Integrating Battery Storage With an Existing Commercial Generator
Adding battery energy storage to an existing commercial site rarely means starting from scratch. Many facilities already have backup generators in place. Not to mention, those generators may have been sized years before battery storage was ever part of the energy strategy.
For installers, that creates an important design question: How will the existing generator work with the new battery energy storage system? The answer can affect more than backup power. Generator size, connection points, battery charging, existing solar and the site’s overall control strategy all influence the best approach.
Start with the Existing Generator
One of the first considerations is whether the site’s generator can be connected directly to the battery system. With the Fortress Power eSpire Nano, a generator can be integrated through the inverter’s Smart Port, allowing it to support backed-up loads and charge the battery during an outage.
For many installations, that provides a straightforward path to generator integration. But existing commercial generators aren’t always sized around the limits of a new energy storage system. A facility may already have a larger generator capable of supplying significantly more power than the Nano’s Smart Port can accept. In that situation, simply connecting the generator to the inverter may leave some of that existing capacity unused.
When an External ATS Makes Sense
For sites with larger existing generators, the design can be expanded using an external automatic transfer switch (ATS).
Rather than routing the generator directly through the Smart Port, the generator can be integrated upstream of the eSpire Nano inverter. With Nano Pro and the Keystone EMS Controller, this configuration can provide up to twice the generator input available through the Smart Port alone while allowing the generator to support backed-up loads and battery charging.
There is another advantage: the Smart Port remains available. That gives installers more flexibility to use it for another site asset, such as AC-coupled PV or a controllable load, instead of requiring the generator to occupy that connection.
Bringing Solar, Storage and Generation Together
Generator integration becomes even more important when the site also has solar. A commercial facility may need the battery to provide backup, the generator to support longer outages and PV to continue contributing energy when it is available. Managing each asset independently can make the system more difficult to design, monitor and operate.
This is where Keystone EMS becomes an important part of the eSpire Nano Pro architecture. The controller can communicate with third-party distributed energy resources. It brings their operation into a broader site-level strategy. In a Nano Pro configuration, that may include the battery, generator, PV, loads and other supported assets.
Instead of viewing the generator as a separate backup asset, installers can design it as part of the site’s overall energy system.
One System, One View of Site Operations
Bringing multiple energy assets together is only part of the equation. Installers also need a way to understand how those assets are operating as a system. With Nano Pro & Keystone EMS, generator, PV, battery and site load data can be brought into a unified monitoring platform. This gives installers and system owners greater visibility into how energy is moving across the site rather than requiring them to monitor each asset separately.
That visibility becomes especially valuable during backup operation. The system can coordinate available resources based on site conditions. This helps determine when stored energy is used, when the generator is needed and how available PV contributes to the site’s loads. For commercial sites with multiple energy resources, the result is a more coordinated approach to backup power. Additionally, a clearer picture of how the entire system is performing.
More Flexibility for Commercial Retrofits
Existing commercial sites don’t always fit neatly into a standard system design. The generator may be larger than expected. Solar may already be installed. The customer may want battery charging during an outage. Or the site may need to preserve the Smart Port for another asset.
The eSpire Nano provides a straightforward path for basic generator integration, while Nano Pro with Keystone EMS gives installers additional options when the site’s existing equipment or energy strategy requires more advanced coordination. For installers working on commercial retrofits, that flexibility can make it easier to work with the assets already on site rather than designing the storage system around unnecessary limitations.
Working on a commercial site with existing generation? Talk to Fortress Power about the site’s existing equipment and energy goals to determine the right eSpire Nano configuration.