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Open Journal of Energy Efficiency, 2015, 4, 45-52
Published Online September 2015 in SciRes. http://www.scirp.org/journal/ojee
http://dx.doi.org/10.4236/ojee.2015.43005
How to cite this paper: Lin, C.-L. (2015) Case Study of Solar Power Producing Efficiency from a Photovoltaic System. Open
Journal of Energy Efficiency, 4, 45-52. http://dx.doi.org/10.4236/ojee.2015.43005
Case Study of Solar Power Producing
Efficiency from a Photovoltaic System
Ching-Lung Lin
Department of Electrical Engineering, Mingshin University of Science and Technology, Hsin-Chu, Taiwan
Email: cll@must.edu.tw
Received 24 June 2015; accepted 21 August 2015; published 24 August 2015
Copyright © 2015 by author and Scientific Research Publishing Inc.
This work is licensed under the Creative Commons Attribution International License (CC BY).
http://creativecommons.org/licenses/by/4.0/
Abstract
To study the efficiency increasing of electric energy generation in the Photovoltaic System is con-
centrated on this paper. There are four cases to improve the efficiency of power producing from
the Photovoltaic System. This article not only describes the differences of facilities before and af-
ter the proposal, but also evaluates the electric energy generation efficiency and improved results
for each proposal. Finally, the better efficiency of all improving ways is analyzed to get into con-
clusions in order to provide further improvement and reference for the industry in the future.
Overall, these proposed methods can improve the efficiency of solar photovoltaic electric energy
generation in about 30.18%.
Keywords
Solar Cell, Photovoltaic, Tracking Device, Inverter
1. Introduction
Sun is a completely unpolluted natural resource, and sunshine illuminates all over the world. It is a sustainable
energy resource which cannot be monopolized. Each year, the quantity of solar energy irradiating on the earth is
more than the need of human consumption. If it is possible to convert this huge and unpolluted energy for ap-
plication, then the problem in the shortage of energy for human can be solved. In current regenerated energy re-
sources, photovoltaic is the best technique developed so far and is the most potential energy resource. Photoe-
lectric effect is to pass solar energy through solar-cell to transfer it into electric power. This kind of photo-
electric transformation is mainly with the help of photoelectric effect of semiconductor elements to proceed. It is
applied to supply power to space station, artificial satellite, and remote area. It is also used to setup solar power
plant and merge into power generation [1]-[3].
C.-L. Lin
46
2. Generation of Photovoltaic System
The power production device involved is the solar cell. Modules and consequently arrays are made by series and
parallel connection of such solar cells. This solar cell is a p-n junction diode that converts light energy from the
sun into electrical energy. The current and voltage thus produced have a non-linear relationship. The power thus
available from a solar cell peaks at a particular operating voltage. This peak power and the corresponding oper-
ating voltage keep varying with changing insolation and temperature conditions [4].
2.1. Operational Theorem of Solar-Cell
Electrons of p-type semiconductor and positive electric charges of n-type semiconductor are attracted with each
other. The blocking layer is formed in the positive-negative neutralized area at the p-n junction. If there is light
illuminating on the p-n junction, free electron will be excited and flowed into n-type semiconductor while posi-
tive electric charge is moved to p-type semiconductor. Furthermore, electric potential force is produced. If it is
connected with load, then there will be electric current moving on it. In simplicity, the theorem of generating
electric power from photovoltaic is to utilize the solar-cell to directly transform photo energy into the other kind
of electric energy by absorbing ultraviolet rays with 0.2 - 0.39 μm wavelength. The operational theorem of a so-
lar-cell is shown as Figure 1.
Solar power is a kind of free and unlimited resource on earth which would not waste our natural resources
pollutes our environment and cause to greenhouse effect. Photovoltaic module must accept any strict outdoor
environment in the world. Otherwise, the life of this product is also the longest in the world, over 25 years. Due
to the world values of protecting the environment, solar industry is developing rapidly and becoming popular.
Figure 2 shows the fundamental solar power generation structure of photovoltaic system.
2.2. Comparison of Solar Cell
The materials of commercial solar cells, they can be classified into following types: Single Crystal Silicon, Po-
lycrystal Silicon, Amorphous Silicon, GaAs, InP, CdS, CdTe, CuInse, CuInGaSe and currently researching
Dye-Sensitized Nanocrystalline Solar Cell [5] and Organic Solar Cell and so on as indicated in Table 1. The
Figure 1. Operational theorem of a solar-cell.
Figure 2. Shows the fundamental solar power generation struc-
ture of photovoltaic system.
C.-L. Lin
47
Table 1. Comparison of solar cell.
Sorts of solar cells Materials of semiconductor Transforming efficiency
Silicon
Crystalline
Single crystallin 12% - 20%
Poly crystallin 10% - 18%
Amorphous Si, SiC, SiGe, SiH, SiO 6% - 9%
Compound
Single crystallin GaAs, InP 18% - 30%
Poly crystallin CdS, CdTe, CuIns, CuInGaSe 10% - 12%
Nano and organic TiO
2
/Dye 1% and under
Data resources: solarpv.itri.org.tw, Green Energy and Environment Research Laboratories of Industrial Technology Research Institute (ITRI).
developed technique of Silicon Crystalline Solar-cell is more mature than others. Its efficiency of power genera-
tion is also perfectly stable. It always is the main force of solar cells. On one occasion, since the price of Silicon
material is raising the other PC techniques likes membrane types have chances to scurry. The merit of the mem-
brane type lies in being able to combine with glass building materials. This will make it to become the large
scale membrane-type solar-cell and also be able to absorb sunlight from different angles. Unlike the silicon
crystalline type, it must face south to setup the best angle in Taiwan. However, the efficiency of power genera-
tion in the membrane type is not as good as the silicon crystalline type, and there are many technical problems
needed to be conquered. Therefore, actual applications are still mainly used the silicon crystalline type solar
cells.
3. Structure of Photovoltaic System
In this case, the photovoltaic system has been installed at Pingtung district, Taiwan. The plane configuration of
the system is indicated in Figure 3. Equipments include: solar-cell arrays, the extended-height type of the mod-
ule supported frame, junction boxes of direct current, Inverters, switch boxes of alternating current, voltage
step-up transformers, high-voltage distributors, the wholesale electric meter and so on. The array of solar-cell
modules (or referred to as the solar panel) should be put up on the 3.2-meter rack to face south with 10 degrees
of the angle of elevation. Total capacities of electric power production is 403.26 kW (1716 slices of solar-cell
module × 235 Watt/slice). According to the regulation of Item III Rule (2) in “Technique Essentials for Merging
the Power Generating System of Renewable Energy with Taiwan Power Company (Taipower)”, the power ge-
nerating equipment with total capacity between 100 kW and 10,000 kW should be transfer to 11.4 kV high-
voltage feeding system of Taipower.
The ways of setting up this photovoltaic system and its environmental conditions are as followings: the solar-
cell arrays are arranged from North to South as the first row (PV-1-PV-4) and the fourth row (PV-13-PV-17).
The transformer station of the photovoltaic system is set up as indicated in Figure 4.
The block diagram of the solar-cell array, transformers, and the circuits of protection device is described in
Figure 5. It escaped time can be coordinated with the Taipower.
4. Improved Cases for Increasing Energy Efficiency
The power production efficiency of solar cell is about 13% to 17%. Therefore, this paper suggests four cases to
improve and increase the efficiency of power generation from the photovoltaic system.
4.1. Increasing the Efficiency from the Amorphous Transformer
The amorphous transformer has characteristics which are low iron loss and low noise, this system changes the
500 kVA traditional high-efficient transformer of the original design to an amorphous, low iron loss and ultra-
high-efficient transformer. The iron loss of the originally adopted traditional high-efficient transformer is 1026
W, however, the iron loss of the amorphous, low iron loss and ultrahigh-efficient transformer is only 220 W.
Calculating the wastage power (iron loss) of the traditional high-efficient transformer is as follows:
C.-L. Lin
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Figure 3. Power plane configuration of the photovoltaic system.
Figure 4. The transformer station in the photovoltaic system.
Figure 5. Block diagram of the solar-cell array, transformer and protection device.
TPCC.
MOF
kWH
Y -Δ
500 kV
34 W
22.8 - 11.4 kV
/380 – 220 V
GCB
24 kV
630 A
Digital
Meter
AC SPD
Indicator
No Fuse
Breaker
Solar-Cell Array:
Total 403.26 kW
Single-chip solar
cell with 235 W
96 sets of 16
chips in serial +
12 sets
of 15 chip in
serial. Totally,
1716 chip
installed,
(16 × 6 × 16 +
15 × 6 × 2)
DC
AC
Data
Collector
PC
C.-L. Lin
49
1026 W 24 Hrs 365 days 8987.76 kWH year.×× ≒
(1)
However, the wastage power (iron loss) of the amorphous, low iron loss and ultrahigh-efficient transformer is:
220 W 24 Hrs 365 days 1927.2 kWH year.×× ≒
(2)
Using the amorphous transformer, the saving amount of wastage power from iron losses for each year totally
is:
( )
1026 220 W 24 Hrs 365 days 7061kWH year.− ×× ≒
(3)
The year average quantity of power generation set up by this system is 647,636 kWH/year, and which is cal-
culated as:
403.26 kW 4.4 Hrs 365 days 647636 kWH year.×× ≒
(4)
The improved efficiency increased by using the amorphous transformer is:
7061kWH 647636 kWH 100% 1.1%.× ≒
(5)
4.2. Increasing the Efficiency by Uninstalling the Anti-Reverse Diode
Advantages of uninstalling the anti-reverse diodes are:
1) Solves the heat-radiating problem while diodes are functioning with giving out heat;
2) Avoids small animals to come to warm themselves and to cause the short-circuit problem;
3) Decreases the wastage of promoting the efficiency of power generation from photovoltaic.
This system is originally installed with 96 anti-reverse diodes. If the quantity of daily equivalent sunshine is
estimated to be 4.4 hours, then the wasting power reduced daily by removing the anti-reverse diodes is:
( )
0.7 V 7 A average 4.4 Hrs 96 2069.8 WH day.× × ×=
(6)
Wasting power by a year is:
2.07 kWH day 365 days 755.5 kWH year.
× ≒
(7)
The year average quantity of power generation set up by this system is 647,636 kWH/year indicated in Equa-
tion (4). The improved efficiency increased by uninstalling the anti-reverse diode is 0.1%. This is shown as fol-
lows:
( )
755.5 kWH 647636 kWH 100% 0.1%.× ≒
(8)
4.3. Increasing the Efficiency by a Sprinkling Water
The geographic location of Taiwan is belonged to the subtropical zone. Especially, Taiwan is full of sunshine,
though the temperature is very high. The environmental condition is very suitable to develop photovoltaic ener-
gy. Consequently as long as we improve the construction of PV system, increase height of the PV construction,
support very large space to get very adequate airflow, and the temperature of PV modules could be kept at about
55˚C. The distance from PV modules to ground must be 3 meters high at least. We can have infinite future of
developing Photovoltaic System [5].
In the way of choosing the cooling system for the photovoltaic system, not only increasing economic effi-
ciency of power production, but also getting higher interest rate to make more income and reduce your invest-
ment during. The more intensity of sunshine is the more quantity of power generation from PV system. Since
the solar-cell module is with the property of negative temperature coefficient, as the temperature of the module
is rising, the efficiency of power generation is decreasing gradually [6]-[9]. For this reason, this study estab-
lished the Cooling System by Sprinkling Water on May, 2011 to reduce the temperature of modules. Because
dust and squalidness on the surface of solar cells are also factors of affecting the efficiency of power generation,
establishing the water-sprinkling system can reduce the temperature of modules and can clean surfaces of panels
as well to increase the efficiency of power generation.
According to “Planning Method and Life-Cycle Cost Analysis for Large-Scale Photovoltaic System” [10], it
provides the average temperature on the back side of the module for each month in Taiwan. The obtained power
results are estimated and shown in Table 2.
C.-L. Lin
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Table 2. Average temperature on the back side of the module and power results for each month in Taiwan.
Monthly section Month 1, 2 Month 3, 11, 12 Month 4, 5 Month 6-8 Month 9, 10
Module back temperature (MBT) 40˚C 50˚C 55˚C 65˚C 60˚C
Low down temperature to 40˚C to reduce power loss 0 4% 6.06% 10.09% 8.08%
Estimation of obtained power results 0 0.12 P
40˚C
0.12 P
40˚C
0.3 P
40˚C
0.16 P
40˚C
Usually, the practical operation is to sprinkle water until the temperature is rising to the highest point. When it
is down to 40˚C, then stop sprinkling water. Therefore, the efficiency can be increase to 5.8%/2 = 2.9% by using
the theory of calculating the triangle area.
4.4. Increasing the Efficiency by a Tracking System
The tracking device for solar cell with a sensor which is composed of four photo-resistors surrounding a sun-
shade to represent east, west, south and north. The resistance of photo-resistor will vary under solar irradiance
such that the position of the sun can be determined by comparing circuit based on which the AC motor can be
driven to allow perpendicular incident angle of sunlight onto the solar cell. This way the solar illumination can
be improved and power generation efficiency can be enhanced. The tracking system is shown as Figure 6 [11]
[12].
There are two solar cell testing devices to receive illumination data in the same testing environment. Table 3
shows that the non-tracking illumination data received from the solar cell. Table 4 shows the tracking illumina-
tion data received from another solar cell. The data were recorded from 6 am to 17 pm, from morning to evening.
The solar photovoltaic system with a tracking device, the solar illumination can be improved and power genera-
tion efficiency can be enhanced. When the solar illumination on solar cell was improved, that the solar voltage
(v) and the solar current (A) values also to be increased. So, the total power producing efficiency is getting
higher. According to the dada from Table 3 and Table 4, the record date of solar cell, the power producing is
accumulated during sunshine time. The daily improving power producing is calculated by Equation (9). (Ex-
clude the power used of the tracking device).
( ) ( )
17
improved
6
non-tracking
tracking
Vbatt Ichag Vbatt Ichag W.
ii ii
i
E
=
= ∗ −∗
∑
(9)
Experiment results show that the proposed all weather tracking device improves the tracking operation preci-
sion and reliability of solar power generation system, improves the photovoltaic system transformation efficien-
cy [12]. Figure 7 shows the data comparison of two solar photovoltaic systems.
The increasing power producing is shown at the bottom line of Table 3 and Table 4. The energy generation
efficiency is increased 26.08% every day, shown as Equation (10).
( )
26.08% 280.05 W 222.12 W 222.12 W 100%.
=−∗
(10)
Although the tracking device of solar photovoltaic system increases 26.08% of energy generation efficiency,
it must base on a shining day. If it is a windy day, the tracking device must be stop. The wind will damage the
tracking device.
5. Conclusions
The geographic location of Taiwan is belonged to the subtropical zone. Especially, the south district of Taiwan
is full of sunshine. The environmental condition is very suitable to develop photovoltaic. Consequently, as long
as we improve moreover on the utilizing technology of solar energy, we can have infinite future of developing
photovoltaic.
Cases adopted by this study to improve and increase the efficiency of power producing from the photovoltaic
system are listed in the followings:
1) Use the amorphous transformer—The improved efficiency increased 1.1%.
2) Remove the anti-reverse diode—The improved efficiency increased 0.1%.
3) Establish the cooling system by sprinkling water—The improved efficiency increased 2.9%.
4) Solar cell with a tracking device—The improved efficiency increased 26.08%.
C.-L. Lin
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Figure 6. The tracking device for a solar cell.
Figure 7. The data comparison of two solar photovoltaic systems.
Table 3. The power producing from the non-tracking solar photovoltaic system.
Time Non-tracking illumination Vpv (V) Vbatt. (V) Ichag (A) Pnon-tracking (W)
6 11.46 14.27 13.66 0.32 4.37
7 25.56 14.86 13.7 0.65 8.91
8 42.4 15.26 13.82 1.31 18.10
9 62.5 15.42 14.29 1.55 22.15
10 70.97 16.15 14.82 1.65 24.45
11 79.11 16.15 14.86 1.74 25.86
12 82.36 16.82 14.92 1.84 27.45
13 77.23 15.76 14.35 1.84 26.40
14 65.05 16.36 14.82 1.71 25.34
15 49.28 16.08 14.72 1.34 19.72
16 30.98 15.9 14.65 1.02 14.94
17 13.37 14.72 13.78 0.32 4.41
Total power producing from non-tracking device (W): 222.12
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Table 4. The power producing from the tracking solar photovoltaic system.
Time Tracking illumination Vpv (V) Vbatt. (V) Ichag (A) Ptracking (W)
6 42.45 15.07 13.77 1.25 17.21
7 48.77 15.23 13.84 1.38 19.10
8 54.27 15.36 14.02 1.48 20.75
9 68.47 15.96 14.44 1.67 24.11
10 75.55 16.33 14.86 1.74 25.86
11 80.97 16.31 14.93 1.8 26.87
12 84.42 16.88 15.11 1.85 27.95
13 81.96 16.1 14.76 1.86 27.45
14 74.1 16.16 14.72 1.76 25.91
15 71.66 16.43 14.99 1.63 24.43
16 66.33 16.27 14.84 1.52 22.56
17 44.06 15.98 14.74 1.21 17.84
Total power producing from tracking device (W): 280.05
Four improving cases of power producing from the photovoltaic system of this study totally increased the ef-
ficiency to around 30.18%. This is obviously increasing the transforming efficiency for the power generation
from photovoltaic, but the result of the solar cell with a tracking device must depend on the weather.
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