## Refining PSO Applied to Electric Energy Cost Reduction in Water Pumping - page 04

The study considered a minimum water level in the reservoirs of 1.5 m, and the pumps curves were defined with one point, i.e., using a hydraulic head of 85 m and a flow rate of 895 l/s. The value of the coefficient C of the Hazen-Williams equation that was adopted was 100 for all of the pipes, which is in accordance with the study by Carrijo (2004). Furthermore, for the operational cost studies, an 80% efficiency was used for the motor-pump sets. The study by Carrijo (2004) considered the energy cost as Brazilian Real (R$) 0.17076/kWh during the peak hour and R$0.0816/kWh at all other times. In turn, the demand at the peak hour is considered to be 26.38 R$/kW and at all other times is considered to be R$8.66/kW. With all of the simulations performed for the previously detailed network, the following result is obtained for the cost of the operational routine:

It can be observed that the routine found with PSO-R works with higher rotations that reduce the occurrence of excessive vibration problems, and therefore, cavitation problems can be avoided. Next, comparative graphs are presented with the reservoir level and pressure at the control nodes. By observing the reservoir level fluctuation graphs, the significant level variation of reservoir 29 is observed once again, which reflects the pressure variation at node 30. Moreover, the level of fluctuation caused by the routine found with PSO-R leads to emptying in moments of greatest water consumption and higher energy cost.

Figure 2: Level fluctuation of reservoir 14: comparison of techniques

Figure 3: Level fluctuation of reservoir 19: comparison of techniques

Figure 4: Level fluctuation of reservoir 24: comparison of techniques

Figure 5: Level fluctuation of reservoir 29: comparison of techniques