High efficiency low emissions technologies
The IEA advocates a two-step strategic approach to prepare coal generation for a low emissions future:
- Improving the efficiency of coal-fired power production while minimising emissions where economically and technically feasible.
- These include supercritical, ultra super critical and integrated gasification combined cycle generation plants, as well as novel technology approaches for power generation.
- Developing CCS such that it can subsequently be integrated into power plants using fossil-fuels (e.g. gas, coal, lignite, diesel and oil) and other industrial plant (e.g., steel mills, smelting and refining) when the implementation conditions are appropriate.
The high efficiency, low emissions road map
Step 1: Improving power plant thermal efficiency while providing meaningful reductions in CO2 emissions
The average thermal efficiency of coal-fuelled power plants is 33%, which is substantially below the state of the art rate of 42% (Chart 1). This efficiency varies across the major coal-using countries from under 30% to 45%. Such differences arise due to the age of the plant, coal quality and impurity profiles (e.g. ash, sulphur and moisture content and physical and chemical “rank” properties), operating conditions, maintenance practices and application of new and improved technologies.
Source: Adapted from IEA Insights Series (2013), 21st Century coal: advanced technology and global energy solutions, report for the Coal Industry Advisory Board, p 20; based on information from RWE AG.
Note: The figure shows CO2 reductions at coal-fuelled stream-electric power plants from higher efficiency / CCS technologies (hard coal, 26 GJ/kg HHV, North Sea cooling water).
As illustrated in Chart 1 above, CCS – the only technology capable of achieving the necessary deep cuts – can reduce CO2 emissions by up to 90%. These technologies will also be required for other fossil fuel generation, including gas, and other industrial plant.
The IEA estimates that advanced coal technologies, including Supercritical (SC), Ultra-supercritical (USC) and integrated gasification combined cycle (IGCC) plants, could deliver 7% of the necessary CO2 emissions cuts in the power sector through to 2050. This is just as much as the estimated contribution of solar photovoltaics (PV) and slightly less than the potential contribution of wind turbines. CCS could deliver almost one third of the entire mitigation effort needed in the power sector.
Source: IEA Insights Series (2013), 21st Century coal: advanced technology and global energy solutions, report for the Coal Industry Advisory Board, p 22; based on data from the Electric Power Research Institute.
List of abbreviations: A-USC PC is advanced ultra-supercritical pulverised coal; USC PC is ultra-supercritical pulverised coal; SC PC is supercritical pulverised coal; EOR is enhanced oil recovery aimed at boosting oil recovery above an average of about 40 per cent by injecting CO2.
As illustrated by Chart 2, some advanced coal power technologies are relatively mature, but many are still in the development phase. Technologies are particularly vulnerable during this period. For example, first-of-a-kind, project cost estimates often increase over time as more information is assembled about the scale-up and application challenges. To maintain momentum during this critical phase it is essential that there is a clear pathway to future cost reduction.
Step 2: Advancing CCS technologies to commercial scale
In the IEA’s core “New Policies Scenario”, the average efficiency of coal-fired generation worldwide improves from 36% to 40% between 2011 and 2035, as old plants, based on subcritical technology, are retired and increasingly replaced by supercritical and other higher efficiency technologies. Over half (55%) of total emission savings in the IEA’s core scenario come from efficiency improvements across all sectors in the global economy. In particular, efficiency gains in power plants, transmission and distribution, refineries, and oil and gas extraction are responsible for around 7% per cent of emission savings in 2035. CCS remains a developing technology in this scenario.
The role of CCS becomes more critical under other scenarios for greater emissions reductions such as the IEA’s “450 Scenario”, which assumes new policy actions consistent with a 50% chance of limiting the long-term average increase in global temperature to 2°C. Here, CCS is projected to account for nearly 60% of total coal-fired electricity generation in 2035. The IEA argues that a 2°C target “puts into sharp focus the need to increase the adoption of technologies such as CCS rapidly and at scale”. Moreover, in its 2014 Fifth Assessment Report, the Intergovernmental Panel on Climate Change projects that without CCS, the cost of achieving that target between 2015 and 2100 increases by 138%.
The challenge for CCS is not to prove the feasibility of its constituent technologies, but to deploy integrated large-scale projects at a cost that is commercially competitive. While the same commercial challenge faces all low emissions technologies, CCS does have the advantage of being applicable to any large point source of high concentration CO2 emissions. CCS can be applied to power generation (from coal, gas, diesel, fuel oil or biomass), production of industrial goods (such as iron and steel, cement and fertiliser), coal-to-liquids processes, oil refining and natural gas processing. CCS allows these power generation technologies to achieve low emissions outcomes while delivering power on an “as it is needed” basis. This type of power generation technology also has the advantage of being independent of the weather while achieving low emissions outcomes.
As illustrated in Chart 2 above, CCS – the only technology capable of achieving the necessary deep cuts – can reduce CO2 emissions by 80 to 90%. These technologies will also be required for other fossil fuel generation, including gas, and other industrial plant.
An important relationship between plant efficiency and the need for CCS needs to be emphasised. Compared to a subcritical plant with an efficiency of 35%, an ultra-supercritical coal plant of the same size with an efficiency of 45% requires about 25% less CO2 capture. Consequently, for the same net electrical output, higher-efficiency plants require CCS units with smaller capacity; hence, high efficiency plants are more likely to have lower operating costs for CCS.
It follows that Step 1 involving deploying high-efficiency, low emissions technologies to increase plant efficiency is important to subsequently reduce the eventual cost of CO2 abatement in Step 2.
Micronised refined coal – direct injection carbon engine
Australia is contributing some critical HELE technology R&D into the Direct Injection Carbon Engine known as DICE.
Australian National Low Emissions Coal (ANLEC) R&D was recently commissioned to report into the viability of micronised refined coal fuel for a Direct Injection Carbon Engine known as “MRC-DICE”.
The report suggests that, with relatively little development, DICE could be competitive for remote area power where the alternative is diesel generated power. It also suggested that DICE offers the opportunity for a step-change in the capital cost base of new pulverised coal plant in Australia while providing the required flexibility to allow coal to support intermittent renewable generation.
COAL21 funding has been approved for an experiment to test MRC-DICE in a 1 MW scale test engine. The engine will run on Micronised Refined Coal (that is, a finely ground coal in a water slurry). A DICE engine using coal can provide both dispatchable electricity supporting renewables and base load generation both with reduced emissions compared to current coal-based technology. The technology is scalable and can support CCS at reduced cost.