Mitsubishi Heavy Industries Technical Review Vol. 56 No. 3 (September 2019)
1PWPS/Aeroderivative Gas Turbine for Fast Demand
Response in Coming Ancillary Market

M i ts u b i s h i H i ta c h i P o w e r S y s t e m s , L t d .

The introduction of large-scale renewable energy projects such as solar and wind power
generation has become a global trend. However, as is well known, renewable energy is very
unstable, and solar power cannot be generated after sunset. This has already become a major
problem, and in some regions, solar power generation has to be restricted for the stable operationof the electric grid system. To further expand the introduction of renewable energy in the future, itis essential to install thermal power sources to compensate for load fluctuations in the electric gridsystem. This power supply requires fast startup and ramp rate characteristics and high efficiency
with lower CO2 emissions, and the aeroderivative gas turbine (Aero GT), which is most suitable forthese requirements, will be introduced here.
In Japan, the market is expected to shift to full liberalization through the separation of power
generation and transmission, and the capacity and adjusting capacity market as Ancillary market
will be developed based on power system stabilization at the time of renewable energy
introduction. The Aero GT is a promising product for this market and this paper describes thecharacteristics of the Aero GT and examples of its activities in Europe and the U.S.A.

|1. Characteristics of PWPS aeroderivative gas turbine
PW Power Systems, Inc. (PWPS) is a manufacturing and sales company of Aero GT that wasestablished in 1961. PWPS was acquired by Mitsubishi Heavy Industries, Ltd. (MHI) in 2013, andbecame a wholly-owned subsidiary of Mitsubishi Hitachi Power Systems, Ltd. (MHPS) in 2017.
Aircraft engines are required to be compact, lightweight, and have a large amount of thrust(power). Therefore, the Aero GT derived from this engine is smaller, lighter and has a smaller
footprint than heavy-duty gas turbines designed exclusively for power generation. In addition, highload responsiveness is required for aircraft engines because of the need to quickly change a large
amount of output in response to environmental changes during takeoff and landing or during flight.
In addition, it is necessary to cope with the operation of repeating the frequent starts and stops, andhigh reliability of ignition startup is also required. On the other hand, since it is necessary to reducethe influence on the main body’s life against such severe operation, the casing and the rotor have athin structure. The Aero GT, which is based on this technology and structure, has a small impact on
the life consumption of high-temperature parts despite its short starting time.
Air compressors with high load and high pressure ratios are used for aircraft engines toobtain a large amount of thrust efficiently, and this compressor is also used for Aero GT, so that thesimple cycle efficiency of Aero GT is higher than that of a heavy-duty gas turbine.
In terms of maintenance, the entire engine is replaced at the site by modularized periodic
inspection in the same manner as the aircraft engine, so it can be replaced in just a few days, and ahigh availavility of the plant is realized. Figure 1 shows a comparison of the appearance of anaircraft engine and Aero GT.

Mitsubishi Heavy Industries Technical Review Vol. 56 No. 3 (September 2019)
2Figure 1 Aircraft engine and Aero GT|2. Aero GT lineup
The Aero GT of PWPS is characterized by its high efficiency (40% on simple cycle), thinand lightweight construction, rapid start (within 5 minutes), quick load response (50%/min), and noturning operation before start. It has 2 models, the 30 MW class FT8 and the 60 MW class FT4000.
The FT 4000 is the latest model, and the core is based on the PW 4000 turbofan engine,which has a good track record, and the low-pressure compressor (LPC) and the power turbine (PT)are uniquely designed for aeroderivative use. The factory test of the first machine was successfullycompleted at the West Palm Beach factory in the U.S.A. in 2014, and 3 units are already incommercial operation in the U.S.A. and Argentina, smoothly contributing to electric power
demand.
Two unique product solutions specific to PWPS using these engines are introduced below.
Table 1 describes these performance characteristics
Table 1 Performance specifications
GT modelFT8Mobilepac(Mobile type)
1SP60(Fixed)
1SP120(Fixed)
2 (Twinpac)

3. Gross Generator output (kW)30,941

70,836

141,567

4. Gross Thermal efficiency (% LHV)

36.7

41.3

41.4

Water injection

Water injection

Water injection

1. Model2. Number of Engines

5. NOx control

FT4000Remarks: 1013 mbar x 15°C, gas fuel, 60 Hz(1)

Mobilepac
Mobilepac with FT8 is the world’s largest capacity mobile power supply facility of 30
MW. Since the GT and the generator are contained in the same trailer, the coupling alignment
adjustment for each movement is unnecessary. In addition, concrete foundation work may also
be unnecessary depending on the bearing capacity of the soil, and it is possible to complete theinstallation work in the very short period of several days (Figure 2) .

Figure 2

FT8Mobilepac

In terms of technical characteristics, FT8-Mobilepac is a dual fuel combustor which canuse both oil and gas fuel, and features dual-frequency specifications that can be operated in 50
Hz districts and 60 Hz districts using the same Mobilepac. After the Great East Japan
Earthquake in 2011, the problem of the transmission of electricity from 60 Hz districts to 50 Hz
districts surfaced, but this Mobilepac can generate electricity in both frequencies by moving

Mitsubishi Heavy Industries Technical Review Vol. 56 No. 3 (September 2019)3from district to district, so it is an effective solution for future disaster mitigation
countermeasures and national resilience.
(2) Twinpac
The FT 4000, if used with a shaft configuration in which one generator is driven by twoengines, is the world’s largest Aero GT package with a generating capacity of 140 MW.
Although it is compact, it has a large amount of output, so it offers significant advantages interms of the reduction of construction cost and installation area.
In addition, since one of the two engines can be operated separately from the other, thepartial load efficiency can be maintained at a high level (Figure 3), and a combination of twogas turbines and one heat recovery boiler can be used in common, contributing to a reduction inconstruction costs.

Figure 3

140 MW class FT 4000 Twinpac|3. GT solutions for capacity and regulating capacity markets
In Europe and the U.S.A., the energy market (MWh) and the ancillary market (Capacity MWand Regulating CapacityΔMW/Δh Market) are operated to stabilize the frequency and voltage ofthe power system following the separation of power generation and transmission, and Japan isconsidering its introduction. The ancillary market (Figure 4) is closely related to the stabilizationof the electric grid system in response to the expansion of renewable energy. In Europe and theU.S.A, the penetration rate of Aero GT in this market is high because of its rapid start
characteristics. Here are some examples of Aero GT solutions.

Figure 4(1)

Ancillary Market Investment Concept

Spinning reserve and condensing operation
If the output of renewable energy drastically decreases due to a sudden change in theweather, the power supply becomes insufficient and the system frequency fluctuates. To
maintain the system frequency properly, it is necessary to make up for the shortage of supply
power quickly with a backup power supply, etc. Thermal power generation with a shortgeneration time of 1 minute or even 1 second is required. In addition, it is preferable that theoperations before starting and after stopping are simple and there are few auxiliary units.
Because the Aero GT is completely air-cooled, including the generator, it is suitable for running
the spinning reserve (instantaneous output) from the perspective of operation and maintenance,and many systems have been introduced in Europe and the U.S.A. As shown in Figure 5,
PWPS’s Aero GT has a Free Turbine configuration in which the PT (power turbine forMitsubishi Heavy Industries Technical Review Vol. 56 No. 3 (September 2019)
4generator drive) is separated from the GG (Gas Generator). Therefore, when the generator isconnected to the electric power system as a synchronous motor without a clutch, power factor
improvement and phase adjustment operation of voltage adjustment are possible. Taking
advantage of these characteristics, in addition to power generation operation, the Aero GT
offers double benefit with a single unit for not only power generation operation, but also powersystem stabilization by condensing operation at the renewable power generation operation.

Figure 5(2)PWPS/Aero GT shaft configuration

Hybrid system (GT + Battery)In the spinning reserve, there is demand to supply electric power instantaneously by astart command and it is necessary to always perform standby operation of the GT with theminimum load. In the meantime, this is uneconomical because fuel is burned on no-load as
standby fuel, and it is also environmentally undesirable in terms of CO2 emissions. A hybrid
system combining GT and a battery has recently attracted attention as a system capable ofcutting this standby fuel and instantaneously supplying electricity. The basic configuration ofthis system is shown in Figure 6.

Figure 6

Hybrid System (GT + battery)This system is composed of Aero GT and a battery (including power conditioner). Its
control unit factors in weather conditions, which affect the renewable energy output, the market
trends of the electric price and the fuel price and starts and stops the system in consideration ofelectric power grid stabilization and economic factors. Furthermore, since the battery can also
serve as an emergency generator during a blackout, a diesel generator for blackouts isunnecessary.
Table 2 shows a comparison between the hybrid system and the GT/battery stand-alone
system. This system has already been put into practical use in the U.S., and is effective for bothdemand for the further expansion of renewable energy introduction and electric power gridstabilization in Japan. A significant drop in battery prices is expected in the future, and theintroduction of hybrid systems is anticipated to be even faster.

Mitsubishi Heavy Industries Technical Review Vol. 56 No. 3 (September 2019)5

Table 2 Comparison of Hybrid and Other Systems
GT only

ESS only

GT + ESS

1. CAPEX

SystemBase

Expensive

Somewhat expensive

2. OPEXBase
Yes (at All Combined
Use Time)
None
Yes (at synchronizedoperation)
Base

Cheap

Cheap

None

None

Yes

Yes

Satisfactory

SatisfactoryFastFastNo

Yes (CHARGE)

Yes (CHARGE)
Not Required

3. Standby fuel
4. CO2 Credit
5. Instantaneous Power Generation
6. Response Speed
7. Measures for Surplus Power fromRenewable Energy Sources
8. Blackout Emergency D/GRequired

Not Required

9. Condensing Operation

Satisfactory

No

Satisfactory

10. Long-term Continuous Operation

Satisfactory

Unsuitability

Satisfactory|4. Future developments
The Aero GT, which has excellent quick start characteristics and fast load change
characteristics, is a power generation system suitable for the ancillary market. As a result, it ispossible to contribute to environmental load reduction and power grid stabilization by expanding
the introduction of renewable energy.
To respond to the diversifying needs of the electric power market, we will make further
efforts to improve the startup performance and operability.