Optimization of Turbine Blade Pitch Angle of a Home-built Wind Turbine for Maximum Power Output

Straight-blade Darrieus vertical axis wind turbines are used as medium and small size wind turbine because of higher power output in vertical axis wind turbine (VAWT). In our previous study, the relationship between the performance and Reynolds number based on airfoil chord length had been investigated by using small-scale test models of lift-type VAWT, and the results showed that the performance of tested wind turbine models with small diameter was clearly lower than that of the large-scale field test machine, and its performance also varies significantly with the blade pitch angle. In this study, we focused on the performance of a small-scale straight-blade Darrieus VAWT, the relationship among the blade airfoil camber direction and the pitch angle, and the performance of the small-scale VAWT was examined experimentally by using a small-scale VAWT test model with Gurney flap which was a small flat plate. Gurney flaps with its height h, as a ratio to the blade chord length c, h/c = 0.036 to 0.055, were attached to the blades of the VAWT test model, in addition, the attaching direction of the Gurney flap on the blade was examined for both inward and outward of the rotor, and the pitch angle was also examined for a range of −5 to 10 degrees. These results are discussed comparing with the result of the VAWT without Gurney flap and considering the numerical results for the single blade with/without the Gurney flap. The results showed that the performance of the tested VAWT was reversed between the inward and outward Gurney flaps around a pitch angle of 10 degrees. That is, the inward Gurney flap was superior at a pitch angle of less than 10 degrees, while the outward Gurney flap was effective at a pitch angle of more than 10 degrees. Furthermore, for the tested small-scale VAWT model, the optimum pitch angle was about 5 degrees, and the inward and shorter Gurney flap showed higher power performance of the VAWT under this pitch angle condition.

The reduction in the power output fluctuation of grid-connected wind turbine-generator systems is strongly required to further increase their total installed capacity in Japan. This study focuses on limiting the maximum electric power output by changing the set point of the power output control as a reduction technique. The influence of limiting the maximum electric power output of a 2 MW-system, which adopts the variable speed operation, on the power output fluctuation characteristic is analyzed through numerical simulation conducted by using an observed field wind data. The focus is on the power output fluctuation, which is important for management of commercial power systems including power plants, of the 2 MW-system with six cases of the maximum electric power output. The results show that limiting the maximum electric power output does not have an influence on the power output fluctuation characteristic and control performance during the pitch angle operation at high wind speeds. However, the year-round simulation reveals that limiting the maximum electric power output brings a tradeoff between the reduction in the power output fluctuation and the generating performance.

Ammonia is an alternative renewable green fuel with significant potential for addressing climate change concerns. Blending ammonia with methane has emerged as a viable strategy to improve the laminar burning velocity of ammonia. In this study, we propose a mechanism for methane/ammonia combustion, comprising 31 species and 131 chemical reaction steps, and investigate the emissions of CO and NO, along with electrical power output and energy efficiency of a micro-thermal photovoltaic (MTPV) system fueled with premixed ammonia/methane/oxygen. Three key parameters are identified as: 1) the inlet mixture flow velocity, 2) the CH4 mole fraction blended ratio (ξCH4), and 3) the material of the micro-combustor. The MTPV system achieves its highest energy efficiency (5.8 %) at an inlet velocity (vin) of 2.3 m/s, and reaches its maximum electrical power output (6.9 W) at vin = 7.2 m/s. Further, increasing ξCH4 can enhance electrical power output (ξCH4 = 0.9 yields 1.37 W more than that at ξCH4 = 0.1). Finally, altering the micro-combustor material is shown to have little effects on electrical power output, NO emissions, and energy efficiency. However, the MTPV system made of quartz is found to reduce CO emissions by 15 % and 12 % in comparison with those systems made of Sic and steel, respectively.

Currently, wind and solar technologies only generate 0.77% and 0.014% of the U.S. electricity consumption, respectively [1]. Though only a small portion of total U.S. electricity production, both sources have seen significant growth recently. For instance, Texas has more than quadrupled its installed wind capacity over the period from 2005–2009 with new installations totaling over 9400 MW [2, 3]. These two resources are globally available and have the potential to generate massive amounts of electricity. As the amount of installed wind turbines continues to grow, gaining better knowledge of their operation and their dynamic response to changing wind conditions is important to ensure their smooth integration and safe operation. The goal of this research is to analyze the dynamic and steady state operations of a 1.5 MW variable speed wind turbine that uses an external rotor resistive control mechanism. The addition of the external generator rotor resistance allows for adjustment of the generator slip and employs a feedback controller that maintains constant power output at all air velocities between the rated wind speed and cut-out wind speed. Using the electronic programming language PSCAD/EMTDC the model simulates the dynamic response to changing wind conditions, as well as the performance under all wind conditions. The first task of the model was to determine which blade pitch angle produces a maximum power output of 1.5 MW. A sweep was used where the simulation runs over the entire range of wind speeds for a selected pitch angle to find which speed resulted in maximum power output. This sweep was used for numerous blade pitch angles until the combination of wind speed and pitch angle at 14.4 m/s and −0.663°, respectively, resulted in a maximum power of 1.5 MW. The second task was to evaluate the model’s dynamic response to changes in wind conditions as well as steady state operation over all wind speeds. The dynamic response to an increase or decrease in wind speed is important to the safety and life expectancy of a wind turbine because unwanted spikes and dips can occur that increase stresses in the wind turbine and possibly lead to failure. In order to minimize these transient effects, multiple controllers were implemented in order to test each ones’ dynamic response to increasing and decreasing changes in wind velocity. These simulations modeled the characteristics of a variable-speed wind turbine with constant power rotor resistive control. First, through calibrating the model the design specifications of blade pitch and wind speed which yield the peak desired output of 1.5 MW were determined. Then, using the method of controlling the external rotor resistance, the simulation was able to maintain the 1.5 MW power output for all wind speeds between the rated and cutout speeds. Also, by using multiple controllers, the dynamic response of the control scheme was improved by reducing the magnitude of the initial response and convergence time that results from changes in wind speed. Finally, by allowing the simulation to converge at each wind speed, the steady state operation, including generator power output and resistive thermal losses, was characterized for all wind speeds.

Development of a solar and gas-fired heat pipe receiver for the Cummins power generation 7.5 kWe dish/Stirling system

Reliability and loading-following studies of a heat pipe cooled, AMTEC conversion space reactor power system

The performance of a 300 kW organic Rankine cycle (ORC) prototype was experimentally investigated for low-grade waste heat recovery in industry. The prototype employed a specially developed single-stage radial turbine that was integrated with a semi-hermetic three-phase asynchronous generator. R245fa was selected as the working fluid and hot water was adopted to imitate the low-grade waste heat source. Under approximately constant cooling source operating conditions, variations of the ORC performance with diverse operating parameters of the heat source (including temperature and volume flow rate) were evaluated. Results revealed that the gross generating efficiency and electric power output could be improved by using a higher heat source temperature and volume flow rate. In the present experimental research, the maximum electric power output of 301 kW was achieved when the heat source temperature was 121 °C. The corresponding turbine isentropic efficiency and gross generating efficiency were up to 88.6% and 9.4%, respectively. Furthermore, the gross generating efficiency accounted for 40% of the ideal Carnot efficiency. The maximum electric power output yielded the optimum gross generating efficiency.

Wind turbines operate predominantly in relatively unsteady flow conditions and are typically misaligned with the incoming wind. Based on the literature review, controlling a section of the trailing edge of the turbine blade is found to reduce load fluctuations on wind turbine blades. Here, a detailed experimental setup describes a 3.5 m diameter wind turbine equipped with a trailing edge flap (TEF). The instrumentation of the compact blade was capable of measuring surface pressure and root bending moment, as well as controlling a TEF simultaneously and in time-resolved fashion. The blade is of constant pitch and chord of 178 mm while the TEF covers 20% of the chord and 22% of the 1.47 m aerodynamic blade span. The turbine was tested in a controlled wind generation facility large enough to house the turbine with less than 7% blockage. The wind turbine was tested for a range of tip speed ratios, blade pitch angles, flap angles and yaw cases. Although the turbine blade is capable of cyclically and dynamically change the blade pitch and flap angle, this paper only investigates constant pitch and flap angles. The results show that changes to the flap or pitch angle are capable of manipulating the coefficient of power, root bending moment and normal force coefficient. The results also show that the flap demonstrates similar control authority to that of the pitch system with the flap occupying just 4% of the blade surface area without reducing the power output of the turbine.

Experimental study on Organic Rankine cycle for low grade thermal energy recovery

Assessment and control of wind turbine by support vector machines

Pitch control by controlling the pitch angle of the wind wheel blade of the wind turbine generator can control the rotation speed when the wind turbine generator is starting and the output power when the wind turbine generator is on grid. The wind wheel can get maximum wind energy when its blade tip speed ratio is an optimum value. When wind speed is less than the rated speed, the rotation speed of the wind turbine generator system should be controlled in order to get the optimum blade tip ratio. When wind speed is larger than the rated speed, the output power must be also controlled by changing the pitch angle of the blade according to the wind speed or the wind turbine will be damaged because of the over load. To get the maximum output power under lower wind speed and to maintain the stable rated output power under higher wind speed, the proper method must be used. In classical control, the controller design needs the accurate mathematical model of the wind turbine generator system, but this model is very difficult to get. To solve this problem, we use fuzzy controller to trace the maximum power when wind speed is lower than the rated speed and use neural network to get the proper pitch angle and so to limit the output power when the wind speed is greater than the rated speed. The simulation block diagram and simulation results were obtained. Compared with the PID controller, intelligent controller has better anti-interference property. The fluctuation of the power is minimized, the maximum power is traced and the rated power is maintained.

Parametric study of the quasi-static response of wind turbines in downburst conditions using a numerical model

In this paper, a research for the effectiveness enhancement of a Cycloidal Wind Turbine by individual active control of blade motion is described. To improve the performance of the power generation system, which consists of several straight blades rotating about axis in parallel direction, the cycloidal blade system and the individual active blade control method are adopted. It has advantages comparing with horizontal axis wind turbine or conventional vertical axis wind turbine because it maintains optimal blade pitch angles according to wind speed, wind direction and rotor rotating speed to produce high electric power at any conditions. It can do self-starting and shows good efficiency at low wind speed and complex wind condition. Optimal blade pitch angle paths are obtained through CFD analysis according to rotor rotating speed and wind speed. The individual rotor blade control system consists of sensors, actuators and microcontroller. To realize the actuating device, servo motors are installed to each rotor blade. Actuating speed and actuating force are calculated to compare with the capacities of servo motor, and some delays of blade pitch angles are corrected experimentally. Performance experiment is carried out by the wind blowing equipment and Labview system, and the rotor rotates from 50 to 100 rpm according to the electric load. From this research, it is concluded that developing new vertical axis wind turbine, Cycloidal Wind Turbine which is adopting individual active blade pitch control method can be a good model for small wind turbine in urban environment.

Design and material variation for an improved power output of AMTEC cells

The dependence on fossil fuel for power generation has a significant negative impact on environmental damage. To reduce the environmental damage, the use of wind energy for power generation needs to be increased and improved. A new type of wind turbine which has been reported recently is a cross axis wind turbine which can be designed for use in high-rise urban buildings where wind condition is more favorable. A model of a cross axis wind turbine which has a rotor diameter of 70 cm and a height of 60 cm has been fabricated and preliminarily tested. The wind turbine model consists of five vertical blades and two horizontal blade arrangements each having five blades. The performance test was carried out at a constant wind speed. During the test, the blade pitch angle was varied from 20 to 60 and wind speed was varied from 5 m/s to 7 m/s. Analysis and evaluation results show that the output power and efficiency of the wind turbine are affected by the blade pitch angle. At wind speed of about 7 m/s, the estimated maximum power is 0.15 W and maximum efficiency of only 0.17% for which the pitch angle was about 60 and tip speed ratio about 0.35.