Energy Cost Optimization in a Water Supply System Case Study

The majority of the life cycle costs (LCC) of a pump are related to the energy spent in pumping, with the rest being related to the purchase and maintenance of the equipment. Any optimizations in the energy efficiency of the pumps result in a considerable reduction of the total operational cost. The Fátima water supply system in Portugal was analyzed in order to minimize its operational energy costs. Different pump characteristic curves were analyzed and modeled in order to achieve the most efficient operation point. To determine the best daily pumping operational scheduling pattern, genetic algorithm (GA) optimization embedded in the modeling software was considered in contrast with a manual override (MO) approach. The main goal was to determine which pumps and what daily scheduling allowed the best economical solution. At the end of the analysis it was possible to reduce the original daily energy costs by 43.7%. This was achieved by introducing more appropriate pumps and by intelligent programming of their operation. Given the heuristic nature of GAs, different approaches were employed and the most common errors were pinpointed, whereby this investigation can be used as a reference for similar future developments. 1. Introduction Investigating efforts in new technological innovations are aimed to improving the energy efficiency of the several production sectors, which also applies to water supply companies [1, 2]. Energy consumption due to the pumping systems represents the biggest parcel of the energy expenses in the water sector—sometimes up to 90% [3]—and there are several practical solutions which can enable a reduction in these costs. Pump and motor upgrades to more efficient solutions, either being technologically more advanced or because they are more properly adjusted to the system, often allow significant energetic savings [4]. Also, changing the pumping operational procedures is very effective since it does not need any additional investment and because the economy with the reduction of the energy cost occurs immediately. The consumption of energy in most of the water systems all over the world could be reduced by at least 25% [5], only by improving the performance in terms of energy efficiency. Operators of the water supply networks have a complex task in taking into account the distinct goals involved in this process. Determining operational rules to improve the quality of the service and that are also energetically economical, among an extensive set of possibilities, requires the utilization of models which take into consideration these