Issaquah plans a 60 kWh sodium-ion battery for its emergency barn

Emerald Battery Labs, a Seattle-based sodium-ion battery manufacturer, announced on October 29 that it will develop a 60 kWh battery system for Pickering Barn in Issaquah, Washington. The plan pairs that storage with the 64.9 kW-DC solar array already on site, so the city's resilience hub can eventually carry critical loads when the grid goes down.

A $671,000 grant from TransAlta Centralia Generation LLC supports part of the work. The city's October council calendar lists Agenda Bill 9256 for the TransAlta grant and the Pickering Barn battery storage. As Microgrid Media points out, that official record backs up the municipal project and the grant action, while Emerald's release supplies the vendor, the chemistry and the 60 kWh design.

For now the battery exists as a design. Certification, permitting, procurement, installation, controls integration and commissioning all come before it can carry a single critical load. Issaquah still has to answer the questions every facilities director and emergency manager will face on their own site: how much power, for how long, and for which loads.

A busy barn, upgraded in phases

Pickering Barn belongs to Issaquah's Resilience Hub Initiative, which picks public facilities that can deliver essential services and community support during emergencies. The city's Solar + Storage Microgrid Feasibility Study flagged the barn as a priority site for a community resilience microgrid. The rest of the year it works as a gathering place, home to a weekly farmers market from May through October.

The city installed heat pumps at the facility in 2025 and added the solar array earlier in 2026, which counted as the project's first phase. Storage is the second phase. According to Microgrid Knowledge, the upgrades are meant to work together: cut energy costs, use more renewable energy and give other public buildings a working example of how they can support community resilience. Issaquah has some history here: in 2023 it became the first city in Washington to earn LEED Gold certification from the U.S. Green Building Council.

The battery is the piece that would let the barn disconnect, or island, from the grid and run critical loads on stored solar energy. The array on the roof does not make the barn a microgrid on its own. As Microgrid Media lays out, separating from the utility grid takes an islanding strategy, inverters and controls set up for it, protection, switching and a defined set of critical loads.

Emerald's job description fits that list: battery integration with the city's existing solar and electrical hardware, energy management, battery management system communications and system-level safety validation. For operators who already have a rooftop array, that scope suggests a battery retrofit reopens the electrical design around the panels. It is more than adding a cabinet next to them.

How long 60 kWh actually lasts

Sixty kilowatt-hours is a tank size, and a tank size alone can't tell an emergency manager how many hours a warming center stays open. Run time depends on the battery's usable capacity, the inverter's power rating, the state-of-charge reserve held back, how much the solar produces, conversion losses, and the size and priority of whatever stays energized. The city and Emerald have not released a power rating or a verified outage-duration target.

The city's own solar estimate helps with scale, but only up to a point. Issaquah describes the array as a 65 kW project expected to generate 53.74 MWh a year and cut municipal electricity costs by more than $6,000 a year. Spread evenly over 365 days, that works out to roughly 147 kWh a day. On paper, an average day produces more than twice what the battery can hold.

Averages are where the comfort ends. An annual figure smooths out the seasons and says nothing about cloudy stretches or the demand from a crowded building. Those gaps matter for anyone judging how far a 60 kWh battery could stretch during an outage. The savings figure tests something else: it reflects the array paying its way on normal days while connected to the grid. Outage service depends on what the battery and controls can deliver once the barn is islanded.

The load list is what turns the tank size into a service promise. The city intends the barn to work as a warming and cooling center, and the resilience-hub idea also covers device charging and other support. Still, the published materials don't say which circuits the battery would keep alive.

HVAC, lighting, communications, refrigeration, charging and accessibility equipment draw very different amounts of power and energy. For a city planning shelter capacity, the order in which loads get dropped as the battery drains matters as much as the capacity figure itself.

Sodium-ion and the UL queue

Sodium-ion chemistry is an alternative to the lithium-ion technology commonly used in stationary storage. It swaps lithium for more abundant sodium-based materials. Developers aim it at jobs where cost, a broader supply base and thermal behavior count for more than packing the most energy into the smallest box. Emerald says its cells offer better thermal stability, long cycle life and no dependence on lithium or cobalt. Microgrid Media is careful to call these manufacturer claims for a proposed product. They are not operating results from Pickering Barn.

That puts the certification plan at the center. UL 1973 covers the batteries themselves in stationary applications. UL 9540 covers the complete energy storage system. UL 9540A, the third certification Emerald plans to pursue, is the test method used to evaluate thermal-runaway fire propagation. For a chemistry sold partly on thermal stability, 9540A is where that claim would meet a standardized fire-propagation test.

Emerald has said it will support the city through permitting and procurement once the design is final and the required certifications are complete. That sequence suggests certification sets the project's pace: the city's purchasing and permitting steps wait on the lab.

Two fair objections. First, passing those tests is a prerequisite for safety review and deployment, but it won't prove how the battery holds up over years in the field.

Second, 60 kWh is tiny next to utility-scale storage. For scale, Solar Builder reports that Madison Energy Infrastructure and CORE Electric Cooperative have launched a 50 MW / 200 MWh battery portfolio across three Colorado sites. It uses Tesla Megapack units, and all three projects are expected online by September 2027. That portfolio stores more than 3,000 times the energy planned for the barn, and its stated purpose is different too. CORE's chief energy supply officer, Chris Hildred, says the storage will help the co-op manage peak demand, control power costs and maintain reliable service across its system.

Microgrid Media's answer to the size point holds up: the barn is a community resilience hub, not a merchant storage plant earning grid-market revenue, so the right test is whether it carries the loads the city assigns it. The Colorado project also shows the kind of disclosure that makes planning possible. Because it is stated as both power and energy, anyone can see it delivers about four hours at full rated output. That is the calculation Pickering Barn's 60 kWh is waiting on.

Milestones before the first islanded hour

The remaining steps are documented, even if their dates aren't. Emerald has to finish the design and certify the system. After that, the city moves through municipal procurement and permitting, then installation, controls integration and commissioning.

Microgrid Knowledge presents the project as an example of municipalities adding battery storage to existing solar so public facilities can do more than their everyday jobs and keep services running during grid disruptions. That framing matters most for towns that already have panels on a public roof. For them, Issaquah's path from feasibility study to solar to storage is the part they can copy.

The clearest signal of what Pickering Barn can do will be two numbers the city hasn't printed yet: the battery's kW rating and a list of the circuits it will hold up. Once those exist, a planner in Issaquah, or in any town copying its model, can turn 60 kWh into hours of heat, light and charging, and decide whether that is enough.