Economy & Energy

No 23 December 2000 -

January 2001

   ISSN 1518-2932

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e&e No 23

Progress in the Energy Matrix and in the Emissions of Gases Causing the Greenhouse Effect

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Reference Economic Scenario

Preliminary Evaluation for the 2000-2020 period

Demand in Equivalent Energy

Electric Energy Demand

2000 – 2020 Thermoelectric Generation


Participation of Fuels used in Generation  

Necessary Thermal Generation Capacity

Emissions in Thermal Power Plants

Conclusions and Sensitivity Evaluation

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Emissions of Gases Causing the Greenhouse Effect by Thermoelectric Power Plant in the 2000 -2020 Period

1. Introduction

Our objective in this work is to develop a methodology for evaluating the emission of the public thermoelectic power plants in different scenarios of economic development and the use of this form of generation considering the different usable fuels. For this purpose we will follow the following path:

  • 1. Obtain the production values associated with a Reference Economic Scenario; 

  • 2. Study the evolution of the equivalent energy/GNP ratio in Brazil, study this ratio in other countries in recent time and its projection in order to determine the demand growth in equivalent energy associated with the GNP;  

  • 3. Study the evolution of electric energy participation in consumption in equivalent energy in Brazil, study this relationship in other countries in recent time and evaluation of electric energy consumption 

  • 4. Evaluation of loses, imports and the participation of self producers aiming at obtaining the energy generation demand concerning public power plants (and those of self producers); 

  • 5. Evaluation of the participation of public power plants in electricity generation;  

  • 6. Projection of thermal power plants participation in the total electric energy generation and the participation of different fuels in this generation;  

  • 7. Study concerning generation efficiency and its projection for the different fuels and consumption of these fuels in the corresponding electricity generation;.  

  • 8. Projection of thermal power plants emissions using fuel demand and information previously obtained for the 1990-1997 period; 

  • 9. Evaluation of the global capacity factor for different power plant types;  

  • 10. Evaluation of the necessity of increasing the Installed Capacity.  

Note: Steps 9 and 10 are necessary, in a strict sense, for emission calculations and were carried out to estimate the necessary generation capacity and compare it with the planned one. The preliminary results can be found at the end of the present work.

2. Emission of Greenhouse Effect Gases from Thermal Power Plants

2.1. Methodology for Evaluating Emissions Causing the Greenhouse Effect

Emissions of the resulting CO2 depends fundamentally on fuel consumption and on some particularities concerning its use. In the long term most of the emitted carbon compounds degrade into CO2. In the particular case of mineral coal with high ash content, as in the Brazilian case, quantitative studies about carbon retention in ashes as well as retention of other compounds such as sulfur have not yet been carried out.

In the present evaluation of long-term impact we have used for coal and for other fuels the parametric data utilized previously in a study carried out for the MCT and PNUD for the 1990-1997 period.

Fuel consumption was converted from tep to TJ (terajoules) according to annual indexes for each fuel and according to the Brazilian Energy Balance data base for each year. Whenever specific data concerning emission were not available we have used recommended parametric values. The factor used are shown in Table 2.1

Table 2.1: Parameters used in the evaluation 


Unit, Conversion Factor, Conversion Factor Unit, Carbon Emission Factor (tC/TJ), Oxidised Carbon Fraction
Diesel Oil, Fuel Oil, VC 1300, , Natural Gas


 Como primeira aproximação pode-se usar os seguintes parâmetros médios     

Table 2.2 : Average Emissions / TJ

Vapor Coal, Fuel Oil, Diesel Oil, Natural Gas

2.2 Evolution of Emissions

Figure 2.1 shows the results of historical and projected carbon dioxide emissions.


Figure 2.1 : Annual Emissions of CO2 from thermal generation of electricity in public power plants.

Figures 2.2 to 2.5 show the evolution of emissions in Gg/year and those accumulated in the indicated period for N2O, NOx, CO and SO2 in the period. Emission values for the selected years and the accumulated values for the 2001/2020 period are shown in Tables 2.3 to 2.7 for the different gases considered.

A more accurate evaluation of emissions can be carried out for the past by assigning specific values for each power plant according to the fuel data. A request for the latter has been submitted to the energy agencies. We have already available data concerning coal that were used in the previous work for MCT and PNUD.   

Table 2.3 : CO2 Emissions in Gg/year


Table 2.4 : N2O Emissions in Gg/year       

Table 2.5 : NOx Emissions in Gg/year      

Table 2.6 : CO Emissions in Gg/year    

Table 2.7 : SO2 Emissions in Gg/year    



Figure 2.2: N2O Annual emissions from electricity generation in public power plants



Figure 2.3: NOx Annual emissions from electricity generation in public power plants


Figure 2.4: CO Annual emissions from electricity generation in public power plants

Figure 2.5 :SO2 Annual emissions from electricity generation in public power plants   

3 – Conclusions and Sensitivity Analysis

In the present work we have studied the emissions of greenhouse effect gases from conventional (non-nuclear) public thermal power plants used for generating electricity. We have assumed that the participation of conventional thermal power plants in the generation of electricity would grow from the present 6% (3% in 1995) to 17% of the total. This participation would still be well below the present world average that is above 60% of electricity from conventional thermal plants.

The emission from this type of plant would increase in 2020 by a factor of 5 relative to that of 1999. In two decades the emission of CO2 per inhabitant would be 0.45 ton/year larger.

The methodology starts directly from economic activity and calculates the total energy consumption and the participation of electricity therein . The schedule of thermal power plants introduction and the participation of different fuels, considering the generation efficiency of each one of them, are defined. Therefore, one can consider different hypothesis for the economic growth, for consumption and for electricity generation.

In the hypothesis considered here the participation of natural gas would be 10% of the total used in public power plants (other energy sources would be responsible for the remaining 7%). This hypothesis presents the lowest emission as compared to the same thermal participation using other fuels. However, since they are used in the base, the possible regulating effect of fuel-oil-fired power plants or even of those using mineral coal (when not linked to production commitment) is minimized.

The procedure developed here helps analyzing the impact of the present option on these emissions and of any other option to be chosen.

For example, in the hypothesis adopted here we are assuming a significant increase of efficiencies in the new power plants mainly due to the possibility of using co-generation. Without this improvement the emissions would grow in the period 6% above the projected value presented here.

This would represent 87 million tons of extra carbon released to the atmosphere in the period of twenty years.

If we consider the alternative of lower participation of natural gas, 8% instead of 10%, this would mean an emission increase of 3% in 2020 and an accumulated increase of 35 million tons of CO2 released to the atmosphere. However, this does not take into account the benefit on the regulating effect from the use of fuel-oil-fired power plants, allowing for a better use of hydroelectric power plants.

Using complementary information it is possible to vary the increments in the utilization of the installed capacity and to evaluate the net impact of this option. Another possibility offered by the methodology is to study the possible role of increasing electricity trade with neighboring countries which would also allow for a better use of the generating park of the countries involved.

The availability of an integrated model as the present one permits this type of simulation in an easy way and allows for obtaining a first evaluation of impact using technical parameters. Using the developed methodology one could also consider the effect of using biomass for electricity generation, which would reduce CO2 emission.

A computer program that permits to perform the integrated analysis of the different variables that influence emission from thermal generation of electricity will be soon available.