When the transmission capacity of an electrical system is insufficient to adequately serve customer demand, the transmission system is said to be experiencing congestion. More transmission lines can be built to increase capacity. However, transmission congestion typically only occurs during periods of peak demand, which occur just a few times per year; capitol-intensive investments in new transmission capacity address problems that occur infrequently. Alternative solutions to alleviated transmission congestion have been devised, including generation curtailment, demand response programs, and various remedial action schema. Though not currently a common solution, battery energy storage systems can also provide transmission congestion relief. Technological and market trends indicate the growing production capacity of battery energy storage systems and decreasing prices, which indicate the technology may soon become a viable option for providing congestion relief. Batteries can provide multiple ancillary services, and so can concurrently provide value through multiple revenue streams. In this manuscript, the authors present a systematic review of literature, technology, regulations, and projects related to the use of battery energy storage systems to provide transmission congestion relief.

Residential-scale distributed energy assets, like residential electric water heaters, individually present a negligible load to the power grid. When aggregated, however, these assets can impart significant effects within a balancing area; they may be dispatched en masse to provide grid services. An aggregation of water heaters may be controlled to assume generator-like functions with the ability to effectively ''decrement power'' through dispatch of load. This resource study examines the capabilities of a 10,000 unit water heater aggregation by subjecting the aggregate to dispatch requests of various size and duration, then analyzing how the aggregate responds to and recovers from these requests. Results show that a large-scale aggregation of electric water heaters may effectively decrement power on the scale of megawatts when the dispatch request size and duration are appropriately considered.

Distributed energy resources like residential electric water heaters and residential batteryinverter systems offer a small amount of change to the grid individually. When aggregated however, these assets can cause major effects to the electric grid. Aggregating these resources allows them to take on generator-like functions with the ability to increment power and decrement power. The Western Energy Imbalance Market is an energy market offering 15 minute and 5 minute markets for energy transactions between balancing areas. Generation assets make increment and decrement bids. Traditionally the only entrants to this market have been large scale generators and large scale assets legally designated as generators. Aggregated distributed resources could offer the same increments and decrements from managing Thank you to Pr. Robert Bass and the rest of the power lab researchers, Manny Obi, Tylor Slay, and Leighton Clarke.