IEEE Electrification Magazine - September 2015 - 40

By improving the efficiency of the thermal cycle, TES can
potentially serve renewable EES needs. A comparative advantage of TES over PSH and CAES is unrestricted by the storage
site's geological conditions. Another advantage is its low cost
and grid integrated when coupled with mature power generation technologies. The TES technology may continue to
advance as TES operating temperatures increase, and the
technology costs just a fraction of battery energy storage,
making it a viable economic option in EES applications. Using
TES for EES to shift the peak generation can also be a source
of additional revenue for a CSP plant, because the TES capital
cost is included in the CSP system, and the TES can be the
free energy storage for electricity storage.
Energy storage will be an enabling technology to allow
utilities to accommodate a high penetration of renewable
energy. Electricity storage is a unique utility power source in
that it can act as both a load and source of power and provide load shifting and both frequency and voltage regulation
services. CSP together with TES can be dispatched to the grid
over a long time frame for utility-scale storage, where energy-storage devices such as ultracapacitors and batteries can
provide short-term regulation services or DESS.

Conclusion
As renewable power generation grows rapidly, the ability to economically store a significant amount of electricity generated
from wind and solar energy sources helps ensure consistent
availability and reliability of electric supply. Combining renewable power generation and energy storage could overcome the
variability issue of power generation by renewable sources. It
could provide the opportunity for renewable energy to provide
power generation in increasing percentage of the electric supply reliably and sustainably. Integrating renewable power and
storage of excess electricity for peak power usage has significant and positive impacts on the grid and environment. First, it
can expand the renewable energy portion of total electricity
generation. Second, it can improve the peak load response. And
third, it can coordinate the electricity supply and demand
across the grid, and reduce the need of utility's spinning reserve.
The power supply flexibility offered by the energy-storage
methods will greatly improve the penetration of renewables
into the grid and transform the future energy supply-from
power generation to transportation-in achieving low- to nocarbon energy sources and serving a sustainable society.

Acknowledgment
We thank our NREL colleagues, Paul Denholm, Greg Glatzmaier, and Charles Kutscher, for their technology insights
and appreciate help from Alfred Hicks and NREL Communications. We also thank the U.S. DOE for SunShot funding
award DE-EE0001586.

For Further Reading
M. M. Hand, S. Baldwin, E. DeMeo, J. M. Reilly, T. Mai, D. Arent,
G. Porro, M. Meshek, and D. Sandor, eds., Renewable Electricity
Futures Study (4 vols.), NREL/TP-6A20-52409, NREL, 2012.

I E E E E l e c t r i f i cati o n M agaz ine / SEPTEMBER 2015

M. Marquis, S. C. Albers, and E. C. Weatherhead, "2011: for
better integration, improve the forecast," Solar Today, vol. 25,
pp. 52-53, Sept./Oct. 2011.
C. Kutscher, "Does utility-scale renewable energy require
massive electric storage?," Solar Today, vol. 24, no. 2, p. 225,
Mar. 2010.
Electricity Storage Association. [Online]. Available: http://
www.electricitystorage.org/about/welcome.
MIT Energy Initiative. (2015, May). The future of solar energy: An Interdisciplinary MIT Study led by the MIT Energy Initiative. Appendix C-Energy storage systems for the electric
power sector. [Online]. Available: http://mitei.mit.edu/
futureofsolar.
P. Denholm, E. Ela, B. Kirby, and M. Milligan, "The role of
energy storage with renewable electricity generation," Tech.
Rep. NREL/TP-6A2-47187, NREL, Jan. 2010.
P. W. Parfomak, "Energy storage for power grids and electric transportation: A technology assessment," Congressional
Research Service 7-5700, Mar. 27, 2012.
U.S. Department of Energy, "Grid energy storage," DOE
Rep., Dec. 2013.
S. Patel. (2014, Apr. 30). The big picture: Storage snapshot.
Power: Business and Technology for the Global Generation
Industry. [Online]. Available: http://www.powermag.com/thebig-picture-storage-snapshot (accessed May 2014)
D. Biello, "How to use solar energy at night," Sci. Amer., vol.
300, Feb. 2009.
Z. Ma, G. Glatzmaier, and C. Kutscher, "The thermal energy
storage solution," Solar Today, vol. 26, no. 3, May 2012.
R. A. Huggins, Energy Storage. New York: Springer, 2010.
Navigant Research, "Community, residential and commercial energy storage," Navigant Rep., 2014.
NREL ESIF Home Page. [Online]. Available: http://www.nrel.
gov/esif/
B. Sorensen, Renewable Energy Conversion, Transmission, and
Storage. New York: Academic Press, Nov. 2007.

Biographies
Zhiwen Ma (zhiwen.ma@nrel.gov) is a senior engineer in
the Thermal Systems Group, National Renewable Energy
Laboratory.
Ahmad Pesaran (ahmad.pesaran@nrel.gov) is the manager of the Energy Storage Group, National Renewable
Energy Laboratory.
Vahan Gevorgian (vahan.gevorgian@nrel.gov) is a senior
engineer in the National Wind Technology Center, National
Renewable Energy Laboratory.
Don Gwinner (don.gwinner@nrel.gov) is a senior communicator in the Communications and Public Affairs Office,
National Renewable Energy Laboratory.
William Kramer (bill.kramer@nrel.gov) is the principal
research engineer at the Energy Systems Integration Facility, National Renewable Energy Laboratory.

http://http:// http://www.electricitystorage.org/about/welcome http://mitei.mit.edu/ http://www.powermag.com/the http://www.nrel

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