Additional information on calculating the conservative emission factor for VietNam
It is concluded that net emission reductions are achieved by applying the following emission factors
in Viet Nam:

·An emission factor of 0.333 tCO2/MWh, which is the emission factor of the most efficientnatural gas-fired power plant in Viet Nam, is applied in case the PV system in a proposed
project activity is connected to the national grid including through grid which is notconnected to a captive power generator.

·An emission factor of 0.333 tCO2/MWh, which is the emission factor of the most efficientnatural gas-fired power plant in Viet Nam, is applied in case the PV system in a proposed
project activity is connected to internal grid which is connected to both the national grid anda captive power generator.

·An emission factor of 0.533 tCO2/MWh, which is the emission factor of the most efficientdiesel power generator in the world, is applied in case the PV system in a proposed project
activity is connected to an internal grid which is not connected to the national grid.

1. Current status of the electric power source mix in Viet Nam
The national grid system of Viet Nam covers all areas in Viet Nam as shown in Figure 1.

Hanoi

Da Nang

Ho Chi MinhFigure 1. Map of Viet Nam electricity system1

(Source: EVN (2015) Viet Nam Electricity Annual Report 2015)

Figure 2 shows the amount of electricity generation supplied to the national grid by each fuel typefrom 2011 to 2013. The amount of electricity from hydro power plants, biomass power plants andimported electricity that is regarded as low cost/must run (LCMR) was 49 TWh (44%) in 2011-2013
average electricity generation. When the share of the LCMR is less than 50% of the total grid
generation, the operation of LCMR resources would not be affected by a newly installed power plant
including a PV project1. Therefore, only electricity from gas-fired, coal-fired, and oil-fired power
plants is taken into account for calculating the official grid emission factor in Viet Nam. Appling theassumptions above, the 2013’s operating margin and build margin that were published by the VietNam government as 0.681 and 0.451, respectively. Accordingly, the government of Viet Nam
published the combined margin of the grid emission factor as 0.5657 tCO2/MWh.

Electricity generation by fuel140
12040%

TWh

10080

1860

4150%
45%
40%
35%
30%
25%
20%
15%
10%
5%
0%

45%

46%
182441

4249

51

40
203502011
Hydro

Gas

Coal

2012
import diesel oil

Share of electricity generation by fossilfueled power plant during 2011-2013 innational grid

Coal
32%
Gas
67%

2013

Oil
1%

biomass Share of LCMR

Figure 2. Electricity generation of Viet Nam gird by fuel typeIn this methodology, natural gas is identified as a primary electric power source for electricity
generation and used for the conservative calculation of emission factor since it has the largest shareamong the fossil fuels used in Viet Nam in the recent three years among its electric power sourcemix.

2. Heat efficiency and the conservative emission factor of natural gas-fired power plants
For calculating the CO2 emission factor of the electricity generated from natural gas as identified in
Section 1 above, the best heat efficiency (59%) of gas-fired power plants which currently operational
in Viet Nam is applied. The relatively new power plants in Viet Nam identified in a web search arelisted in Table 1. Accordingly, Phu My 3 combined-cycle power plant operated by Phu My 3 BOT
1

CDM EB (2015) Tool to calculate the emission factor for an electricity system
2Power Company Limited is identified as the most efficient power plant. The plant is manufactured
by Siemens and has an efficiency of 58.7% (Lower Heating Value: LHV).

Table 1. Efficiency of natural gas-fired power plants in Viet NamManufacturer
ProductCapacity
Phu My 3 combined-cycle
power plant2
Phu My 2.1 and Phu My 4

SGT5-4000F andSST5-5000
GT13E2740 MW in total
160 MW +450MW

gas-fired power plants3

Plant efficiency(LHV)
58.7 %
53.8 %The CO2 emission factor of power generation by natural gas-fired power plants is calculated fromthe plant efficiency using the following equation:
CO2 emission factor of power generation [t-CO2/MWh]= CO2 emission factor of natural gas [kgCO2/TJ] *3.6*10ି଺ / (Heat efficiency (LHV) [%]/100)
Applying the CO2 emission factor for natural gas combustion, which is 54,300 kgCO2/TJ derived
from “IPCC guideline 2006, Chapter 2, stationary combustion” together with the Plant efficiency(LHV) of 58.7%, the emission factor of power generation by the most efficient natural gas-fired
power plant is calculated to be 0.333 t-CO2/MWh.
The value is lower than 0.5657 tCO2/MWh (combined margin, 2013) which is the emission factor of
the Viet Nam grid published by the government of Viet Nam. Therefore, it is concluded that netemission reductions will be ensured by applying the emission factor of power generation by the mostefficient natural gas-fired power plant for grid electricity displaced by a solar PV system,.

3. Calculation of the emission factor of a diesel generator

To determine the emission factor of a diesel generator in a conservative and simple manner, themost efficient heat efficiency is applied.
The CO2 emission factor of diesel power generation is calculated from the heat efficiency using
the following equation:
CO2 emission factor of power generation [t-CO2/MWh]2

http://www.siemens.com/press/pool/de/pressemitteilungen/2013/energy/energy-service/ESE201301
016e.pdf
3
http://www.alstom.com/press-centre/2011/3/alstom-renews-service-agreement-for-phu-my-gas-fired-power-plant-in-vietnam/3

= CO2 emission factor of fuel source [kgCO2/TJ] *3.6*10ି଺/ (Heat efficiency (LHV) [%]/100)
Applying the default value of the CO2 emission factor of diesel combustion which is 72,600
kgCO2/TJ derived from “IPCC guideline 2006, Chapter 2, stationary combustion”, together withthe heat efficiency of 49%, the efficiency level which has not been achieved yet by the world’s
leading diesel generator, the CO2 emission factor for diesel generator is calculated to be 0.533
tCO2/MWh.

4