3. Results
This study raises several remarks (see Fig. 2):
• We tend to pump during the night, when electricity is cheaper.
• Looking at Figs. 1 and 2, the solution results in pump operating points that are close to the highest efficiency points (around 43 พ?3//?).
• For Water Tower 2, we fill it separately during the first day because the pressure drops are significant at section Junction 12 - Water Tower 2 due to a small pipe diameter. The aim is to obtain a discharge pressure close to the hydrostatic pressure and thus to pump most efficiently during off-peak hours. With this strategy, only one pump is less efficient (Pump 2 between 0:00 am and 2:00 am). On the second day, pumping occurs with a constant and smooth flow into water tower 2 in order to avoid significant pressure losses.
• If we install variable speed drives, the total electricity charges will not be significantly reduced.