This presentation explain how does Solar Cell panel power output are changing as a function of solar illumination. The specific aim of presentation session is to introduce various method in predicting solar cell power output using manufacture data sheet given in STC rating. Six calculation model are chosen and being tested analytically under influence of changing illumination level. The result are then compared with actual PV performance gained from the P-V curve supplied in manufacture data sheet to measure the degree of accuracy from each calculation procedure.
Estimating photovoltaic power output under various irradiance level
1. ESTIMATING PHOTOVOLTAIC POWER
OUTPUT UNDER VARIANCE OF
IRRADIANCE LEVEL
Haryo Agung Wibowo
Auckland University of Technology
Email: disiniharyo@yahoo.com
2. WHAT IS SOLAR ENERGY
• It is the largest sources of energy received on
Earth
• Solar is a renewable sources of energy
• Solar power would be a lot safer for the
environment and a lot better for the health
people
3. GENERATING ELECTRICITY
FROM SOLAR ENERGY
• Use semiconductor medium to convert sunlight
into electricity
Crystalline
Material
Thin Film Cell
Organic and
Polymer Cell
5. HOW DOES PV WORK?
• Photon of sunlight help excite an electron in
semiconductor crossing a higher conduction
band, leave electron – hole pair
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+
+
+
+
Electric Field
Load
6. HOW DOES PV WORK?
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• Junction with higher concentration of electron
become negative pole
• Electric field are created between positive and
negative junction
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+
+
+
Electric Field
Load
7. • If external pathway is provided, electron will be
swept away to the circuit. In macro view it was
appeared as electric current
HOW DOES PV WORK?
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+
+
+
+
+
Electric Field
Load
8. ADVANTAGES OF SOLAR PV SYSTEM
• It converts solar energy directly into electrical
energy without going through thermal-
mechanical link. It has no wear and tear part
• Solar PV system are reliable, modular, durable
and generally maintenance free
9. ADVANTAGES OF SOLAR PV SYSTEM
• These system are quiet, compatible with almost
all environments, expected life span for 20 years
or more
Snowy, High Altitude Site
Desert Climate
10. ADVANTAGES OF SOLAR PV SYSTEM
• It can be located at the place of use and hence no
distribution network is required
11. DISADVANTAGES OF SOLAR PV SYSTEM
• At present the cost of solar cell are still high,
making them economically uncompetitive with
other conventional power sources
$0.00
$1,000.00
$2,000.00
$3,000.00
$4,000.00
$5,000.00
Conventional Coal Combined Cycle
Gas Plant
Geothermal Nuclear Wind Solar
Price/kW
12. DISADVANTAGES OF SOLAR PV SYSTEM
• As solar energy produced only in the daylight time, an
energy storage is needed to make electricity available on
demand which make the whole system more expensive.
13. DISADVANTAGES OF SOLAR PV SYSTEM
• The efficiency of commercially available solar
cells are low
• Large number of solar cell area are required to
generate power on utilities scale
0%
10%
20%
30%
40%
Wind Turbine Monocrystalline Polycrsytalline Thin Film Polymer Cell
14. PROBLEM IDENTIFICATION
• How large the solar cell area is required to
deliver particular energy amount?
The answer depends on a number of locality
factor:
1. Solar irradiance
2.Temperature
3.Dust deposition density
4.Manufacture mismatch tolerances
5.Inverter efficiency
6.Spectral distribution
15. PRIMARY CONCERN
• To know how large does PV size should be, we
need to know exactly how does power output
behave as a function of solar irradiance
16. CAN IT AFFECT POWER OUTPUT?
• In engineering sense, yes
• As solar irradiance increase, the higher number
of photon hitting the modules.
• In micro view, it release greater number of
electron crossing the conduction band and
create more hole – electron pair
• Then higher electrical current and voltage will be
resulted
17. HOW TO QUANTIFY?
• We have to be familiar with:
1. Expected PV operating region
2. Typical manufacture product datasheet
18. PV OPERATING REGION
• PV current – voltage (I-V) curve is used a basis
to identify module circuit key parameter
Open Circuit Voltage
(Voc)
Short Circuit Current
(Isc)
19. PV OPERATING REGION
• To determine where the system will actually be
operating, we need to find common spot where the I-V
curve of the load and I-V curve of the PV intersect
Load I-V curve
System operating
point
21. PV OPERATING REGION
• We always expect to boost the power into the
maximum point
How to do that:
1. Control the PV or load or both I-
V curve simultaneously
2. Distribution network must be
able to absorb whatever amount
of the power being generated
22. PV OPERATING REGION
• Given that two condition is possibly met, make sense if
we want to push the operation of PV always satisfying
maximum power point (Pmp)
First Fact To Note:
Pmp is always varying dependent
on solar irradiance value
encountered by PV
25. DATA SHEET IN I-V CURVE
Isc
Voc
Vmp, Imp
1000 W/m2, 25⁰C,
1.5 AM
26. THE GAP
• Loosing large amount of information outlining PV maximum
power output characteristic under natural sunlight condition.
Truth Facts:
In Auckland, chance
of receiving
illumination at 990-
1010 W/m2 (STC)
are only less than
0.3% per year
That imply more
than 99% ,
irradiance will be
discovered outside
of that range
27. WHAT DO WE GET SO FAR?
• Accept that PV is always regulated to achieve
operation at maximum power point
• Know that manufacture will only provide PV
parameter based on STC rating
28. THE GAP
• Consequently, we do not know exactly how large the scale of
PV have to be implemented to meet minimum energy
demand.
• Without such essential information is available, sensibly the
most simple way to estimate the power output are using a
linearization approach.
• However, that is too risky, as this solution may produce some
degree of erroneous which affect the dimension overall system
become way too underrated or oversized
• Underrate -> expected energy outcome will never be realized
• Oversize -> the capital cost may no longer suggest PV had
competitive energy price as other renewable source
29. STUDY MOTIVATION
A guidance should be there to make engineer knowledgeable
about the way to use various simple approach for predicting
PV maximum power output within different irradiance value
• Not only that, they should also be advised about the degree of
error will be generated from each method compare to the real
PV output, so that necessary correction factor can be applied
accordingly to the overall PV design to obtain correct system
dimensioning.
30. RESEARCH GOAL
• Introduce various analytical method to predict
PV maximum power output under different
irradiance level using information suggested
under STC rating
• Test the calculation model and observe the
degree of accuracy compare to the information
provided by manufacture datasheet
• The PV product used as data sheet references is
Sharp PV ND-220E1J polycrystalline cell
31. STUDIED ANALYTICAL METHOD
• Six algebraic method to correct from STC to any
operating condition will be covered here:
1. Whitfield and Osterwald
2. Jones and Underwood
3. Araujo and Sanchez
4. Constant Efficiency Number
5. Constant Fill Factor
6. Variable Fill Factor
32. WHITFIELD AND OSTERWALD
• Due to lengthy formula should be completely
written on each analytical method, it is only
single formula will be presented here.
• One that pretty simple to use is:
max max*
2
1000 /
mG
P P
W m
33. VALIDATING THE METHODS
• Each model are then tested under 4 illumination level that is
referred to a standard laboratory test supplied by
manufacture (200, 400, 600, 800 W/m2)
34. VALIDATING THE METHODS
• The calculation result is compared to the extracted
manufacture PV output performance:
• And the deviation are measured using following equation:
35. VALIDATING THE METHODS
• The degree of erroneous between each method are presented
under following figure:
36. VALIDATING THE METHODS
• All method return good
result with <5% error
margin in the region close
to 800 W/m2
• As the irradiance drop,
deviation is amplified
• Whitfield and Osterwald,
Variable Fill Factor method
yield + 10% error when
400W/m2 is given as an
input
37. VALIDATING THE METHODS
• Best technique shown least
error (<10%) can be derived
from Araujo and Sanchez
method.
• The worst performance is
achieved by Variable Fill
Factor method because
variance of Voc are not
taken into account in the
formula
• It should be anticipated that
the error may become
worse as high as >10% at
irradiance <200 W/m2
38. ANOTHER FACTSHEET
• From New Zealand National Institute of Water and
Atmospheric Research (NIWA) statistic it is interestingly
revealed that around 82% global irradiance received in
Auckland was found by less than 400W/m2
. It is equivalent
with 32% of solar energy captured on PV surface every year.
• From that, the error prediction on PV annual energy
yield, calculated from constant efficiency/Whitfield &
Osterwald/ Variable Fill Factor method by not taking
appropriate error correction measure, is around
32% x 10% = 3.2%
39. SUMMARY
• Error cannot be avoided when predicting photovoltaic power
output using analytical method
• It has been shown that method proposed by Araujo and
Sanchez has a good proximity with real PV characteristic
represented in this case by Sharp ND-220E1J product
• To the existing available analytic method, the degree of
accuracy need to be improved particularly for prediction PV
power output under low irradiance regime