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
Fuel
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
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.
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