known as located on Merritt Island, in the state of Florida (USA). It is also one of the National Aeronautics and Space Administration's (NASA) ten field centers. Since December 1968, KSC has been NASA's primary launch center of American spaceflight, research, and technology. This paper presents a comprehensive analysis of the subsystems that constitute the newly proposed system potentially for KSC and highlights their complex relationships and synergies. Leveraging renewable energy sources, such as concentrated solar power (CSP) and wind energy, coupled with the subsystem uniquely, such as the regenerative Rankine cycle, multi-stage flash (MSF) desalination unit, hydrogen production process, and Li–Br absorption chiller, the KSC's system maximizes energy conversion efficiency while minimizing environmental impact. Noteworthy outcomes include daily water production of 177.63 kg/s and hydrogen production of 169.61 kg/day, alongside annual energy contributions of 212,692,688 kWh for CSP and 66,158,552 kWh for wind turbines. More than that, it produces 23.04 kg/s MMH as fuel. Additionally, the overall energy and exergy efficiencies of the system are 30.6% and 33% respectively. Despite challenges, such as low efficiencies in certain subsystems, like mono methyl hydrazine (MMH) production, ongoing research and development efforts aim to optimize processes and enhance sustainability. [ABSTRACT FROM AUTHOR]

Hydrogen emerges as a pivotal energy carrier, shaping the future of the energy landscape. This study explores the potential of utilizing solar energy for green hydrogen production, presenting a promising avenue for low-carbon energy generation. Despite its potential, uncertainties stemming from the intermittent nature of solar energy, demand fluctuations, and economic considerations pose challenges to its widespread adoption. The paper delves into the performance of a power-to-hydrogen system, employing solid oxide electrolyzers to convert electricity from solar arrays into green hydrogen. Two distinct system architectures are proposed: the dedicated configuration, where the owner of the solar array and power-to-hydrogen facilities are the same, and the non-dedicated configuration, where the power-to-hydrogen system purchases solar electricity from the owner of the solar power plant. Simulation results from the case study reveal that the non-dedicated system offers superior economic performance compared to the dedicated system. Considering different hydrogen demand levels and electrolyzer sizes, the levelized cost of hydrogen in the non-dedicated scheme is below 2 $/kg, demonstrating competitive pricing within the realm of renewable technologies. However, solar-assisted green hydrogen faces tough competition with traditional sources of hydrogen production when considering economic aspects. • The effect of component size and demand level on green hydrogen production has been analyzed. • Two scenarios, dedicated and non-dedicated configurations, have been investigated. • The component size has been optimized for various demand levels in both configurations. • Simulation results indicate superior LCOH performance in the non-dedicated configuration. • Solar hydrogen production faces tough competition from conventional technologies in final pricing. [ABSTRACT FROM AUTHOR]

This paper investigates how to improve the utilization of solar energy in concentrated solar power plants for multi-tasked operation, including hydrogen production. In this regard, an integrated energy system with multiple power generation stages is developed to utilize heat from concentrated solar collector with molten salt thermal energy storage system. The two-stage steam Rankine cycle and organic Rankine cycle are used as power generation cycles in order to utilize heat from the molten salt at different temperature levels, which improves source utilization for power generation. Continuous energy supply is considered a crucial challenge for renewables, which can be achieved by diversifying the source or adding energy storage. The current study uses two different energy storage methods to ensure the continuous energy supply to achieve self-sufficiency as well for the community. Hydrogen energy subsystem is the second energy storage within the integrated system, which is the secondary energy storage that is used if heat is not sufficient to drive the power generation cycles. In order to make decisions for a better source utilization, ensure continuous power supply, and facilitate the operations of the components and energy storage subsystems according to the loads and source availability, an operational decision-making strategy is developed and applied within the spreadsheet model. In order to test the proposed system and the developed algorithm, a time-dependent analysis is carried out where hourly community load and hourly source data are employed. The analyses are carried out using the first and second laws of thermodynamics, primarily through energy and exergy aspects. The power cycle can generate power from heat within the temperature range of 160°C and 500°C, in between 6.12% and 37.2% of heat to power energy conversion efficiency. The overall energy and exergy efficiencies of the integrated system are found to be 31.29% and19.71% by considering the average meteorological data. • A new concentrated solar-based integrated energy system is designed. • The community demand and changing source availability are simulated. • The molten salt thermal energy and hydrogen storage options are incorporated into. • The energy and exergy efficiencies are determined annually for each hour. [ABSTRACT FROM AUTHOR]

Offshore floating solar power stations represent a new frontier in energy development. These stations maximize solar energy use, reduce land consumption and promote algae growth. However, moist marine air makes airborne particles like sand adhere more easily to PV panels, reducing photoelectric conversion efficiency and causing overheating and potential damage. Additionally, drones and fixed cameras face challenges due to complex maritime factors and complicating image analysis. To address these issues, this paper proposes an exploratory framework for identifying dust regions on photovoltaic panels specifically for offshore floating solar power stations. The framework aims to address how to accurately and reliably identify dust accumulation on PV panels, even in images with complex background interference. The framework is designed to be compatible with existing image recognition models and incorporates specialized enhancement modules to further improve recognition accuracy and efficiency. In this study, we utilized a dust feature enhancement module based on the HLS color space, combined with Mask R-CNN, to demonstrate the framework's feasibility and effectiveness. Experimental results show that, compared to a single Mask R-CNN, the framework significantly reduces misidentification and omission of dust areas, boosting the confidence level and effectively meeting the operational needs of offshore floating solar power stations. • An exploratory framework to identify dust on photovoltaic panels in offshore floating solar power stations is proposed. • Introduction of PAI as an evaluation metric to more accurately assess the misidentification of background instances. • Validates the limitations of the mean Average Precision evaluation metric under certain specific conditions. [ABSTRACT FROM AUTHOR]

The concentrating solar power (CSP) plant, renowned for its flexibility, environmental friendliness, and energy storage capabilities, has become integral components of large-scale renewable energy projects in China. However, the grid connection methods for CSP plants, wind farms, and photovoltaic (PV) plants are independent. To enhance renewable energy consumption and improve the revenue of CSP and PV plants, this paper proposes a dual-time scale dispatch model for the dynamic operation of the CSP-PV hybrid plant. This model considers the actual startup conditions and dynamic switching models of the subsystems involved in the receiver, thermal storage subsystem, and power cycle. Based on the dynamic operation characteristics of the CSP-PV hybrid power plant, different time scales are used for prediction during day-ahead and intraday periods, improving the efficiency of the hybrid power plant and adapting to weather changes. The dispatch optimization outcomes of the CSP-PV hybrid plant serve as the reported curve for the day-ahead and intraday rolling optimal scheduling process, aiming to minimize the operating costs of the power system. A simulation is conducted to demonstrate the effectiveness of the proposed model, utilizing data from the Dunhuang area, Gansu Province, China. • A dual time scale dynamic operation model for CSP-PV hybrid plants is presented. • The optimal dispatch is integrated with day-ahead and intraday optimal scheduling. • HVDC transmission is considered in power system optimal scheduling. • The optimal dispatch of the CSP-PV hybrid power plant is proved in Dunhuang area. [ABSTRACT FROM AUTHOR]

This paper introduces an innovative integration of geothermal and solar energies to assess the production of power, cooling, and freshwater. These products are achieved through a modified absorption refrigeration cycle, a modified organic Rankine cycle, and humidification-dehumidification subsystems driven by a flash-binary configuration. The performance of the setup is evaluated using both thermodynamic and economic approaches. Additionally, three multi-objective optimizations are applied to determine a suitable optimal state. The approaches reveal net power, cooling, and freshwater production rates of 807.3 kW, 1345 kW, and 7.96 kg/s, respectively. The designed setup requires a total capital investment cost of $2,490,310 and has a payback period of 5.76 years in the base mode. The study highlights that the temperature difference of superheating significantly impacts the total capital investment cost and exergy efficiency, while the cooling production is mainly influenced by the evaporator temperature. The final optimal state achieved an exergy efficiency of 15.98 % and a net present value of $1,999,864. Overall, this innovative hybrid geothermal-solar setup demonstrates a viable solution for sustainable energy production, combining power generation, cooling, and freshwater production in a single integrated system. The findings support the system's potential for real-world applications, particularly in regions with suitable geothermal and solar resources. • Designing a novel multi-generation driven by solar and geothermal energies. • Considering the energy, exergy, and economic analyses for the performance evaluation. • Producing 807.7 kW net power, 1592 kW cooling, and 8.8 kg/s freshwater. • Achieving 15.98 % of exergy efficiency with a payback period of 5.36 years. [ABSTRACT FROM AUTHOR]

Accurately predicting residential solar energy consumption is crucial for efficient electricity production, supply, and power dispatch. However, conventional forecasting methods often struggle to handle complex energy consumption data. In response to this challenge, this study develops a pioneering two-stage error-corrected combined forecasting model that integrates traditional linear methods, seasonal processing techniques, deep learning models, and intelligent optimization algorithms to outperform other combined forecasting methods in terms of performance. This research analyzes the combined weight values, shedding light on why the proposed model consistently outperforms its counterparts. To confirm its superiority, the proposed model and five benchmark models are rigorously tested in this paper using four evaluation metrics and a hypothesis testing method. The empirical results show that the proposed combined model performs well in terms of accuracy and stability. Notably, the average absolute percentage error of its 24-step ahead prediction is 2.9053 %, which outperforms all comparative models, both single and combined model. These results fully illustrate the advantages of the combined model and reaffirm the excellence of its prediction performance in predicting energy consumption. • A novel forecasting combined model is proposed for solar energy consumption. • The proposed combined model outperforms the five benchmark models. • The interpretation of combination weight in the combined model is elaborated. • Four experiments, hypothesis test and multi-step prediction are performed. [ABSTRACT FROM AUTHOR]

The heliostat field of solar power tower (SPT) system occupies a large proportion of both the total investment and total energy losses of a plant. However, the optimization design of a heliostat field is a challenging work, because there are too many parameters to be optimized. In this paper, a new high-dimensional genetic algorithm toolbox (HDGA) is developed in Visual Studio Community 2015 for the heliostat field design, in which a new crossover strategy is employed for the high-dimensional optimization. The algorithm is verified by both mathematical models and engineering cases, the results show that HDGA is more effective for the high-dimensional problem, and its convergence speed is much faster than that of the genetic algorithm toolbox developed by the University of Sheffield (Sheffield GA). The new algorithm is explained in detail and the optimal field layout is presented. With the new algorithm, a heliostat field referencing to the Gemasolar plant is optimized in this paper. The results show that the optical performance of the heliostat field is improved significantly than that of the un-optimized case, and the optical efficiency of 63.7% is reachable at the design point. At the same time, the annual insolation weighted efficiency is 56.9%. [ABSTRACT FROM AUTHOR]

This paper compares different strategies to transform the heating sector into a future 100% renewable energy solution. It focuses on the consequences for infrastructures in terms of grids and storage across the electricity, gas and heating sectors. The hypothesis is that these consequences are rarely taken into proper consideration, even though the costs are significant and differ substantially between the alternative pathways. While the smart grid scenarios are based on electricity as an energy carrier, the “smart energy systems” approach is based on a cross-sectoral use of all grids. Using Denmark as a case, this paper shows how the current gas and district heating grids each have twice the capacity of the electricity distribution grid. Moreover, the existing gas and thermal storage capacities are substantially higher and the additional future capacities are more affordable than within the electricity sector. The conclusion is that the “smart grid” pathway requires a 2–4 times expansion of the electricity grid and significant investments in electricity storage capacities, while the “smart energy systems” pathway can be implemented with relatively few investments in affordable minor expansions of existing grids and storage capacities. [ABSTRACT FROM AUTHOR]

The fossil energy crisis is a great test for human society and the prospect of methanol reforming hydrogen fuel cell technology is of great concern. Higher production cost is also an important factor in limiting the combined cycle power plant. The integrated system enables the overall energy utilization efficiency to improve. Methanol can be made from coal gasification and liquefaction and coal chemical industry has received the attention and support from the state and it is an extremely promising technology. Based on the large scale commercial process simulation software Aspen Plus, this paper constructs a distributed energy system based on solar methanol reforming SOFC which combines GT-ST power generation system with AHP-AR. The results show that the efficiency of SOFC, total electrical efficiency and total system thermal efficiency of the method are 35%, 66% and 90% respectively. In this paper, the performance analysis of SOFC integrated system is carried out which reveals the affinity of solar energy and chemical energy. The results show that the new system increases the power generation and reduces the coal consumption rate. [ABSTRACT FROM AUTHOR]

This paper presented a numerical investigation into a solar/waste energy driven sorption/desorption cycle employing a novel LiCl-Sillicon-Gels adsorbent bed. Several adsorbent materials available for air drying, e.g., silica gel, zeolites, silica gel haloid compound, consolidated composite desiccant, etc., were compared each other, leading to the selection of a most suitable desiccant material (i.e., LiCl-Sillicon-Gels), which has an adequate regeneration temperature of 80 °C and relatively higher moisture absorption capacity of 0.5 g/g. A dedicated adsorbent bed structure was devised to allow both solar radiation and warm air (generated from the waste heat) to pass through to vaporize the water reserved in the voids of the bed. The mass and energy conservation principles were applied to both air and adsorbent within the bed, leading to the development of a specialist mathematical model able to characterize and evaluate the performance of the sorption/desorption cycle. On this basis, the desorption process driven by both solar radiation and waste heat and associated sorption process were simulated side by side. The performance of the sorption/desorption cycle, represented by moisture extraction volume (D me ), moisture extraction/removal efficiencies (ƞ me /η mr ), and dehumidification coefficient of performance (DCOP), and their correlations with the major operational factors, e.g. swapping time of working mode, parametrical data of the process/regeneration air and solar radiation, were investigated and characterized. The results of the research indicated that the system can achieve a good performance (i.e., moisture extraction volume of 7–7.2 g/kg, moisture extraction/removal efficiencies of 0.4–0.5 and 0.5 to 0.57, and DCOP of 0.35–0.37) under a typical wet climatic condition (i.e., 30–35 °C and 70–80% RH). Increasing solar radiation intensity to 1,800 W/m 2 could lead to a significant rise in DCOP (from 1 to 5). Furthermore, the geometrical set-up of the adsorbent chambers/beds and cycle was optimized, giving the recommended air flow channel length of 0.7–0.9 m and air flow turning number of 5–7. The swapping time of the beds in terms of the function is suggested to 2.5–3 h. Compared to the conventional adsorption system, the new system can achieve around 90% saving in fossil fuel energy use. In summary, the paper made first of its kind effort in designing, characterizing and optimizing a novel solar/waste energy driven sorption/desorption cycle with LiCl-Sillicon-Gels as the bed filling material, which would help realization of the sustainable air treatment process in both building and industrial sectors, thus contributing to the energy saving, carbon emission reduction, as well as sustainable development on the global scale. [ABSTRACT FROM AUTHOR]

Organic Rankine Cycle (ORC) is promising in utilizing low-medium thermal energy, and solar energy is widely considered as the most attractive renewable energy for the future. Consequently, electricity production by coupling ORC and solar energy can reduce the fossil fuel consumption and lower the CO 2 emissions over the world. However, the intensity of solar radiation keeps changing throughout the daytime, so it is important to study the daytime performance of solar-ORC system to guarantee a proper operation. Based on the discretized parameter model built in Dymola, dynamic performances of a small-scale power plant driven by parabolic trough collector (PTC) under clear sky and cloudy sky conditions are analyzed in this paper, respectively. The results show that degree of super heat, evaporation pressure and output power are relevant to direct normal irradiance (DNI) and follow the variation of DNI from morning to afternoon. Particularly, this paper pays attention to analyze the system's responses to the cloud blockage using the dynamic model. It shows that short period (5 min) of cloud blockage of the sun poses no severe influence, while the cloud occurring at morning can cause the system to break down easily. In addition, a conventional PID control strategy is considered for the PTC-ORC system under the weather condition of cloudy sky. The optimized system can generate 105.54 kWh and the system without control can generate 84.95 kWh. The generation can improve 24% compared to the system without control. [ABSTRACT FROM AUTHOR]

Integrating solar heat and calcium looping (CaL) process into the existing lignite-fired power generation system is a promising technology to control CO 2 emission. However, the heat released from carbonation process led to the temperature increase of exhaust flue gas together with heat losses in boiler. To recover the waste heat from the exhaust flue gas, this paper proposed a solar-aided lignite-fired power generation system with CaL process CO 2 capture, lignite pre-drying and feedwater preheating (i.e., design III). Besides, design I without waste heat recovery and design II with only lignite pre-drying were simulated for comparison. Through the case study based on a solar-aided 330 MW lignite-fired power generation system, thermal and techno-economic performance of design III was the best on the design condition. Its standard coal consumption rate was 374.44 g/kWh, which was 61.12 g/kWh and 8.24 g/kWh lower than design I and design II, respectively. With the new design, the annual net profit of design III is $18.2924 M, with $0.5652 M higher than design II. The sensitivity analysis indicated that the thermal performance of design III was also the best under various conditions of CO 2 capture efficiency and integrated solar heat. • Solar tower, lignite Pre-drying and Feedwater preheating were integrated with CaL process CO 2 capture. • The new design recovered the waste heat from exhaust CO 2 -lean flue gas caused by carbonation process. • The new design decreased the standard coal consumption rate and increased the thermal efficiency. • The new design was proved economically feasible based on annual net profit. • Sensitivity analysis was conducted to study the influences of CO 2 capture efficiency and integrated solar heat. [ABSTRACT FROM AUTHOR]

The photovoltaic double skin façade (PV-DSF) is a cutting-edge building envelope renowned for its dynamic nature and power generation capabilities, which attracts substantial scientific attention. However, the current lack of experimental support makes it challenging to draw definitive conclusions about the influence of façade material. This study aims to address this gap by investigating the energy performance of PV-DSF with different façade materials, thereby establishing an empirical foundation for its optimization. In this regard, the full-size comparison experiments on PV-DSF with 20/40% photovoltaic (PV) glass as external façade and laminated/double glass as internal glass were conducted in Harbin, China. The EnergyPlus software is adopted for the simulation of lighting energy consumption. The results indicate that PV-DSF with 40% PV outperforms that with 20% PV, leading to significant reductions in total energy consumption in both summer (22.73%) and winter (16.84%). The double glass can prevent 0.49 MJ of total heat gain in summer, which is accompanied by a marginal 0.03 MJ increase in winter energy consumption. In total, for optimal annual performance, 40% PV and double glass are recommended as the façades of PV-DSF. The results of this investigation can provide an experimental foundation for PV-DSF optimization in sustainable building design. • This paper presents the semi-experimental study on photovoltaic double skin façade. • The impact of façade material on the net energy-saving performance is studied. • The 40% photovoltaic (PV) glass outperforms 20% PV glass in both summer and winter. • The double glass possesses great advantage in summer, with a tiny short in winter. • From the view of year-round operation, 40% PV and double glass are recommended. [ABSTRACT FROM AUTHOR]

Given the cascade utilization of photon energy, concentrating spectral beam splitting hybrid conversion technology is one of the state-of-the-art solar energy harvesting schemes. In this paper, a novel photovoltaic-thermochemical hybrid system based on a Cassegrain concentrator is proposed for ameliorating optical efficiency and thermochemical conversion under spectral splitting. On this basis, solar energy penetration is improved by concentrating optimization and reactant flow regulation. A specially developed splitter is used to allocate different radiation bands, allowing for the thermochemical storage of photovoltaic loss at mid/low temperatures. The mathematical method covering ray tracing, parameter optimization, solar multi-effect conversion process, and evaluation is constructed and verified, by which the optical characteristics, thermodynamic regulation, and economic feasibility are quantitatively investigated. The results show that the optical efficiency of 79.2% can be obtained by multi-objective optimization considering the uniformity of energy flux and the deviation of ray incidence angle for the first time. With the assistance of the reactant flow strategy, the hybrid system has a solar-product conversion efficiency of more than 36.4% and a stable exergy conversion capacity under different irradiance conditions. Moreover, the system demonstrates a potential investment return and a controllable levelised cost of electricity. In summary, the research results will contribute to the feasibility of full-spectrum solar absorption and the applicability of dish concentrators in distributed scenarios. • Cassegrain concentrator exhibits impressive adaptability in the SBS hybrid system. • Optical optimization and reactant regulation boost solar energy penetration. • Photon cascade allocation enables energy level enhancement and storage. • Potential for high-grade energy conversion and financial viability is demonstrated. [ABSTRACT FROM AUTHOR]