Low cost fabrication of permanent magnet for low speed wind turbine generators using waste motors

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1 Songklanakain J. Sci. Technol. 40 (6), , Nov. Dec Oiginal Aticle Low cost abication o pemanent magnet o low speed wind tubine geneatos using waste motos Chainuson Kasagepongsan 1* and Monti Suklueng 2 1 Renewable Enegy and Envionmental Reseach o Local Community Unit, Suat Thani Rajabhat Univesity, Mueang, Suat Thani, Thailand 2 PSU Enegy Systems Reseach Institute, Pince o Songkla Univesity, Hat Yai, Songkhla, Thailand Received: 4 Apil 2017; Revised: 4 August 2017; Accepted: 15 August 2017 Abstact This study is devoted to the euse o waste motos modiied to seve as wind tubine geneatos. The geneato is designed to be a high peomance pemanent magnet synchonous wind geneato ( PSWGs). The 10kW waste moto was modiied to a 6kW geneato by changing the oto to a neodymium magnet with 12 poles and eoming the SWG#18 coppe coils at the stato. The esults indicated high induced voltage and low hamonic distotion, as well as high geneato eiciency. The output powe o this geneato is 4kW at a wind speed o 12 m/s. S809 aeooil blades wee used o this system and the design incopoated an electical post used o the towe. Theeoe, as a waste moto and electical post ae used, the device can be abicated at a low cost to poduce a wind tubines o low speed winds suitable o southen Thailand. Keywods: PSWGs, wind tubine, waste moto 1. Intoduction Duing the past two decades, it has become wellknown that constuction and demolition (C&D) waste has exteme negative eects on the envionment and has attacted woldwide attention om both eseaches and industy pactitiones. Thailand is the one o many counties geneating C&D waste in inceasing amounts (Gui, Hongping, & Hongxia, 2010). The solid waste om agicultue and municipalities has been chaacteized as one o the astest gowing waste categoies. A typical household could expect to discad appoximately 68 items ove twenty yeas including: 20 cell phones, 10 computes, 7 televisions, 7 VCRs o DVD playes, and seveal answeing machines ( Gui, Hongping, & *Coesponding autho addess: chainuson.kas@su.ac.th Hongxia, 2010). One o the geatest solid waste types is machiney, which can be eused o modiied to ceate new units with high eiciency. Households play a cucial ole in the management o waste electical and electonic equipment (WEEE) and the success o WEEE ecycling pogams depends on thei paticipation. Getting WEEE to designated dop-o locations is a household s statutoy duty in counties such as Gemany, Japan, Switzeland, and South Koea (Manomaivibool & Vassanadumongdee, 2012). The poposed policy in Thailand calls o local govenment to buy back and consolidate WEEE o envionmentally sound ecycling. This policy has the potential to get household WEEE consolidated into the omal ecycling secto. Additional eseach is needed on the collection o WEEE in developing counties to lean how to lessen pollution and othe envionmental impacts caused by ecycling (Manomaivibool & Vassanadumongdee, 2012). Nowadays, the enegy issue has become impotant o all counties in the wold, so eduction o the consumption o taditional enegy and suppot o the development o

2 C. Kasagepongsan & M. Suklueng / Songklanakain J. Sci. Technol. 40 (6), , enewable enegy ae the keys to sustainable development ( Ying & Hongyan, 2012). In ecent decades thee has been exteme gowth in the wold population while the consumption o enegy esouces has also been inceasing. Howeve, the taditional enegy oms such as oil, coal, hydocabons, etc. geneate an enomous amount o geenhouse gases and cause envionmental pollution and ecological deteioation o the envionment. Theeoe, many eseaches have tied to develop wind powe, and the beneits o wind powe ae inteesting ( Ying & Hongyan, 2012). In Thailand the best wind enegy potential is aound the coast o the Gul o Thailand in land aeas with highe elevations.the aveage annual wind speed is 6.4 m/s measued at an elevation o 50 m. The electicity geneated om wind powe in Thailand has been inceasing in quantity continuously in both govenment and pivate sectos (Chingulpitak & Wongwises, 2014). Based on wind enegy eseach in Thailand, the povincial electicity authoity (PEA) is demonstating electicity geneation with one 1.5 MW tubine at Sating Pha Distict in Songkhla povince o southen Thailand. The wind tubine used is made in China, namely model YFKF01-500/4, and has the highest poductivity in Thailand. This tubine has a hoizontal axis diven with an asynchonous geneato gea box, with a pole height o 80 m and blade diamete o 77 m. The tubine stats up geneating electicity at a wind speed o 3 m/s and maximum poductivity is at a wind speed o 11.5 m/s. The tubine can be cut-o at a maximum wind speed o 21 m/ s ( Chingulpitak & Wongwises, 2014). Howeve, this tubine is eally opeated only with winds exceeding 3 m/s and the maintenance is not easy needing a team o technicians. Theeoe, Thailand needs to develop low speed wind tubine geneatos o local application. The pemanent magnet synchonous geneato (PMSG) based on the wind tubine can be easily connected to the gid via back-to-back convetes. The PMSG has shown high eiciency in powe enhancement and excellent peomance to extact maximum powe om the wind (Nasii, Milimonaed, & Fathi, 2014). Low speed wind geneatos have a poblem with cogging toque that could be impoved via pole and slot. The small scale wind powe applications need a cost eective and mechanically simple geneato o seving as a eliable enegy souce ( Gyeong & Tae, 2013). Geneally, the geneato and accessoies o wind tubines puchased om the maket tend to be costly. In this study, a waste moto is modiied to seve as a geneato by installing a pemanent magnet in pat o the oto and einstalling the coil in the stato. The new low cost geneato is connected with the blades om a wind tubine set that geneates maximally 6 kw electic powe. A concete electicity pole is used o the towe suppoting the wind tubine assembly. 2. Pemanent Magnet Synchonous Geneato A pemanent magnet synchonous geneato is appopiate o wind tubines. Recently, pemanent magnets have been widely used in wind tubines because these geneatos match peectly with the equiements o building a low speed wind tubine (Kallaste, Vaimann, & Pabut, 2012), with the attibutes including simple constuction, light weight, slow speed, high powe, vaiable speed, low toque, and low pice. The main poblem o this geneato is that the cogging toque must be eliminated by skewing the slot o the stato ( Abbaszadeh, RezaeeAlam, & Teshnehlab, 2012). Figue 1 exhibits the geneal stuctue o the oto aanged with the magnetic suace. The N-pole and S-pole have a complete lux cicuit; the magnetic lux passes om the oto though to the ai-gap, laminate steel, coil in the stato, ai-gap, and then passes back to the oto again to complete a closed loop (Hsiao, Yeh, & Hwang, 2014). F (1) F (2) Based on the magnetic equivalent cicuit, the lux density ( ) o the magnet passes though ai and stato in the geneato. The dive oce in the magnetic cicuit o the electomagnet is the magnetomotive oce F= Ni, that poduces a lux against magnetic eluctance R. Theeoe, the lux density is elated to the atio o F and R as shown in equation (1). This implies equation ( 2 ) o the magnetomotive oce F, in tems o lux density and eluctance R. Equation ( 2 ) is substituted into equation ( 1 ) oming the omula o lux density as equation ( 3 ) showing the atio between and R. Theeoe, equation (3) can explain that lux density depends on the initial lux density though each mateial which esults in a dieent value o R ( Sen, 1989). 2 2 m m K m g s m (4) m g Ai gap Stato Coil Roto R s Rg N Rm S R g 1 K Coil m S Pemanent-Magnet N Figue 1. Schematic diagam o the pemanent magnet synchonous geneato (PMSG) shows the magnetic lux between oto and stato (Hsiao, Yeh, & Hwang, 2014). (3)

3 1348 C. Kasagepongsan & M. Suklueng / Songklanakain J. Sci. Technol. 40 (6), , 2018 Whee eluctance and K is oto lux, m is magnet eluctance, g is ai eluctance, s is stato eluctance, is oto is the oto leakage acto. The magnetic lux can be deived as shown ( Hsiao, Yeh, & Hwang, 2014) in equation (4). Based on Figue 1, the steel eluctance ( s ) is small elative to ai-gap eluctance g ; the steel eluctance can be eliminated by intoducing a coection coeicient K slightly geate than unity to multiply g to account o the neglected ( ). Fo a machine with suace magnets unde consideation, the leakage and eluctance actos ae typically in the anges s and , espectively, while the lux concentation acto is ideally 1.0 (Hsiao, Yeh, & Hwang, 2014). E 4.44 NK (5) Hee tuns in each phase and w E is excitation voltage, is equency, is the lux pe pole to the excitation cuent I, N is the numbe o K is the winding acto. Figue 2 (a) shows the ield cuent i it lows to the oto ield winding that w induces a sinusoidal distibuted lux in the gap. I the oto is otated by the pime move that geneated the excitation voltage E it obeys equation (5), while the oto pemanent magnet can diectly give the lux density that geneated the excitation voltage E. This is shown in equation (6), and the excitation voltage E is elated though equations (4) and (5). The excitation voltage E is popotional to the geneato speed n and oto lux. The and the numbe o poles p ae constant o a pemanent magnet. Theeoe, E is only popotional to the geneato speed n shown in equation (7). E np (6) 4.44 NK 4.44 NK w w 120 g 1 K 1 K m g m E n (7) Figue 2. (a) The ield cuent I lows though the oto ield winding to induce the lux density Ø, (b) The oto lux density Ø geneated diectly om the magnet. 3. Methodology 3.1 Electical geneato The 10kW waste motos ae vey commonly available in antique electical stoes and consume thee-phase 380Vac electic powe. The moto is a bi-diectional machine. Theeoe, it can tansom wind enegy into mechanical enegy ate adapting cetain pats. In ode to obtain electical enegy, it would be necessay to abicate changes in the moto to obtain a geneato. The design o this moto is vey simple. A modiied stato is needed to educe the cogging toque that aects the stating toque. Theeoe, the slot on the stato equies a design o pope thickness o the stato tooth tips. I these stato tooth tips ae too thin, then they ae likely to be subject to magnetic satuation, inceasing the cogging toque. The thickness o the tooth tips should be the same as the width o the slot opening. Moeove, the width o the slot opening aects the cogging toque. Reducing the width o the slot opening to educe pemeance vaiation between the teeth o the stato could decease the cogging toque (Sisiiwanna & Konghiun, 2012). Epoxy/mica should be inseted into the slot in the stato to suppot the coppe coil as insulation i the geneato stato deteioates unde themal, electical, vibational, and themal-mechanical stesses when opeating ( Chen, Cheng, Yue, & Xie, 2006). The moto has 36 slots in the stato o inseting coppe coil o phase A, phase B, and phase C, as shown in Figue 3. The coils used SWG#18 with 40 tuns pe

4 C. Kasagepongsan & M. Suklueng / Songklanakain J. Sci. Technol. 40 (6), , Table 1. Paametes o the wind geneato designed. No. Paamete Value Figue 3. The oto and stato o the tansomed 36-slot moto. slot and wee coated with vanish ( Bell & Sung, 1997) to pevent shot cicuiting. Figue 3 shows the stuctue o the oto and the stato. An ai gap o 2.5 mm was omed between oto and stato o constant eluctance to lux lowing om the oto to the stato. Futhe, the magnetic ields embedded in the oto slots wee uniomly spaced ove a oto magnet pole; the magnet had a cuved shape included in the cicula suace o the oto which could smoothly move magnetic lux to the stato. The smoothness o the ai gap helps the electomotive oce waveom with low hamonic distotion. Wate insulation was impoved at the tubine to weathe poo the device. The ball beaings wee eplaced with wate pump beaings, and ubbe stips wee placed to seal possible wate entances while the coating was einoced with paint. The oiginal oto om the waste moto contained the coppe coil and laminate, the shat was inseted in the cente o the oto, and the end o shat could be connected to an assembly o blades. The commecial type neodymium magnets ( [ oute] x40x10mm) and ( [ inne] x40x10mm) with ac shape wee ixed on the suace o the oto. Thee wee 48 small suace-ixed magnets in the oto o 12 poles attached by Loctite glue 331, which gave the magnetic lux T/ magnet path equivalent to the one ceated by the coil when woking as a moto. Table 1 shows the paametes o the pemanent magnet synchonous geneato ate it was modiied om the 10 kw waste moto. 3.2 Blade stuctue design The blade used in this eseach was a 3 mete blade adapted om a design study ( Banes, Moozov, & Shanka, 2015). The blade was poduced om ibeglass and epoxy esin laminates, with shaply deceasing atigue esistance with ibe content. Excellent atigue esistance is shown with aligned stand einocement at 46-68% ibe by volume and seveal esins ( Mandell, Sambosky, & Mille, 2013). The geomety o the blade is designed to ollow (Banes, Moozov, & Shanka, 2015), which blends a cicula coss section at the blade oot to a thick S809 aeooil at the 25% span. The chod tapes and thickens om a maximum 25% o the blade span to a minimum at the tip. The aeodynamic 1. Electical geneato Pemanent Magnet Synchonous Geneato 2. Numbe o Coppe coil 18#SWG 3. Phase numbe 3 phase 4. Pole numbe 12 poles 5. Tun numbe pe coil 480 tuns/phase 6. Synchonous Speed 500 pm 7. Eiciency 72.61% 8. Resistance pe phase (A) 2.00 Ω/phase 9. Resistance pe phase (B) 2.05 Ω /phase 10. Resistance pe phase (C) 2.00 Ω /phase 11. Inductance pe phase (A) 14.5 mh/phase 12. Inductance pe phase (B) 14.5 mh/phase 13. Inductance pe phase (C) 14.5 mh/phase 14. Insulatos pe phase A-Neutal >35 G Ω /phase 15. Insulatos pe phase B-Neutal >35 G Ω /phase 16. Insulatos pe phase C-Neutal >35 G Ω /phase speciications ae designed so that the twist o the blade vaies, deceasing om oot to tip. Stuctual spa contained in the blade by webs located at the 10% and 60% chods at the blade oot and the 15% and 45% chods om the 25% span outwads. The details o thickness, twist, and chods ae shown in Table 2. The location and shape o the six aeooils, each with dieent chods and twist, ae shown in Figue 4. The blade was omed by esin ibe using vacuum assisted esin inusion moulding ( VARIM). VARIM is a composite manuactuing pocessing to abicate high quality and lage scale components. In this pocess, dy pe-om abics ae placed in an open mould and a plastic vacuum bag is placed on the top o the mould. One side o the mould is connected with a esin souce and a vacuum pump. The liquid esin inuses into the einocing ibes thanks to the vacuum dawn though the mould. Cuing and de-moulding steps ollow the impegnation pocess to complete the poduct (Goen & Atas, 2008). The main steps o the pocess ae: 1. A dy abic o pe-om and accompanying mateials such as elease ilms, peel plies ae laid on the tool suace. 2. The pe-om is sealed with a vacuum bag and the ai is evacuated by the vacuum pump. 3. Liquid esin with hadene om extenal esevoi is dawn into the component by vacuum. 4. The liquid esin with hadene is inused into the pe-om until thee is complete impegnation. 5. Cuing and de-moulding steps inish the poduct. The components o the inusion pocess utilized in the wok ae shown in Figue 5. Thee blades ae omed o a wind tubine in this study. 3.3 Peomance test o geneato The poposed pemanent magnet synchonous geneato (PMSG) was expeimentally tested, with the opeation shown in Figue 6( a) and the linea gaph exhibits the electical powe vesus otational speed o the geneato in Figue 6( b). 6kW o lamps wee used as the load while continuously inceasing the otational speed to the maximum

5 1350 C. Kasagepongsan & M. Suklueng / Songklanakain J. Sci. Technol. 40 (6), , 2018 Table 2. Span Baseline blade geomety design o the blade o the NACA S809 aeooil Chod (mm) Thickness (%) Twist (Deg) Aeooil Spa location o Cicle 10-60% o S % o S % o S % o S % o S % o ange. The PMSG was opeated at pm with the sinusoidal waveom o thee phases having peak to peak voltage aound 220 Vac at 50Hz, as shown in Figue 7( b-d), while the sinusoidal waveoms compaed with the entie 3 phase system as shown in Figue 7( a) as expected o a pemanent magnet synchonous geneato. The coesponding hamonic specta o oto and stato voltages ae shown in Figue 8( a-c). The PMSG is a thee-phase geneato that had total hamonic distotion (THD) o 1.4%, 1.6% and 1.9%, espectively.accoding to IEEE , the hamonic voltage distotion on powe systems o 69kW and below is limited to 5.0% and THD has individual hamonic limits o 3% ( Blooming & Canovale, 2006). The esultant and the component luxes otate in the ai-gap at the same speed, govened by equations (6) and (7). The phase vecto diagam o these luxes is shown in Figue 8(d).The oto lux induced the voltage E and poduced the vecto sum o the luxes om the magnets, which have almost the same magnitudes but ae phase-shited by 120 degees. Figue 4. The baseline geomety. Figue 5. (a) The vacuum assisted esin inusion molding (VARIM) pocess and (b) the inal poduct om the VARIM pocess. Figue 7. The PMSG is opeated at the speed 500 pm with sinusoidal waveom o thee-phase cuent having peak to peak voltage aound 220 V ac at 50 Hz. Figue 6. ( a) The poposed pemanent magnet synchonous geneato ( PMSG) is expeimentally tested o the opeating speed ange. (b) The electic powe om the geneato was tested using lamps at the load o up to 6 kw. Figue 8. The hamonic specta o oto and stato voltages ae shown in (a-c) while the electical phase vecto is shown in (d).3.4 Application

6 C. Kasagepongsan & M. Suklueng / Songklanakain J. Sci. Technol. 40 (6), , This wind tubine was a novel design in that by using an electic post ( einoced concete) o the towe it was low cost and made o eadily available mateials. The wind tubine was abicated by casting with box holes, so the electical post can be inseted in the hole o the tubine as shown in Figue 9 (a-c).wind enegy is one altenative enegy souce in Thailand that is located nea the equato and has low to modeate wind speeds that aveage 3-5 m/s (Glassbook et al., 2014). Suat Thani is located in southen Thailand and has high potential o wind enegy. The popeties o this PMSG geneato acilitate pactical implementation o such wind powe. Figue 10 shows the measued powe cuve o the PMSG geneato opeated with wind speed at 1. 2 m/ s, designed o wind speed o 12 m/ s, and with cut-o wind speed at 14 m/ s. The wind powe output is limited to 4kW, which is the aveage om the data logge. Howeve, electicity can still be geneated at a wind speed o 2 m/s. The electic powe was measued daily by the data logge and showed powe peaks o 1. 3 kw aound 2-4 pm, depending on the wind speed each day, as shown in Figue 11(a). The electic powe was collected monthly in ( aveage each day) ; the powe was highest aound 33kW in Febuay, and 10kW in Novembe. Additionally, the aveage powe ove the yea was appoximately 24 kw. The PMSG should be co-opeated with blades because the wind speed is low. The tubine can stat at wind speed o 1.2 m/s, is optimal o 12 m/s, and has cut-o wind speed o 14m/s. The details o the wind tubine popeties ae exhibited in Table 3. Figue 11. (a) Measued daily electic powe om the PMSG geneato, and (b) measued monthly electic powe. Table 3. Paametes o the wind tubine geneato using waste moto. No. Paamete Value Figue 9. (a) schematic sketch o the wind tubine assembly on an electic post o einoced concete. (b) The installation o the wind tubine system onto the electic post at 16 mete height. (c) The low cost wind tubine. 1. Roto Diamete (blade) 6 m. 2. Blade Mateial Fibeglass Reinoced Plastic 3. Numbe o Blades 3 4. Cut- in Wind Speed 1.2 m/s 5. Rate Wind Speed 12 m/s 6. Cut-o Wind Speed 14 m/s 7. Suvival Wind Speed 25 m/s 8. Rated Output Powe 4 kw 9. Maximum Output 6 kw Powe 10. Rated Output Voltage 380 VAC 11. Geneato Type 3 Phase Pemanent Magnet Geneato 12. Height o towe (m) 16 m (concete electical post) Figue 10. Measued powe cuve o the wind tubine using PMSG geneato.3.4 Economic analysis These wind tubine systems wee designed to opeate o 20 yeas with inancial estimates consisting o the ixed costs and the vaiable costs totaling 160,400 baht. The indicatos o inancial analysis wee based on electicity poduction o 9, kw/yea with 3% maintenance/yea, 7% salvage value and the value o 4.50 baht/unit. Economic analysis was consideed in tems o net pesent value (NPV), beneit cost atio (BCR), intenal ate o etun (IIR), and payback peiod (PBP). The esults ae shown in Table 4.

7 1352 C. Kasagepongsan & M. Suklueng / Songklanakain J. Sci. Technol. 40 (6), , 2018 Table 4. Estimates o economic easibility o this wind tubine system. Indicato 1. Net Pesent Value 224, Beneit Cost Ratio Retun on investment 20.26% 4. Payback time yeas Value Table 4 eveals a payback time o 13.8 yeas because o the aea o installation in which the median wind speed must be taken into account, but it did show positive NPV at electicity o baht/kw as shown in Figue 12. Figue 12. Estimates o payback o this wind tubine system on an annual basis. 4. Conclusions Thailand is located in a topical aea whee the wind speed is low speed but geneatos o wind tubine systems ae commonly designed o high speed and with a high capital cost. In esponse, this study evealed successul abication o a geneato o wind tubines at a low cost, o low speed, and using eadily available mateials. The geneato can be modiied om waste motos and the towe set-up om electic posts. The geneato can be opeated om wind speeds o 1.2 m/s, is designed o wind speed o 12 m/s, and has cut-o wind speed o 14 m/s. The wind powe output is limited to 4kW. In the utue, this novel geneato will help ecycle waste motos to wind tubine geneatos that can seve in small wind ams in Thailand. Acknowledgements The authos would like to thank o unding om the annual govenment statement o expenditue, Suat Thani Rajabhat Univesity, iscal yea 2013 (Exta). Renewable Enegy and Envionment Reseach o Local Community Unit (REERCU) and Monti Suklueng would like to thank the PSU Enegy Systems Reseach Institute (PERIN), Faculty o Engineeing, Pince o Songkla Univesity. Reeences Abbaszadeh, K., RezaeeAlam, F., & Teshnehlab, M. (2012). Slot opening optimization o suace mounted pemanent magnet moto o cogging toque eduction. Enegy Convesion and Management, 55, doi: /j.enconman Banes, R. H., Moozov, E. V., & Shanka, K. (2015). Impoved methodology o design o low wind speed speciic wind tubine blades. Composite Stuctues, doi: /j.compstuct Bell, S., & Sung, J. (1997). Will you moto insulation suvive a new adjustable equency dive?. IEEE Tansactions on Industy Applications, doi: / Blooming, T. M., & Canovale, D. J. (2006). Application o IEEE STD hamonic limits. Coneence Recod o 2006 Annual Pulp and Pape Industy Technical Coneence, 1-9. doi: /papcon Chen, X., Cheng, Y., Yue, B., & Xie, H. (2006). Study o epoxy/ mica insulation deteioation in geneato stato using ulta-wide band patial dischage testing technique. Jounal o polyme testing, 25, doi: /jpolymetesting Chingulpitak, S., & Wongwises, S. (2014). Citical eview o the cuent status o wind enegy in Thailand. Renewable and Sustainable Enegy Reviews, 31, doi: /j.se Glassbook, K. A. Ca, A. H. Dosnes, M. L. Oakley, T. R., Kamens, R. M., & Gheewala, S. H. (2014). Lie cycle assessment and easibility study o small wind powe in Thailand. Enegy o Sustainable Development, 22, doi: / jesd Goen, A., & Atas, C Manuactuing o polyme matix composites using vacuum assisted esin inusion molding. Achives o mateials Science and Engineeing, 34(2), Retieved om on/ _manuactuing_o_polyme_matix_c omposites_using_vacuum_assisted_esin_inusion_ molding/links/0deec53b145c605edb pd Gui, Y., Hongping, Y., & Hongxia, W. (2010). Estimating the geneation o constuction and demolition waste by using system dynamics: A poposed model. Bioinomatics and Biomedical Engineeing ( icbbe), 4 th Intenational Coneence on 2010, 1-4. doi: /ICBBE Gyeong, C. L., & Tae, U. J. (2013). Optimal cogging toque eduction design o dual stato adial lux pemanent magnet geneato. 15 th Euopean Coneence on Powe Electonics and Applications (EPE) 2013, 1-9. doi: /tenconsping Hsiao, CY., Yeh, SN., & Hwang, JC. (2014). Design o high peomance pemanent-magnet synchonous wind geneatos. Enegies. 7, doi: /en

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