This document summarizes a student's project on optimizing the cost of a roof-top solar power plant connected to the electric grid for residential use. The student analyzed: 1) Minimizing the home's electricity bill by using solar power during the day and storing excess in batteries for night, drawing from the grid as needed. 2) Maximizing the investment return over the system's lifespan by calculating the present value of savings from lowered electricity costs versus installation costs. 3) The results showed optimizing solar panel size and battery capacity could reduce the electricity bill by over $500 per year. Newer, cheaper technologies could provide a positive return on investment for a 25 panel, 8 kWh battery system.

1. PRESENTATION PREPARED BY
SYED AJMAL KHALIL
STUDENT OF M.TECH SAE
UNDER THE GUIDANCE OF
DR. MAHESH KUMAR (SUPERVISOR)
LATE. DR. BARNAMALA SAHA (CO -SUPERVISOR)
ROOF TOP SOLAR PLANT CONNECTED TO
GRID FOR RESIDENTIAL PURPOSE AND COST
OPTIMIZATION

2. TOPICS
 ABSTRACT
 INTRODUCTION
 OBJECTIVE
 METHODOLOGY
 RESULT AND DISCUSSIONS
 REFRENCES

3. ABSTRACT
 PV systems on residential place are developed to mine energy from solar
power systems and convert into electricity either come up with storage using
battery or grid connected facility.
 Solar power plant and the DC power generated from solar photovoltaic panel is
converted to AC power using solar grid inverter.
 The generated ac power can be fed to grid during day time when the usage is
not as much as per load and in night when solar power is not sufficient to fulfill
the requirement, loads are served by drawing power from grid.
 The components are selected on the bases of residential and rating
requirements .
 Costing analysis of the solar power plant is done to determine the sensitivity
parameters on levelized cost of energy (LCOE).

4. CONTINUED
 Solar power plant and the DC power generated from solar photovoltaic panel
is converted to AC power using solar grid inverter.
 The generated ac power can be fed to grid during day time when the usage is
not as much as per load and in night when solar power is not sufficient to
fulfill the requirement, loads are served by drawing power from grid.
 The components are selected on the bases of residential and rating
requirements .
 Costing analysis of the solar power plant is done to determine the sensitivity
parameters on levelized cost of energy (LCOE).

5. INTRODUCTION
 Solar energy is clean, pollution free renewable energy, District Srinagar of State
Jammu and Kashmir India being located at 34.0837° N,74.7973° .
 which receives average DNI(Direct Normal Irradiation) and GHI (Global
Horizontal Irradiation) received from last ten years varied from (1
kWh/day/m2 ) to (8kWh/day/m2 ) per day .
 Rooftop solar PV system can be with or, without having grid interaction , In
grid interactive system the DC power generated from solar PV panels is
converted to AC power using power conditioning unit .
 Generated power is given to the grid either of 11 KV three phase line or, of 220V
single-phase on the basis of the system that has installed at various places like
commercial buildings, residential complexes etc

6. Continued…

7. Continued…
 In case if the solar power is not able to fulfill the load requirement due cloud
cover, the loads are being provided with the power from the local grid as the
grid-interactive works on net metering basis only, the beneficiary pays to the
utility on net meter reading basis only .
 Grid-interactive systems do not require battery for backup as the local grids
serves as the backup in case of low generation by solar PV system.
 For reliability of the system at least one hour of the battery back should be kept
for any interruption in the power supply.

8. Continued..
 Components used in grid connected PV:-
 PV modules :- PV modules of 225 to 250 watts that consists of 60 cells that
are connected in series. Other modules are also available in the market with
higher power capacity, but the selection of 225 to 250W is mainly availability
and preferred due to cost optimization .
 Insulation cables: The electrical connections between any two components
can be done by insulating wires or cables, for pv system we need to select an
suitable wire /cable to reduce the voltage drop and power losses in cable.
 Inverter:-The AC power converted from the inverter must synchronize
automatically to the grid AC voltage and frequency. The design of an inverter
should be in such a way so that it can operate the PV system near its maximum
Power Point (MPP). co

9. Continued..
 Net metering: metering is a method or mechanism that allows domestic or
commercial users to generate their own electricity using solar panels or
photovoltaic systems in order to export their extra energy back to the grid.
 The process of net metering provides system owners with the opportunity to
gain extra income by selling the excess power to the utility or local grid hence
providing the energy to the local grid in the peak load hours.
 Junction boxes or combiners: Junction boxes are used for wiring and must
be able to withstand dust; water etc, even junction boxes of suitable rating
should be selected.
 Fuses of satisfactory rating must be provided in order to protect the solar
arrays from short circuit.

10. OBJECTIVE
 Cost optimization in terms of (Installation, Labor, Energy, Storage,
Real Time Pricing):-
 By minimizing equipment capital cost with lower material content, with lower-
cost materials and more efficient design, or it can be done with less expensive
manufacturing and shipping costs.
 By reducing installation costs (i.e.; with simpler designs and minimization).
 By lowering operation and maintenance costs with improved reliability,
automation, reducing need as with self-cleaning mirrors, and with better
techniques.
 By constructing larger systems that provide economy of scale, mainly in the
power sector.

11. METHODOLOGY
 To minimize the cost of energy which has to be delivered to a residential, commercial
purpose with this effect optimization can be determined i.e., how many solar collectors
and batteries (if any) are needed to provide lowest cost energy to the customer,
optimization evaluates the effect of changes in capitalized cost of the solar panels and
batteries.

12. METHOD FIRST
 Step 1:- Minimize Electricity Bill
 Fig. 1 shows electricity demand provided from three sources i.e; public grid, solar panels, and battery bank.
Dt=Gt +Pt + Bt
 The input energy is a function of solar irradiation and efficiency and the size of the solar panels So the
equation can be formed as
St × PVsize × Pveff = Pt + PCt + L (2)
• Stored energy in the battery (Et) is function of sum of the input energy (minus) the summation of the
output energy from the batteries up to the desired time.
Et = Et -1 + Beff × PCt-1 – Bt-1 + Eo
Et = (Beff ×PCi – Bi) + Eo=1
where
EO =the initial stored energy of batteries

13.  Taking into consideration, the real time price of the electricity and the amount of energy absorbed
from the grid at each time, and electricity cost for the period time of t is: t
C = (4)
 As we know the objective is to minimize the electricity bill for a specific period of time then Eqns. 2
and 1 will be rewritten as:
 Gt = Dt – PVsize × PVeff × St +Lt+PCt–Bt ( 5) Hence, objective function has been
minimized as;
 C = (Dt- PVsize× PVeff× St + Lt + PCt- Bt) × Ct) (6)
 Grid: power supplied from the grid, Gt is always assumed to be greater than zero. Which means that
all solar energy generated will either be consumed directly to loads or will charge the battery.
Therefore from Eq. 5 it states that:-
 Dt -PVsize × PVeff × St + Lt + PCt -Bt ≥ 0 (7)

14. METHOD SECOND
 The optimization has been observed for 72 hours, means system optimizes
available stored energy at time t and the predicted data for the next t + 72
hours.
 When the optimization is done the condition of the system will be fixed for the
time t and the next optimization will be from t + 1,… t+73.
 By this methodology we will let the system decide how to manage the flow of
energy.
 Step 2:Maximum Investment Return;
It is known that minimized electricity bill (C) calculated for a range of solar PV
area and battery capacity with optimal solar collector area for delivering lowest
cost energy over a particular time can be determined.

15. CONTINUED..
 Capital costs per area of solar collector and per kWh of battery capacity, inflation rate, and desired
interest rate from investment (assumed zero), the cash flow of the profit and cost in the life period of
the solar panels, the present value of the investment return is
P = (Pa , Fa ,I,a) (7)
 Net future value Fa for each year = (saved money - capitalized cost for the year). Capitalized cost of the
solar panels and batteries are also a function of their size and unit cost then result of present value for
each year is given as:
Capitalized costa= PVsizea * PVcosta + Bsizea * Bcosta
Saved moneya= f (PVsize, Bsize) (8)
 As a result, the net present value,
Pa (9)

16. RESULTS
 Electricity Bill Minimization : shows the price of grid supplied power which is high so
the system uses solar or stored energy to loads, and when the grid power price is low then
loads are powered by the grid and generated solar energy is used to charge the batteries.

17. CONTINUED…
• shows how to achieve optimized result for a year. As initially electricity bill was $1335
and then optimized cost came to $835 with optimal use of solar energy.
 Investment Return
The investment return is calculated for in view of battery technologies ,solar module
costs as the conditions of the case lower price of electricity and low solar irradiance in the
region with the high price of batteries and their short life span, for all the value of the size
of the batteries the investment return is negative.
• As the price of solar panels and storage systems have decreased , and latest technologies
for storage systems with longer life as first step towards maximum investment return can
be considered for with average price of the electricity about 0.23$ per KWh in
comparison with 0.15 $ in for residential users.
•

18. An example of investment return calculation for the new condition is illustrate in Fig.

19. CONTINUED…
 Implicit price per square meter of the solar panel and storage system with 13
years of life span were $750 and $400 respectively.
• Now as shown, matchless optimal result that exists, for 25 square meters of
solar area and with a 8 kWh storage capacity has given maximum investment
return at the end of solar panels' life is $9140.
• Fig also shows how different life span of storage systems the price per KWh has
to decrease to make this idea valuable.

20. DISCUSSIONS
 The performance design and installation of 8 kW roof top PV power system can
be analyzed, as total parameters of the system will be taken on real time basis
and the generated energy will be used for serving the increasing demand and
the remaining power will be injected into the grid.
 The existing systems display a way to optimize the cost of transferred energy to
end users if real-time pricing of the electricity has been put into practice. It is
assumed in this model that the current generation capacity is fixed and all
energy produced from the renewable source is stored locally and overall effect
shown by this optimization is that of peak clearing.
 However result showed up the overall money saved by each individual user the
society (utilities) will be potentially saved because of peak demand reduction
and decrease in need for peak capacity construction. The results showed how
the price of any storage system should decrease to make the solution economic.

21. REFRENCES
 Vol-5, Issue-1, Jan- 2018] https://dx.doi.org/10.22161/ijaers.5.1.10 ISSN: 2349-6495(P) |
2456-1908(O)
 O. Wasynczuk, Dynamic behavior of a class of photovoltaic power systems, IEEE
Transactions on Power Apparatus and Systems 102 (1983) 3031-3037.
 Vinay Janardhanshetty and Keerti Kulkarni, “Estimation of cost analysis for 500KW grid
connected solar photovoltaic plan: A case study”, International Journal of current
engineering and technology, vol 4, PP. 1859- 1861,No.3,June 2014.
 Pradeep Paleli and Harinichallapally,”Roof top solar and netmetering in India- A
Detailed Analysis”, PP.1-6, Efficientcarbon.com
 P. Karki, B. Adhikary and K. Sherpa, "Comparative Study of Grid-Tied Photovoltaic (PV)
System in Kathmandu and Berlin Using PV syst," IEEE ICSET, 2012.
 J.T. Bialasiewicz, Renewable energy systems with photovoltaic power generators:
Operation and modeling, IEEE Transactions on Industrial Electronics 55 (2008) 2752-
2758.

22. REFRENCES..
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MATLAB/SIMULINK, in: Proceedings of the World Congress on Engineering and
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 H. Patel, V. Agarwal, MATLAB-based modeling to study the effects of partial shading on
PV array characteristics, IEEE Transactions on Energy Conversion 23 (2008)302-310.
 O. Wasynczuk, Dynamic behavior of a class of photovoltaic power systems, IEEE
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THANK YOU