TPO/Developer Model

I have PV system plus storage proposal but not sure best way to implement in SAM.

I have a hotel owner who relies on his own diesel generator and a very unreliable grid powered by connected diesel engines at some distance (few kms away.)  The hotel owner's electricity bills is very high and he is looking to explore adding solar PV plus storage. My plan is to use SAM's TPO/Developer model to make initial feasibility analysis since the model provides both Host and Developer financial info. The analysis is based on the Host/Developer  PPA agreement.

I know SAM does not model Off Grid systems but what is the best way to get as close as possible to a proposed PV plus storage with minimal grid interaction?
 
Conceptual Questions:
Does TPO/Dev model works when "no load data" is selected on the Electric Load? I noticed that battery will not charge from PV when "no load data" is selected. Is it OK to assume that Developer's system (PV +battery) can ignores Host's hotel load "no Load data" but simply sell his system's generated electricity. Is it also OK to assume that PV can charge battery during day time  and sell battery power to the Host during night time.  All with minimal interaction with grid and with "no Load Data" option.

Thanks for the help.

Omar

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.

Paul,
Thank you for the detailed input. It  gives me options and cleared some basic concepts. My apologies if some of my questions/inquires are basic ...just getting started with SAM.


Note: I am here in the US but working with people in Africa where more 60 million inhabitants and businesses have no access to electricity. Existing grid extension or new grid infrastructure is very extensive. The only feasible option currently is diesel generator. Solar PV plus storage has a lot of promise with falling prices but technology penetration is very slow mainly due to lack of investment and skilled labor.  SAM with Off Grid capability would have been really a welcome tool. Any future plans for SAM to add Off grid capabilities?  Even a reasonable work around would have been also be welcome news.

 
Thanks again for your support

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.

Paul,

Just a follow up question regarding the upcoming SAM application to model Microgrid systems, see your note above. Any info on expected timing in terms whether SAM's Mirogrid capability is expected some time this year or perhaps next year. 

Thanks
Omar 

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.