VFDs can reduce energy consumption and water loss in variable pumping systems.
09/07/2015
As the cost of energy and water and wastewater services continues to rise, operators are looking for ways to reduce the costs of these basic, yet crucial, utilities. Proposed energy efficiency standards from the U.S. Department of Energy (DOE) and other federal measures could help. In the water sector, the DOE has a mandate to develop and enforce national minimum energy efficiency standards for any product if significant savings can be realized in a cost-justified and technically feasible manner. During the past year, the DOE and stakeholders have been negotiating a regulation for pump efficiency. That rule, now in the Notice of Proposed Rulemaking (NOPR) phase, would apply only to clean water pumps of these types:
- End suction close-coupled
- End suction frame-mounted/own bearings
- In-line
- Radially split, multi-stage, vertical, in-line, diffuser casing
- Vertical turbine submersible
Figure 1. Water losses at different operational pressures (Courtesy of Danfoss)
While VFDs can help reduce energy consumption, which could lead to lower operating costs, some additional savings may not be initially realized:
- Protection of pumps and assets
- Reduction of maintenance costs
- Lower risk of bacteria/contamination of tap water
- Lower risk of road breaks
- Reduction in pipe repair cost
- Extended service life of network
- Postponed investment in system upgrades
- Improved control performance
- Increased redundancy
- Reduced load on supervisory control and data acquisition (SCADA) system because of dedicated VFD software features