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Need for Solar Power Inverters
The power grid and almost every equipment that uses electricity uses alternating current (AC) while solar modules - either individually or when connected together - generate Direct Current (DC). Therefore it is extremely important to switch the DC power being generated from solar power with an inverter into useable AC power. Thus a solar inverter actually “inverts” DC to AC to operate all types of common electrical loads from lights and fans to air-conditioners and heavy machinery without interruption.
Components of Solar Inverter
There are two major components of a solar power inverter:
On the AC side, these solar inverters supply electricity in sinusoidal form. On the DC side, the power output of a module varies as a function of the voltage in a way that power generation can be optimized by varying the solar system Voltage to find the 'Maximum Power Point'. Sunipod solar inverters therefore incorporate optimized 'Maximum Power Point Tracking' (MPPT). It ensures optimal energy transfer from the solar PV system using MPPT technique which maximizes the amount of current going into the load from the solar array. An under optimized solar MPPT algorithm can seriously affect the amount of solar electricity generated from your solar power solution.
Types of Solar Inverter
Solar power inverters can be categorized based on size and type.
Solar inverters can be large array inverters also called as central inverters or they can be smaller string inverters. However, the problem of partial shading or shadowing — technically termed as potential induced degradation (PID) of the solar panel — is prominent with the use of large solar array inverters. Solar string inverters are installed at each string level. It converts the solar generated DC power to AC power using a separate solar inverter for each string. This inverter also uses the solar MPPT (maximum power point tracker) technique for better output. The advantages of such a solar inverter are that it has more reliability and leads to better solar power generation while also reducing the PID effect.
The sizing of inverter depends on site characteristics, the size of the solar power solution and the electrical load connected to that system.
2 common types of solar energy inverters are On-Grid Solar Inverters also known as Grid-Tie Solar Inverters and Off-Grid Solar Inverters. Both serve a different function and are used for a different type of solar energy system, although each inverter still converts DC into AC.
On-Grid/Grid-Tie/Grid Parallel Solar Inverters
On grid parallel solar inverters are for use in most situation where your solar array is “tied” directly and in parallel to your local power grid. These systems, known as grid tie solar systems or grid parallel solar systems, are more common and are much cheaper because of the lack of need for a battery.
In such systems, DC from the solar panels is sent to the grid tie inverter which converts into AC. In this type of system, it is necessary to have your solar unit wired to your incoming line from the grid. Thus ensuring that your load uses solar energy you produce while any excess power required is sourced from the power company.
This type of system is best suited for common commercial and industrial applications but offers no protection in case of power outages because of the lack of a backup battery. But if like most large operations you consume power during the day time, then there is no need to save this electricity when you could be using it directly as and when produced, thus saving you costs on power storage equipment.
All on grid systems are required to have a solar energy inverter with anti-islanding protection which forces them to shut down in case of power outages. Without anti-islanding protection, your solar system would continue to generate electricity and send small amounts back into the electric grid during power outages. This energy would stay in the local power grid and is referred to as an island. These islands can be extremely dangerous for utility workers who are trying to repair the gird during a power outage.
Off-Grid Solar Inverters
Off-Grid Solar Inverters are used in systems where the solar panels generate direct current energy which is then stored in rechargeable batteries. When energy is required, the DC is sent from the battery to the off grid solar power inverter and then converted into AC which can then be used to power your electricity needs.
Even if we want to simply charge the solar generated DC power from the solar array to a battery bank we need to “invert” from DC to AC and control the charging using the solar charge controlling capabilities of your solar inverter. This solar charge controlling capability ensures that the solar battery bank is charged using just the optimum amount of current and voltage to enhance battery life and maintain the right output voltage for the solar battery bank input.
Sizing the solar array and the batteries required is complex. Detailed analysis of your requirements will be needed to provide for your minimal critical needs. You'll also need to rewire you main electrical panel to isolate the "critical loads" so that only they are provided power in an outage. This means that some of the equipment is provided power while other non-essential loads are not.
With systems using off-grid solar inverters you will be free to consume electricity whenever you wish, provided your batteries are charged or your solar array is currently producing electricity.