Design of a standalone PV system for the all-weather condition

AIP Conference Proceedings 2461, 060001 (2022); https://doi.org/10.1063/5.0092260 2461, 060001

© 2022 Author(s).

Design of a standalone PV system for the all-weather condition: A practical approachCite as: AIP Conference Proceedings 2461, 060001 (2022); https://doi.org/10.1063/5.0092260Published Online: 17 August 2022

Adithya Ballaji, Ritesh Dash, Rajini H., et al.

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Design of a Standalone PV System for the All-Weather

Condition: A Practical Approach

Adithya Ballaji,a) Ritesh Dash, Rajini H, Manish Bharat, and Pavan B

School of Electrical and Electronics Engineering, REVA University, Bangalore, India.

a)Corresponding author: [email protected]

Abstract. In recent times, many researchers have presented various works on the design of standalone PV(SPV) systems. Though

from the review of certain works on SPV systems, it was noted that various critical parameters were not considered for the design

of the system. In the present work, a detailed design of a standalone PV system based on a practical approach for the all-weather

condition is proposed. Generation of power through SPV includes designing, identifying, and determining specifications of various

components being used in the system based on the load estimation. The process mentioned earlier mainly depends on factors like,

geographical location, type of weather conditions, insolation level of sun, and finally load consumption. Here a detailed outline

for the procedure specifying all the components of the standalone photovoltaic system for all-weather conditions based on typical

energy requirements is considered. The paper also presents an elaborate cost analysis considering the entire life span of solar

PV module installation and maintenance is also considered. The analysis highlights the high initial investment but also presents

the ROI amount and substantial dividend gains during the system life span. Thus the presented will act as a helpful resource for

designing and installing the SPV for rural and urban areas.

Keywords: Stand-alone, Solar PV array, Carbon footprints, Inverter, sustainability, Charge controller, battery, module orientation,

payback period

INTRODUCTION

In recent years, the rapid rise in the energy demand due to sophisticated technological advancement increased envi-

ronmental sustainability and scarcity concerns with the rise in the cost of fuels has led to increased research on the

fossil fuel like coal, petroleum, and natural gas is on a steep decline and get exhausted in a few hundred years [1]. The

rate at which energy is being consumed on one hand is rapidly increasing and may lead to the energy crisis and global

warming [2]. Solar energy is one of the most abundantly and easily available of all the renewable energy resources,

as it is clean and easy to use. In the last few years, electricity generation through solar is being vastly exploited

compared to other renewable energy resources because PV (Photovoltaic) technology can convert solar radiation into

electric power. As the PV technology is modular, it is an ideal choice and solution for off-grid power generation [3].

The current worldwide energy consumption is way less than the available potential of solar [4]. Solar energy can be

used for fulfilling our daily energy requirements during the available sun hours. But as we know the solar radiation is

not constant and is

supply day and night due to varying sunshine and climatic conditions. Thus one of the options is to have an energy

storage device like the battery, in this regard a standalone solar PV system is used. Climatic conditions are different

around the globe.

varies based on the time of day, season, location, and climatic weather conditions. Considering the above-mentioned

factors, standalone PV systems do not have one particular standard. One of the factors which mainly affects the

generation and PV system is the location of the system, as the condition varies from place to place [5]. India is a

country with enough sunshine for a complete year and is pollution-free, which helps in reducing carbon footprints. A

standalone system is a concept that can be used in rural areas where grid-connected power is difficult to reach. Urban

areas are placed where grid-connected electricity is available and the usual impression being standalone systems are

costlier compared to grid-connected electricity. In this regard, a typical load estimation based on the urban scenario

is carried out in the paper. The standalone PV system is one of the favored ways of harnessing solar energy due to

its various advantages like energy independence, safety, security, and unwanted electricity bills [6]. Easy installation

and low maintenance being an add-on to the list of advantages. Energy storage through battery banks has provided

much more robustness and reliability to the system. In this regard, a standalone PV system is proposed for the urban

household scenario. The proposed work aims to present a detailed consideration for the design of the SPV system

using a practical approach. Thus this paper gives procedures and technical specifications and guidelines for designing.

Sizing and component selection based on the equipment availability is presented. The paper also highlights the cost-

International Conference on Recent Trends in Electrical, Electronics & Computer Engineering for Environmental and Sustainable Development

AIP Conf. Proc. 2461, 060001-1–060001-15; https://doi.org/10.1063/5.0092260

Published by AIP Publishing. 978-0-7354-4357-0/$30.00

060001-1

ing benefits in long term compared to the conventional source to encourage the use of the SPV system proposing the

SPV system being more economical and cost-effective. Finally, the paper presents the design and function of a SPV

system briefly in the following section. In section 2, the statement of the problem is presented. Section 3 describes

the steps, procedure, and design consideration. In section 4 a practical case scenario of an urban Bangalore household

is considered. And finally, section 5 gives the costing details followed by the conclusion in section 6.

STATEMENT OF PROBLEM

The standalone PV system is an important part of power generation through solar. Many researchers have conducted

studies on the SPV system. For any system to operate on high efficiency and deliver expected output the design

of the system must be carried out with all the technical considerations, procedures, and factors affecting the power

generation through solar. It is seen that many of the important factors are not considered in the design of the SPV

system. This lapse in the design procedure leads to low power output, faults in the system, reduced life of the system,

losses and low efficiency of the system, and finally high maintenance and investment cost. A detailed critical review of

selected articles on the SPV system is done and drawbacks are highlighted in table 1. Considering all the drawbacks

and research gaps in the critical review, a detailed design of a standalone PV system for the all-weather condition

using a practical approach is proposed in the paper.

STANDALONE PHOTOVOLTAIC SYSTEM

The standalone PV system is an interconnection of various electrical circuits together by the application of which

generation of electricity can be done without any interval due to unavailability of sunlight [5]. The proposed system is

TABLE 1. Research Gaps

Reference Drawbacks / Research Gaps

Ref.[7] 1. The proposed work highlights the software aspect of designing a Standalone PV system.

2. Does not take into account the practical factor and parameters of designing a standalone PV system

Ref. [8]

1. Validation is based on simulation results.

2. No manual calculation or justification is provided.

3. Design consideration for a standalone PV system is not presented.

4. The paper highlights the monitoring of batteries (storage) and MPPT with the presentation of any design

calculation.

5. Phantom load not considered

6. Cable loss not considered

Ref. [9]

1. Validation is based on simulation and not actual design formal for the standalone PV system.

2. Design of inverter not considered.

3. Phantom load for load estimation is not taken into account.

4. While selecting the peak sun hour, the darkest month is to be considered and not the yearly average.

Ref. [10]

1. Hardware validation and actual design consideration not presented.

2. Practical design procedure for standalone PV system not considered.

3. Actual load (R and L) is not taken in load estimation specifically.

4. Load for all-weather not taken into account

5. Phantom load not considered

Ref. [11]

1. The results are presented without proper calculation, with no validation.

2. Phantom Load not considered.

3. Extra % for inverter design not taken into account.

4. The efficiency of the Inverter is not considered for Inverter calculation.

Ref. [12]

1. Design consideration is presented without any practical implementation.

2. Phantom Load not considered.

3. Load utilization as per all-weather consideration.

4. Optimum sizing of the battery bank, and No. of series and parallel modules to be connected.

5. Phantom load not considered

6. Cable loss not considered

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FIGURE 1. Block diagram of the Standalone PV system with different components.

usually used when the requirement of power is 24*7, i.e., the power supply to the load is not interrupted due to change

in climatic conditions (reduced sunlight) and due night time. SPV system consists of the following components: 1)

Solar PV array 2) Array Disconnect 3) charge controller 4) Battery bank 5) Inverter 6) load disconnect 7) cables and

protective devices. Depending on the load requirement and intensity of sunlight at the location, the system components

are specified and selected. Fig. 1 gives the block diagram of the SPV system with different components. The following

subsection gives a brief insight into the details and function of different and components [13].

Solar Photovoltaic Panel

The main and primary component of the SPV system is the Solar photovoltaic cell, also called a solar cell, it generates

solar cell [13]. Together a collection of these solar cells make up a solar panel. The required voltage and current

for a particular system are achieved by connecting this individual PV panel in series and parallel or a combination of

both which forms a PV array.

Charge Controller

A charge controller is a device used to regulate the flow of charges (current) between the two main components

of the SPV system i.e., PV array and battery. The charge controller is the heart of the PV system. The charge

controller mainly regulates the flow of the current of the battery. It protects the battery from over-charging and voltage

fluctuations [14]. Two types of charge controllers are available: Solar charge controllers with PWM technology and

Solar charge controller with MPPT technology. The proposed work uses the latter for its application.

Battery Bank

One of the most important functions in a Standalone PV system lies with the battery bank. The main function of

the battery bank is to store energy during sunshine hours and deliver it to load during non-sunshine hours. There

are various types of batteries like lead-acid, VRLA battery, and a lithium-ion battery which are used based on the

application and cost of the system.

Inverter

The inverter is one of the most important parts of the system, as it delivers the power to the load in its required form

for AC applications. It is also called a power conditioning circuit. Since most of the appliances used in residential

buildings work on AC, these inverters convert the DC input from PV and battery to AC for it to be delivered to the

load.

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Balance of the System Components

Balance of system components or BoS are important components of the system, they mainly balance the system,

and mostly consist of protective devices, which include blocking and bypass diodes, lightning-protection system,

fuses, bus-bar, and cable wiring, together these all are called as the balance of system components [15]. The efficient

protection of the system is done by BoS. In addition to it, the selection of cable also plays an important role as the

voltage drop and cable loss should be minimized.

Load

These loads are the power consumption devices or the units in the PV system which are to calculate for the design of

the PV array. For an efficient PV system, it is necessary to have a proper calculation and load estimation. Electrical

loads need to be considered by taking the weather condition into account as the usage varies depending on the weather.

Phantom is one of the most important factors to be considered as most load estimation neglect it and burdens the

system. Considering all these factors a proper load estimation should be carried out for residential buildings. The

amount of power generated by the panel is effected by the load connected to the PV System. the type of PV panel

and rating of panel to be installed is mainly decided by the type of load. The residence load profile is determined by

listing all the residential applications with their power ratings and hours of operation at different seasons to obtain the

total average energy demand in watt-hours. The total average energy demand in watt-hours is calculated by taking

into account all the different residential with their power ratings and hours of usage for different seasons.

Here in the proposed work, system is designed considering the maximum load consumption of all four seasons.

PV SYSTEM DESIGN METHODOLOGY

Design of a PV system is a tedious and meticulous process of determining the capacity of the system in terms of

power, voltage, and current for each of the components of the PV system with the need to achieve the load estimation

requirement of the residential building, the design for same is being carried out. The system design consists of 10

steps. First step is the Inspection of site and analysis of sun radiation, as it plays a major role is power extraction by

the Solar PV.

Step 2: calculation Building load requirement

Step 3: Components and choice of system voltage

Step 4: Estimation of Inverter Capacity

Step 5: Estimation of Battery Capacity

Step 6: Specification of Charge Controller

Step 7: Designing of layout and solar PV array specification

Step 8: Cable sizing (DC)

Step 9: Land requirement and PV module orientation

Step 10: Cost Analysis

Inspection of Site and Analysis of Sun Radiation

The first and one of the most important steps in the design of the SPV system is the inspection of the system installation

site and analysis of sun radiation [16]. The number of sunny days per year is estimated based on the location. The

energy generation through panels depends on the radiation of the sun throughout the year. The temperature effect is

also carried out to find the effect of temperature on voltage and current of cell. Shadow analysis is also carried out

to find the solar radiation falling on the solar panel. Sun path at a particular location is very important to calculated

the azimuth and altitude angle [17]. Here an online PVWatts calculator software is used to analyse the monthly solar

irradiance for location of the proposed work.

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Building Load Requirement Calculation

The power of the system that needs to be installed depends on the electric load of the building. The load profile of

the residential building is determined by listing all the equipment used with their power rating and hours of usage to

determine the total average energy demand in watt-hours. The load estimation is done and considered based on the

requirement of all four seasons. The detailed step-wise calculation of load estimation is mentioned below:

Step 1: All the AC Loads are listed with wattage and hours of use for a week. (No AC load then skip to Step 5)

Watts is multiplied by hours/week to determine AC watt-hours for each week. All watt-hours for a particular week

are added to find the total AC watt-hours per week.

Step 2: The above results are converted to DC watt-hours per week. The result of Step 1 is multiplied by 1.13 to

correct it for inverter loss.

Step 3: DC Load as per their wattage and hours of use is listed. Watts is then multiplied by hours/week to determine

DC watt-hours per week (Wh/Wk). watt-hours per week are added together to determine total DC watt-hours per

week.

Step 4: DC watt-hours per week are determined. The DC loads converted from AC loads from step 2 are added with

DC load from step 3. Finally, the phantom load is also added to it.

Step 5: The total watt-hours/day consumption is divided by 7 to get the total average watt-hours per day that are

required to be supplied to the battery. The load estimation in table 2 below is carried out for s residential house in

Bangalore, Karnataka.

TABLE 2. Load calculation

SL.NO Parameter Value and Unit

1 Peak Watts 4934W

2 Total AC Wh/week 52027W

3 Total AC Wh/Day 7432W, Considering Inverter with 90% efficiency

4 Peak watts 4934x1.10 = 5.5kW

5 Total DC Wh/week 59831W

6 DC Wh 9kWh

7 Adding Phantom Load 3kW

8 Total DC Wh/Day 12kWh, Considering DC Loads of 500W

9 Total DC Wh/Day 12.5kWh/Day

Considering all weather conditions, below table 3 gives the load estimation for different weather conditions. Here

the load calculation and estimation is done based on average load consumption in Bangalore, residential area.

TABLE 3. Load estimation for different weather

Weather Type Load Estimation

Winter 12.5kWhDay

Summer 10.2kWhDay

Autumn 9.5kWhDay

Spring 10kWhDay

Inverter Capacity Estimation and System Voltage

As we are aware that the SPV system delivers DC voltage and power, it is very much important that DC power is

converted to AC power, most devices used in residential applications work on AC power. The inverter is rated at its

rated Power (PKVA) and DC output voltage (VDC). The power rating of the inverter should not be less than the total

power consumed by all loads and must have the same nominal voltage as the battery bank. Power delivered by inverter

PINV is taken 1.25 times of the peak load in case of future load expansion. The power factor considered is 0.8 and thus

PKVA is given by,

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PKVA PINV /PF (1)

The efficiency of the inverter is a very important parameter as the DC-AC Power conversion depends on the effi-

ciency of the inverter INV Load power continuously to the inverter is given by,

T P1 TP/ INV (2)

Input Continuous DC (IDC) to the inverter from the PV module is to be calculated by taking the system DC voltage

(VDC) which is given by,

IDC T P1/VDC (3)

The daily energy input to inverter EINV is one of the most important parameters needed for the battery selection

and design and given by,

EINV EDaily/ INV (4)

Detailed and Calculated inverter specifications are listed in table 4 below:

TABLE 4. Load estimation for different weather

Parameter Calculated Parameter Value

Total Continuous output power (TP) 7kW

Efficiency ( INV ) 90%

Power input to the inverter (T P1) 8kW

DC input voltage (VDC ) 360VDC

DC input current to the inverter (IDC ) 25 ADC

Power Factor (PF) 0.8

Total Inverter Power (PINV 1) 7kW

KVA rating (PKVA 9KVA

The energy coming from the inverter (Daily) 12kWh

The energy input to the inverter (EINV) 13.3kWh

Output AC voltage 240VAC

Number of phases Three

Types Solar PCU/Hybrid Type

MPPT voltage from PV (CCvolt) 500V

Battery Capacity Estimation and Charge Controller

Deep cycle batteries are usually selected for the application in the SPV system, and are designed and developed such

that even when discharged to a low energy level can still be recharged rapidly over and over again. The battery selected

should be able to store sufficient energy enough for operating loads on rainy or cloudy days and at night times. The

detailed calculated specification of the battery is given in table 4. Charge controllers are the heart of the system and

are used to regulate the flow of charge to the battery and protect the battery from overcharging. There are two types of

charge controllers namely PWM and MPPT, in recent times the latter is being used because of its high efficiency and

ability to extract maximum power. In the proposed work, a Schneider XW-MPPT600-80, with a rating of 600VDC

maximum input voltage and 48VDC nominal battery voltage is used.

Battery bank (BAh) is the energy storage capacity and calculated using the requirement of daily energy and the of

autonomy (number of days) or also known as BACKUP [18] and is given by,

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V

BAh EINV NBACKUP / VDC DoD (5)

The depth of charge (DoC) of the battery is known as the amount of energy that is used for delivering the load. C-

rating determines the charge and discharge of batteries. Usually, C-10 rating battery is used. The optimum battery

bank is given by the equation,

BOAh TP

Crating (6)

The load requirement is met by actually connecting the batteries in series Bs and parallel Bp connection and is given

by the equation,

Bs VDC

Voltage of single battery

(7)

Bp BAh

Ah capacity of a single battery

(8)

As the number of batteries for series and the parallel connection is determined, the total number of batteries can be

given by the equation,

NB BS BP (9)

The efficiency ( Bat) of the battery is considered to be 85% for a lead-acid battery which is widely used in SPV

system [18] and thus the energy which required (EBat) from the battery bank to get charged from the PV array is given

the equation,

EBat VDC BAh/ Bat (10)

Using the above equations, the battery specification is calculated and presented in table 5 below.

PV Array Sizing and Design of the Layout

The main component of any SPV system is the solar PV array. When several PV modules are connected in series they

are called strings, and these strings together are known as PV arrays. They are used in array form only if the load

requirement is high, as in the case of proposed work. Based on the values of current and voltage the design of the PV

array should be carried out. In a typical PV system, the cable loss for OV to the battery is considered to be 3% [19].

Thus the PV array voltage is given by VPV and is given by,

Vpv CCVOLT

cable

The PV array energy requirement (EPV )is given by the formula,

Epv

EBat

cable

Similarly, the current requirement from the PV array for every hour is given by the equation,

(11)

(12)

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TABLE 5. Calculated Battery specifications

Parameter Calculated Parameter Value

Per day usage 7 hours

Autonomy (NBACKUP) 3

Battery type Lead Acid Battery

Depth of discharge (DoD) 50%

Battery bank capacity required (BAh) 2770Ah

Operating voltage of the battery bank (VDC ) 48

Each battery voltage 2V

The capacity of each battery 1620Ah

Total number of strings (BP) 3

No. of batteries in each string (BS) 24

Total no of battery required (NB) 72

C-rating 10

Energy require to charge battery(EBat ) 156.42kWh

TABLE 6. Average monthly radiation data of the location

Month Irradiance

(kWh/m2/day)

JAN 6.52

FEB 6.49

MAR 6.74

APR 6.43

MAY 6.07

JUN 5.02

JUL 4.51

AUG 4.55

SEP 4.93

OCT 4.79

NOV 5.15

DEC 5.85

Ipv

Epv

Vpv Dailysunshinehour

(13)

The date for the Bangalore region of daily peak sunshine hours is given in table 6 and the darkest hour for the month

is selected for calculation [20] [21]

A PV array is made of numerous PV modules which in turn are connected in series (SPV ) to form strings and

these strings are connected in parallel (PPV ) to obtain the required voltage and current of the array. The maximum

voltage and current for a PV module are VM and IM. here standard test conditions (STC) are considered IEC standard

of 60891(2009) are used to get the correct values for VM and IM under ambient conditions of the SPV system

installation site. The SPV is given by,

Spv

Vpv

VM

(14)

Once the module is connected in series, the voltage of the PV string is equal to VPV . The current rating is the same

as the individual PV module and thus IM. Thus the voltage and current for each string are given as VPV and IM. IPV

is the current required from the PV array, due to the current surge, a few strings are connected first in parallel and a

fuse is connected to the circuit.

considered as 20A and depends on the module manufacturer. Thus the value of p is given by dividing the fuse current

by module maximum current as shown in below equation

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p 20

IM

In array, the total number of strings required to complete is given by,

Ppv

Ipv

p IM

Finally, the total number of PV modules (NPV ) required is

(15)

(16)

NPV PPV SPV p (17)

Below table 6 gives the details of the PV module selected for the work presented [22]. The calculated values of the

solar PV array specification are presented in table 7 below.

TABLE 7. Selected PV module specifications

Parameters Specifications

The power rating of the individual PV

Module 345WP

VOC 68.2V

VM 57.3V ISC 6.39A

IM 6.02A

Module efficiency 21.50%

Power Tolerance 0-5%

Technology 96 Monocrystalline

Maximum System Voltage 1000V IEC

Maximum Series Fuse 20A

Power Temperature coefficient -0.30%/°C

Generated Power for the first 5 years 95%

Land Requirement and Orientation of PV Array

For a SPV system, land size estimation and orientation of PV modules on very important parameters. It is required

that the design include calculation of inter-row spacing and orientation of PV modules for tilted or ground-mounted

PV systems. This is carried out to avoid potential shading of PV modules.

The orientation of PV modules for tilted or ground-mounted PV systems. This is carried out to avoid potential

shading of PV modules. Determining the orientation and inter-row spacing for a system is a bit complicated and

troublesome, avoiding which may lead to under performance of the system and reduced efficiency. The first step is to

calculate the inter-row spacing. Fig.2 shows the diagram for the inter-row spacing. The Average sunlight angle (a) is

taken to 47 and Tilt Angle (W) is 36. Fig. 3 Shows the Area of the PV panel and Fig.4 shows the final wiring diagram

of the proposed system.

The above shows the arrangement of PV modules in array form and the total area required for the PV array rep-

resentation. The area is presented with proper inter-row spacing calculation. Based on the calculation of the PV

array area, the final wiring diagram for the SPV system is presented in Fig. 4 with an option for wind and generator

integration.

Cable Sizing of the System

The sizing and selection of cable are a very important part of the system design. Output and efficiency of the system

is being also dependent on the type and size of cable selected. In cases when the cable is not selected appropriately

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FIGURE 2. Determining the inter-row spacing between rows [7].

FIGURE 3. 6.236m2 x 12.69m2 area of PV Array.

FIGURE 4. Proposed block diagram of SPV system [24].

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TABLE 8. Detailed parameters of PV array Specification

Parameters Specifications Reference Equation

Total PV array capacity 38kWP Total no. of modules *

wattage rating per module

Energy Required from PV array (EPV ) 161.25kWh From equation12

Array voltage output (VPV ) 515v From equation11

Array current output (IPV ) 70A From equation13

No. of strings (PPV ) 4 From equation16

No. of modules in series (SPV ) 9 From equation14

No. of modules in parallel connected in

the string (p)

3 From equation15

Total number of modules 108 From equation17

DC wire Length 10m

and it draws more current than its rated value, it damages the entire system. This would lead to high losses. Hence

most of the cable selected is usually rated more than the actual required value. Cable sizing for the PV system is done

in two ways:

Inverter to cable sizing of battery

Solar Photovoltaic to inverter cable sizing

Inverter to Cable Sizing of Battery

The main basis of inverter cable wiring depends on the maximum continuous input current (IB1) which is given by,

IB1 TP

VLB

(18)

In the above equation, the lowest voltage VLB) should be selected the voltage level that is just above

the value at which it will get disconnected to avoid discharging.

Solar Photovoltaic to Inverter Cable Sizing

The energy loss and loss of voltage in the cable are considered to be 3% [19]. Based on this the DC rating of the cable

is given by,

IDC IPV 1.25 1.25 (19)

Here due to safety consideration, the oversize of wire is done at 25% more than the continuous current that the wire

will be subjected to due to high radiation intensity. Voltage drop due to cable is

VDROP_DC VPV 3% (20)

VDROP DC

2 LDCCABLE IDC p

(21)

_ ADCCABLE

The resistivity of the cable material is given by p, LDCCABLE Is the length of the cable and ADCCABLE is the area of the cross-section of the cable. Based on the above equations, the DC Cable details are mentioned in below table 9.

Thus from the above table, it can be seen that the voltage drop in cable plays a very important role in the SPV

system.

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TABLE 9. DC Cable specification and voltage drop

Parameters Ratings / Values Reference

Maximum continuous input current (IB1) 34A Equation 18

DC rating of cable (IDC ) 87A Equation 19

Standard Drop (VDROP_ DC ) 15V / (3%) Equation 20

Actual Drop (%) (VDROP_ DC ) 1.64% Equation 21

Actual Drop (V) (VDROP_ DC ) 8.4V Equation 20

Cost analysis and costing methods

The different components which make up the solar PV system are costly. The initial investment in Solar PV systems

is high. The different components used for the proposed SPV system and final costing are given in table 10 below.

Here the PV module cost is taken as INR 48/- per watt peak (on the higher side) and Battery cost as INR 15/- per Ah.

TABLE 10. Cost of Proposed SPV system

Name of the Component Quantity Price per quan-

tity (INR)

Total Price

(INR)

Solar Panel (Sun Power) Model

No x21-345wp

108 16560/- 1788480/-

GIANT POWER (1620Ah, 2V) 72 23400/- 1749600/-

Lento Industries Private Limited,

(10KVA,360VDC)

1 350000/- 350000/-

Total Cost of the above materials 3,888,080/- Other components like cable, Labour, Metering, junction box,

and Control Device, etc. are lump together as 100% of the

above component cost

388808/-

Final Total Investment 42,76,888/-

The above table gives the details of the Initial investment, here Land cost is not considered in this case as the area

for the proposed system is considered to users own. Hence no initial investment is required for residential buildings.

With the stated initial investment, it is difficult for users to opt for the SPV system as it is a high initial investment.

Thus the payback period is presented stepwise to establish financial feasibility. Procedure calculating the payback

period and economic feasibility stepwise explained below.

Step 1: Find the total number of units generated by the PV system in a Day. As per the calculation, the average

sunshine hour considering the darkest month is 4.51 hours and the 38kWp PV system has an efficiency of 75%. The

PV module efficiency lasts for the first 5 years and then it starts degrading at a 0.4% rate every year. Thus unit

generation per day for the first year is given as 4.51x38x75x95 which is equal to 122 Units. Similarly, the per day unit

generation can be calculated for the remaining 25 years.

Step 2: Determine the amount (rate) of electricity from the grid and the amount (rate) of electricity is different based

on location in India and also for rural and urban households. In Karnataka, the following are the rate for electricity

based on the number of units consumed.

Step 3: To find the present value of the future investment. Find the present value of the future investment is given by

the equation mentioned below [23].

PresentValue FutureValue 1 in f lationrate / 1 discountrate n (22)

The present value is the present valuation of all the future investments made and product costs after n number of

years is the future value. The money value when it decreases with time is known as the inflation rate. Here n is the

number of years.

Step4: Write inters of Return on Investment or Payback Period.

Once the SPV system is installed it will not be needed to pay the electricity cost from the grid. Saving per year

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FIGURE 5. Flow chart for design and economic feasibility of PV system.

with a deduction on maintenance cost of 10% per year is explained further with an example for the first year. The

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electricity consumption for the first year (122*7.00*365) is equal to 3,11,710/- from which 10% as maintenance cost

for each year. The final saving will be 2,80,539/-. Considering the first year saving, for the first 5 years the saving

will be around 14,02,695/- and for 25 net saving will be 77,92,250/-. The SPV system though is of high initial

investment, but over some time contributes to a lot of saving and is economically feasible. There are other online

tools also for calculation of the payback period listed below:

1. MNRE- SPIN An online application Solar Photovoltaic Installation

2. Solar Mango calculator - Rooftop Solar Electricity: Cost Estimator for Industrial/Commercial Consumers

3. PVCalc The return (ROI) calculator for Solar PV energy investments The complete flow chart of a standalone

PV system is as shown in Fig. 5 below. The flow chart gives the detailed and stepwise procedure to be carried out

while designing the standalone PV system. The life cycle costing for savings and economic feasibility is included.

The process chart gives the complete overview of the design process and requirements for the standalone PV system.

CONCLUSION

SPV systems are the main source of clean energy and help in reducing carbon footprints. The proposed system till

now has been contemplated for rural use where grid power is not an option. In urban areas, since the power is supplied

from the grid and initial investment on the SPV system is high. This has led to fewer users using the solar PV system.

Even though the irradiance varies from 700 W/m2 to 1100W/m2 but it more than sufficient to generate energy for the

requirement of residential applications needs if the energy is efficiently extracted from the sun. the paper presents the

detailed and complete stepwise design of standalone PV systems and cost analysis methods. Earlier various works

on the SPV system have been presented, but there are many drawbacks in the design considerations and hence same

has been considered and an optimal and efficient system has been presented. The power needed for the electrifying is

7kW and the initial investment for the system is around 43 lakhs (rounded off). But even though the initial investment

is high, but with a payback period, it can be less than 15 years, and the system life is 25 years, with the remaining 10

years of saving. In the future, with technological advancement, the costs of the components will be reduced which

would even reduce the payback period further. The proposed work presents the costing analysis and steps to carry

out payback period calculation both manually and online. Though the costing is not presented in detail and just an

overview is given in the paper, as costing payback period in the SPV system is a separate area of research and will

be taken as future work.

it would make it a more popular choice and enhance sustainable development thereby reducing dependence on grid

power and reducing carbon footprints.

ACKNOWLEDGMENTS

The authors would like to express their heartfelt gratitude and thanks to REVA University for providing us with the

facility and support to carry out the proposed work.

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