pin nhien lieu mat troi

8/3/2019 Pin Nhien Lieu Mat Troi

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PHN I:PIN NNG LNG MT TRI(PNLMT)

Mc lc:

1) Gii thiu chung v lch s hnh thnh

2) Cu to v nguyn l to in nng

3) Mt s hn ch ca PNLMT

4) Thit b km theo

5) ng dng Vit Nam v t th giit vn :

i. Pin mt tri hot ng nh th no?

ii. Ti sao phi pha thm tp cht vo cht bn dn silic?

iii. iu g s xy ra khi cho hai loi bn dn P-N tip xc

nhau?iv. Ti sao PNLMT cho cng sut thp?

v. Vn t ra cho t s dng PNLMT ngy nay l g?
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PHN II:KH THIN NHIN NGVA. GII THIU CHUNG

B. KH THIN NHIN

I. ng dng kh thin nhin trn t1. Dng kh thin nhin c th cung cp v cha trong bnh

nhin liu t

2. t s dng nhin liu kh thin nhin NGV

II. Tnh cht NGV

1. Thnh phn ho hc

2. Nhit tr (PCI)

3. Ch s Wobbe

4. c im lin quan n qu trnh chy trong ng c

a. Ch s OCTANE

b. nh la v lan truyn bung la trong bungchy ng c s dng NGV

c. Thnh phn v nhit ca sn phm chy

III. Cc k thut lin quan n t s dng NGV1. Bnh cha nhin liu NGV trn t v h thng cung cp

a. Bnh cha NGV trn t

b. H thng cung cp NGV

2. T chc qu trnh chy

IV. Cn bng nng lng v nh hng n mi trng ca h

t NGV1. Tiu tn nng lng lin quan n vic vn hnh h

thng NGV

2. Tnh nng ca t

a. i vi t thng dng

b. i vi xe bus v xe vn ti

3. nh hng i vi hiu ng nh knh

C. HNG PHT TRIN TRONG TNG LAI


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PHN I: PIN NNG LNG MT TRI

1> Gii thiu chung v lch s hnh thnh

a> Gii thiu chung:

Theo thng k ca cc nh khoa hc th nhin liu hc thch th s b

cn kit trong vng 50 nm na nu c s dng nh tc nh hin nay.

Do vn tim ngun nhin liu thay th ang uc t ra hng u.

C rt nhiu kin c a ra nhng pin nng lng mt tri c s

quan tm cao, v tnh nng sch v bn vng ca n.

C 2 cch chnh s dng nng lng mt tri

- S dng di dng nhit nng : l hp th mt tri, nh knh...

- S dng thng qua s chuyn ho thnh in nng: H thng pin

mt tri

Cu hi t ra l pin mt tri hot ng th no?

Pin mt tri l thit b ng dng hiu ng quang in trong bn dn ( thnggi l hiu ng quang in trong - quang dn) to ra dng in mt chiu

t nh sng mt tri.

b> Lch s

Hiu ng quang in c pht hin u tin nm 1839 bi nh vt l

Php Alexandre Edmond Becquerel. Tuy nhin cho n 1883 mt pin nnglng mi c to thnh, bi Charles Fritts, ng ph ln mch bn dn selen

mt lp cc mng vng to nn mch ni. Thit b ch c hiu sut 1%,

Russell Ohl xem l ngi to ra pin nng lng mt tri u tin nm 1946.

Sven Ason Berglund c phng php lin quan n vic tng kh nng

cm nhn nh sng ca pin.

II>C u to v nguyn l to in nngA > Cht bn dn


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a) Cht bn dn silicon

_ Loi pin mt tri thng dng nht hin nay l loi s dng Silic tinh

th. hiu v nguyn l lm vic ca pin mt tri loi ny chng ta cn bit

mt vi c im ca cht bn dn Silic.

_ Trong bng tun hon Silic (Si) c s hiu nguyn t 14-

1s22s22p63s23p2 . Cc in t ca n c sp xp vo 3 lp v, 2 lp v bn

trong c xp y bi 10 in t. Tuy nhin lp ngoi cng ca n ch c

lp y 1 na vi 4 in t 3s23p2. iu ny lm nguyn t Si c xu hng

dng chung cc in t ca n vi cc nguyn t Si khc. Trong cu trc

mng tinh th nguyn t Si lin kt vi 4 nguyn t Si ln cn lp v ngoi

cng c chung 8 in t (bn vng).

_ Tinh th Si tinh khit l cht bn dn, dn in rt km v cc in t b

giam gi bi lin kt mng, khng c in t t do. Ch trong iu kin kch

thch quang, hay nhit lm cc in t b bt ra khi hin kt, hay ni theo

ngn ng vng nng lng l cc in t (tch in m) nhy t vng ha tr

ln vng dn b li vng ha tr 1 l trng (tch in dng), th khi cht

bn dn mi dn in.

b) Pha tp cht to bn dn P-N

V sao phi pha thm tp cht?

_ tng kh nng dn in ca bn dn silicon ngi ta thng pha tp

cht vo trong . Trc tin ta xem xt trng hp tp cht l nguyn t

phospho (P) c s hiu nguyn t 15-1s22s22p63s23p3 vi t l khong mt

phn triu. P c 5 in t lp v ngoi cng nn khi lin kt trong tinh th


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Si s d ra 1 in t. in t ny trong iu kin b kch thch nhit c th bt

khi lin kt vi ht nhn P khuch tn trong mng tinh th.

Cht bn dn Si pha tp P c gi l bn dn loi N

(Negative) v c tnh cht dn in bng cc in t t do.

_ Nu chng ta pha tp cht l cc nguyn t Boron (B) c s hiunguyn t l 5-1s22s22p1 vi silic th: B ch c 3 in t lp v, chng ta s

c cht bn dn loi P (Positive) v c tnh cht dn in ch yu bng cc

l trng.

c> C ch pht sinh in nng

iu g s xy ra khi ta cho 2 loi bn dn P-N tip xc vi

nhau?

_ Khi cho 2 loi bn dn P-N tip xc vi nhau th cc in t t do

gn mt tip xc trong bn dn loi N s s khuych tn t bn dn loi N ->

loi P lp cc l trng trong phn bn dn loi P ny.

_ Liu cc in t t do ca bn dn N c b chy ht sang bn dn P haykhng? Cu tr li l khng. V khi cc in t di chuyn nh vy n lm cho


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bn dn N mt in t v tch in dng, ngc li bn dn P tch in m.

b mt tip xc ca 2 cht bn dn by gi tch in tri ngc v xut hin

1 dng in hng t bn dn N sang P ngn cn dng in chy t bn dn P

sang N.

_ Thit b m chng ta va m t trn chnh l 1 i t bn dn. intrng to ra b mt tip xc ch cho php dng in t chy theo 1 chiu.

y l t bn dn loi P sang bn dn loi N, dng in t s khng c

php chy theo hng ngc li. l gii v sao bn c th lin h mt cch

n gin n phn tnh in.

(Khi c photon chm vo mnh silic nu nng lng ca photon cao hn

nng lng ca cc e trong mng tinh th. Th nng lng ca photon s b

cc e trong mng tinh th hp th. V a cc e ln mc nng lng cao hn.

Khi photon c hp th, nng lng ca n c truyn n cc ht electron

trong mng tinh th. Thng thng cc electron ny lp ngoi cng, v

thng c kt dnh vi cc nguyn t ln cn v th khng th di chuyn

xa. Khi electron c kch thch, tr thnh dn in, cc electron ny c th

t do di chuyn trong bn dn. Khi nguyn t s thiu 1 electron v gi

l "l trng". L trng ny to iu kin cho cc electron ca nguyn t bn

cnh di chuyn n in vo "l trng", v iu ny to ra l trng cho

nguyn t ln cn c "l trng". C tip tc nh vy "l trng" di chuyn

xuyn sut mch bn dn.)

_ Pin quang in khng phi ci g khc chnh l mt it bn dn c

din tch b mt rng v c lp N cc mng nh sng c th truyn qua.

Khi chiu nh sng vo pin quang in mt phn s b phn x ( v do trn


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b mt pin quang in c mt lp chng phn x ) v mt phn b hp th

khi truyn qua lp N. Mt phn may mn hn n c lp chuyn tip, ni

c cc cp e v l trng nm trong in trng ca b mt gii hn P-N. Vi

cc bc sng thch hp s truyn cho e mt nng lng ln bt khi

lin kt. S khng th c chuyn g nu khng c in trng nh to bi lp

chuyn tip. l l do gii thch v sao nu ta chiu nh sng vo mt vt

bn dn th khng th sinh ra dng in .

_Nhng cp e v l trng ny nm trong tc dng ca in trng do e s

b ko v pha bn dn loi N cn l trng b ko v pha bn dn loi P. Kt

qu l nu ta ni hai cc vo hai phn bn dn loi N v P s o c mthiu in th. Gi tr hiu in th ny ph thuc vo bn cht ca cht lm

bn dn v tp chp c hp ph . Vi Si ( B;P) th gi tr ny khong

0,6V.


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Cu to v nguyn l thu NLMT nh hiu ng nh knh

3> Mt s hn ch ca PNLMT

_ nh sng mt tri cung cp cho chng ta khong 1 kilowatt/m2

( Chnh xc l 1,34 KW/m2: y chnh l hng s mt tri). Tuy nhin hiu

sut chuyn thnh in nng ca cc pin mt tri ch vo khong 8% n

12%.

_ Ti sao li t vy?. Cu tr li l nh sng mt tri c ph tn s kh

rng. Khng phi tn s no cng c nng lng kch thch in t t

vng ha tr ln vng dn. Ch c nhng photon nng lng cao hn khe vng


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bn dn mi lm c iu ny. i vi bn dn Si khe vng vo khong

1.1eV. Cc photon nng lng thp hn s khng s dng c. Nu photon

c nng lng cao hn khe vng th phn nng lng d cng khng c

ng gp g thm. Vy ti sao chng ta khng chn cc vt liu c khe vng

hp tn dng ngun photon tn s thp. Vn l khe vng cng xc nh

hiu in th (hay in trng) b mt tip xc. Khe vng cng b th hiu

in th ny cng b. Nn nh cng sut ca dng in bng hiu in th

nhn vi dng. Ngi ta tnh ton c khe vng ti u l vo khong

1.4eV, khi cng sut dngin thu c ti a.

_ Mt nguyn nhn na cng cn tr vic nng cao hiu sut ca pin mt

tri, l cch chng ta b tr cc tip xc kim loi ly dng in. mt

di ca tm pin hin nhin ta c th cho tip xc vi 1 tm kim loi nhng

mt trn n cn trong sut nh sng c th i qua. Nu ch b tr cc tip

xc mp tm pin th cc in t phi di chuyn qu xa trong tinh th Si mi

vo c mch in (ch l bn dn Si dn in km, tc in tr ca n

ln). V vy ngi ta thng dng 1 li kim loi ph ln b mt ca pin mt

tri. Tuy nhin kch thc li khng th gim v hn nn cng phn no lm

gim hiu sut chuyn nng lng nh sng thnh nng lng in.

_ Th ba l: c ngi cho rng nng lng lm ra mt h thng pin mt

tri ln hn nng lng n thu c trong qu trnh dng ( hay ni mt cch

i sng hn tin mua n t hn tin mua in: iu ny trc y l ng,tuy nhin vi cng ngh hin nay t l ny l 1:4 nghing v tin thu c.

Tc l b 1 triu mua h thng th s thu c 4 triu tin nng lng thu

c )

_ Mt thc t l vic s dng nng lng Mt tri nc ta cn qu xa

vi l do ta vo ngun nng lng thy in ( cng l mt loi nng lng

sch) nhng thc t nhu cu tiu th in v s kh s v tnh trng cc h


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cha xung di mc cht ging mt hi chung nh ti suy ngh ny ca

ton b mi ngi!

S c bn ca h thng in nng lng mt tri

4> Mt s thit b km theo

a. B IU KHIN SC

- L thit b thc hin chc nng iu tit sc cho c-quy,

bo v cho c-quy chng np qu ti v x qu su nhm

nng cao tui th ca bnh c-quy, v gip h thng pin

mt tri s dng hiu qu v lu di. - B iu khin cn

cho bit tnh trng np in ca Panel mt tri vo c-quy

gip cho ngi s dng kim sot c cc ph ti. - B iu khin cn thc

hin vic bo v np qu in th (>13,8V) hoc in th thp (


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Mch bo v ca b iu khin s thc hin vic ngt mch khi b iu khin

xc nhn bnh c-quy c np y hoc in p bnh qu thp.

b. BATTERY (c-quy):

- L thit b lu tr in s dng vo ban mhoc lc tri t hoc khng cn nh nng.

- c-quy c nhiu loi, kch thc v dung lng

khc nhau, ty thuc vo cng sut v c im ca h

thng pin mt tri RED SUN. H thng c cng sut

cng ln th cn s dng c-quy c dung lng ln hoc dng nhiu bnh c-

quy kt ni li vi nhau.

c. AC-DC INVERTER

- L b bin in nghch lu. Inverter chuyn i

dng in 12V DC t c-quy thnh dng in AC

(110VAC, 220VAC). c thit k vi nhiu cp cng sut

t 0.3kVA 10kVA.

- Inverter c nhiu loi v cch phn bit chng bng dng sng ca in

p u ra : dng sng hnh sine, gi sine, sng vung, sng bc thang

5 ) ng dng PNLMT Vit Nam v t s dng PNLMT trn

th gii

_Pin mt tri l phng php sn xut in trc tip t nng lng mt

tri qua thit b bin i quang in. Pin mt tri c u im l gn nh, c

th lp bt k u c nh sng mt tri, c bit l trong lnh vc tu v tr.

ng dng PNLMT di dng ny c pht trin vi tc rt nhanh, nht

l cc nc pht trin. Ngy nay ng dng PNLMT chy xe thay th dn

ngun nng lng truyn thng.


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_ Tuy nhin gi thnh thit b pin mt tri cn kh cao. Nn nhng

nc ang pht trin, pin mt tri hin mi ch c kh nng duy nht l cung

cp nng lng in s dng cho cc vng su, vng xa, ni ng in quc

gia cha c.

_ Vit Nam, vi s h tr ca nh nc (cc b, ngnh) v mt s t

chc quc t thc hin thnh cng vic xy dng cc trm pin mt tri c

cng sut khc nhau phc v nhu cu sinh hot v vn ha ca cc a

phng vng su, vng xa, cc cng trnh nm trong khu vc khng c li

in. Tuy nhin hin nay pin mt tri vn ang cn l mn hng xa x i vi

cc nc ngho nh chng ta.

_ i u trong vic pht trin ng dng ny l ngnh bu chnh vin

thng. Cc trm pin mt tri pht in s dng lm ngun cp in cho cc

thit b thu pht sng ca cc bu in ln, trm thu pht truyn hnh thng

qua v tinh. ngnh bo m hng hi, cc trm pin mt tri pht in s

dng lm ngun cp in cho cc thit b chiu sng, ct hi ng, n bo

sng. Trong ngnh cng nghip, cc trm pin mt tri pht in s dng lm

ngun cp in d phng cho cc thit b iu khin trm bin p 500 kV,

thit b my tnh v s dng lm ngun cp in ni vi in li quc gia.

Trong sinh hot ca cc h gia nh vng su, vng xa, cc trm pin mt tri

pht in s dng thp sng, nghe i, xem v tuyn. Trong ngnh giao

thng ng b, cc trm pin mt tri pht in dn c s dng lm nguncp in cho cc ct n ng chiu sng. hiu c ht tc dng, hiu

qu v tm quan trng ca h thng pin mt tri pht in, chng ta c th tm

hiu s nguyn l h thng in pin mt tri ni li in hnh di y:


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Xe hi chy bng nng lng mt tri nhanh nht th gii

_ Mu siu x Volkswagen do Peter Wilkins thit k chnh l li phn

pho cho nh kin v kiu dng xu x ca dng xe chy bng nng lngmt tri.

_ B pin quang in tch hp t trn b cnh ngoi tht. Nhim v

ca b pin l hp th nng lng mt tri v np cho cm pin nhin liu
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hyr t gia. Bn cnh l 4 m-t in dng truyn ng cho bnh

xe.

PHN II: KH THIN NHIN NGV

A. Gii Thiu Chung:


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Kh thin nhin l ngun nng lng s cp rt quan trng. trong nhngnm gn y, sn lng kh thin nhin hng nm trn th gii t xp x 2 tTp (1000m3 = 0.85Tep), tng ng khong 60% sn lng du th. Ngita c tnh n nm 2020, sn lng kh thin nhin trn th gii s l 2.6 t

Tep/nm so vi sn lng du th l 3.5 t Tep.Tr lng kh thin nhin hin nay khong 150 t Tep,xp x vi tr lng du th. Mt khc, kh thin nhin c uim l phn b gn nh hu khp trn a cu nn m boc s cung cp an ton v thun tin hn du th.

Kh thin nhin hin nay ch yu c s dng sinhnhit gia dng v cng nghip (si, to nhit , cng nghha hc...). T l kh thin nhin s dng trong lnh vc giaothng vn ti cn rt khim tn.

T nhng nm 1990, vic nghin cu s dng kh thinnhin lm nhin liu c thc hin nhiu khu vc trnth gii. Kh thin nhin c xem l nhin liu sch. V vy,vic s dng n chy ng c ngoi mc ch a dng hangun nhin liu n cn gp phn lm gim nhim mitrng mt cch ng k.

Kh thin nhin thay nhin liu lng truyn thng chy t gi tt l NGV. Sau y chng ta s nghin cunhng c trng ca NGV, tnh nng k thut cng nh mc

pht nhim ca t s dng ngun nng lng ny.

B. Kh thin nhin NGV:

I. ng dng kh thin nhin trn t:1. Dng kh thin nhin c th cung cp v cha trong bnh nhin liut:

Kh thin nhin c th cha trong bnh nhin liu ca t hai dng:- Dng kh nhit mi trng v p sut cao (khong200bar).

- Dng lng nhit -16oc v p sut mi trng khngkh.


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Cng mt nng lng nh nhau, kh thin nhin ha lng c th tch vkhi lng bnh cha nh hn khi n dng kh (thng t l 1:3 ivi th tch v 1:3.7 i vi khi lng). Tuy nhin, vic s dng khthin nhin trng thi lng cn c k thut lm lnh phc tp, bnhcha phi c cch nhit hon ton. Khi khng cn c cch nhit ,

phi m suppap an ton (tc ng p sut 6 bar) cho kh thinnhin thot ra. Tnh trng ny gy tn tht mt b phn nhin liu (cth n 1%) khng cn thit, nhng nguy him nht l s chy n nus bay hi din ra trong mi trng khng kh kn. Do vy, hin naytrn th gii ngi ta thng dng kh thin nhin dng kh chy t. Tuy nhin, mt s nc nh M, c... ngi ta ang tip tcnghin cu s dng kh thin nhin ha lng s dng trn cc ngc cng sut ln (xe ti, tu la, tu bin...).

2. T s dng nhin liu kh thin nhin NGV:Nm 1996 ngi ta c tnh c khong 1 triu xe t chy bng khthin nhin trn th gii.

Hnh 1.S phn b lng t s dng nhin liu kh trn th gii

hnh trn gii thiu s phn b lng t dng nhin liu kh thinnhin cc lc a khc nhau. Cc quc gia s dng nhiu nht l CEI(Cng ng cc quc gia c lp), , Argentina, Canada, Newzealand,M. trong nm 1996 ngi ta c tnh c 2700 trm phn phi NGVdi dng kh nn, trong 600 trm Canada v H Lan c lp tmy nn gia dng ngay ti nh ngi s dng.Con s c tnh ny s

thay i rt nhiu trong mt tng lai gn v ngi ta d kin mt sgia tng nhanh chng c v s cc quc gia s dng cng nh s lng


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t s dng NGV tng nc. Tuy nhin, d s lng c tng nhanhnh vy, t s dng NGV cng ch c ch trn mt s dng xedch v cng cng (taxi, xe bus...) v loi nhin liu ny gip cho ngc lm vic tt hn, t n, pht sinh t nhim hn ng c s dngnhin liu lng.

II. Tnh cht ca NGV:Kh thin nhin c thnh phn ch yu l methane (CH4chim t 80-90% ty theo ngun khai thc). V vy, tnhcht ca kh thin nhin gn vi tnh cht ca khmethane.

1.Thnh phn ha hc

Methane

Ethane

Propane

Butane

C5+

Nit

H2S

CO2

Php 69.0 3.0 0.9 0.50.5

1.515.3

9.3

Algerie 83.7 6.8 2.1 0.80.4

5.8 - 0.2

ngu 85.3 5.8 5.3 2.1 0.2 0.9 - 0.4

Irak 56.9 21.2 6.0 3.71.6

- 3.5 7.1

M 86.5 8.0 1.9 0.30.2

2.6 - 0.5

Indonesia

65.7 8.5 14.5 5.10.8

1.3 - 4.1

Bng 1: Thnh phn ca kh thin nhin cc vng khai thc khc nhau

Bng trn gii thiu thnh phn tiu biu ca mt s mu khthin nhin t mt s khu vc trn th gii. Ngoi methane,nhng thnh phn hydrocacbure khc theo th t thnh phngim dn: ethane (1-8%), propane (2%), butane v pentane(nh hn 1%). Kh thin nhin cng cha nhng cht kh trnh nito (10.8%), CO2 (0.2-1.5%). Trong nhng phn sau,chng ta ch xt kh NGV l kh thin nhin cha t nht 80%methane.

2. Nhit tr (PCI):


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Thng thng, nhit tr ca kh thin nhin c tnhtheo kWh/m3 iu kin thng (101.3 kPa v OoC). Trong sdng NGV lm nhin liu cho t, tin cho vic so snhvi nhin liu c in nh xng, diesel, ngi ta thng tnhnhit tr theo MJ/kg. Bng 2 gii thiu mt vi gi tr tiu biu

PCI ca kh thin nhin t cc vng khc nhau. S chuyn it PCI th tch sang PCI khi lng cn phi bit khi lngring r(kg/m3). T l nhin liu /khng kh trong tng trnghp chy hon ton l thuyt c th c xc nh theo thnhphn ca kh thin nhin (bng 1).

Xut xkh

Khilng

ring th kh (kg/m3) r

T l hnhpchyhonton l thuyt

PCI

(MJ/kg) (kWh/kg) (MJ/m3N) (kWh/m3N)

Lacq 0.73 17.09 49.64 13.79 36.42 10.12

Algerie(fos)

0.76 16.77 48.89 13.58 37.06 10.29

Algerie

(Montoir) 0.80 16.79 48.95 13.60 39.40 10.94Mer duNord

0.81 15.63 45.46 12.63 36.80 10.22

URSS 0.74 16.53 47.99 13.33 35.70 9.92

Gronigue 0.82 13.87 40.27 11.19 33.17 9.21

Bng 2:Nhit tr khi = 1 i vi cc mu kh thin nhin

Chng ta c th thy rng kh thin nhin c nhit tr ring khi lngcao hn (khong 10%) so vi nhin liu lng thng thng. Cng hiu sutnh nhau, sut tiu hao nhin liu (tnh theo khi lng) ca ng c dng

NGV cng gim chng y ln. D nhin, PCI ca NGV gim khi thnh phncc kh tr (CO2, N2) tng.

3. Ch s Wobbe:Ch s Wobbe (W) l mt c trng c s dng lu so snh tnh

nng ta nhit ca h thng chy. Ch s Wobbe c tnh theo biu thc sau

y: cng thc


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Trong :PCS: nhit tr cao MJ/m3.d: t trng ca ga so vi khng kh.Quan h gia W v t l hn hp trong trng hp chy hon ton l

thuyt rt c ngha thc tin:

Biu thc ny cho ta thy rng r l hm ng bin theo ch s Wobbe.Nu ch s Wobbe tng, t l chy hon ton l thuyt, v do m c

ca hn hp, cng tng vi cng s iu chnh h thng cung cp nhin liukh.V vy i vi nh ch to t, gi tr ca tr s Wobbe v nht l s

thay i ca n t mu kh ny n mu kh khc l mt thng tin cn thiti vi s iu chnh h thng cung cp nhin liu cho ng c.

4. c im lin quan n qu trnh chy trong ng c:So snh mt s tnh cht c trng ca kh thin nhin (ch yu l kh

methane) v xng c trnh by trong bng 3.

c trng Methane XngCh s octane 130 95Nhit tr khi lng (kJ/kg) 50009 42690Nng lng hn hp (kJ/dm3) 3.10 3.46Gii hn di bc chy 0.50 0.60Tc chy chy tng mc 0.80 (cm/s)

30 37.5

Nng lng nh la ti thiu(mJ)

0.33 0.26

Nhit on nhit ca mng la(K)

2227 2266

Bng 3: So snh c tnh ca methane v xng

a. Ch s octane:Ch s RON v MON ca methane theo th t l 130 v 115. y l u

th ca kh NGV s dng trn ng c nh la cng bc. Do tnh chngkch n tt nn NGV cng c s dng trn ng c c t s nn cao cci to t ng c Diesel nguyn thy. Trong trng hp , ngi ta thng

s dng phng php nh la bng cch phun mi (ng c lng nhinliu). K thut ny c nhiu li th trn ng c tnh ti nhng s dng rt hnch trn ng c vn ti do vic iu chnh phc tp ch qu . V vy,


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hin nay gn nh hu ht cc t s dng NGV u hot ng theo chu trnhng c nh la cng bc truyn thng.

b. nh la v lan truyn mng la trong bung chy ng c s dngNGV:

Nng lng ti thiu ca tia la in cn thit t chy hn hpmethane khng kh cao hn nhiu so vi trng hp cc hydrocacbure khcnhau. V vy, h thng nh la ca ng c s dng NGV phi c tnh nngcao hn (bobine phi c cng sut cao hn) m bo to ra mt nnglng nh la t 100 n 110mJ so vi 3040mJ i vi ng c xngtruyn thng.

Mt khc, gii hn thnh phn hn hp c th chy c i vi khmethane rng hn cc loi hydrocarbure khc nn ng c c th lm vic vihn hp ngho hn.

Tc lan trn mng la ca hn hp methane khng kh tng ithp (hnh 2) c im ny lm gim tnh nng ca ng c v lm tngtruyn nhit t mi cht cng tc qua thnh. khc phc tnh trng nyngi ta tng cng thm vn ng ri ca hn hp trong bung chy. Tuynhin tc lan trn mng la thp ca hn hp methane khng kh c uim l lm gim n ca qu trnh chy nh gradient p sut nh.

Hnh 2. chy (m/s) ca methane, propane v isooctane (iu kin banu: p sut 30 bar, nhit 900oK)

c. Thnh phn v nhit ca sn phm chy:Methane ch cha 75% khi lng carbon so vi 8788% i vi nhin

liu lng truyn thng. Trong iu kin chy hon ton l thuyt, thnh phn

CO2 cc i trong sn phm chy ch t 11.7% so vi 14.5% i vi iso-octane. Cng nh hm lng carbon trong methane thp nn khi ng c lmvic vi hn hp giu, thnh phn CO trong kh x thp hn khi s dng cc


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hydrocarbure khc. Nhit mng la ca hn hp methane-khng kh thpnn nng NOx trong sn phm chy cng thp.

III. Cc k thut lin quan n t s dng NGV:

Ging nh khi vn hnh, s dng cc thit b p lc khc, i vi tNGV chng ta ch cn phi xem xt cc iu kin v khi lng, th tch, an ton ca bnh cha nhin liu kh p sut cao.

1. Bnh cha nhin liu NGV trn t v h thng cung cp:a. Bnh cha NGV trn t:

Hnh 3: B tr bnh cha NGV trn t

Gii php c in nht l s dng bnh thp cha NGVdi p sut khong 200 bar. Theo qui nh an ton, bnhcha phi chu c p sut th nghim 600 bar phngn v trong trng hp n b sy nng (khi b ha hon chng

hn). iu ny lm gim kh nng cha cc i ca bnh(khong 0.15m3N NGV i vi 1kg v bnh cha).Ngy nay, ngi ta a chung nhng loi vt liu khc,

chng hn nh nhm thng hay nhm gia c thm si thytinh, vt liu composite vi sn bng si thy tinh hay sicarbon. Kh nng cha kh ca cc bnh ch to t cc vtliu khc nhau trnh by trn bng 4. Bng ny cho thy rngnhng vt liu mi c th cho php nng sc cha NGV lngp 4 ln so vi bnh bng thp c cng khi lng.


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Vt liuKh nng cha

m3n/kg bnh cha 200bar

Thp thng 0.13-0.14

Thp tt 0.18-0.20

Nhm thng 0.19-0.20

Nhm gia c si thytinh

0.28-0.38

Composite snbng si thy tinh

0.40-0.50

Composite snbng si carbon

0.50-0.70

Bng 4:Kh nng cha (m3N) i vi 1 kg bnh cha lm bngcc vt liu khc nhau p sut 200 bar

Ngi ta nhn thy d s dng loi vt liu no i na th p sut khtrong bnh khong 200 bar l ti u nht.

Mt phng php khc cha NGV trn t l dng vt liu hp th.Vt liu ny c th l than hot tnh hay oxyde kim loi. u im l chngth hin kh nng cha kh (trn mt n v khi lng) cao (hnh 4) v cth lm vic p sut thp (3040 bar). Trong iu kin , gi thnh nn kh

thp hn v bnh cha c th c ch to theo nhng nh dng khc nhaucho ph hp vi s b tr bnh cha trn xe (bnh cha NGV thng thng p sut 200 bar phi c dng hnh tr). Bnh cha nhin liu kiu hp thang c nghin cu hon thin. Vn gii quyt l khng ch qu trnhnhit din ra khi hp th kh (ta nhit) v khi gii phng kh (thu nhit), khnng hp th kh, tui th ca vt liu hp th... Hin nay, ngi ta tc p sut lm vic 35 bar vi kh nng cha kh t 125180 lt i vimt lt th tch bnh cha, ngha l t c khong 50-80% kh nng chaca bnh thp thng thng p sut 200 bar.

Tuy nhin cho n nay, vic cha kh NGV di p sut cao vn l giiphp thng dng nht. V vy, trn t s dng loi nhin liu ny ngi taphi lp cc thit b an ton trnh s c chy n trong trng hp kh b rr. Trong thc t ri ro ny rt t xy ra v methane nh hn rt nhiu so vikhng kh (t trng so vi khng kh l 0.55) nn b khuch tn nhanh chng,kh nng t c hn hp trong gii hn bc chy l rt thp.


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Hnh 4:Kh nng cha kh trn than hot tnh 210oC

m bo an ton v p sut, trn h thng cung cp nhin liu NGVngi ta lp t mt van an ton tc ng p sut 350bar. p sut ny cth xy ra khi t b ha hon. Kt qu th nghim trong trng hp chy xecho thy kh thot ra khi van an ton gy chy nhng khng n. i vi xe

bus chy ga, bnh cha kh thng t trn trn xe (hnh 5).

Hnh 5:S b tr tng th h thng cung cp NGV trn t bus

b. H thng cung cp NGV:


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Chng ta phn bit hai trng hp: trm dch v cung cp kh tp trungv my nn gia nh gip cho ngi s dng np NGV ngay ti garage camnh.

cc nc c h thng ga thnh ph, trm dch v NGV c ba chcnng:

- Ni vo mng phn phi kh thin nhin ca thnh ph.- Nn kh n p sut hn 200bar v d tr mt s bnh kh cung cpnhanh trong nhng gi cao im.

- Phn phi kh NGV cho t bng ng mm.Thi gian np NGV cng nh cng tt, thng khong 2 n 10 pht

cho mi xe. iu ny i hi phi cha ga trong bnh d tr trm c p sutcao hn nhiu so vi p sut bnh cha kh trn t. Thng thng p sutmy nn khong 250bar. i vi mt trm dch v np kh cho 1000 t/ngy cn phi c my nn c cng sut khong 100kW.

Cui cng cn ni thm rng, khi cung cp NGV, my nh lngthng c chia khng phi theo m3 kh cung cp m theo lt xng tngng cho ngi s dng c th so snh vi nhin liu lng truyn thng.

Ngoi ra, cc nc pht trin c h thng cung cp kh thin nhintrong thnh ph, ngi ta cn s dng my nn c nhn cung cp NGVcho t ngay ti nh ngi s dng. H thng ny m bo np ga chm,khong 4lit/gi vi p sut 200bar.

2. T chc qu trnh chy:Hai dng t c th dng NGV l t chuyn dng v t bus.

Ty theo dng s dng, gii php k thut v t chc qu trnh chy c thkhc nhau.

t chuyn dng thng dng cho ng c xng nn khi ci to nsang dng NGV cn ch n vic tng t s nn. T s nn ca ng c chy

NGV c th chn cao hn nhiu so vi ng c xng do ch s octane camethane ln. Thng t s nn ca ng c NGV l 12 hoc 13. Cng nhng c xng, nng cao hiu qu lm vic x l nhim bng b xc tc ba

chc nng, b to hn hp phi iu chnh thnh phn hn hp f quanh gi trchy ton l thuyt.

Vic ci to xe bus nguyn thy dng ng c Diesel sang dng nhinliu kh NGV phc tp hn v phi thm h thng nh la cng bc v tchc qu trnh chy nh ng c xng. Trong iu kin gim nhimmi trng v tnh nng kinh t ca ng c, ngi ta c th p dng hai gii

php k thut sau y v hai gii php ny ang l i tng ngin cu tiptc pht trin:

- Gii php th nht l cho ng c lun lm vic vi thnh phn hn

hp chy hon ton l thuyt kt hp vi vic x l kh thi bng b xc tc bachc nng. u im ca n l gim mc pht nhim nhng nhc iml hiu sut gim so vi ng c Diesel.


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- Gii php th hai, t c tham vng lm gim nhim mi trng hnnhng c kh nng lm gim sut tiu hao nhin liu. Gii php ny cho phpiu chnh thnh phn hn hp theo iu kin vn hnh v u tin s dnghn hp ngho.

IV. Cn bng nng lng v nh hng n mi trng ca h t NGV:Sau y chng ta s kho st s cn bng nng lng lin quan n qutrnh cung cp nhin liu kh thin nhin (vn chuyn, nn v phn phi) vtnh nng ca ng c s dng NGV, t bit l tnh nng lin quan n vn nhim.

1.Tiu tn nng lng lin quan n vic vn hnh h thng NGV:Vic nh gi tnh kinh t ca h t NGV cn phi xem xt n s cn

bng nng lng trn ton b cc cng on t khi khai thc kh m n khi

s dng trn t. Bng 6 gii thiu nhng s liu so snh v cn bng nnglng ca NGV v nhin liu lng truyn thng. tiu tn nng lng cphn b trong 5 cng on: sn xut, vn chuyn, lc, phn phi v nn (kh)trc khi s dng. i vi kh NGV, nng lng tiu th ca cc cng ontrc khi np vo ng c chim khong 16%. Mc tiu tn ny tng itt so vi xng. V phng din ny, du Diesel kinh t nht, ngay c trnghp du Diesel cha t l lu hunh thp (0,05%).

Cc cng on Xng Du diesel GPL-C Kh thinnhin

uc t kh qutrnh khai thc

3.0 3.0 3.0 1.8

Tiu th trn hintrng

1.0 1.0 1.0 -

Vn ti 1.9 1.9 1.9 8.0

Lc 12.5 6.5 3.5 -

Tn tht lc 0.3 0.1 0.1 -Phn phi 0.5 0.5 1.0 0.5

Nn - - - -

Tng cng 19.2 13.0 10.5 16.3

Bng 6:Phn b nng lng tiu th trc khi n ni s dng ca cc loinhin liu khc nhau

2 . Tnh nng ca t:a. i vi t thng dng:


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Nh chng ta trnh by vic chuyn i t thng dng s dngnhin liu lng sang s dng kh thin nhin NGV i hi mt s ci to ngk i vi ng c: nng cao t s nn, nng cao cng sut h thng nh la,c bit phi l ci to h thng cung cp nhin liu v bnh cha. Trong phnny chng ta s nh gi tnh nng ca ng c v vn nhim.

Tnh nng:V hiu sut, ng c dng NGV c th d dng t c hiusut cao hn ng c xng khong 10% nh t s nn cao. Khi np trctip nhin liu th kh vo ng np, h s np ca ng c b gimdn n cng sut ng c gim (khong 10%). Tuy nhin s tt gimcng sut c th b tr nh s gia tng hiu sut ng c. ng c sdng NGV c tnh nng v ng hc (gia tc, qu , tc cc i...)tng ng ng c xng. Mt khc, nhin liu NGV do dng kh nnt b nh hng bi qun tnh trong giai on qu nn ng c lm

vic mm mi hn. Cui cng, ng c s dng NGV khng c nhngnhc im lin quan n nhit mi trng nh ng c dng nhinliu lng. nhim:

Cng nh i vi nhng nhin liu khc, c impht sinh nhim ca ng c dng NGV lin quann thnh phn hydrocarbure ca nhin liu, (thngnhin liu NGV cha t nht 90% methane). Bng 7 sosnh thnh phn hydrocarbure trong kh x trc khivo b xc tc 3 chc nng khi ng c s dng nhinliu NGV v xng. Khc vi ng c xng, trong kh xng c NGV hu nh khng c hydrocarbure no chn 4 nguyn t carbon, c bit hn na l khng cs hin din ca thnh phn hydrocarbure thm.

Lin quan n vn to ozone h tng khquyn, kh thi ca ng c NGV c hot tnh thp hnng c xng n 2 ln. Tnh cht ny ch yu l donhin liu NGV cha phn ln methane, thnh phncc hot tnh rt thp hoc c th b qua.

Mt khc, nhin liu NGV khng bao gi gy trngi i vi b xc tc ba chc nng do thnh phnlu hunh nh trong trng hp nhin liu lng. Tuynhin, s xy ha methane cn li trong kh x rt khkhn. Mun loi tr trit cht kh ny cn s dngmt b xc tc c bit.


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Bng 7: So snh thnh phn hydrocacrbure trong khthi ca ng c dng xng v dng NGV. Mu cly pha trc b xc tc, theo chu trnh ECE+EUDC

S liu so snh trong vi trng hp in hnh:Sau y l s liu so snh ca vi trng hp ng cxng v ng c NGV. Trng hp th nht (bng 8),nu xt hai ng c c cng t s nn, cng kt cung np, cng h thng nh la v h thng phn

phi kh th t NGV c mc pht sinh nhimthp hn ng c xng khong 50%.

Bng 8: Gim nhim nh b xc tc i vi ng c NGV (t l hn hpf=1)

Trng hp th hai, nu xt mt ng c cthit k chuyn i chuyn dng nhin liu NGV thng c dng NGV c mc pht nhim rt thpso vi ng c xng c cng cng sut v mmen(bng 9).

So snh tnh nng ng cdng gasole v kh thin

nhin

Nhin liu

Diesel Kh thin nhin


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PCI (kJ/kg) 42800 49100Ch 1400 1260M men 1180 1000

Cng sut 173 185 m c 0.56 0.61

Sut tiu hao nhinliu (g/kWh)

204 186

Hiu sut ton b 41.2 39.4

Bng 9: So snh momen cc i v hiu sut ca ng c Diesel v ng cNGV

b. Xe bus v xe vn ti:


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Hnh 8:Xe but s dng NGV

nh gi mc pht sinh nhim cng nh tnh nng ca t phthuc nhiu k thut to hn hp: hn hp ngho hay hn hp c thnh

phn chy hon ton l thuyt vi b xc tc 3 chc nng.

Tnh nng:ng c Diesel tng p khi chuyn sang s dng NGV vi b

xc tc 3 chc nng v hn hp c thnh phn chy hon ton l thuytth tn tht hiu sut s rt ln, c th ti 20%.

Ngc li nu dng k thut hn hp ngho, khi ng c NGVlm vic vi b tng p th hiu sut cao hn (xp x ng c Diesel nguynthy) v momen cc i chp nhn c. Bng 8 cho chng ta thy s sosnh gia ng c NGV v ng c Diesel nguyn thy.

nhim:


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Bng 10: Mc pht nhim ca ng c dngNGVBng 10 cho chng ta mt vi v d lin quan n mc pht nhim

ca t vn ti s dng NGV. Chng ta nhn thy trong mi trng hp,mc CO v b hng rt thp, mc HC i lc gn vi gi tr cho php

bi lut mi trng, nhng ch cha phn ln methane (khong 90%), cn licc thnh phn khc rt thp.

Cn v mc pht sinh kh NOx, kh x ng c NGV c nng NOx rt thp nu ng c lm vic vi f=1 v c lp b xc tc 3 chc nng.Nng ny cao hn mt cht nhng vn nm trong gii hn cho php nudng hn hp ngho.

Nhng phin phc c bit ca ng c Diesel (n, hi, khi en...) sc gim i rt nhiu i vi ng c NGV. Mc n gim c khong 3db khi ng c hot ng khng ti i vi t bus thnh ph.

V mi hi, cht ph gia cha lu hunh (THT: Telrahydrothio-phene)

pht hin s r r c thm vo kh thin nhin vi thnh phn rt thp(20 hay 25mg/m3) nn b t chy hon ton. V vy nn kh x ng c NGVrt t hi so vi kh x ng c Diesel.

3. nh hng i vi hiu ng nh knh:Methane cng nh CO2 v N2O l kh gy hiu ng nh knh mt cch trc

tip v vy ngi ta rt quan tm n vic nghin cu nh hng ca vicpht trin ng c NGV n vic nng ln ca bu kh quyn.

Chy hon ton l

thuyt vi b xctc 3 chc nng

Chy hn hp

ngho vi b xctc oxy ha

Tiu chunEuro1996

CO 2.5 0.3 4


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HC 0.5 0.2 1.1NOX 3.5 2.5 7.0B hng 0.05 0.05 0.15

(n v tnh: g/kWh)Bng 11:Pht nhim ca ng c cng nghip dng NGV

Trong thc t, ng c NGV pht sinh nhiu methane nhng t CO2 so ving c nhin liu lng. V vy, lng cht gy hiu ng nh knh trong khx ng c NGV thp hn khong 25% so vi ng c xng v 5% so ving c Diesel (Bng 12). Do , vic s dng NGV s lm gim i ng klng kh gy hiu ng nh knh trn phm vi ton cu.

Xng Diesel NGVTrc b xc tc 356 280 267

Sau b xc tc 310 251 231Bng 12: So snh mc pht sinh kh gy hiu ng nh knh i vi ngc dng xng, Diesel v NGV (gCO2/km), theo chu trnh ECE

C. Hng Pht Trin Trong Tng Lai:Nhn chung, ng c dng NGV c rt nhiu ha hn i vi t hot

ng trong thnh ph hay vng ven , nhng khu vc tnh trng nhimmi trng do phng tin vn ti gy ra ngy cng tr nn trm trng. mts khu vc trn th gii, ngi ta bt u s dng NGV cho t chy

trong thnh ph. Chng hn Buenos-Aires, tt c taxi u dng NGV. nhng thnh ph ln ca M, chng hn New York, ngi ta xy dngnhiu d n quan trng cho vic chuyn t nhin liu lng sang NGV.

Nhiu quc gia khc nh , Canada, H Lan... cch y kh lu xy dngnhng c s h tng phc v cho vic pht trin t dng NGV. cc ncny t dng NGV ngy cng c nhn rng. Cui cng ngi ta d kins gia tng t NGV nhng quc gia sn xut kh thin nhin nhMalaysia, Trung Quc... nhng quc gia ny s lng t ngy mt giatng nn vn nhim mi trng khin ngi ta phi quan tm n NGV.

Nhng d kin trn cho php chng ta d on c rng, trong thi giantrc mt (trong vng t 5 n 10 nm ti), s lng t dng NGV trn thgii s tng t 2 n 5 ln.

D nhin s pht trin NGV nhanh hn cng c th din ra nhng vimt s iu kin. Trc ht loi nhin liu ny cn cho thy tnh u vit chcchn so vi nhng nhin liu ang cnh tranh nh nhin liu kh ha lngLPG. Hin ti NGV c u im khng th ph nhn nhng u th ny chachc cn c duy tr trong tng lai. Mt khc, ngi ta ch tip tc nghincu s dng nhin liu kh nu nh nhng gii php k thut v x l nhimkh x ng c nhin liu lng khng ci thin c so vi yu cu ca lut

mi trng. Cui cng, nh nhng nhin liu khc, s xm nhp ca NGVi hi:


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- Chnh sch thu khuyn khch ngi s dng.- C s h tng phc v vic cung cp NGV cho t (Trm dch v

cng cng hay c nhn, hnh 9).- Gii quyt c vn tm l ca ngi s dng lin quan n tnh an

ton ca t dng NGV..

Hnh 9: Trm dch v cng cng cung cp NGV cho t

pin nhien lieu mat troi

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