Optimal Operational Planning under Uncertain Demand and Flexible Electricity Tariffs

Abstract Submission: When operating an existing water distribution system (WDS), it is necessary to operate the network as cost-effectively as possible. In addition to uncertain demand (the biggest uncertainty factor in a WDS), the electricity tariff also changes due to market influences. Therefore, it is impossible (or prohibitively expensive) to meet all technical constraints on the network operation for a day-ahead planning. For example, the water utility may plan to produce as little water as possible to reduce operating costs, but at the same time wants to reduce the total water age and pressure. However, due to the demand uncertainty, there is a certain risk that the demand cannot be met during operation. In such a situation, a conservative strategy is usually pursued: the water company produces a large amount of water (i.e. much more than necessary) to meet the demand, even if the plant is operated at a high electricity tariff. To avoid excessive costs, the water company can try to find an optimal trade-off between the operation cost and the desired level of operational reliability in the planning phase, which represents the objective of this study. We propose to solve this problem by chance constrained multi-criteria optimization considering hydraulics, water quality and costs. As a result, the planned operational strategy will guarantee pressures and water age within the specified operational range, as well as demand satisfaction with a user-defined probability (i.e. reliability), while minimizing the expected operational costs.

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