Hello Paul.
I think the approach the SAM team makes is the right one, in the sense of keeping it as simple as possible.
My first suggestion would be to simply incorporate an input field similar to what you have incorporated into the latest version of SAM in the "project term Debt".
I am referring to the entry field "Moratorium" in order to better model bank credit. Just as this input field delays the payment of credit, another input field could be incorporated that delays the necessary years (typically 2 or 3) for starting production, which has a significant impact on the IRR and NPV.
Currently, I have to export the results to excel, enter some columns depending on the years I want to delay revenue, and recalculate the IRR and the NPV.
The second suggestion would be to prorate the investment during the construction years, typically with 2 or 3 years would be sufficient for almost all kinds of projects. This can be further refined, because it admits many improvements, but I do not know if the effort will be worth it, since most renewable energy projects have a construction period of less than a year, so most users of Sam may think maybe it is not worth it.
The projects I work on are hydroelectric (more than a year of construction period) and wind farms (more than a year, because wind farms that we concretely develop are those of complex orography).
As feed in tariffs have been shrinking in Europe, it is increasingly important to study the financing of projects, especially credit coverage. Do you intend to incorporate swaps, collateral or subordinated debt into the financial model? (In Spain we have moved from a feed in tariff system to electrical auctions, so that I am working more as a financial than an engineer.)
