INFLUENCE OF DUST IN SOLAR CELLS USED FOR MEASURING SOLAR RADIATION
Lillo, I; A oyo, A.M.; Sil a, M; Ba ea J.M.
Escuela Supe io de Ingenie os de Se illa
A enida de los Descub imien os, s/n
41092. Se ille (SPAIN)
e-mail: isido olill[email p o ec ed]
ABSTRACT: The pho o ol aic cells (PV) a e commonly used as global adia ion measu emen de ice, e en hough
when i has been p o ed ha he e a e signi ican di e ences wi h espec o using py anome e s. The di deposi ed
on he su ace o he PV is one o he mos in luen ial ac o s in he measu emen o he sola adia ion. In his wo k
we ha e made expe imen al measu emen s wi h ou iden ical cells, wo cleans and wo di ies wi h di e en soil
densi y (0.2 g/m2, 0.4 g/m2, 0.8 g/m2, 1.2 g/m2 and 1.5 g/m2) and di e en size pa icles (< 125 μm) compa ing he
esul s and ob aining a co ela ion be ween he densi y o he dus and he di e ence be ween he measu ed i adiance
o clean and di y cells o each pa icle size.
Keywo ds: Sola adia ion, sola cell, py anome e .
1 INTRODUCTION
Py anome e s a e nowadays he mos accu a e senso
o measu e he sola global adia ion due o hey co e all
sola adia ion spec um. Howe e , PV cells, ha only
co e a ac ion o he sola adia ion spec um depending
on he echnology, a e also used as a measu emen de ice
o sola global adia ion. The e a e di e ences be ween
bo h kind o de ices, py anome e s and PV cells, and he
alues gi en by PV cells a e usually lowe han hose
gi en by py anome e s [1].
On he o he hand, PV cells a e cheape han
py anome e s and when i is needed o e alua e he
pe o mance o a PV plan , he ac ual a ailable global
adia ion is mo e p ecisely gi en by a cell (made o he
same echnology han he plan ) han by a py anome e ,
because he incidence angle and spec um losses o he
plan a e accoun ed on he cell measu emen s bu hey a e
no on he py anome e measu emen s.
The di e ence be ween he measu emen s om PV
cells and py anome e s is de e mined by mul iple
a iables as he cell echnology, he cell empe a u e, he
spec al esponse o he cell (cha ac e ized by he
humidi y and he cloudiness index) and, ob iously, he
di le el o he cell and o he py anome e . A e nine
mon hs o measu emen s i has been p o en ha he
highe he humidi y and he cloudiness he lowe he
di e ences be ween he PV cell and he py anome e a e,
while he highe he incidence angle he highe hese
di e ences a e.
A ele an ac o ha a ec s o he measu emen s
om PV cells is he dus le el. In gene al e ms, he di
deposi ed on a su ace a ec s, among o he s, o he
ansmi ance. In a sola cell, as he p o ec i e su ace
ansmi ance is a ec ed (usually glass), he cell esponse
is in luenced. This e ec on he asmi ance has been
ex ensi ely s udied o se e al ma e ial and di e en
wea he condi ions [2,3].
The e ec o he dus on a PV de ice has been also
analyzed and i has being de e mined he in luence o he
dus on he pe o mance o a PV module. The s udies
ha e been based on he wea he condi ions o he si e
(dese a eas, humidi y, and wind speed), he o ien a ion
and he il o he module o sola cell and he
cha ac e iza ion o he dus , especially om he size, he
densi y and he geome y o he pa icles. [4,5].
The e a e e en s udies ha ha e aking in o accoun
he in luence o he di on PV modules as a unc ion o
he cell echnology [6].
As a summa y, in e e y case he ollowing e ec s
ha e been obse ed:
On one hand he highe he di on he cell he lowe
he sho -ci cui in ensi y and he ou powe a e,
ela ion ha can be app oxima ed by a leas squa es
i . On he o he hand, he open ci cui ol age does
no depend on he di [7].
In addi ion he sola cell deg ada ion is mo e
signi ican o ine pa icles han o coa se
pa icles [4].
The PV cell e iciency dec eases wi h a much highe
slope o dus densi y lowe han 1.5g/m2. F om
his alue, he pa icles begin o be deposi ed one
abo e he o he , and hen hey do no co e mo e
e ec i e a ea o he [7].
The sola cell il di ec ly a ec s o he dus
accumula ion. So, de ices wi h li le inclina ion
show a highe end o he accumula ion o dus .
Mo eo e , he ansmi ance dec eases as he il
angle is dec easing [3].
The in luence o he cosine ac o is decisi e on he
eliabili y o a sola cell esponse. In his sense, o
incidence angles highe han 20º, he cell
e lec ance inc eases apidly and his esponse is
ou o eliable alues [8].
Wi h espec o he ai mass, he s udies show ha
his ac o is signi ican o sola ele a ions up o
30º [8].
The Bonne and Saps o d s udy [1] p oposes wo
calib a ions cons an o co ec he adia ion da a
eco ded by a silicon cell: one o clea sky and he
o he o o e cas sky.
Co ela ions ha e been de eloped o compensa e he
de ia ion on he esponse ha a sola cell
expe imen due o empe a u e changes and he
sola spec um [9]. The esponse imp o es
signi ican ly when i is co ec ed by sola spec um.
Anyway, di use adia ion esul s show a highe
de ia ion han di ec ones.
The a iables ha in luence on he dus quan i y ha
i is deposi ed on a su ace is qui e s udied opic.
Dus induced deg ada ion o py anome e sensi i i y.
All hese conside a ions show he mul i ude o a iables,
28 h Eu opean Pho o ol aic Sola Ene gy Con e ence and Exhibi ion
3567
besides dus , ha in luence on he pe o mance o a PV
cell as a sola adia ion measu emen de ice.
2 OBJECTIVE
The pu pose o he wo k is o analyze and p o e
expe imen ally he in luence o dus in he measu e o he
sola adia ion wi h pho o ol aic cells depending on he
densi y and size o he dus and in he le el o i adiance.
I has been ca ied ou by he expe imen al compa ison
be ween clean and di y iden ical cells.
3 HYPOTHESES AND METHODOLOGY
This pape answe s his ques ion unde he ollowing
assump ions:
Two iden ical calib a ed py anome e s ha e been
used (PL and PS) and ou iden ical calib a ed
monoc is aline silicon PV cells. The cells a e
encapsula ed by pai s, wo o wo. One o his pai s (CL1
and CL2) has been kep always clean (cleaned dia y),
while he o he pai (CS1 and CS2) has been di ied using
di e en soil densi ies (0.4; 0.8; 1.2 and 1.5 g/m2) and
di e en pa icle size o clay and sil (be ween 0 μm and
65 μm o clay and be ween 0.65 μm and 150 μm o
sil ).
In he same way one o he py anome e s has been
kep always clean (PL) and he o he has been di ied in
di e en le els (PS).
E e y de ice has been placed on a ho izon al su ace.
The da a ha e been eco ded e e y i e seconds and he
mean alue o bo h he clean and he di y cells ha e
been de e mined. As a p e ious s ep i was p o ed ha
he maximum e o in he adia ion measu es was less
han 0.1% o he ou cells and less han 0.05% o he
wo py anome e s.
4 THEORETICAL BACKGROUND
In Figu e 1 he absolu e di e ence be ween he
measu emen s om he clean cells and he di y ones is
shown as a unc ion o he mean alue measu es by he
clean cells. This i s igu e is o clay pa icles (be ween
0 μm and 65 μm) and o di e en di y densi y alues
(0.2, 0.4, 0.8, 1.2 and 1.5 g/m2). I can be obse ed ha
he highe he densi y and he i adiance, he highe he
absolu e di e ence be ween he clean and he di y cells
is. The maximum alue o he di e ence is a ound 20
W/m2 o a densi y o 1.5 g/m2.
Figu e 1. Absolu e i adiance di e ence be ween
clean and di y cells o i e di e en di densi ies as a
unc ion o i adiance. Clay
Simila ly, in Figu e 2 he absolu e di e ence be ween
he measu emen s om he clean cells and he di y ones
is shown as a unc ion o he mean alue measu es by he
clean cells, bu o sil pa icles in his case (be ween 65
μm and 125 μm) and o di e en di y densi y alues
(0.2, 0.4, 0.8, 1.2 and 1.5 g/m2). Again, he di e ence
inc eases wi h he di densi y and also wi h he
i adiance. Fo low densi ies, lowe han 0.4 g /m2,
Figu e 1 and Figu e 2 a e e y simila bu hey a e no so
simila o highe densi ies han 0.4 g /m2 ( o sil he
maximum di e ence be ween clean and di y cells is
a ound 40 W/m2). In any case he absolu e di e ence
depends mainly on he i adiance mo e han on he cell
empe a u e, he incidence angle o he sola spec um.
Figu e 2. Absolu e i adiance di e ence be ween
clean and di y cells o i e di e en di densi ies as a
unc ion o i adiance.
Figu es 3 and 4 show he same in o ma ion bu in
pe cen age e ms.
Figu e 3. Pe cen age i adiance di e ence be ween
clean and di y cells o i e di e en di densi ies as a
unc ion o i adiance. Clay
Figu e 4. Pe cen age i adiance di e ence be ween
clean and di y cells o i e di e en di densi ies as a
unc ion o i adiance.
28 h Eu opean Pho o ol aic Sola Ene gy Con e ence and Exhibi ion
3568
I is no ed ha he e o in he measu emen inc eases
as he le el o i adiance inc eases in absolu e e ms bu
emains almos cons an in pe cen age e ms o
i adiance le els abo e 300 W/m2 and medium-low di
le els (<0.4g/m2), especially o clay, while o high
le els o con amina ion, he di e ence dec eases as he
le el o i adiance inc eases, eaching a maximum a 200
W/m2.
The esul s show he in luence o he dus le el in he
measu emen o he sola adia ion wi h a PV s a ing ha
he e o s, when exp essed in pe cen age, a e p ac ically
cons an o each densi y le el depending on he dus
pa icle size. This conclusion can be ex apola ed o he
p oduc ion o a pho o ol aic plan .
6 CONCLUSIONS
The absolu e e o be ween he measu emen s om a
clean and a di y cell depends mainly on he i adiance
le el and he pa icle size mo e han on he cell
empe a u e, he incidence angle o he sola spec um.
A di y monoc is aline PV cell makes a bigge
absolu e e o when he i adiance and he pa icle size
a e highe . The maximum alue o he e o is a ound 40
W/m2 o 1000 W/m2, o a pa icle size o 125 µm and
o a di densi y o 1.5 g/m2. In he same condi ions bu
o pa icles up o 65 µm, he maximum e o is a ound
20 W/m2.
A di y monoc is aline PV cell makes a pe cen age
e o ha p ac ically only depends on he di densi y o
pa icle sizes up o 65 μm.
The same e ec can be obse ed o pa icles up o
125 μm and densi ies up o 0.4 g/m2. Fo highe densi ies
han 0.4 g/m2, he pe cen age e o in he sola adia ion
measu emen depends also on he i adiance le el.
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