International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, Volume 8, Issue 20, August 2012)
SIZING OF A STANDALONE PHOTOVOLTAIC SYSTEM
FOR SMALL SCALE INDUSTRY
Akanksha Kumra1, Manoj Kumar Gaur2, Chandrashekhar Malvi3
1,2,3
Deptt of Mechanical Engg, MITS, Gwalior
government support , solar PV technology is seen as a
solution for energy supply.
The solar cell efficiency has increased over 24 %[2].The
world annual production is currently over 10000 MW and
solar PV technology are now increasingly seen as a major
energy provider for Indian scenario[3].
Solar photovoltaic has a wide range of applications, one
of them being developing a standalone PV system for small
scale industries. Various advantages for small scale
industries by using this technology are:
1. Reduction in conventional electricity cost.
2. Reduction in Carbon credits
3. Gives clean energy which will offset carbon
dioxide emission every year.
4. During power outages or load shedding electricity
can be provided through these systems especially
in administrative buildings in small scale
industries.
This paper includes a small scale industry’s
administrative building for sizing of PV system. This
industry is situated in Gwalior M.P.
Abstract - This paper presents a study pertaining to the
design of a standalone photovoltaic system to supply
electricity to a small scale industry’s administrative building.
The estimated load of the system is about 6.5 kWp.
Methodology is discussed and based on the load estimation,
batteries and arrays are sized and result presented in a
tabulated form. Layout, installation and life cycle cost of the
system have also been discussed with life cycle cost of the
system as 42 lakhs and payback period as .72 years.
Keywords - Photovoltaic system, standalone, small scale
industry building, sizing, life cycle cost, payback period.
I.
INTRODUCTION
Electricity from unconventional energy sources is
becoming popular these days due to governmental support
and investment from private enterprises. Among these
unconventional energy sources solar photovoltaic
technology is emerged out in gaining interest especially in
country like India, where solar energy is abundantly
available throughout the year[1].
Rising electricity cost ,concern for climate change and
need to find alternative energy solutions and with
65
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, Volume 8, Issue 20, August 2012)
FIGURE 1
SOLAR RADIATION MAP OF INDIA [1]
66
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, Volume 8, Issue 20, August 2012)
II.
For a clear day, the intensity of solar radiation at a given
location is symmetrical around the solar noon time of the
location. Also the radiation intensity is maximum at noon.
Therefore the solar PV modules are oriented to maximize
solar radiation interception at noon time. It can be shown
that if the PV modules are to be fixed throughout the year,
at a fixed angle, the optimum tilt of solar PV modules
should be equivalent to the latitude angle of the location.
Also, if the modules installation is done in the Northern
hemisphere the orientation should be South facing and if
the PV modules are being installed in Southern hemisphere
then the PV modules should be installed North facing [3].
C. Battery sizing
Only PV bateries should be use for PV system. While
designing battery bank days of autonomy should be kept in
mind. The days of autonomy are the days of below average
insolation days. Generally two or three days are considered
in designing. Other factors like maximum depth of
discharge, temperature correction, rated battery capacity
and battery life are also considered [4].
For deep cycle battery maximum depth of discharge is
80%. In this design we will take depth of discharge to be
65%. Temperature correction is needed because at low
temperature battery efficiency decreases. Temperature
correction factor is taken to be 0.9.
Required battery capacity in Ampere hour (Ah) is given
by
Brc= Ec(Ah) × Ds/(DOD)max × t
(4)
where, Ds =battery autonomy or storage days;
(DOD)max = maximum battery depth of discharge;
t = temperature correction factor.
Batteries in parallel is given by
Bp =Brc/Bsc
(5)
where, Bsc = capacity of selected battery (Ah).
Batteries in series is given by
Bs =Vnsv/Vnbv
(6)
where, Vnbv = nominal battery voltage.
Vnsv= Nominal system voltage
Total battery
BT = Bp × Bs
(7)
D. Array sizing
For a DC bus voltage of 110 V,
No. of modules per string =
110 + 1 (allowance for blocking diode)/
Working voltage
(8)
METHODOLOGY
The system sizing involves various steps which are as
followed:
1. Load estimation of the system under consideration
2. Battery sizing
3. Array sizing
4. Array tilt
5. Layout of the proposed system
6. Life cycle cost of the system
7. Payback period
A. Load Estimation
System design is based on the size of the load. The
operating voltage selected for a PV standalone system is
usually the voltage required by the largest loads [4].
Energy demand is given by Watt –hour per day
by
Ed(Wh)= ∑
NiIiViHi
(1)
th
Where Ni =number of i load
Ii and Vi are the current and voltage drawn by the ith loads
Hi= Daily duty cycle of the ith load (hrs/day)
Load demand in ampere-hour is given by
Ed(AH)= Ed(WH)/ηpce Vnsv
(2)
Where ηpce = power conversion efficiency
As we are not using inverter hence we will not consider
the above efficiency factor.
However where inverter is used power conversion
efficiency factor should be taken into consideration.
Vnsv =Nominal system voltage
Corrected Ampere hour load is given by
EcAh = Ed(Ah)/ ηwηb
(3)
ηw =wire efficiency= 2%
ηb = Battery efficiency= 16.5%
B. Array Tilt
Optimum tilt of PV modules – permanently fixed
To maximize generation of solar radiation the
interception of solar radiation has to be maximized. For
maximum interception of solar radiation the solar PV
modules should be kept perpendicular to the sun rays. Sun
changes its position throughout the day, hence the position
of the PV modules should also be changed throughout the
day, i.e. sun tracking is required. Since precise tracking is
not possible also the cost of the system increases due to
costly tracking equipment moreover it requires
maintenance. Therefore fixed mounting of solar PV
modules is advised and preferred.
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International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, Volume 8, Issue 20, August 2012)
Now Total cell area required to meet a mean daily load
can be found out from the following [5]:
1. Calculate the mean daily solar radiation available
2. Calculate Mean daily output available from PV
module surface area of 1 m2 is given by
{(mean daily solar radiation available)* (module
efficiency) * (irradiance of cell available from
manufacturer’s specification) }/ Largest system
voltage
3. Array losses due to module mismatch, blocking
diodes, dirt, and degradation is considered and
multiplied with the above to get Gross mean daily
output available from module area of 1 m 2
4. The area of PV module required is given by
Mean daily load required/ Gross mean daily
output available from module area of 1 m 2.
5. Number of PV Modules is given by
(The area of PV module required)/(Area of
standard PV module available)
6. Minimum number of module strings is given by
Number of PV Modules/ No. of modules per string
III.
The total estimated load for the entire system is 6.5kW p
as shown in the Table 1 above.
FIGURE II
SHOWING BASIC LAYOUT OF THE SYSTEM
TABLE II
RESULT OBTAINED FROM THE SYSTEM SIZING
RESULTS AND DISCUSSION
A. Load Estimation for the system
TABLE I
SHOWS LOAD ESTIMATION OF THE SYSTEM AS GIVEN BY
BRITANNIA INDUSTRIES J B MANGARAM GROUP GWALIOR
Corrected Amp – hour load Ec =Ed/ηwηb
Here ηw =Wire efficiency= .975
ηb= Battery efficiency= .835
Ec= 726.23
The system consists of Solar PV Panels which are
connected to batteries through a control system and an
inverter.
Batteries are used due to intermittent nature of solar
energy so that excess energy can be stored during active
periods so that load can be carried during inactive periods.
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International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, Volume 8, Issue 20, August 2012)
IV.
Payback Period
Yearly conventional electricity cost for the system
=3321500
Payback Period = .72 years
LIFE CYCLE COSTING OF THE SYSTEM
Economic parameters and cost of components [6] are
shown below in Table 4.
TABLE III
SHOWING ECONOMIC PARAMETERS AND COST
PV array cost
Rs 150/Wp
Battery cost
Rs 4000/kWh
Battery Charge controller
Rs 27000
V.
cost
Auxiliaries cost
Rs 11250
General Inflation rate
7.5%
Discount rate
10 %
Annual Maintenance and
2%
‐ Roof tops of buildings
‐ Roofs of parking area and path ways
‐ Any other open area
In this particular case installation design has been done
on the roof of the administrative building.
VI.
Operation cost
PV system installation cost
10 %
DC Motor Cost
Rs 10,000
Interest Rate
14.29 %
Number of Years
25
PV INSTALLATIONS IN ADMINISTRATIVE BUILDING
Since most of the buildings in a given industry are of
same height, building terraces offer excellent locations for
SPV installations.
The possible spaces for installation of PV modules
include:
CONCLUSION
Suitable layout of the system has been given and results
of battery and array sizing have been tabulated. Initial cost
of the system is high but since the payback period is .72
years , hence the system is economical. Future scope exists
in sizing of the standalone system using Fuzzy logic.
ACKNOWLEDGEMENT
We would like to express our sincere thanks to Mr. U .K
Chauhan Production Head, Britannia Industries JB
Mangaram Gwalior for all his support.
The life cycle of the system is taken as 25 years .
Batteries have a life time of 8 years.
The cost of first group of batteries = 12,80,000
Present worth of second group of batteries= A(1+i) N-1/
(1+d)N= 985535
Present Worth of third group of batteries= 822658
Total PV array cost= 975900
Cost of battery charge controller= 27000
Initial cost of the PV system= PV array cost + first group of
batteries cost +Cost of battery charge controller + Inverter
Cost + Auxiliary cost
Initial cost of the system= 2399740
Life cycle cost of the system= Initial cost of the PV system
+ Installation cost + cost of second and third group of
batteries + Maintenance and operation costs
Life cycle cost of the system= 4207932
Life cycle output energy= 474500 kWh
REFERENCES
[1] Ministry of non renewable energy http://www.mnre.gov.in/ .
[2] Martin A. Green, Keith Emery, Yoshihiro Hishikawa, Wilhelm
Warta and Ewan D. Dunlop- Solar cell efficiency tables (version 39)
progress in photovoltaics: research and applications Wiley
[3] Chetan S. Solanki -Solar PV Energy for Academic Campuses in
India -A White Paper Department of Energy Science and
Engineering IIT Bombay Oct 2010.
[4] M.M.H Bhuiyan , M. Ali Asgar -Sizing of a standalone photovoltaic
power system at Dhaka Renewable Energy 28 (2003) 929–938
Science Direct
[5] Vinod kumar Sharma Antonio Colangelo- Photovoltaic Technology:
Basic Concepts , Sizing of standalone PV system for Domestic
applications and Preliminary Economic Analysis Vol. 36, No. 3, pp.
161-174, 1995 Elsevier Science Ltd
[6] Mohanlal Kolhe, Sunita Kolhe, J.C Joshi-Economic viability of
standalone solar PV system in comparison to diesel power systems
in India
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