Wind power potential and characteristic analysis of Chiang Mai, Thailand

Transcription

1 Journal of Mechancal Scence and Technology 24 (7) (2) 475~479 DOI.7/s Wnd power potental and characterstc analyss of Chang Ma, Thaland Tanate Chachana,* and Sumpun Chatep 2 Program of Energy Engneerng, Faculty of Engneerng, Chang Ma Unversty, 52, Thaland 2 PARA laboratory, Faculty of Engneerng, Chang Ma Unversty, 52, Thaland (Manuscrpt Receved l 22, 28; Revsed uary 23, 2; Accepted ch, 2) Abstract An nvestgaton of wnd characterstcs and wnd energy potental at Chang Ma Provnce, Thaland was studed. Wnd data taken from the weather staton at Chang Ma Internatonal Arport between 2-26 was analyzed n order to obtan the potental energy generated by a ertcal Axs Wnd Turbne (AWT). It was found that the yearly average wnd velocty was 5.7 meters per second wth a standard devaton value of 2.2 meters per second. The analyss assumed that wnd blew n the S.W. to N.E. drecton. Two parameters for the local wnd, the shape parameter (k) and scale parameter (c) were obtaned at and 6.38 meters per second, respectvely. The estmated power that could be generated by a ertcal Axs Wnd Turbne was 83.9 W/m 2 at 3 meters above ground level. Ths partcular ste corresponds to class wnd power. Ths level of power densty may be adequate for non-connected electrcal and mechancal applcatons, such as battery chargng and water pumpng. Keywords: Wnd characterstc; ertcal Axs Wnd Turbne (AWT); Wnd data n Chang Ma Introducton The demand for energy s ncreasng steadly n Thaland. Accordng to the Energy Polcy and Plannng Offce, Mnstry of Energy, and the Royal Tha Government, the energy consumpton of Thaland as of 26 was,54 Toe/day. In 26, Thaland spent 99 thousand mllon baht for the mport of energy n the forms of ol, natural gas, coal and electrcty. The rato of energy consumpton n 26 s shown n Fg.. The Royal Tha Government has created a naton-wde campagn to save energy and encourage use of all types of energes: e.g. bomass, bogas, solar, small hydro power plant and wnd. Wnd s an exstng source of energy whch s clean, renewable and abundant. In prncple, wnd s freely accessble to be utlzed. Forces exerted by wnd are readly apparent, and thus, efforts to harness wnd energy appeared very early n the hstory of manknd. Recent ncreases n the cost of fossl fuels has revved the nterest n modern explotaton of ths form of energy,.e. wnd power. Wnd power s proportonal to the cube of the wnd speed. Therefore, the knowledge of the wnd and ts characterstcs Ths paper was recommended for publcaton n revsed form by Assocate Edtor Dae Hee Lee * Correspondng author. Tel.: , Fax: E-mal address: tanatecha@hotmal.com KSME & Sprnger 2 are mportant requrements n order for the wnd turbne to be desgned accurately for hgher effcency. The analyss of wnd s energy potental requres proper statstcal assessment of wnd characterstcs such as mean wnd speed, drecton of wnd and ts frequency dstrbuton. The wnd speed gradent can help predct the potental wnd energy at hgher elevatons wth respect to the ground. However, t requres wnd data from at least two elevators of the same ste so that the power law exponent can be calculated. ertcal varatons n wnd veloctes depend on the season, tme of the day and topographcal features of the regon. To fnd the most effcent locaton to set up a wnd turbne of any partcular sze, long-term accumulaton of wnd data s requred. A ertcal Axs Wnd Turbne (AWT) s sutable for a locaton wth an undentfed wnd drecton due to the fact that a AWT accepts wnd from any drecton. The turbne may be bult at locatons where hgh structures are prohbted, such as a cty or locatons near an arport. Chang Ma provnce s located n the north of Thaland and conssts of flatlands and mountans. Ths rollng topography causes hgh local wnd shear. There are two types of seasonal or monsoon wnd [2]: the northeast and the southwest monsoon wnds, actve durng ember-ruary and ust, respectvely. So, the objectves of ths work are to study the wnd characterstcs and quantfy the wnd energy potental at Chang Ma Provnce, Thaland, and estmate the power potental that may be

2 476 T. Chachana and S. Chatep / Journal of Mechancal Scence and Technology 24 (7) (2) 475~479 Ol 44% Coal 6% NG. 37% Elec. 3% Fg.. Thaland s energy consumpton n 26 []. Mean Wnd Speed (m/s) N Sutep-Pu Natonal Park Northeast monsoon Arport Chang Ma.. A (m/s) SD (m/s) Southwest monsoon Fg. 3. Dstrbutonal parameters on a ly bass, calculated from the measured daly tme-seres maxmum wnd speed data of Chang Ma Internatonal Arport at Fg. 2. Chang Ma Internatonal Arport and topography around the arport [4]. generated by a ertcal Axs Wnd Turbne (AWT). 2. Wnd data and lmtaton n ths study Ths analyss used the wnd data collected by the weather staton at Chang Ma Internatonal Arport from 2 to 26. The staton s located at 8 o N and 98 o 57 5 E. The wnd speed data were measured n klometers per hourwas measured at a heght of 2.5 meters above ground level, whle the wnd drecton was measured at 4. meters above ground level. The data were converted to meters per second and values were converted to a standard measurng heght of. meters above ground level. Webull dstrbutons were consequently analyzed. Wnd power potental was calculated at.-3. meters above the ground level. Fnally, the power output of a ertcal Axs Wnd Turbne (AWT) at 3. meters was estmated based on the turbne effcency at 4% wth transmsson and generator effcency at 85%. 3. Wnd data analyss 3. Wnd speed The ly mean wnd speed ( ) and the standard devatons (SD) were calculated by Eqs. () and (2), respectvely. NB N = = m f () σ (2) N B 2 2 = m f N( ) N = The method of bns [5] was used to prove the average wnd speed and standard devaton, as shown n Eqs. () and (2). Fg. 4. Wnd frequency rose for 2-26 at Chang Ma Internatonal The data must be separated nto the wnd speed ntervals, or bns, n whch t occurs. It s most convenent to use the sameszed bns. Suppose that the data are separated nto N B bns. Each bn has the wdth w, wth mdpont m, wth the number of occurrences n each bns of frequency f. Fg. 3 shows that the hgh wnd speeds occurred n the summer s, l to ust, and dmnshed n the rany season from tember to ember. However, n the cold season, uary to ch, mean wnd speed slghtly ncreased. The annual average wnd speed was 5.7 m/s wth a standard devaton of 2.2 m/s. 3.2 Wnd drecton Wnd drecton s shown by the wnd frequency rose (Fg. 4). Increasng wnd frequency was used as an ndcator of a man drecton. The arport s qute an napproprate locaton to setup the wnd turbne because ths ste has a hgh value of surface roughness, and the turbne wll be dangerous to arplanes. However, ths data shows the general trend of the val-

3 T. Chachana and S. Chatep / Journal of Mechancal Scence and Technology 24 (7) (2) 475~ ues and drectons of the wnd. The data from the present locaton ndcates that the expected potental wnd power should be greater for a ste where the surface condton s characterzed by a flat open area wth low surface roughness. Most of the wnd blows n the South-West to North-East drecton or 8-27 o when o s North. The frequency of wnd n the 8-27 o drecton was 57%. Comparson of Fgs. 2 and 4 reveals that the wnd s blowng parallel to the mountan range of Sutep-Pu Natonal Park. 4. ertcal wnd speed gradent The wnd speed at the surface s zero due to the shear frcton between the ar and the surface of the ground. The wnd speed ncreases wth heght most rapdly near the ground, but at a progressvely dmnshed rate at greater heghts. At a heght of about 2 klometers above the ground, the changes n the wnd speed become zero. The vertcal varaton of wnd speed, or the wnd speed profle, can be expressed by dfferent functons. In ths study, the power exponental functon (Eq. 3) was used to analyze the vertcal varaton of wnd speed at a standard heght ( meters above ground level) and to estmate the wnd speed at 2-3 meters above ground level [5]. Z Zr z = z r α Where Z, the actual wnd speed, s recorded at heght z, Z r s the wnd speed at the requred or extrapolated heght z r and α s the power law exponent. The power law exponent can be determned as a functon of speed and heght wth followng equaton [6],.37.88ln( ref ) α = zref.88ln( ) where the unt of ref s n meters per second and z ref s n meters. The data n Table shows that the predcted wnd speed wll ncrease wth elevaton above ground level. Wnd speed at meters above the ground was predcted to be about 3% greater than wnd speed at 2.5 meters, and wnd speed at 4 meters above the ground was predcted to be 7% greater than wnd speed at 2.5 meters. The results show that the wnd turbne can capture more energy from wnd at hgher elevatons above ground. (3) (4) Table. The power law exponent and wnd speed at meters above ground level from 2-26 at Chang Ma Internatonal Month A 5. Statstcal analyss of wnd data Statstcal analyss can be used to determne the wnd energy potental of any ste. The wnd speed probablty dstrbutons and the functons representng them mathematcally are the man way to analyze data. Ther use ncludes a wde range of applcatons, from the technques used to dentfy the parameters of the dstrbuton functons [7] to the use of such functons for analyzng the wnd speed data and wnd energy economcs [8]. In general, there are two popular probablty dstrbutons to use for wnd data analyss,.e. Raylegh and Webull. The Webull dstrbuton s based on two parameters:the shape parameter ( k ) and scale parameter ( c ). The probablty densty, p ( ) and the cumulatve dstrbuton functons, F ( ) of the Webull dstrbuton are gven by Eq. 5 and 6 respectvely. Webull probablty densty functons, p ( ) k k k p ( ) = exp c c c Webull cumulatve dstrbuton functons, F ( ) k F ( ) = exp c It s not a straghtforward process to fnd the shape parameter ( k ) and scale parameter ( c ) n terms of and σ. There are several methods that can be used. Eqs. 7 and 8 are emprcal equatons [6]. They are commonly used to calculate the shape and scale parameters. σ k = Power law exponent.86 (5) (6) k < (7) c = (8) Γ ( + / k) where Γ ( x) s gamma functon α t x x e t dt Wnd speed (m/s) at elevaton above ground level (α) 2.5 m m 2 m 3 m Γ ( ) =. (9) The gamma functon can be approxmated by [9]

4 478 T. Chachana and S. Chatep / Journal of Mechancal Scence and Technology 24 (7) (2) 475~479 Table 2. Webull parameter and gamma functon of (+(/k)) at Chang Ma Internatonal Month * SD c k (m/s) (m/s) (m/s) A * Mean wnd speed at 2.5 m above ground level Probablty Densty Γ ( + (/ k)) x x 39 Γ ( x) = ( 2πx)( x )( e ) x 288x 584x 2 3 () The Webull parameter and gamma functon of (+(/k)) at Chang Ma Internatonal Arport was analyzed by usng the wnd speed at 2.5 meters above ground level and s lsted n Table 2. The Webull probablty densty dstrbutons and Webull cumulatve dstrbuton are shown n Fgs. 5 and 6,.5 Wnd Speed (m/s) Fg. 5. Webull probablty densty dstrbutons at Chang Ma Internatonal Cumulatve Dstrbuton (%) Wnd Speed (m/s) Fg. 6. Webull cumulatve dstrbuton at Chang Ma Internatonal power densty (W/m-sq) respectvely. The shape parameter (k) vared between and 3.68 and the scale parameter (c) vared between and The gamma functon of (+(/k)) vared between.886 and.93 and s n drect varaton wth shape parameter (k). 6. Wnd turbne power producton The average wnd power densty, P/ A, represents average avalable wnd power per unt area. Ths s gven by: P 3 = ( ) ρ () A 2 whereas the mean power densty for the Webull functon ( P W ) s gven by: PW ρ 2 k 3 = c Γ + Tme seres Webull model Fg. 7. Wnd power denstes obtaned from the measured data and Webull models. Power (W/m-sq) Fg. 8. Potental power generaton by AWT at 3 meters above ground level. (2) The power denstes calculated from the measured probablty densty dstrbutons and those obtaned from the Webull models are shown n Fg. 7. The mnmum power denstes occur n uary wth 4.8 W/m 2. It s nterestng to note that the hghest power densty values occur n the summer s of l,, e, y and ust, wth a maxmum value

5 T. Chachana and S. Chatep / Journal of Mechancal Scence and Technology 24 (7) (2) 475~ of W/m 2 n. The power denstes n the remanng s fall between these mnmum and maxmum groups. Fg. 8 shows the potental power densty generated by AWT at 3m above ground level. The specfc values used to calculate ths s composed of 4% of performance effcency, C p, 85% of effcences of the drve tran, η m, and the generator, η e. The power generated s calculated by Eq. 3. The hghest power values occur n the summer s wth a maxmum value of W/m 2 n. P C 2 3 AWT = ρ pηmηe (3) 7. Conclusons In the present study, daly measured tme-seres maxmum wnd speed data from 2-26 at Chang Ma have been statstcally analyzed. The probablty densty dstrbutons have been derved from the tme-seres data and the dstrbutonal parameters were dentfed. Probablty densty functons have been ftted to the measured probablty dstrbutons on a ly bass. The wnd energy potental of the locaton has been studed based on the Webull models. The most mportant outcomes of the study can be summarzed as followed: () The yearly average wnd speed and standard devaton values were 5.7 and 2.2 m/s, respectvely. The wnd prmarly blew from the southwest drecton. (2) The average shape parameter (k) was and the average scale parameter (c) was 6.38 (3) The yearly average wnd power densty value was W/m 2 at 2.5 m above ground level. The estmated power potental generated by AWT was 83.9 W/m 2 at 3m above ground level; ths partcular ste corresponds to the wnd power class of. Ths level of power densty may be adequate for non-connected electrcal and mechancal applcatons, such as battery chargng and water pumpng. Acknowledgment The authors wsh to thank the offce of Chang Ma Internatonal Thanks also to PARA laboratory, FAME laboratory and the faculty of engneerng at Chang Ma Unversty for ther support. References [] Energy Polcy and Plannng Offce, Mnstry of Energy, Royal Tha Government. Energy polcy journal ol. 75, uary ch 27, ISSN [2] Rangsan Apakupakul. Introducton to Meteorology. Chulalongkorn Unversty Press. ISBN , Thaland. (24) (In Tha). [3] John F. Walker and Ncholas Jenkns, Wnd Energy Technology. John Wley & Sons. Baffns Lane, Chc Hester, West Sussex PO9 UD, England (997). [4] Google Earth Program, Pcture of Chang Ma Internatonal Arport and topography around the arport, 27/4/27. [5] J. F. Manwell, J. G. McGowan and A. L. Rogers, Wnd Energy Explaned. John Wley & Sons, Baffns Lane, Chc Hester, West Sussex PO9 UD, England (22). [6] C. G. Justus, Wnds and Wnd System Performance, Frankln Insttute Press, Phladelpna, PA. (978). [7] J.. Seguro and T. W. Lambert, Modern estmaton of the parameters of the Webull probablty densty dstrbuton for wnd energy analyss. Journal of Wnd Engneerng and Industral Aerodynamcs, 85 (2) [8] Al Nac Celk, A statstcal analyss of wnd power densty based on the Webull and Raylegh models at the southern regon of Turkey, Renewable Energy, 29 (23) [9] M, Jaml, Wnd Power statstc and Evaluaton of Wnd Energy Densty, Wnd Engneerng, 8 (5) (994) Tanate Chachana receved hs B.S. degree n Scence (Physcs) from Prnce of Songkla Unversty, Thaland n 22 and M.S. degrees n Energy Engneerng from Chang Ma Unversty, Thaland n 24. He s currently (2) a Ph.D degrees student n Program of Energy Engneerng, Chang Ma Unversty (Tha Royal government scholarshp). Hs research nterests nclude the wnd energy, bomass energy and alternatve energy technology. Sumpun Chatep receved hs Ph.D. degree n Resources Engneerng from Unversty of New England, Armdale, Australa n 983. He s currently an Assocate Professor at the Department of Mechancal Engneerng, Faculty of Engneerng, Chang Ma Unversty, Thaland. Hs research nterests nclude flud engneerng, gas turbne and the renewable energy technology.