Graphic determination of available energy-saving potential in a reservoir pumping application with variable-speed operation

Centrifugal pumps represent a notable share of electricity consumption in motor-driven systems. Many studies have verified the energy-saving potential in these systems with device improvements and by modification of the applied flow control method or characteristics of the surrounding process. The best approach for reaching a more energy-efficient reservoir pumping system has to be determined for each system separately, making the analysis too laborious for a typical system operator. This paper proposes the application of graphic analysis tool for determination of the available energy saving potential in a reservoir pumping application. To realize this object, this paper studies how the available energy-saving potential in a reservoir pumping system is affected by two different variable-speed control schemes and by surrounding process variables, namely the static head variation and friction factor. Based on conducted simulations, generic graphs for determination of the available energy saving potential in the reservoir pumping application are formed, and their applicability is tested with two real-life cases. The produced graphs for available energy-saving potential seem to provide feasible results when compared to the case studies, justifying their use for instance in energy audits. Hence, this paper provides an effective tool for pumping station operators to assess economic feasibility of a variable-speed operation in their systems. However, further testing is required to see whether the resulted graphs are representing reality in all situations that can be described with static head and its variation.