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COMPARISON OF PREDICTED AND MEASURED ANNUAL PERFORMANCE OF A ROOF-TOP GRID-CONNECTED PV SYSTEM IN THE IRISH CLIMATE

Authors:
Chibuisi CHINASAOKWU Okorieimoh at Technological University Dublin
Chibuisi CHINASAOKWU Okorieimoh
Brian Norton at Technological University Dublin
Brian Norton
Michael Conlon
Michael Conlon
Michael Conlon
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Abstract

The problem of energy scarcity has reached a global scale as a result of the majority of energy production relying on non-renewable sources of energy. Solar photovoltaic cells use the photovoltaic effect to convert solar energy into electrical energy. Solar energy can reduce emissions of carbon dioxide (CO2) associated with the generation from fossil fuels as the only CO2 emissions are those embodied in their manufacture. A 268.8 m2 area roof-top grid-connected PV system with a total capacity of 49.92kWp was installed at Warrenpoint (54.11oN and 6.26oW) in Ireland. 192 “Renesola” PV modules were installed with a nominal peak output of 260Wp and efficiency at standard test conditions (STC) of 18.5%. System outputs were measured at 15-minute intervals over a year. A system simulation was carried out to predict average annual energy yield, average system efficiency, and average system performance ratio. The system simulation showed that an annual average energy yield of 12,695.2 MJ (3,526.4 kWh) was generated at an average system performance ratio of 85% and average system efficiency of 15.8%. System measurements showed an average annual energy yield of 12,035.8 MJ (3,343.5 kWh) at an average system performance ratio of 85.17% and system efficiency of 15.82%. The system performance ratio measured was greater than the performance ratio predicted by system simulation by 0.17%. The system’s measured efficiency was greater than that given by the system simulation by 0.02%. The average annual energy yield (12,695.2 MJ) predicted by the simulation was greater than the system’s measured annual energy yield (12,035.8 MJ) by 659.4 MJ.
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COMPARISON OF PREDICTED AND MEASURED ANNUAL PERFORMANCE OF A ROOF-TOP GRID-
CONNECTED PV SYSTEM IN THE IRISH CLIMATE

 !"
#$%"
ABSTRACT
&!"!'!
 &"(   )*  !   &
   & + 
"!","-./"* (
!!!. ""!
0.122 . !)& ")"34*  & !
566.7&* "7&-8599 " 1.17/ 
%"96.:;< 34"* "*  &&!
.1=7&">"""(- /!928? &*
"  98)  0 ( * "
&"  " >
"&!(
  ( *"     " ! 9.168.@
-A8.15 7/ * "   &! ( ! 28? "
>!982? *"
"!9.=A82@-AA5A87/&!(!
289$?">!982.?
 &! ( "*   &!
(&""  ( =9$? 
B">*(
==.?    " -9.168. @/&"" 
(*B""-9.=A82
@/1865@
KEYWORDS:
 (    &! (  "
&"*
Introduc!on
& !   "     !' !
&"()*!-.=96/ 
&&+
-   .=.=/    "  !  "," -./
" *  ( ! ! !    .   
""!-9666/&!!34
C""(! ( "(
"  & -    .=91/  (  
&*"""""&!34&-
 .=96/ 0 34    && ""   ( 
-".=92/((
>",&"-.=91/34
"("&!&""
&"&!(- .=91/
Related work
"*!34&!((
  "" D ,& E(   -.=9A/ " F !
&( G !  34  0   (  " 
!(4"
""   &! & ! " 34 &* &  
&("("(-.=95/("*
.5 7& ")" 34  "  * "(  (H & "
,)  I" "   ,)  34 
&&"6=?!""!""(I"")
"34!"%("!
&!!9=7")"34&*&%" " "
-.=98/ ""   &! ( ! 219.?  " # -.=9$/
"  &! ! 99. 7 J&")" 34  
%"(  &! (! $2? ! "(" :&!
3"" ""03!!;!)&#")"34 
%<*""&&*I"
&!&""-"/""&!!!)&")
"34%*&(&H
9  & !  (   ,  34
&!"
. DC&!!34
A "(!-"/"""(+34
5 34"",&"""*.=).8
*&"
!  " !  &  &"" " " 
&!!!)&")"34%""
  & ! !(  ( ! 34  (  
& &* ! 34    +"  
"*"&""("&
Methodology
Site Loca!on and Climate Descrip!on
034,""" &&"- /&&
;"7& %"  8599(" " 1.17"
(34!.122.(")&I!(
*D9
D9(" *! "&&;"
7&%"E
7&   )" *  "  &  ! 51
-2$1?("/@958-2.5?("/@*
D.
January
February
March
April
May
June
July
August
September
October
November
December
76
78
80
82
84
86
88
90
0
2
4
6
8
10
12
14
16
REL.HUMIDITY (%) AIR TEMPERATURE (oC)
MONTH
RELATIVE HUMIDITY (%)
AIR TEMPERATURE (oC)
D.0&";(K"7&
"(G!7&!=557L.
5.A7L.!!*!1$$1
D!9=168-DA-//7"&"
"!!A2L8$L(-DA-//
-M&HLL***LLJ*)L$518/
January
March
May
July
September
November
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
0
20
40
60
80
100
120
DAIL Y SOLAR IRRA DIATION (kWh/m^2/d)
MONTHLY RAINFAL L (mm)
MONTH
SOLAR IRRADIATION (kWh/m2 /day)
MONTHLY RAINFALL (mm)
January
March
May
July
Septemb er
November
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
0
1
2
3
4
5
6
DAIL Y SOLAR IRRADIATION (kWh/m^2/d)
WIND SPEED (m/s)
MONTH
SOLAR IRRADIATION (kWh/m2 /day)
WIND SPEED (m/s)
a. b.
DA"(!"*"&"! 7&
-M&HLL***LLJ*)L$518/
System Monitoring and Method of Data Acquisi!on and Assessment
"F("!*,""
,)&"(34"
,""*""98N)
 ""!*""
!!*H
&O
3!"O
3!(!O"
>!
Results and Discussion
System Simula!ons
34(&!"*"&P
-M&HLL***"*L"*LQLK/
D5*(! "7&")"34
D534("&(!")"! 
"7&3-M&HLL***"*L"*LQLK/
Cable Sizing
&*!"G*("8!"*
-4/=91?"998?&(*"-4/""
*"(! 0 0#
-***"*/*(&**"&(!
9?0"
8&*!"G-***"*/
 4 4 
3*
&(
161.7 5862=7 ==97 8.65.7
;&*"
&(
=91? 998? ===? 9A9?
 91=== A=== 9==== .6===
)( .8.1.
88.
98=..8.
1.
88.
98=.
  " ! J& ")"34  D 5 &
!"!""*D8D")(
"(&*"&(=91?4*
( &*   " &( ! 998?%  4 * 
(&*"&(I(!5=7"
&&G*(&*"&(*
9
D8#")"34!")"
9I(!"&&G*(&*"
&(
.34"%&!
%.")"34!H
-/ 34"(&*
-/ ,3*3-33/&(&*&
-'" .=9$/
-/ #")"L0&0&*!"
-/ &*"*D5-.=92/
System Simula!on Results
Energy Yield and Performance Ra!os
D   ! (  &! (* 21?  &I
(*2527L7&"   & - "/*5.A92
7-98.A552@/."(J.=5AA-A/D
5    " *A8.15 7 -9.168.@/  
&!"*2A?&!(*28?"
    > * 982?  &I  ;( - &I/ 
3"-?"/" >-R / !""34
"-9/-./"-A/H
 &IS
Total Energy Yield
PV Module Capacity
-9/
?"S
Energy Yield
Total Energy Yield
T9==?-./
U SU34V"V T3; -A/
7H
  W"   "     ! *M  -7/
"")"34
34 " &   "   , & ! ")" 34
" """  "(-& !.8 X "
9===7LY"!98/
 W"    ! *M  -7/ "   ")" 34
&(&"
A ! (
!34" 96.
3&* 566.7&
!34 .
0&*! 5===7
0(&* 5===7
0(&*( 2=9?
0" 5.A927
! 9==?
3!( 21?
&I" 2527L7&
-?!34/ )))
"" ===40
."(J.= 5AA
50  (;
 "
Z7[
"
Z@[
"
&
Z?[

&!
(Z?[

>
R Z?[
@ 6=2 A.16 . 2. 98.
D 911A 862$ 5 28 982
 AA=5 99265 2 2$ 91.
0& 56$A 9$6=A 9. 22 91A
 159= .A=$1 98 2$ 91.
@ 1A2A ..6$6 98 2$ 91.
@ 8685 .95A5 95 21 91=
0 8959 928=2 9. 21 91=
& A188 9A982 6 21 91=
 ..=9 $6.5 8 25 981
 9=85 A$65 . 2. 98.
 1$9 .591 . 2= 956
 5.A9$ 98.A5.
0 A8.15 9.168. 2A 28 982
SYSTEM MEASUREMENTS
System Measurements
"\&! (*289$?&I 
"*2=A1$7L73""*5=9..7-9555A=9@/-
 8/   " * AA5A8 7 -9.=A82 @/  
" & * 2A? "   >*
982.?"9=
Performance Comparison of Measured and Simulated Results
(" * " 
&!(! 3; *=9$?&!(
! (3;  %   "  > !   
R *==.?(>!R  
"-98.A5.@/!(*
 "!-9555A=9@/$6996@(
"""""*
(! D!!"(
&&"  ( * *    "  -
D1/!FC(&!(
(-D1"85/
!C(*!"!(
D1&!"""&!! 7&!)
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8"&!! 7&34 
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@ $81 .$.= 922 218 919
D 856 96$8A 9A$ 2.= 98.
 .A$A9 285A9 86. $9= 9A.
0& 5658 9$2=.91 9.AA 2A$ 988
 $99= .8868 9$$. 6.= 9$9
@ 8$.5 .=1=18 95.$ 2$1 91A
@ 829$ .=65= 958= 25A 98$
0 8=29 92.69 9.11 281 986
& A8119 9.2A2 26= 212 919
 ..A65 2=1. 81= 228 915
 9.86 58A9 A95 6== 91$
 $=. .8.1 9$8 25= 981
 5=9.. 9555A=9
0 AA5A8 9.=A82 2A 289$ 982.
Inverter Percentage Conversion Loss
7    !340
*""34"0*1
("&F(-5/"
"!!"F(-8/
&"!*-5/H
%&S
DC Energy−AC Energy
DC Energy
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EDC
T9==?-8/
7HU   >  ( ! &-0 / 
&-/(&"9==?
1"0>"&
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@ .$1A .$.= 625= 91
D 96$21 96$8A 662= =9$
 215=. 285A9 626= 99.
0& 9$29=A 9$2=.91 6668 ==51
 .1=6. .8868 629= 989
@ .=1.2 .=1=18 666= =9=5
@ .=62= .=65= 6629 =969
0 92A.= 92.69 6625 =982
& 9.66= 9.2A2 622. 99$
 29.9 2=1. 66.$ =$A
 585= 58A9 662= =.
 .85= .8.1 6658 =88
 9585=A9 9555A=9
0 9.9916 9.=A82 665. =1.6
!(B&"* 
"$
$&!(* 
 (   
9 0
&!(!28?
0&!(
!289$?
. &I"
2527L7&
&I"2=A1$
7L7&
A "
5.A9$7-98.A5.@/
"5=9..7
-9555A=9@/
5 
"&2AA?
"
&2AA?
8 
>982?
>
982.?
Conclusion
,!""(*""
&"&(&(C"34&
&!",!&
&&"&(!34&("
&"(("&("-""
("/G"34&""&!
(*"&&"!&&"(%"!
"""!34&"!F
!*""("&"*+34
&&!
0"+C&&*"!
34""""""&!34""
&
References
" &30 00 E  " E  ; 0-.=92/
]3! ( ! ")" J&  34  ! 
"B 0  " ! ' %"  ;& 5 && 851)88A
https://doi.org/10.1016/j.egyr.2018.08.002
E("0 &E0-.=9A/];*!&G&((
FB;* ;..&&585)518
% K" 0K"""  ;G 0#-.=92/] " "(! 
&!!")"34&&"(
!0 B9=9=91L'.=92=A98$
'   -.=9$/]3 *""& !H 0
( *     &&( "&  "
&&!&%" ;* B;$=&&
.62)A9A
" @W W#  -.==$/ ] + !* ( "("
G)&! ! ")" & B
33;0&&98&&A8A)A12
K"0%"E E"'0-.=91/]%&!")
"34&&((*"G)
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... As the chosen PV systems, shown in Table 1, and PV system in Niš have similar power and PV configurations, it can be concluded that PV system efficiency and PR are lower in countries with a subtropical climate due to the negative impact of higher ambient temperatures and, therefore, higher solar module temperatures. PV systems with other PV technology and higher powers, installed worldwide and shown in [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27]32], are not comparable to a given PV system in Niš. Table 1. ...
A Statistical Analysis of Long-Term Grid-Connected PV System Operation in Niš (Serbia) under Temperate Continental Climatic Conditions
Article
Full-text available
  • May 2023
This study analyzes the grid-connected PV system performances over a 10-year period under temperate continental conditions in Niš. Based on the experimental results, we found the following: the 10-year yearly average values of PV system efficiency, Yf, CF, and PR are 10.49%, 1178.51 kWh/kWp, 13.45%, and 0.87, respectively. The yearly average value of PV performances for a 10-year measurement indicates that the behavior of the given PV system over 10 years does not change significantly. Besides, a mathematical prediction model was obtained through regression analysis, and ANOVA was applied for testing the model’s validity. It is shown that the obtained model is statistically significant and enables prediction better than a simple average, the mean values of PV electricity are not changed statistically significantly over the 10 observed years, and there is a statistically significant difference in POA mean radiation during the months over 10 years. Based on the obtained model and POA radiation values, a prediction of the PV system output can be made for similar PV installations. The analysis presented in this study significantly impacts energy prediction, PV energy modeling, and the economics and profitability of the grid-connected PV system utilization, as well as the PV systems’ operation planning and maintenance.
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