5 Must-Have Features in a Power Storage Systems

1

.

ESS Introduction & Features

In this section

:

What is ESS?

An Energy Storage System (ESS) is a specific type of power system that integrates a power grid connection with a Victron Inverter/Charger, GX device and battery system. It stores solar energy into your battery during the day for use later on when the sun stops shining.

It allows for time-shifting power, charging from solar, providing grid support, and exporting power back to the grid.

When an ESS system is able to produce more power than it can use and store, it can sell the surplus to the grid; and when it has insufficient energy or power, it automatically buys it from the grid.

In the ESS system, there must at least be one inverter/charger and also a GX device such as:

Other components can be added when needed; see chapter 2.

Note: The information contained in this ESS manual does not apply to the Multi RS models, which use a VE.Can interface (not VE.Bus); see the RS product manuals for specific information on programming them for ESS.

When is it appropriate to use ESS?

Use ESS in a self-consumption system, a backup system with solar, or a mixture of both: For example, you can use 30% of the battery capacity for self-consumption and keep the other 70% available as a backup in the event of utility grid failure.

Optimizing self-consumption:

When there is more PV power than is required to run loads, the excess PV energy is stored in the battery. That stored energy is then used to power the loads at times when there is a shortage of PV power.

The percentage of battery capacity used for self-consumption is configurable. When utility grid failure is extremely rare, it could be set to 100%. In locations where grid failure is common - or even a daily occurrence - you might choose to use just 20% of battery capacity and save 80% for the next grid failure. African countries for example.

Keep batteries 100% charged:

ESS can also be configured to keep the batteries fully charged. Utility grid failure is then the only time battery power is used - as a backup. Once the grid is restored, the batteries will be recharged either from the grid or from solar panels - when available.

ESS in a system with a generator

Configuring ESS in a system which uses a diesel generator as backup - for extended mains failures - can be achieved. Grid code and Loss of Mains configuration will need special attention; see here.

And on the GX device, select 'Generator' as the AC Input type in the Settings → System setup menu. The system will then enable generator charging; ensure that the generator is properly loaded, and will be automatically switched off as soon as parameters are met.

When not to use ESS

• Off-grid systems - either with or without generator.

• Marine systems.

• Automotive systems.

• Inverter priority, also known as 'Intentional islanding“ or 'Ignore AC' input systems.

With and without grid-meter

ESS can be used both with an external grid meter or without one.

Where there is a grid meter; either a full or partial grid-parallel system can be configured to run alongside.

Where there is no grid meter; all loads are connected to AC-out. And where there is a PV Inverter present that is also connected to AC out.

Optional feed-in of MPPT Solar charger power

Power from an MPPT can be fed back to the grid. Enabled/disabled by a user setting on the CCGX: Settings → ESS.

Fronius Zero feed-in option

By using the Power Reduction feature in Fronius grid-tie inverters, the ESS system can automatically reduce the output of the installed PV Inverters as soon as feed-back is detected; without switching and frequency shifting.

It is not possible to combine ESS with the Fronius Smart Meter - but it's not necessary either, as ESS already has metering.

With ESS, it is not possible to disable feed-in a system with other brands of grid-tie inverters. See Chapter 2.1.2 for more information.

ESS Training

Energy Storage System introduction, examples and diagrams

A separate document that provides further introductory information, overviews, and system examples is available to download here.

Advanced control options

See ESS mode 2 and 3.

1.1

.

Let's look at the following example installations:

• Residential scale Energy Storage System with MPPT Solar Charger

• Retrofitting an existing Grid-tie inverter installation

• System with Generator backup (using the generator auto start/stop feature in the GX device)

Backup system with Solar

All loads are wired on the AC output of the inverter/charger. The ESS mode is configured to 'Keep batteries charged'.

When using a grid-tie inverter, it is connected to the AC output as well.

When grid power is available, the battery will be charged with power from both the grid and the PV. Loads are powered from PV when that power source is available.

Feed-in is optional and can be enabled or disabled depending on local regulations.

1.2

.

Components

Inverter/charger

• The Energy Storage System uses a MultiPlus or Quattro bidirectional inverter/charger as its main component.

• Note that ESS can only be installed on VE.Bus model Multis and Quattros which feature the 2nd generation microprocessor (26 or 27). All new VE.Bus Inverter/Chargers currently shipping have 2nd generation chips.

• The Multi RS is currently excluded and does not yet support ESS.

GX device

• The system is managed by the GX device, which also provides extensive monitoring, both locally and remotely via our VRM Portal and the VRM App.

Battery

Victron Lithium batteries

• Lithium Battery Smart 12,8V & 25,6V

Third-party battery compatibility

Please see this list of third-party batteries with which Victron equipment is compatible:

• Battery Compatibility

Lead batteries: OPzS and OPzV

• The relatively high internal resistance of these types of batteries should be considered when designing a system that uses them.

Lead batteries: AGM / GEL

• Note that the use of standard AGM and GEL batteries is not recommended for installations designed to cycle the battery bank every day.

Battery Monitor

In most situations, it is not necessary to install a battery monitor:

• Lithium batteries with canbus connection (BYD B-Box, Pylon, LG Resu and others) already have a built-in battery monitor. Adding another will only set up a conflict. Always use the canbus connection to provide battery status/state-of-charge data for these batteries.

• Redflow ZBM / ZCell zinc-bromide flow batteries with the ZCell BMS also support the same canbus protocol. This is the preferred integration approach for these batteries.

• The built-in battery monitor of the Multi Inverter/Charger can be used to provide data where installed batteries do not have a monitor built-in. The advantage here is that in an ESS system the charge currents from MPPT Solar Chargers will also be taken into account.

The only situation where an external battery monitor is required is when a system using a no-monitor battery type also has additional power sources: for example, a DC wind generator. (No monitor battery types include lead batteries, for example, or Victron 12.8V lithium batteries.)

Where an additional battery monitor is necessary, use one of these:

• BMV-700

• Lynx Shunt VE.Can

Detailed information is available in the CCGX manual chapter 5.2.

Grid Meter (optional)

An Energy Meter can be installed in the main distribution panel between the grid and the installation for a full or partial grid-parallel installation.

A grid meter is not required where there is no AC renewable-energy source(s) and also no AC load(s) present on the  input side of the Multi/Quattro system (i.e. where all such sources and loads are on the output side of the Multi/Quattro system).

If there is any AC renewable energy source or any AC load between the grid connection point and the input side of the Multi/Quattro system, incorrect results will be calculated and recorded by the GX unless a grid meter is installed and enabled.

In particular, without a grid meter:

• When renewable energy is being provided on the input side, the grid value will be wrong (too low/negative); and

• The AC Load value shown will be too low (and will show zero where there is a surplus of renewable energy).

Both issues are resolved by installing a grid meter.

Click here for more information about the configuration and selection of grid meters.

PV (optional)

• ESS can work with both Grid-tie PV inverters and/or MPPT Solar Chargers. (A mix of both is also possible.)

• When using Grid-tie PV Inverters we recommend monitoring is performed using the CCGX. See CCGX manual for the options.

• ESS can also be operated without PV. This is typical for virtual power plants, where the installation is part of a cluster of small storage systems - supplying energy to the grid during peak demand.

How does a battery storage system work?

A BESS collects energy from renewable energy sources, such as wind and or solar panels or from the electricity network and stores the energy using battery storage technology. The batteries discharge to release energy when necessary, such as during peak demands, power outages, or grid balancing. In addition to the batteries, BESS requires additional components that allow the system to be connected to an electrical network.

A bidirectional inverter or power conversion system (PCS) is the main device that converts power between the DC battery terminals and the AC line voltage and allows for power to flow both ways to charge and discharge the battery. The other primary element of a BESS is an energy management system (EMS) to coordinate the control and operation of all components in the system.

BESS Power and Energy Ratings

For a battery energy storage system to be intelligently designed, both power in megawatt (MW) or kilowatt (kW) and energy in megawatt-hour (MWh) or kilowatt-hour (kWh) ratings need to be specified.

The power-to-energy ratio is normally higher in situations where a large amount of energy is required to be discharged within a short time period such as within frequency regulation applications. For pricing purposes, however, the quoted measure is usually the energy rating.

What is the Battery C‐Rate?

A battery’s C rating is the rate at which a battery can be fully charged or discharged. For example, charging at a C-rate of 1C means that the battery is charged from 0 - 100% or discharged from 100 - 0% in one hour.

A C-rate higher than 1C means a faster charge or discharge, for example, a 2C rate is twice as fast (30 minutes to full charge or discharge). Likewise, a lower C-rate means a slower charge or discharge, as an example, a C-rate of 0.25 would mean a 4-hour charge or discharge.

The formula is:
T = Time
Cr = C-Rate

T = 1 / Cr (to view in hours), or T = 60 min / Cr (to view in minutes). For example:

C-Rate

Time