Energy Conversion and Management 47 (2006) 1326–1337

www.elsevier.com/locate/enconman

A small wind turbine system (SWTS) applicationand its performance analysis

Onder Ozgener *

Solar Energy Institute, Ege University, 35100 Bornova, Izmir, Turkey

Received 17 February 2005; accepted 25 August 2005Available online 5 October 2005

Abstract

Energy conservation, pollution prevention, resource efficiency, systems integration and life cycle costing are very impor-tant terms for sustainable construction. The purpose of this work is to ensure a power supply for the north of the SolarEnergy Institute building environment lamps by using wind power to comply with the green building approach. Beside this,the study is to present an energy analysis of the 1.5 kW small wind turbine system (SWTS) with a hub height of 12 m aboveground level with a 3 m rotor diameter in Turkey. The SWTS was installed at the Solar Energy Institute of Ege University(latitude 38.24 N, longitude 27.50 E), Izmir, Turkey. NACA 63-622 profile type (National Advisory Committee forAeronautics) blades of epoxy carbon fiber reinforced plastics were used. The system was commissioned in September2002, and performance tests have been conducted since then. The performance analysis of the SWTS is quantified and illus-trated in the tables, particularly for a reference temperature of 25 �C, 30th of October 2003 till 5th of November 2003 forcomparison purposes. Test results show that when the average wind speed is 7.5 m/s, 616 W and 76 Hz electricity is pro-duced by the alternator.� 2005 Elsevier Ltd. All rights reserved.

Keywords: Energy; Environment; Exergy; Renewable energy; Sustainable development; Wind; Wind energy

1. Introduction

Energy conservation, pollution prevention, resource efficiency, systems integration and life cycle costing arevery important terms for sustainable construction. Besides, these principles include: (i) minimizing non-renew-able resource consumption, (ii) enhancing the natural environment and (iii) eliminating or minimizing the useof toxins, thus combining energy efficiency with the impact of materials on occupants [1]. Therefore, possibleuse of wind energy must be evaluated in terms of its impact on the environment.

Wind power is fun but not practical in most situations and is unlikely to perform well in built up areas dueto low wind speeds, turbulence etc. [2]. However, wind energy was the fastest growing energy technology in the1990s in terms of percentage of yearly growth of installed capacity per technology source. The growth of wind

0196-8904/$ - see front matter � 2005 Elsevier Ltd. All rights reserved.

doi:10.1016/j.enconman.2005.08.014

* Tel.: +90 232 388 4000/1242; fax: +90 232 388 6027.E-mail addresses: onder.ozgener@ege.edu.tr, onderozgener@mail.ege.edu.tr

Nomenclature

A rotor swept area (m2)CM momentum factor of rotor (–)Cp power coefficient (energy conversion ratio) (–)H height (m)Href reference height (m)I phase currents (A)R maximum rotor radius (m)Vr local wind velocity (m/s)V volt (V)VLL phase to phase voltage (V)VLN phase voltages (V)P available power (W)Pa actual power (active power at generator output) (W, kW)Pe power at inverter output (W, kW)Wa actual work of SWTS (kW h)Wteo theoretical work potential of SWTS (kW h)_m mass flow rate of air (kg/s)S apparent power

Greek symbols

x angular speed of rotor (rad/s)g efficiency (–)Dti yearly cumulative time (h/year)k tip speed ratio (–)q air density (kg/m3)l Hellman coefficient (–)P

total

Abbreviations

LCD liquid crystal displayNACA National Advisory Committee of AeronauticsPBL planetary boundary layerPF (cosW) power factor (–)SWTS small wind turbine (windmill) system

O. Ozgener / Energy Conversion and Management 47 (2006) 1326–1337 1327

energy, however, is not evenly distributed around the world. By the end of 2001, the total operational windpower capacity worldwide was 23,270 MW. Of this, 70.3% was installed in Europe, followed by 19.1% inNorth America, 9.3% in Asia and the Pacific, 0.9% in the Middle East and Africa and 0.4% in South and Cen-tral America [3].

Turkey has a considerably high level of renewable energy resources that can be a part of the total energynetwork in the country [4]. Turkey�s total theoretically available potential for wind power is found to be about88,000 MW. Besides this, Turkey�s wave power potential is estimated to be around 18,500 MW, with an aver-age wave energy capacity of 140 billion kW h annually. These figures indicate that Turkey has considerablepotential for generating electricity from wind and wave power [5,6]. Today, distributed small wind electric sys-tems can make a significant contribution to Turkey�s energy needs. To date, four wind power plants have beeninstalled with a total capacity of 20.1 MW in Turkey [6]. Because of the recent increase in the price of fossilfuels, it is becoming ever more costly to provide energy for our abodes, besides the fact that pollution is being

1328 O. Ozgener / Energy Conversion and Management 47 (2006) 1326–1337

created to provide this energy. This study aims to develop a more efficient and more useful SWTS (small windturbine system) for rural areas, increasing efficiency and decreasing the costs of stand alone and wind systemsin the Aegean Region, Turkey.

Renewable energy is abundant and its technologies are well established to provide complete security of energysupply [7]. Among renewable energy sources, wind energy plays an important role. From the late 1800s to theearly 1900s, thousands of US farmers and ranchers used windmills to pump water, grind grain, charge batteriesand provide power for radios, lights and washing machines. The use of windmills to provide electric power diedout in the early 1930s when the Rural Electrification Administration made cheap electricity generated at centra-lized power stations available to farms and ranches across the country. Today, the cost of electricity in manyareas is spiraling upwards and weak electrical grids make power to remote farms and ranches less reliable thanin the past. Even urban homeowners are faced with unexpected jumps in power costs [8].

Researchers estimate that 50% of the United States has enough wind resources for small turbine develop-ment and 60% of US homes are located in those wind resource areas. Using small wind turbines, farmers,ranchers and homeowners can reduce their utility bills, stabilize their electricity supplies and contribute tothe nation�s energy supply to play an important role in securing our energy future. Distributed wind electricsystems represent an opportunity for some nations, especially America households, to return to the energyindependence of a past century [8].

Wind energy applications have rapidly increased in the world, so the efficiency of wind energy constructionsare getting important. Theoretically, the maximum efficiency of wind energy conversion is 59.2% according tothe Betz Criteria [9]. Today, the available wind energy conversion efficiency reaches about an average of 40–45% in modern wind turbine types.

There are two basic classes of windmill design: horizontal axis and vertical axis. Conventional windmillsspin on a horizontal axis. The rotor, or spinning part of the windmill, is the most important part becauseit determines how much energy a windmill can capture and transform into some other form of energy.

The rotating blades depend on either of two aerodynamic principles to derive power from the wind: drag orlift. Drag devices are simple wind machines that use flat, curved or cup shaped blades to turn the rotor. Inthese, the wind merely pushes on the cup or blade, forcing the rotor to spin.

Lift devices, in contrast, use airfoils like those in the wing of an airplane to propel the rotor. Air flowingover the blade causes both lift and drag. As objects, like an airplane�s wings, move through the air, the air pullsagainst them and holds them back. This is called drag. Lift is caused by the wind moving at different speedsaround the wing. Faster moving air has lower pressure than slowly moving air. Slower air under the wingpushes it upward as lift. The sum of these two forces on a windmill�s blades generates a thrust that pullsthe blade on its journey through the air, much like it pulls a sailboat through the water. This thrust is greatestwhen the blade is slicing through the wind. Airfoil performance is determined by the ratio of lift to drag [10].

The NACA 63-nnn series blades can be preferred to other blades in applications for performance improve-ment because of the fact that these profiles have shown excellent properties for wind turbine blades, and theiraverage power coefficients are higher than those of other blades [11,12]. In this study, the performance param-eters of a wind turbine are given first. An experimental study is then explained. Finally, the results obtainedfrom the present study are discussed.

2. Test facility

2.1. Experimental setup

A test facility was constructed to study the requiring electricity needs of the environment lights of the SolarEnergy Institute during night conditions. The consumed energy for environment lights purposes depends onthe seasons and the daily changing climatic conditions. A schematic diagram of the constructed experimentalsystem is illustrated in Fig. 1. A horizontal axis wind turbine having three epoxy carbon fiber reinforced plasticbladed rigid hub was constructed, including complete units of the SWTS, at the Solar Energy Institute in EgeUniversity, Izmir (latitude 38.24 N, longitude 27.50 E), Turkey. The main characteristics of the elements of theexperimental setup are given Table 1. The experimental system consists of five major parts as follows: (a) elec-tronics: charge controller, power conversion, inverter, charger, warmth control equipment, thermocouple

20 W20 W20 W20 W20 W

3 m

12m

50H

z22

0V

AC

Ground level50 Hz 220 V AC50 Hz 220 V AC50 Hz 220 V AC50 Hz 220 V AC

90-1

85V

32-1

00H

zA

C

Win

d

AC/DC/AC96/220V

2m

Fig. 1. A schematic of the SWTS.

O. Ozgener / Energy Conversion and Management 47 (2006) 1326–1337 1329

(thermic), (b) storage batteries, (c) mechanics: tower, nose cone, yaw bearing, slip rings, tail, vane, nacelleassembly, (d) 1.5 kW non-synchronous generator (alternator) and blades, (e) environmental energy saving fivelamps with total power 100 W and (f) five moving and light sensors for energy saving.

2.1.1. Non-synchronous generator (alternator)Alternator are designed to charge (storage) batteries (accumulators). The alternator converts the mechan-

ical (rotational) energy of the rotor into electricity (three phase alternating current). The magnets are in therotor, which allows suppression of the rings and brushes for connection. The number of poles (30) improvesthe alternator performance at low speed, increases the mechanical parts life and reduces the noise level [13].

2.1.2. Rotor system

The rotor system consists of three NACA 63-622 blades made of carbon fiber and epoxy. Its profile [14–21]allows the efficient conversion of wind linear movement in to alternator rotational movement.

2.1.3. Tail

The tail keeps the rotor aligned into the wind except when the wind speed exceeds security limits. When thishappens, the special articulation system turns the rotor sideways to the wind to limit the rotor speed in highwinds, but the turbine continues producing power [13,22].

2.1.4. Tower

The random or stochastic nature of wind is the single most unique design constraint that differentiates windturbines from aircraft designs. The majority of today�s wind turbines operate within the first 100 m of theearth�s surface. This region, which occupies the lowest portion of the planetary boundary layer (PBL), is ex-tremely turbulent and driven by variations that occur with the diurnal changes in the atmospheric boundaryconditions. The vertical variation of temperature and wind speed with height defines the PBL behaviourcharacteristics.

The tower location and height are the principal factors for system efficiency. The wind average speed de-pends on many parameters and can vary a lot in the same area. The wind laminar flow over the earth�s surfaceis disturbed by many obstacles and topographic variations. This has two consequences: wind speed decreasingnear the earth and turbulences, both of which diminish as the height increases. A reasonable security margin is10 m above any obstacle within 100 m. Even in smooth areas, 10 m is advisable [21–26].

Table 1The main characteristics of the elements of the SWTS system studied

No. Item Three bladed rigid hub system

1 Aerodynamic profile form NACA 63-6222 Manufacturing material of blade Epoxy carbon resin3 Mold used to manufacture blade Steel4 Material ratio of blades 50% epoxy resin, 50% carbon fiber5 Tensile strength (MPa) 900a

6 Average blade weight (g) 13007 Number of blades 38 Rotor diameter (m) 39 Maximum power (W) 1500b

10 Maximum power wind speed (m/s) 12b

11 Cut in velocity value (start up wind speed) (m/s) 2.4b

12 Cut off velocity (limiting wind speed) (m/s) 18b

13 Theoretical maximum power factor value (–) 0.4531b

14 Maximum energy conversion (power factor) ratio (–) 0.3515 Height of hub (m) 1217 Roughness of blade surface Clean18 Theoretical profile tip loss efficiency (–) 0.91219 Theoretical profile loss efficiency (–) 0.8822 Power factor range 0–0.3524 Brake system Mechanical25 Generator (AC alternator) 1.5 kW non-synchronous generator/3 phase26 Power systems AC/DC/AC and 3 kW inverter27 Inverter input voltage (V) 9628 Inverter output voltage (V) 22029 Inverter output frequency (Hz) 5030 Generator average cosW [power factor (PF)] 0.6231 Batteries� charging voltage (

PV) 100

32 Batteries� charging current (P

A) 2233 Charge controller disconnect voltage (V) 10634 Accumulators (batteries)/unit 65 Ah 12 V/835 Alternating current in environment lights (

PA) 0.54

36 Alternating voltage in environment lights (V) 22037 Total power of environment lights (W) 10038 Generator frequency (Hz) (at 4.3 m/s wind speed) 30b

39 Generator average alternating voltage value(P

V) (at 260 rpm and 10 m/s wind speed)139

40 Range of rpm of rotor 60–320b

41 Mechanical efficiency of system (–) 0.9742 Generator efficiency (–) 0.9843 Inverter and power group efficiency (–) 0.9844 Gear system efficiency (–) –45 Estimated average decibel value (10 m from hub

and average 5.5 m/s wind velocity)50

a Theoretical maximum value [13].b Production value [13].

1330 O. Ozgener / Energy Conversion and Management 47 (2006) 1326–1337

2.2. Measurements

The following data were regularly recorded with a time interval of 15 min during the experimental period30th of October 2003 till 05th of November 2003.

(a) Measurement and monitoring on a LCD display of instantaneous power generations of the alternatorand all electrical parameters by using the electronic energy analyzer.

(b) Measurement of wind velocities at the ground level by anemometer, and then, these values were calcu-lated for 12 m by using the Hellmann equation.

O. Ozgener / Energy Conversion and Management 47 (2006) 1326–1337 1331

(c) Uncertainty analysis is needed to prove the accuracy of the experiments. An uncertainty analysis wasperformed using the method described by Holman [27].

Daily average values of 37 measurements from 8.30 a.m. to 4.00 p.m. with an interval of 15 min were re-corded. The total uncertainties of the measurements are estimated to be ±1.30% for the wind velocities,±1.02% for the voltage and current in the system and ±3.03% for the power factor.

2.3. System operation

The rotor begins to rotate (spin) when the wind speed reaches approximately 2.4 m/s (8.64 km/h). Batterycharging commences at a slightly higher speed, depending on the battery state of charge. When the battery isfully charged, the charge controller disconnects the turbine from the battery. The turbine produces a threephase alternating current (AC) that varies in voltage and frequency as the wind speed varies. The controller(regulator) rectifies this AC into the direct current (DC) required for battery charging and controls the energysupplied to the batteries to avoid overcharging. The SWTS has electronic energy analyzers that show everysystem status data (phase voltages (VLN), phase currents (I), total current (

PI), power factor (PF) cosW,

apparent power etc.).

3. Analysis

Designing wind turbines to achieve satisfactory levels of performance and durability starts with knowledgeof the aerodynamic forces acting at the critical interface between wind and machine.

The efficiency of a wind turbine is usually characterized by its power coefficient as given below. The max-imum possible value of Cp is 0.5926 according to the Betz criterion.

Cp ¼I � V

gmechanic � galternator � 0:5qpR2V 3r

¼ P a

Pð1Þ

where Cp is the power coefficient of a wind turbine. The power coefficient is given by Eq. (1). In this study, theelectrical equipment and mechanical equipment losses were assumed to be galternator = 0.98 and gmechanic =0.97, respectively.

The power performance of a wind turbine can be expressed for fixed angular speed. This parameter is de-fined by

CM ¼Cp

kð2Þ

Wind turbines indicate various Cp values depending on the wind velocities. Therefore, their efficiency is bestrepresented by a Cp–k curve. The tip speed ratio k is given by

k ¼ xRV r

ð3Þ

where k is the tip speed ratio, R is the maximum rotor radius (m), x is the rotor speed (rad/s) and Vr is thewind velocity (m/s).

The air flowing as wind has the same properties as the stagnant atmospheric air except that it possess avelocity and, thus, some kinetic energy. This air will reach the dead state when it is brought to a complete stop.Therefore, the availability of the blowing air is simply the kinetic energy it possesses:

Exergy of kinetic energy ¼ availability ¼ ke1 ¼V 2

r

2ð4Þ

To determine the available power, we need to know the amount of air passing through the rotor of thewindmill per unit time, the mass flow rate. Assuming standard atmospheric conditions (25 �C, 101 kPa) in thisstudy, the density of air is 1.18 kg/m3, and its mass flow rate is

_m ¼ qAV r ¼ qpR2V r ð5Þ

1332 O. Ozgener / Energy Conversion and Management 47 (2006) 1326–1337

Thus,

available power ¼ P ¼ ð _mke1Þ ð6Þ

This is the maximum power available to the windmill. Most windmills in operation today harness about 20–40% of the kinetic energy of the wind [28].

Kinetic exergy is a form of mechanical energy, and thus, it can be converted to work entirely. Therefore, thework potential or exergy of kinetic energy of a system is equal to the kinetic energy itself regardless of thetemperature and pressure of the environment [28].

Any measured wind velocity value can be estimated for different heights by using the following Hellmannequation [29]

V r ¼ V ref

HH ref

� �l

ð7Þ

where Vr is the calculated wind velocity and Vref is the wind velocity at the reference height. In this study, theHellmann coefficient (l) was assumed to be 0.28 [30] because the tower location is near the city.

4. Results and discussion

Ideally, applied research activities (field testing) should be conducted by several technical disciplines, suchas; aerodynamic, materials, structures, fatigue, meteorology, aero acoustics, control and power systems andmanufacturing, e.g., [31–50].

The random or stochastic nature of wind is the single most unique design constraint that differentiates windturbines from aircraft designs. The majority of today�s wind turbines operate within the first 100 m of theearth�s surface. This region, which occupies the lowest portion of the planetary boundary layer (PBL), is ex-tremely turbulent and driven by variations, which occur with the diurnal changes in the atmospheric boundaryconditions. The vertical variation of temperature and wind speed with height defines the PBL behaviour char-acteristics. During normal daytime turbine operations, the temperature normally decreases with height, whichcontributes to a convectively unstable atmosphere. Under these conditions, the largest and most energetic tur-bulent motions are associated with convective edges or cells that are many times larger than even the largestwind turbines. The large eddies actively mix with and absorb the smaller, more compact turbulent structuresthat have a more direct impact on rotating wind turbine blades.

In contrast, a stable boundary layer is characterized by warmer air overlaying cooler air in contact with theearth�s surface. Under such conditions, coherent or organized turbulent structures can develop, which canexist for long periods of time due to the lack of the large scale, vertical mixing characteristic of unstable flows.These structures can be quite intense and, depending on their size and orientation, are capable of inducinglarge structural loads when flowing into the spinning rotor of a wind turbine. Interestingly, a disproportionatenumber of hardware failures have occurred during evening operations, attesting to the potential severity ofthis inflow condition on turbine performance, e.g., [21,23–26].

There are three basic methods of testing wind turbine rotors; wind tunnels testing, tow testing and field test-ing. Field testing presents the proper wind environment, but it brings new challenges in measuring and record-ing test data. The method that was used in this case greatly smoothes the resulting graph of the power curve(Fig. 2).

The performance data from the wind turbine are stored. Output power and wind speed are sampled overperiods of time, and average values of wind for each period are stored as wind speed.

One of the significant measures of the cost effectiveness of a wind turbine is its production of energy. In thedesign and analysis of wind turbines, the annual energy output is calculated. Calculation of annual energy out-put requires knowledge of the wind speed frequency distribution and the system power output of the turbineas a function of wind speed, as shown in Table 2. Furthermore, every prediction of annual energy output isspecific, depending on the local wind flow patterns and turbulence and the local air density [19,21].

Table 2 illustrates using design performance data for the NACA 4415 [19] and also the NACA 63-622 bladeprofiles. Wind velocities of 1998 were taken from the Colak et al. research project [51]. When the average windvelocity was calculated for the entire year, it was found to be approximately 3.22 m/s in the field of the Solar

1600

1400

1200

Pow

er (

W)

1000

800

600

400

200

00 2 4 6 8 10 12 14 16 18

Wind speed (m/s)

1000

1200

1400

1600 0.4

Pow

er f

acto

r (-

)

Pow

er (

W)

0.3

0

200

400

600

800 0.2

0.1

01 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Wind speed (m/s)

a

b

Power factor Power

Fig. 2. Measured power curves of (a) alternator and (b) SWTS.

Table 2Typical calculation and theoretical results of blade groups: average energy production

Blade Group I (NACA 63-622 profile and made of epoxy carbonresin)

Blade Group II (NACA 4415 profile and made of GRP)

Windspeed(m/s)

DurationDti (h/year)

Wind speedfrequency(%)

Yearlyaveragewind speed

Net energyoutput(kW h/year)

Windspeed(m/s)

DurationDti (h/year)

Windspeedfrequency(%)

Yearlyaveragewindspeed

Net energyoutput(kW h/year)

0–2.5 4234 48.33 – 0 0–6.5 8454 96.51 – 03.5 1348 15.39 – 86.680 7.5 197 2.25 – 90.3224.5 1422 16.24 – 194.341 8.5 76 0.86 – 50.7245.5 975 11.13 – 243.287 9.5 18 0.21 – 16.7716.5 475 5.42 – 195.641 10.5 13 0.15 – 16.3557.5 197 2.25 – 124.646 11.5 2 0.02 – 3.3058.5 76 0.86 – 70 – – – – –9.5 18 0.21 – 23.146 – – – – –10.5 13 0.15 – 22.570 – – – – –11.5 2 0.02 – 4.562 – – – – –

Total 8760 100 3.22 964.873 – 8760 100 3.22 177.477

O. Ozgener / Energy Conversion and Management 47 (2006) 1326–1337 1333

Energy Institute, as listed in Table 2. Using the values given in Colak et al. [51], the wind speed frequencies aredetermined and illustrated in Table 2.

For analysis purposes, the actual data for energy analysis and performance assessment purposes were takenfrom the SWTS, and the respective physical and thermodynamic properties were obtained based upon thesedata. Tables 3 and 4 show the measured and calculated performance parameters average values of the SWTSduring the experimental period 30th of October 2003 till 05th of November 2003. The daily average values of37 measurements from 8.30 a.m. to 4.00 p.m. with an interval of 15 min were taken. The total uncertainties of

Table 3Measured and calculated performance parameters average values of the SWTS

Vr Cp _m ke1 PðW Þ ¼ _mke1 Pa(W) = Cp * P Pe Vr Dtia

(h/year)Wind speedfrequency(%)

Wteo

(kW h/year)Wa

b,c,d

(kW h/month)

2.4 0.18 20.01 2.88 57.63 10.38 9.16 0–2.5 4234 48.33 0 September–October/10e

3.1 0.2 25.86 4.8 124.13 24.8 21.9 3.5 1348 15.39 86.680 November/15e

4 0.24 33.36 8 267 64 56.5 4.5 1422 16.24 194.341 December/9.84.5 0.28 37.53 10.13 380.18 106.45 94 5.5 975 11.13 243.287 January/11.4e

5.5 0.3 45.88 15.13 694.16 208.3 183.9 6.5 475 5.42 195.641 February/10f

7.5 0.35 62.56 28.13 1760 616 544.1 7.5 197 2.25 124.646 March/20.68 0.33 66.73 32 2135 704.55 622.31 8.5 76 0.86 70 April/9g

9 0.3 75.06 40.5 3040 912 805.55 9.5 18 0.21 23.146 May/8g

10 0.25 83.4 50 4170 1042.5 920.82 10.5 13 0.15 22.570 June–July/9g

12 0.21 100.09 72 7206 1513 1335 11.5 2 0.02 4.562 August/9g

Total 8760 100 964.873 111.8

a Measured value [51].b Measured value between September 2002–August 2003.c Months.d Monthly useful work potential of the SWTS.e Moving and light sensors was used on lights for saving energy.f SWTS in maintenance.g Monthly average wind speed very low for producing electricity at 12 m.

1334 O. Ozgener / Energy Conversion and Management 47 (2006) 1326–1337

the measurements are estimated to be ±1.30% for the wind velocities, ±1.02% for voltage and current in thesystem and ±3.03% for the power factor. Tables 3 and 4 tell us about generalizing the seven days performanceof this machine into annual performance because the hourly averages of wind speed, direction and frequencycharacteristics approximate the yearly wind regime in the Bornova-Izmir vicinity. In addition, 2002/2003 sea-sonal performance effects can be seen from the last column in Table 3. The theoretical useful energy is found as964.873 kW h (corresponding to measured 1998 wind velocity speeds), however the actual seasonal perfor-mance useful energy was measured as 111.8 kW h from September 2002 to August 2003. The main reasonis the large low wind speed frequency distribution; moving and light sensors were used on lights for savingenergy; and the SWTS was down for maintenance some days. Whole actual useful energy values were recordedby using the electronic energy analyzer in the system. As expected, lower average wind speed, minimum energystorage in the batteries and minimum actual useful energy was obtained in May. Furthermore, the perfor-mance test results are given Table 4. When the average wind speed is 7.5 m/s, 616 W and 76 Hz. electricityis produced by the alternator, but the power consumption value every time is constant because the totalpower, voltage and currents of the environment lamps are 100 W, 220 V and about 0.5 A, respectively.

The experimental results show that monovalent central lighting operation cannot meet the overall energyneeds of the Solar Energy Institute building environment lamps if the wind speed is very low. Bivalent oper-ation (combined with other lighting systems) can be suggested as the best solution in the test location if thepeak energy load can be easily controlled.

By comparison, in a study performed by the author, the power factor value for the NACA 4415 bladedwind turbine was obtained to be 0.275 [9,19,52]. This clearly indicates that the performance of the NACA63-622 in terms of energy and exergy utilization efficiencies is better than that of the NACA 4415. One ofthe reasons for this is that the profile losses in the NACA 63-622 are lower than those in the NACA 4415.Energy and exergy performance safety was increased because,

Blade:

• A steel mold was used to produce a smooth surface.• A long and narrow airfoil was selected having a larger aspect ratio than the NACA 4415 blade.

Table 41.5 kW generator measured parameters

Measured parameters Wind velocities (m/s)

0–4.4 4.5 5.5 6.1 6.7 7.2 7.5 8.4 9 10 12 15 16 17 18

Alternator output

Phase voltages (VLN) Negligible 53 55 60 64 65 64 65 66 80 107 107 107 107 246Phase currents (I) Negligible 0.61 0.91 1.7 2.17 2.62 3.1 3.4 4.33 4.35 4.7 4.7 4.7 4.7 –Total current (

PI) Negligible 1.83 2.75 5.12 6.51 7.86 9.3 10.2 13 13.1 14.1 14.1 14.1 14.1 –

Power factor (PF), cosW Negligible 0.63 0.79 0.57 0.56 0.59 0.59 0.69 0.61 0.57 0.58 0.58 0.58 0.58 –Phase to phase voltage (VLL) Negligible 94 100 103 110 110 111 115 116 139 185 185 185 185 426Average phase to phase voltage Negligible 91.7 95.2 102 110 112 111 112 115 139 185 185 185 185 426Frequency (Hz) Negligible 32 35 38.8 47 51.2 76 79 91.6 95 100 100 100 100 –Total active powerP

P a ¼P

IV LL cos WNegligible 106 208 300 401 519 609 788 912 1038 1513 1513 1513 1513

Total apparent powerPS ¼

PIV LL

Negligible 168 262 522 716 880 1032 1142 1495 1821 2608 2608 2608 2608 –

96/220 V DC/AC Inverter output

Voltage 220 220 220 220 220 220 220 220 220 220 220 220 220 220 220Frequency (Hz) 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50

O.

Ozg

ener

/E

nerg

yC

on

version

an

dM

an

ag

emen

t4

7(

20

06

)1

32

6–

13

37

1335

1336 O. Ozgener / Energy Conversion and Management 47 (2006) 1326–1337

Location:

• Test location was selected according to local topography and was evaluated by the effects of buildings, treesetc.

Mean gear system:

• Direct fixed connection was used between the generator and rotor blades. This increased the Cp values dueto lower friction.

5. Conclusions

An experimental system was installed for investigating the performance of a SWTS to ensure a power sup-ply for the Solar Energy Institute building environment lights by using wind power. It has been satisfactorilyoperated without any serious defects in the experimental period. The results obtained during the 30th ofOctober 2003 till the 5th of November 2003 were given and discussed. The effects of climatic conditionsand operating parameters on the system performance parameters were also investigated. The experimentalresults indicate that these SWTSs can be used for producing electricity in the Aegean region of Turkey. Addi-tional conclusions drawn from the present study may be summarized as follows:

• A SWTS can provide a practical and economical source of electricity in the Aegean region because thisregion has a good wind resource.

• The number of years for simple payback is a function of the wind speed, annual energy production from theturbine, the manufacturer�s power curve and the installed costs of the SWTS.

• Changing just the blade design (airfoil) of the small wind turbine can increase the annual energy productionfrom the turbine and greatly improve the manufacturer�s power curve.

Acknowledgement

The author would like to thank the Ege University Research Fund, Fiberplast Inc., Fibrosan GRP Industryand Trade Inc., Ozmak Radio Antenna and Electronic Industry and Trade Inc., Sena Electronic Co. due totheir financial supports. In addition, Dr. Leyla Ozgener, for her help in performing the experiments, is alsogreatly appreciated.

References

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