Well, as you know, a model assumes particular conditions, which you might lay out, as, for example, that fossil fuels are being depleted and that burning them contributes to climate change - implying that their use should be minimized. Or you can assume natural gas supplies are increasing and are cheaper than renewables and should be used. Whatever, state your input assumptions/premises. Then you'll need to state the roles of the "players" - those involved in controlling the process of planning. Indicate how those players will be involved in various aspects, such as setting electric rates, R&D, inspections, etc. (public hearings? committee meetings? appointments by the governor, etc.). That should get you rolling... Good luck!