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Case Study

Learn how an electrical distribution utility customer drove economies of scale.

Integration of Renewables at Snohomish County Public Utilities District

Snohomish County Public Utility District (PUD) is committed to meeting load growth first with conservation, and then with clean renewable resources. When the PUD recently grew its wind generation from 0 to 8% in just two years, the addition of intermittent wind generation magnified a yearly spring runoff problem. In the Northwest, winter snow begins to melt and the wind starts to blow in March, April and May. These seasonal events drive peak production of electricity on the shoulder of the Western Interconnection’s peak load requirements that follow in June, July and August. With production and consumption mismatched and swinging widely north to south, east to west, day to night and rain to shine, the PUD looked to distributed energy storage, both to address the intermittency of renewables and to more broadly support the transmission and distribution grid.
Join Snohomish PUD on a tour of the first MESA-based energy storage system (2:31).

Today’s Energy Storage Systems

Today’s energy storage industry is a smorgasbord of batteries, power control systems and voltage converters, all requiring custom engineering to knit the system together. “One of the challenges with energy storage projects is that everyone is its own black box project. Every time you do one of these projects, you have a lot of non-recurring engineering costs that are required to make a battery system talk to the power conditioning system, talk to the utility systems like SCADA and DMS,” said Craig Collar, Assistant General Manager for Power, Rates and Transmission, Snohomish PUD. For the PUD to deploy more than one energy storage project, energy storage had to become scalable, replicable and cost-effective for customers. The PUD also recognized the advantage of deploying different battery chemistries to address different use cases. With different energy storage technology in each project, standards are needed for consistent communications interfaces and to provide the maximum value to the utility.

Energy Storage Systems of Tomorrow

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The PUD helped create and found the Modular Energy Storage Architecture (MESA) Alliance. The MESA Alliance has the goal of transforming the energy storage industry through the establishment of open, non-proprietary specifications and standards for energy storage systems. By standardizing communication interfaces, utilities can reduce the complexity of energy storage systems, reduce the non-recurring engineering, and choose from interchangeable components such as different battery chemistries. With storage architected in a more standardized fashion, utilities can focus innovation in software intelligence to address new use cases.“Our mission is to meet our load growth first with conservation and then with clean renewable resources. Those clean renewable resources by their very nature are intermittent. We see the MESA initiative in energy storage in general and the software this project represents as really being the essential elements of our being able to do that in a cost-effective manner.” — Craig Collar, Assistant General Manager

Doosan GridTech® Software and System Design


Snohomish PUD is partnering with Doosan GridTech to design and deploy three MESA-based energy storage systems controlled by the Doosan GridTech Intelligent Controller® (DG-IC®). Fleet optimization and scheduling is provided by the Doosan GridTech Distributed Energy Resource Optimizer® (DG-DERO®). The diagram shows the major components of the systems as currently planned. The first system, MESA 1a, was dedicated on January 15, 2015.

The DG-DERO runs in the utility data center and is built on open standards such as MESA, OpenADR, Web Services, ICCP, and DNP3. Drawing on its suite of bulk power applications, DG-DERO maximizes the economics of the fleet of energy storage systems by matching each storage asset to the most valuable mix of opportunities on a day-ahead, hour-ahead and real-time basis. Applications, or ways that DG-DERO will optimize the value of distributed resources for Snohomish, include:
  • Energy Arbitrage – Buy low, use or sell high
  • Transmission Constraint Relief – Avoid energy congestion
  • Best Market – Avoid unfavorable (spot market) purchases
  • Energy Imbalance Mitigation – Protect your energy forecast
Built on MESA standards, the DG-IC integrates energy storage systems from several vendors into the District’s communication and control systems, while providing flexible operating modes that can be configured and scheduled to respond to constantly evolving use cases. Use cases, or ways that energy storage can increase renewable energy use and improve grid efficiency and resiliency, can include:
    • Renewables integration
    • Frequency regulation
    • Load balancing
    • Peak shifting
    • Voltage support
    • Islanding
Under coordinated and automatic control, the fleet of energy storage systems will provide better integration of renewable energy, minimize exposure to market volatility, and mitigate voltage and current issues while improving grid reliability, flexibility and performance.

Snohomish Energy Storage Portfolio: Project Technology and Partners

Project Owner: Snohomish County Public Utility District Software provider/system design: Doosan GridTech Energy Storage System 1a: Parker Hannifin Power Conversion System (PCS) and a GS Yuasa International Ltd.-manufactured 1 MW (500 kWh) Lithium-Ion battery supplied by Mitsubishi International Corporation Energy Storage System 1b: Parker Hannifin PCS and an LG Chem Ltd. 1 MW (500kWh) Lithium-Ion battery Energy Storage System 2: 6.4 MWh UniEnergy Technologies vanadium flow battery system Additional Partners: Alstom is the supplier of the EMS, SCADA and DMS platforms.DOE’s Pacific Northwest National Laboratory is developing use cases. Research Institution: University of Washington

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