Handbook of Energy Storage for Transmission or ... - W2agz.com

EPRI Proprietary Licensed Material
present during constant charging and discharging, regulation reserve may not be suitable.
Of the others, spinning reserve would likely be the most viable since cycling would be
relatively infrequent (a few times per year) and since this type of reserve power is the
most costly to provide by competing thermal plants. For purposes of this analysis,
spinning reserve is taken as the ancillary service provided by the VRB.
Alternatives
For this application, the VRB would compete with thermal plants in a competitive
marketplace. For purposes of the benefits analysis, the VRB is evaluated against typical
market prices for spinning reserve.
Control/Dispatch Strategy
The VRB would be charged to full capacity and kept in service to discharge its energy as
required. Depending upon the technical requirements, the pumps may be turned off and
the electrolyte tanks drained in order to minimize tare losses (full power could be
delivered in 1-2 minutes). The system would be cycled only a few times per year,
extending the useful service life of the equipment.
Prospects for Success
This application is a very good match for the VRB. The required cycling (i.e., the
number of events per year) is relatively low, there is an emerging competitive
marketplace, and it provides the opportunity for multiple applications (the energy storage
rating could be increased beyond the spinning reserve requirements to serve other
applications, such as peak shaving).
3.4. Windfarm Stabilization & Dispatch
Description
As the penetration of wind energy on a power grid grows to a significant portion of the
overall generation mix, system impacts such as frequency stabilization and system
reliability become increasingly important planning considerations. Wind energy has
always been penalized as non-dispatchable resource (e.g., by not qualifying for capacity
payments). Large-scale energy storage potentially overcomes these issues by absorbing
undesirable power fluctuations and providing firm, dependable peaking capacity.
This is of considerable interest in Europe as wind energy is approaching significant
penetration levels. Even today, the problems are present on smaller island grids where
windplant power fluctuations cause system frequency excursions.
Alternatives
In this application, the primary purpose of storage – whether provided by the VRB or
another storage technology – is to maximize the production and delivery of wind energy
during periods of high wind turbulence and ramping. In the absence of storage, grid
operators occasionally curtail production to ensure stability, forcing windplants to “spill”
otherwise valuable energy by feathering turbine blades or disabling selected turbines.
Vanadium Redox Battery 25