For some, installing a PV system and not being able back up loads is unacceptable. One option to avoid the cost and inefficiency of batteries in a GT system is to install an engine generator. But how an engine generator is installed and works in conjunction with your PV system is a very important consideration.
For batteryless inverters, it is important to include a transfer switch so that the inverter never “sees” the AC output from the generator, and so the generator does not feed into the grid. During a power outage, the generator could automatically turn on to serve the loads. If the generator and inverter weren’t electrically separated, the inverter may try to connect to the generator, as if the generator was the grid. This could damage the generator and could result in an explosive and flame-filled ending.
The transfer switch allows the loads to be connected to either source—grid or generator—but never both at the same time. To avoid allowing the inverter to connect to the generator, the inverter should always be connected to the utility side of the transfer switch. This will make sure that the inverter and the grid are properly protected from the generator output.
With some battery-based inverters, it is possible to connect the generator directly to the inverter, just like a stand-alone system, and isolate it from the grid without an additional transfer switch. The inverter is limited by the amount of current it can pass through and fully utilize. This means you need to analyze the specifications for the inverter and match them to a generator. Other inverters require incorporating a manual transfer switch—you select the power source (grid or generator), then make some changes to the inverter’s programming to verify proper operation. Others can handle all those functions automatically.