TPO/Developer Model

Hi Omar,

If the hotel owner plans to build, own, and operate the PV-plus-storage system and use the power to reduce power required from the diesel generator and grid, then I think the Commercial financial model would be suitable. A positive net present value (NPV) would mean that the savings from fuel and grid purchases offset the cost of installing and operating the system.

SAM does not model diesel generators and assumes the grid is always available to meet the load when needed or unreliable grid. You could use "Electricity from grid" to represent power from the grid and generator. On the Electricity Rates page:

1. Choose the "Buy all / sell all" metering option.
2. For the energy charge rate table, set Number of entries to 1, set the sell rate to zero and the buy rate the aggregate price of electricity in $/kWh to represent purchases of both diesel fuel for the  generator and electricity from the unreliable grid.
3. Set the Period in both the Weekday and Weekend tables to 1. (Use your mouse to select the entire table and type "1" on your keyboard.)



For that approach to work, you would need to size the PV array / inverter and battery bank to minimize exports to the grid.

If the hotel owner plans to enter into a partnership with a developer, where the developer builds, owns, and operates the system and the hotel owner (host) purchases power from the developer at a fixed price negotiated through a power purchase agreement (PPA), then the Third Party - Host / Developer model is the one to use. It will help you determine a PPA price that results in a positive NPV to both the both the host and developer. You could use the same approach I describe above to model the system.

The Single Owner financial model would best represent a scenario where the developer builds, owns, and operates the system and sells all of the power it generates at a fixed power price (with optional time-of-delivery multipliers).

For the distributed generation financial models, SAM assumes that the system reduces grid purchases to meet a building or facility's electric load. If you set the load to zero, or use the "no load" option for a PV-plus-storage system, all of the power generated by the system is excess generation and is either credited to the project for net metering, or sold by the project for "buy all / sell all." For these projects, if there is not a load, SAM will not discharge the battery, so it never needs to be charged by the PV system. To model a PV-plus-storage system that discharges the battery to the grid, you should choose one of the PPA financial models.

Best regards,
Paul.

Hi Omar,

We are working on enhancements to SAM to make it suitable for modeling microgrid applications, so stay tuned.

If you are not aware, the commercial software HOMER is designed specifically to model off-grid and grid-connected hybrid systems. It was originally developed at NREL, and is now developed and distributed by HOMER Energy LLC.

Best regards,
Paul.

Hi Omar,

We have plans to add the capability to model an unreliable grid and grid outages, which will at least go part way toward SAM's being able to model minigrids and microgrids. We hope to secure funding to implement those plans for the Fall 2021 version of SAM.

Best regards,
Paul.