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Power Generation and Greenhouse Gas Abatement The Effects of Generation Efficiency Fuel Type and Renewables.

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Dev. Chem. Eng. Mineral Process., 7(5/6), pp.551-561, 1999.
Power Generation and Greenhouse Gas
Abatement: The Effects of Generation
Efficiency, Fuel Type and Renewables
G. Millar" and M-A. Hessami
Department of Mechanical Engineering, Monash University, Clayton,
Victoria 3168, Australia
* 191 Canterbury Road, St Kilda, Victoria,Australia
Power generation in Australia is responsible for about 25% of the country's
greenhouse gas emissions. Due to the abundance of coal, most power stations use
thisfitel as the primary source of energy. The high carbon content of coal combined
with the relatively poor power generation effciency of these facilities, explain the
contributions which power generation make to Australia's greenhouse gas emissions.
In this paper, the effects of these two parameters, ie, fie1 type and generation
effciency, on greenhouse gas abatement is studied It is shown that by controlling
these two factors, there is a significant potential to reduce greenhouse gas emissions
in Australia.
An analysis of the electricity market showed that renewable energy projects and
natural gas fired power stations cannot compete on price with coal fired power
stations. Carbon tares and green energy programs are seen as the most likely wqvs
to make renewable energy and natural gas competitive with coal, and thus reduce
greenhouse gas emissions caused by power generation.
Introduction
Greenhouse gas abatement is a topical and controversial subject in Australia in
the lead-up to the twenty-first century. While the potential environmental and social
551
G.Millar and M-A. Hessami
costs of greenhouse gas emissions are well documented and are a cause for
international concern [ 1, 21, it is less clear what steps governments are willing to take
on a local and national basis to help avoid these problems. This paper studies the
effects of one particular approach which the Australian government can take to
reduce greenhouse gas emissions in the context of energy production and usage. The
emphasis is placed on the use of more efficient hardware, and cleaner fuels.
Greenhouse Gases and the Greenhouse Effect
A substantial increase in the atmospheric concentration of carbon dioxide, methane,
chlorofluorocarbons, nitrous oxides and other greenhouse gases has been reported by
many researchers [ 1,3], and this increase has been attributed to human activities such
as energy production, industry, transport and agriculture.
The Intergovernmental Panel on Climate Change (IPCC) has assessed that the best
estimates of the effects of a doubling of carbon dioxide levels from pre-industrial
levels to concentrations of about 550 ppm is likely to be an increase in the mean
temperature of the Earth’s surface by 2.5 degrees Celsius; by 1990 a 25% increase on
pre industrial atmospheric CO, concentration had occurred [3]. The IPCC also
estimates that to stabilise atmospheric concentrations at 1990 levels the following
reductions in emissions would need to take place.
Table 1: Reduction Necessary to Stabilise Concentrations at 1990 Levels [l].
Greenhouse Gas
Reduction needed
Carbon Dioxide
more than 60%
Methane
15-20%
7o-ao%
Nitrous oxide
CFC- 11
70-75%
CFC- 12
75-85%
HFC-22
40-50%
Australia is responsible for about 1.4% of global greenhouse gas emissions [4].
We release greenhouse gases into the atmosphere from a number of sources as shown
in Table 2.
552
Power generation and greenhouse gas abatement
Table 2: Net Greenhouse gas emissions, Australia[4].
Sector
'YOof total emissions 1994
Energy - Stationary Sources (incl. power generation)
37.8
Energy - Transport
11.7
Energy - Fugitive Emissions
6.9
Land Use Change, Forestry and Agriculture
40.4
1.7
Industry w o n Energy)
Waste
3.3
For the purpose of this paper, the focus is placed on one of the largest contributors
to greenhouse gas emissions: power generation. Of all emissions from energy
production, approximately 88 percent is carbon dioxide [4].
Greenhouse gas emissions from electricity production account for a substantial
proportion of Australia's emissions, approximately 25%. Electricity is produced from
four main fossil fuels in Australia: black and brown coal, natural gas and petroleum
products (eg Diesel).
Table 3 shows the energy generation and subsequent
greenhouse gas emissions fiom the main fossil fuels used in Australia's power
stations.
Table 3: Greenhouse Gas Emissions from Power Generation.[5]
Fuel Type
Energy
CO,
CO
CH,
NO,
N,O
use
(kt)
(kt)
tonnes
(kt)
tonnes
10.0
800
290.4
730
PJ
Black Coal")
899.2
81558
Brown Coal
474.4
44754
8.3
240
64.1
660
Natural Gas
146.2
7474
3.2
260
23.7
10
Petroleum
28.4
1972
8.6
100
33.1
20
Total
1548.2
135758
30.2
1400
411.2
1420
Total from
3877.4
274000
4454
112800
1328
11600
Energy Sector
~~
~
Black coal mining also releases large quantities of fugitive C&.
The link between greenhouse gas emissions and power production from various
fossil fuels is clear from the data in Table 3, and the conclusion can be drawn that if
553
G.Millar and M-A. Hessami
energy usage fiom fossil fuels is reduced, the rate at which greenhouse gases are
being produced will decline. This paper will examine by how much Victoria can
reduce its CO, emissions using more efficient power generation technology and fuels
with lower carbon contents.
Power Generation in Victoria
Brown coal is the principal fuel used for power generation in Victoria and for this
reason Victoria’s greenhouse gas emissions per unit of electricity use are particularly
high as brown coal contains greater than 60% water which must be evaporated in the
combustion process. All coals also have a high carbon content, almost twice that of
natural gas.
Table 4 lists the principal generating facilities in Victoria with their annual power
output, efficiency and carbon dioxide emissions. These values have been used to
analyse the potential for reducing greenhouse gas emissions in Australia.
Table 4: Victorian Electricity Generation Capacity [6,7].
Power Station
Rating Energy
Eff. Capacity kgC0,
Generated
HHV Factor”)
0
(GWh) ( I )
(Yo) (Yo)
Brown Coal-fired:
Loy Yang A (ST)
Hazelwood (ST)
Yalloum w (ST)
Loy Yang B (ST) (’)
Energy Brix (ST)
Anglesea (ST)
Natural Gas Fired:
Newport D (ST)
Jeeralang (GT)
Hydro-Elec&c Total:
Total
Mt CO,
per year
2000
1600
1450
lo00
170
150
15595
4254
10377
4197
601
1030
29
24
27
29
24
24
89
30
82
96
40
78
I160
1400
1300
1160
1300
1300
18.1
6.0
13.5
4.9
0.8
1.3
500
466
1578
3062
302
2080
38
26
70
7
480
690
1.5
0.2
8414
41860
Note: Based on fuel gross specific energy and electricity sent out.
(1) Energy generated during the year ended 30 June 1996.
(2) Calculated as energy generated (in MWh) divided by nameplate rating (MW) and again divided by
8760 hours (no. hours in one year).
(3) Loy Yang B2 was commissioned during this period and generated for approximately 6 months.
554
Power generation and greenhouse gas abatement
To determine the possible increases in efficiency of Victoria’s major fossil fuel
power stations, their current thermal efficiencies were compared to the newest power
stations. The best brown coal fired steam generator was assumed to be 29 percent
efficient; this is the thermal efficiency of Loy Yang B which was completed in 1996.
The efficiency of the best natural gas steam turbine was considered to be equal to that
of the Newport power station which is 38 percent efficient. The efficiencies of a
modem gas turbine and combined cycle system were taken to be 40 and 60 percent
respectively; these are the efficiencies of Asea Brown Boveri’s (ABB) GT24/26 gas
turbine and the associated combined cycle system [8, 91.
The carbon dioxide emissions from a modem gas turbine and combined cycle
power plant running on natural gas were estimated using the carbon dioxide
emissions from Newport power station per MWh and comparing the efficiency of the
Newport power plant with ABB’s state of the art gas turbine and combined cycle
power plants. A modem gas turbine is therefore assumed to produce 456 kg of CO,
per MWh and a modem combined cycle power plant 304 kg of CO, per MWh.
Calculations have been made for all Victoria’s major fossil fuel fired power
stations. Table 5 shows the saving per year that could be made by replacing the older
power stations with newer coal fired steam turbines and also more efficient power
stations running on natural gas’ . The percentage CO, saving refers to the percentage
reduction in CO, emissions from power generation in Victoria.
Interested readers should refer to Millar (1997) for details of the calculation
procedure used to obtain these data [ 101.
555
G.Millar and M-A. Hessami
Table 5: CO, emissions re
Replace by
Power Station
mew coal fired
~tearnturbine
Reduction
CO,
%Co2
iced by upgrad g Victoria’s power stations.
Replace by leplace by new
Replace by
:ornbined cycle
new gas
new gas fired
turbine
steam turbine
Reduction
Reduction
Reduction
Y&O,
CO,
%Co2 co2 %co* co,
(MvYr)
(Mt/yr)
(MW
(MW
Brown Coal-fired:
Loy Yang A
Hazelwood
Yallourn W
1.02
1.45
2.21
3.14
Loy Yang B
23.76
13.35
28.89
10.60
22.95
10.98
3.91
8.47
4.02
8.69
4.66
10.09
18.96
10.34
22.37
8.51
18.42
8.76
2.85
6.18
2.95
6.40
3.59
7.78
Energy Brix
0.08
0.18
0.49
1.07
0.507
1.10
0.599
1.30
Anglesea
0.14
0.31
0.84
1.83
0.869
1.88
1.026
2.22
Natural Gas Fired:
Newport D
0.073
0.16
0.539
1.17
Jeeralang
0.071
0.15
0.117
0.25
28.23
61.10
34.22
74.06
Total
2.70
5.85
27.22
58.91
Table 5 demonstrates that Victoria could reduce its CO, emissions from power
generation by 5.85 percent by replacing old brown coal power stations with newer
more efficient power stations. The biggest savings (about 59%) in CO, emissions
fkom power generation would be realised if Victoria was to replace all brown coal
burning power stations with natural gas fired power stations as natural gas produces
about half the greenhouse gas emissions of coal. Natural gas fired combined cycle
power plants installed to replace Victoria’s current steam and gas turbines would
reduce Victoria’s greenhouse gas emissions by 74 percent.
The technology is currently available to make a dramatic reduction to Victoria’s
greenhouse gas emissions. However it is the relative cost and availability of more
efficient generating technology and natural gas that will determine the future viability
of reducing greenhouse gas emissions in Victoria.
556
Power generation and greenhouse gas abatement
Renewable Energy
Although increasing efficiency will slow down the rate at which greenhouse gases are
emitted, only the use of renewable energy sources, relatively speaking, will stop the
release of greenhouse gases by the power generation sector.
If all of Victoria's power stations were replaced by renewable power generation
facilities then the net pollution emitted per unit of electricity would be zero; this is a
very unrealistic scenario. A more realistic approach for the use of renewable energy
would be to meet the demand for increased capacity with renewable energy. This
would stop any increases in greenhouse gas emissions from power generation. Old
power stations could be replaced with state of the art gas fired combined cycle
generators when they reach retirement, thereby reducing emissions due to increased
efficiency.
Viability of Renewable Energy
The National Electricity Market (NEM) was established in Australia in May 1997
when South Australia, Victoria, New South Wales, ACT, Tasmania and Queensland
agreed to form a single competitive electricity market. The NEM is responsible for a
deregulated and reformed Australian Electricity Supply Industry.
Since the
establishment of the NEM, electricity prices on the spot market have averaged below
$20/MWh (2'/kWh), this is approximately half the pre- NEM price. However, most
electricity is currently sold under venting controls at $35/MWh.
An examination of renewable energy projects around the world shows that wind
turbines are among the cheapest renewable energy sources. Communication with a
potential wind farm developer in Victoria suggested that a price of around $90/MWh
would be needed for wind power to be viable in Australia. Clearly renewable energy
projects are a long way from competing on price with fossil fuel generation sources.
In many countries around the world governments have intervened to force
retailers to buy energy produced from renewable energy sources by imposing what
are effectively carbon taxes. In countries such as Germany, the United States, India
and the Netherlands this has triggered the formation of large wind power generation
557
G. Millar and M-A. Hessami
schemes. Carbon taxes can be justified by taking into account the social costs of
energy production.
The social costs of energy production were explained by
Hohmeyer in a study suggesting that the market price of electricity should be twice its
present value as this price increase would ensure that consumers are paying for all the
costs associated with electricity generation such as health and environmental
problems [ 1I].
Installing power generation facilities which are smaller and closer to the point of
usage gives renewable energy projects such as wind farms a chance to compete with
fossil fuel power plants especially when there is no major grid nearby. King Island,
Esperance and Cooper Pedy are some examples where wind power was successful in
replacing existing diesel generators.
The worst of the environmental impacts caused by wind turbines include noise
and visual pollution. While the visual impact of a wind turbine is a matter of personal
taste, the noise emitted by a wind farm is fairly low, it reduces to between 35 and 45
&(A) at 350 metres [ 121.
Greenhouse Gas Reduction in Australia
Extrapolating the potential to reduce greenhouse gas emissions from Victoria to
Australia it can be seen that emissions could be substantially reduced fiom the power
generation sector by installing combined cycle systems burning natural gas.
Australia is now committed to stabilising its greenhouse gas emissions at 8%
above 1990 levels. Using more efficient power generation systems running on
natural gas and installing more renewable power systems are essential in helping
Australia to achieve, maintain and exceed this target.
General Discussions
There are many ways to abate greenhouse gas emissions. The main options as
outlined above are increasing efficiency, changing to alternative fuels, using
renewable energy resources and to some extent offsetting emissions.
558
Power generation and greenhouse gas abatement
A survey of current greenhouse gas emission, current energy usage and future
availability of energy in Australia shows that there are two important points to be
made when considering reducing greenhouse gas emissions.
1. Renewable energy sources must play a far greater role in meeting our energy
requirements.
2. A greater emphasis on conserving energy and improving efficiency is needed
so that fewer resources, whether fossil or renewable, are needed to produce OUT
energy requirements.
There are of course two sides to energy production: the actual generation of the
energy and the use of the energy. It is important to look at both of these as
improvements in both power generation and usage can play a role in greenhouse gas
abatement. Energy usage is to a large extent the realm of the individual but
governments can impact on this area by regulating the efficiency of appliances.
Concentrating on increased energy efficiency alone will not stop climatic change.
Increased efficiency can reduce the rate at which greenhouse gases are released but
efficiency increases cannot stop greenhouse gases being released. Renewable energy
sources must be further developed and applied in a greater variety of areas so that the
release of greenhouse gases can be minimised.
Doubling the market price of electricity in Australia to cover the social cost of
electricity generation would be enough to make wind power a competitive power
source in the NEM. An increase in the price of electricity would also reduce
greenhouse gas emissions by making investments in energy efficiency far more
attractive.
Due to the current low price of electricity in Australia it is unlikely that natural
gas fired power plants or renewable energy will be competitive with coal power
stations. However the premium priced green energy programs being introduced
around Australia today may solve this problem.
There are several distribution companies in Australia that market premium priced
green energy and these companies are expecting that one percent of their customers
will take advantage of these green energy programs. The premium that customers
559
G.Millar and M-A. Hessami
pay to purchase green energy varies between suppliers but is in the order of three
cents per kilowatt hour. This premium is used specifically for developing further
renewable energy projects, this could amount to 400MW of green energy generation
capacity [ 131.
Creating a new electricity market selling renewable energy should bring about the
installation of a substantial quantity of renewable energy projects. Renewable energy
capacity will hopefully be able to supply any increase in energy demand and reduce
the need for additional fossil fuel fired power stations.
The NEM does have advantages in terms of greenhouse gas reduction in Victoria,
as a link is intended between Tasmania and Victoria which will enable the excess
generating capacity from Tasmania’s hydroelectric schemes to be used, reducing the
need for building more coal fired plants. Tasmania has produced 8679 GWh of
electricity in 1994 with an installed capacity of 2.26 GW. This averages out to a
system load of just over 1 GW and a peak load of 1.4 GW [14]. From these figures it
can be seen that Tasmania has the potential to export hydroelectricity to Victoria and
therefor reduce Victoria’s green house gas emissions.
The installation of a major grid connection to Tasmania and the establishment of
the green energy programs currently offer the greatest potential to reduce or at least
prevent a further increase in greenhouse gas emissions from power generation.
Conclusions
This paper has discussed possible energy savings that could be made to reduce
greenhouse gas emissions in power generation sector. The electricity market has
been examined and it has been found that renewable energy projects and even natural
gas fired power stations cannot compete with coal fired power stations due to
Australia’s cheap and easily accessible coal reserves. It has been suggested that there
are long term advantages for Australia to have a renewable energy industry. The
current premium priced green energy programs have the potential to make wide
spread renewable energy projects in Australia a reality. A renewable energy industry
560
Power generation and greenhouse gas abatement
will not only reduce our greenhouse gas emissions but it will also reduce our reliance
on the world’s depleting fossil fuel’s reserves.
Australia has the potential to greatly reduce its greenhouse gas emissions. But for
that to happen the government will need to accept responsibility for sectors over
which it has a degree of control, to endorse the development of more efficient natural
gas fired combined cycle power stations when old power stations need replacing, and
to encourage renewable energy projects.
Nomenclature
CH,
CO,
co
GT
GWh
HHV
kt
Methane
Carbon Dioxide
Carbon Monoxide
Gas Turbine
Giga Watt hour
Higher Heating Value
Kilo Tonne
Mt
Mt/yr
MW
NOx
N,O
PJ
ST
Million Tonne
Million Tonnes per year
Mega Watt
Oxides of Nitrogen
Nitrous Oxide
Peta Joule (10’’ J)
Steam Turbine
References
I. Mitchel, C.D. 1992. Grappling with Greenhouse: Understanding the science of climate change.
National Greenhouse Advisory Committee, 39.
2. Kreith, F., and Burmeister, G. 1993. Energy Management and Conservation, National Conference of
State Legislatures.
3. Intergovernmental Panel on Climate Change. 1990. Working Group 1.
4. Department of Primary Industries and Energy. 1997. Green Paper on Sustainable Energy Policy for
Australia, 20-22.
5 . Australian Bureau of Statistics. 1994. Energy Accounts for Australia, 26, 114.
6. Energy Projects Division Department of Treasury and Finance (Victoria). 1997. Victoria’s Electricity
Supply Towards 2000,20.
7. State Electricity Commission of Victoria. 1992. The SECV and the Greenhouse Effect, 14.
8. ABB Power Generation. 1996. Advanced Cycle System: The innovative answer to lower the cost of
electricity.
9. Stokes P.A. 1996. Developments in Combined Cycle Power Technology, 31.
10. Millar G. 1997. Greenhouse Gas Abatement: What can the Government and Individuals do?. 12-17.
11. Hohmeyer 0. 1990. Social costs of electricity generation: Wind and Photovoltaic Versus Fossil and
Nuclear. Contemporary Policy Issues 8,3.
12. Boyle G. 1996. Renewable Energy: Power for a Sustainable Future, 296-301.
13. Wind Power Monthly. 1997. Launch of Largest Ever Green Power Scheme. Wind Power Monthly
May, 39.
14. Electricity Supply Association of Australia (ESAA). 1996. Electricity Australia 1996,30-33,4041
561
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