We present the perfect forecast concept as both an effective forecast validation metric and an operational strategy to integrate increasing amounts of variable solar power generation on power grids. The costs incurred in transforming imperfect into perfect predictions define the new metric: these include the costs of backup storage and output curtailment necessary to make-up for any over/under predictions. We illustrate the concept with the most recent version of the SUNY forecast model for hour-ahead and day-ahead forecast examples with single power plants as well as distributed PV fleets. We show that delivering perfect predictions – i.e., fully eliminating grid-operators uncertainty — is achievable at small operational cost. Most importantly, we show that a perfect forecast strategy with optimized least-cost storage and overbuild/curtailment is an effective first step of a longterm strategy to cost-optimally transform variable PV generation into firm, effectively dispatchable generation capable of displacing conventional dispatchable and baseload generation.

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