Environmental Engineering Reference
In-Depth Information
lifetimes are likely to increase and the costs should decrease. Additionally, if a
large number of plug-in electric vehicles with proper control systems become
available, the batteries for these vehicles may represent a new way to match
energy sources to loads on a scale of interest to utilities. The implementation
of “smart grids” in two-way communication systems allows management of
both loads and sources. Just how much storage may be economical to install
and where to locate it are problems that are still under investigation.
At substation level, megawatt level batteries are now available and it is
expected that NaS batteries capable of delivering hundreds of megawatts
will be available soon.
Batteries in the megawatt range have also been used to delay upgrades of
transmission lines. For example, power may be transmitted from a generator
to a battery during nights (low load times) and used to supply peak power
in afternoons. Additionally batteries of this size are now used to smooth
fluctuations in power from wind farms. For large rapid transient needs, fly
wheels (not discussed in this volume) are also available. Thermal energy
storage seems to fit easily into the development of solar thermal systems and
is included in the plans for a number of major projects under development
when this topic was written. Heat pumps and solar-driven refrigeration sys-
tems are now available and undergoing further development.
If a large number of these systems are installed, they will exert an impact on
peak air conditioning and some heating loads. For large amounts of energy
storage (gigawatt hours), pumped hydroelectric systems and compressed air
systems are currently in use and show significant potential as cost-effective
means of increasing available storage. Permits for siting pumped hydroelec-
tric systems require time, suitable geological conditions, and large amounts
of capital. However, these systems are expected to have long useful lives and
can significantly reduce costs of integrating wind and solar energy into a
grid. Underground compressed air storage also requires specific geological
structures but such sites are expected to be more available than sites for new
pumped hydroelectric systems, particularly in the high wind regions of the
great plains of the United States.
References
1. Gyuk, I. December 2003. EPRI-DOE Handbook of Energy Storage for
Transmission and Distribution Applications. Report 1001834.
2. ERCOT Operations Report on EECP Event of February 26, 2008. www.
ercot.com/meetings/ros/keydocs/2008/0313/07.ERCOT_OPERATIONS_
REPORT_EECP022608_public.doc
3. Levine, J., and L. Hansen. February 2008. Intermittent renewables in the next
generation utility. Rocky Mountain Institute. Renewable Power Generation
Conference, Las Vegas, NV.
