Eng. ARONICA Ruben [309041]

Eng. ARONICA Ruben

DISSERTATION

MASTER STUDIES

Scientific coordinator:

Lect. Dr.Eng. Marius Daniel CALIN

BRASOV

2018

TRANSILVANIA UNIVERSITY OF BRAȘOV

FACULTY OF ELECTRICAL ENGINEERING AND COMPUTER SCIENCE

DEPARTMENT OF ELECTRICAL ENGINEERING AND APPLIED PHYSICS

MASTER STUDY PROGRAM: ADVANCED ELECTRICAL SYSTEMS

Eng. [anonimizat].

[anonimizat] a wind turbine.

Scientific coordinator:

Lect. Dr.Eng. Marius Daniel CALIN

BRASOV

2018

Table of Contents

Abstract 2

Introduction 2

CHAPTER 1 3

1.1. Background on the wind’s equations 3

1.2. Aspects regarding the wind turbine’s geometry 5

1.3. Control and regulation of wind turbines 6

1.3.1. The stall regulation 7

1.3.2. Pitch regulation. 7

1.3.3. Yaw regulation 8

1.4. Turbine types and terminology 9

1.5. Wind energy extraction 11

CHAPTER 2 12

2.1 Considerations on the Romanian energy sector 13

2.2 Wind potential energy analysis in the Central region of Romania 14

2.2.1 The average annual wind velocity in Romania 14

2.2.2 Central region’s geographical, physical characteristics and climate analysis 15

CHAPTER 3 27

3.1 Emulation of a wind turbine 27

3.2 Single-phased motor mathematical model 31

3.3 Experimental data and results interpretation 33

3.3 Barriers to develop investment projects in renewable energy 37

CONCLUSION 39

References 40

ANNEXES 42

[anonimizat]. Therefore, the paper includes in the first chapter the most important mathematical equations regarding the wind’s force, a theoretic presentation about the wind turbine (WT) [anonimizat] a wind turbine and the electric wind energy extraction mathematical model. [anonimizat] a simulation of a wind turbine to prove out the necessity of the WT implementation confirming the feasibility of this project.

Introduction

The wind’s force is a [anonimizat] a weather hurricane. Historically, [anonimizat].

[anonimizat] a [anonimizat]. Electricity produced from the wind produces no CO2 emissions and therefore does not contribute to the greenhouse effect. Wind energy is relatively labor intensive and thus creates many jobs. The wind turbines main drawback is the noise when they produce electricity. [MAR – 2008]

[anonimizat] a comprehensive study related to this subject.

Fig.1.1 Highlighting of aerodynamics concept [VI]

[anonimizat], respectively the air’s interactions with solid materials. Aerodynamics is a science and study of physical laws of the behavior of objects in airflow and the forces that are produced by airflows.

[anonimizat]’s [anonimizat] or electrical energy. In ideal conditions, these transformations happen without any loss, but the real situation confirms that losses exist, thus defining the efficiency.

CHAPTER 1

Background on the wind’s equations

The mathematical apparatus given below determines the wind energy potential, respectively the potential power developed under ideal conditions.

Considering w the wind’s speed and p the dynamic pressure gives the following equation:

1.1

, where ρ is the air density in kg/m3. The density of the air depends on the atmospheric pressure and on the air’s humidity. If the wind hits an S surface, such as the boats sail, the potential (p) pressure will become mechanical energy used to pull the boat further. If S is the surface area, the following relation gives the F wind force:

1.2

Considering the displacement on the x-axis, the following relation computes the L mechanical work developed by the wind’s force:

1.3

The P power developed by the wind in a τ time interval can be determined:

1.4

, because

1.5

Fig.1.2 Wind’s energy kinetic force calculus schematic, where V means volume, m – air mass, ρ – air density, w – wind speed and S – surface on x length.

To compute the winds kinetic force, considering an arbitrary V air volume, closed by an arbitrary S surface on x length, which is in the wind’s direction, and the surface is normal of the wind’s direction, the air’s volume is:

1.6

Considering air’s density as ρ, the m wind’s air mass will be determined:

1.7

The m air’s mass Ec kinetic force in this case computes by the following formula:

1.8

, where w denotes the wind speed.

Moreover, the following relation gives the kinetic P power developed by the wind in τ time:

1.9

, where

1.10

All these cases are in ideal consideration, without losses. In real case, the technical performances of the equipment determines the η efficiency.

1.11

, where the r indices denotes the factual parameters compared to the theoretically ideal ones.

Aspects regarding the wind turbine’s geometry

The wind turbine main parts are the rotor, the nacelle and the tower (Fig.1.3b). The nacelle is not a fix compartment of the tower and hub, this implies, that there are bearings between the two that allow them to move with respect to each other; that is, the assembly of hub and blades rotate with respect to the nacelle, and the nacelle rotates about the tower axis.

The nacelle (Fig.1.4) serves the following purposes:

Houses the gearbox, generator, coolers for the gearbox oil, and heaters for wintertime, turbine brake system, motors and gear for yaw system, the wind direction and speed measurement systems, the transformer for turbine energy supply, and other equipment based on the turbine design.

Allows yawing of the turbine; that is, adjusting the turbine orientation to the wind direction.

Provides counterweight for the hub and blades’ weight. [AHM – 2012]

Geometrically spoken the wind turbine’s blade has an elongated rectangle form. The radius is the distance between the hub and the blade’s peak, shown in Figure 1.3. If the transversal section is considered, the form of the blades is asymmetrical. This structure helps the wind to hit the bolded part of the blade (Fig1.5); this is the so-called front of the blades. These profiles are the aerodynamic profiles (Fig.1.3a).

Fig.1.3 The rotor and blades of a wind turbine [I]

Fig.1.4 Wind turbine’s blade design [ABB-1959] [GLA – 1935]

Wind turbine blades are long and slender structures where the spanwise velocity component is much lower than the streamwise component. [XII]

Fig.1.5. Nacelle’s main components. Source: US Dept. of Energy – Office of Energy Efficiency and Renewable Energy

Control and regulation of wind turbines

The control system ensures that the turbine operates within the design range; it keeps the rotational speed within a certain range; yaws the turbine; keeps the power output within a certain range and starts or stops the turbine. The control system can ensure a smooth power output P(t) and may optimize the power output at lower wind speeds. To limit the power at high wind speeds the following three strategies are used:

Stall regulation;

Pitch regulation; and

Yaw control.

The stall regulation is the simplest of all because fixes the blades to the hub. Pitching the blades in this case is not possible. A stall regulated wind turbine operates almost at constant rotational speed, and thus, the angle of attack increases as the wind speed increases. On a stall-regulated wind turbine, an asynchronous generator is often used. The rotational speed of the generator in an asynchronous generator’s case is:

1.12

, where fgrid is the grid’s frequency and p denotes the number of pole pairs. Because the rotational speed of the generator is higher than the rotational speed of the rotor, a gearbox used between the generator and the rotor is necessary. The torque characteristic of the asynchronous generator is given.

Fig.1.6 A typical torque characteristic for an asynchronous generator

The pitch regulation makes possible to pitch the entire blade and thus to change simultaneously the angles of attack along its entire length. The result-sketch of one way for pitch control is in Figure 1.7. In this figure is a characteristic that includes the speed of the wind measured for 10 minutes, the generator’s speed which equals to 1500 rpm and the power of the generator, approximatively 1100 kW. Observe that the debited power remains almost constant compared the wind’s speed.

Fig.1.7 Stall regulated wind turbine starting at high wind speed:

Elkraft 1MW demonstration wind turbine.

A pitched blade can act as an aerodynamic brake and it is no longer necessary to include tip brakes as on a stall-regulated machine. By pitching the entire blade, it is possible to control the angles of attack and thus the power output. Power reducing means decreasing the angles of attack and by pitching the leading edge of the blades up against the wind.

At yaw regulation, instead of limiting the power output using pitch regulation, the control is at the turbines yaw. On normal pitch regulated machines, it is common to have a yaw drive, which is trying to rotate the nacelle to minimize the yaw misalignment in order to get as much air through the rotor disc as possible. In high winds, the rotor turns out of the wind to limit the airflow through the rotor and thus the power extraction. For example, the old Western mills used yaw control. Figure 1.8 indicates the difference between stall regulated or pitch, respectively yaw regulated WT.

Fig.1.8 Constant speed versus variable speed

A wind turbine is equipped with an asynchronous generator forcing the blades to rotate at a given speed. [ABB – 1959] [GLA – 1935] [DAN – 2012] [MIH – 2012]

Fig.1.9. WT Pitch Control and Yaw Control [LIE – 2012]

Turbine types and terminology

The names of different types of wind turbine depend on their constructional geometry, and the aerodynamics of the wind passing around the blades; also called airfoils. Fig.1.10 shows a blade section of a horizontal axis wind turbine’s blade [MAR – 2008]. Velocities and forces at a section of a rotating turbine blade. (a) Front view of horizontal axis turbine blade, rotating section speed v; (b) Perspective view, showing undisturbed wind speed u; (c) Section view from the blade tip, showing v in the plane of rotation and distant wind speed u.

Fig.1.10. Wind turbine’s blades

Figure 1.11 gives the classification of possible wind devices.

Fig.1.10 Classification of wind machines and devices. (a) Horizontal axis. (b) Vertical axis. (c) Concentrators.

Wind energy extraction

Wind energy becomes useful only by harnessing and converting into mechanical, respectively electrical energy form. The mathematical equations for these operations are given.

In the undisturbed state a column of wind is upstream of the turbine, having an A1 cross sectional area of the turbine disc, has the following kinetic energy that passes per unit of time:

1.13

, where ρ is the air density and u0 the undisturbed wind speed. This is the power in the wind at speed u0.

Fig.1.11 Power in wind.

In Fig.4.3, the mass of column is ρAu0, and the kinetic energy equals with the given equation:

1.14

The air density (ρ) depends weakly on height and meteorological condition, because wind speed generally increases with height, affected by local topography, and varies greatly with time.

Theoretically, the air’s velocity is constant. This means that the same air passes through the turbine in laminar flow as shown in Fig.1.12.

Fig.1.12 Betz model of expanding airstream

Treat the rotor as an ‘actuator disc’, in this case, across which there is a change of pressure as energy is extracted and a consequent decrease in the linear momentum of the wind. Perturbations to the smooth laminar flow is not a considering problem here, although they undoubtedly occur because of angular momentum is extracted and vortices in the airflow occur.

Area A1 is the rotor swept area, and A0 and A0 areas enclose the stream of constant air mass passing through A1. For energy extraction mathematic modelling, must follow the steps given:

To determine u1. The F force or thrust on the turbine is the reduction in momentum per unit time from the air mass flow rate .

1.15

This force applies by an assumed uniform airflow of speed u1. The 4.3 relation gives the power extracted by the turbine:

1.16

The loss in energy per unit time by that airstream is the power extracted from the wind calculates by:

1.17

Equating PT and Pw the following expression found out is:

4.5

, hence

1.18

Thus, according to this linear momentum theory, the air speed through the activator disc cannot be less than half the unperturbed wind speed. [12. JOH – 2006] [13. MAR – 2008]

CHAPTER 2

The technical potential of onshore wind energy estimates to be 20,000 x 109-50,000 x 109 kWh per year, while the total annual world electricity consumption of about 15 x 109. The global wind power industry installed 539,581 MW in the year 2017, with a difference of 51,927 MW compared to 2016. The countries with the highest total installed wind power are China (145,104 MW), European Union (141,579), United States (74,472 MW), Germany (44,947 MW), India (27,151 MW).

Considerations on the Romanian energy sector

To reduce emissions of greenhouse gases by 21% and to use 10% biofuels in the composition of fuels by 2020, Romania is trying to increase usage of renewable energy from 17.8% in 2005 to 24% in 2020. [24. CON – 2009] [24. YOG – 2016] [2. BRA – 2012] [11. JEF – 2012]

In the present, in Romania the energy is produced primarily based on coal-plants, natural gas and oil, plus energy from hydropower and since 1996, nuclear power. There are three major consumers: industry, households and transport. All this sector is regulated by the National Regulatory Agency in the Energy Field – ANRE (abbreviation in Romanian), which “has the mission to create and enforce regulations necessary for the energy sector, heat and natural gases market functioning.”[II]

Because the use of these sources is restricted, therefore the potential is lower than that presented in Table 1. That is because technological barriers, implications of economic efficiency and the environment. All values are in thousands toe, this measure unit meaning thousands of tones oil equivalent (toe).

Table 1. Annual potential of energy from renewable sources in 2016. Source: PNAER [PNA 210] (National Plan for Taking Action on Electrical Domain in RES)

Production and consumption of energy from renewable sources in 2002-2016 in Romania, are given below

Table 2. Production and consumption from RES energy in Romania (2002-2016)

Observe that in certain years, gross internal consumption exceeds renewable energy production [COR – 2011] [PNAER 2010].

Wind potential energy analysis in the Central region of Romania

Wind potential analysis is a fundamental issue to study, especially in the given case. The following subchapter treats the wind potential in Romania.

The available wind energy on a global scale approximates to be 57.000 TW/year, where the offshore contribution estimates 25.000-30.000 TW/year. Therefore, theoretically spoken, wind energy could cover all energy there is necessary.

The question is how will global energy consumption will be. The fact that energy consumption is always in increase is obvious. That is why the International Energy Agency provides an approximated 5.8 million megawatts until 2020 from 3.3 million in 2000.

The average annual wind velocity in Romania

Orography and the airs thermal stratification directly influence the wind’s velocity. Thus, on the mountain zone the average annual wind velocity is 8 – 10 m/s on the Carpathian peaks (2000 – 2500 m), at lower altitudes it will have a 6 m/s at 1800 – 2000 m and it reaches 1 – 2m/s in the depression zone. In the Carpathic interior curve, in Moldova the wind’s speeds are 4 – 5 m/s, and measuring the annual average top speeds in the eastern part of the country, in Câmpia Siretului the speed stands at 5 – 6m/s, and at the Black Sea’s shore (6 – 7 m/s). The highest wind speed values measured in Romania are on the mountain peaks. In Podișul Moldovenesc, Bărăgan’s north-east and the mountains of Dobrogea, where the winds velocity gets up even to 40 m/s. Likewise, at the Danube’s Delta, the Transylvanian plateau and in the northern part of the vest plain and Mureș rivers lane the annual wind speeds are between 20 – 30 m/s. Based on the evaluations and the interpretations of the data resulted from measurements, the energetic potential in Romania is the most favorable on the Black Sea’s shore, at the mountain zones and at the Moldova and Dobrogea’s plateau.

Fig. 2.1 Average annual wind speed in Romania

The table below presents an annual RES potential in Romania.

Table 3.

Central region’s geographical, physical characteristics and climate analysis

The study of geographical distribution of wind speeds, characteristic parameters of the
wind, topography and local wind flow and measurement of the wind speed are very
essential in wind resource assessment for successful application of wind turbines. Forwards, a brief study describes these aspects for Romania’s Central region.

In this region is the interior of the Carpathian curve, formed from six counties: Alba, Brașov, Covasna, Harghita, Mureș and Sibiu (Fig. 2.2). This region’s relief contains important parts from the Romanian Carpathian Mountains, the Transylvanian plateau and the contact depressions between the hills and mountains. The mountain-zone takes over 47% of the given territory; here are situated the Moldoveanu (2544 m) and the Negoiu (2535m).

The regional particularities of the wind are:

The mountain peaks over 1700m where wind speed can reach up to 20 m/s. It has been observed that local orography determines wind to deviate to the valleys. In Brașov county, in Bran and the lowlands of Bârsa dominates the North-West wind, meanwhile in Făgăraș plateau blows the West wind.

The mountain and the valley breeze have good frequency in Apuseni Mountains and in the Oriental Carpathian Mountains, which are found in the studied zone.

Because geographical means the central region of Romania has a shielded climate. Thanks to the influence of the Atlantic Ocean, in this zone there is an important wind potential. The Geographic Information System (GIS) analyzes the wind potential for the central region of Romania. The Climatologic Atlas of Romania (1970) was used to complete the most important meteorological parameters. This study uses two interpolation methods: Natural Neighbors and the Kriging method. Kriging is “an advanced geostatistical procedure that generates an estimated surface from a scattered set of points with z-values. Unlike other interpolation methods in the Interpolation toolset, to use the Kriging tool effectively involves an interactive investigation of the spatial behavior of the phenomenon represented by the z-values before selecting the best estimation method for generating the output surface”. [V.] The Natural Neighbor method is “a geometric estimation technique that uses natural neighborhood regions generated around each point in the data set.” [X.]

To verify the zones that have wind potential it is important to consider the following criteria:

to provide constant wind speed for the wind turbine

to dispose the wind turbines on low profile hills and round heights

to assure a good air circulation over the entire year

to avoid rough terrain

to consult the meteorological maps with the high annual frequency of the wind

to lower the wind variations in time as much as possible.

In modern world, the extraction of power from the wind with modern turbines and energy conversion systems is an established industry. Thus, manufacturing WT is possible in a range varying from tens of watts to several megawatts, and diameters of about 1 m to more than 100 m. Based on these measurements the following maps had resulted (Fig. 2.3 – Fig. 2.9). These maps shows the average annual wind speed (Fig 2.3); the atmospherically calm, small speed, medium speed and high wind speeds (Fig 2.4); the dominant wind’s average speed (Fig 2.5) according to the 4 factors given above (Fig 2.6); the wind’s potential map (Fig. 2.7); the detailed wind’s speed considered in Romania’s central part (Fig 2.8 and Fig 2.9). [21.REG – 2010]

Fig. 2.2 Romanian counties map, where Central Region of Romania is marked with red dot. [III]

Fig. 2.3 Central Region of Romania. Annual average wind speed given by the dominant direction of the wind.

Fig. 2.4 Central Region’s average wind speed categorized by four (4) major criteria: atmospherically calm, small speed, medium speed and high wind speeds.

Fig. 2.5 Central region. Average dominant wind’s speed frequency map.

Fig. 2.6 Central region. Wind speed’s frequency map evidenced for the 4 dominant factors.

Fig. 2.7 Central region. Wind’s potential map

Fig. 2.8 Central region wind’s speed (m/s)

Fig. 2.9 Central region’s wind potential map

These maps emphasizes the wind potential. The Climatologic Atlas of Romania inspires the meteorological data processing. The wind’s velocity and the wind’s frequency were interpolated by the two interpolation methods: the Natural Neighbors and the Kriging method. Natural Neighbors (NN). creates a Delaunay triangulation of on the input points and selects the easiest modes to form a convex shell around the interpolation points. Afterwards, it is computed the area. The Kriging interpolation method assumes that the distance between the given points and the spatial arrangement contributes to the generation of the final surface. Kriging uses a mathematical formula and a number of points localised in a given area to interpolate for every location found to be interesting. Kriging uses a multistep process including a statistic data analysis and a variographic modelling, which creates a possible surface. The variogram means a structural analysis, which is used to obtain the spatial model.

The most important zones with wind potential are the Făgăraș Mountains, Brașov’s county south and some hidden areas in Apuseni Mountains.

Conform to the maps, in Brașov area there is an annual wind speed between 3.90 – 7.10 m/s, a big wind potential, and a good frequency of wind.

Negoiu Impex project manufacturer published a wind potential evaluation in Brașov area. The following information, extracted from this study is given.

The considered zone was Brașov, its vicinity, and Poiana Brașov. Two zones found to be interesting: the Tâmpa and the Postăvarul peak (Fig2.10.). For this study, the ANM map (1Administratia Națională de Meteorologie (RO), National Meteorological Administration System (EN) [IX.]) was used which contained the average wind speed at 50m altitude and a map at 60m developed by Al-Pro German Company. The investment was evaluated between 30.000 – 50.000 Euros. After a brief study, the conclusions are the following:

In the case of Tâmpa, at 120m, the wind speed is 4.1m/s and at 60m is only 2.0 m/s. This is not a recommended for such a financial investment, because it could return only in 39.3 years.

Considering the Postăvarul peak, using the, the Al-Pro German group’s map at 60m and 120m, the annual average wind speed is much higher than at Tâmpa, respectively 6.1m/s at 60m and 7m/s at 120m.

The results are given in Table 3.

Fig. 2.10 Studied zones viewed on Google Maps (marked with red dots)

Table 3 Wind speed at Tâmpa and at the Postvărul

Quoting the information from 3TIER Company it is found out that at Postăvarul there is a 74% wind potential, which is equal with the one from Fântânele, Cogealac, Dobrogea, Constanța county where already have been made large investments that cumulated up to 400 million Euros. [18. OCT – 2012]

Fig. 2.11 Comparison between Postăvarul and Fântânele, Constanța

CHAPTER 3

Emulation of a wind turbine

The present project studies the implementation of a wind-turbine emulator. This has the purpose to enlarge the viewer’s experience about how wind-energy harnessing is possible and justify a WT implementation at Postăvarul peak in a certain area. The setup includes the following components: a kitchen hood’s fan (Fig.3.3), an AC motor and its command system (Fig. 3.1; Fig 3.2), a DC fan (Fig.3.4) and an enclosure (Fig.3.5), which holds all these components.

The construction of the enclosure is in such manner, that the wind has the best output speed. The top of the enclosure also has a metallic grid (Fig 3.7). This grid enables slight variations of the electric energy produced by the DC fan. Gradually closing this vent blocks partially the airflow. This leads to heating, especially in the inside of the motor (the moving parts), producing possible damages in time.

The WT emulator components, highlighted in the following figures are below.

Fig.3.1 The main rotor

Fig.3.2 The main stator

Fig.3.7 LED lamp

For a simpler visualization of the emulating system, a virtual 3D wind-emulator model is proposed. This model resembles the emulator’s working principle, as will be shown.

The system has the following main components:

AC monophased motor;

main fan (on the motor’s shaft);

electrical switch;

secondary fan (resembles the wind turbine’s blades).

All the components are in a wooden case (Fig.3.6).

Fig.3.8 Virtual emulator. 1 – DC fan (12V), 2 – main wind generator fan, 3 – two speed switch, 4 – main motor, 5 – air-out grid.

Fig.3.9 shows the wind’s path in the emulator.

Fig.3.9 The inner aircirculation

In the emulators design the path of the wind was optimised to maximum capacity.

The operation mode of the emulator is:

The main motor, plugged to the AC power supply (the grid).

The main fan, started by an electrical switch will create the necessary air-flux.

Therefore, the secondary fan will start rotating, producing a DC voltage.

The secondary fan, connected to a simple LED lamp (Fig.3.7). The lantern’s purpose is to simulate a consumer behavior connected to a WT. The switch has two operating modes: one for low speed, and one for the highest speed debited by the motor. At lower speed, there are 1400 rpm’s, while at the highest speed 2450 rpm. This makes possible a detailed study over wind energy potential even at a lower scale.

The main motor parameters are in the following table:

Table 3.1

The DC fan main parameters are:

Single-phased motor mathematical model

Since in the emulator implements a single-phased asynchronous motor, a mathematic model of the single phased induction machine is analyzed.

Modelling of a single-phased induction machine, developed for the commonly type, refers to a squirrel-cage motor (Fig.3.10). Building the model means on one distributed stator winding and two equivalent rotor windings, modelling the squirrel cage. The single-phase induction-machine does not produce a torque at standstill; in this case, it needs an auxiliary winding to produce a non-zero starting torque that will cause the shaft to accelerate to near synchronous mechanical speed at no load.

A fifth-order differential model of the single-phase induction motor in rotor (a, b) coordinates is given below [4. DAN – 2012].

3.1

3.2

3.3

3.4

3.5

Where the label s denotes the stator winding, and the labels ra and rb denote the rotor phase-a, and phase-b windings. The variable λs is the stator flux and λra and λrb are the rotor fluxes of phases a, and b.

Fig.3.10. Squirrel cage motor main components

The electrical angle between the stator winding and the phase-a rotor winding defined as θ, and the electromagnetic torque and the mechanical load torque are defined as Te respectively Tm.

The flux relations given by the following equation are:

3.6

Where Lls and Llr are the stator and rotor leakage inductances and Lms is the stator magnetizing inductance. For an electrically linear machine, the magnetic co-energy is equal to:

3.7

Using equation 3.7, the co-energy, expressed in terms of inductances is:

3.8

The Te electromagnetic torque developed by the machine given by the equation below:

3.9

, where θm represents the mechanical angle of rotation related to the electrical angle θ by

3.10

Where p is the number of poles per phase. With these considerations, T electromagnetic torque equals

3.11

3.3 Experimental data and results interpretation

In this study, the measurements taken in consideration are:

Output DC current

Output DC voltage

Debited energy (calculated)

Calculated Power

The following table highlights the results extracted from measurements.

Table 3.2. The secondary DC fan output parameters

The computation of debited energy is possible by the following formula:

3.12

3.13

For example, in the second case the debited energy equals to

The speed of the wind, measured in Brașov area is for this study’s relevance. The procedure implemented using the Zephyrus Android application from Play Store®, which uses the mobile phone’s microphone to compute the speed of the wind. Therefore, consider a 2% measurement uncertainty. The results are below as graphic charts. The places where measurements took place are:

Astra Marketplace (Fig 3.10);

Bucharest Street (Fig 3.11);

Tâmpa peak (Fig 3.12);

Postăvarul peak (fig 3.13).

The graphic chart’s main window has the following components: momentary wind speed; smallest wind speed; average value calculated considering all the measurements and maximum wind speed.

Astra marketplace the following data had been obtained

Fig.3.10

Bucharest street the following data had been obtained

Fig.3.11

At Tâmpa peak At Postăvarul peak

Fig.3.12 Wind speed at Tâmpa peak and at Postăvarul peak

These measurements took place at ground level.

The wind’s speed created by the main motor’s, using the same procedure is shown below.

Fig.3.13 Wind speed obtained at 2450 rpm and at 1400 rpm

The WT emulator supplies an LED lamp, as an electrical receptor. The following data was obtained.

Light’s flux at 1400 rpm Light’s flux at 2450 rpm

Fig.3.14 Light’s flux at 1400 rpm, respectively at 2450 rpm

Because the fan has two different speeds, the LED lamp light flux obtained as output parameter will have two values, as expressed. To measure the flux of the light the Light Meter is used, which is an app from Play Store®. The results obtained are 107 lx at 1400 rpm, and 661 lx at 2450 rpm.

A possible application of the WT implemented in Postăvarul area is the power supplying of the touristic cable car.

Summarizing Table for the wind speed measurements in different places of Brașov for a short-time period

Table 3.3

Barriers to develop investment projects in renewable energy

The WT emulator used in this study did not consider all the opponents that could appear in real life when it comes about building a wind-plant. For example, the wind’s force in the given case is constant. Therefore, must consider the following barriers in developing investment projects in RES, mostly related to wind energy issue.

There are many barriers, which constitutes most of the challenges for development of investment projects in the energy sector, especially in developing projects that focus on renewable energy 3. [COR – 2011] E. [PÉT – 2014] F. [SUA – 2013].

Firstly, to be mentioned, administrative barriers:

Insufficient spatial planning in some circumstances,

Nimby attitude (it stands for “not in my back yard”),

Troublesome procedures (authorization time),

Too many authorities involved.

Thirdly, technological barriers examines issues such as lack of technical skills, lack of information on new technologies, overall complexity, maintenance of the components, choosing the wind turbine’s proper regulation type, power grid connection, hazardous situations related to environmental and operating conditions. A. [IBR – 2011] B. [KLU – 2014]

Fourthly, a few of the market barriers are the size of investment project cost of energy transportation from renewable sources, restricted access for new competitors, etc.

As any technical system, the wind-energy harnessing has advantages and disadvantages.

The most widely emphasized pro and contras are the following [CON – 2009], [OTT – 2012], [MĂD – 2014], [JAN – 2009].

Pro – arguments:

renewable energy;

low maintenance cost;

less residual waste materials;

green energy;

competivity in the energy market;

potential of energy storage

Contra – arguments:

volatile production of wind potential;

hard to estimate the wind potential;

disturbing noise for the environment;

birds are endangered;

the size of investment projects;

cost of energy transportation from renewable sources;

All these represent an obvious barrier, but some could ameliorate. For example, if lack of technical skills is a problem in the present, in the future this could solve out.

SWOT analysis of the project Table 3.4

CONCLUSION

The present project consisted from a study regarding the wind energy as potential solution to implement RES systems in Brașov, Romania. The aim of this paper was to continue the researches and to develop a simulation through a WT emulator, which was achieved.

It was built at a smaller scale a WT emulator that revealed the following results: demonstrates the possibility of wind harnessing because the emulator generate electrical energy at a speed of 2450 rpm, equivalent at a wind speed of 7 m/s, as the one recorded at Postvărul peak. These results demonstrate the possibility for a LED lamp to lighten at 661 luxes with an energy consumption of 0.36 Wh, taking into account a DC generator with an electrical power of 2.2W. The LED lamp resembles a consumer. At this scale, this is a considerable significance, which resulted from an output voltage of 3V at 10 mA DC.

Especially in Brașov area, at the Postvărul peak, it is a great possibility to build up a wind system. This solution, energetically spoken could optimize the electrical consumption of the cable car system by producing electrical energy. Although this solution has a higher initial cost, it is a feasible solution for Brașov city, especially because this would mean an energetic development, to promote Brașov at a higher technical and cultural position. This solution, estimated at 30.000–50.000 Euros would bring good results, compared to 400 million Euros invested at Fântânele-Constanța. A successful implementation will lead to development of other similar projects, growing tourist attraction, having an affordable financial amortization.

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ANNEXES

Estimation of a Vestas WT built by Kogaion software for Postăvarul

Estimation for a 100m diameter Vestas WT at Postăvarul

Measurement of the rotation speed

LED lamp’s test