Applications

See the menu at left for discussions of individual storage applications.

Transmission Support and Avoidance of Congestion Charges

Electricity storage improves the performance of the transmission system to the extent that it increases the load carrying capacity of the transmission system, a benefit accrues if additional load carrying capacity defers the need to add more transmission capacity and/or additional T&D equipment.  This provides a benefit to the owner of the transmission system.

Utilities that do not own transmission facilities pay those who do for transmission “service”.  Thus, when non-owners use the transmission system to move energy from one place to another the owners impose an “access” charge to cover carrying charges and operations and maintenance costs.  Today, transmission capacity for a transaction can include an access charge, which is scaled with overall power flow in the corridor, not just a linear relationship based on needed power flow.  The end user may avoid these charges by installing electricity storage.

NOTE: avoided congestion charges is an established financial opportunity. It is related to too many kWh for the Transmission system to transmit based on rated capacity.  The price is set by ISOs.

The Transmission Support application is really used to modify the “electrical performance” of the system, per the EPRI/DOE Handbook. Discharge, the storage duration is probably just a few seconds.

Type

Description

Transmission Stability Damping

Increase load carrying capacity by improving dynamic stability.

Sub-Synchronous Resonance Damping

Increase line capacity by allowing higher levels of series compensation by providing active real and/or reactive power modulation at sub-synchronous resonance modal frequencies.

Voltage Control and Stability

1. Transient Voltage Dip Improvement: Increase load carrying capacity by reducing the voltage dip which follows a system disturbance.

2. Dynamic Voltage Stability: Improve transfer capability by improving voltage stability.

Under-frequency Load Shedding Reduction

Reduce load shedding needed to manage under-frequency conditions which occur during large system disturbances.

 

Updated May 2009