Smart Modeling for Water Distribution System Energy Optimization

Authors:

  • Bryan Lisk PE, John Collett - Hazen and Sawyer
  • Ray Shell - City of Macon GA

Distribution is a large part of overall energy costs, presenting a high benefit potential from energy optimization.

Hydraulic modeling can be used to to identify and evaluate multiple types of energy optimization opportunities, including scenarios for pumping efficiency, variable speed systems, optimizing pumping operations, and simulating energy usage to compare potential savings.

For hydraulic modeling to be a truly effective energy management tool, we have to have a means to develop a demand profile and understand how the specific billing elements unique to the facility impact the bottom line energy costs. Billing rate modeling takes the last step to calculate actual energy costs.

When energy is used and how much energy is used determines the overall cost.

Reducing energy usage and costs is rapidly becoming a major priority for water utilities. Numerous water and wastewater utilities are searching for economically feasible opportunities to reduce operating costs through optimizing collection and distribution systems. Many water utilities maintain a calibrated hydraulic model for planning purposes to ensure their distribution systems have the capacity to meet their customer’s demands while maintaining water quality. In addition to a planning tool, hydraulic modeling can also be a very effective tool to identify opportunities to maximize pumping and conveyance efficiency. It is common practice to optimize energy efficiency by using hydraulic models to identify the lowest energy usage scenarios. However, this strategy may not result in the lowest cost scenario since the model does not take into account the unique elements of the electric utility billing rate structure (i.e. demand ratcheting, time-of-use billing, and coincident peak billing). Electric billing rate modeling provides a means to accurately calculate the bottom line energy costs by incorporate the unique billing rate structure and applying the same calculations the electric utility uses to determine the facility’s energy costs.

To illustrate how hydraulic modeling and electric utility billing rate modeling can be used together as an effective energy management tool, this paper will present the results of three (3) hydraulic modeling projects where hydraulic modeling and billing rate modeling were used to evaluate the final energy costs for multiple pumping operation scenarios. The case studies will demonstrate how in some cases, optimizing for minimum energy usage may not be the lowest energy costs scenario.

Specifically, this presentation will present the following:

· General overview on how hydraulic modeling can be used to identify and evaluate multiple types of energy optimization opportunities.
· Demonstrate how electric billing rate structures such as time-of-use and demand rates can be leveraged to reduce energy costs by using storage capacity to reduce demand charges and reduce energy usage during on-peak hours.
· Demonstrate how hydraulic modeling and electric billing rate modeling can be used together to identify unexpected opportunities to minimize energy costs while also maintaining water availability and quality.
· Provide an overview of strategies to reduce pumping and distribution energy costs by managing water storage tank levels.
· Provide information on energy markets and industry trends that will impact the future value of hydraulic and billing modeling.

For more information, please contact the author at blisk@hazenandsawyer.com.

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