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Why have a Generator?
You may wonder, "Why would a renewable energy storage system (like wind or solar) need a generator that burns fossil fuels to charge its batteries?"
A generator is a crucial component for off-grid energy storage systems and can even be necessary for some grid-tied applications. Local challenges like snow-covered arrays, short winter days, or extended grid outages can strain even the most resilient battery banks. Some off-grid system owners run their generators up to 300-500 hours annually!
The generator becomes a backup to the system's backup solution, so selecting the right generator is important. You will want to identify whether you are just seeking to assist the battery (when times are tough) or if it is also used to run large loads that would otherwise be too much of a strain on the battery.
Here are a few examples:
- Central air and heat
- Pool pumps
- Well and water pumps
- Luxury loads, like arc welders, exotic fish tanks, and hot tubs
Generator Options
There are many generator types, makes, and models. Not all are compatible with modern grid-tied energy storage systems (ESS), and the system's owner can experience support issues:
- ESS manufacturers may not provide guidance for third-party components like generators, as their scope can be limited to an estimation (based on an error code within their product or app), which can result in increased service calls for the company.
- Generator manufacturers may not be equipped to assist with calls regarding ESS integration, as it is not a primary goal for their product.
The three most common generators available on the market are:
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Inverter Generator Application: Recreational Power: Up to ~3000 watts Made for ESS integration as a temporary solution for short-term outages. |
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Portable / Recreational Application: Short-term power outages, job site power Power: Up to 10 kW Typically not compatible with ESS, as they create "dirty" power. This power is unsuitable for long-term use with most appliances and sensitive electronics. |
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Home Standby / Backup Application: Whole home backup, commonly used in energy storage systems Power: 8 – 40 kW Home backup generators create clean power and have features that allow easy integration with a modern ESS (can be automatically started and stopped by a hybrid inverter). |
Compatibility
There are as many generator makes and models as there are PV inverters. Generator compatibility is a common concern, but ESS manufacturers rarely provide a complete list of specific makes and models. However, searching based on the features compatible with ESS will help reduce the list to something more manageable.
Tigo's whole home 200A rated automatic transfer switch (ATS) is compatible with generators that have these characteristics:
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Common Issues and Maintenance
It is worth discussing generator auto-start requests since a failed start is a common reason for a service call. Here are the top reasons (in order, generally) for a failed generator start.
- No fuel
- Dead battery
- Poor preventative maintenance
- Low oil level
- Choke adjustment
- Dirty air filter
- Clogged fuel filter or valve
- Dirty carburetor
- Bad spark plug
To ensure proper usage and maintain operational status, always refer to the manual for instructions and set reminders for preventative maintenance.
Aside from maintenance, generators have specific settings and requirements that help prolong the product's life. In most situations, integrating with a quality ESS will automatically take care of these settings.
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CAUTION: Using a generator without the Tigo Automatic Transfer Switch (ATS)
1. You must never allow the PV inverter to operate while the generator is running.
Running a generator while a PV inverter is in operation is never permissible unless the ATS can isolate the PV inverter. The Tigo EI ATS accomplishes this criteria. However, if you are using a third-party generator without the Tigo ATS and Battery, then there are important application considerations to understand before operation.
2. Using the Tigo EI Inverter with an existing generator and third-party ATS
It is possible to use a Tigo EI Inverter with an existing generator and third-party ATS, but you must ensure the EI Inverter never operates while the generator is running. Excess solar could backfeed from the backup panel to the generator breaker and the generator regulator board, irreparably damaging the generator. This is not covered by their warranty.
The safest way to prevent generator damage during a grid outage is to install a small relay on the AC line that connects the inverter breaker that will open when the grid goes down. This will turn the inverter off while the generator begins to run since it detected a grid outage.
This diagram shows an existing ATS and generator. The homeowner wants to install the Tigo EI Inverter but not the battery. In this whole home backup generator application, the Tigo inverter breaker would attach to the main panel that the generator feeds. Notice the small relay on the AC line from the inverter breaker on the main panel.
This relay must open when there is a loss of grid, so its power supply must not be on the main panel. Otherwise, when the generator detects a loss of grid and starts up, the relay will now have power, and you run the risk of PV backfeed.