Generation retrofits: New report considers the implications

Reviews of national ambient air quality measures, as well as licence reviews in New South Wales and Victoria, have helped bring a focus on the contribution of coal-fired power stations to the fore this year.

The National Environment Protection Measures (NEPM) for ambient air quality are currently under review and have raised the question of whether Australia’s coal-fired fleet should or could be retrofitted according to the highest international standards. A new report, commissioned by the Australian Energy Council, considers the implications of retrofitting power stations along with a cost-benefit analysis. So what did it find?

Retrofitting Australia’s coal-fired fleet

Leading international engineering consultants, WSP, were commissioned to estimate the costs and non-financial implications (such as additional water demand and physical limitations) of retrofitting Australia’s coal-fired fleet with the best available technologies for emissions control.

Australian coal-fired power stations have a range of air emission control technologies in place and many were built in the 1980s and 1990s.

Abatement technology continues to evolve and the European Union is often cited as the gold standard for Australia to follow to tackle three air pollutants: Particulate matter (PM₁₀ and PM_2.5), sulphur oxides (SO_x) and nitrogen oxides (NO_x). The WSP evaluates the viability of Australian coal-fired power stations being retrofitted to meet EU standards for those three air pollutants.

The costs

WSP finds that coal-fired power stations will incur significant costs if they were required to retrofit. While costs vary depending on the size and type of a unit, for a single 720 MW black coal unit, the costs could reach as high as $432 million in capital expenditure and $27 million in annual operating costs.[1] If a station has more than one unit, which is standard, these costs would then need to be multiplied. In NSW there are 16 black coal units around this size. These cost estimates are conservative because they do not take into account whether power stations have the physical space to install additional abatement technology or the financial costs of having a power unit out of service while being retrofitted.

Installing new technologies will depend on whether it is compatible with the existing equipment, the plant’s overall foot print, operating parameters and interfacing or connection points, the report says.

Environmental benefits

The report also considered the environmental benefits of making these retrofits. In the case of particulate matter, where abatement technology is already installed, WSP found the viability of installing an additional retrofit on top of current technology ‘is unlikely to be reasonable’ as many plants already meet EU standards.[2] For sulphur oxides and nitrogen oxides, the Commonwealth Government’s Department of the Environment and Energy has found that these emissions are already at a level so low that they are unlikely to have a negative health impact.[3]

The benefit then of reducing these emissions must be balanced against the high costs, as well as any impact in other environmental areas. The technology used to reduce sulphur oxides needs up to an extra 878,000,000 litres of water per year to operate, while nitrogen oxide abatement technology creates additional greenhouse waste streams, namely ammonia slip and nitrous oxide emissions.[4] Nitrous oxide (N20) is ‘another greenhouse gas that is approximately 300 times more harmful to the environment than CO₂ [carbon dioxide] in terms of contributing to global warming’.[5]

Trade offs and local issues

There are other trade-offs too that need to be considered. For example, NO_x and SO_x abatement will reduce plant efficiency leading to an increase in CO₂ emissions.

Outside of affordability and sustainability issues, there is also a question of the operational impact of retrofitting on the plant reliability. Further installations may inhibit the viability of flexible or two-shift operation. This is significant because flexible generation is needed to support a grid transitioning to variable renewable generation.

Consideration of the respective age of plants also needs to be taken into account given the costs of retrofitting, when combined with the need to have units taken out of service while retrofitting occurs, has the potential to render continued operation of some older power stations uneconomic before the electricity system has invested in replacement capacity.

WSP also notes that when considering additional abatement, the geographical locations of the plant and the air shed in which it operates need to be taken into consideration because the ‘level of abatement that the power plant is required to achieve may (and often does) vary depending on whether there are other emitting sources in the air shed (such as other power plants or industrial operations); whether the area is highly developed with emissions from transport sources; and the density of sensitive receptors within the air shed’.[6]

The extent of the air shed from NSW power stations was the subject of another report, the Ewald Report, commissioned in November 2018 by activist group Environmental Justice Australia. The findings of that report were challenged by a subsequent peer review by EnRisks Environmental Sciences which found substantial problems with the methodology used (subject to an earlier EnergyInsider article “Power station particulate emissions: Flawed claims re-emerge”)

In assessing individual emissions, the new WSP report found the following:

Particulate Matter

Most particulate matter emissions arise from natural causes, such as sea salt, dust storms or bushfires, as the recent events in Sydney show. Of the human made sources, wood heaters and road vehicles make larger contributions than coal-fired power stations. Coal-fired power stations represent a comparatively small source of particulate emissions thanks largely to the wide geographic dispersal of the plants and their existing particulate abatement technologies.

In these circumstances, WSP found that the viability of installing an additional retrofit on top of current technology ‘is unlikely to be reasonable’, especially since many plants already meet EU standards.[7] If retrofitting were to be mandated, WSP estimates that a 720 MW black coal unit would incur costs of $67 million in capital expenditure and $5 million each year in operating costs.[8] Since all large Australian plants have more than one unit, these costs would need to be multiplied accordingly.

Sulphur Oxides

SO_x arise from mostly human sources, and governments have implemented various regulations to reduce SO_x emissions particularly from transport. These regulations have proven effective and the Australian Government’s Department of Environment and Energy factsheet reports that ‘the amount of sulphur dioxide in the air is at acceptable low levels in most Australian towns and cities’.[9] While coal burning does emit SO_x, Australian coal has a relatively low sulphur content. This has given it added export value because it can avert the need for expensive abatement technology when used overseas in place of local coal.

If a power station were to install abatement technology, it would likely be in the form of a wet flue gas desulphurisation system because it achieves the highest SO_x removal efficiency. To be retrofitted on a 720 MW black coal unit, WSP estimates a capital expenditure of $277 million and an annual operating cost of $11-14 million. 

Nitrogen Oxides

Fossil fuel combustion, along with motor vehicle emissions, are two major sources of NO_x emissions. While the Department of Environment and Energy has concluded that ‘even the highest levels of nitrogen dioxide reached in most Australian towns and cities are thought to be acceptable for humans’,[10] each state government nonetheless regulates NO_x emissions through a uniform framework to ensure public health is maintained.[11] If abatement technology was mandated, there would be not only financial but also adverse environmental consequences that require consideration.

For a 720 MW black coal unit, WSP estimates a capital expenditure of $88 million and an annual operating cost of $7-8 million, which would be multiplied depending on the number of units.[12] Installing NO_x abatement technology will also likely create additional greenhouse waste streams, namely ammonia slip and nitrous oxide (N₂0) emissions.[13] Ammonia slip can lead to the contamination of fly ash, preventing it from being beneficially reused for other carbon reduction services (such as a substitute for cement).[14] As stated above, the release of N20 emissions is an even greater concern due to its potential to worsen climate change so such trade-offs need to be carefully considered.

Conclusion

Power plant operators continually adopt new measures within the reasonable capability of their existing plant to minimise various emissions based on local conditions. However requiring existing plants to undertake major retrofits would have significant operational implications.

The WSP Report complements the earlier EnRiskS Review and highlights the need to consider Australia’s local circumstances when assessing retrofits. Australia is characterised by relatively clean air that is already stringently regulated to ensure man-made pollutants do not pose a material public health risk. The need for objective and localised analysis is important because an expensive change, such as retrofitting, could have widespread impacts on the costs and operability of Australia’s existing dispatchable power stations and potentially create other adverse environmental consequences.

Download the WSP Report and EnRisks Review.

[1] These figures represent the accumulative cost of installing fabric filters to abate particulate matter, wet flue gas desulphurisation to abate sulphur oxides, and selective catalytic reduction to abate nitrogen oxides. See page 4 of the WSP Report for a full breakdown of the costs.

[2] WSP, Considerations for Retrofitting Emissions Control Systems in Australian Coal Power Plants (October 2019), p1.

[3] Australian Government, Sulfur Dioxide: Air Quality Fact Sheet (2005), Department of the Environment and Energy, https://www.environment.gov.au/protection/publications/factsheet-sulfur-dioxide-so2.

Australian Government, Nitrogen Dioxide: Air Quality Fact Sheet (2005), Department of the Environment and Energy, https://www.environment.gov.au/protection/publications/factsheet-nitrogen-dioxide-no2.

[4] This is assuming the plant operates for 8,000 hours per year at full load. WSP Report, p35. 

[5] WSP, Considerations for Retrofitting Emissions Control Systems in Australian Coal Power Plants (October 2019), p39.

[6] Ibid at p20-21.

[7] Ibid at p1.

[8] Ibid at p4. 

[9] Australian Government, Sulfur Dioxide: Air Quality Fact Sheet (2005), Department of the Environment and Energy, https://www.environment.gov.au/protection/publications/factsheet-sulfur-dioxide-so2.

[10] Australian Government, Nitrogen Dioxide: Air Quality Fact Sheet (2005), Department of the Environment and Energy, https://www.environment.gov.au/protection/publications/factsheet-nitrogen-dioxide-no2.

[11] This is achieved through the National Environment Protection Measures (NEPM).

[12] WSP Report at p4. 

[13] Ibid at p38.  

[14] Ibid at pp5-6.