International Journal of Applied Engineering Research ISSN 0973-4562 Volume 11, Number 14 (2016) pp 8113-8116
© Research India Publications. http://www.ripublication.com
Demonstration Study on Standalone PV System for Solar Desalination in
Korea
Byunggyu Yu
Division of Electrical, Electronic & Control Engineering, Kongju National University,
1223-24, Cheonan Daero, Seobuk-gu, Cheonan-si, Chungnam, 31080, Korea.
In this research project, to develop the application system for
practical use of fresh water generation system with
evaporation method is the main object using the evacuated
solar collector with operating range of about 80-90[℃] as
thermal system and solar photovoltaic system as electric
supply system.
As one of the project targets, this paper presents
demonstration study on stand-alone PV system for solar
desalination facility with plate-type heat exchanger. This
paper focuses on design and experimental results of the
photovoltaic generation system to supply electric power for
solar desalination system including batter bank, power
conditioning system, solar tracker, and emergency backup
system.
Abstract
This paper presents demonstration study on stand-alone PV
system for solar desalination facility with plate-type heat
exchanger. Most of the electricity required in the solar
desalination facility is supplied by a photovoltaic power
generation system made up of 30 single crystalline silicon
modules each 0.792 m wide by 1.583 m long, producing a
total of 5.2[kW]. The installed photovoltaic system uses the
tracker to have more generated power and the battery storage
bank to restore the remained power from PV after the pumps
consumed. Based on the similar pattern between the PV
power generation and electric load in the study, the battery
bank can be optimized. Pump-controlling inverters connected
to the photovoltaic system automatically start up the
desalination system according to the amount of solar radiation
available and runs the pumps by controlling the output of the
photovoltaic system. Fresh water production varies with the
solar radiation. The test plant in this study has produced fresh
water 500 liters/day, on average. It was shown that the
Photovoltaic power generation system supplies enough
electric power for the stable solar desalination process, even
with considerable fluctuations in the irradiation. This solar
desalination system is expected to be used in isolated islands,
remote area, and desert districts where water shortages are
severe. For further research, the battery bank will be
optimized by the experimental parameter with a stable
desalination performance in order to lower the system cost
and the total electric system for solar desalination can be
removed every night by using a timer in order to save the
standby power loss.
SYSTEM DESCRIPTION
As shown in Figure 1, the hot water using evacuated solar
collector would supply as heating medium for sea water
needed to be evaporated and the PV system would supply the
electricity to activate the working fluids. That system is
integrated by the solar collector, PV system, and evaporation
type of fresh water generation system. It is remarkable that the
pattern of PV generation is similar with that of pump load for
desalination.
Keywords: solar desalination, stand-alone, PV system
INTRODUCTION
Water is not always available in the quantity and quality
where it is needed for specific purposes. A third of people in
the world based on UN environmental report have suffered
with the water lack and Korea is also known as one of the
countries with water lack problem. Until now, various
desalination systems have been studied.[1-7] As reported in
the running report of domestic management for sea water
desalination system, there are some problems including the
operation by town manager without professional knowledge,
out of order of membrane for pre-filtering of sea water, and
difficult repairs of RO(Reverse Osmosis) components and
high pressure pumps to operate [7-10]. 29 systems of all 40
sea water desalination systems installed have normally
operated in Korea.
Figure 1: System overview of solar desalination
DESIGN CONSIDERATION
As Table 1, the actual pump electric load is equal to 2.3[kW].
Since the 2.3[kW] nominal load period is around 8 hour
throughout the year, the daily consumed load energy is
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International Journal of Applied Engineering Research ISSN 0973-4562 Volume 11, Number 14 (2016) pp 8113-8116
© Research India Publications. http://www.ripublication.com
determined as Equation (1) with battery discharging
coefficient (K1) and inverter efficiency (K2).
𝑃𝐿𝑜𝑎𝑑 × 𝑇1
2.3 × 8
𝑊𝐿𝑜𝑎𝑑 =
=
= 22.72[𝑘𝑊ℎ/𝑑𝑎𝑦]
𝐾1 × 𝐾2
0.9 × 0.9
(1)
The required PV array capacity is also determined with the
averaging irradiance duration 4.5hour as shown Equation (2).
Usually, the averaging irradiance duration is 3.5hour in Korea,
but the duration of a tracking PV system can increase up to
around 30% higher.
Table 1: Load specification of the installed PV system
Motor #1 [kW] Motor #2[kW] Total [kW]
Motor #3 [kW]
Nominal Power
0.75
1.5
2.3
0.8
Figure 2: PV system block diagram
For the stated desalination system, the 5.2 [kW] stand-alone
PV system is installed in Jeju Island as shown in Figure 3. The
PV tracking system is used to increase the generated power,
which is operated by insolation database program and is
controlled to two axes. As shown in Figure 4, both motor #1
and motor #2 have the spare pump motor for emergency.
Figure 5 shows the constructed 5kW PV inverter.
Table 2: Component specifications of the installed PV system
Electrical Specification
PV module
Nominal power [W]
(SE-173S)
MPP voltage [V]
MPP current [A]
(# of series) * # (of parallel)
PV inverter
Type
(T001)
Rated AC output power [kW]
Efficiency [%]
Battery
Rated voltage [V]
(SP2000)
Capacity [Ah]
(# of series) * # (of parallel)
𝑃𝑎𝑟𝑟𝑎𝑦 =
Value
173
37.0
4.67
10 * 3
stand-alone
5
90% or more
12
200
16 * 2
𝑊𝐿𝑜𝑎𝑑
= 5.05 [𝑘𝑊]
𝑇2
(2)
To meet the required PV array capacity, 173[W] PV module is
used by 10 series and 3 parallel as Table 2. As a result, the
designed PV array power is around 5.2[kW].
For 2 days battery backup operation, the designed battery
capacity is around 75.73[kWh] by Equation (3).
22.72[𝑘𝑊ℎ/𝑑𝑎𝑦] × 2[𝑑𝑎𝑦]
𝐴ℎ =
= 75.73 [𝑘𝑊]
0.6
(3)
As shown in Table 2, the battery as 12V/200[Ah] is connected
by 16 series and 2 parallel, which generates 76.8[kWh].
With this design process, the PV system is constructed as
Figure2. If the pump doesn’t operate correctly due to PV
system breakdown, the grid will drive the power to the pump
in order to prevent the solar thermal panel damage. In the real
stand-alone PV system, the grid replaced by diesel-generator
is optional as a backup system with concrete battery storage.
Figure 3: Installed 5.2kW PV tracker
Figure 4: Installed motor #1 and motor # 2 (pair for
emergency)
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International Journal of Applied Engineering Research ISSN 0973-4562 Volume 11, Number 14 (2016) pp 8113-8116
© Research India Publications. http://www.ripublication.com
Figure7: Main measured data for 3 month
Figure 5: 5kW PV inverter
PERFORMANCE RESULTS OF PV SYSTEM
Figure6 shows the web-based monitoring display. Therefore,
the standalone PV system can be monitored remotely and
checked the stored database. Every 4 second, some main parts
of the measured data including irradiance, temperature, power
generation, and power consumption are displayed. In case of
the stored database, the main data are stored every 10 minutes
by averaging.
Figure7 and Figure8 show the PV generation, the consumed
load energy, and battery charging/discharging energy. From
this measured data, the PV generation is enough to supply the
electric power to the desalination system. Actually, it is clear
that both pattern of PV generation and that of motor power
consumption have the very similar each other.
Figure 8 shows the PV performance data on a sunny day.
However, this system specification has some defect that there
is always power consumption of standby loss around 400W
from battery storage bank throughout the night. This problem
could be solved by the cut off the PV system during every
night by using electronic timer.
Figure 8: PV system performance during a sunny day
CONCLUSION
In the research project, to develop the application system for
practical use of fresh water generation system with
evaporation method is the main object using the evacuated
solar collector with operating range of about 80-90℃ as
thermal system and solar photovoltaic system as electric
supply system.
As one of the project targets, this paper presents
demonstration study on stand-alone PV system for solar
desalination facility with plate-type heat exchanger. This
paper focuses on design and experimental results of the
photovoltaic generation system to supply electric power for
solar desalination system including batter bank, power
conditioning system, solar tracker, and emergency backup
system. As a result, this stand-alone PV system shows the
good performance of electric power supply by the similar
generation-load pattern.
ACKNOWLEDGEMENTS
This work was supported by the research grant of the Kongju
National University in 2015
Figure 6: Web-based remote monitoring system
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International Journal of Applied Engineering Research ISSN 0973-4562 Volume 11, Number 14 (2016) pp 8113-8116
© Research India Publications. http://www.ripublication.com
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