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Snohomish PUD Energy Storage Program Generates Insights for Future Grid Management

By Neil Neroutsos, Media Liaison and Jason Zyskowski, Senior Manager of Planning, Engineering & Technical Services Snohomish County Public Utility District (PUD)

At Snohomish PUD, it’s ingrained in our thinking that we take a long term view in planning for and investing in our energy resources amid a rapidly changing environment. We’re a utility that is constantly assessing a broad collection of options to meet our future needs.

As our utility adds additional renewable energy resources to its portfolio – much of which can be intermittent, such as solar and wind – energy storage continues to become a more economical means of managing reliability. We’re already seeing energy storage system prices come down – and not just the prices for equipment and hardware, but engineering time as we learn how to better design and operate the systems.

The PUD has installed two energy storage systems at local substations: the first includes a set of two large-scale lithium-ion batteries, and a second is based on advanced vanadium flow battery technology. Our engineers and project managers have learned that these systems are unique and you need to fully understand how to use each technology. For example, do you need 2 megawatts for three hours or 4 megawatts for six hours? And what are the systems’ charging and discharging limits?

We’ve learned that lithium-ion and vanadium flow systems have very different charging/discharging characteristics. Lithium-ion degrade over time as you cycle them, depending on how quickly you charge and discharge them and the number of cycles each day. The vanadium flow systems have a longer life limit – you can charge and discharge them as many times you want over a 20-year period. However, when you charge them, the energy you’re going to get isn’t as efficient. So you need to know your business use and how to best match it to the right type of battery.

Lithium ion battery storage

As part of our energy storage research, we’ve worked with Pacific Northwest National Laboratory to test use cases such as shifting energy from peak to off-peak times and using storage for load shaping to smooth out the rate of load changes. We’ve also partnered with the University of Washington and Bonneville Power Administration (BPA) to test a Distributed Energy Resource Optimizer (DERO) tool. It’s a software system that allows our Power Schedulers to optimize the value of our battery systems.

DERO interfaces with the utility’s IT infrastructure to get a live look at our load and resource status and communicate it back to our Power Scheduling system. It helps manage issues such as when an energy resource is removed from the system or when we see real-time changes in load forecasts and want to avoid imbalance charges from BPA.

We’ve also worked with our partners to use DERO to test how to coordinate transmission-level congestion relief. Another study with BPA looked at how demand response and battery storage could mitigate peak load demands.

Our team has learned that if you don’t have an easy way to control these battery systems, schedule them and monitor them in an automated fashion, you’re not realizing their full set of benefits. A large part of our success has come as a result of our work to standardize our battery operations, particularly how they communicate with each other, with our SCADA system and our power scheduling software.

Going forward, we’re now designing a third energy storage system as part of a Microgrid and Clean Energy Technology Center, located in Arlington, Wash. It will demonstrate multiple new energy technologies, including energy storage paired with a 500-kilowatt solar array. The system will be able to be “islanded” and run independently from the electrical grid. It also will demonstrate how PUD electric fleet vehicles can be used to benefit the electric grid via a vehicle-to-grid system that allows both charging and discharging into the grid.

The Clean Energy Technology Center will serve as the test load for the Microgrid and will showcase various technologies to the public, the business sector, researchers and other local agencies. The project’s multiple uses include grid resiliency and disaster recovery, renewable energy integration, grid support and ancillary services and the vehicle-to-grid component. The facility also could be utilized as an emergency operations site in the event of a major disaster, such as an earthquake.

Snohomish PUD’s energy storage program has greatly benefitted through $10.8 million in supporting grants from the Washington Clean Energy Fund.


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