IEEE Power & Energy Magazine - November/December 2014 - 48

150
Underground Storage

100

Gas Fields

Dec.

Nov.

Oct.

Sept.

Aug.

July

June

May

Apr.

Mar.

-50

Jan.

Feb.

(GWh)

-100
-150

0
20 3
04
20
05
20
06
20
07
20
08
20
0
20 9
10
20
11
20
1
20 2
13

4,500
4,000
3,500
3,000
2,500
2,000
1,500
1,000
500
0
02

Hours

figure 17. Natural gas: seasonal usage of storage facilities
in 2013.

figure 18. CCGT operating hours in Spain, 2002-2013.

In short, these criteria ensure that all LNG plants are
capable of operating at nominal capacity for between eight
and 13 days.
Underground natural gas storage capacity is fairly limited in Spain, as compared with other EU countries such as
France, Germany, or the United Kingdom. Nevertheless,
such capacity allows for:
✔✔ ensuring minimum supply in the face of long-term
failures
✔✔ providing interseasonal regulation
✔✔ providing intradaily regulation.
Since electricity production regulating units operate during
an increasingly limited number of hours, it is important to implement gas storage management strategies and demand-side policies to ease the operation of both the electricity and gas systems.
Moreover, operating hours for regulating units have decreased
over time, as illustrated in Figure 18, which shows a sustained
decrease in the operating hours of CCGTs from 2008 to 2013.

Concluding Remarks
CCGTs make possible the operation of electric energy systems with high renewable penetration such as the one in
Spain, and these plants therefore play a critical role in the
operation of such electric systems. This is the case because

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CCGTs provide reliable and fast backup to the uncertain and
intermittent production of most renewable plants, notably
wind- and solar-based ones.
On the other hand, CCGTs strongly link the operations of
the electricity and gas systems, making them highly interdependent. Due to the flexibility of the gas supply, via both LNG and
pipelines, CCGTs make the operation of the electrical system
both flexible and efficient. It is relevant to point out that such
flexibility is crucial in a system that is poorly interconnected
and has limited storage capacity, like the one in mainland Spain.
In the future, greater storage capacity, more interconnections, and a more efficient management of renewable
resources will all contribute to make CCGTs less critical to
the operation of Spain's electric energy system. A hub-based
gas market in Spain will enhance trading opportunities for
gas, which will eventually result in enhanced operation of
the CCGTs of the electric energy system and, ultimately, in a
more efficient operation of the entire system.
LNG facilities play a critical role in this efficiency, as
they enable great flexibility in the operation of the gas system and allow a tight interconnection between gas and electricity. Moreover, LNG plants link the electricity system of
Spain to international gas markets.
It is necessary to implement efficient pricing mechanisms
in both the gas and electricity markets, including commodity (electricity and gas) prices and infrastructure-use tariffs
(transmission facilities for gas and electricity), in such a
manner that an efficient operation of these two interconnected markets can flourish. In addition to short-term signals,
these prices need to embody appropriate long-term signals
that stimulate investment in both electricity and gas production facilities.

For Further Reading
R. de Dios, F. Soto, and A. J. Conejo, "Planning to expand?"
IEEE Power Energy Mag., vol. 5, no. 5, pp. 64-70, Sept.-
Oct. 2007.
J. M. Morales, A. J. Conejo, H. Madsen, P. Pinson, and
M. Zugno, "Integrating renewables in electricity markets.
Operational problems," in International Series in Operations Research & Management Science. New York: Springer,
2014, ch. 1.
S. Gabriel, A. J. Conejo, B. Hobbs, D. Fuller, and C. Ruiz,
"Complementarity modeling in energy markets," in International Series in Operations Research & Management Science. New York: Springer, 2012, ch. 1, 3, 10-12.

Biographies
José Gil is with Gas Natural Fenosa, Spain.
Ángel Caballero is with Gas Natural Fenosa, Spain.
Antonio J. Conejo is with The Ohio State University,
Columbus, Ohio.
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november/december 2014

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