Principal Research Results“Energy Chain”, A New Concept in Evaluating Future Energy Conservation andGreenhouse Abatement Alternatives and EffectivenessBackgroundThe energy demand and supply system consists of many kinds of energy subsystems, for example, grid network, fuel (citygas, LPG, kerosene and so on) networks, prospective fuel (hydrogen) networks and demand-side equipments such as heat pump andcogeneration. In recent years, many evaluation methods and factors have been proposed and discussions of energy policy about innovative technology are becoming more multifaceted. In addition, as a result of specialization and segmentation of engineering science,
too much discussion has been centered on particular details of efficiency, rather than on the overall needs of the energy supply and demand system. Integration of these evaluations and discussions is necessary for criteria for judgment. Critical review is always necessary to ensure that prospective technologies are really energy saving and contribute to greenhouse abatement over the whole spectrum
from producing energy to end-use.

Objectives
To introduce a new concept of “Energy Chain” from producing energy through transmission, utilization and end-use, and topropose engineering methodology and evaluation method with examples.

Principal Results
1.Proposing a New Concept of Energy Chain and Evaluation Method
What the energy end-user needs is “energy benefit”. This include all kinds of benefit ＊ 1 that end-users enjoy. The energy
chain (EC) concept is defined as energy paths from source ＊ 2 to energy consumption to final end-use energy benefit (Fig.1 (a)). As
shown in the figure, there are a lot of paths in an EC to meet an energy benefit. Two indices based on time-depending demand are proposed to measure the effectiveness of the process (Fig.1 (b))＊ 3. Energy Chain Joule Index (ECJI) expresses the level of energy conservation and Energy Chain Carbon Index (ECCI) expresses the level of greenhouse abatement (CO2 emissions). A larger value indicates an effective energy chain with respect to energy conservation or greenhouse abatement. EC diagram can represent visually theflow of energy. This diagram also can represent quantities and places of exhaust heat generation and consumption. This is useful tograsp features of ECs.
2.Examples of Evaluation with Energy Chain Method(1) Analysis results that use time-depending demand are presented in Fig. 2. Two ECs are compared; “Grid + Heat Pump” and “PEFCCogeneration + Grid”. As shown in these figures, both ECs have same effectiveness of energy conservation but Grid + Heat Pump
excels in terms of greenhouse abatement.
(2) Equivalent energy conservation conditions with respect to rated demand ＊ 4 can be obtained by making ECJI of both ECs equal(Fig.3), and this is represented in the figure as an energy conservative competitive border (ECCB). In AREA 1 which is shut inthick-dashed curve and ECCB, the cogeneration system is more energy conservation than Grid + Heat Pump. When value of demand rate of heating to electricity (φ) increases, AREA 1 becomes small and finally disappears at a certain value. When ηg andζHP increase, AREA 1 becomes small, too. The cogeneration system presented in (1) exists in AREA 1 as a result of analysis
based on rated demand. The system, however, exists on the ECCB as a result of analysis based on time-depending demand, because the system does not make full use of recovery heat. This result shows it is necessary to use time-depending demand for EC evaluation.

Future Developments
The concept and evaluation method of EC will be made known at home and abroad. Authors will develop software which
involves this method as soon as possible, and will accumulate more examples.
Main Researchers:
Michiyuki Saikawa, Senior Research Scientist, and Katsumi Hashimoto, Research Scientist, Thermal Engineering Sector, Energy
Engineering Research Laboratory
Reference
T.Hamamatsu, M.Saikawa and K.Hashimoto, 2004, “Energy Chain”, A New Concept in Evaluating Future Energy Conservation andGreenhouse Abatement Alternatives and Effectiveness”, Proceedings 19th World Energy Congress, Sydney
K.Hashimoto, M.Saikawa and T.Hamamatsu, 2004, “A Comparative Study of the Distributed Cogeneration System and theCentralized Grid with Heat Pump System Using “Energy Chain” Concept”, Proceedings 14th ICPWS, Kyoto＊1：What the energy end-user needs is “energy benefit” in terms of heating, cooling, lighting and so on, but neither city gas/oil nor electricity.
＊ 2：The primary energy supply into Japan.
＊ 3：Energy Chain Workshop (Aug. 2001 - Mar. 2003, host: CRIEPI, project manager: Prof. Kasagi (Univ. of Tokyo)) consisted of intellectual
mechanical, electrical, energy and civil engineers and government officers. They discussed and agreed that EC indices are important and haveinternational availability and objectivity.
＊4：”Rated demand” (a) is classified into electricity and heat, (b) does not depend on time. And (c) demand ratio of heat to electricity is fixed andequal to ratio of heat recovery to generation efficiency of cogeneration92

6. Fossil Fuel Power Generation - Improving the efficiency of thermal power generation

The Collection of Energy(Primary Energy)

Final Energy
Consumption

Networks

Natural Gas

Clean Fuel Bases

Coal, etc.

Overseas and Dom estic

Nuclear FuelCentralized
Grid PowerTo Industrial
DemandTransport, Reforming, Conversion,
Liquidation, Refining, etc.

Hydropower, Wind,Geothermal, Solar Power,
Biomass and Waste, etc.

Lighting
Installations,Freezers,Electric Tools,Elevators, etc.

Power Net work

Refrigerationand Work,Operation At
Both
Residences &Offices.

Heat Pumps
for HVA C

HV/AV forResidencesand Offices

Heat Pumps
for Hot Water
SupplyDistributed Generationof Ultra High Efficiency

Hot Water
Supply forResidences
and Offices

Distributed
Heat / Power
Co-Generation
Clean Fuel Networks
Absorption
Refrigerator

Oil, etc.
Co-P roduction of High
Value Added Materials

Energy Conservation:
ECJI: Energy Chain Joule Index
End-Use Energy Benefit (MJ)＝
Primary Energy Consumption (MJ)

Co-Production of High
Value Added Materials

Methanol,Hydrogen,etc.

The End Use
Energy Benefit

Greenhouse Abatement:(ECCI: Energy Chain Carbon Index)
End-Use Energy Benefit (MJ)
＝CO 2 Produced from Primary Energy (kg-C)※ Should be based on “high heat value (HHV)”

Note: The combustion equipment for clean fuel at theultimate energy consumption stage has been excluded.

The energy chain concept is defined as energy paths from source to energy
consumption to final end-use energy benefit in terms of heating, cooling,lighting and other benefits of energy(a) Concept of Entire Energy Chain

Two indices are proposed to measure the effectiveness ofthe process. Energy Chain Joule Index (ECJI) expresses
the level of energy conservation. Energy Chain Carbon
Index (ECCI) expresses the level of greenhouseabatement.

(b) Indices Definition

Fig.1 Concept of Energy Chain and Indices Definition.

Energy demand and supply analysis for Japanese
residence using yearly time-depending demandsis done. There are two kinds of energy supply
system. One is Grid + Heat Pump, other is PEFC
+ Grid. ECJI of both systems is equal, but ECCIof Grid + Heat Pump is larger than that of PEFC
+ Grid.
※Grid power efficiency at demand end is about
0.36 (by the energy saving law in Japan). COP(=heat output / input electricity) of heat pumpwater heater is about 4 (achieved value).
※In evaluation of ECCI, unit of demand is “MJ”,
CO 2 emission factor of electricity equal to0.101kg-C/kWh and that of city gas equal to0.0140kg-C/MJ.

Power Generation Efficiency of Co-Generation, ηcge

Fig.2 Examples of Energy Chain Evaluation(Comparison between grid-power & heat pump and on-site cogeneration)
0.4

The thick-dashed curve representstheoretical maximum ofcogeneration efficiency, which means total efficiency ofcogeneration (ηcg) equals 100%. Therefore, in the top-rightarea of the map (AREA 0), cogeneration is impossiblebecause the total efficiency of cogeneration systems exceed
100%. Below the EECC curve (AREA 2), cogeneration is
disadvantageous to energy conservation. Two fine-dashedcurves represent total efficiency of cogeneration is 80% and60%, respectively. This figure is named “energyconservation map”, x-axis is demand ratio of heat toelectricity (φ) and y-axis is power generation efficiency ofcogeneration (ηcge).

AREA 1(Co-Gen. is energy conservative)

Energy Conservation
Competitive Border(ηg=35%,ζHP=4)

0.3

0.2

AREA 0PEFC-Time DependentDemand0.1(Co-Gen. is impossible)
PEFC-Rated Demandηcg=100%ηcg=80%

ηg: Grid power efficiency at demand end, ζHP: Coefficientof performance (heat pump), ηcge: Generation efficiency ofcogeneration, ηcg: Total efficiency of cogeneration, φ :ηcg=60%

AREA 2 (Co-Gen. is not energy conservative)
0.001234567

Demand Ratio of Heat to Electricity, φ8910

Demand ratio of heat to electricity.

Fig.3 Energy Conservation Map based on Energy Chain Joule Index93