The document describes the design and modeling of an off-grid photovoltaic system for domestic loads. Key steps in designing the system include determining power consumption, sizing PV modules, selecting an inverter and battery capacity. Components of the system include PV modules, a charge controller, batteries, inverter and DC-DC converter. Simulation models of these components are created in Matlab and the System Advisor Model is used for performance and cost analysis. The results show that 72 150W PV modules, a 15KVA inverter and 6377Ah batteries can meet a daily load of 48.787kWh for a domestic home.

1. DESIGN AND MODELLING OF
OFF-GRID PHOTO VOLTAIC SYSTEM
FOR DOMESTIC LOADS
Batch Members
B. Sravani-12JG1A0204
V. Sri Sudha Phani-12JG1A0247
K. Esther Rani-12JG1A0219
G. Madhilina-12JG1A0208
Under the Guidance of
Mrs.V.SreeVidhya
Assistant Professor
DEPARTMENT OF ELETRICAL &ELECTRONICS ENGINEERING
GAYATRI VIDYA PARISHAD COLLEGE OF ENGINEERING FOR WOMEN
MADHURAWADA : : : VISAKHAPATNAM

2. ABSTRACT
 Solar or Photovoltaic( PV) systems are now popular
everywhere in world. These systems generates electricity to
meet the demands along with conventional resources. In this
project an Off-Grid PV system for a domestic load is
designed and modelled by using matlab software and sam
software.
 This system is so called an Off-grid PV system because there
is no grid connection available and PV system work
independently.
 SAM (System Advisor Model) makes predictions on
performance and cost analysis of the system. Hence, this
model is introduced in designing the system .

3. INTRODUCTION
 Off-Grid (stand-alone) PV systems have become widely
adopted as reliable option of electrical energy generation.
 The design of the Off-grid PV system is to supply the required
electricity for the appliances used during our daily usage. The
PV system is simulated with the use of solar radiation on a day.
 The photovoltaic (PV) technology has the versatility and
flexibility for developing off-grid electricity system for different
regions, especially in remote domestic areas.
 For the design it is necessary to estimate the load demand and
then select the components as per the requirement.

4. Stand Alone – Off-Grid System Components

5. Design of Off-Grid PV system
Steps required for designing of PV system:
1. To determine the power consumption:
-Calculate Energy consumed for each appliance
used.
-Calculate the total power needed from the PV
modules.
2. Size of the PV modules:
-Calculate the number of PV Modules required for the
system.
3. Inverter Rating;
4. Battery Capacity;
5. Charge controller.

6. Calculation of Energy Consumed by the load:

7. Result obtained from the sizing of the proposed Off-Grid
PV system:

8. Components in the Off-Grid PV System :
1.PV Module
2.Charge Controller
3.DC-DC Converter
4.Batteries
5. Inverter

9. PV Module :
 PV modules consist of PV cell circuits sealed in an
environmentally protective laminate and are the
fundamental building block of PV systems.
Cell

10. Simulation Models
PV module :
Presentation of the whole PV model

11. Subsystem 1 of PV Module :

12. Subsystem of Ioref :
Ioref = Isc,ref exp (voc,ref / a)
Detailed I0,ref implementation

13. Subsystem of Io:
Io=Isc,ref(Vocref/a)(Tc/Tcref)3 * exp((q€G/Ak)(1/Tcref – 1/Tc))
Detailed I0 implementation

14. Simulation of Iph:
Iph = G/Gref * (Iph,ref + µsc *ΔT)
Detailed Iph implementation.

15. Subsystem of Module Output :
Rp = Vmp,ref + Impref*Rs / (Iscref – Iscref(exp(vmpref+RsImpref –Vocref/a)) + Iscref
(exp(-vocref/a)) - (Pmax/Vmpref )
Detailed model with Rp term

16. Characteristics of PV Module:
V- I characteristics

17. V-P characteristics

18. Charge Controller:
 A charge controller or charge regulator limits the rate at
which electric current is added to or drawn from
electric batteries.
 The most important features of charge controller is to
maintain the battery voltage and protect the battery
against overcharging.
 During the operation of the PV array the temperature
and irradiation changes continuously, this results in
changing the V-I curve of the V-P array consecutively.
Therefore, the maximum power point of the curve can
be tracked to exploit the energy from the PV more
efficiently by MPPT Controller.

19. Charge Controller (MPPT)
Simulation Model of MPPT Charge Controller

20. Output of MPPT
power

21. Battery :
Batteries – stores DC output from the controller .
Boost Converter
Boost Converter (step-up converter) is a DC-to-DC
power converter with an output voltage greater than its
input voltage.
DC-DC Converter :

22. Boost Converter:
Simulation Model of Boost Converter

23. Simulation Results

24. Battery:
Simulation Model of Battery

25. Simulation Results
Discharge Characteristics of Battery

26. Inverter
 It is an electronic device that changes direct
current (DC) to alternating current (AC).

27. Inverter with load:
Simulation Model of Inverter along with Load

28. Simulation Results:
Simulation Results Of Inverter

29. Load Results :

30. SAM :(System Advisor Model)
 SAM uses a performance model to estimate the system’s total
annual output, and financial model to calculate the project cash
flow.
 SAM reports performance and financial metrics in tables and
graphs, which can be exported for use in reports or for further
analysis in other models.
 SAM calculates a system's total electricity production in kilowatt-
hours for the first year based on hourly weather data for a particular
location, and physical specifications of the power system
components.
 It then calculates the total production for subsequent years based on
an annual degradation factor, and annual cash flows based on
financial and economic inputs to determine the levelized cost of
energy and other economic metrics.

31. Location and resource

32. SAM Results
module :

36. Cost Analysis of the system:
Total cost =100%
 Module =53%
 Inverter =22%
 Installation cost =12%
 Miscellaneous cost=13%

37. Cost of the System :
 Module cost = Rs 13,68,000
 Inverter cost = Rs 5,67,849
 Installation cost = Rs 3,09,735
 BOS cost = Rs 3,35,547
Total cost = Rs 25,81,131

38. Calculation of pay back period:
initial investment
Pay back period = cash flow
= 12.08 Years

39. Advantages of Off-Grid System:
 No Interference with power companies or retailers.
 Generates, stores and uses own power.
 Unrestricted system size.
Disadvantages of Off-Grid system:
 More expensive than grid connected applications.
 Battery backup is required.
 Off- Grid PV systems must be designed and
installed by qualified technicians.

40. CONCLUSION:
 The results show that the total daily load requirement of
a domestic load is 48.787kWh/day. In order to meet this
load demand, 72 PV modules each rated at 150W, one
inverter of 15KVA and battery with a storage capacity of
6377Ah are needed.