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Wastewater Treatment Plant Microgrid with Tier 4 Diesel Generators

Solution Overview

A microgrid is a local energy grid that can disconnect from the traditional grid and function autonomously without disrupting operations.[1] During the 23rd Ave Wastewater Treatment Plant (WWTP) Power Redundancy study, Phoenix partnered with APS to install a microgrid that would serve both the city's power redundancy needs and APS's long-term goals.[1] This approach improves the sustainability and resilience of the surrounding community's electricity grid, particularly for critical water and wastewater treatment infrastructure.[1]

Technical Components

The microgrid runs on diesel generators, which APS identified as the optimal fuel source to ensure reliable operation.[2] As part of the installation, Tier 2 generators were replaced with more stringently regulated Tier 4 generators which significantly reduce emissions.[1] The bidirectional substation allows the microgrid to take energy from the main grid, while also letting it flow back.[2] APS built in the ability to add batteries and photovoltaic systems to the microgrid very quickly and easily, with everything already in place for plug-and-play installation.[2] The microgrid was constructed with renewable energy and storage in mind, allowing for swift conversion to 100% renewable energy if Aligned Data Centers requests it.[2] When there is a fluctuation outside of the norm, the microgrid machines will automatically turn on and support the grid as well as securing the site.[2] In times of crisis, the microgrid can use its own local energy generation from solar energy generation systems, emergency generators or an on-site battery system.[1]

Implementation Details

In 2016, Arizona Public Service Co. announced it would build a 63 MW microgrid with Aligned Data Centers, as part of the utility's push to build the 'grid of the future.'[2] The 63 MW APS microgrid was completed by 2017, one year after its announcement.[2] While Aligned paid for part of construction, APS recovered the remaining costs from ratepayers.[2] Arizona regulators approved a number of programs for APS to recover costs for new technologies through the rate base in the past, including an in-house rooftop solar program.[2] The APS microgrid was constructed on top of the roof of a converted building.[2] Additional power redundancy studies will be conducted at different facilities and microgrids will be installed at those facilities identified to show a benefit to the power redundancy needs at those locations.[1]

Benefits and Impacts

The microgrid can take the load from the data center offline to provide 24/7 power in times of outages.[2] Once the crisis is resolved, the microgrid can then be connected to the traditional grid.[1] The microgrid is useful if energy generation in the surrounding community is disrupted and can provide resiliency and stability to the grid.[1] The microgrid illustrates how the utility is finding ways to relieve congestion on transmission lines, leverage grid services and boost the resiliency of the grid.[2] In times of crisis, this capability is important to the continued operation of water and wastewater treatment plants.[1]

Climate Adaptation Relevance

The implementation addresses power disruption risks during extreme weather events and other climate-related crises. Comparable projects demonstrate the critical need for power redundancy, as Hurricane Sandy left the service area of the Passaic Valley Sewerage Commission (PVSC) in Newark, New Jersey, without power for 72 hours.[3] Phoenix's approach promotes development of community-wide energy projects, including microgrids, that improve the sustainability and resilience of the surrounding community's electricity grid.[1]

[1]: City of Phoenix. (n.d.). Phoenix Climate Action Plan. [2]: Utility Dive. (2017). APS completes 63 MW microgrid in Phoenix. [3]: Passaic Valley Sewerage Commission. (n.d.). Hurricane Sandy Impact Report.

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