Clearing procedures for day-ahead Italian electricity market: are complex bids really required?

Many technical debates discussed in the last years the market structure that can be considered as optimal for electricity in a deregulated environment. Simplicity and market transparency do not always comply with the intrinsic complexity of the electrical system, due to technical constraints and security requirements. The mechanism for bid selection in the day-ahead market is one of the most discussed topics, because it strongly influences both the economical revenues of operators and the physical feasibility of the dispatching schedules set by the market. Usual production bids, only detailing hourly prices and quantities (“simple bids”), do not transfer to the clearing mechanism important technical-economical integral constraints, like the minimum daily revenue required by the operator or the power ramp limitation of generating units; in this case, adjustment sessions follow the primary energy market, to correct undesired or unfeasible outcomes. In some markets, such additional constraints are already expressed in the so-called “complex bids”, thus avoiding or minimizing the need for adjustment sessions. Nevertheless, the clearing mechanism of the day-ahead market results strongly complicated and the system transparency decreases; the effectiveness of this solution must be then carefully assessed. In this paper, we present an analysis of the possible quantitative impact of complex bids in the Italian electricity day-ahead market, in order to evaluate possible benefits and drawbacks