Reducing pumping costs for water utilities
It wasn’t long ago that water and wastewater utility providers viewed energy as a cost of doing business. It was simply embedded within the price of the product or service, and then passed along to the customer because no one questioned it. However, utilities today are facing revenue constraints combined with increasing costs, which require managers to evaluate methods for either increasing revenues or reducing expenses. As you can imagine, increasing rates or reducing jobs are not very popular alternatives. One method that can help solve the challenges of this economic reality is to look at reducing other kinds of costs. Energy consumption often stands at the top of the list since it is one of a water or wastewater facility’s highest expenses.
Water and wastewater management is an energy-intensive operation. Currently, there are more than 75,000 water and wastewater systems within the U.S. alone. These facilities are estimated to consume well over 150 billion kWh annually, which is approximately 12% of the total electricity consumed in the nonresidential, commercial, and industrial sectors. And if current energy projections continue, these facilities will account for an increase of 29% by 2040, according to the U.S. Energy Information Administration. This increase in energy consumption will only further add to the economic strain that modern utility providers face.
Reduced costs through operational efficiency
The majority of energy consumption is tied to water processing and distribution in the form of motor-driven systems that operate pumps. In fact, pumps account for 80% of electricity used by water systems. A utility can realize substantial energy reduction by operating its water-pumping systems with greater efficiency even without upgrading any of the major components. These efficiencies are gained not only from a design and asset lifecycle management perspective, but by operating the right (most efficient available) component pumping systems at the right time, for the right duration, to meet operational requirements at the lowest cost.
Analyzing available assets
To ensure availability for a particular process, most water facilities use built-in pumping system redundancy to meet constant availability and capacity requirements. Each pump site within the system is designed to support a specific process; however, they typically function with unique operating and efficiency characteristics due to a low degree of standardization. Pumping system efficiency can vary greatly depending on the age, design, operation, and maintenance of a given asset throughout the system’s lifecycle. This aspect, coupled with system availability and varying demand, serves as proof that managing multi-source pumping system operations for optimum performance at the lowest energy cost is a complex operational problem. Adding complexities caused by variability in electricity costs (peak rates can vary by more than 500% from normal and off-peak rates) compounds the challenge.
The following intelligence is required to optimize pumping operation:
- Pumping systems’ energy efficiency
- Optimum pumping system operating configuration
- Optimum pump systems’ operating strategies
- Potential cost savings
- Potential environmental impact
- Opportunities to shave peak load
- Opportunities to reduce demand charges
- Additional capacity requirements
- Excess capacity requirements
- Nonconformance identification and communication
- Out-of-service capacity needing expedited resolution
- Identification of potential maintenance and capital improvement opportunities, and
- Validation of efficiency countermeasures.
Without greater asset visibility, the chances of operating a pumping system for the lowest cost would be challenging at best. Access to this level of intelligence brings significant potential for energy cost reductions—as efficiency increases, costs fall proportionally. As a result, some estimates would put savings equal to, if not exceeding, system efficiency gains.
Framework for smart pumping solutions
Optimal pumping system performance at the least energy cost can be predicated through the convergence of energy, asset management, and operations. This approach must factor in process definition (what specific pumping systems comprise what unique processes), system efficiency, system availability, system capacity, time-of-use energy and demand rates, the demand required, and operating strategy (base load vs. variable load and peak shaving). Of equal importance is the ability to assess these systems based on the most current operating and performance data available, as well as pumping system energy performance and non-optimal operating anomalies, while also notifying the appropriate stakeholder at the right time, at the right place, and with the right information to address potential opportunities and assess operating changes once they are made.
Des Moines Water Works’ (DMWW) approach is to systematically achieve the best outcome, quantified as the lowest possible cost, through optimizing pumping system demand, capacity, and costs. Ultimately, DMWW’s framework provides the necessary level of intelligence needed to answer the following questions:
- Which pumping systems should be operating to meet the operational demand?
- What is the optimal pumping strategy and system-operating configuration?
- How long should each pumping system operate per day?
- When should each pumping system operate per day?
- Are the pumping systems operating at the least possible cost?
- What is the cost per day to operate the pumping systems?
- Is additional capacity required to meet demand?
- What is the environmental impact of the pumping operation and the management controls required to keep the program sustainable?
Like DMWW, there are several considerations when adopting a pumping system(s) optimization approach, including:
- The pumping systems’ configurations, design basis, and availability need to be defined and systematically kept current.
- The pumping system(s) efficiency needs to be systematically determined and kept current.
- Applicable electricity provider time-of-use rate schedules need to be mapped to the unique pumping systems.
- System demand (capacity requirements) needs to be allocated to the pumping systems and ad-hoc adjustments enabled.
- The intelligence and controls need to organizationally align accountability and responsibility.
DMWW’s multi-source pumping system optimization will enable our utility to know exactly where our pumping system energy is going and, more importantly, where it should be going. Pumping system optimization intelligence will meet DMWW customers’ water demands while saving energy expense-all of which goes straight to the bottom line.
William Stowe is CEO and general manager, Des Moines Water Works.
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- While energy saving programs often begin by replacing existing equipment with higher-efficiency choices, improved operational strategies can reduce energy consumption without costly capital improvements.
- Determining optimal equipment use depends on having detailed information about the equipment involved and the ability to calculate the lowest-cost outcome at any given time.