Comparison energy consumption for combined VSD pump with constant speed pump in raw water pumping
Keywords:
Energy management, Raw water pumping, Pump, Variable speed driveAbstract
The raw water pumping system functions to pump raw water from the source into the production system by using pumps connected in parallel. The control of the pumping rate is achieved by adjusting the pump speed to increase or decrease the pumping rate. However, installing variable speed drive on every pump requires a high investment cost. Installing variable speed drive on only some pumps is therefore a cost-saving approach. In this experiment, pumps with adjustable speeds are operated together with pumps of fixed speed, and the optimal operating point for the raw water pumping system is determined to maximize energy savings at pumping rates of 8, 8.8, 9.6, and 10.4 . This is done by adjusting the speed of the variable-speed pumps in combination with 1, 2, and 3 constant-speed pumps.
The results show that at pumping rates of 8 and 8.8 , operating 4 variable-speed pumps yields the highest overall efficiency of 55.1 % and 55.3 %, respectively. At pumping rates of 9.6 and 10.4 , operating 2 variable-speed pumps together with constant-speed pumps yields the highest overall efficiency of 56.4 % and 53.4 %, respectively. In summary, operating an appropriate number of pumps according to the pumping rate, with pump speeds above 85 %, results in an overall efficiency greater than 53 %. When operating variable-speed pumps together with constant-speed pumps, only 1-2 constant-speed pumps should be used so that the remaining variable-speed pumps maintain speeds not lower than 85 %, thereby preserving high overall efficiency more than 50 %.
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