POWER June 2014 - 70

ELECTRIC POWER 2014 ROUNDUP
The Word for Gas Is " Flexibility "
As an ever-changing power mix and growing renewable contributions challenge
grid stability, flexible gas generation looks to be more important
than ever, panelists at ELECTRIC POWER 2014 reported.
Thomas W. Overton, JD
W
ith the gas-fired power sector in
continual flux, blessed by plentiful
gas supplies but faced with uncertain
fuel costs and competition from intermittent
renewable generation, plant owners must
make flexibility and responsiveness a priority.
That was the message from the natural gas
track at the ELECTRIC POWER Conference
held in New Orleans, April 1-4.
Flexible Operations
Rob James, product manager for Neuco,
discussed a project optimizing heat rate and
ramp rate at Dynegy's Independence combined
cycle plant in Osewgo, N.Y. The 1,042MW
dual 2 x 1 facility began bidding into
the New York Independent System Operator
frequency regulation market about four years
ago. Dynegy later retained Neuco to help
maximize the plant's capability for high-
ramp rate ancillary services. This meant finding
ways to optimize the dynamics of the
combined cycle process and enhancing dayahead
capability prediction.
By using sophisticated modeling software
to predict demand trends, the plant is able
to deploy its duct burners ahead of time to
increase steam turbine output and preserve
high-ramp rate gas turbine capacity. The
model then turns the duct burners off as soon
as they are no longer needed in order to maintain
plant efficiency. Timing the duct burners
is important when selling into the regulation
market because the gas turbines can reach
maximum output below total plant output
well before the heat recovery steam generator
(HRSG) heats up, which can compromise
the plant's committed ramp rate. If the duct
burners are timed properly, the plant can sell
all its power into the regulation market while
still bidding at gas turbine ramp rate.
Nikhil Kumar, director of energy and utility
analytics, Intertek Asset Integrity Management,
reviewed a study of combined
cycle and simple cycle gas turbine operating
performance from 2002 through 2012. The
study was intended to characterize trends
and effects of cycling operation. Not surprisingly,
the data showed substantial increases in
average capacity factors at these plants, but
also increased number of starts and ramping
episodes. This places greater stress on a plant,
meaning steps must be taken to increase equipment
resiliency. Among the countermeasures
that can help deal with increased cycling are
installing additional thermocouples in the
HRSG to better monitor temperature changes
and better monitoring and control of HRSG
chemistry. More effective steps can be taken
if planning begins at the design stage.
Flexible Design
Increased penetration from intermittent
renewable generation is challenging combined
cycle plant profitability as increased
cycling (see related article, " Managing the
Changing Profile of a Combined Cycle
Plant " in this issue) sends maintenance
costs up while lucrative baseload roles are
taken by wind and solar. However, renewable
generation rarely follows forecasts
precisely, leaving plenty of gaps needing
to be filled. Properly designed plants can
ramp quickly and stay profitable by pursuing
opportunities in ancillary markets, as
several speakers explained.
Omar Rubio of Siemens Energy described
two major ramping episodes in Germany and
California last year, when multiple gigawatts
of renewable generation came off the grid
over a short period of time, and grid operators
had to ramp up major amounts of conventional
generation to replace it. Such episodes will
only become more common, and that means
1. Gas projects roll on. Dennis Finn of Wärtsilä gives a report on a gas engine plant in Alaska during the ELECRIC POWER natural gas
track as panelists Udo Zirn, Chris Marks, and Joe Ferrari look on. Source: POWER/Tom Overton
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POWER June 2014

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