This paper describes the starting behavior of small horizontal axis wind turbines at high angles of attack and low Reynolds number. The unfavorable relative wind direction during the starting time leads to low starting torque and more idling time. Wind turbine models of sizes less than 5 meters were simulated at wind speed range of 2 m/s to 5 m/s. Wind turbines were modeled in Pro/E and based on the optimized designs given by MATLAB codes. Wind turbine models were simulated in ADAMS for improving the starting behavior. The models with high starting torques and less idling times were selected. The starting behavior was successfully improved and the optimized wind turbine models were able to produce more starting torque even at wind speeds less than 5 m/s.
From ancient times the kinetic energy of the wind is used for various household activities like milling of wheat and corns. In the 1980s blade element momentum theory was presented. Based on blade element momentum theory various wind turbine designs were proposed for various wind conditions. In areas of high wind speeds large wind turbines can be installed. For areas of low and medium wind speeds small wind turbines are installed. It is not possible to start wind turbine at low wind speeds, so changes should be made in the existing wind turbine models in order to increase their sensitivity [
In this research work wind speed and direction data were taken from PMD (Pakistan Meteorological Department) for various sites of KP (Khyber Pakhtunkhwa). Optimized designs were then proposed for these locations. Optimized designs were made using MATLAB coding, ADAMS simulation, and PRO/E modeling.
The optimized designs were then installed at the selected location of KP (one model for each location made of wood) and the output parameters (torque and rpm) were measured which shows a huge improvement as compared to conventional wind turbine models installed in similar wind speed locations.
The main aim of this project was to propose optimized designs for the selected locations of KP. According to the wind speeds and work of Wood [
Size of wind turbines at selected locations of KP.
Location | Average wind speed (m/s) | Size of turbine (meters) |
---|---|---|
Cherat | 4.20 | 5 |
Peshawar | 1.23 | 1 |
Warsak | 2.40 | 2 |
Ramatkoore | 1.70 | 1.5 |
Lorramiana | 3.73 | 2.5 |
Nizampur | 1.74 | 1.5 |
MATLAB coding was done based on the blade element momentum theory. A MATLAB function with the name parameter was used to obtain the blade parameters (chord and twist distribution). The block diagram for this MATLAB function is given in Figure
Block diagram for the determination of blade parameters.
As shown in Figure
Wind turbine models were made in Pro/E environment based on the parameters obtained from MATLAB function. A wind turbine model made in Pro/E is shown in Figure
Initial Pro/e model.
A second MATLAB function calculates the aerodynamic forces on various stations of wind turbine blades. The block diagram for this function is shown in Figure
Logic diagram for the determination of aerodynamic forces.
The MATLAB function as shown in Figure
The Pro/E models were imported into ADAMS environment and the aerodynamic forces were applied on their blades. A wind turbine model with forces applied in ADAMS environment is shown in Figure
ADAMS model with wind forces applied on its blades.
Various models were simulated in ADAMS environment and the models with more starting torque were selected. The complete simulation process is explained in Figure
Flow chart for modeling and simulation of wind turbine blades.
The wind turbine model used for simulation has the following blade parameters. The distance between the leading and trailing ends of wind turbine blade is known as chord length (
Blade parameters for the wind turbine model.
Serial number | Blade station | Local radius meters | Local radius mm | Local radius inches | Chord width meters | chord width inches | Blade angle beta degrees |
---|---|---|---|---|---|---|---|
1 | 1 | 0.15 | 150 | 5.905512 | 0.1679 | 6.610236 | 14.5 |
2 | 2 | 0.2 | 200 | 7.874016 | 0.1608 | 6.330709 | 13.6 |
3 | 3 | 0.25 | 250 | 9.84252 | 0.1537 | 6.051181 | 12.7 |
4 | 4 | 0.3 | 300 | 11.81102 | 0.1466 | 5.771654 | 11.8 |
5 | 5 | 0.35 | 350 | 13.77953 | 0.1395 | 5.492126 | 10.9 |
6 | 6 | 0.4 | 400 | 15.74803 | 0.1324 | 5.212598 | 9.9 |
7 | 7 | 0.45 | 450 | 17.71654 | 0.1253 | 4.933071 | 9.1 |
8 | 8 | 0.5 | 500 | 19.68504 | 0.1182 | 4.653543 | 8.2 |
9 | 9 | 0.55 | 550 | 21.65354 | 0.1111 | 4.374016 | 7.3 |
10 | 10 | 0.6 | 600 | 23.62205 | 0.104 | 4.094488 | 6.3 |
11 | 11 | 0.65 | 650 | 25.59055 | 0.0969 | 3.814961 | 5.4 |
12 | 12 | 0.7 | 700 | 27.55906 | 0.0898 | 3.535433 | 4.5 |
13 | 13 | 0.75 | 750 | 29.52756 | 0.0827 | 3.255906 | 3.6 |
14 | 14 | 0.8 | 800 | 31.49606 | 0.0756 | 2.976378 | 2.7 |
15 | 15 | 0.85 | 850 | 33.46457 | 0.0685 | 2.69685 | 1.8 |
The torque output from the simulation was compared with the experimental results. The experiments were carried out in open environment with cross flow of wind on wind turbine rotor. The cross flow of wind caused a slight difference between the experimental and simulation results. The agreement between the output of simulation and experimental results shows us that we can analyze various wind turbine models using this simulation setup. The comparison is shown in Figure
Comparison between experimental and simulation results.
In order to validate the simulation results from ADAMS software, the output torque is compared with the experimental results for the same wind conditions. For a wind turbine blade design modeled by [
After simulation settings and forces application the initial Pro/e models for the selected locations were simulated. First of all the initial wind turbine designs were imported into ADAMS. After simulating, those initial models graphs from ADAMS postprocessor for each selected location were obtained. The output power of wind turbine depends on both the output rpm of wind turbine and the out torque of wind turbine. In order to study the starting behavior of wind turbines, at least one of these two parameters must be monitored. The torque at the output is monitored in this research work. The focus is to bring changes in wind turbine blade profile so that the output torque increases during the starting time. Various wind turbine models were simulated in ADAMS environment and the output torque was recorded. The output torque for the initial models is shown in Figures
Output torque for the initial design of Peshawar region.
Output torque for the initial design of Cherat region.
The wind turbine blade parameters were altered near the hub region and the new wind turbine models were then simulated in ADAMS environment. The output graphs for torque are shown in Figures
Output torque for the increasing chord design of Cherat region.
Output torque for the decreasing chord design of Cherat region.
Output torque for the increasing blade angle design of Cherat region.
Output torque for the decreasing blade angle design of Cherat region.
Figures
The optimized wind turbine models for the selected locations of KP are shown in Table
Optimized wind turbine designs for the selected locations of KP.
Ramatkore | Chord distribution | 0.314 | 0.288 | 0.253 | 0.232 | 0.186 | 0.164 | 0.153 | 0.121 | 0.110 | 0.101 | 0.08 | 0.076 | 0.06 | 0.047 | 0.03 | ||||||||||||
Twist distribution | 0.406 | 0.383 | 0.362 | 0.328 | 0.231 | 0.210 | 0.188 | 0.156 | 0.123 | 0.101 | 0.06 | 0.041 | 0.03 | 0.027 | 0.02 | |||||||||||||
|
||||||||||||||||||||||||||||
Lorramiana | Chord distribution | 0.432 | 0.391 | 0.353 | 0.330 | 0.276 | 0.251 | 0.243 | 0.217 | 0.191 | 0.183 | 0.16 | 0.153 | 0.13 | 0.101 | 0.09 | ||||||||||||
Twist distribution | 0.464 | 0.443 | 0.418 | 0.376 | 0.271 | 0.230 | 0.211 | 0.189 | 0.145 | 0.107 | 0.06 | 0.031 | 0.020 | 0.018 | 0.01 | |||||||||||||
|
||||||||||||||||||||||||||||
Nizampur | Chord distribution | 0.314 | 0.288 | 0.253 | 0.232 | 0.186 | 0.164 | 0.133 | 0.121 | 0.110 | 0.101 | 0.08 | 0.076 | 0.06 | 0.047 | 0.03 | ||||||||||||
Twist distribution | 0.406 | 0.383 | 0.362 | 0.328 | 0.231 | 0.210 | 0.188 | 0.156 | 0.123 | 0.101 | 0.06 | 0.041 | 0.03 | 0.027 | 0.02 | |||||||||||||
|
||||||||||||||||||||||||||||
Peshawar | Chord distribution | 0.199 | 0.181 | 0.160 | 0.146 | 0.110 | 0.102 | 0.099 | 0.087 | 0.079 | 0.066 | 0.05 | 0.040 | 0.02 | 0.017 | 0.01 | ||||||||||||
Twist distribution | 0.392 | 0.372 | 0.352 | 0.322 | 0.220 | 0.191 | 0.163 | 0.121 | 0.108 | 0.081 | 0.03 | 0.021 | 0.02 | 0.017 | 0.01 | |||||||||||||
|
||||||||||||||||||||||||||||
Cherat | Chord distribution | 0.980 | 0.909 | 0.846 | 0.792 | 0.744 | 0.701 | 0.663 | 0.629 | 0.597 | 0.458 | 0.418 | 0.400 | 0.383 | 0.368 | 0.354 | 0.341 | 0.329 | 0.318 | 0.307 | 0.297 | 0.288 | 0.279 | 0.271 | 0.265 | 0.256 | 0.249 | 0.242 |
Twist distribution | 0.411 | 0.344 | 0.292 | 0.250 | 0.217 | 0.189 | 0.165 | 0.145 | 0.128 | 0.096 | 0.083 | 0.071 | 0.061 | 0.052 | 0.043 | 0.036 | 0.029 | 0.023 | 0.017 | 0.012 | 0.007 | 0.002 | −0.001 | −0.005 | −0.008 | −0.012 | −0.015 |
Wind turbine designs were proposed for low and medium wind speed locations of Pakistan based on the comparison between simulation and experimental results. Simulations were carried out by interfacing ADAMS and MATLAB software. For each low wind speed location the main aim was to improve the starting behavior of wind turbine models. Wind turbine models were modeled in Pro/E and were then simulated using ADAMS and MATLAB.
Various wind turbine models were modeled in Pro/E by varying chord length and blade angles. The simulation results show that increasing the chord lengths and blade angles near the hub region increases the output torque, angular velocity, and angular acceleration.
Increasing the chord lengths and blade angles near the hub decreases the idling time, so the wind turbine reaches its rated speed in minimum time.
Optimized wind turbine models were achieved based on simulation and experimental results. Actual wood models were made based on the chord and blade twist data of optimized designs. These wood models were tested and the output power was more as compared to previous wind turbine models designs for the same wind speeds. The next step of the research is to practically install wind turbine models in the proposed locations.
Pitch control, if introduced in these wind turbine models, will help in staring and also help to minimize the rotational speed of wind turbine models during high speed wind.
The authors declare that there is no conflict of interests regarding the publication of this paper.