NANG LUONG M(5l -
C 6 N GNGHfi M<3l LlTA CHON GOC NGHIENG TOI iTU
CHO CAC PANEL NANG Ll/ONG M.\T
T R 6 Id H.A TINH
N G U Y I N TRONG HA
To/n tdt
Bill bdo nay tdc gid xin gidi thieu den quy doc gid phuang dn lua chon goc nghieng toi tru sao cho tong ndng luang bite xa mat trai chieu den mat thu cua cdc panel Id ldn nhdt. Phucmg phdp phdn tich dua tren mo hinh gidi tich ve quan he giiia long xg chieu tdi mpt mat phdng nghieng bdt ky vai cdc tpa dp dia ly, quy dgo Mat trdi vd cudng dp long xg & tdn xg do duac tren mat bdng Igi mpi thdi diem trong ndm.
Goc nghieng toi tru fiopi ung vdi gid tri cue dgi ciia long xg tren mat phdng nghieng tim duac nhd hdm Solver Irong MsExcel. Kit qud nghien cuu cho ta cdc gid tri tuang ung ciia fiopi co dinh, theo miia vd theo timg thdng trong ndm de quy vf co the lua chon khi lap dgt vd su dung cdc panel ndng luang mat trdi (NLMT) cita minh duac hieu qud nhdt.
1. Dat van de
Ndng lugng mdt trdi la mpt trong cac ngudn ndng Iupng s^ch va vo tan, la nguon gdc cua cac nguon ndng lupmg khac tren trai dat. Loai ngudi da biet tan dung nguon ndng luong quy gia nay tir rat lau, tuy nhien vi$c khai thac va sir dyng ngudn ndng luong nay mot each hieu qua nhat thi van la van de ma chiing ta can quan tam nghien ciiu.
Ngay nay viec Idp dat va sir dung cac panel NLMT dd phat dien, ham nuac da tra nen phd bien 6 mpi viing mien cua To qudc. Cac ky thuat va cdng ngh? mdi da va dang duac ap d\ing de che tao ra cac panel cd hieu suat cao han va gia thanh ngay cang thap. Ben canh dd viec lip ddt mpt panel sao cho hieu qua cua nd
Nha may lpc dau Dung Quat dat cao nhat la mot van de kinh te-ky thuat can dupc giai dap mpt each khoa hpc.
Mdt quy tac phd bien la khi lap dat cac bp thu NLMT thi bS mat thu phai hudng ve phia chinh Nam hoac chinh Bac (gdc phucmg vi y = 0 hoac y = 180°) tuy theo vT dp dia ly hay gdc lech cua mat trdi so vdi mat phang xich dao. Khac vdi viec xac dinh hudng, viec xac dinh gdc nghieng tdi uu cho cac bp thu rat phiirc tap vi khdng nhiing do Trai dat tu quay quanh true cua nd va chuyen dpng quanh mat trdi theo qGy dao e-lip nen vi tri tuang doi cua Mat trdi so vdi Trai dat thay doi tuan hoan theo thdi gian trong ngay va trong nam ma cdn phu thupc vao cuong dp cac thanh phan biic xa mat trdi, suat phan chieu cua mat dat, tpa dp dia ly tai moi dia phuang...
Do dd viec xac dinh gdc nghieng tdi uu cho cac panel NLMT de nang cao hieu qua su dimg chting khdng chi la van de ly thuyet dan thuan ma la mpt yeu cau cap thiet tir th\rc tien.
2. Thiet lap mo hinh giai tich
Bai toan xac dinh gdc nghieng tdi iru fiopi cho cac panel NLMT trong bai viet nay duac xay dung tir cac md hinh ly thuyet va thuc nghiem duac trinh bay trong [1], [2], [3] va sd li$u khi - tuang quan trac duac trong [4].
(id KHOfl Hpc & CdNG NGHl Hft TINH ( 2 ^
Md hinh tac gia sir dung trong bai bao nay thudng dupc biet den vdi ten gpi la mo hinh bat ding hudng (thanh phan tan xa khdng ddng nhat theo mpi hudng) cua Reindl (1990), nhimg khdng phai hoan toan do Reindl xay dung nen ma la ke thira tir md hinh dang hudng kinh dien cua Liu-Jordan (1962) nhu trinh bay dudi day.
Hinh. Minh hpa quy udc cdc goc trong mo hinh tinh todn
Tdng xa Hx chieu den mpt mat phang nghieng bat ky la tdng hgp cua ba thanh phan:
true xa HB, tan xa HD va thanh phan phan xa tir mat dat HR theo cdng thirc:
Hr=H^ + H:, + H. (1)
Thanh phan true xa tinh theo md hinh cua Liu-Jordan sau khi hieu chinh lai cdng thirc cua Hottel-Woertz dua ra nam 1942 doi vdi panel d ban cau Bac, hudng ve xich dao la:
ii,-(H,-H^R, (2) co5(c - j).cor.:.5:".<.o„ + < .sin((i>~5l
C050.co5>.,. 5; ".lOi, + ^'j.-.smo.s'.nS (3)
Thanh phan tan xa tinh theo md hinh bat ddng hudng cua Reindl dugc cac tac gia trong [2] danh gia la cd dp chinh xac cao khi mat thu quay ve hudng Nam:
HD=H,R:, (4)
Cac gia tri HQ \ a Hd trong bai bao nay dupc tac gia lay theo sd lieu thdng ke d tram Vinh '"*' nhu trong bang dudi day:
Ho 2191 2140 2732 4326 6091 6176 Hd 1553 1667 2035 2677 2781 3113
Ho 6550 5751 4715 3604 2747 2441 Hd 2903 3018 2576 2138 1831 1689 Hb = W- - //- la true xa trung binh ngay ciia
thang, [W/m^/ngay]; (7) cp-gdc VI dp, d TP. Ha "TTnh lay bang -1-18° (vT
dp Bac);
6-gdc lech cua mat trdi, la gdc lech giiia dudng thang ndi tam Trai dat vdi tam Mdt trdi so vdi mat phang xich dao khi Mat trdi di qua kinh tuyen dia phuang, dan vi tinh la [dp], dugc xac -dinh theo cdng thiic Cooper (1969) la:
:.-(234 4-';)
;3.45.£;n
365 (8)
.t. +
M)(^^)'-i-(i
(5)
Thanh phan phan xa tir mat dat tinh theo md hinh dang hudng cua Liu-Jordan:
«, = «.(ii|^)
(6)
Cac dai lugng trong cac cdng thiic tren la:
Ho- tdng xa trung binh cua mpt ngay trong thang do dugc tren mat bang, [W/m^/ngay];
Hd- tan xa trung binh cua mpt ngay trong thang do dugc tren mat bang, [W/m^/ngay];
( 2 6 ) sd KHOfl Hpc SI C6NG N G H I Hft TINH^
Trong do n la ngay thii n trong ndm, quy udc n=l la ngay 1 thang 1;
^S3- ^••'ss la gdc gid mat trdi ldn img vdi mdt bang va mdt phang nghieng, d'an vi tinh la [radian], xac dinh theo cdng thtic:
{
io,j = .ArccosC-tin<J>tan6) ') Arccos[- tan(4. - p)tan6]J (9) p-suat phan chieu cua mat dat, lay bdng 0,2 11,3)P-la gdc nghieng cua panel so vdi mdt bdng vdi quy udc gdc p > 0 khi mat thu hudng \h phia chinh Nam, p < 0 khi mat thu hudng \h phia chinh Bdc. Tac gia dua vao ddu tri tuyft doi trong phuang trinh (5) chi mang tinh thuat toan de giam bdt sd lugng phep tinh.
Bai toan cd the dugc phat bieu nhu sau:
Tim cdc gid tri goc nghieng ciia mat ihu fiopi Sf-9(f,9(fJ de long ndng luang buc xg mat trai chieu den mdt thu
X^r = 5][[(«.<-l^..)Srv-; • ( ^ ) !
dgt gid tri ldn nhdt trong nhiing khodng thdi gian cho trudc trong ndm.
Vi gia tri do dugc ctia buc xa mat trdi la trung binh ngay ctia timg thang trong nam nen gdc l?ch cua mdt trdi trong cac cdng thiic tren sS dugc thay bdi gia trj trung binh thang theo cdng thiie:
£
rr, ?•- - ' = > ' ' ' •
•^- >". (10)
m-la sd ngay cua thang thur k trong ndm, k= 1,12^ 5i tinh theo cdng thiic (8) cho moi ngdy trong thang.
3. Phan tich ket qua va nhan xet
Bdng 1. Cdc gid tri goc nghieng toi tru cho bp thu phdng theo timg thdng trong ndm Thdng
1 2 3 4 5 6 7 8 9 10 11 12
Gdc nghieng
Popt (dp)
42 29 17 3 12 18 16 3
14 31.5 42 46
Hudng
Nam Nam Nam Nam Bdc Bdc Bdc Bdc Nam Nam Nam Nam Tdng NL tren m$t thu ca ndm (MJ/m^.ndm)
Tdng NL tren mdt thu (MJ/mlthang)
293,85 232,08 312,68 467,52 691,73 693,17 753,22 642,56 520,99 448,58 357,92 341,54 5755,85 Bdng 2. Cdc gid tri goc nghieng toi tru cho bp thu phdng theo cdc mita trong ndm
Thdng Gdc nghieng
Popt (dp)
Hudng Tdng NL tren mdt thu (MjW.thang)
11 12 1 2 3 4 5 6 7 8 9 10
43
12
15
12
Nam
Nam
Bdc
Nam Tdng NL tren mdt thu ea nam (MJ/mlndm)
357,83 341,33 293,82 226,69 312,14 463,14 690,87 692,52 753,21 626,34 520,74 431,18 5709,83
Bdng 3. Gid tri goc nghieng toi uu cho bp thu phdng CO dinh
Thang 1 2 3 4 5 6 7 8 9 10 11 12
Gdc nghieng Popt (dp)
6,5
Hudng
Nam
Tdng NL tren mjt thu ca ndm (MJ/m^.ndm)
Tdng NL tren mdt thu (MjW.thang)
258,26 222,25 309,79 466.80 664,25 646,21 701,04 636,00 517,49 419,28 313,93 290,17 5454,47 Vifc lya chpn phuang an Idp ddt thay ddi gdc nghieng theo thang, theo miia hay cd djnh tuy thudc vao tinh thuan lgi va mye dich cua ngudi sti dung. Tuy nhien can chii y rdng vdi cac bd thu NLMT dh ham nudc thudng la loai ttidn hoan ty nhien (khdng dung bam) dya vao hieu ling Si-phdng nhi?t trong trudng trgng lye, nen cac bp thu kieu nay yeu cau mdt gdc nghieng tdi
^ S d KHOfl Hpc Si CONG NGHl Hft TINH ( 2 ^
thieu de dam bao tuan hoan ty nhien va thudng dugc dua ra trong sd tay hudng dan sii dung cua cac nha san xuat. Do do viec lya chgn gdc nghieng tdi uu phai thda man yeu cau nay. Cdn ddi vdi cac tam pin NLMT hay he thdng nudc ndng tuan hoan cuong biic (dimg bom) thi khdng can de y tdi.
Tuy tac gia da cd gang lua chpn md hinh phii hgp nhung dp tin cay ciia ket qua thu dugc van phu thudc nhieu vao dp tin cay cua sd lieu quan trdc thdng ke dugc trong [4]. Su sai khac ve tpa dp dia ly nai quan trdc biic xa mat trdi so vdi tpa tinh toan trong md hinh ciing cd the gay ra sai sd.
Bie'n thien cua goc nghieng toi \ni (d?) theo thorl gian 12 thang trong nam
- Gia trj am la be mat thu lnrcfng ve phia bac - Gia tri di/ffng la be m^t thu hi/ong ve phia nam
— C o dinh Iheo thing —Coflinhtheomua - CotJinhtheonam
Do thi 1. Bien thien gid tri goc nghieng toi tru ciia cdc phuang dn theo 12 thdng trong ndm
4. Ket luan
100 00
•?:1 X l
9~ LW
!!6 00
•35 00 3100
•:)l M 92 00
t ^
\ •••-
^ ^__
1 ,
ftiLCddinh thecthar^
Do thi 2. Hi?u qud ndng Iupng ciia bp thu thay doi theo cdc phucmg dn lua chpn goc nghieng toi mi
Ket qua phan tich trong bai viSt nay cho thdy:
Neu thay ddi gdc nghieng cua panel theo cac gia tri tdi uu timg miia thi tdng nang lugng biic xa chieu den mat thu se giam khoang 1%, cdn neu ddt bp thu cd djnh vdi gdc nghieng tdi uu thi tdng nang lugng birc xa chidu dSn bd mat thu giam khoang 5% so vdi trudng hgp thay ddi gdc nghieng cua panel theo cac gia trj toi uu timg thang trong nam (do thj 2). Neu lya chpn gdc nghieng khdng phii hgp thi hipu qua cua cdc panel hay bd thu cd the giam di rat nhidu.
To/ lifu Iham khao
[1] Soteris A. Kalogirou: Solar energy engineering processes and systems. Copyright © 2009. Elsevier Inc.
[2] AU Mohammad Nooridn, Isaac Moradi, Gholam Ah Kamali: Evaluation of 12 models to estimate hourly diffuse irradiation on inclined surfaces. Renewable Energy 33 (2008).
[3] John A.Duffie, William A.Beckman: Solar engineering of thermal processes, John Wiley& Sons, Inc,1980.
[4] Quy chudn xdy dung Vi?t Nam, QCXDVN 02:
2008/BXD.
[5] Hodng Duang Himg: Ndng Iupng Mat trdi -ly thuyit vd img dung, NXB KHKT2007.
CAU DOI
'Teie e» ttutfitt iaf*H, au» ^Atf^ tiatUi tdtt, edtUi itiim. ttdtc eA& xuei» « « AJU dJL»^
^Cfteit tUit t&« i titUi ddt «w^ itte., 6*aiH^ tcaiu e<£» min t& ditt iiitt e*aiHf^.
( ^ s d KHOfl Hpc & CdNG NGHJ Hft TJNH^ Q u v n h N h U