Design of solar pv system

1. What you’ll learn?
Design your own PV system

2. How Solar Power SystemWorks?

3. Design Steps a Solar PV System for Your
Home
A solar PV system design can be done in five steps:
• Step 1: Calculate energy consumption of appliances
• Step 2: Calculation of inverter sizing
• Step 3: Calculation of battery bank
• Step 4: Calculation of number of PV panels
• Step 5: Solar charge controller sizing
Cost calculation of the solar PV system

4. Step 1: Calculate energy consumption of
appliances
• We want to know how much electricity is consumed by an appliance in a day?
• Energy= Power × Duration of use (hours)
• LED bulb electricity (or energy )consumption per day
10 W ×10 Hr every day= 100 Whr every day
• LED bulb electricity (or energy )consumption per month
10 W ×10 Hr /day ×30 days=3000 Whr/month
Calculate the electricity consumption of all appliances per day and per month?

5. List of appliances electricity consumption
S.No. Name of Appliance Power Rating
(W)
Per day usage
(hr)
Per day
Electricity
used (Whr)
Multiply the total appliances watt-hours per day times 1.3 (the energy
lost in the system) to get the total Watt-hours per day which must be
generated by the panel

6. Step2:InverterSizing
• An inverter is used in the system where AC power output is needed.
• The input power rating of the inverter should never be lower than the total watt
appliances.
• The inverter size should be 25-30% bigger than the total watts of appliances.
• For standalone systems, the inverter must be large enough to handle the total amount
of watts you will be using at one time.
• In case of appliance type is motor or compressor, then inverter size should be minimum 3 times the
capacity of those appliances and must be added to the inverter capacity to handle the surge current
during starting.
• For grid connected systems, the input rating of the inverter should be same as PV array rating to allow for
safe and efficient operation.
• The inverter must have the same nominal voltage as your battery.

7. Step 3: BatterySizing
• The battery type recommended for using in solar PV system is deep cycle
battery.
• Deep cycle battery is specifically designed fro to be discharged to low energy
level and rapid recharged or cycle charged and discharged day after day for
years.
• The battery should be large enough to store sufficient
the appliances at night and cloudy days.
energy to operate

8. Step 3: Battery Sizing
To find out the size of battery, calculate as follows:
1. Calculate total watt-hours per day used by appliances.
2. Divide the total watt-hours per day used by 0.85 for battery loss.
3. Divide the answer obtained in step 3.2 by 0.6 for depth of discharge.
4. Divide the answer obtained in step 3.3 by the nominal battery voltage.
5. Multiply the answer obtained in step 3.4 with days of autonomy to get
the required battery sizing.
•Days of autonomy: the number of days that you need the system to
operate when there is no power produced by the panels

9. Step 3: BatterySizing
𝐵𝑎𝑡𝑡𝑒𝑟𝑦 𝐶𝑎𝑝𝑎𝑐𝑖𝑡𝑦 𝐴ℎ
=
𝑇𝑜𝑡𝑎𝑙 𝑤𝑎𝑡𝑡 − ℎ𝑜𝑢𝑟𝑠 𝑝𝑒𝑟 𝑑𝑎𝑦 𝑢𝑠𝑒𝑑 𝑏𝑦 𝑎𝑝𝑝𝑙𝑖𝑎𝑛𝑐𝑒𝑠 × 𝐷𝑎𝑦𝑠 𝑜𝑓 𝐴𝑢𝑡𝑜𝑛𝑜𝑚𝑦
0.85 × 0.6 × 𝑛𝑜𝑚𝑖𝑛𝑎𝑙 𝑏𝑎𝑡𝑡𝑒𝑟𝑦 𝑣𝑜𝑙𝑡𝑎𝑔𝑒

10. Step 3: Battery Sizing
Example
•Total appliances use
= (18 W × 4 hours)+(60 W ×2 hours)+(75 W ×12 hours)
•Nominal voltage of the battery = 12 V.
•Days of Autonomy = 3 Days
•𝐵𝑎𝑡𝑡𝑒𝑟𝑦 𝐶𝑎𝑝𝑎𝑐𝑖𝑡𝑦 𝐴ℎ =
(18 W × 4 hours)+(60 W ×2 hours)+(75 W ×12 hours)
0.85×0.6×12
× 3
• Total Ampere-hours required=535.29 Ah
• Therefore, the battery should be rated :12 V, 600 Ah for 3 Day
Autonomy

11. Step 4: Solar PV Sizing
=
• Solar radiation unit=kWh/m2/day
• At given location=5.5 kWh/m2/day
• Divide it by 1000 W/m2 (under STC)
• Hours of solar radiation=5.5 hours per day
• Power of solar panel
Total energy by solar panel per day
Hours of solar radiation per day

12. Step 5:Solar C harge Controller
• Its function is to regulate the voltage and current from the solar arrays
to the battery in order to prevent over charging and
also over discharging.
• The solar charge controller is typically rated against Ampere and Voltage capacities.
• Select the solar charge controller to match the PV array and batteries.
• Make sure that solar charge controller has enough capacity to handle the current
from PV array.

13. Design Example on off-grid solar PV system
sizing

14. Load Considered for our Example
Name of
Appliance
Number of
Appliances
Power Rating
(W)
Per day
usage
(hr)
Per day
Electricity
used (Whr)
Air Conditioner 1 2500 8 20,000
Lamps 5 60 12 3,600
Refrigerator 1 200 24 4,800
TV 1 200 2 400
Total Power 3,200 W
Or
3.2 kW
Total energy consumed 28,800 Wh
Or
28.8 kWh

15. Inverter Sizing
• Inverter size should be greater by 25 to 30% of load
• Therefore, minimum inverter sizing= 1.25 ×3.2=4 kW
• Considered efficiency =97%
• The inverter minimum input=96V
• As efficiency = 𝑜𝑢𝑡𝑝𝑢𝑡 𝑝𝑜𝑤𝑒𝑟
𝑖𝑛𝑝𝑢𝑡 𝑝𝑜𝑤𝑒𝑟
𝑜𝑟 𝑜𝑢𝑡𝑝𝑢𝑡 𝑒𝑛𝑒𝑟𝑔𝑦
𝑖𝑛𝑝𝑢𝑡 𝑒𝑛𝑒𝑟𝑔𝑦

0.97
• 𝑖𝑛𝑝𝑢𝑡 𝑒𝑛𝑒𝑟𝑔𝑦 = 𝑜𝑢𝑡𝑝𝑢𝑡 𝑒𝑛𝑒𝑟𝑔𝑦
= 28.8
= 𝟑𝟎 𝒌𝑾𝒉

16. Battery Sizing
• Consider the efficiency of battery with charge controller combined= 85%
• So input energy to charger and battery = 30 𝑘𝑊ℎ
= 𝟑𝟓. 𝟐𝟗 𝒌𝑾𝒉
0.85
• We need to consider days of autonomy where sun is not available
• Assume 1 day of autonomy
• 𝐵𝑎𝑡𝑡𝑒𝑟𝑦 𝐶𝑎𝑝𝑎𝑐𝑖𝑡𝑦 𝐴ℎ = 𝑇𝑜𝑡𝑎𝑙 𝑤𝑎𝑡𝑡−ℎ𝑜𝑢𝑟𝑠 𝑝𝑒𝑟 𝑑𝑎𝑦 𝑢𝑠𝑒𝑑 𝑏𝑦 𝑎𝑝𝑝𝑙𝑖𝑎𝑛𝑐𝑒𝑠×𝐷𝑎𝑦𝑠 𝑜𝑓 𝐴𝑢𝑡𝑜𝑛𝑜𝑚𝑦
0.85×0.6×𝑛𝑜𝑚𝑖𝑛𝑎𝑙 𝑏𝑎𝑡𝑡𝑒𝑟𝑦 𝑣𝑜𝑙𝑡𝑎𝑔𝑒
• DoD of battery=60%, each battery 200 Ah
• So Ah required= 3.67 kAh
12
• Number of series batteries=96
= 𝟖
8×200
• Number of parallel strings= 3670
= 2.29 = 𝟐

17. PV Module Sizing
• At given location=5 kWh/m2/day
• Divide it by 1000 W/m2 (under STC)
• Hours of solar radiation=5 hours per day
• Power of solar panel= Total energy by solar panel per day
Hours of solar radiation per day
= 𝟑𝟓.𝟐𝟗
= 𝟕 𝒌𝑾
𝟓
•PV panel available in the market: Pm=250 W, Voc=30V, Isc=8.3 A
𝟐𝟓𝟎
• Therefore number of PV panels = 𝟕𝟎𝟎𝟎
=28 panels

18. Solar Charge Controller Sizing
• Solar charge controller available in the market:3.8 kW
• With specifications of 96 V and 40 A
• Two solar charge controllers gives: 7.6 kW
• First group: 4 series and 4 parallel which gives 16 panels
• Total current=4 ×8.3=33.2 A
• Total voltage=4 ×30=120 V
• Second group: 4 series and 3 parallel which gives 12 panels
• Total current=3 ×8.3=25 A
• Total voltage=4 ×30=120 V

19. 4 series and 4 parallel 4 series and 3 parallel
Battery bank Inverter Loads