Grid Energy Storage System

Engineered for fast response, high power applications in grids and microgrids.

Energy storage systems are facilitating the modernization of electricity grids and are now a key distributed energy resource (DER) to ensure reliable delivery of reactive and active power given an evolving mix of traditional and renewable energy generation. As more solar and wind are interconnected, energy storage systems (ESS) must respond faster and cycle more frequently to ensure grid power quality and resiliency in a generation nameplate mix that includes growing amounts of utility scale wind and solar. Further, advanced energy storage systems are filling gaps in grid ancillary services as a result of continued global trends in the loss traditional sources including fossil based energy.

The provision of power-intense applications requires more advanced and optimized ESS architectures to achieve technical, cost and profitability targets.

Leveraging two decades of use in the grid, Maxwell ultracapacitor-based grid energy solutions deliver fast responding, high peak power grid storage utilizing field-proven energy delivery technologies and advanced utility grade control and communication systems.

Our highly scalable energy system is deployed either as an optimized battery-ultracapacitor energy storage system or as a stand-alone ultracapacitor system to deliver energy and power better, faster and for less than traditional battery storage systems. The system dispatches power and energy to the grid measured in cycle timeframes to minimize and eliminate costly transient grid events to serve the needs of mission critical grid and industrial applications. Maxwell’s advanced systems are deployed to stabilize frequency, provide voltage support, smooth renewable power output, provide synthetic inertia, bridging and ramping, and improve generator response.

System Building Blocks



















Ultracapacitors (supercapacitors) are the core technology powering the system. Unlike electrochemical battery systems, which are typically oversized to mitigate lifetime degradation related to heating (I2R) during high peak power delivery and frequent cycling, ultracapacitors store charge electrostatically which allows them to be rapidly and frequently charged and discharged while maintaining lifetime and very high c-rate equivalency. Typical operating temperature range is from –40 to 65oC. With over 8 million devices deployed in utility grids, Maxwell’s proprietary core technology has withstood the test of utility deployments globally to deliver reliable, resilient and durable performance required for grid operations.

Grid Modules

Ultracapacitor cells are combined into a series string and assembled into modules. The modules feature advanced voltage, temperature and cell balancing with an internal and external monitoring and communication system that is designed from the ground-up to ensure system reliability and long system-level life. Additionally, the module features Maxwell Technologies’ High Voltage Interlock Loop (M-HVIL™) to enable the advanced functionality of internal system fail-over, providing an additional level of safety to field assets.

Grid Energy Storage System

Ultracapacitor modules are installed in standard 19” rack systems combined with a communications gateway providing two-way communication for state of availability and state of health via Modbus TCP/IP or Process Field Net (Profinet) protocols.