Connection diagram for Micro-Inverter We spent this weekend installing a 200W solar panel to power some of the AC loads in my home. Instead of the traditional method of using a panel to charge batteries, I installed something called as a Grid-Tie Micro-Inverter. Like most things in life, this has advantages as well as disadvantages. Read on to find out more...
What is a Micro-Inverter and what is it used for?
There are generally 2 ways of harvesting energy of the sun. In the more common method adapted for residential applications, you connect Solar Panels to a Battery Bank via a Solar Controller, and use the energy stored in the Battery Bank using an Inverter to run your AC loads like lights, fans, etc. Dis-advantage of this technique is the Batteries, which are costly and need replacing in 4-5 years. However, when you have access to fairly reliable grid electricity but would still like to use Solar Energy without incurring cost of batteries, Micro-Inverters is the way to go. A Micro-Inverter connects directly to your Solar Panel and generates AC power that's phase matched with your grid power. Thus, your appliances use what ever power is generated from your panels, and the balance power is drawn from the grid, thus eliminating the need of batteries, and reducing your electricity bill. Since one Micro-Inverter is connected to one panel, it can utilize something called as MPPT (Maximum Power Point Tracking) to extract maximum power out of a solar panel, which is not possible in systems where multiple Solar panels are connected in series/parallel to a single Inverter. Another advantage of a Micro-Inverter is that it can be connected to additional Micro-Inverters in a daisy chain to add capacitiy to your system, letting you increase capacity of your system gradually. Since each Micro-Inverter directly generates 230V AC from the panel its connected to, you can even connect mis-matched panels of different make, capacity, and age, which is not possible in traditional systems. The term "Grid Tie" implies that it's directly connected to the Grid supply, and supplies excess power back to the grid.
Does a Micro-Inverter generate power if the main power goes down?
A Micro-Inverter will stop generating power if the main power is shut off. This protects an electrician working on the line after he's shut off the main supply.
What if you generate more power than you use?
Here's the unfortunate part in a state like Maharashtra. The state has not introduced legislation to support Net Meters, where the electricity company can give you a rebate for whatever excess electricity is generated. Today, if you generate more than you use, the normal meter will report that as energy used and you will end up paying for the excess energy you produce! Therefore, you need to be careful in sizing the system to be just under what you normally use.
Will a Micro-Inverter supply power on a branch circuit that's being supplied power from a Diesel Generator OR a regular AC Inverter?
It would be great if you could supplement you Inverter/Diesel Generator's power in case of an outage to save Diesel/Battery. However in most cases, the Micro-Inverter is not able to synchronize the wave-forms generated by these power backup systems and shuts down till main power comes on. This means that your Micro-Inverter won't generate any power when your home is running on backup power. So one usually ends up connecting a Micro-Inverter on the input side of these systems rather than output. Having said this, I have personally not tried it out, and would like to confirm for myself that that is indeed the case.
Are Micro-Inverters cheap?
Sadly no. These devices are fairly sophisticated. Cost per watt for these will be almost the same as what you pay for the panel. But their inherent advantages make them worthwhile in the long run.
Photo our our Installation:
What is a Micro-Inverter and what is it used for?
There are generally 2 ways of harvesting energy of the sun. In the more common method adapted for residential applications, you connect Solar Panels to a Battery Bank via a Solar Controller, and use the energy stored in the Battery Bank using an Inverter to run your AC loads like lights, fans, etc. Dis-advantage of this technique is the Batteries, which are costly and need replacing in 4-5 years. However, when you have access to fairly reliable grid electricity but would still like to use Solar Energy without incurring cost of batteries, Micro-Inverters is the way to go. A Micro-Inverter connects directly to your Solar Panel and generates AC power that's phase matched with your grid power. Thus, your appliances use what ever power is generated from your panels, and the balance power is drawn from the grid, thus eliminating the need of batteries, and reducing your electricity bill. Since one Micro-Inverter is connected to one panel, it can utilize something called as MPPT (Maximum Power Point Tracking) to extract maximum power out of a solar panel, which is not possible in systems where multiple Solar panels are connected in series/parallel to a single Inverter. Another advantage of a Micro-Inverter is that it can be connected to additional Micro-Inverters in a daisy chain to add capacitiy to your system, letting you increase capacity of your system gradually. Since each Micro-Inverter directly generates 230V AC from the panel its connected to, you can even connect mis-matched panels of different make, capacity, and age, which is not possible in traditional systems. The term "Grid Tie" implies that it's directly connected to the Grid supply, and supplies excess power back to the grid.
Does a Micro-Inverter generate power if the main power goes down?
A Micro-Inverter will stop generating power if the main power is shut off. This protects an electrician working on the line after he's shut off the main supply.
What if you generate more power than you use?
Here's the unfortunate part in a state like Maharashtra. The state has not introduced legislation to support Net Meters, where the electricity company can give you a rebate for whatever excess electricity is generated. Today, if you generate more than you use, the normal meter will report that as energy used and you will end up paying for the excess energy you produce! Therefore, you need to be careful in sizing the system to be just under what you normally use.
Will a Micro-Inverter supply power on a branch circuit that's being supplied power from a Diesel Generator OR a regular AC Inverter?
It would be great if you could supplement you Inverter/Diesel Generator's power in case of an outage to save Diesel/Battery. However in most cases, the Micro-Inverter is not able to synchronize the wave-forms generated by these power backup systems and shuts down till main power comes on. This means that your Micro-Inverter won't generate any power when your home is running on backup power. So one usually ends up connecting a Micro-Inverter on the input side of these systems rather than output. Having said this, I have personally not tried it out, and would like to confirm for myself that that is indeed the case.
Are Micro-Inverters cheap?
Sadly no. These devices are fairly sophisticated. Cost per watt for these will be almost the same as what you pay for the panel. But their inherent advantages make them worthwhile in the long run.
Photo our our Installation:
Photo of our Installation
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