Planning District Energy Decarbonization: Evaluating an Electrification Path for CenTrio Energy’s Western Avenue Steam Plant
Decarbonizing an operating district steam system is a challenge that equipment alone can't address. Utility providers, like CenTrio Energy, must determine how new technologies will interact with existing equipment, electrical infrastructure, customer loads, reliability requirements, and future phases of decarbonization efforts. CenTrio is working through those questions at Seattle’s Western Avenue Steam Plant.
Affiliated Engineers, Inc. (AEI) has planned and delivered district energy systems for public and private clients across the country for more than three decades. That experience spans central utility plants, steam and hot water systems, chilled water, thermal energy storage, electrical generation and distribution, and campus electrification. Understanding these efforts requires a broad understanding of how energy is produced, distributed, and used within connected buildings.
AEI uses existing-condition assessments, operating data, load analysis, modeling, and life-cycle cost analysis to understand those relationships and compare potential paths forward. The work can reveal where existing assets still provide value, where new capacity is needed, and how a decision in one part of the system affects another.
Determining What Existing Infrastructure Can Continue to Serve
Existing district energy systems represent substantial investments in plants, distribution infrastructure, and connected buildings. Decarbonization planning must consider how much of that infrastructure can continue to serve the system.
AEI’s work at Stanford University and the University of California, Davis (UC Davis) demonstrates how that analysis can lead to different answers. At Stanford, AEI planned and designed a campus conversion from steam to hot water, including a new central energy facility, building conversions, a new hot water distribution system, thermal energy storage, heat recovery, and new electrical infrastructure. At UC Davis, AEI established existing and future campus loads, quantified steam losses, and compared multiple thermal energy systems through life-cycle cost analysis before recommending a low-temperature hot water strategy using heat recovery, thermal energy storage, and future ground-source heat exchange.
Together, these projects demonstrate why district energy decarbonization strategies must respond to each system’s infrastructure, loads, operating requirements, and long-term goals.
AEI is applying this district energy planning experience as CenTrio evaluates opportunities to electrify and modernize its Western Avenue Steam Plant in Seattle. Existing fossil fuel infrastructure will continue to play an important role in resiliency and meeting peak thermal demands, while new low-carbon technologies will be phased in over time, handling an increasingly larger portion of the load.
Evaluating Electrified Steam Production at Western Avenue
CenTrio is planning an electrode steam boiler as their first step toward long-term decarbonization goals. AEI provided engineering design services to evaluate how the technology and the electrical infrastructure needed to support it will integrate with the existing plant while maintaining reliable district steam service.
AEI began with a predesign scoping effort to address key technical questions and establish a basis for CenTrio’s subsequent decisions about design, procurement, and construction.
Electrical capacity was a central consideration. The concept included a new electrical feeder from Seattle City Light (SCL). AEI developed medium voltage one-line diagrams and coordinated with SCL to evaluate the electrical infrastructure required to support the project.
At the plant, AEI evaluated multiple electrode boiler technologies and configurations, including options that could operate directly from medium voltage without a transformer. The team also studied potential equipment locations within the existing plant, including areas occupied by legacy boiler and emissions-control equipment.
Those siting decisions affect more than equipment arrangement. AEI considered constructability, modifications to existing infrastructure, operational continuity, and flexibility for future changes. Maintaining district steam service during potential future improvements was an important planning consideration.
Planning for Future Decarbonization Options
CenTrio’s longer-term strategy extends beyond an electrode boiler. AEI also evaluated steam-generating heat pumps, thermal energy storage, and a potential connection to a local chilled water district loop to help CenTrio understand how today’s decisions could affect future options.
The team also researched and navigated applicable local code requirements to ensure compliance and avoid triggering unrelated facility upgrades.
AEI is advancing the preliminary concept through the next phases of design, developing capital cost estimates, schedules, operational impacts, and key risks.
For established district energy systems, decarbonization planning means understanding where change creates value, where existing infrastructure can continue to serve, and what each option requires before making major investments.
Learn more about CenTrio Energy’s decarbonization efforts in Seattle.