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In this paper, indium tin oxide (ITO) nanoparticles and four different indium tin oxide–ethylene glycol (ITOEG) nanofluid optical filters are prepared and experimentally tested. The XRD and TEM measurements of indium tin oxide nanoparticles are launched, spectral transmittances of pure ethylene glycol and four different ITOEG nanofluid materials are tested, and the beam splitting behaviours of the four different nanofluid optical filters are compared. The results show that the nanofluid consisting of 15 mg indium tin oxide and 200 ml ethylene glycol has a relatively better overall beam splitting behaviour. For the full spectrum, its average transmittance and absorbance are 69.1% and 30.9%. A novel PV/thermal system is proposed and its performances are evaluated when the ITOEG nanofluid is assumed to be utilized. The results show that the overall optical efficiency of the PV/thermal system is 93.6%. When the north–south sun-tracking error increases to 0.2°, the overall optical efficiency of the system decreases to 90.1%. That means the PV/thermal system has a relatively good adaptability to the sun-tracking error. The operation behaviour evaluation results reveal that the theoretical overall PV and solar thermal efficiencies of the PV/thermal system are 17.7% and 18.5%.

The evolutionary game theory method has been widely used in the research works about different kinds of energy utilization fields, especially the clean energy utilizations which can facilitate the sustainable energy development. This paper presents a research review of the evolutionary game theory (EGT)-based studies on different energy-related aspects, including the traditional energy utilizations, energy saving and carbon emission reduction, new energy utilizations, new energy vehicles, electric power market, distributed energy systems, micro-grid, smart grid and energy storage. Typical research works based on the evolutionary game theory method and relevant algorithms are introduced and summarized. To promote the sustainable developments of energy utilization technologies as well as the usage of evolutionary game theory method, typical existing problems and several general recommendations about the further EGT-based research works are also proposed. The potential further works based on the evolutionary game theory approach may include the EGT-based studies considering more complex initial conditions and influential factors, verifications of the applicabilities and feasibilities of the evolutionary game theory method based on practical examples, research works with evolutionary game models consisting of more participants, and research and development (R&D) works of new EGT-based or hybrid algorithms.

This study aims to find a feasible photovoltaic/thermal (PV/T) utilization method based on film-based beam splitting technology. In contrast with previous studies, the main novelty of this paper is proposing the design of an innovative PV/T system using both parabolic trough concentrator (PTC) and film-based beam splitter (FBS). The design approach of the PV/T system is presented. A new FBS used for this PV/T system is designed by using the Needle method, and its average reflectivity and transmissivity are 27.2% and 72.8%. By using Ray Tracing and Computational Fluid Dynamics (CFD) simulation methods, the performance evaluation of the PV/T system is conducted. The evaluation results reveal that when the East-West sun tracking error is 0.2°, the optical efficiencies of the photovoltaic module and the solar thermal collector tube (TCT) can be kept at 95% and 93.9%. Moreover, when the heat transfer fluid (HTF) in the TCT is selected to be the ethylene glycol, the operation analysis results demonstrate that the photoelectric efficiency of the photovoltaic module is 25.4% and the thermal efficiency of the PV/T system is 17.24%. The thermal performance of the system can be improved when the HTF flow velocity is increased properly or when the inlet HTF temperature is decreased. The technical feasibility of the proposed PV/T system can be revealed from the analysis results of this study.

Abstract Solar power generation is an effective approach to promote the achievement of carbon neutrality. Heat transfer materials (HTMs) are important for concentrated solar power (CSP) systems and their accessary thermal energy storage (TES) devices. The performances of HTMs can influence the operation behaviors of CSP systems and TES devices. On the whole, the HTMs can be divided into three categories according to their physical states, which are the liquid, gaseous, and solid HTMs, respectively. This article presents a brief review of research works on liquid HTMs used in CSP systems and TES devices of CSP systems, mainly including different kinds of molten salts, heat transfer oils, nanofluids, liquid metals, and water. Some typical practical applications, experimental and simulation studies on different kinds of liquid HTMs used in CSP and TES systems are introduced, and the advantages, disadvantages, and further research and development work prospects of different kinds of HTMs are briefly summarized. This article aims to providing a reference for researchers in solar thermal power field.

This study aims at proposing a public-private partnership project including the government (GOVT), coal-fired power plant (CTPP) and solar photovoltaic power plant (PVPP) toward carbon emission reduction and neutralization in China. The project is formed using the CO2 capture and utilization (CCU) and solar PV hydrogen production technologies. When all the participators cooperate, the influence of typical factors on the project is evaluated using the evolutionary game theory method. The results show that increasing the CCU subsidy can strengthen the participating intention of the CTPP but will reduce that of the GOVT. Improving the green electricity subsidy can strengthen the participating intention of the PVPP but will decrease that of the GOVT. To ensure the smooth running of the project, a relatively higher carbon emission penalty and a higher sales price of methanol should be ensured, the PVPP should control its daily working hours appropriately, and the proportion of electricity quantity of the PVPP used for hydrogen production should be increased. In this study, the suggested ranges of CCU and green electricity subsidy coefficients are 0.03–0.05 $/kWh and 0.0035–0.0045 $/kWh, the carbon emission penalty coefficient should be greater than 11 $/t, and the suggested range of daily working hours of the PVPP is 7–8 h.

Liquid metals are good potential heat transfer materials for thermoclinic heat storage (THS) systems and will play an important role in the next generation solar thermal power system with higher operating temperature. This paper presents a comparative research work on the charging, discharging and mechanical performances of THS tanks based on four different liquid metal materials, which are lead (Pb), lead-bismuth alloy (PbBi), sodium (Na) and sodium-potassium alloy (NaK). The analysis results indicate that for both the charging and discharging processes, the lead-based THS tank can have the shortest operating duration, largest charging and discharging quantities (9.78 × 109 J and 9.21 × 109 J) as well as the highest discharging efficiency (94.17%), revealing its best operating performance. Relatively acceptable operating performances of lead-bismuth-based and sodium-based THS tanks are also demonstrated. Furthermore, in contrast with other three liquid metals, the lead-based THS tank also has the best mechanical performance. It has the smallest peak maximum mechanical stress of the steel wall (58.6 MPa). In summary, the lead-based THS tank has both the best heat storage and mechanical performances.

This paper presents a comparative analysis of thermal and mechanical behaviors of the thermally stratified heat storage system using three different heat transfer materials, which are the binary nitrate salt, ternary nitrate salt and liquid lead–bismuth eutectic (LBE) alloy. The discharging behaviors of the tank using three different heat transfer materials are investigated by using both the algebraic and numerical models. For all the three materials, the algebraic results are consistent with the simulation ones. During the discharging process, in comparison, the thermal stratification thickness of the tank using the binary nitrate salt is relatively smaller, which can lead to a better discharging performance. The comparison results of expanding behaviors of the standby tank reveal that the thermal stratification thicknesses of tanks using the three different heat transfer materials all increase with the standby time increased. Compared with the other two materials, the thermal stratification thickness of the tank using the binary nitrate salt is the smallest at the same standby time. The comparison results of mechanical behaviors of the tank demonstrate that the maximum mechanical stress of the tank using the liquid LBE is the greatest, while the tank using the molten salts can have better mechanical properties.

Thermocline sensible heat storage (SHS) systems are usually utilized in parabolic trough solar power systems. Liquid lead–bismuth eutectic (LBE) is a potential heat transfer medium for SHS systems, but its influences on the performances of SHS systems are rarely studied. In this study, a simulation model of thermocline SHS tank using liquid LBE as the heat transfer fluid is established, and the influences of initial cold and hot LBE temperatures on the operation and mechanical performances of the tank are estimated. The results reveal that when the liquid LBE is used as the heat transfer fluid, the SHS tank can operate stably. The initial cold LEB temperature has almost no influence on both the total heat storage and heat release durations of the tank, while the initial hot LBE temperature has proportional relationships with the total heat storage and heat release durations. The heat storage performance as well as the heat release behavior of the tank can be improved by increasing the initial cold LBE temperature, or by decreasing the initial hot LBE temperature. The peak maximum mechanical stress of the tank can be decreased by increasing the initial cold LBE temperature, or by decreasing the initial hot LBE temperature.

This study presents the design and performance evaluation of a novel concentration photovoltaic/thermal (PV/thermal) system based on parabolic trough concentrator and indium tin oxide-ethylene glycol (ITOEG) nanofluid spectral filter. The overall design principle of the PV/thermal system is introduced, and the ITOEG nanofluid spectral filter is prepared and experimentally tested. For the full spectrum, the average transmittance and absorbance of the nanofluid spectral filter are 69.1% and 30.9%. The optical behaviour evaluation results reveal a double-peak radiation flux density distribution on the nanofluid channel bottom surface as well as on the solar cell module surface. When the north-south sun-tracking error increases to 0.2°, the optical efficiency of the PV/thermal system decreases to 93.7%. That means the system has a relatively good adaptability to the sun-tracking error. The thermodynamic analysis results reveal that the theoretical photoelectric conversion and solar thermal efficiencies of the PV/thermal system are 29.1% and 17.2%. The thermal efficiency of the PV/thermal system can be increased by increasing the nanofluid inlet flow velocity or by decreasing the nanofluid inlet temperature properly.

This study proposes a novel hybrid solar-gas power and hydrogen-production system, which is comprised by the solar tower thermal system, gas-steam turbine combined cycle and organic Rankine cycle-based hydrogen-production system. Based on the Ebsilon code, the operation processes of the hybrid system are simulated. The results show that the output power and electric efficiency of the hybrid system are 103.9 MW and 41.3%, and the daily hydrogen output is 62.2 kg. The operation simulation results of the hybrid system reveal that the gas-steam combined cycle and solar island can both achieve stable operations, and the power generation section and hydrogen-production device can both work effectively, which means the hybrid system is technically feasible. The exergy estimate results of the hybrid system show that the combustion chamber and solar receiver have the two largest exergy destructions, which are 56.5 MW and 45.3 MW. That means the performances of the two components can be further improved. For the hydrogen-production system, the exergy destructions of the proton exchange membrane electrolyzer, turbine, condenser and evaporator of the organic Rankine cycle are 0.156 MW, 0.111 MW, 2.338 MW and 1.891 MW, and the corresponding exergy efficiencies are 51.2%, 92.6%, 80.7% and 79.5%, respectively.

This paper presents a numerical study on the heat transfer performance of U-shaped double-pipe heat exchanger for the concentrated solar power system. The effects of the mass flow rate, temperature and pressure of inlet super-critical CO2 are evaluated. The results show that due to the effect of centrifugal force, temperature and flow velocity distribution divergences happen in the elbow part of the double-pipe. That can enhance the heat transfer performance. With the inlet super-critical CO2 mass flow rate increased, the convection heat transfer coefficient and Nusselt number of the super-critical CO2 both increase. When the inlet super-critical CO2 mass flow rate increases to 0.6 kg s−1, the maximum local average convection heat transfer coefficient and Nusselt number of the super-critical CO2 are 7120.0 W m−2K−1 and 1892.7. By increasing the inlet super-critical CO2 temperature or pressure, the convection heat transfer coefficient of the S–CO2 can be increased. With the inlet super-critical CO2 temperature increased from 700.0 K to 780.0 K, the maximum local average convection heat transfer coefficient of super-critical CO2 increases from 5034.5 W m−2K−1 to 5149.1 W m−2K−1. Compared with the other two parameters, the effect of inlet super-critical CO2 pressure on the heat transfer performance is relatively smaller.

This paper presents an effect evaluation of initial hot molten salt temperature on behaviours of a thermally stratified latent heat storage (LHS) tank using phase change material (PCM) capsules. The influence of initial hot molten salt temperature on the heat storage, heat release and mechanical behaviours of the LHS tank are evaluated. The simulation results show that the initial hot molten salt temperature has relatively great influences on both the heat storage and heat release behaviours of the LHS tank. A higher initial hot molten salt temperature can reduce both the thermocline thickness and total heat storage duration of the tank in the heat storage process, and can increase the maximum heat storage and heat release powers, final effective heat storage and heat release quantities and peak maximum mechanical stress of the tank. When the initial hot molten salt temperature reaches 873.0 K, the peak maximum mechanical stress of the tank is 141.7 MPa. Therefore, to achieve a better operation behaviour of the LHS tank, the initial hot molten salt temperature should be appropriately increased while ensuring that the peak maximum mechanical stress of the tank does not exceed the yield stress and a certain margin can be kept.

The heat transfer fluid material can affect both the behaviors of a heat storage tank. Based on the Fluid-Solid Coupling method, the influences of five different heat transfer fluids on the thermal and mechanical behaviors of the thermally stratified tank are estimated in this paper, including the binary nitrate (KNO3+NaNO3), binary chloride (KCl + MgCl2), ternary nitrate (KNO3+Ca(NO3)2+LiNO3), liquid lead-bismuth eutectic (LBE) and liquid sodium. The simulation results demonstrate that for the charging process, the tank using the ternary nitrate has the best operation behavior, while for the discharging one, that utilizing the binary nitrate has relatively better operation behavior. The standby behavior comparison results indicate that the thermocline stability of the ternary nitrate is the best, but the tank employing the binary nitrate has the smallest cumulative total heat loss. The mechanical performance comparison results show that the binary nitrate salt and binary chloride salt can lead to the smallest and largest maximum mechanical stress of the tank, which are 96.6 MPa and 168.8 MPa. Therefore, the tank utilizing the binary nitrate has the best mechanical behavior.

In this paper, a novel parabolic-trough solar and gas combined (PSGC) system is proposed to explore a new potential utilization approach of solar energy. The working principle of this PSGC system is introduced. The operation behavior estimate and exergy analysis of the system are conducted. The results show that this PSGC system has an output power of 96.1 MW and an efficiency of 45.8%. The solar heat-to-electric efficiency is 21.6%. As the solar intensity augments, the output power as well as the proportion of the solar energy increases. The maximum exergy loss and minimum exergy efficiency both occur in the parabolic-trough-based solar direct steam system (SDSS), which are 30.5 MW and 30.75%. The exergy loss and exergy efficiency of the SDSS both increase as the solar intensity increases. With the solar intensity increased, for the steam turbine (ST), the exergy loss in the high-pressure ST decreases, the exergy loss in the low-pressure ST increases, and the exergy efficiency variations in the high- and low-pressure STs are both very small. The economic analysis results indicate that the PSGC plant is economically feasible and its net present value and internal rate of return are 447.94 million yuan and 19.5%, respectively.

The central shaft is an important and indispensable part of a small scale urban vertical axis wind turbines (VAWTs). Normally, it is often operated at the same angular velocity as the wind turbine. The shedding vortices released by the rotating shaft have a negative effect on the blades passing the wake of the wind shaft. The objective of this study is to explore the influence of the wake of rotating shaft on the performance of the VAWT under different operational and physical parameters. The results show that when the ratio of the shaft diameter to the wind turbine diameter (α) is 9%, the power loss of the wind turbine in one revolution increases from 0% to 25% relative to that of no-shaft wind turbine (this is a numerical experiment for which the shaft of the VAWT is removed in order to study the interactions between the shaft and blade). When the downstream blades pass through the wake of the shaft, the pressure gradient of the suction side and pressure side is changed, and an adverse effect is also exerted on the lift generation in the blades. In addition, α = 5% is a critical value for the rotating shaft wind turbine (the lift-drag ratio trend of the shaft changes differently). In order to figure out the impacts of four factors; namely, tip speed ratios (TSRs), α, turbulence intensity (TI), and the relative surface roughness value (ks/ds) on the performance of a VAWT system, the Taguchi method is employed in this study. The influence strength order of these factors is featured by TSRs > ks/ds > α > TI. Furthermore, within the range we have analyzed in this study, the optimal power coefficient (Cp) occurred under the condition of TSR = 4, α = 5%, ks/ds = 1 × 10−2, and TI = 8%.

In this paper, the theory of aerodynamics and NACA series airfoil is used to analysis Darrieus type vertical axis wind turbine of wind heating system after setting up the relevant structure parameters. Through reasonable correction, the curve of wind energy utilization coefficient of wind turbine is obtained. According to the operating characteristics of wind turbine, the reliability of the wind energy heating system installed in certain area is analyzed. At the same time, the system configuration suggestions are put forward. Based on the curve of wind energy utilization coefficient, Description of variable speed operation of wind turbine will effectively improve the efficiency of wind energy utilization. [ABSTRACT FROM AUTHOR]

Based on basic equation and boundary layer theory of pneumodynamics, the thesis conducts numerical modeling and theoretical analysis on the last stage of turbine characteristics at a small volume flow by using FLUENT, gives an emphasized analysis on the position of first occurrence of backflow and its expansion direction and comes up with flow structure of the turbine flow field at last stage in the small volume flow condition. In connection with specific experiments, it puts forward the flow model of backflow occurring in the last stage field and the solution to the model. The flow field at last stage for a 100MW turbine in the small volume flow condition that is calculated by using the model is basically in conformity to the actual result. [ABSTRACT FROM AUTHOR]