Hi Paul,
Thanks for your note-as usual very helpful and timely. Thanks so much!
A few clarifying items from my question and how I will be interpreting your response.
The facility I am looking at already has PV on it. I created a load profile for the facility from utility and solar 15 min data, which I am calling "native load" because, as you noted, it removes any excess generation back to the grid giving a picture of the facility's actual energy use. I am using this "native load" to model the existing PV (78kW) with an additional 280kW along with storage, or in another scenario, just storage in various financial arrangements. I want to model all the PV not just new arrays so that the battery controller knows what solar resources are available at each timestep.
My main question, which you seemed to have gotten to, is how to discount the cost for the existing PV on the financial side for the various setups. My concern was that because there is diminishing marginal value of the PV as the system output outpaces what the facility needs (in hopes of reaching zero energy), that I might need to be careful where and how I discount the existing PV costs.
For the scenario which only sees us adding a battery, I will do as you say and just set capital costs of a PV system that match what is already on site to zero. For scenarios where I add PV, I will discount capital costs (rate per installed watt) that represent what is already onsite.
Thanks again.
Best,
Henry