IEEE Power & Energy Magazine - November/December 2014 - 104

in my view

Ross Baldick

flexibility and availability
can the natural gas supply support these needs?

There are several reasons
to embrace the natural-gas-fired generation of electricity, including relatively
low emissions compared to coal and
oil and the cost-effectiveness of building and operating new plants that can
be utilized in cogeneration configurations. at my school, the University
of Texas at austin, we have generated electricity on campus at our own
combined-cycle plants for decades.
Furthermore, the campus's need for
low-grade heat utilizes a greater fraction of the primary input energy than
is possible with stand-alone combinedcycle plants used just for electricity production. That is, cogeneration
reduces air emissions and decreases
the amount of fuel used per unit of utilized energy compared to a stand-alone
combined-cycle configuration without
use of waste heat. such cogeneration
options are realistically only possible
with smaller generation stations that
are typically natural-gas fired since
larger coal, oil, and nuclear generators
can rarely be scaled for a waste heat
use and are typically not suitable for
urban environments.
hydraulic fracturing in north america has greatly expanded the potential
supply of natural gas. In general, natural
gas has become relatively inexpensive
in regions that have allowed hydraulic fracturing, and average natural gas
prices are likely to stay low for the
foreseeable future. extended periods of
moderate and stable natural gas prices
Digital Object Identifier 10.1109/MPE.2014.2340774
Date of publication: 20 October 2014

104

ieee power & energy magazine

will further encourage the demand for
natural gas, which will result in a resurgence of its use in manufacturing and
electricity generation. however, not
all regions of the United states (or all
countries) are willing to utilize hydraulic fracturing. Moreover, U.s. natural
gas prices have recently increased, and
there can be occasional interruptions to
the natural gas supply due to weather or
other events, resulting in price volatility during these periods. Consequently,
the desire to diversify energy supply among resources could also result
in some future expansion of nongas
resources or the addition of dual-fuel
capability to generators that use natural
gas as their primary fuel.
natural-gas-fired generation can be
designed and tuned to meet operational
flexibility requirements. This ability to
provide both fast start-up and ramping
facilitates the integration of intermittent renewable energy resources into
the electric system. This combination
of resources also reduces air emissions
compared to a thermal-only portfolio
and will encourage the further expansion
of natural-gas-fired generation capacity
as a complement to intermittent renewables. The increase in natural-gas-fired
capacity and the associated increase in
natural gas consumption will result in
natural gas being an ever-more major
player in thermal generation portfolios.
To utilize the flexibility of naturalgas-fired generation, however, gas supply must also be relatively flexible, and
the gas infrastructure must support these
needs. The flexibility and availability
of natural gas supply is the focus of my

concerns in this "In My view" column.
Flexible resources and fuel supplies
will be required to meet increases in
intermittent renewable capacity and the
resulting greater variability and uncertainty of the net load, which is the difference between the gross load and the
intermittent renewable production.
To understand why the flexibility of
the gas supply is a concern, first consider
the case without intermittent renewables.
In the absence of large-scale storage,
the system generation must supply the
instantaneous load at every moment.
Demand levels are critically tied to ambient temperature and other weather-related
variables. The availability of high-quality
weather forecasts, together with modern
statistical and forecasting techniques, has
allowed for the very accurate forecasting
of electrical and gas demand. The dayahead forecasts of electric load are generally quite accurate. Consequently, in the
absence of significant variable generation, the need for natural gas supply for
electric generation can usually be well
judged for day-ahead electricity markets.
natural gas markets have liquid trading
opportunities within this day-ahead context, at least for Tuesday through saturday delivery. however, the timing of these
markets is not well aligned with the timing of various electricity markets, and the
absence of liquid weekend trading means
that most, if not all, deliveries for sunday,
Monday, and public holidays are established on Fridays. There is a mismatch
between the "electric day" (midnight to

(continued on p. 100)
november/december 2014

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