four-element curtainwall panel with pv …

ADVANCED MATERIALS 250 Karl Clark Road, Edmonton, Alberta T6N E4 1

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FOUR-ELEMENT CURTAINWALL PANEL WITH

PV INTEGRATED MODULE TESTING

Test Results

Prepared by

Kaz Szymocha, D.Sc.,

Chris Astle, M.Sc., James Brown

Alberta Research Council.

for

VISIONWALL

June 10, 2004

1

EXECUTIVE SUMMARY

The testing and evaluation of a PV integrated window as described are the subject of agreement between the ARC and Visionwall. The goal of the evaluation is to expose the Visionwall products to operational conditions that simulate the extremities resulting from sudden weather changes, collect data and evaluate PV module performance. A series of 20 test cycles was performed with the Four-Element Visionwall product. The results as presented are evaluated mostly from the position of the user, who's interests are in the reliability of the product when exposed to the harsh northern Canadian weather conditions in Yellowknife. Table of Content

1. Introduction 2. Test Unit Description

3. PV Integrated Window Testing

4. Test Results

5. PV Performance Evaluation

6. Conclusions and Remarks

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1. INTRODUCTION Constant progress in solar energy technologies offer cost reductions and new opportunities in PV applications for commercial buildings. Building applications are one of the major contributors to the growth of solar energy systems. An objective analysis of current solar technologies, their costs, and energy requirements clearly indicate that solar thermal energy development will be most rewarding for remote and cold climate regions. The economics can be further improved if solar system elements can be integrated with building components, such as the walls or windows. This project is part an effort to create an advanced building wall product. This interim report presents the wall integrated PV panel testing results, which is the subject of a contractual agreement between ARC and VISIONWALL Corporation. This testing is not intended to form the basis of any scientific research. The purpose of the testing is to provide a “degree” of confidence in the performance of the PV-building component integrated element. It is assumed that the suppliers of the individual elements undertake their own testing to support their products.

2. TEST UNIT DESCRIPTION

A movable, wood platform with two thermally insulated chambers (two heated cavities) was constructed as shown in Figure 1A and Figure 1B. The interior surface of the 4-element panel, which will simulate an interior building space is supposed to be kept at a constant temperature of 20ºC (enclosed and heated during cold chamber testing and open to ambient when outside of cold chamber). The heated cavities are equipped with portable heaters with thermostats capable of maintaining 20ºC and 30C. The heated cavity widths are about 350 mm.

Three temperature sensors were installed inside the panel during factory assembling process.

• from the exterior lite to the internal film; • interior film chamber itself; • interior lite to film chamber.

Other temperature sensors and a pressure signal line were installed after chamber assembly as shown in Figure 2. As shown a in this figure additional thermocouples were installed to record the frame temperature and exterior (air) temperatures. The sensors were connected to a datalogger and records of data were taken every 10 minutes. An additional independent control system was installed for the PV electrical output (volts and amps) and solar irradiation. The testing/measuring system is shown in Figure 2.

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Removable side cover

Removable side cover

Glass

PV module

Varied temperature from -30ºC to +70ºC

20ºC

Data Logger

490

50 2,102

2,440

1220

240

2,540

Figure 1A. Movable test unit with two chambers (top view).

4

2,440

1182

2,102

50 2,102

1220

2,540

Figure 1B. Side view of movable test unit (side view with side wall removed).

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Data Logger 21 measuring channels

Grid 240V

Thermostat

P11

A14

R

V13

V12

T6

T7 T8

T1

T2

T3

T4

T5

T9

T10

PV module

Frame surface temp. Frame inside temp.

PV temp front Back chamber temp. Front chamber temp.

Air temp.

PV temp back

Glass outside t

Glass inside temp.

Membrane temp.

Outside Testing Pyranometer

Data monitoring, storage and processing

Another set of sensors for reference panel data

10 h lTemperature Data

Blower/Heater

Figure 2. Test unit schematic for performance evaluation of the experimental Visionwall solar -PV integrated panel.

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3. TESTING The objective of this examination is to test and evaluate a four-element curtainwall panel with PV integrated module under the different temperature regimes detailed in Table 1. The specific purpose is to assess the temperature and pressure response of the PV-integrated 4-element panel during simulated installation under varying ambient conditions. The regimes of the Visionwall 4-element curtainwall panel incorporating a photovoltaic module are shown in Table 1 and in Figure 3. Table 1. Predicted Test Period Conditions. Period PV side temp Glass side temp Time Length of

test #A +30ºC +20ºC 10 pm to 6 am 8 hr #B -30ºC +20ºC 6 am to 11 am 5 hr #C +30ºC to 70ºC +20ºC 11 am to 5 pm 6 hr #D -30ºC +20ºC 5 pm to 10 pm 5 hr The most interesting is out-door testing period #C when the panel is exposed to direct sunlight and subjected to thermal shock after stitting for five hours in a cold chamber at -30ºC. Integrated PV module performance is also evaluated during period #C. The panel temperature during out-door testing is difficult to control because of the influence of different, uncontrolled factors like solar radiation intensity, air temperature and wind. The testing procedure is shown in Figure 3. In total 20 cycles are predicted over a period of five days.

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-40

-20

0

20

40

60

80

-2 0 2 4 6 8 10 12 14 16 18 20 22 24 26Time, h

Am

bien

t Tem

pera

ture

, oC

Test outside of building for PV panel performance evaluation (exposure to solar radiation) PV panel temperature

28 30 32 34 362 4 6 8 10 12

Next day 24 hour testing period

Cycle A B C D A B

Figure 3. Periods for window-PV panel testing (20 cycles, 4 testing cycles per day). Testing procedure

• Cycle A - Install heat chamber insulation, heat PV side of panel to +30ºC and hold at this temperature for 8 hours,

• Cycle B - Place test unit in refrigeration chamber, chill to -30ºC and hold at this temperature for 5 hours,

• Cycle C - Remove panel from –30ºC refrigeration chamber, transfer test unit outside building, expose to sun and hold for 6 hours,

• Cycle D - Transfer test unit to refrigeration chamber, chill to –30ºC and hold at this

temperature for 5 hours Continue repeating this process 20 consecutive times, minimizing time lag between each cycle. 4. TEST REULTS Test results are resented in figures from Figure 4 to Figure 12.

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-40

-30

-20

-10

0

10

20

30

40

50

60

70

80

0 2 4 6 8 10 12 14 16 18 20 22 24

Time, h June 1, 2004

Tem

pera

ture

, C

PV temp T1PV temp T2Film T3Glass inside T4Glass outside T5Frame T6Frame T7PV chamber T8Glass chamber T9Air T10PressureIrradiationVoltage

Cycle 1-A 2-B 3-C 4-D 9 Figure 4. Test results for June 1, 2004.

-40

-30

-20

-10

0

10

20

30

40

50

60

70

0 2 4 6 8 10 12 14 16 18 20 22 24


Tem

pera

ture

, C


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Cycle 5-A 6-B 7-C 8-D

Figure 5. Test results for June 2, 2004.

-40

-30

-20

-10

0

10

20

30

40

50

60

70

80

0 2 4 6 8 10 12 14 16 18 20 22 24


Tem

pera

ture

, C


Cycle 9-A 10-B 11-C 12-D

11Figure 6. Test results for June 3, 2004.

-40

-30

-20

-10

0

10

20

30

40

50

60

70

80

0 2 4 6 8 10 12 14 16 18 20 22 24


Tem

pera

ture

,C


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Cycle 13-A 14-B 15-C 16-D Figure 7. Test results for June 4, 2004.

-40

-30

-20

-10

0

10

20

30

40

50

60

70

80

0 2 4 6 8 10 12 14 16 18 20 22 24


Tem

pera

ture

, C


Cycle 17-A 18-B 19-C 20-D

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Figure 8. Test results for June 7, 2004.

Comments Frame expansion as compared to glass reduced as a results lower of the lower temperature range.

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15

30 ºC

Cycle B and D Cycle CCycle A

+20 ºC +20 ºC

70 ºC

+20 ºC +20 ºC

-30 ºC

Figure 9. Patterns of temperature distributions for different cycles for steady state.

0

5

10

15

20

25

30

35

40

0 50 100 150 200Distance, mm

Tem

pera

ture

, C 1-A, 6:005-A, 6:009-A, 6:0013-A, 6:0017-A, 6:00

Figure 10. Temperature distribution profiles for cycles A.

-30

-20

-10

0

10

20

30

0 50 100 150 200Distance, mm

Tem

pera

ture

, C

2-B, 10:406-B, 11:0010-B, 11:3014-B, 11:3018-B, 11:004-D, 22:008-D, 22:0012-D, 22:0016-D, 22:0020-D, 22:00

Figure 11. Temperature distribution profile for cycles B and D.

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0

10

20

30

40

50

60

70

80

0 50 100 150 200Distance, mm

Tem

pera

ture

, C 3-C, 16:007-C, 16:0011-C, 16:0015-C, 14:0019-C, 14:00

Figure 12. Temperature distribution profile for cycles # C.

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5. PV PERFORMANCE EVLUATION As shown in Figure 13, the maximum power achieved during regular testing periods was 133.3W. The average maximum power during the three utilized testing periods was 121.4 W. At this maximum power point, the average load resistance, voltage and current were 7.77 Ω, 29.3 V and 3.99 A, respectively. On the final day of testing an atypical increase in performance was found when the sun was in full view of the solar panel, but was surrounded by an expanse of clouds. The data implied that the maximum power output jumped to 153.5W due to an increase in the solar irradiation to 798W/m2. This piece of data was not used in calculations due to its somewhat rare and inconsistent nature. Efficiency of the solar cells is calculated using the following formula:

)/(*)()(

22 mWnIrradiatioSolarmCellsofAreaWOutputPowerCellSolarMaximumAverageEfficiency =

As displayed in Table 2 the average efficiency obtained throughout the testing period was 12.8%. Power density indicates the average power obtainable per square metre of PV cell installed, based on the current solar cell system of 1.674 m2, and was found to average 72.5W/m2. Table 2. Performance Data for Integrated PV Panel Date Average

Solar Irradiation

(W/m2)

Average Max.

Power (W)

Solar Cell Efficiency

Power Density

(Cell Area)

(W/m2) June 3rd 576.3 127.3 13.2% 76.1 June 4th 561.8 121.1 12.9% 72.4 June 5th 564.5 115.9 12.3% 69.2

Average 567.5 121.4 12.8% 72.5 Figures 13 and 14 show the power curves and irradiation values, and the current-voltage and irradiation values, respectively, for three days of testing.

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Power Curves and Irradiation Values

0

25

50

75

100

125

150

175

200

0.0 10.0 20.0 30.0 40.0 50.0

Voltage (V)

Pow

er (W

)

400

425

450

475

500

525

550

575

600

Vert

ical

Irra

diat

ion

(W/m

2)

1215pm Jun3

1215pm Jun4

115pm Jun7

Figure 13: Power curves and irradiation values from PV panel.

Current-Voltage and Irradiation Values

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

0.0 10.0 20.0 30.0 40.0 50.0Voltage (V)

Cur

rent

(A)

400

420

440

460

480

500

520

540

560

580

600

Vert

ical

Irra

diat

ion

(W/m

2)

1215pm Jun3

1215pm Jun4

115pm Jun7

I di ti

Figure 14: Current-voltage data and irradiation values from PV panel.

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6. CONCLUSIONS AND REMARKS After collecting, processing and analyzing the data, the following conclusions were formed:

• The residence time during the testing periods is sufficiently long to stabilize the temperature profile along the panel.

• The most critical period concerning thermal shock stress on the panel occurs when the panel is

transferred from the cold room (-30ºC) to outside the building and exposed to sun. In full sun the panel temperature was found to increase to 90ºC in less then 80 minutes being heated at rate of about 1.13ºC/min. Maximum PV surface temperature nearly 75ºC were observed.

• There is negligible pressure buildup within the panel. The measured pressure differences, when

the panel undergoes the temperature shock periods, do not exceed 20 Pa.

• The power by the photovoltaic module was approx. 120 W (occasionally up to 150 W) and is significantly lower than nominal 230 W value published by the manufacturer. The reduced output of a PV module is related to its vertical orientation during testing. In standard procedure PV panels are evaluated perpendicular to incident solar radiation

The panel after five days of testing was the subject of rigorous inspection.

• After five days of rigorous testing there was no indication of cracks, foil folding or gap expansion occurring in the panel.

four-element curtainwall panel with pv …

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