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TECHNO ECONOMIC ANALYSIS OF
ON GRID PV SYSTEM IN
AN NAJAH UNIVERSITY HOSPITAL
SUPERVISED BY:
DR. EMAD BREIK
HIBA ABU ISSA
BARA’A SURAKJI
2012-2013
DANIA ALABED
INTRODUCTION
In recent years, there has been a huge worldwide
movement to use renewable energy in both
residential and commercial uses. And the solar
energy is the most important source.
We need to point the renewable energy sources
that our country Palestine have Authority strategy
in Palestine predicts that by 2020, 10 % of our total
consumption will be from renewable source.
And this is the reason why we choose this topic to
be our graduation project.
PHOTOVOLTAIC BACKGROUND
Photovoltaic system is comprised of photovoltaic
cells, devices that convert light energy directly into
electricity.
The word photovoltaic comes from “photo”
meaning light, and “voltaic” which refers to
producing electricity. Therefore, the photovoltaic
process is “producing electricity directly from
sunlight”.
Photovoltaic are often referred to as PV.
HOW PV CELL WORK
PVcells are made of at least two
layers of semiconductor material.
One layer has a positive charge,
the other’s negative. When light
enters the cell, some of the
photons from light are absorbed by
the
semiconductor
atoms
freeing electrons from the cell’s
negative layer to flow through
an external circuit and back into
the positive layer. This flow of
electrons
produces
electric
current.
HOW PV CELL WORK
TYPES OF PV CELLS

Single Crystalline

Polycrystalline or Multicrystalline

String Ribbon

Amorphous or Thin Film
The most efficient sunlight conversion technology available about 10% to 12%.
Module efficiency about 10% to 11%.
Module efficiency about 7% to 8%.
Module efficiency about 5% to 7%.
THEORY OF I-V CHARACTERIZATION
PV cells can be modeled as a current source in parallel with a
diode. When there is no light present to generate any current,
the PV cell behaves like a diode. As the intensity of incident
light increases, current is generated by the PV cell, as
illustrated in following Figure :
STANDARD TEST CONDITION
Standard Test Conditions (STC) they are:

Cell temperature is 25 oC .
Solar irradiance (intensity) = 1000 W/m2 (often
referred to as peak sunlight intensity, comparable
to clear summer noon time intensity).

Solar spectrum as filtered by passing through 1.5
thickness of atmosphere .

FACTORS AFFECTING MODULE OUTPUT POWER

Temperature & irradiance.
FACTORS AFFECTING MODULE OUTPUT POWER

Mismatch and wiring losses.
Module mismatch.
 Power lost in resistance in the wiring system.
These losses should be kept to the minimum.




DC to AC conversion losses.
Some power is lost in the conversion process.
Additional losses in the wires from the Roof top array down to
the inverter and out to the house panel.
PHOTOVOLTAIC SYSTEMS TYPES
PHOTOVOLTAIC SYSTEM TYPES

Grid tied system

Off Grid system
OFF GRID SYSTEM TYPES
It is the most common in remote locations without
utility grid service, off grid solar electric systems can
work anywhere.
They are generally designed and sized to supply
DC and/or AC electrical load.
1. DIRECT COUPLED SYSTEM
Drawbacks in this type are:
It can only be used in the day to supply load as there is no
battery for storing energy.
 It can not be used with AC load .

2. OFF GRID SYSTEM WITH INVERTER
In this type we use an inverter to convert voltage
from DC to AC at appropriate voltage level.
Drawback in this type is:

The lack of storage unit, so it will not supply load at night.
3. OFF-GRID SYSTEM WITH BATTERY WITH DC OUTPUT
The problem of no electricity generation in the night is
eliminated with the inclusion of storage unit (batteries) as
backup energy in the night.
4. OFF-GRID SYSTEM WITH BATTERY WITHOUT DC OUTPUT
5. OFF GRID SYSTEM WITH ENGINE GENERATOR
GRID TIED SYSTEM TYPES (ON GRID SYSTEM)
Grid tied systems are designed to operate in parallel with and
interconnected with the electric utility grid.
Grid tied system with no battery
for storing energy.
Grid tied system with batteries
for storing energy.
GRID TIED VS. OFF GRID SYSTEMS
Grid tied advantages:



There is no need for a battery system to store the energy.
Less expensive than off grid systems (less equipment and
less time to install and require very little maintenances).
More efficient and environmentally friendly.
Off grid advantages:



When we have no grid, there may be no option other than
to go with an off grid system.
Although it requires more care and maintenance, but it
can give the homeowner a strong sense of independence.
Homeowner is no longer subject to the risk of a loss of
power from the grid.
GRID TIE INVERTER (GTI)
It is a special type of power inverter that converts from DC to
AC and feeds it into an existing electrical grid.
Properties of Tie inverter:


The technical name for a grid tie inverter is "grid interactive
inverter". typically it cannot be used in standalone
applications where utility power is not available.
During a period of over production from the generating
source, power is routed into the power grid, there by being
sold to the local power company. During insufficient power
production, it allows for power to be purchased from the
power company.
GRID TIE INVERTER (GTI)




It must synchronize its frequency with that of the grid and
limit the voltage to no higher than the grid voltage.
GTI has a fixed unity power factor, which means its output
voltage and current are perfectly lined up.
It has an on board computer which will sense the current
AC grid waveform, and output a voltage to correspond
with the grid.
It also designed to disconnect quickly from the grid if the
utility grid goes down.
OFF GRID INVERTERS
always work in a system that uses batteries, but
sometimes they work with generators too. Some
inverters can charge the batteries with the extra
energy from a generator.
COMPONENTS OF ON GRID
SYSTEM
COMPONENT OF ON GRID PV SYSTEM

PV array
A PV array is the complete power-generating unit,
Dc-Ac inverter
 Combiner Box

It gathers all the solar panel connections at one location,
providing a neat, clean looking installation.

Metering
This includes meters that provide indication of system
performance. Some meters can indicate energy usage.

other components
In most cases, the grid will require a transformer to step up
the voltage from the solar inverter to be connected to the
grid.
COMPONENT OF ON GRID PV SYSTEM

Balance of system equipment (BOS)
The BOS equipment that used to integrate the solar modules
into the structural and electrical systems of the home are:

Mounting systems.
Solar panel mount They are important to provide proper directional and
latitudinal orientation, maximize production, and to provide the stability
needed to protect your investment.
 A solar tracker is a device for orienting a solar panel or solar array
toward the sun.


Wiring systems, which include:
Disconnects for the dc and ac sides of the inverter.
 Ground fault protection, and overcurrent protection for the solar
modules.
 Fuses for each module source circuit.

DESIGNING THE PV IN AN
NAJAH HOSPITAL
Our project is going to use PV system to generates
electricity to feed An-Najah University Hospital.
The Hospital intends install solar cells and connect
them with the grid lines of the Northern Electricity
Distribution Company.
According to the financial possibilities that are
available for the University , they decided to install
a 100 kwp PV system.
The Energy Authority in Palestine tracking a feed in
tariff policy In which the government buys one
kilowatt that has been generated from a solar cell
for 1.07 Nis, this price is set by PERC (Palestine
electrical regulator council), as it is known, the price
of one kilowatt we buy from the Northern Electricity
Distribution Company is 0.55 Nis.
CHOOSING THE ELEMENTS OF THE PV SYSTEM
In this research we will display our calculation that show:






Number of modules & inverters that are needed for this
size of PV system.
The suitable fuse that we can used to protect module
circuit (Dc side).
The suitable cables that are needed for connection
between module circuit and a junction box, at the same
way we choose a suitable cables are needed for
connection between junction box and inverters.
In order to protect an AC side we choose the circuit
breakers that are needed for our PV system.
And after of all we’ve calculated the space area that is
needed to install 100 kwp PV system.
We’ve also designed calculator that help us sizing any ON
Grid system.
CHOOSING THE ELEMENTS OF THE PV SYSTEM

Select the type of PV module
We’ve used a Kyocera 140watt module.


Number of modules we need
100 kw / 140w = 714 module.
From the data sheet of this module we have:
Pmax = 140 watt
Vmpp = 17.7 V
Impp = 7.91 A
Voc = 22.1 V
Isc
= 8.68 A
Max system DC volt = 600V
CHOOSING THE ELEMENTS OF THE PV SYSTEM



We need 384 DC volt (this value must be in the range of
inverter‘s dc voltage).
Number of modules in series = system Dc volt / module Vmmp
384 / 17.7 = 22 modules.
Number of modules in parallel
714 / 22 = 33 modules.
CHOOSING THE ELEMENTS OF THE PV SYSTEM

Select the inverter (DC/AC)
In our project we’ve used a 10 kw MAC inverter
From the data sheet, the DC volt range for this inverter is (250800) volt.



S inverters ≥ 1.1 Ppv peak
So we will need a 110 kw tie inverters
Number of inverters
110kw / 10k = 11 inverters
Number of Modules are connected to each inverter
22 * 33 /11 = 22 * 3 modules
CHOOSING THE ELEMENTS OF THE PV SYSTEM

Cables, protection device & earthing system
Modules require fusing for each module source circuit.
In order to have a successful design we must achieve the
following relationship
Irated fuse ≥ 1.25 Isc for module
The 140 watt module have a 8.86 A short circuit current So
we use a 15 A fuse for each module circuit.
The cross sectional area for wire must be chosen according
to this relationship
Irated cable ≥ Irated for fuse
CHOOSING THE ELEMENTS OF THE PV SYSTEM
The suitable cable that is connected between junction box
and inverter will be D 3-XLPE 16 mm2 cross sectional area.
Now we select the C.B to protect the AC side
ICB ≥ 1.25 * #of string of module * Isc for each module
Icable ≥ ICB
We’ve selected a 50 A C.B to protect the AC side of inverter
& the suitable cables that connect between inverter and main
power supply will be D 3-XLPE 10 mm2.
THE ELEMENTS OF THE PV SYSTEM
AREA CALCULATION OF PV ARRAY

Dimensions of Kyocera module
Length = 150.144 cm
Width = 66.802 cm
Depth = 4.572 cm

In Palestine the array of PV solar system placed
diagonally at an angle 32 in degrees.
AREA CALCULATION OF PV ARRAY
PV CALCULATOR
PV SYSTEM CALCULATOR


We designed a calculator that it
help us to calculate the suitable
elements for any on grid system.
The flow chart of the calculator
PV SYSTEM CALCULATOR
PV SYSTEM CALCULATOR

The following images show the module type that we used in
our program and the inverter type.
PV SYSTEM CALCULATOR


After entering the PV System size in kw and DC volt system the
program ask to choose a module and inverter that you want to use
in PV system.
When you choose them, the data sheet will be displayed in the left
side of the window.
OUR NEXT STEP




Actual design on the roof of the hospital (location).
The Connection of the PV system with the grid (cables,
transformers, protective devices).
Software Economical evaluation (calculating the total
income from the PV system).
Environmental impact.
TECHNICAL ANALYSIS OF
INTEGRATION OF PV SYSTEM
Integration of PV systems with distribution networks
could bring a number of benefits as well as technical
issues.

The benefits could be the reduction in maximum
demand charge and energy losses. However, it
creates voltage rise issues.

After we analyze the quality of supply that’s come
from NEDCO company we take a LV network of AnNajah University Hospital , then we take another
residential network to show the impact of PV system
on networks.

NAJAH UNIVERSITY HOSPITAL DISTRIBUTION NETWORK
(SUGGESTION PROJECT)
This network supplies An-Najah University Hospital with a
length of 200 m and 400 kVA transformer.
This network consists of 3 phase loads , 3 distribution
lines.
The load related to the hospital is 274KVA.
The parameters of the cable and transformers are :
Type of equipment or
cable
400 KVA transformer
Resistance(at 50 Hz)
Reactance(at 50Hz)
x/r = 3.09
Z% = 4
Cable (95 mm2)
.273 ohm/km
.330 ohm/km


For the photovoltaic system, we identify 140 wp PV
modules of 17.7 V. The PV generator that we want to
install it on each bus will consist of 16 photovoltaic
modules in series and 15 module in parallel.
The whole constituting a branch of 283 V DC to be
connected to an inverters of 36 kW.
The network before
installing a PV
generator.
After installing a 33
kwp PV on a bus 3.
Another 33 kwp PV
generator was
installed on bus 4.
Finally a 33kwp PV
on bus5.
RESIDENTIAL NETWORK
Result before install PV on the network
A 5kwp PV on a bus 12 was installed.
Result after adding the PV from bus (12 to 4).
IMPACT OF THE CONNECTION OF PV ON THE
GRID VOLTAGE
Number of bus
Bus Voltage
befor install PV
Bus Voltage
after install PV
on bus 3
Bus Voltage
after install PV
on bus 4
Bus Voltage
after install PV
on bus 5
Bus 2
Bus 3
Bus 4
Bus5
392.5
376.2
376.2
376.2
393
381.1
376.7
376.7
393.4
381.5
381.5
377.1
393.9
382
382
382
395
393
391
389
Bus Voltage before install
PV
387
385
Bus Voltage after install PV
on bus 3
383
Bus Voltage after install PV
on bus 4
381
Bus Voltage after install PV
on bus 5
379
377
375
1
2
3
4
5
6
7
8
Number of
Bus
RESIDENTION NETWORK
Numbe V
r of bus before
install
PV
V
after
install
PV on
bus 12
V
after
install
PV on
bus 11
V
after
install
PV on
bus 10
V
after
install
PV on
bus 9
V
after
install
PV on
bus 8
V
after
install
PV on
bus 7
V
after
install
PV on
bus 6
V
after
install
PV on
bus 5
Bus 2
Bus 3
Bus 4
Bus5
Bus 6
Bus 7
Bus 8
Bus9
Bus 10
Bus 11
Bus 12
393.2
386.8
381.4
376.7
372.8
369.4
366.7
364.5
362.9
361.9
361.4
393.3
387
381.6
377.1
373.2
370
367.3
365.2
363.7
362.8
362.3
393.4
387.2
381.9
377.5
373.7
370.5
367.9
365.9
364.5
363.5
363.1
393.5
387.4
382.2
377.9
374.1
371
368.5
366.6
365.2
364.2
363.8
393.7
387.6
382.5
378.2
374.6
371.6
369.1
367.2
365.8
364.8
364.3
393.8
387.8
382.8
378.6
375
372.1
369.6
367.7
366.3
365.3
364.8
393.9
388
383
378.9
375.4
372.5
370.1
368.1
366.7
365.7
365.3
394
388.2
383.3
379.3
375.8
372.8
370.4
368.4
367
366
365.6
393.1
386.6
381.1
376.4
372.3
368.9
366
363.8
362.1
361
360.4

These results shows the compensation of the voltage
drop in line.
IMPACT OF THE CONNECTION OF PV SYSTEMS
ON THE POWER LOSSES IN DISTRIBUTION NETWORK


Installation of PV systems on the distribution network
changes the load profile of customers and hence
energy losses on the networks.
In the first distribution network The procedure of the PV
system increases from 0 to 100kWp. The reduction of
power losses is about 54.5% .
Electrical losses Before install PV
8.4 KW
Electrical losses after install PV at bus 3
6.8 KW
Electrical losses after install PV at bus 4
5.3 KW
Electrical losses after install PV at bus 5
3.9 KW

And also in the residential distribution network the
procedure of the PV system increase from 0 to 40 kwp,
the reduction of power losses is about 19%.
Losses befor insert PV
37.1 KW
Losses after Insert PV at bus 12
36.2 KW
Losses after Insert PV at bus 11
35.5 KW
Losses after Insert PV at bus 10
34.4 KW
Losses after Insert PV at bus 9
33.4 KW
Losses after Insert PV at bus 8
32.7 KW
Losses after Insert PV at bus 7
32 KW
Losses after Insert PV at bus 6
31.3 KW
Losses after Insert PV at bus 5
30.8 KW
Losses after Insert PV at bus 4
30.5 KW
Losses after Insert PV at bus 3
30.1 KW

If the energy losses on the network can be reduced, any
premature defect of network equipment caused by
thermal heating could be minimized. Hence, utility
companies may avoid or defer the needs of upgrading
their networks. This can help the utility companies to
minimize the cost of maintenance for their networks.
IS THERE ANY OTHER QUESTION ?
THANKS FOR YOUR ATTENTION