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CASE STUDY

Pump Overhaul and Sequencing PG&E, Northern, California

Situation

This California water district is a public retail water purveyor with a service territory of 47 square miles delivering approximately 18 billion gallons of water annually to 13 distribution zones. Their existing water pumping and storage system consists of 28 groundwater wells, 22 booster stations, three water treatment plants, and 34 reservoirs with a 90 MG capacity. Well pumps are used to fill reservoirs for disinfection and blending, and booster pumps distribute source water to the distribution zone through reservoir level on-off controls.

To operate its water pumping and storage system, the District’s consumes 36.7 million kWh of electricity annually, or an average of 1,403 kWh/MG pumped. Typically, water distribution consumes between 700 kWh/MG to 1,200 kWh/MG pumped (and anywhere from 700 kWh/MG to 1,800 kWh/MG pumped for groundwater sources).

Solution

Lincus engineers proposed a multi-pronged solution that would yield up to 2,769,465 kWh in annual energy savings.

Pump Efficiency Improvements: Lincus’ engineers identified 10 booster pumps and four well pumps that could be overhauled to elevate the District’s overall plant efficiencies from 57.9-66.9% to 68-72%. This improvement would yield 1.25 million kWh (or 12%) of annual energy savings and $161,651 in annual utility costs. With an additional $118,202 in utility incentives, this measure would offer a payback of 3.8 years.

Well Pump Sequencing: By optimizing the sequencing of the District’s 24 well pumps so that pumps with lower energy intensity are prioritized, Lincus discovered another 462,177 kWh (or 2%) in annual energy savings and $59,593 in annual utility costs. With an additional $36,974 in utility incentives, this measure would offer a payback of 2.7 years.

Zone Optimization and Sequencing: Lincus recommended the installation of a pressure reducing valve (PRV) so that a subzone of the District’s Zone 4 could be gravity fed by neighboring Zone 5, rather than relying on boosters in one of Zone 4’s existing pump station to maintain pressure (as under the pre-existing arrangement). As a result, this would eliminate the need for the boosters to provide additional head to maintain pressure in the subzone, and allow them to be sequenced based on energy efficiency. This would yield an annual energy savings of 526,441 kWh (or 5%) and $74,583 in annual utility costs and address customer complaints of low water pressure in that subzone. With an additional $42,612 in utility incentives, this measure would offer a payback of 3.5 years.

Booster Pump Sequencing: The energy intensity of pumps varies throughout the District’s system. By installing kW meters and using existing flow meters to sequence 47 booster pumps that fill common reservoirs and zones, the District would be able to prioritize pumps with lower energy intensity to meet system demands. This measure would yield an annual energy savings of 527,149 kWh (or 4%) and annual utility savings of $74,683. With an additional $54,926 in utility incentives, this measure would offer a payback of 5.7 years.

Results

Water Infrastructure and System Efficiency (WISE™) Program:The Lincus WISE™ program is a comprehensive turnkey solution for Municipalities which offers no-cost engineering services, project support, and cash incentives. Lincus uses a holistic approach, combining existing pump tests, energy audits, and hydraulic modeling to evaluate how a water reclamation facility can optimize its performance. In this project, Lincus completed its review of the system and overall analysis in a single phase. Lincus engineers conducted an onsite assessment to understand system operations, then developed a savings analysis to show payback based on overhauling and sequencing pumps within the system.

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