JCM Proposed Methodology
Displacement of Grid and Captive Genset Electricity by a Small-scale Solar PV System
Additional Information
1. Grid emission factor
It is concluded to apply the emission factor of 0.533 t-CO2/MWh for the displacement of gridelectricity which uses diesel fuel as a power source by a solar PV system in Palau to achieve net
emission reductions.
1.1. Backgrounds
Although an emission factor of grid electricity is commonly used to calculate emission
reductions achieved by implementation of renewable energy projects to displace grid electricity,
it is not officially published in Palau.
1.2. Findings and rationales
1.2.1. Estimation for the existing power stations in Palau
The Palau Public Utilities Corporation (PPUC), a public corporation established as the soleenergy and water provider for the Republic of Palau, has two power stations, the Malakal Power
Plant located in the commercial center and the EPSECO Power Plant located in Aimeliik.
The followings have been found from the information published by the International Renewable
Energy Agency (IRENA), Secretariat of the Pacific Community (SPC) and PPUC.
Engines using only diesel fuel as a power source are installed in both power stations.

Based on the information by IRENA and SPC, power generation efficiency and the CO2
emission factor of existing power stations in Palau is estimated to be those shown in Table
1 using constants shown in Table 2.

Table 1 Power generation efficiency and CO2 emission factor
IRENA (in 2011)
SPC （in2009）
Malakal Power EPSECO Power
Palau total
StationStation
kWh
43,375,400
45,375,400
83,000,000

Electricity
Diesel fuelUS gal2,650,504

3,640,389-

Efficiency

kWh/gal

14.2

12.5

-

Diesel fuelLitre

10,033,249

13,780,371

23,808,000

Efficiency

kWh/litre

4.20

3.30

3.49

Power generation efficiency of existing power station%

41%

33%

34%

CO2 emission factor ton-CO2/MWh0.631

0.804

0.761

1

Reference: The International Renewable Energy Agency (IRENA), Renewable energy
opportunities and challenges in the Pacific Islands region “Palau”, August 2013; SPC, Palau
Country Energy Security Indicator Profile 2009
Table 2 Constants for calculation of CO2 emission factor
values43 GJ/t IPCC 20061 Volume 2 Energy

Net calorific value of diesel oilDefault emission factors of diesel oilConversion factor of diesel oil

sources72.6 kg-CO2/GJ IPCC 2006 Volume 2 Energy
0.85 kg/litre Petroleum Association of Japan2

1.2.2. Power generation efficiency using diesel fuelCurrently, grid electricity is produced solely through diesel generators at two power plants inPalau. Furthermore, considering the following facts, it can be concluded that diesel generation
still tends to be the best available option3 for grid electricity generation in the future in Palau.
Diesel generator is one of the most energy efficient amongst generators using fossil fuelas a power source

Lack of infrastructure for the supply of other fossil fuels such as gas pipeline

Existing diesel engines for the grid electricity are expected to be used, but they may be replacedin near future upon reaching the end of its lifetime. Also, new capacity may soon be required tomeet increasing electricity demand. The choice of technology for such additional / replacement
capacity is likely to be diesel engines due to their proven track record, albeit a highly efficientone.
In a grid where introduction of a single diesel engine may substantially alter the grid emission
factor, it is assumed that the project displaces new high-efficiency diesel generators to ensure
net emission reductions.
The following information regarding power generation efficiency of new high-efficient diesel
generators has been acquired from published information.
“There are two primary types of piston engine for power generation: the diesel engine and thespark-ignition gas engine. Of these the diesel engine is the most efficient, reaching close to 50%
energy conversion efficiency.”41“IPCC 2006” refers to “2006 IPCC Guidelines for National Greenhouse Gas Inventories”
http://www.paj.gr.jp/statis/kansan/index.html (Japanese language only)
3
The Secretariat of the Pacific Community, Towards an energy secure Pacific, 2011
4
“POWER GENERATIN TECHNOLOGIES, 2nd Edition”, 2014, Paul Breeze

22

“In general, diesel engines have efficiencies that range from 30 to 45%.”5“Power generation efficiency of diesel engines range from 30% to 48%”6“In addition to the SU3 and MARK-30B engines (diesel engines), with output ranges of 2.0 to4.0 MW and 5.2 to 8.1 MW, respectively, an in-line 2.7-MW six-cylinder engine has recentlybeen developed; both its output and thermal efficiency are better than in conventional engines.
The SU3 and MARK-30B engines have attained generation efficiencies of 44.1% and 46.8%,
respectively, which are better than any other diesel engine in the world in this class.”7

It can be said that diesel engines are the most efficient diesel generators, power generation
efficiency of diesel engines has not improved dramatically during recent years, and the world’s
leading power generation efficiency of diesel engines is close to but has not achieved 49%.
Therefore, setting power generation efficiency of new high-efficient diesel generators at 49% isconservative.
A CO2 emission factor can be estimated from power generation efficiency using the following
equation.
CO2 emission factor of the grid electricity [t-CO2/MWh]= (CO2 emission factor of diesel oil [kg-CO2/GJ]/1000*3.6) / (power generation efficiency(lower heating value basis) [%]/100)
Applying the default value of the CO2 emission factor of diesel oil (72.6 kg-CO2/GJ)8 and theconservative value of power generation efficiency of new high-efficient diesel generators, thegrid emission factor of 0.533 t-CO2/MWh is derived. This value (0.533 t-CO2/MWh) is lower
than all values obtained from the published information shown in section1.2.1., which alsoensures that the power generation efficiency of new high-efficient diesel generators set above isconservative.
5Handbook of Energy Efficiency and Renewable Energy”, 2007, Edited by D. Yogi Goswami“Cogeneration Plan and Design Manual, 6th edition”, 2008, The Japan Institute of Energy
7“Approach on High Efficiency Diesel and Gas Engine”, 2008, Mitsubishi Heavy Industries
Technical Review Vol. 45 No. 182006 IPCC Guidelines for National Greenhouse Gas Inventories
63

Table 3 Power generation efficiency and CO2 emission factor of diesel engine
Power generation efficiency of diesel engine%
CO2 emission factor ton-CO2/MWh

49%
0.533

2. Emission factor of captive electricity
The emission factor of 0.8 t-CO2/MWh, stated in the small-scale CDM methodology AMS-I.F.
“Renewable electricity generation for captive use and mini-grid”, is commonly used as theemission factor for captive diesel generators. However, as stated in section 1.2.2, the installationof new high-efficiency diesel generators to the grid is possible, which may cause captivegenerators to be replaced by grid electricity. Therefore, the emission factor of 0.533 t-CO2/MWhis applied to achieve net emission reductions.

43. Measurement of power generation by solar PV system
Electrical current of the generated electricity by the solar modules is DC, and will be changed toAC by the inverters. The electrical current output (AC) of the inverters is measured using theelectricity meter. The inverters are powered by the generated electricity (DC) from the solarmodules. Therefore, the measured value of the electricity meter is equal to the sum of amount ofelectricity supplied to the grid electricity and the amount of electricity supplied to internal
power grid. The measured value will be recorded either by manually or by using a data logger.
4. Electricity consumption by monitoring equipment
The electricity consumed by a typical monitoring system ranges from 1 W for a meter to 12 W
for a communication and data logger system (see below), and this system will be powered bygrid electricity of internal power grid. The electricity consumption is negligible compared to thepower generated by the solar PV system.
Item

Power demand

SourceMonitoring

Type 4W

SMA SUNNY WEBBOX catalog

equipment

Maximum 12WElectricity

Up to 5VA

Osaki Electric A3C-S27VR specification document

meter5