An Experimental Study on Energy Saving and Carbon Emission Reduction in a Variable Speed Multistage Pump

Centrifugal pumps are commonly utilized to transfer liquids from one point to another in water supplies, irrigation systems, industrial processes, power generation, and HVAC applications. The issue of energy saving in pump operations is still a hot topic for researchers to both reduce energy costs and help preserve energy sources, because centrifugal pumps hold special importance for a sustainable energy future. The majority of these hydraulic machines are operated at a constant speed through throttle valves; however, variable speed technology offers a wide range of operation speeds using variable speed drives (VSDs). This study aims to lessen and mitigate the electricity costs of the operation of pumps by saving energy through variable speed control. The control method of variable speed for centrifugal pumps is mainly separated into two categories: constant pressure pump control (CPPC) and proportional pump control (PPC). In this paper, a horizontal multistage centrifugal pump operated with three different control methods, including throttling control at a fixed speed for full loads and part loads, variable speed control at a constant pump pressure, and variable speed control in proportional control mode, is investigated. All of the numerical values of flow rates, pump heads, electrical input power, and other variables are experimentally measured. The system curve of the used pump and pump characteristic curves are created based on the results of the experiments for applied control methods. Each control method applied on the test rig is assessed in terms of energy consumption to decide if the control technique is economically feasible. Payback periods are calculated through pump control methods within the scope of economic sustainability. This research demonstrates that the payback periods of the VSD are 7.4 and 12.6 months for proportional control modes and 45.18 months for constant pressure pump control. Applied variable speed methods achieve significant energy savings compared to throttling control for sustainable energy consumption that aligns with the Sustainable Development Goals (SDGs) of the United Nations (UN). This article demonstrates how flow regulation techniques in pumping systems contribute to sustainable energy consumption and reduce carbon footprint.