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A controllable heat-driven swirling wind turbine system was integrated with a photovoltaics (PV) system for energy generation in a heat-collecting shed. This is a brand-new type of a wind energy generation system; and a helical three-blade structure in a vertical axis was introduced. The stationary pre-rotation vanes have a variable diameter and a helical twist angle of 225°. A numerical simulation was conducted to investigate the feasibility of a wind turbine blade structure for efficient energy output for industrial application. The computational fluid dynamics (CFD) tool OpenFOAM was used to simulate the operating conditions of the wind turbine. The findings illustrated the efficacy of the new system. The new helical blade structure is efficient for wind energy output of the turbine in a swirling wind field. The simulation under different heat source temperatures illustrated that an increase in heat source temperature could increase the output efficiency of the wind turbine energy system. The increment in output efficiency could be up to 19.07% when the temperature rises from 40 K to 80 K. The PV-swirling wind integrated system was shown to be more economical than a single solar photovoltaic system because its investment payoff period could be shortened by 2 years.

The paper presents the analysis of the small hydropower plant working at variable speed. The hydro-set that consists of the guide vanes and propeller turbine integrated with the permanent magnet synchronous generator is simulated by using Computational Fluid Dynamics (CFD) in Ansys Fluent v18.0. The important part of the paper is the analysis of the mechanical power losses in the hydro-set gap. The analytical and numerical calculations show that these losses are significant and have to be considered in performance calculations. The k-e and k-ω SST models, as well as the one-equation Spalart-Allmaras (SA) model, were tested and verified on the experimental hydropower plant of 75 kW power. The comparison showed that the best agreement with experimental results provides the Spalart-Allmaras model.

In this paper, a modification of a simple gas turbine into the Brayton cycle with regenerative heating, using turbine extraction at intermediate pressure, is presented. The main concept of the retrofitting is based on the transfer of heat from the turbine exhaust gases to the air entering the combustion chamber. The extracted gas transfers heat to air via the divided regenerative heat exchanger and after that is compressed and mixed with additional air. The efficiency gain is dependent on the extraction intermediate pressure and the extraction mass flow rate. The mathematical model of the proposed cycle and its implementation in an in-house code termed COM-GAS is presented. This zero-dimensional robust model allows the prediction of basic parameters such as temperatures, combustion composition, efficiency, and other related factors. Numerical simulations of both basic models with either semi-perfect or real gases based on thermodynamic tables were compared with available exploited data, and differences between this study and others did not exceed 5%. Contrarily, differences between gas turbine cycle with regenerative heating are visible between the two models. In particular, when using the coupled classical regeneration with regeneration according to Szewalski's idea, the integrated cycle efficiency could be significantly increased up to 39.5%.

In this paper theoretical analysis of an ocean thermal energy conversion (OTEC) system was conducted using the Rankine cycle based on the first law of thermodynamics and a mathematical model of components of the system was established. Efficiencies of six types of working fluids were evaluated and compared under the uniform conditions. Finally a 15 kW OTEC plant using the Rankine cycle was constructed and change rules of the thermal cycle efficiency were obtained with various parameters. The results show that by using the Rankine cycle R717 is “the most suitable” for an OTEC system among the selected working fluids. Thermal cycle efficiency initially increases and then decreases with increasing turbine inlet pressure; maximum thermal cycle efficiency was achieved when the turbine inlet and outlet temperature are fixed. Thermal cycle efficiency was 3.2% when the turbine inlet pressure was 0.85 MPa under calculating the conditions. The thermal efficiency decreased with an increase of the condensing temperature under the same turbine inlet pressure. The consistency between the experiment and theoretical results was verified; the experimental value was lower than the theoretical. Meanwhile, this work can provide design data for an OTEC plant and operating experience for an OTEC system was obtained.

Different sCO2 cycle concepts together with a newly proposed cycle configuration were simulated and a comparison was conducted to show the advantages and disadvantages of each cycle considered here. The cycles were compared using a wide range of the turbine inlet temperature, while alternating the used cooling system (air vs. wet cooling systems). The thermodynamic and cost inefficiencies within the simulated cycles were identified using exergoeconomic evaluation methods. The high exergy destruction costs in coolers indicate that the investment cost should be reduced by using different material than titanium due to its high cost. Also, the calculated product cost demonstrates a potential advantage of the proposed cycle. The analysis showed, in general, that sCO2-based cycles are promising for various applications, resulting in system efficiencies and costs that could compete with conventional power generation technologies soon. The sCO2 recompression concept and the novel sCO2 cycle showed the best results among all investigated sCO2 cycles.

This study analyses the aerodynamic performance of two unidirectional-radial-air-turbine configurations; inflow and outflow. These turbines were studied as the Power-Take-Off unit for application on a vented-OWC and a conventional-bidirectional-OWC with a twin-turbine topology, forming four different turbine-OWC configurations. These configurations were evaluated in terms of full-scale power extraction using extrapolated hydrodynamic experimental data of irregular waves for a King Island test site. The power extraction capacity was evaluated by defining a lower and upper bound of power generation under fixed and controlled-RPM schemes and the energy produced in each configuration was then compared against a state-of-the-art twin-rotor turbine. It was found that the difference between these power extraction bounds was lower in case of the outflow turbine, which shows this turbine is less sensitive to RPM variations than the inflow turbine. In addition, due to its lower resistance to the flow in direct mode, the outflow turbine has a smaller full-scale size than the inflow turbine. It was concluded that the outflow turbine provides better efficiency in a twin-turbine-OWC system, while the inflow turbine yields higher conversion efficiency in a vented-OWC system. The vented OWC equipped with a radial inflow turbine can obtain comparable power to the bidirectional OWC system.

When the small modular reactor (SMR) operates off-grid, the load following demand increases. To solve this problem, a flexible load is used to compensate the electricity load. The flexible load comprises power-consuming systems that can change their load actively, such as district heating, desalination, hydrogen production, and other industrial heat supply systems. Based on the modeling of the nuclear steam supply system, turbine, and flexible load, a simulation platform is established in the MATLAB/Simulink environment. For the load following to be compensated by the flexible load, the key problem is dynamic load allocation, in which the electricity load is divided into a moderate part and fluctuating part. The two parts of the load are undertaken by the SMR and flexible load, respectively. Based on the characteristics of different flexible loads, the changeable flexible load and fluctuating flexible load are presented. Two load following control methods are presented for the two types of flexible loads. The simulation results show that the present method can not only relieve the load following burden of the reactor core but also provide steam with stable quality to the flexible load, thereby improving the flexibility and efficiency of the SMR.

This paper presents the concept of compressed air energy storage (CAES) system with Partial Oxidation Gas Turbine (POGT) technology. In this type of turbine fuel is oxidized with an excess air coefficient λ of less than 1.0. Therefore, a given value of the turbine inlet temperature (TIT) can be reached at significantly lower air consumption. POGT products are electric power and combustible process gas that can be utilised in various ways. In this paper there is assumed a bottoming process, which consists of low pressure combustion and a secondary turboexpander. The system is considered to be functioning in power-to-power mode. However, POGT creates also other opportunities that can help improve flexibility of energy market. As the paper presents an initial study of possibilities the proposed system has been compared against the existing plant in Huntorf (Germany). In this way main differences as well as advantages and limitations of the proposed solution are compared against the existing conventional first generation CAES facility. The study is focused mainly on key thermodynamic parameters and potential performance improvement of the CAES process. The results revealed considerable round-trip efficiency gains.

In this paper, a transient model is developed to simulate the start-up operation of an industrial twin-shaft gas turbine based on real geometry and control logic. The components’ characteristic curves of the studied gas turbine were generated with the aid of CFD simulation tools and according to the real geometry of each component. The control logic of the studied gas turbine was simplified and coupled with the developed engine performance model. Also, the gas turbine actuators including variable inlet guide vanes, compressor bleed valves, and fuel valves were simulated so that their concurrent effects on the gas turbine transient behavior can be captured precisely. Moreover, the air-cooled compressor turbine was modeled with a new approach. The integrated model was set up and then tuned with the field data in the base load condition. Next, the start-up operation of the gas turbine from zero speed to the base load condition was simulated and validated with the field data. The results show good agreement between the model outputs and field data. Regarding the model outputs, it can be used as the base code for a more comprehensive investigation of flexibility, operability, and the life concerns of this type of gas turbines.

Tidal current energy is a promising renewable energy resource. Full scale tidal current turbines (TCT) have been deployed all over the world. To verify the design methods of large TCTs with high reliability and efficiency, a 600-kW tidal current turbine was designed and tested in this study. This turbine consisted of a two-blade rotor, a low speed ratio gearbox and a medium speed generator. The turbine was grid-connected through a full-rated converter, and its speed was controlled to capture the maximum power. First, to reach high turbine performance, system design details and maximum power point tracking (MPPT) control strategy were considered. Then, the 600-kW turbine was manufactured, and an onshore test was carried out to test power transmission and control performance. The power performance of the blades and control system were further tested in the sea trial carried out in Zhoushan. Good agreement was obtained between theoretical analyses and test results. Finally, to ascertain causes for observed power fluctuations, the power spectral density (PSD) was analyzed; the results indicated that power fluctuations may be due to stream shear.

This paper analyses the effect of a mean shear similar to an atmospheric boundary layer on the wake of a wind turbine by means of Large Eddy Simulation. More specifically, a comparison is made between the wake in the presence of a smooth boundary layer and that in the absence of a boundary layer (i.e., an unconfined uniform incoming flow). The numerical simulations show that the presence of a smooth boundary layer lowers the power output, however, the rings of tip vortices in the presence of a power-law incoming flow are more stable than for a uniform incoming flow. More importantly, the length of the wake region for the case with the smooth boundary layer is about 12D, which is much shorter than for a uniform incoming flow (namely 20D). Strong downwash, observed at this distance in the presence of a smooth boundary layer, results in a higher velocity magnitude and lower turbulence in the far wake of the wind turbine when compared with a uniform flow. A mechanism explaining these observations is also proposed. This new knowledge may result in denser wind farms, compared with wind farms established on smoother surfaces.

The environment-friendly development of wind power is complicated as the atmospheric impacts of wind farms are difficult to measure. Wind power has made contributions to emission reduction, but it is undeniable that the substantial wind farms (SWFs) have had a non-negligible impact on the local ABL. This paper aims to provide a reliable methodological scheme and practical data for human beings to objectively understand the development of wind power. Based on the data from one of the Chinese gigawatt-scale wind power bases in Zhangbei County of Hebei Province, the mesoscale simulations were conducted to explore the impacts of substantial wind farms on the local and regional atmosphere. The results show that: (i) the impact of substantial wind farms on the local area is significant and sustained, while this impact on the regional area is slight and occasional; (ii) it can bring about the seasonal and diurnal differences in the local ABL property; (iii) it can not only induce the horizontal turbulence directly caused by wind turbine wake flow, but also produce the vertical mixing in the near-surface ABL. A systematic analysis of wind power potential and its atmospheric impact is urgent to ensure sustainable development of wind power.

The basic objective of wind farm layout optimization is to maximize the energy produced by wind farms. However, when wind turbines are arranged in a limited space like an onshore wind farm, specific wind turbines may have greater wake exposure than other wind turbines. This phenomenon can be conspicuous in a mixed layout that consists of turbines with different capacities and hub heights. In this study, we developed and tested a new objective function to increase wind farm energy output while making the wake loss of each wind turbine uniform. The purpose of this function is to adjust the wake effects of all of the wind turbines on a wind farm to similar levels, thereby promoting the operational stability of all of the wind turbines. Layout optimization was performed using a simulated annealing algorithm, which is a heuristic method, with actual wind conditions for an existing wind farm in operation. Then, the results obtained using the proposed method were compared with those yielded by layout optimization for energy maximization. The layout generated using the proposed objective function had lower energy output than that obtained by energy maximization. However, this difference was small and the proposed method prevented wake effect concentration on specific turbines by making the wake effect levels uniform.

This paper proposes a systematic method that precisely estimates the capacity factor (CF) of the variable-speed wind turbine (WT) by considering the coupled influence of the turbine operation constraints and the air density. To do so, the WT’s operation is defined by introducing the QN-curve (denoting the generator torque versus rotor speed), and the influence of different QN-curves on the power production is analysed while considering the influence of the air density. Then, a practical power-curve model considering the constraint of the QN-curve is derived for the WT. Following that, the formulation and the procedure of CF estimation are presented. Lastly, the presented CF estimation approach is applied into an industrial WT while considering the wind sites with four different altitudes. Finally, the application results show the capabilities of the proposed approach in evaluating the CF under the coupled influence of the QN-curve constraint and the air density. Meanwhile, comparing the proposed approach to four empirical approaches demonstrates that the CF estimation based on empirical models has considerable deviations to the results of the presented model under different site altitudes. Furthermore, among the four empirical models, the CF estimations from the quadratic and the linear models present the least deviations to those by the proposed model at the sites with low altitude and high altitude, respectively.

In the supercritical CO2 recompression Brayton cycle, recuperators play an important role in cycle efficiency and operating performance. In this work, a dynamic model of the supercritical CO2 recompression Brayton cycle is developed. The effects of high-temperature and low-temperature recuperators on the dynamic characteristics of the cycle are examined. It is found that cycle parameters, including temperature, power, and cycle efficiency, exhibit sinusoidal variations like the source signal provided by the hot-side inlet temperature of recuperator. The transient responses in different locations of the cycle have different amplitudes and phases. The source signal with amplitude of 12.5 K at the hot-side inlet temperature of the high-temperature recuperator causes power variations of 10, 1, and 1.3 kW, respectively, in the turbine, main compressor, and recompressor, while the maximum variance of the cycle efficiency is within 1.57%. When the amplitude at the hot-side inlet temperature of the high-temperature recuperator is changed to 25 K, variances in the cycle efficiencies, powers, and temperatures, respectively, nearly double in the turbine, compressors, and recuperators. When two source signals are added to the cycle, the phase of the cycle efficiency well matches each phase of the two individual source signals.

The reliability of power systems, in terms of uninterrupted electricity supplies, is dependent on the reliability of the system's elements, especially the generation sources and transmission lines. The reliability of a coal-fired power unit's operation is essentially affected by the unit's main components, i.e. the turbine, the boiler and the generator. According to the statistics, the boiler is the most failure-prone element of the power unit. Therefore, efforts aimed at improving the reliability must include actions that enable early diagnostics of the state of the individual devices. In this paper it has been proposed that the optimal time to perform diagnostic testing of boiler tubes should be determined using risk analysis. Using the net present value (NPV) discounted cash flow index and the avoided risk criterion, a procedure has been put forward that optimizes the time when diagnostic tests should be carried out. The method has been applied to optimize diagnostic testing of boiler tubes, where corrosion is the principal cause of damage. Methods have also been given to determine the probability of the failure of such elements.

Structural simplification and efficient hydraulic performance are key to effectively utilizing ultra-low head water power resources and reducing hydroelectric unit costs. In this study, a computational fluid dynamics (CFD) method was used to predict hydraulic performance of an axial turbine at the Gaoliangjian power station. CFD results agreed well with field test data. Using the same numerical method, a new siphon turbine was then designed based on the original distributor and turbine runner equipment. This study investigated the effect of different siphon outlet passage geometry parameters, runner blade shapes, and distributors on the hydraulic performance of the siphon turbine. The maximum hydraulic efficiency increased to 87.9% under a head of 2.87 m. Finally, the hydraulic performance of the turbine was compared for four different distributor designs after adding an intake sump at the turbine entrance. The bell-shaped distributor with four guide vanes resulted in the highest power output at the lowest head. Therefore, the siphon turbine is a good option for energy conversion in ultra-low water head settings.

Experimentally determined efficiency characteristics of two micro turbines are discussed in this paper. One turbine (15 kW) is working with cyclopentane, the other turbine (12 kW) expands hexamethyldisiloxane (MM). The two turbines are designed and built in accordance to the concept of a micro-turbine-generator-construction-kit (MTG-c-kit) for small-scale Organic Rankine Cycle (ORC) waste heat recovery. The motivation for this MTG-c-kit and its architecture will be briefly introduced. Both single stage impulse turbines show a high design point total-to-static isentropic efficiency: the 15 kW cyclopentane turbine achieves 65.0%, the 12 kW hexamethylidisiloxane turbine achieves even 73.4%. Furthermore, the discussed off-design characteristics of the turbines prove that their operating behavior is very advantageous for small waste heat recovery plants - the turbine efficiency keeps a high level over a wide range of pressure ratio and rotational speed.

One of the current major challenges in wind energy is to maximize energy production of wind farms. One approach in this effort is through control of wind turbine wake interactions, since undesirable wake interactions can introduce additional mechanical stresses on turbines, leading to early failures and reduce overall energy production of wind farms. To develop control strategies that can minimize wake interactions, it is essential to simulate wake behaviors accurately and quickly. In this work, a fast and accurate turbine wake model capable of modeling turbine wakes under yaw is presented. This model builds upon the work of existing wake models and is capable of producing results comparable to that of conventional full CFD simulations using a fraction of the computational cost. The accuracy and speed of the proposed model allows for the development of real-time turbine control strategies to maximize power output. The results of the proposed model are validated with previous numerical and experimental data.

In this paper, a new combined cycle of asymmetric twin-scroll turbocharged diesel engine cycle and inverse Brayton cycle (IBC) for use is proposed. The use of a single asymmetric twin-scroll turbocharged diesel engine cycle is simple in structure and can improve the trade-off between low fuel consumption and nitrogen oxide emissions; however, both the engine exhaust gas recirculation (EGR) rate and the exhaust energy utilization should be further improved. A test bench experiment was performed to validate the numerical models of the single-cycle and combined-cycle approaches. Based on the models, the influence laws of the critical system parameters (turbine asymmetry and the IBC turbine throat area) on the engine performance characteristics were studied. The combined cycle was found to achieve improvements in both the engine EGR rate and the power. Given the same EGR rates at different engine speeds, the power improvement of the combined cycle was found to increase with increasing engine speed and decreasing turbine asymmetry, reaching a maximum of 5.00%. Moreover, further power improvements with an increasing IBC turbine throat area were observed, with the maximum power improvement of 5.78%. Compared with the power turbine, the combined cycle can utilize more waste heat at low and medium engine speeds; thus, the combined cycle is well-suited for use in heavy-duty diesel engines. The new combined cycle described in this report has great potential to provide substantial gains in both engine emissions and energy.

This work introduces a numerical analysis of three-bladed Darrieus vertical axis wind turbine performance using 25 different sectional profile airfoils from different families. This investigation is to optimize and maximize torque output coefficient and output power coefficient as well as studying force analysis for the optimum airfoil. Aerodynamic simulations were used depending on finite volume analysis using computational fluid dynamic (CFD) methodology. These CFD simulations used the unsteady (transient) Reynolds-Averaged-Navier-Stokes (URANS) calculations to solve and analysis the flow field around the turbine. Quantitative and qualitative validations were presented in this work, it is found that an acceptable agreement between the current CFD calculations and the published experimental work in the calculations of the power output coefficient. The results presented that the optimal configuration is LS (1)-0413 airfoil. The power coefficient of the turbine consists of LS (1)-0413 airfoil has been increased by 16% compared to NACA 0021 performance. Furthermore, in the current study, the different forces on the different elements of the Darrieus turbine were analyzed during the rotation as well as in stationary conditions for the best blade profile.

Palm oil mill effluent (POME) is a potential source for biohydrogen. A continuous stirred tank reactor was used to study the effects of mixing speeds of a Rushton turbine on the biohydrogen production. The initial organic loading rate and volatile solids of influent were 55 g of chemical oxygen demand per liter of influent per day and 30.28 g of volatile solids per liter of influent, respectively. The retention time was 24 h and the turbine speeds were 10, 50, 100, and 150 rpm. The corresponding hydrogen yields were 2,669, 2,868, 3,413, and 3479 mL per liter of influent. The total maximum hydrogen yield at 150 rpm was equivalent to 6958 mL per liter of POME. A speed of 100 rpm was recommended for the constant speed operation as it gave the highest net energy gain of 23.96 kJ LPOME-1. Five varying speed schemes were studied to determine the maximum net energy gain. The varying speed schedule should be 100 rpm for the first 8 h and 10 rpm for the rest 16 h, which increased the net energy gain by 11% in comparison to the 100 rpm constant mixing speed. Feasibility analysis revealed possibility in industrial application.

Interstage turbine combustors can be used to improve the thrust-to-weight ratio of gas turbines, but their operating conditions and technical requirements are obviously different from those of traditional gas turbine combustors. A typical feature of these combustors is the slight temperature rise combustion under the high velocity conditions of combustor inlets. In this study, a new type of interstage turbine combustor with high performance was proposed, and the influence of the injection mode on the combustion characteristics was investigated. Seven combustion modes with a trapped-vortex combustion zone and preheated fuel nozzles were designed. The effects of the average temperature of the combustion zone (changed by the air injection mode) and the combustion-zone temperature distribution (changed by the combustion-zone configuration) on the combustion characteristics, including the stable combustion boundary, the combustion efficiency, and the temperature distribution, were studied experimentally and numerically. The results showed that high-efficiency combustion in a wide, stable working range was achieved. The new combustor had a shorter length than the conventional combustor and had a wider lean blowout boundary compared to the same type of combustor. Based on the results, the optimal combustor configuration that could be used for practical applications in high-efficiency gas turbines was determined.

In this study the mixing quality of turbine impellers with blade angles of 30°, 45°, and 60° was studied on the anaerobic digestion efficiency using a new model based on mixing time, energy consumption, biogas compounds, and slurry characterizations. Study on the mixing process using a single indicator system based image processing technique showed a mixing for 5 and 10 min and pausing for 5 h. The results showed that (i) the impeller with blade angle of 30° and mixing time of 5 min consumed the least energy whereas produced the most CH4 amounts associated with more TS, T.VS, C, and N degradation, (ii) the impeller with blade angle of 60° produced the least CO amounts associated with more COD and BOD removal, and (iii) the suitable mixing time decreased the CO and H2S production. The results confirmed that the significant effects of the impeller blade angle and mixing time on biogas compounds were because of changing the slurry characterizations during the mixing process. Using the new model for efficiency evaluation, the impeller with blade angle of 30° in mixing time of 5 min had the highest efficiency among the researched cases documented its favorite for better digestion in higher efficiency.

Conventional and advanced exergy analysis of a recompression supercritical CO2 cycle was investigated in this study. The first and second splitting levels of exergy destruction are calculated to determine the real potential of enhancement for the S-CO2 cycle performance. The thermodynamic cycle method of advanced exergy analysis is applied in the present work to reveal the endogenous, exogenous, avoidable, unavoidable, avoidable endogenous, unavoidable endogenous, avoidable exogenous, and unavoidable exogenous exergy destruction for each system component. The overall exergy efficiency for the system are determined as 16.63% and 17.13% under real and unavoidable conditions, respectively. Based on the total avoidable exergy destruction rate, the maximum improvement potential for the system is 106.855 MW (about 50% of the total exergy destruction), and of this avoidable value, 34.59% is endogenous, and 65.41% is exogenous. It is also revealed that, for improving the overall system performance, the priority order of components obtained by the conventional exergy analysis is different from that achieved by the advanced exergy analysis. The former suggests this order as: the reactor, the pre-cooler, the LTR, the HTR and the turbine, while the latter recommends the priority as the HTR, the turbine, and the main compressor. The results also indicate that the reactor has the least potential for improvement despite its highest exergy destruction.

The erosion caused by sand particles significantly influences the safety of radial inflow turbine in Compressed Air Energy Storage (CAES) system which operated in desert area. In present study, effects of tip leakage flow on erosion of a CAES radial inflow turbine are investigated at different tip clearances and total pressure ratios. A CFD model coupling Tabakoff and Grant erosion model is utilized for the analysis. Results illustrate that the trailing edge of stator, the leading edge of rotor blades, the shroud and hub surfaces near inlet of rotor cause more severe erosion at each tip clearance. Therefore, wear-resistant coating should be adopted. The severe erosion can also be found at blade tip of rotor. However, it is gradually suppressed with the increase of tip clearance. With the increase of total pressure ratio, the region with higher erosion rate on the shroud of rotor gradually extends to downstream. However, the erosion rate at leading edge of rotor blades is decreased obviously. In conclusion, the erosion effect can be alleviated remarkably when the tip clearance size is of 2% and total pressure ratio is more than 1.84, while the isentropic efficiency is almost kept the same.

A new type of improved coal-fired recompression SCO2 Brayton cycle with a second split flow to the boiler was introduced. The design parameters of the high and low pressure turbines of the above SCO2 Brayton cycle were determined based on a consideration of the economics of the SCO2 system and the realization of the equipment. The self-compiled mean-line design program for two-stage SCO2 axial turbines was used to design the high and low pressure turbines for the 5 MW SCO2 Brayton cycle, with the important design data of the two turbines being given. RANS equations and the SST Turbulence Model were chosen for numerical simulation of the aerodynamic performance of two turbines in the design point and variable operating conditions that used ANSYS CFX and the real physical property data file of SCO2 from NIST software. Numerical results indicated that the isentropic efficiency of the SCO2 high pressure turbine and low pressure turbine with a good variable operating performance are 82.88% and 82.26% in the design point, respectively. The output power of the high pressure turbine and low pressure turbine are 3,251 kW and 6,156 kW, respectively, in the design point, which can meet the design requirements. The Cps curves, limited streamline spectrums, and the Mach number contours of the root, middle and top flow field of the turbine blades is reasonable.

A novel method for the combined cycle retrofitted with compressor inlet air heating (HEAT) process is proposed in this work for part load performance improvement. The performance of the new cycle is researched with two regulations with HEAT and compared with another two strategies with compressor inlet guide vane (IGV). For the novel method, the compressor inlet air is preheated by part of the exhaust flue gas from the heat recovery steam generator. Moreover, comparation result indicates that the novel strategy with HEAT to maintain design turbine inlet temperature (T3) and then to keep turbine exhaust temperature (T4) at its maximum value (HEAT-T3-T4) is suggested for load arrangement. If being compared with the cycle using IGV control to maintain design T3 then keep extreme T4 (IGV-T3-T4), a maximum combined cycle efficiency increment as 1.7% pt. could be obtained by the cycle with HEAT-T3-T4. Both energy analysis and exergy analysis are given in this paper. The simulation results indicate that higher compressor outlet temperature (T2) decreases the extra exergy destruction during combustion, so that the performance of the cycle with HEAT is improved. Meanwhile the specific work of each cycle has also been presented. Furthermore the pressure loss affection of the compressor inlet air heat exchanger on the combined cycle performance is investigated in range of 0%–5%. Each 1% pressure loss is calculated to decrease 1.4% on the design power output, and 0.25% pt. on the combined cycle efficiency, which will weaken the performance improvement. To summarize, this paper proposes a novel method for the combined cycle power output adjustment to obviously improve its part load efficiency. This innovative solution has never been suggested before and it could be combined with other methods for better result.

Vertical Axis Wind Turbines (VAWTs) are suitable for use in populated areas. The main parameter of the design of this type of the wind turbine is the cross sectional profile of the turbine blade. Additionally, the turbine performance and the generated aerodynamic noise of the VAWTs are critical issues that could limit the spreading of these turbines especially in the residential zones. In the last years, some publications investigated the J-shape Darrieus turbine and praised the performance of this design. Therefore, the present investigation introduces a criticism of the J-shape Darrieus Vertical Axis Wind Turbine (J-SD-VAWT) with three-bladed rotor. An accurate comparison has been introduced for three different turbines with different airfoils sections (NACA 0015, NACA 0021 and S1046). The comparison included the standard airfoil design and the J-shape of the same airfoils from two points of views of turbine performance and noise generation. Aero-acoustics and performance of the proposed design was thoroughly investigated using the Computational Fluid Dynamics (CFD). Both the Unsteady Reynolds-averaged Navier-Stokes (URANS) equations and the impermeable Ffowcs Williams and Hawkings (FW-H) equation were simultaneously solved. The effects of J-shape cut ratio, speed ratio, and turbine solidity were investigated. For all configurations, the results indicated that J-shape reduced the performance and did not reduce the turbine noise.

Hybrid renewable energy systems are proving to be capable and emission-free sources of power generation, especially for off-grid/remote areas. This study develops a mathematical model to optimize a hybrid solar-wind energy system with storage for a remote island with genetic algorithm (GA). Four different cases are evaluated and the results are compared with that, the widely-used HOMER software, illustrating that GA method can output a more optimal system than HOMER in respect of cost and system reliability. Moreover, two systems with different wind turbine size are analyzed and their results present very little difference in terms of system cost and reliability, indicating that wind turbine size has little impact on the results. Furthermore, the simulated performance of the system and the effects of loss of power supply probability (LPSP), variation of load and renewable energy resources on the system cost are analyzed. Sensitivity analysis on some key parameters indicates that by considering a slight (1–5%) LPSP there is a significant decrease in initial capital cost (25–30%), operating cost (15–17%) as well as COE. It is evident from the sensitivity analysis that initially it is better to energize the off-grid/remote areas with small LPSP than no electricity.

It is important to accurately estimate the impact of manufacturing geometric variations on the turbine aerodynamic performance for the engineering design and manufacture. In this paper, a method to quantify the uncertainty impact of the blade geometric variations was proposed. The principal-component analysis combined with the Kolmogorov-Sminov test and the Sobol sensitivity analysis was used for the uncertainty modeling of the blade geometric variations, and the Kriging surrogate model based on the polynomial chaos expansion (PC-Kriging) was used for the uncertainty quantification in the method. Meanwhile, a Reynolds Average Navier-Stokes (RANS) solver was combined to simulate the aerodynamic performance. This method was applied to estimate the impact on the aerodynamic performance of a low-pressure turbine. The calculation results demonstrated that the aerodynamic performance was significantly influenced, which was manifested as an overall deterioration, a large fluctuation and several extreme cases. Detailed analysis of the mechanisms at the origin of the variations in the aerodynamic performance indicated that the variations of total pressure loss mainly come from the variations of the wake mixing loss, and the 70%–100% axial region on the blade is the sensitive region. The geometric variations, especially the variations of the blade thickness, in the sensitive region are one of the main factors leading to the performance variations. In the engineering manufacture, reasonable formulation of the manufacturing tolerance based on the results of the uncertainty analysis can improve the turbine aerodynamic performance under the influence of the geometric variations.

A novel combined organic Rankine cycle and ejector heat pump is proposed, which combines the organic Rankine cycle and ejector heat pump, and could produce both power output and heat output simultaneously. An ejector is installed on the turbine inlet side to increase the total heat exchange amount of the combined cycle by utilizing the injection capability of the high-pressure primary fluid. Using the heat exchange capacity of the cold source to adjust the matching problem between the primary fluid heat source and secondary fluid heat source. The constant pressure mixing model is used to model the ejector, and a new solution method of the model is proposed. Through the parametric analysis, the results show that the heat exchange of secondary fluid and turbine intake pressure have significant effects on the thermal efficiency and heat recovery capacity. By comparing with the basic organic Rankine cycle, the maximum net power output of the novel combined cycle can be increased by 10.78%, and the maximum heat recovery capacity can be increased by 19.04%.