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What Type of Inverter is Best?

Q:

What Type of Inverter is Best?

A:

Very recently the PV industry has developed a new configuration of inverter for PV systems. (An inverter takes the direct-current electricity from the solar panels and "inverts" it into alternating-current.)

Conventional PV inverters are called "String" inverters because they usually take the power from a group of PV panels that are "strung" together, or several groups of PV panels strung together. These strings of panels can generate higher voltages the inverters require.

The new entry is the PV panel inverter - basically an inverter is used for each PV panel. This approach has some specific advantages, and some drawbacks.

The principle advantage is that it can make the whole PV system more efficient. In large PV systems with string inverters, there can be many panels in a string. If one of those collectors is shaded, damaged or underperforming, the whole string suffers and the energy delivered will be significantly reduced or completely stopped. In a large group of PV panels that use individual panel PV inverters - only the shaded, damaged or underperforming panel is going to be affected - other PV panels would continue to operate at full capacity. Another advantage is that the wiring is simplified as the DC/AC interface is at the PV panel - all wiring after the PV panel is AC.

The biggest issue with the individual PV inverter is the servicing of the inverter. Instead of being placed inside an accessible room, they are located on the roof, behind the PV panel. In a large PV array on a steep roof, several stories tall, this will be a problem. These are new products, without a long track record of performance. They are also typically more expensive and require somewhat more labour to install. Inspectors, already not very familiar with solar string inverters, may be a problem because they will not go onto the roof to inspect the individual inverters.