Development of High Efficiency
Gas Turbine Combined Cycle
Power Plant
MASAO ISHIKAWA*1

MASASHI TERAUCHI*1

TOYOAKI KOMORI*1

JUN YASURAOKA*1

The reduction of carbon dioxide (CO2) to prevent global warming has become a serious issue for power plants. Since power plants
account for one third of the total CO2 emissions, improvements in their efficiency will greatly contribute to the reduction of CO2emissions. This paper focuses on the gas turbine combined cycle power plant, and introduces the approaches for the improvement ofits efficiency.

1. Introduction
Methods of CO2 reduction to prevent global warming canbe divided into two types: reduction of CO 2 emissions andrecovery of CO2 .
Over the last one or two years CO 2 recovery has beenstudied for a combined system of hydrogen gas turbine
combined cycle and EOR (enhanced oil recovery), where
petroleum coke is gasified and the gas is shifted by reforming
to CO2 and hydrogen.
It is well-known that power plants are responsible for
one third of the total CO 2 emissions. Improving the heatefficiency of a power plant by introducing a high-efficiency
gas turbine combined plant with an advanced gas turbine
leads directly to the reduction of CO 2 emissions, and istherefore an effective means of CO2 reduction.
This paper reports the gas turbine combined cycle plant toreduce CO2 emissions, and describes its future prospects ofhigh efficiency.

Fig. 1 G-type combined cycle plant
Unit 4-2 at Higashi Niigata Thermal Power Station ofTohoku Electric Power Co., Inc.

Efficiency of the plant (HHV, %)60

2. Transition of the heat efficiency of combined cycle
plant and CO2 reduction
Thermal power plants are broadly divided into two types:
the conventional type with a combination of a boiler andsteam turbine and the combined cycle type which consists ofa gas turbine and a steam turbine that uses high-temperature
steam obtained through heat recovery from the gas turbine
exhaust gas.
Unlike a conventional thermal power plant, a combined
cycle power plant was adopted for power generation in Japanfor the first time in 1984 in Unit No. 3 at Higashi Niigata
Thermal Power Station of Tohoku Electric Power Co., Inc.,
where a D-type gas turbine with an inlet temperature of 1,100°C
was adopted.
With the rise in turbine inlet temperature, a 1,300°C class
F-type gas turbine was developed, followed by a 1,500°C classG-type gas turbine (see Fig. 1). The state-of-the-art G-type
gas turbine combined plant has an efficiency exceeding 59%

5040
3020: Combined cycle power plant: Conventional thermal power plant

100
1940

1950

1960

1970

1980

1990

2000

2010

YearFig. 2 Transition of plant efficiency of conventional type thermal
power plant and combined cycle power plant :Adapted from Improvement of Efficiency of Thermal Power Plant, ‘3.
Gas Turbine,’ Thermal Power and Nuclear Power Plant Vol. 54 No.
10 (2003) p. 1176.

(LHV base) and 53% (HHV base). Figure 2 shows a comparison
between the combined cycle power plant and a conventional
thermal power plant, while Fig. 3 shows the transition ofreductions in CO2 emissions per kWh due to improvement ofefficiency.
Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 45 No. 1 (Mar. 2008)*1 Power Systems Headquarters

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0.8
CO2 emissions (kg/kWh)0.70

Combined plant efficiency (LHV%): Conventional thermal power plant: Combined cycle power plant

0.75
0.65
0.60.55
0.5
0.45
0.4
0.35
0.3
1940

1950

1960

1970 1980
Year

1990

2000

2010

65
Gas turbine
combined cycle60

G-typeF-typeSuper high-temperature
gas turbine(1700˚C)55
D-type50451100 1200 1300 1400 1500 1600 1700
Turbine inlet temperature (˚C)

Fig. 3 Transition of “CO2 emission reduction”
Indicates the CO 2 emissions converted to emissions from natural
gas firing conventional thermal power/combined cycle power plants

Fig. 4 Turbine inlet temperature and combined plant efficiency

The CO2 emissions have consistently been reduced since1950, but because of the slowdown of the improvement inefficiency, the amount of CO 2 reduction in conventional
thermal power plants is not so much compared with thecombined plant.
On the contrary, because of the drastic improvements
made in the efficiency of the combined cycle plant, the CO2
emissions have been greatly reduced and are expected to
be further reduced in the future due to improvement ofefficiency.

temperature) and efficiency.
The efficiency of the combined cycle plant with a 1,700°C classgas turbine with its inlet temperature improved to 1,700°C
compared with the F-type and G-type with inlet temperaturesof 1,500°C has reached the level of 62% - 65% (LHV base), andis expected to stand at a higher level than the efficiency of theconventional combined cycle plant.
The design concept of 1,700°C class gas turbine is shownin Fig. 5.
Mitsubishi Heavy Industries, Ltd. (MHI) has joined thedevelopment program of the 1,700°C class gas turbine, a nationalproject, which requires six component technologies (combustor,cooling technology, heat-resisting materials, heat-shielding
coating, turbine aerodynamics and compressor aerodynamics).
For realization of the 1,700°C class gas turbine with an inlet
temperature far higher than the latest 1,500°C gas turbine,

3. Outline of 1,700°C class high-efficiency gas turbine
As mentioned above, it is necessary to raise the cycle
temperat ure in order to improve the ef f iciency of thecombined cycle plant. Figure 4 shows the relationshipbetween the maximum cycle temperature (gas turbine inlet

TurbineDevelopment of advanced cooling technology,
low thermal conductivity heat-shielding coating,development of super heat-resistant material,high-load and high-performance turbine

Compressor
High pressure ratio,
high-performance compressor

Combustor
Low NOX
combustion system

Fig. 5 Design concept of 1,700°C class gas turbine

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 45 No. 1 (Mar. 2008)

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50.0

10000

CO2 emissions(100 million tons/year)

Power generation using natural gas(TWh)

12000

8000
6000
4000
200002000

2010

45.0

CO2reduction

40.0
F-typeG-type35.0

1700˚C
class

30.0

2030

Year

Fig. 6 Estimated power generation using
Fig. 6 natural gas
Adapted from IEA World Energy Outlook

Fig. 7 Estimated CO 2 emissions due to power generation
Fig. 7 at natural gas firing combined cycle plant
Indicates emission rate per 10,000 TWh.

the basic design of high performance compressor, low NO X
combustor and turbine capable of withstanding the 1,700°C
inlet temperature is under development.

5. Conclusion
Gas turbine combined cycle power plants mainly using
MHI D, F and G-type gas turbines are currently in operationin large numbers, and there are many under construction
or planned both in Japan and abroad. The development andintroduction of this new technology responds to the needfor the effective utilization of energy and countermeasuresagainst global warming, thus contributing greatly to society.
MHI is determined to continue ef for ts to develop newtechnology as a pioneer company in this field.

4. CO2 reduction due to high-efficiency gas turbine
combined cycle plant
The world’s gross power generation amounted to 15,000
T (tera) Wh in 2000, and is estimated to exceed 20,000 TWh
in 2010 and 30,000 TWh in 2030.
It is estimated that the power generation due to naturalgas, the main fuel of power generation equipment, will be
5,000 TWh in 2010 and double to about 10,000 TWh in 2030
(see Fig. 6).
Supposing it is planned that all of the power generation(10,000 T Wh) for 2030 will use natural gas firing highefficiency gas turbine combined cycle G-type or 1,700°C classturbines, the CO2 reduction due to fuel reduction because ofthe efficiency difference from the F type turbine will amountto 200 million tons for G-type turbines and approximately
500 - 700 million tons for 1,700°C class turbines (see Fig. 7).
In view of the present total annual CO 2 emissions ofapproximately 1.3 billion tons in Japan, this figure showsa remarkable progress in CO2 reduction.
Thus, it is considered that the large CO 2 reduction for
high-efficiency gas turbine combined cycle plants is possible
before the implementation of CO 2 recovery and reservoir
systems.

References
1. Iwasaki, Y. et al., Operating Status of Uprating Gas Turbines andFuture Trend of Gas Turbine Development, Mitsubishi Heavy
Industries Technical Review Vol.44 No.4 (2007)
2. Okada, I. et al., Development of 1 70 0°C Class Gas Turbine
Technology, Mitsubishi Juko Giho Vol.44 No.1 (2007)

Masao Ishikawa

Masashi Terauchi

Toyoaki Komori

Jun Yasuraoka

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 45 No. 1 (Mar. 2008)17