Energy storage for the grid has generally been viewed as an optional add-on device to bolster reliability of the grid, as a special case reliability improvement in place of other measures, and as a tool for postponing infrastructure investment (Non-wires alternatives). These uses of storage have improved grid reliability at the margins but have not changed the essential resilience characteristics of the grid. This is because they do not fully capitalize on the key potential of storage: its use as a shock absorber for the grid.
In virtually all other complex systems, buffers are utilized to address volatility. The presence of a buffer provides a system with “springiness” or “sponginess” that makes the system able to tolerate a variety of perturbations. Communication systems smooth out the flow of data bits using jitter buffers. Logistics systems have buffers – they are called warehouses. Water and gas systems have buffers – they are called storage tanks. In each case, the buffer is some form of controlled storage that evens out irregular flows, thus reducing or eliminating the impact of volatility (whether fluctuation or interruption) in either source or use of the flow. Buffers are like shock absorbers – they provide the springiness that makes systems internally resilient to external disturbances. Electric power grids are unique among complex systems in that they lack shock absorbers, and so are inherently deficient in resilience and system utilization.
A power system that is increasingly comprised of large scale and distributed variable resources with increasingly dynamic loads from electrification requires grid shock absorbers. These energy storage devices must be embedded in and distributed throughout the grid as core infrastructure and integrated with grid control. Among the uses for an embedded storage device network are enabling renewables integration to meet 100% goals, reducing exchange of volatilities between bulk systems and distribution systems, and managing volatility exchange between bulk natural gas and electric generation systems. Embedded grid storage would not be used for bidding into wholesale electricity markets for supplying grid services or engaging in energy arbitrage.
The multi-use ability of this storage provides a potentially more cost effective solution while also adding significant improvements in resiliency. To be useful for the purposes just described, grid storage should be firm designable, firm dispatchable, securable, and assured of availability. To be effective, embedded storage should be distributed throughout a system, not concentrated in one or a very few extremely large units. It must be possible instantly to select operating modes and meet dynamic operating objectives as well as special objectives during resilience events. Such control must be able to operate on short time scales (sub-minute to sub-second). The necessary information to operate storage devices this way resides with the electric utilities.
Treating storage as a systemic upgrade across a regional grid includes deploying storage as a large number of smaller distributed units rather than as a few massive centralized devices can address the inherent “flexibility” required for our evolving system. Locating storage units at T/D interface substations; controlling groups of storage units as networks with individual fallback local control when grids are fragmented, it is feasible to significantly improve resilience and operational flexibility of power grids on a regional scale. Sizing total storage power ratings at 20% of the system peak yields a cost estimate that is well in line with other past and presently planned infrastructure upgrades.