Frequently Asked Questions
(a) Stand Alone System: It is off grid solar power plant which are further of two types
(i) Stand Alone System with Battery Bank and
(ii) Stand Alone System without Battery Bank
(b) Grid Connected SPV Plant: It is grid connected solar power plant which are further of two types
(i) Grid Connected Hybrid System with Battery Bank and
(ii) Grid Connected System without Battery Bank
(c) Grid-Export System: It is a grid connected system with 100 % export to the Grid
(ii) Polycrystalline
(iii) Thin film/ amorphous.
A. Grid Export System Hybrid PCU( Grid Connected with battery bank):
Condition # 1:
SPV present, Grid available
Battery Charged through MPPT* charger + mains & Load supplied through Grid
MPPT – Maximum Power Point Tracker
SPV – Solar Photo Voltaic
Condition # 2
PV available, Battery charged, Grid available surplus power exported to grid connected loads
Condition # 3
SPV not available, Grid available,
Battery charging through Mains
Condition # 4
SPV not available, Grid OFF,
Inverter supplying power to grid connected loads through Battery
Condition # 5
SPV & Grid not available
Battery discharged. Start DG command
Battery charging through DG
B. Grid-Connected Power Plant (Having Net Metering facility)without battery bank:
Condition # 1:
PV present, Grid available
Load supplied through PV upto level of PV and draws more if required from Grid
Condition # 2
PV available, Grid available
If load is less then PV available then surplus power exported to grid
Condition # 3
PV not available, Grid available,
Load supplies from Grid.
Condition # 4
PV available, Grid Not available
The power plant will not work
Advantages of A Hybrid System (Grid Connected with battery bank):
•High level of reliability to Battery bank.
•Lesser battery discharge and hence longer life of battery.
•Reduced electricity bills.
•Highly reliable system and can be used in wide range of URBAN/Industrial/Institutional application. Also improves the quality of AC power and can be called solar UPS.
Limitations of a Stand-Alone (Off Grid Plant):
•High Cost.
•High cost on maintenance
•Works on battery charge-discharge leadings to:
•Wastage of precious PV power generated.
•Reduced battery life.
•Worst performance when used with VRLA Battery
•Does not ensure optimum yield from PV panels.
•Thus stand-Alone system is suitable only for RURAL where AC Power is not available at present and is not likely in near future.
Advantages/Disadvantages of Grid-Connected Power Plant without battery bank:
Advantages:
•High conversion efficiency of PV Power into usable AC power
•Simple system with longer life i.e. no battery life issue.
Disadvantages:
Works only when grid power is available.