Carbon emission and mitigation cost comparisons between fossil fuel, nuclear and renewable energy resources for electricity generation
Introduction
This paper reviews and compares the major technological advances and carbon dioxide mitigation options for the global electricity supply industry. It is a summary of a review study undertaken by the authors for the Third Assessment Report of the Intergovernmental Panel on Climate Change (IPCC, 2001). The IPCC's policy specifically excludes policy prescriptions or commentary. Whether or not liberalised electricity markets are likely to adopt the cost-saving, emission-reducing technologies included in the paper, or whether there are particular institutional obstacles to their adoption is not discussed. Suffice to say that if an investment opportunity exists to increase profit for a privately owned power generating company (or even for a state-owned enterprise), serious consideration will be given. If this same investment would also serve to offset the threat of a future carbon emissions charge, then it would make good commercial sense to invest.
The paper concentrates on carbon emissions and largely ignores the impacts of other emissions from power generation plants (other than the desulpurisation of flue gases). Other more minor greenhouse gas (GHG) emissions such as nitrogen oxides (NOx) are detailed in the Third Assessment Report (IPCC, 2001). These, together with other possible emissions from some power plants such as dioxins, whilst certainly needing to be considered in any environmental impact assessment necessary for a resource consent when developing a new plant, were not considered since they have relatively low importance.
The global electricity supply sector accounts for the release to the atmosphere of over 7700 million tonnes of carbon dioxide annually , being 37.5% of total CO2 emissions. Under business as usual conditions, the annual carbon emissions associated with electricity generation, including from combined heat and power cogeneration, is projected to surpass the level by 2020 (IEA, 1998). GHG emissions are easier to monitor and control from a limited number of centralised, large power stations than from millions of vehicles, small boilers and even ruminant animals. Therefore the electricity sector is likely to become a prime target in any future world where GHG emission controls are implemented and GHG mitigation is valued.
Several broad methods for mitigation of carbon dioxide emissions exist:
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More efficient conversion of fossil fuels: Technological development has the potential to increase the present world average power station efficiency from 30% to more than 60% in the longer term. Also, the use of cogeneration plants replacing the separate generation of power and heat offers a significant rise in the utilisation effectiveness of fuel.
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Switching to low-carbon fossil fuels and suppressing emissions: A switch to gas from coal for example allows the use of high efficiency, low capital cost, combined cycle gas turbine (CCGT) technology, resulting in lower carbon emissions per kWh of electricity generated.
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Decarbonisation of fuels and flue gases, and carbon dioxide sequestration: Decarbonisation of fossil fuel feedstocks before combustion for electricity generation can be used to make hydrogen-rich secondary fuels which in the longer term can be used in fuel cells. Decarbonisation of flue gases after combustion can become an effective GHG abatement option. In both cases the carbon dioxide can then be stored over geological time frames, for example, in depleted gas fields.
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Increasing the use of nuclear power: Nuclear energy could replace baseload fossil fuel electricity generation in many parts of the world if acceptable responses can be found to concerns over reactor safety, radioactive waste transport, waste disposal and proliferation.
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Increasing the use of renewable sources of energy: Technological advances offer new opportunities and declining costs for renewable energy technologies which, in the longer term, could meet a greater share of the rapidly growing world energy demand.
In relation to world electricity production, coal continues to have the largest share at 38% followed by renewables (principally hydro power) at 20%, nuclear at 17%, natural gas at 16% and oil at 9%. Electricity production is expected to almost double by 2020 (Table 1). However average carbon emissions per unit generated will decline over time mainly due to using new technologies with improved conversion efficiencies.
Coal-fired power generation is projected to have a major increased share by 2020 due to strong growth in countries such as India and China reflecting its importance there, together with steady growth in the USA, but a decline in Western Europe. Gas-fired plant is projected to continue to grow strongly in many world regions reflecting the increasing availability of natural gas whilst oil will lose market share. Nuclear power is projected to decline slightly after 2010 with capacity additions in developing countries and economies in transition roughly balancing plants being retired in OECD countries. Hydropower is projected to grow by around 60%, mainly in China and other Asian countries. New renewables have expanded substantially throughout the 1990s in absolute terms including wind by 21% per year and solar photovoltaics (PV) by 30% per year. Biomass and geothermal projects are also experiencing good growth. So overall, renewables are projected to continue to grow till 2020, but without significant government intervention, they will still only supply less than 2% of the electricity market share.
Section snippets
Fossil fuels
The efficiencies of modern thermal power stations using the steam cycle can exceed 40% based on lower heating value (LHV), although the average efficiency of the installed stock world wide is closer to 30%. The cost of a modern coal-fired power station with SOx and NOx controls is typically $US1 1300/kWe but less efficient designs with fewer environmental controls are cheaper and therefore often built in developing countries. Costs vary considerably depending on
Technological and economic potential of power generation systems
Several electricity generation technologies were analysed and compared for both their costs and carbon mitigation potential. Previous studies attempted to compare power generation technologies on cost alone (US DOE/EIA, 2000; WEA, 2000; OECD, 1998). The OECD data resulted from a survey of power stations due for completion between 2000 and 2005 in a wide cross-section of countries. It showed that costs can vary considerably between projects due to national and regional differences including the
Conclusions
Compared with burning coal or gas in conventional power generating plant designs, there are several alternative technological ways to generate electricity and reduce greenhouse gas emissions cost effectively. They include using plant designs which offer more efficient power generation conversion of fossil fuels, greater use of renewable energy or nuclear power, and the capture and disposal of CO2. The choice, in terms of cost savings and carbon emission reduction benefits, is very site specific
Acknowledgements
The secretariat of Working Group III of the IPCC Third Assessment Report agreed for this section of the report to be published in this revised and condensed form. The other co-authors of Chapter 3 are acknowledged, several having provided useful reviews of this analysis during the preparation of the IPCC report.
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