L. Vesely, K. Sedlacko, D. Jones
Echogen,
United States
Keywords: long-duration energy storage, thermal storage, alaska, railbelt
Summary:
Long-duration energy storage (LDES) is a critical component of the energy infrastructure as the world transitions to renewable sources such as wind and solar. Because these energy sources are inherently intermittent, due to factors like time of day, weather, and seasonal variation, energy generation from these sources is not consistently available. However, during periods of surplus production or decreased demand, long-duration energy storage systems can capture and store energy for extended periods, making that energy readily available during times of low renewable output or high demand. As the energy landscape shifts, advanced energy storage solutions and strategic initiatives are emerging to enhance grid resilience and reliability. One such initiative is the Railbelt Innovation and Resiliency (RIR) project, which plays a pivotal role in modernizing Alaska’s Railbelt electrical grid. Central to this initiative is a proposed Pumped Thermal Energy Storage (PTES) system, developed by Echogen Power Systems and in partnership with Westinghouse Electric Company. The project will implement a 50 MW / 1,200 MWh PTES facility, strategically co-located with the Healy Power Plant in central Alaska. This technology utilizes electricity to operate a closed-loop supercritical CO₂ heat pump cycle, storing energy in thermal reservoirs for later dispatch during periods of high demand. The Alaska Energy Authority (AEA) outlines that Alaska’s Railbelt faces several challenges: an aging infrastructure, limited interregional transmission flexibility, constrained ability to integrate variable renewables, and a looming retirement of thermal capacity units. These constraints expose the system to supply shortfalls, reliability risks, and high costs during peak events or outages. The RIR seeks to mitigate these structural risks through grid-hardening investments, improved redundancy, and energy storage deployment. There are several advantages to integrating PTES into Alaska’s Railbelt grid. Unlike short-term battery systems limited to 2–4 hours, PTES is designed for 10+ hours of continuous output, making it suitable for bridging multi-hour gaps during low wind/solar production or during forced outages. This matches the operational stress patterns in the Railbelt region, where supply gaps may last many hours. Furthermore, PTES offers operational flexibility by decoupling the heat pump cycle from the power conversion cycle. This enables independent control of the charge and discharge rates, allowing for flexible operational control. Lastly, PTES mitigates certain supply chain constraints commonly associated with electro-chemical storage systems, making it a viable long-term option. In sum, the RIR initiative’s alignment with PTES underscores the transformative potential of long-duration energy storage in the Alaska Railbelt context. By enabling extended dispatch, mitigating reliability risk, and complementing network upgrades, LDES can act as a keystone technology in the path toward a more resilient, lower-carbon, and cost-effective grid. The POLAR project stands as a flagship demonstration: if successful, it may catalyze broader adoption of thermal storage, and new business models for dispatchable, long-duration grid assets in challenging geographies.