PacifiCorp 2007 Integrated Resource Plan (May 30, 2007)

PacifiCorp – 2007 IRPChapter 4 – Resource Needs AssessmentObligationThe obligation is the total electricity demand that PacifiCorp must serve consisting of forecastedretail load and firm contracted sales of energy and capacity. The following are descriptions ofeach of these components:● Load – The largest component of the obligation is the retail loads of the load forecast. Describedin the beginning of this chapter the load forecast is an hourly description of electricloads in the PacifiCorp system for the 20-year IRP study period (2007-2026). The capacitybalance counts the load (MW) at the hour of system coincident peak load. The energy balancecounts the load as an average of monthly time-of-day energy (MWa).● Sales – This component includes all contracts for the sale of firm capacity and energy. Thecapacity balance counts these contracts by the maximum obligation at time of system peakand the energy balance counts them by optimum model dispatch. All sales contracts are firmand thus planning reserves are held for them for the capacity balance. Note that for the 2007IRP there was a reporting change for the delivery portion of exchange contracts. Exchangecontract deliveries are no longer reported in the Purchase and Renewable components as wasdone for the 2004 IRP and 2004 IRP Update. These delivery amounts now appear in theSales component.ReservesThe reserves are the total megawatts of planning and non-owned reserves that must be held forthis load and resource balance. A description of the two types of reserves follows:● Planning reserves – This is the total reserves that must be held to provide the planning reservemargin. 28 It is the net firm obligation multiplied by the planning reserve margin as inthe following equation:Planning reserves = (Obligation – Purchase – DSM – Interruptible) x PRM● Non-owned reserves – There are a number of counterparties that operate in the PacifiCorpcontrol areas that purchase operating reserves. This amounts to an annual reserve obligationof about 7 megawatts and 71 megawatts on the west and east-sides, respectively.PositionThe position is the resource surplus (deficit) resulting from subtracting the existing resourcesfrom the obligation. While similar, the position calculation is slightly different for the capacityand energy views of the load and resource balance. Thus, the position calculation for each of theviews will be presented in their respective sections.Reserve MarginThe reserve margin is the ratio of existing resources to the obligation. A positive reserve marginindicates that existing resources exceeds obligation. Conversely, a negative reserve margin indi-28 PacifiCorp models operating reserve requirements, which are based on minimum WECC Operating Reserves thatcover Contingency Reserves and Regulating Reserves. PacifiCorp also includes incremental reserves for supportingwind, which is documented in Appendix J.78