Grid-Tie with Battery Backup
Residential
Commercial
Industrial / Utility
AC Coupled
DC Coupled
Grid powers main panel; renewables power sub-panel
Solar energy is never fed to the grid
Grid is present as a backup
Simplified FDO Manufacturing Flow with TPMs _ Liam at Infineon.pdf
Solar & Battery presentation
1.
2. About Iron Edison
• 7+ years of battery system and battery-
based solar PV system design experience
• 500+ battery systems sold
• Working with 1,400+ Partners across the
country to successfully install and
commission battery-based systems
3. Battery-Based Solar PV Systems
• Grid-Tie with Battery Backup
• Residential
• Commercial
• Industrial / Utility
• AC Coupled
• DC Coupled
• Grid Backup
• Typically Residential
• DC Coupled
4. Grid-Tie with Battery Backup
• Operates like a Grid-Tie system most of the time
(when the grid is online)
• Critical loads are backed up (when the grid is down)
PV array
inverter/
charger
AC service
panel
AC utility
meter
grid
charge
controller
battery
inverter
AC distribution
panel
5. Grid-Tie with Battery Backup
Normal operation (day)
PV array
inverter/
charger
AC service
panel
AC utility
meter
grid
charge
controller
battery
inverter
AC distribution
panel
6. Grid-Tie with Battery Backup
Normal operation (night)
PV array
inverter/
charger
AC service
panel
AC utility
meter
grid
charge
controller
battery
inverter
AC distribution
panel
7. Grid-Tie with Battery Backup
Grid is down (day)
PV array
inverter/
charger
AC service
panel
AC utility
meter
grid
charge
controller
battery
inverter
AC distribution
panel
8. Grid-Tie with Battery Backup
Grid is down (night)
PV array
inverter/
charger
AC service
panel
AC utility
meter
grid
charge
controller
battery
inverter
AC distribution
panel
9. Grid-Tie with Battery Backup
Grid is down (day)
• Like Grid-Tie inverters, Battery-Based
inverters have an anti-islanding feature
• An internal automatic transfer switch (K1, K2)
prevents back-feeding to the grid
• The automatic transfer
switch also allows either
AC1 (grid) or AC2 (gen)
to be connected to the
inverter input, but not
both simultaneously
10. Grid Backup
PV array
inverter/
charger
AC service
panel
AC utility
meter
grid
charge
controller
battery
inverter
AC distribution
panel
• Grid powers main panel; renewables power sub-panel
• Solar energy is never fed to the grid
• Grid is present as a backup
14. AC Coupled
• Allows for Grid-Tie solar retrofit
• Does not allow for Grid Backup system set-up
PV array
battery-based
inverter/
charger
main panel
AC utility
meter grid
battery
sub-panel
GT inverter
18. AC Coupled
PV array
battery-based inverter/ charger
sub-panel
GT inverter
AC1 =
connection to
main panel
K1 opens
Grid is down: the battery-based inverter is
responsible for the anti-islanding feature
19. • Lead Acid (sealed/AGM)
– No maintenance
– No off-gassing
– ~1,500 cycles at 30% DOD
• Lead Acid (wet/flooded)
– Regular maintenance (watering)
– Off-gasses hydrogen gas
– ~2,000 cycles at 30% DOD
Battery Types - conventional
20. • Nickel Iron
– Regular maintenance (watering)
– Irregular maintenance (electrolyte refresh)
– Off-gases hydrogen gas
– 11,000+ cycles at 80% DOD
• Lithium Iron Phosphate
– No maintenance
– No off-gassing
– 5,000+ cycles at 50% DOD
Battery Types - alternative
21. • Long life
– 11,000 cycles at 80% DOD
– Batteries cycled daily last over 30
years (11,000 ÷ 365 = 30.1 yrs)
• Deep discharge
– 80% recommended DOD
– More useable capacity than most
other battery types
– Deep discharge has no negative
impact on batteries
Nickel Iron
• Nearly indestructible
▫ Operating temperature range: -22°F through 194°F
▫ Tolerant of over-charge and over-discharge
▫ The battery’s alkaline electrolyte acts as a metal preservative
22. • Ideal for solar storage
– C/5 charge rate works well with average 5 peak sun-
hours
• Compatible with most major brands
– Magnum Energy, Schneider Electric, OutBack Power,
MidNite Solar, SMA (Sunny Island)
• High charge voltage
– Charges at 1.65 Volts per cell
– Drop a cell when charging from inverter/charger
Nickel Iron (continued)
23. • Safest lithium chemistry
– LiFePO4 is chemically stable
• Active cell management
– Battery Management System
(BMS) included
• High energy density
• Efficient (95%)
• Compatible with most
major brands
• Cycle life affected like lead
acid
Lithium Iron Phosphate
Editor's Notes
FYI this is a DC COUPLED architecture. Let’s start with the concept and revisit DC Coupled VS AC Coupled later.
Residential and Commercial systems operate in the same way
Batteries are kept topped off and solar energy mostly goes to loads or grid
Inverter AC distribution panel loads are fed by grid when battery reaches certain pre-programmed setpoint (can be high voltage-FULL or lower voltage – we can revisit Grid BACKUP concept later)
Just like a GT inverter, Battery-Based inverters have an anti-islanding feature and internal automatic transfer switch
Depending on the size of your battery, your inverter’s AC distribution panel could remain powered to last through the night or more.
Just like a GT inverter, Battery-Based inverters have an anti-islanding feature and internal automatic transfer switch
PROs = lessen the burden on the grid’s infrastructure (typically incurred with GT systems)
CONs = ‘masked’ loads
If loads on inverter AC distribution panel are less than available power from DC sources, then net excess power from DC source is not converted and NOT exported to the grid
‘masked’ loads – the utility is unaware of loads on the inverter AC distribution panel that are typically powered by the renewable energy system; demand and consumption at the residence in a ‘Low Batt’ scenario are higher than what the utility expected
Image is flipped
GT inverter immediately disconnects (anti-islanding feature) and BB inverter AUTOMATICALLY starts powering critical loads. It takes 5 minutes for the GT inverter to reconnect after the BB inverter starts mimicking the grid signal.
Image is flipped
The battery is the HEART of the battery-based PV system
Off-gassing store in vented battery box with vent fan
The battery is the HEART of the battery-based PV system
Nickel Iron = Alkaline Chemistry; Electrolyte = potassium hydroxide with lithium hydroxide; Nickel Iron is also a lot more ROBUST
Solar as a charge source: 3-stage charging (bulk, absorb, float) / Grid or Gen as charge source: 2-stage charging (bulk, absorb)
More sensitive to over-charge and over-discharge
More similar to Lead acid cycle life = 2,000 cycles at 80% DOD
