A solar inverter is essentially built like a grid-tie inverter which is capable of managing a battery bank.A hybrid inverter can operate like a grid-tie inverter fulfilling the same objectives, namely:
- Convert the DC energy generated by the solar installation into an AC energy compatible with the local network (230VAC / 50Hz in Europe). Indeed, the current generated by the solar installation cannot be used directly since it is a Direct Current, which varies depending on different factors such as solar irradiance, temperature, etc. … The hybrid inverter will therefore convert this direct current into Alternating Current with a voltage and frequency identical to those present int the outlets, allowing consumption or export of solar production.
- The hybrid inverter will synchronize its output signal with that of the grid to be able to inject the solar energy to grid.
- Each hybrid inverter has (or should have) an integrated anti-islanding protection. It is necessary for the hybrid inverter to stop injecting energy into the grid and physically disconnect itself from the network when it fails (in case of the grid failure or voltage and / or frequency which go outside a certain range). There is a European standard called “DIN V VDE 0126-1-1” which defines the rules for decoupling, and there are many other similar norms applicable in various geographical areas. The hybrid inverter therefore incorporates a relay which will open to decouple the inverter from the electrical grid if necessary.
In addition to these basic functions the hybrid inverter will:
- Store the excess production in an energy storage system (batteries) before injecting it into the public distribution network. The consequence is an increase in the self-consumption rate and the autonomy of the site.
- Use all the different sources of energy available on the site (PV array, battery, grid) when the energy demand is high. For example, for an instantaneous consumption of 3kW, if the solar panels produce only 1000W and the battery is able to provide only an additional power of 1000W, the public network will only provide the missing 1000W.
Please note, there is currently a large supply of inverters sold as hybrid inverters but which are in reality a type of an “all-in-one” off-grid inverter incorporating an inverter and a charger. The best way to know if you are actually buying a hybrid inverter is to make sure that it has the standard necessary for connection to the electric grid in your geographical area (for example DIN V VDE 0126 in Europe). If the inverter does not have this standard then it is an off-grid inverter.
Once you have verified that the inverter complies with the local grid code, you will also need to make sure that it is also equipped with a built-in backup output, which is used to supply a selected number of electrical devices in the event of a power outage.
Below is a diagram of an installation incorporating an IMEON hybrid inverter.
- Self-consumption with batteries on site connected to the electricity network, with or without backup
- Self-consumption without batteries on site connected to the electricity network, without backup
- Electrification of isolated, remote sites, with batteries
- Use of lithium or lead-acid batteries (gel, AGM…)
- Possibility of coupling with a diesel generator (see IMEON documentation)
IMEON hybrid solar inverters have many advantages:
- High yields
- Artificial intelligence integrated into IMEON 3.6 and 9.12
- ONE operating system integrated into IMEON 3.6 and 9.12
- Guarantees among the highest on the market
- Possibility of warranty extension up to 20 years
- Significant track record
Here are the different data provided by the manufacturers of hybrid inverters and a few things to check:
- Nominal output power: this value describing how much power your inverter can output continuously, given in watts (W) or in kilowatts (kW).
- Output voltage: communicated in V (volts) or Vac (volts alternating current). It is necessary to make sure that the selected inverter can synchronise with local grid in your geographic area.
- Max efficiency: this is the maximum conversion efficiency between the output of the solar panels and the output of the inverter (direct consumption).
- Maximum DC voltage: communicated in V (volts) or Vdc (volts direct current), this is the output voltage of the solar array which should not be exceeded. When sizing the installation, one must take into account the specifications of the solar panels (don’t forget the temperature coefficients) to define number of panels which can be coupled with the inverter.
- Maximum DC current: communicated in amperes (A), this is the current produces by the solar array, measured on the solar panel input of the inverter.
- MPPT voltage range: communicated in V (volts) or Vdc (volts direct current), this is the solar array’s voltage range within which the inverter is able to generate electricity. When sizing the installation, one must ensure that the panels will be able to supply a voltage within this range during operation.
- Start-up voltage: communicated in V (volts) or Vdc (volts direct current), this is the voltage from which the inverter is able to generate electricity. When sizing your installation, you must ensure that the panels will be able to output the voltage higher than this value.
- Max charge current: this value is given in A (amps). It is important to make sure that this value is consistent with the nominal output power of the inverter. For example, for a 3kW inverter, it is appropriate to have a charging current of 60A for a 48V battery bank at nominal voltage because, in this way, it is possible to charge almost all of the instantaneous production into the batteries. If the charger is undersized then there is a risk of losing a part of the energy generated by the array.
- Maximum discharge current: this value is given in A (amps). It is important to make sure that this value is consistent with the power of the inverter. For example, for a 3kW inverter, it is appropriate to have a discharge current of 60A for a bank of 48V batteries at nominal voltage because, in this way, it is possible to supply all of the power drawn by the inverter from the battery and therefore avoid drawing energy from the grid.
- Nominal voltage of the battery bank or range of battery voltage: expressed in V or Vdc, it gives an idea of the configuration of the battery bank to be considered according to the batteries selected (48V modules or 12V batteries, 6V, 2V, in series or in parallel…).
- Transfer time: this data is communicated only for inverters with a back-up function. This is the time required to switch from network connected mode to back-up mode (emergency power supply). If the transfer time is less than 20ms then the supply of power is not interrupted.
- Certifications: as the inverter is connected to the public electricity distribution network, it is mandatory that it complies with the standards in force in your geographical area.
- Type of inverter: the inverter can be with transformer or without transformer (TL for transformless). Inverters without transformers generally have higher conversion yields than inverters with transformers. Make sure that the panels you have chosen are compatible with the inverter.