BACKGROUND INFORMATION
A new paper by three Australian researchers, published in the international peer-reviewed journal Energy, looks at 16 electricity generating technologies as candidates for meeting future greenhouse emission reduction targets.
The technologies are assessed in terms of their potential to produce reliable, continuous, baseload power. The assessment covers performance, cost and carbon emissions.
Cost, and the impact of carbon pricing on that cost, is analysed on the basis of 15 comprehensive cost studies published over the past decade. Similarly the carbon intensity estimates are based on 14 published studies of life cycle greenhouse emissions from electricity generation. The comprehensive range of authoritative studies analysed (including research from the International Energy Agency, Energy Information Administration, Massachusetts Institute of Technology and the Intergovernmental Panel on Climate Change) means that the results that emerge are reliable, comparable and representative.
For a technology to be considered fit-for-service as a baseload generator it needs to be scalable, have a reliable fuel supply, a low or moderate emissions intensity, and high availability without the need for a large external energy storage facility.
It turns out that technology options for replacing fossil fuels, based on established performance and objective cost projections, are much more limited than is popularly perceived. The review identifies only five proven low-emission technologies that could meet this set of fit-for-service criteria for the supply of baseload power. The technologies are: pulverised fuel coal combustion (PF coal) coupled with carbon capture and storage (CCS); integrated gasification combined cycle coal (IGCC) with CCS; combined cycle gas turbine (CCGT) with CCS; nuclear; and solar thermal with heat storage and gas turbines.
Of these five, the only renewable technology is solar thermal with heat storage and gas backup. However, this is the most expensive of the technologies examined and replacing coal with solar thermal power would require a carbon price of over $150 per tonne of emissions.
The paper summarises the joint cost and emissions results in the diagram below. This shows how the assessed cost per megawatt-hour of electricity varies with the technology used and the price set for carbon dioxide emissions. These prices, known as levelised costs of electricity, are the accepted way of expressing the average cost of generating electrical energy over the lifetime of a plant. They are regarded as a good indicator of the average wholesale price the power station owner would need to break even, in financial terms, and can be standardised across different technologies (and so are comparable).
In the diagram, the five fit-for-service technologies are compared with costs for conventional coal-fired generators using pulverised fuel (PF). The point where each line hits the vertical axis on the left is the cost when there is no carbon price, as happens now. It shows that a modern coal power station produces the cheapest power.
As the emission price (e.g., carbon tax) rises, so does the electricity cost. Coal-based power rises fastest because it has the greatest emissions. The points where the line for PF coal crosses the other lines represent the carbon prices where each technology becomes more economic than traditional coal-fired power.
Nuclear stands out as the cheapest solution to provide low-emission baseload electricity over almost the whole carbon price range shown. The next cheapest is CCGT (natural gas) with CCS, which needs a carbon price of just over $30. To justify building either of the two coal technologies (PF or IGCC) with CCS requires a carbon price over $40.
According to international experience, if nuclear energy were adopted in Australia its initial cost (termed ‘first-of-a-kind’) would be about $30 per MWh higher than in the diagram, but would come down to that level as more plants were built.
