Experience from PV system performance (including comparison of on-roof and façade systems in Prague) Vitezslav Benda, Zdenek Machacek CTU Prague, Faculty.

Experience from PV system performance (including comparison of on-roof and façade

systems in Prague)

Vitezslav Benda, Zdenek MachacekCTU Prague, Faculty of Electrical Engineering

radiation temperature

datalogger

Inverter SUNRISE MINI

= 180 V+

-switchboard ~ 230 V

~ 230 Vgrid

connection=

~PV module field

++ +- - -SUNRISEdatalogger

displayunit

PC

In the year 2001, a 3kWp demonstration, on-grid connected

photovoltaic system has been built at the Czech Technical University in Prague on the roof of the Faculty of Electrical Engineering.

In the year 2001, a 3kWp demonstration, on-grid connected

photovoltaic system has been built at the Czech Technical University in Prague on the roof of the Faculty of Electrical Engineering.

PV field 1

PV field 2

PV field 3

=~

=~

=~

Temperature sensor

Radiation sensor

Display unit

Comp. networkEthernet

RJ45

Converter RS 422/RS232

RS 485

RS 232

RS 422

Power measuring

DataloggerFVS 2300E

Grid connection 230 V / 50 Hz

Shunt

Inverter SUNRISE

PC

Installed peak power: 3320 Wp

Total module area: 26 m2 Number of modules: 30 (3 fields of 10)

Latitude: 50.07 °NAltitude: 205 m

http://k313.feld.cvut.cz/solarsys/

Module type Pmax (Wp) Vpm (V) Ipm (A) VOC (V) ISC (A) cell (%) module (%)

RADIX72-112 111,5 17,4 6,41 21,5 7,04 14,9 12,8

RADIX72-108 107,8 17,1 6,29 21,5 6,98 14,4 12,4

Parameters of PV modules at radiation power 1000W/m2, spectrum AM 1,5 and temperature 25°C

PV field Tilt angle Module type Pm (Wp)

1 45° RADIX72-112 1120

2 variable RADIX72-112 1120

3 90° RADIX72-108 1080

Parameters of individual PV fields

Parameters of Sunrise inverters

Type of inverter Sunrise Mini Sunrise Micro

Input voltage 120 - 300 V 120 - 300 V

Nominal input voltage 170 V 170 V

Maximum input voltage

350 V 350 V

Output voltage 230 V,+10/-15% 230 V,+10/-15%

Output frequency 50 Hz,+/-0,2 Hz 50 Hz,+/-0,2 Hz

Output nominal current

4,4 A 3,2 A

Output nominal power 1000 W 750 W

Harmonic distortion < 3% < 5%

Maximum effectivity 93% 92%

Dark consumption 0 W 0 W

A comparison of estimated and measured energy production in period from January 2002 to December 2005

0

2000

4000

6000

8000

10000

12000

14000

Ave

rag

e d

aily

en

erg

y p

rod

uct

ion

(W

h)

Estimation Measured

2005200420032002

Energy produced by individual PV fields in period from January 2002 to December 2005

0

1000

2000

3000

4000

5000

6000

Jan

uary

Marc

h

May

Ju

ly

Sep

tem

ber

No

vem

ber

Jan

uary

Marc

h

May

Ju

ly

Sep

tem

ber

No

vem

ber

Jan

uary

Marc

h

May

Ju

ly

Sep

tem

ber

No

vem

ber

Jan

uary

Marc

h

May

Ju

ly

Sep

tem

ber

No

vem

ber

Avera

ge d

ail

y e

ne

rgy p

rod

uc

tio

n (

Wh

)

PV field 1 PV field 2 PV field 3

2002 20052003 2004

This gives the efficiency decrease of about 0.6% per 1K, which is higher than supposed decrease of cell efficiency (about 0.4% per 1K).

It means that an increase of losses with increasing temperature in other parts of system cannot be neglected.

Temperature dependence of energy conversion efficiency

9,0

10,0

11,0

12,0

13,0

14,0

15,0

Eff

icie

ncy

(%)

-5,0

0,0

5,0

10,0

15,0

20,0

25,0

30,0

35,0

PV

field

tem

pera

ture

(°C

)

Febr

uary

Mar

ch

Nov

embe

r

Oct

ober

Sep

tem

ber

Aug

ust

July

June

May

Apr

il

Efficiency

Temperature

8

9

10

11

12

13

14

0 20 40 60

PV field temperature (°C)

Effi

cien

cy (%

)

August

January

39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58

Temperature distribution over the PV field areas

roof

facade

June, ambient temperature 32 °C

Tilt angle: 45°

Tilt angle: 90°

teplota (°C)

Temperature distribution over the PV field areas

December, ambient temperature -6 °C

roof

0100

200300

400500

600700

800900

8:00 9:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00

Ou

tpu

t p

ow

er

(W)

PV field 1 PV field 2

Shadowing effect

PV field 1PV field 2

Conclusions

• Facade PV system applications can produce about 66% of electrical energy produced by the roof (45° tilted) one

• Efficiency of PV systems is strongly influenced by temperature

• PV field constructions should allow an effective cooling of PV modules