Optimization of Variable Speed Pump Scheduling for Minimization of Energy and Water Leakage Costs in Water Distribution Systems with Storages

Optimization of water distribution systems (WDSs) to minimize operating costs becomes an important concern for water utilities, especially due to the continually increasing energy price. Besides the energy cost, water utilities worldwide are also facing with the water loss problem. More water loss occurring in WDSs will require pumps to work much more to supply extra flows and pressures for compensating the water loss amount. As a result, clean water is wasted and at the same time more energy cost is expensed without any benefit for water utilities. For this reason, optimizing operations of pump stations for minimizing only the energy cost by taking advantage of electrical tariff structure is indeed inadequate since the water loss cost may be higher than the energy cost. To be capable of practical implementation and preserve clean water resources, operational optimization of WDSs should take both energy cost and water loss cost into account for deducing optimal pump scheduling. This paper investigated the potential application of variable speed pumps (VSPs) for decreasing both energy cost and water leakage cost for operations of WDSs with storage tanks. The comparisons of the uses of VSPs and fixed speed pumps (FSPs) for many scenarios are also carried out demonstrating that the application of VSPs outperforms the use of FSPs in decrease of the total cost of energy and water loss.