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Which are the factors to be considered while buying energy storage systems?

Basics 101 : Understanding Specifications of Storage Tower (also known as AC Coupled or Retrofit Inverter)  

Home Owner if you use Path to Green Homes, you will be able to choose the right equipment and get a quote from your nearest installer. We don’t stop at recommending brand names e.g. How is LG? PathToGreenHomes helps you drill down to matching series and model e.g. 1Φ (4-5kW) RESU Series with 5kW AC Power.  

Below is the specification of storage tower which you will find commonly in data sheet, installation and warranty manuals. 

Manufacturer  Choose Brand or Manufacturer name Installer near you
Series Inverter Series are group of related products   Send Enquiry
Model Part number is followed by the inverter AC power and phase (1Φ / 3Φ) for ease of selection Send Enquiry
Datasheet Values  Send Enquiry
AC Power (KW) AC output power e.g. 5KW inverter for 5KW household load Send Enquiry
Battery Capacity (kWhr)  Storage Towers may have inbuilt or approved 3rd party battery makes. The battery capacity maybe expandable later by Paralleling  “No of Parallel Battery w/o addn devices” or series “See Battery Voltage”   Send Enquiry
Inverter type Grid type connect only with solar panels. Hybrid connects with both panel & battery. Storage Tower connect only with battery  Send Enquiry
Backup Overload ( kW)  A 5KW inverter should work >5KW for a small “time period (secs)” to accommodate surge loads like aircons , motor, pump etc. Send Enquiry
Overload (secs)A 5KW inverter should work >5KW for a small “time period (secs)” to accommodate surge loads like aircons, motor, pump etc. If Overload ( secs) is ZERO (0), it means that Backup overload load is not possible.   Send Enquiry
PhasesA household can be Single or Three phase. Most Three phase inverters already feature unbalanced load and they can deliver 5KW  across 3 phases as follows 0.5KW, 1KW, 3.5KW Send Enquiry
Solar Panel compatibility  Send Enquiry
Max Allowed Input  Current  from PV per  String NA. AC Coupled / Storage Tower cannot be connected to solar panels  Send Enquiry
Input MPPTs  ( nos )  NA. AC Coupled / Storage Tower cannot be connected to solar panels  Send Enquiry
PV String Level Monitoring NA. AC Coupled / Storage Tower cannot be connected to solar panels  Send Enquiry
Country  Country of Origin is HQ for manufacturer irrespective of place of assembly  Send Enquiry
Round Trip Efficiency  Round Trip efficiency in AC Coupled / Tower is the final efficiency after all losses including battery charging and battery discharging loss. Path to Green Energy has observed that many manufacturers are instead mentioning only the electronics efficiency not comparable to Round Trip Efficiency. Many  AC Coupled inverters do not have in built battery but require 3rd party compatible battery. So to arrive at Round Trip efficiency deduct battery charging and discharging loss ( 8%-12%).   Send Enquiry
Colour  Inverter colour is personal choice. However the quality of paint, C5 corrosion level are imp for longevity. In future plastic housing of inverters (to save cost) will make an arrival which need compliance to mechanical, electrical and tough EMI compliance Send Enquiry
Safety  Send Enquiry
 Lightning protection Type (DC)Type 1 = best, Type 2 = Good, Type 3 = standard.  
Very few inverters have an SPD fail alarm (LCD screen blinks) when it gets damaged due to surge.  
Send Enquiry
Lightning protection Type (AC)  Type 1 = best, Type 2 = Good, Type 3 = standard .  
Very few inverters have an SPD fail alarm (LCD screen blinks) when it gets damaged due to surge.  
Send Enquiry
Exchangeable SPDs  “Damaged SPD” can be part of an expensive board & need for replacement for both SPD and the expensive board. It may cost $100 for such replacement. Not very common but Path to Green Energy prefers equipment where only SPD replacement is possible.  Send Enquiry
Fuse for Battery ( Yes / No )  Standard features like “Reverse protection” and  “breaker” are basic safety but Battery Fuse, Soft Start is the real safety thingSend Enquiry
Dimensions  Compact is better. Liquid cooled models won’t be compact but very advanced technology.  Send Enquiry
Weight (Kg)Sometimes light inverter is better but not always. Some mfr leave a must “EMC filter” to make it lighter. Some top models add “liquid cooling” to add to reliability.  Send Enquiry
Send Enquiry
Battery Cycles Each time battery is discharged that’s one battery cycle. There are 365 days in a year and 10 years means 3650 cycles (100% charge and discharge each day). Please ask supplier if can battery be fully discharged Or weather maximum 90% / 80% of discharge is recommended since it has price implication  Send Enquiry
Battery Voltage (V) High Battery voltage reduces losses. As the household load increases (EV, Heat Pump), storage capacity maybe increased (not all inverters allow it) by adding more batteries in Series.  
Note : However not all brands will allow battery capacity addition, by mixing an existing (Old battery) with a new one. For them such mismatch is unacceptable
Send Enquiry
Parallel Batteries w/o addn. device  Storage capacity may later be increased, by adding batteries in PARALLEL instead of Series. No of units in parallel is an inverter feature to parallel batteries, without purchasing an additional data logger.   Send Enquiry
PV Oversizing (kW) We can connect 7kW solar panels to a lower rated 5Kw inverter. This is particularly advantageous in certain parts of Europe (such as Belgium). Send Enquiry
WarrantySend Enquiry
Electronics  Warranty (Years)  A 10-12 year warranty is at least recommended.   Send Enquiry
3rd Party Device CompatibilitySend Enquiry
Compliance to SunSpec Protocol  “Plug & play” interoperability for 100s of smart devices. Send Enquiry
Weather data integration Intergrate 3rd party reliable weather data from MetroControl / Skytron/ SolarLog useful for PV Energy prediction. 
In a EV scenario  regional meteorological data can create a generation forecast, which it compares against your own consumption behaviour.  
Send Enquiry
Smart Heat Pump Heat pumps operate directly from solar which is the cheapest energy source  Send Enquiry
Wireless connection Communication between devices through the local area network will reduce the complexity of system wiring.  Wireless connection is more beautiful, but the complexity of the initial configuration increases. Send Enquiry
Futuristic RequirementsSend Enquiry
Smart EV Charger  In General EV Charger can integrate in any PV grid. However this requirement is “Yes” when an Electric vehicle can be charged quickly, in a PV-optimized or forecast-based manner. The solar power should fully feed the car and not the grid.   Send Enquiry
Smart inverter Mainly required right now in the USA. It’s the ability to participate as an Interoperable PV Inverter with advanced Grid-Support Functions as Distributed Energy Resource (DER)  Send Enquiry

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