A case study of a 400 W, small roof top stand alone solar PV system in India

1. Small Residential Stand Alone
Roof-top Solar PV System:
A Case Study
By: Manoj Nair,
M-Tech. (H.E.E.)

2. Why Renewable ?
 Demand for electricity in India is increasing day by day,
doubles every 7 years.
 Gap between demand and supply,
 Limitations of Large scale Mega Power Plants;
• Financial issues,
• Govt. clearances,
• Gestation period; 5 years to 10 years
• Environmental issues,
• Limited availability; to exhaust in near future etc.
 Significant T & D losses; excess of 30%

3. Why Solar PV?
• Free and Abundant sunlight;
average 5 hours, and 300 days per years.
• Long Life of PV panels;
25 years
• Pollution free and Minimum Maintenance,
• Fast response and reliable,
• Modular units, easy scope for future expansion,
• Inherent short circuit protection,
• No T & D losses for small Roof Top PV plants
• Low Gestation periods

4. Potential of Roof top Solar PV System
 As per census 2011, India has 140 million houses with
proper Roof Tops.
 Roof Top Solar PV Systems (RTPV) is best suited for urban
areas where the houses are crowded and dense.
 Roof top stand alone PV systems can be installed with in
a few days (2-3 days)
• Stand alone PV system is directly connected to the load
through an inverter of appropriate capacity,
• Excess energy is stored in a battery of user defined
capacity for use in emergency period,
• In a grid tied system, excess energy produced is returned
to the grid if net metering facility is available in the area.

5. Key Elements of Stand alone Roof top Solar PV
System
• Solar PV
panels,
• Charge
controller,
• Battery,
• Inverter,
• Cables,
• Switches etc.

6. Role of Charge Controller
• A Charge controller protects the battery from
overcharging, moderates the charging at the end of
the charging cycle,
• It indicates the charging status of the battery such as
undercharge, overcharge, or deep discharge through
indicators.
• IGBT or MOSFET technology is used now a days
which reduces the idle current of the charge
controller

7. Role of Battery & Inverter
• Battery is used to store the excess energy produced.
• The cost of a battery is significant, hence there use
should be kept at an optimal value.
• Inverter is used to convert the DC output of the
battery/solar PV panel into AC of 230 V, 50 Hz.
• Care should be taken while selecting the inverter. An
inverter with sine wave output should be adopted as a
sinusoidal AC supply will increase the efficiency and life
of your electrical appliances.
• Wires of appropriate size should be selected to avoid un-
necessary voltage drop and power loss as wires of lesser
cross section will have higher resistance, increasing the
voltage drop and losses.

8. Check whether your house is suitable for the
solar PV system?
• It is very important to assess the amount of sunlight
available at the location where a solar PV system is
being installed.
• To collect maximum sunlight the ideal orientation of
a solar panel is towards south. However a 45-degree
east or west of south can also work.
• The system should be placed in such a place so that
there is no obstruction of trees or adjoining building.
• Roof should be of RCC to bear the weight of the solar
PV system.

9. Sizing a roof top solar PV system
• It is very important to size your solar system properly.
• Sizing will depend on the load requirements in your
setup. Solar system is good for operating low wattage
appliances like lights, fans, TV, etc.
• It is not advisable to operate High wattage appliances
like Air Conditioners, Microwave Ovens and Water
Heaters on a solar PV system (in fact solar water
heaters and solar air conditioners are available
separately).
• The connected load of your setup will help you
determine the size of system that you need and that in
turn will drive the cost of the system.

10. Primary Designing of a Roof top Solar PV system
• Collection of Information/Data; wattage of electrical
appliances, duty cycle, load profile, monthly electricity consumption
& bill, cost of panels, battery, inverter etc.
• Load Selection; load to be placed on solar PV system should be
selected
• Sizing solar array,
• Deciding battery capacity,
• Selection of Charge controller,
• Deciding of Inverter capacity,
• Structure,
• Wiring

11. Load / Energy Calculation
Load of Equipment in Watts x No. of working hours per Day
gives the Watt Hours Per Day (WHPD)
To calculate the Ampere Hours Per Day (AHPD)
AHPD = WHPD/(Av. Power Factor of the load x System Voltage)
Average Power Factor of the load to be connected to the solar PV system is
taken as 0.8 lagging in this study.

12. Capacity of Solar PV Panel
• The Solar PV Panel will supply to your electrical load
through the inverter as well as will charge your battery.
• If the electrical load on the panel is more it will provide
less current to the battery, thus battery charging will be
slow.
• So simultaneous calculation is necessary.
• The max. current of a 100 W PV panel is 5.8 A,
considering that a single panel is giving a current of 5 A,
the calculations were carried out.
• If you are running an electrical load of 200 W on the solar
system i.e. using the output of 2 panels, only 2 panel
outputs i.e. 10 A will be available for battery charging.

13. Charging Current of Battery
Charging Current
200 Ah 20 A
165 Ah 16 A
150 Ah 15 A
135 Ah 13.5 A
100 Ah 10 A

14. 400 W, stand alone solar PV
system: Case study

15. Introduction of the premises
• The premises which is considered for case study is a 3
BHK Duplex house located near Minal Residency, Bhopal.
• The total connected load is 7.7 kW and the details are
given in next slide.
• Only Light and fan loads and other small loads as T.V.,
kitchen chimney, aquarium, water filter are considered as
the load which is to be shifted on solar system.
• The system capacity is so selected that the energy
produced by solar system can be directly utilized at the
max., i.e. battery storage should be min.
• Occasionally electric iron and water pump of ½ h.p. is
also used.

16. Connected Electrical Load of the Premises
• Total connected load of the premises is 7.7 kW
Light Load (8 x 40 W, T/L & 4 x 10 W, CFL ) 360 W
Fan Load (6 x 70 W Fan & 2 x 220 W cooler) 860 W
T.V. (CRT type) 150 W
Electric Water Geyser 2000 W
Microwave Oven 2200 W
Water Pump 375 W
Electric Iron 600 W
Kitchen Chimney 190 W
Mixer/ Juicer 600 W
Fridge 110 W
Washing Machine 450 W
Acquarium 120 W

17. Loads to be put on solar..
• So the average connected electrical load of any middle
class residential house comes between 5 to 8 kW.
• It is never advised to take the full electrical load on
solar PV system; as it will-
• Increase the initial investment,
• Payback period will be too long.
• In this case electrical loads such as water geyser, water
pump, microwave oven, washing machine etc are still
grid connected.
• In this case electrical loads such as T/L, fans, coolers,
kitchen chimney, water purifier, etc of 1680 W are put
on solar system.

18. Solar PV panels

19. Solar PV Panel
Solar PV panels
Make: Topsun,
Gandhinagar, Gujarat.
Cap: 100 Wp, x 4 nos.
Warranty: 25 years
(conditions apply)
* Output of solar panel
reduces by 2.5 to 3.5%
during the first year, then
after a min. reduction of
0.7% per year [3]

20. Nameplate details of PV panel
• Max Output = 100
Wp per panel,
• Max voltage = 18 V,
• Max current = 5.8 A

21. End Terminals
• End Terminal Box,
• Connecting leads,
• (parallel connections
so that output is 18 V
and current 5.8 x 4 A)

22. Rear view of the panel

23. Supporting Structure
• MS Iron angle of
appropriate size
painted with ‘Al’
paint.

24. Solar Charge Controller
Solar Charge Controller
• Make: RXL,
• Cap: 40 A, 12 V,
• Warranty: 1 year,

25. Solar Battery
• Tall tubular Lead-Acid
battery
• Make: Luminous,
• Cap: 150 Ah, 12 V,
• Warranty: 5 years

26. Inverter
• 850 VA, 50 Hz,
Sine-wave
Inverter
• Make: Su-Kam

27. Change Over Switch
• Simple Switch
used as Change
Over Switch
• Make: Anchor
* This simple switch is a
key element
responsible for the
scheduling

28. Technical Details of the Solar PV System
System capacity:
 PV panel = 100 W x 4 Nos,
 Charge Controller ; 40 A
 Battery; 150 Ah, 12 V, Tubular Lead-Acid,
 Inverter; 850 VA, sine wave
 PVC insulated stranded ‘Cu’ wires of 4/2.5 sq.mm

29. Cost of installing the Solar PV system
Sr. No Component Cost (INR)
1 Solar PV panel, 4 x 100 W, Topsun Make 20,000.00
2 Charge controller, 40 A, 12 V, RXL Make 1,300.00
3 Battery, 150 Ah, 12 V, 5 yr warranty, Luminous Make 14,500.00
4 Inverter, 850 VA, 220 V, 50 Hz, sine wave, Su-Kam Make 5,500.00
5 ‘Cu’ stranded wires 4/2.5 sq.mm and switches 3,000.00
6 M.S. angle painted frame 2,000.00
7 Installation & Transportation Charges 2,000.00
8 Misc. Cement, sand, metal etc 7,00.00
8 Total 49,000.00

30. Scheduled Load on Solar System
• Of the total connected load, equipments of 1680 W,
with diversity factor of 4, are connected manually to
the solar PV/ Battery system.
• Three schedules were followed till date:
• 5.30 AM to 6.30 PM (May to July 2015)
• 5.30 AM to 5.00 PM (Aug to Sep 2015)
• 10.00 PM to 5.00 PM (Nov 2015)
* The above schedule are purely tailor made depending on the
seasonal variation and individual use which anybody can do.

31. Ref
1. Govt. of India, Ministry of Railways, “Handbook on installation and
Maintenance of Solar Panel”, RDSO, Gwalior.
2. Shanmugawalli K.R., & Veedamuthu R, “Viability of Solar Rooftop PV
Systems in Group Housing”, Current Science, Vol. 108, No.6, March 2015.
3. Tata Power Solar, “Warranty Document”.
4. Su-Kam, “Solar Batteries”

32. Any ?????

33. Thank You,
Have a Nice Day