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Considering the need to reduce greenhouse gas emissions, onshore wind energy is certain to play a major role in future energy systems. This topic has received significant attention from the research community, producing many estimations of Europe's onshore wind potential for capacity and generation. Despite this focus, previous estimates appear to have underpredicted both the amount of available future wind capacity as well as its performance. Foremost in this regard is the common use of contemporary, or at least near-future, turbine designs which are not fitting for a far-future context. In response to this, an improved, transparent, and fully reproducible work flow is presented here, and applied to determine a future-oriented onshore wind energy potential for Europe. Within a scenario of turbine cost and design in 2050, 13.4 TW of capacity is found to be available, allowing for 34.3 PWh of average generation per year. By sorting the explicitly-placed potential installation locations by their expected generation cost, national relationships between cost and performance versus installed capacity are found, and it is also seen that all countries possess some potential for onshore wind energy generation below 4 ct € kWh - 1. Furthermore, it is unlikely for these costs to exceed 6 ct € kWh - 1 in any future capacity scenario. • Determination of onshore wind energy potential in Europe for 2050. • Land eligibility, explicit futuristic turbine placement, and 37 simulation years. • Full potential at 13.4 TW and 34.3 PWh/a, with expected costs at or below 6 ct/kWh. • All European countries possess at least some potential below 4 ct/kWh. • Usage of futuristic turbine designs for future energy system designs is crucial. [ABSTRACT FROM AUTHOR]

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. • Introduction of a Micro-Turbine-Generator-Construction-Kit for ORC plants. • Experimental results for two different representatives of this kit. • Confirmation that the kit is practical for small-scale waste heat recovery. • Proof that micro turbines are competitive as expander for ORC plants <100 kW el. • Abstract. [ABSTRACT FROM AUTHOR]

Abstract A cycle simulation code with integrated turbine design/optimization algorithm has been developed and utilized for the analysis/optimization of ≈ 10 M W e recompression supercritical carbon dioxide Brayton cycle. Integrated turbine design and optimization code computes the turbine design engaging the meanline design calculations as a function of received inlet conditions from the main cycle simulation code. Moreover embedded turbine code optimizes the turbine geometric by minimized the losses with in the turbine using response surface optimization methodology and returns turbine geometry and performance parameters to main code. In order to capture the swift variation in thermophysical properties of SCO 2 in the supercritical region, cycle design point code and embedded turbine codes are linked with NIST REFPROP program. Integrated turbine design/optimization code was validated using 3D Reynolds-Averaged-Navier-Stokes calculations. Response surface methodology was tested by comparing the 3D computation results for the turbine baseline and optimized designs. Finally recompression supercritical carbon dioxide Brayton cycle was analyzed under various conditions of cycle's minimum temperature, minimum pressure, and pressure ratio and split mass fraction. On the basis of the results it is recommended to use proposed model for more realistic and accurate modeling cycle design point analysis. Highlights • Development of cycle simulation tool with embedded turbine design/optimization code. • A meanline turbine design methodology is developed using real gas model. • The turbine rotor is optimized using Response Surface Method (RSM). • Conduct cycle analysis and optimization of recompression S C O 2 − B C. [ABSTRACT FROM AUTHOR]

The article presents a new technical solution for designingmicroturbine nozzles. The nozzles have a rectangular cross section, the longitudinal axis of the accelerating section is straight, and its projection onto the plane of the nozzle is placed at a tangent to thecircle formed by the middle diameter of the turbine. This makes it possible to increase the efficiency of the microturbines, which have nozzles with outlet angles from 5° to 9°.Microturbine efficiency research was carried on an experimental turbine. The studied turbine power reached 80 kW. The authors submit an empirical model makes it possible to predict the efficiency of a microturbine and determine the values of the factors corresponding to the maximum efficiency mode. Through optimization, the efficiency of the investigated microturbine stages reached 0.62 with tapered nozzles. The other parameters were: the nozzle outlet angle - 5°; the rotor blade input angle - 8.1°; the dimensionless peripheral speed - 0.44; the degree of pressure reduction per stage - 19.7. [ABSTRACT FROM AUTHOR]

With the widespread application of pulse turbochargers in internal combustion engines, steady or quasi-steady turbine models are no longer qualified for on-engine turbine performance prediction. Pulsatile flow condition caused by the reciprocating nature of the engine results in strong unsteadiness across the turbocharger turbine, which makes the turbine performance departing from that under steady or quasi-steady conditions. Modelling turbocharger turbine through a one-dimensional (1D) method is an important approach to simulate the unsteady performance of the turbine. In this paper, a 1D performance model of turbocharger turbines is presented. The model solves the turbine volute flow with 1D viscous equations, with volute curvature and circumferentially continuously flow exiting at volute outlet considered. The circumferential flow non-uniformity at volute outlet is preserved. The turbine rotor is modeled with multiple meanline models. The model was used to simulate the performance of a mixed-flow turbine and validated by the experimental data. Results show that the performance predictions are in good agreement with the experimental data. Flow parameters at internal points of the turbine predicted by the 1D model were compared with three-dimensional unsteady simulation results and reasonable agreement was observed, which demonstrates the ability of the 1D model in capturing the pulse propagation. [ABSTRACT FROM AUTHOR]

Delaying a stall improves the performance of any turbomachinery system. TC (tip clearance), which is used in a bi-directional flow Wells turbine of an ocean wave energy device, changes the flow pattern on the turbine blade suction surface, while changing or modifying the TC zone can help obtaining a delayed stall. In the present work, a new tip grooving scheme is introduced and the performance is compared for different tip groove depths and TCs of a Wells turbine. The performance is defined in terms of wider operating range or stall delay, power production and efficiency. The problem was solved by a numerical analysis technique. A multi-block meshing scheme was employed to generate structured and hexahedral elements in the computational domain and the flow was solved in ANSYS CFX ® v14.5 by solving Reynolds-averaged Navier Stokes equations. It was found that the grooves improve the turbine operating range and power production as compared to those of the turbine without a groove. The groove depth of 3% of the chord length produced highest power and widest operating range. Using the circumferential groove, 26% increase in turbine power output for a particular operating point is achieved. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents an alternative design of wind turbine. Wind turbine design includes subsystem elements necessary to satisfy rigorous grid codes imposed by transmission system operators (TSOs). While the addition of these components assures compliance they have an impact on the overall reliability. A new approach which can be taken by the industry is to rethink the design of the turbines, in this paper we describe how wind turbine units could be simplified in order to bring manufacturing and maintenance costs down and increase reliability for a farm installation of multiple machines. Installations with single stand alone turbines have to meet the stringent regulations to satisfy grid codes requirement, however, in a “farm” like configuration, a different approach can be taken to make the farm compliant rather than each individual turbine. A description of a Simulink model for this farm configuration is given and data extracted from the simulation are analysed. [Copyright &y& Elsevier]

Abstract: This paper describes thermal analysis methodology results for the supercritical steam turbines. The analysis presented here concerns the external cooling of the turbine components. Due to the supercritical parameters of the live steam, the inlet areas of the high and intermediate pressure parts are exposed to the steam at high temperature level. The design solutions applied to the turbines so far aim to protect the inlet areas. Basic solution incorporate protective screens, which are made of a material more resistant to the high temperature than the rest of the components. Additional protection is provided by the external cooling. The applications of both methods described above allow to increase the live steam temperature. The conducted analysis determined the temperature field in the steam, which cools the rotor, as well as the distribution of the temperature and stresses in the rotor. The obtained results were then applied to the investigations concerning the durability of the rotor. [Copyright &y& Elsevier]

Mixed flow turbines have been widely applied in turbochargers, aircraft engines and power generation systems. It is well known that the mixed flow turbine is a seat of several losses such as secondary flow generation and incidence effects. The turbine loss is dependent on its design parameters, especially the blade number. Commonly, this last parameter is determined by old empirical correlations which are less accurate than more advanced computation methods. In the light of this, the present paper investigates the effect of the blade number using the latest advanced 3D-CFD code attempting to improve performance and further reduce loss generation. Seven designs of the mixed turbine with different numbers of blades from 3 up to 15 have been considered for investigation. Computed results have been validated against experimental data collected from a developed test rig. Two correlations have been developed relating the mass flow parameter and the output torque of the turbine to its blade number. Also, a detailed analysis on the effect of the blade number on the tip clearance flow leakage has been performed. Results showed better efficiency and a decreased blade passage loss with an increasing blade number. • Blade number effect on performance of one mixed flow turbine was investigated. • Seven designs with different blade numbers have been considered for investigation. • A good agreement has been recorded between numerical and experimental results. • Passage and incidence losses decrease with an increasing blade number. • Swallowing capacity and efficiency are improved with an increasing blade number. [ABSTRACT FROM AUTHOR]

Gravitational water vortex turbine (GWVT) is one of the emerging micro-hydro power plants because it requires less expertise, low head and reduced setup space for installation. A detailed performance evaluation of the GWVT based on turbine performance curves is yet to be explored. With the help of mathematical expressions along with the experimentation, the present study presents different performance parameters (PPs) such as; rotational speed, torque, brake power and mechanical efficiency of single-stage GWVT under various flow and design conditions. The effect of vortex height, runner position, percentage submergence of blades, notch angle, blades aspect ratio, blades curvature, blades inclination, hub diameter, straight and conical edged blades on the PPs has been investigated. The analytical and experimental results are in a good agreement both qualitatively and quantitatively. The experimental results show that the vortex height and a good vortex shape with fully developed air core are the major parameters in deciding the performance of GWVT. Better performance of GWVT can be achieved at middle of the rotational speed range i.e. between the minimum and maximum load conditions with minimum possible notch angle and hub diameter, using inclined blades of zero curvature fixed near the bottom of the basin. • Turbine design and operating conditions affect the turbine performance. • Rotational speed is a strong function of blade submergence in water vortex. • Vortex height with fully developed air core mainly drives the turbine performance. • Best performance lies at mid-range rpm with minimum notch angle and hub diameter. • Inclined blades of zero curvature fixed near bottom of basin are the best performer. [ABSTRACT FROM AUTHOR]

This work deals with the prediction of the maximum efficiency achievable by turbines for Organic Rankine Cycle (ORC) systems by means of similarity principles. At present, this is a key topic in the preliminary design optimization procedures of these systems. The dimensional analysis applied to the most general ORC turbines scenario helps obtain the functional relationship between maximum turbine efficiency and the most relevant design variables within the general framework of the flow similarity. Aim of the work is to search for the less wide and more convenient set of independent similarity parameters to increase the accuracy of turbine efficiency data in the optimization of ORC systems. Results show that the strict flow similarity does not hold if the same design is used for different working fluids, because real gas compressibility effects cannot be disregarded for most of the fluids usually adopted in ORC systems. On the other hand, a "quasi-similarity" approach can be applied to the design of low volume expansion ratios ORC turbines using the size parameter (SP), volume expansion ratio (VR) and the compressibility factor (Z) as predictors of turbine efficiency. Accordingly, two original correlations for the SP-VR-Z map of optimized axial turbine stages are suggested. • Theory of turbomachines' flow similarity is extended to real gas and scale effects. • General formulation is rearranged to map efficiency of ORC turbines at design point. • Flow similarity in optimized designs is preserved for equal SP-VR-Z-Γ. • Modeled SP-VR-ideal gas map of turbines efficiency is compared to real SP-VR-air map. • SP-VR-Z is proposed as best set of turbine's similarity parameters to optimize ORCs. [ABSTRACT FROM AUTHOR]

This study proposes a method to minimize the cost of energy (COE) of wind turbines on high-altitude sites, in which the parameters of rotor radius, hub height and rated power are optimally designed. Firstly, the COE model is built up, and the wind turbine optimization problem is formulated. Then, Yin-Yang pair optimization is presented and improved to solve the optimization problem. Lastly, the proposed method is validated under typical wind resource distribution and different altitude scenarios. The results show that with the increase of altitude, the optimal COE increases, whereas the three optimized parameters present different trends of variation. It is indicated that by considering the influence of altitude, COE at a certain altitude can be reduced effectively. Meanwhile, the improved Yin-Yang pair optimization shows smaller iteration number of convergence and convergence time in comparison with particle swarm optimization and traditional Yin-Yang pair optimization. On this basis, sensitivity analysis of optimized parameters and optimal COE to wind resource parameters is carried out, and the influence of uncertainty of wind resource statistics on optimization results is explored. By doing that, it is shown that the rotor radius, hub height and COE are most sensitive to the change of mean wind speed, and rated power is sensitive to all three wind resource parameters. On the other hand, COE decreases with the increase of three wind resource parameters. These results can be used as a guide for the wind turbine design on the high-altitude site. • A techno-economic model considering altitude influence. • A novel Yin-Yang pair optimization algorithm. • Fast convergence by the improved Yin-Yang pair optimization. • Main reason for increased COE with altitude rise. • Sensitivity analysis of optimized parameters and COE to wind resource parameters. [ABSTRACT FROM AUTHOR]

Savonius wind turbines are the most suitable devices used in urban areas to produce electrical power. This is due to their simplicity, ease of maintenance, and acceptable power output with a low speed and highly variable wind profile. However, their efficiency is low, and the development of optimization tools is necessary to increase the total power output. This work presents a metamodel-based method to optimize the size and shape of a set of deflector plates to reduce the reverse moment of the turbine, using a genetic algorithm combined with an artificial neural network, reducing the computational cost. A parametrization of the deflectors geometry is proposed, and a Computational Fluid Dynamics model was implemented to train and validate the artificial neural network. The method was applied to design the deflectors of an actual 8-blade, 1[kW], 2.5[m] height turbine. Results showed an efficiency increment of 30%, from 0.215, to 0.279 in the turbine with the optimized deflectors. Furthermore, it is capable of producing power at 4[m/s], while the reference design had null power at that point. This methodology demanded 159 h, a substantial reduction of the computational cost of up to 97% in contrast to the classical simulation-based optimization approach. [ABSTRACT FROM AUTHOR]