IEEE Power & Energy Magazine - January/February 2017 - 18

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Gas turbine research and development (R&D) focuses on
improving the technical flexibility as well as economic profitability in electricity markets by minimizing startup times,
enhancing ramping capabilities, and reducing gas power stations' minimum stable output. The R&D priorities for gas
power plants are as follows.
✔✔ Using advanced materials to minimize cycling impact and cost. For CCGTs in particular, this involves
improving the balance of plant (or "BOP") and the
heat-recovery steam generator (HRSG), which often
Japan LNG
Europe (NBP)
limits startup times because the material and equipUnited States (Henry Hub)
ment cannot sustain higher temperature gradients.
Improved maintenance procedures in combination
figure 1. Gas pricing at different global trading hubs,
with new control instruments (potentially in real time)
2003-2016. The United Kingdom is representative of
can also optimize the startup procedure and reduce
European gas prices. NBP: national balancing point.
startup times.
(Source: International Energy Agency, Tracking Clean
✔✔ Increasing the use of monitoring and automation for
Energy Progress 2016, Paris: OECD/IEA, 2016.)
reliable startup sequencing. For CCGTs, additional
monitoring systems help identify stress and residual
life on steam turbines and HRSGs.
Open-cycle gas turbines (OCGTs) and aeroderivative gas
turbines (ADGTs) were always designed to provide flexibil✔✔ Maximizing load gradients during load changes. This
ity, but CCGT power plants were initially designed to operate
can be accomplished by using advanced materials and
mid-load to base load. Over the last decade, European CCGTs
real-time monitoring systems to minimize wear and
have already evolved to a point where it is common that they
tear of the material.
have a more flexible operating schedule. Since the mid-2000s,
✔✔ Improving combustion stability in gas turbines during
CCGT dispatch in some European regions has moved from
load change.
base load to mid-load to several startup/down cycles per day
✔✔ Reducing turn-down ratio and maximizing part-load
(Figure 3). Consequently, operating times decreased to as low
efficiency, especially of the gas turbine. This can be
as 1,300 h per year, while startup rates have increased from
achieved by improving the combustion process and
25 starts per terawatt-hour (TWh) to more than 80 starts per
burner materials.
TWh produced (Figure 4). The increased cyclic operation
Turbine-based plants today completely dominate the gas
exposes gas plants to more wear and tear and, consequently, power sector, but in some cases they could potentially face
increases cycling costs.
competition from reciprocating engines. In the past, reciprocating engines have mainly been
used only for small, decentralized
applications because turbine efMinimum Turndown
Hot Startup
Ramping
ficiencies are considerably lower
OCGT
for these applications (<10 MW)
CCGT
and reciprocating engines can burn
ICE
a broader range of fuel composiICE CC
tions (pipeline quality gas and,
Hard Coal
e.g., synthetic natural gas, landfill
Lignite
gas, and biogas). However, recip0
4
6
0
10
20
30
20 40
60
0
2
rocating engines are now availFL/min (%)
FL (%)
Hours
able in sizes of up to 20 MW and
can be organized as banks of enfigure 2. The flexibility characteristics of thermal electricity generation plants.
gines to form a large power plant
Typical plant size (MW) is as follows: OCGT: 50-200; CCGT: 300-500; internal
(>200 MW). Today, in fact, many
combustion engine (ICE)/reciprocating engine: 20-200; ICE combined cycle (CC):
gas turbine manufacturers also
250-450; black (hard) coal: 500-1,000; lignite: 500-1,000. Note that nuclear plants
own reciprocating engine compaare excluded because they perform worse. FL: full load. (Sources: International
nies (Table 1). These plants proEnergy Agency, Energy Technology Perspectives 2014, Paris: OECD/IEA, 2014;
vide cost-effective N-1 reliability
German Institute for Economic Research, Current and Prospective Costs of Electricity
for islanded power systems due
Generation, Berlin, 2013; Verband der Elektrotechnik Elektronik Informationstechnik,
to the scalability of the cascadErneuerbare Energie braucht flexible Kraftwerke-Szenarien 2020, Frankfurt am
ing plants, which require only one
Main, 2012.)
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january/february 2017

Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - January/February 2017