This summer, Snohomish County Public Utility District (PUD) will deploy an innovative energy storage system that aims to transform the marketplace and how utilities manage electric grid operations.

The PUD, based in Everett, Wash., and its principal partner, 1Energy Systems, will install the Modular Energy Storage Architecture (MESA) at multiple utility substations. The system will provide a standard, nonproprietary, scalable approach to energy storage. With it, in the future, utilities and grid operators would be able to choose interoperable components – batteries, power converters and software – to meet their specific needs with energy storage systems.

effective energy storage will reduce line congestion and transmission losses

“Today, devoid of standards in energy storage systems, you’re essentially getting black boxes — each one different, each with a different interface, and each requiring a different way of integrating it into your network,” said PUD General Manager Steve Klein. “It becomes a nightmare in terms of operational functionality, engineering and cost.” The PUD program has several objectives, including:

  • Integration of intermittent energy projects through energy storage and information technology;
  • Demonstration of dispatch of energy storage resources from utility energy control centers; and
  • Improved reliability and reduced cost of intermittent and distributed generation resources.

“The MESA system promotes the expanded application of plug-and-play type energy storage systems to address the needs of today’s electric grid, which increasingly depends on intermittent energy resources such as wind and solar,” said Klein.

The PUD energy storage program will include two, large-scale lithium ion batteries, one built by LG Chem and a second by Mitsubishi-GS Yuasa. Additionally, the PUD will deploy four strings of advanced vanadium flow batteries contained in 21 shipping containers, which will be built by UniEnergy Technologies, a PUD business customer. The batteries will be sited at substations in the utility’s service area.

System Operations

Energy storage could help resolve a broad range of issues related to electric grid operations. Storage offers benefits related to frequency and voltage support, and could reduce the need to maintain spinning reserves for backup.

Controls integration and optimization software is one of the keystones of the PUD storage program. The control system will involve the different storage batteries, each with its own performance characteristics. The software will also integrate multiple types of renewable energy and manage demand response. The control system infrastructure is the next critical technology for utilities and the energy storage industry, advancing from merely demonstrating individual energy storage projects, to creating an easily deployable, scalable solution that will be integrated with other grid assets.

The controls and optimization software will be integrated with the PUD’s Alstom SCADA system.

“It will change how we operate our SCADA systems in that our distribution systems have always operated one-way from generating resources,” said PUD Assistant General Manager of Distribution and Engineering Chris Heimgartner. “We are currently working with Alstom Grid to model our distribution system to incorporate energy storage.”


Successful energy storage systems, coupled with demand response – buildings acting as batteries – will let utilities adaptively absorb load and produce power in response to real-time grid conditions in order to provide stability. The PUD will identify up to five megawatts of load with commercial and municipal customers who have the capacity to shift their energy consumption to meet regional needs to absorb or shed load. Control signals between demand response customers and the utility will be managed through the utility’s operations center.

A 2012 report by the University of Washington and University of Michigan engineering departments highlighted these and other operational benefits, including the significant value of using storage and demand response for arbitrage between periods of high and low demand. It also called out the value of ancillary services, such as frequency control, reserve and voltage control. The report reinforced that effective energy storage will reduce line congestion and transmission losses. It will minimize the need to run expensive power plants and to spill renewable energy during times of excess energy supply.

Renewable Energy Integration

For the PUD and other utilities, energy storage is an invaluable tool in resolving issues related to intermittent energy sources. During times of high solar energy production, for example, batteries can be fueled for use later in the evening when customers are returning home and demand peaks.

“When our load and market prices are high, there’s potential to draw from the battery to minimize purchases,” said PUD Senior Manager of Power Supply Kelly Wallace. “Local renewable resources would provide the fuel, including small hydropower, biogas/biomass, solar and other distributed generation.”

Meanwhile, the PUD also plans to utilize energy storage to integrate a tidal energy pilot project in Puget Sound’s Admiralty Inlet. It will use an optimized battery charge/discharge algorithm to capture deep-cycle, variable frequency, variable-voltage energy, beyond what is currently commercially manageable. It will provide consistent, utility-grade power to the local distribution network.