Distributed Generation
Installed Each Family in 21
Century
YOICHIRO OKAZAKINOBUYASU MATSUDAIRAAKIRA HISHIKAWA
KAORU YAMANE

solar power generation, and the new energy source fuelcell, etc. This paper, however, describes particularly the
product equivalent to the low-capacity distributed generation with power 3.8 MW or under.

1. Introduction
Mitsubishi Heavy Industries, Ltd. (MHI) has been
manufacturing various machines related to power industry in order to meet the needs of customers. “Distributed
Generation” is a general term for small-scale powersource against large-scale centralized power source that
supplies electricity using nuclear, thermal and hydroelectric power plants and the network of powertransmissions lines. Easy to install wherever needed asa small-capacity power source, the distributed generation generates only the required amount of power andhas high energy efficiency. As a countermeasure against
global warming and because of deregulation in energy
industry, it has a promising future and is expected tohave its market widened.
MHI deals with the distributed generation using highpower diesel engine, gas engine, and gas turbine, thereproducible energy such as wind power generation and

2. PastFig. 1 shows the horse-power generated by 4 kW - 3.8
MW class MHI engines.
MHI has been producing industrial engines since prewar time for mounting and using on construction
machines. However, with the Fire Service Act revised in1974 and obligation enforced for buildings to install emergency power supply as a disaster preventing facility, thedistributed generation became popular and came to be
frequently used as the engines for package generation set.
Further, with the changes brought in energy situation in 1975-1984, there was an increasing market
demand for application to continuous power source andcogeneration. Consequently, MHI developed new series( X 10 3 )Economiccrisis inSouth East
Asia

8 000

7 000

High appreciationof yenGenerated horse-power (PS)

6 000

80 /$

5 000

4 000
Shock due
to highappreciationof yen

3 000

2 000

Secondoil shock(crisis)1 000

01965 1967 1969 1971 1973 1975 1977 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001
Collapse of so-called bubble
Fiscal year
age, demand on the decline
Fig. 1 Generated horse-power of engines of 3.8MW or under
Indicates the transition of generated horse-power of engines ranging in capacity from 4 kW to 3.8 MW since 1965.

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol.40 No.1 (Feb. 2003)

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Fig. 3 shows the comparison of engines for 1000 kWclass generators, indicating that the new-type engines
S12H launched in 1997 is smaller in size and lighter inweight than the conventional type S12N put on sale atabout 1975.
Found close to our living, the distributed generation
has eventually come to the limelight in recent years withincreasing demand for low pollution and energy-saving.
In order to meet with these demands, MHI has developed and put on sale diesel engines conforming toemission regulations and low fuel consumption requirements or gas engines using clean city gas as the fuel.
The emission regulations schedule of U.S. Environmental Protection Agency (abbreviated as EPA) for
off-load diesel engine is given in Fig. 4 as an example,of engines with higher performance and durability thanthe conventional ones, and launched them in the domestic market of distributed generation. Because of the brisk
domestic market and increased export during the periodof 1985-1994, the generated horse-power has so far enjoyed a rapid growth.
However, the engine generator for camping use did not
spread much as the distributed generation for home use.

3. Present
3.1 Diesel engine
The diffusion of cogeneration and the deregulation ofenergy have led to the distributed generation getting
spotlighted and increased.
Fig. 2 shows a line-up of engines used for small-power
distributed generation.

R

20% reduction
Conventional type S12N
in weight
4 700 kg
New-type S12H
3 800 kg

: MHI Industrial Machinery Division: MHI General Machinery &Special Vehicle Headquarters: Mitsubishi Motors Corporation (MMC)
Small-size
SS engineSK

Gasoline engine
L
SL
SQ

MITSUBISHI

D1, D2 [MMC]
SB
SA
SH

Large-size engine
SR, SR-V
SU

5 10

50

100

300

500

700

1 000

5 000

10 000

Output (kW)Fig. 3 Comparison of old and new engines
Conventional type S12N for 1 000 kW-class generator
is compared with new type S12H in terms of size andweight. The weight is reduced by 20% in the new type.

Fig. 2 Line-up of small-power distributed generation engines
Indicates a series of generator engines, covering a wide range from 1 kW
to 3.8 MW.

Year

37 to 75 kW

First-stage control

37 to 130 kW

First-stage control

7.5
5
4.7

37 to 75 kW

Second-stage control

109.2

First-stage control

Second-stage control

Third-stage control

Futurecontrol draft

6.6
5

75 to 130 kW

Third-stage
control
Third-stage
control

Second-stage control

NOx + HC (g/kWh)10
9.2
NOx + HC (g/kWh)1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009First-stage control

Second-stage control

Third-stage control
Futurecontrol draft

00(0.13)(0.13)
0
0.1
0.2
0.3
0.4
0.5
0.6
0
0.1
0.2
0.3
0.4
0.5
0.6
Particulate Matter (g / kW.h)Particulate Matter (g/kW.h)Fig. 4 U.S. EPA off-load engine emission regulations schedule
The example is for 37 kW to 130 kW, with the control getting stricter in second and third stages than in first stage.

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol.40 No.1 (Feb. 2003)

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Fig. 5 Diesel engine corresponding to secondary control of exhaustgas (emission)
Indicates the appearance of 2 MW-class S16R generator set corresponding to North American EPA exhaust gas regulatory requirements (control)by adopting large-size air-cooled charge air cooler and high-pressurefuel-injection pump.

Fig. 6 Appearance of miller-cycle gas engine
Indicates the installed GS16R obtained by applying Miller-cycle
gas engine for cogeneration to the S16R engine in Fig. 5.

indicating that the schedules and control values bothin Japan and abroad are almost same. MHI is currently under consideration of putting new typeengines conforming to the second-stage regulatory(control) requirements on sale and developing newengines to meet the more severe third-stage regulatory requirements. In order to clear the second-stage
regulatory requirements, the intake temperature
was reduced to diminish the NOx emission and thefuel injection pressure was increased to reduce theparticulate matter considered harmful to environm e n t a n d h u m a n b o d y, l e a d i n g t o t h ecommercialization of the engine with the appearance
shown in Fig. 5 and conforming to the gas emission
regulatory requirements.

3.2 Gas engine
As for the gas engine, MHI launched the Miller cycle
gas engine with the highest efficiency in this class ofengine in the world in the market in 2000, and has
gained high reputation. The appearance of the engine
6. As is shown in Fig. 77, Miller cycleis shown in Fig. 6
refers to a system where the closing time of intake
valve is changed to make the compression stroke
shorter than that of a normal engine, causing the expansion ratio to become higher than the compression
ratio. The work indicated by the section with dot meshing in the diagram gets increased, causing the thermal
efficiency to get improved. MHI has successfully improved the efficiency by 5% as compared with theconventional engine by adopting this system in theHigh efficiency
Engine flywheel output efficiency (%)

Conceptional diagram of Miller cycle
3

Pressure

Combustion
Heat
input
2

Expansion

Increased work due tohigh expansion ratio
ExhaustCompression

4

5

IntakeExhaustCompression stroke
Expansion stroke

42%

40

37%
35

6

1

30
Extendedpart

VolumeBase engine

Final objective (target)

Fig. 7 High-efficiency through miller-cycle
With the expansion ratio higher than that of the conventional engine, the work done got increased with the efficiency improved by 5% against the base engine.

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol.40 No.1 (Feb. 2003)

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Outline of equipment

Annual CO2 emission(ton)Reduction of CO2

1. Main specification of gas engine
Engine type

GS 16 R

Number of cylindersBore x Stroke
Output845 kWe/1 500 rpm

Power generation efficiency

40%

NOx

1 20 ppm (O2 0%)

150
Reduction rate
(22.2%)

700
600
500
400
676

300

526

200
100
0

Before introduction

Cost merit

After introduction

Index indication with"commercial power supply + boiler"
cost as 100
Independent power
generation

Commercial
power supply+ boiler
100
Boiler fuel charge
14(using hot water and steam)31
Basic (contract) charge

2. Operating record(1) Operation started: July 1999
(2) Total operating time: 7 600 hr

55Electric charge

Reduction
ratio of 40%

60

Fuel charge
and maintenance cost

Fig. 8 Example of gas cogeneration engine installation
Shows an example of independent power plant in Sagamihara Machinery
Works of General Machinery & Special Vehicle Headquarters, indicating a drastic improvement in CO2 emission and operating cost ascompared with before the adoption of the plant.

lean-burn engine. Fig. 8 shows an example of the gas
cogeneration used for independent power generation in
MHI Sagamihara Machinery Works, with the CO 2 reduced by approximately 20% as compared with prior to
its adoption and the operating cost by approximately 40%
as compared when the works had used commercial power
supply and boiler.
These engines are operating at the customers’ places
and, like continuous generation system, are controlled
through a 24-hour remote monitoring system to minimize the failure chance caused by trouble.

the equipment is expected to get superannuated needing renewal, it is considered to be partially replacedwith the distributed generation and the small andmedium size centralized generation with excellent
efficiency.
Fig. 9 shows the possibility of the distributed generation getting widely spread in the future. The
distributed generation adopting micro-gas turbine used
in a convenience store has become a topic of conversation in newspaper, etc. in recent years, and is expectedto spread in future for small-scale facility such as
houses with less demand of heat and electricity. It isalso expected that the power source for distributed generation will become optimum for each pattern of power
demand.
Further, the distributed generation is indispensable
to the plant facilities where installation of transmission
line (cable) is not easy, and eventually, its demand (need)is considered to be increasing.
MHI is mustering efforts in the development of future-generation products, such as high-efficiency gas
engines and high-efficiency continuous diesel engines for
distributed generation, and such as micro-gas turbinesand fuel cells for small stores and home use.
4.2 High-efficiency gas engine
As for the high-efficiency gas engine, the development of engine employing the cylinder-wise,
independent optimum electronic control adopted in
MACH series for high-power distributed generation

4. Future
4.1 Future of distributed generation
The demand for electric power is estimated to increase in Japan until the middle of 21st century.
However, the centralized power generation is expected
to face a drag on the new installation of nuclear power
plant, making the construction of large-scale plants
more and more difficult in the future. This is likely toincrease the need of distributed generation all the
more.
Further, because of the augmentation of equipment
to match with the maximum power, the centralized
generation is incapable of precise correspondence (tosituation) such as load leveling, etc., so that the system has excessive equipment (facility), releasing
about 60% of the input primary energy as waste heat.
As a result, towards the middle of 21st century, when

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol.40 No.1 (Feb. 2003)

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Power demand

Large
10 MW or more

5 to 10 MW

1 to 5 MW

Small

500 to 1 000 kW 100 to 500 kW

10 to 100 kW

Field with smaller
demand for heat

School (Primary,to senior-high)Junior college
and university

Data center

GE,DE

GE,MGT

Combined residential complex

GE..

Generalsupermarket

GE,DE

DE

Large-size
complexshopping center

General hospital

GE,DE

GE,DE

Plants formaterial fields. iron making. Petroleum. Paper and pulp
GT

Field with larger
demand for heat

Fast foodshop

insurance facility

GE

GE,
DE

Warm bathfacility

Business
hotel and inn

GE,DEIndustrial Field

Gas station

Sport facility
Hotel

MGE

DE

Large-size plants except
the plants for materials. Large-scale food processing plant. Automobile plant. Electronic parts and products plant

Small and medium scale plants. General food processing plant. Plastic products. Electricity

GT,GE

GT,GE,DEYear 1980

1995

2010

2000

Spread expanded
field in recent years

Pre-spread field

House

Fuel cell(Solar light)

Fuel cell
BeautyparlorFamily restaurant
Fuel cell
MGT,MGE
Small and medi- Noodles
um size hospital shops (Ramen,
Soba and Udon)
DE,MGT
MGE
Elderly people's

Tenantbuilding

Large-size generalsupermarket

1 kW or less

CVS

(Solar light) Fuel cellGE

Welfare field
Business use
Home use

Spread time

1 to 10 kW

Status quo spreadand development
field

Field expected tospread in the future

Fig. 9 Prospect of expansion in spread of distributed generation in future It is expected that the distributed generation with conveniently
operable power source will spread in future for small-scale facility such as houses with less demand of heat and electricity.

Pre-combustion
chamber gas
Ignition plug

112.5

Torch jetOptimized specifications
for pre-combustion andmain chamber shapes
and discharge port

(Conventional engine)
Pilot oil
Injection valve
Lean mixture

Main
mixtureTorch jetPower generation efficiency index(with the present value as 100)Main
mixtureStoichiometricmixtureElectronic control of gas
volume in main chamber
and pre-combustion
chamber per cylinder

Optimization of Intake
valve closing time
Common rail system

Development
objective
Present

100

87.5

Lean-burnMiller-cycle
GE

Lean-burn GE

75.0

62.5
100

200

500

1 000

2 000

5 000

10 000

Output (kW)(New engine)
Slight pilot fuelFig. 11 Development objective of high-efficiency gas engine
Improved power generation efficiency and substantial series are
obtained by partially applying the development factors of Miller-cycle
and MACH series.

High-pressure
pump(with machine)

4.3 High-efficiency diesel engine
Development of new series of high-efficiency diesel
engine for continuous use conforming to the much stricter
regulatory requirements for exhaust gas expected in the
future is under way. In order to achieve simultaneously
both the correspondence to exhaust gas regulatory requirements and the improvement in thermal efficiency,
the engine is designed to have high stiffness (rigidity) towithstand the increasingly high maximum pressure inside the cylinder in addition to the adoption ofhigh-pressure injection of fuel and electronic control, with

Common rail system
Fig. 10 Development of high-efficiency gas engine
Indicates the concept of development of MACH series, with the efficiencyof 42% achieved by adopting the elements in the figure.

as shown Fig . 10
10, the lean-burn system of pilot ignition to control NOx emission and making partial
use of the Miller cycle development factor is underway. The development objective (target) is given in
Fig. 1
1.
11

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol.40 No.1 (Feb. 2003)

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Thermal efficiency index(the present indication as 100)120

the target values shown in Fig. 12 and Fig. 13
13. In orderto achieve the final target, development of unique MHI
after-treatment device and the conventional technology
for meeting the exhaust gas regulatory requirements
such as water injection inside the cylinder as well as thecorrespondence to the engine performance are to be effectively used.
4.4 New distributed generation
Fig. 14 shows the micro-gas turbine generator. Though
there is no detailed description in the figure, the generator is put to commercialization with the following 3“E’s” as the sales points.
(1) Efficiency: Small-size generator with efficiency 30%
or above(2) Environment friendly: Urban-type generator with low
NOx emission and low noise(3) Easy to operate: Generator capable of starting, loading, and stopping by means of a single button
Fig. 15 shows the polymer electrolyte fuel cell. The
know-how of the research carried out jointly with
Mitsubishi Motors Corporation is to be applied to thedevelopment of the fuel cell for distributed generation.
Development of 1 kW-class distributed generation forhome use is also under way.
The expansion of spread of the distributed generation depends largely on external environmental
factors (such as power rates, fuel cost, and environmental control). MHI is developing gas turbine andfuel cell in addition to diesel and gas engines to correspond to whatever change might occur in theenvironment.

Step 1

Step 2110

MHI
status100

High-speed Current engine
super-charged
High-speed
non-supercharged

90 Target levelof worldwide
research
80

25
50
75
100
125
NOx concentration index (the present indication as 100)
Fig. 12 Development objective (1) of high-efficiency diesel engine
The development objective is expressed by the relationship between NOx
and thermal efficiency, with the thermal efficiency improved at the present
level of NOx before reducing NOx emission drastically in the next step.

Emisson regulations
limit for 2006

Fuel consumption index(the present indication as 100)

105

100

Current engin. High-pressure injection. Variable injection timing. Control of injection rate
. EGR/after-treatment

95

90
New engine
85
4

6

8

Exhaust gas level NOx + HC (g/ kW. h)
Fig. 13 Development objective (2) of high-efficiency diesel engine
Low emission of exhaust gas and drastic reduction in fuel consumption
are set as the development objective (target) by applying the development factors (elements) in the figure.

[Specifications]80

Rotational frequency (rpm)65 000Power generation efficiency (%)

30

NOx (ppm)

25 or more

Overhaul time (h)20 000Micro-gas turbine (MGT)High-speed generator

45

Gas engine: MHI MGT
: MGT
: Gas engine: Industrial gas turbine

40
Power generation efficiency

Micro-gas turbine generation set(%)

Output (kW)MHI MGT
35
30
25
MGT
20
15
10

Industrial gas turbine
100

1 000

10 000

Output (kW)Output and efficiency of MGT and gas engine

Fig. 14 Micro-gas turbine generator With the output 80 kW, the power generation efficiencyof 30% has been achieved, so that the generator is placed at the top level in the world.

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol.40 No.1 (Feb. 2003)

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Power(Electric power)

Hydrogen
Air
Coolant

ExhaustFuel cell stack
Hot-water supplier

Mountedunder
the floor
Fuel cell car(Joint development
by MMC and MHI)

Fuel cell power pack
1 kW PEFC Unit
Stationary fuel cellFig. 15 Appearance of polymer electrolyte fuel cell
Describes the outline of the fuel cell and thefuel cell under development, with the photograph at the bottom right showing 1 kW fuel cell for home use.

5. Conclusion
With the diffusion of distributed generation to theextent that one unit is used in each family, each family
will start to own a heat accumulating system, bringing
a drastic change in the pattern of energy utilization. Thenthe present power system from upstream to downstream
will not work, calling for the optimization of energy operation of the whole community. This is likely to resultin the revolution of energy business, giving rise to a richlife with less pollution. MHI is determined to continue
making efforts to develop and spread distributed generation meeting individual requirements in order torealize such world.

GENERAL MACHINERY & SPECIAL VEHICLE HEADQUARTERS
M a n a g i n g D i r e c t o r, G e n e ra l
Manager, General Machinery &Special Vehicle Headquarters
Yoichiro Okazaki

References(1) Kurihara et al., Electric Power System Technologies for a
New Era, CRIEPI Review Vol.39 (2000) p.39
(2) Oda et al., Distributed Generation of Mitsubishi Heavy Industries, Mitsubishi Juko Giho Vol.39 No.3 (2002) pp.152-159(3) Website of Fujikeizai Co., Ltd.
http://www.fuji-keizai.co.jp

Nobuyasu
Matsudaira

Akira Hishikawa

Kaoru Yamane

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol.40 No.1 (Feb. 2003)

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