Commercial demonstration of advanced coal technologies
The development of emission controls on coal fired power plants can be used as an example of technology progression through the required TRLs. In the mid-20th century, coal-fired power plants had limited controls for sulphur dioxide (SO2), nitrogen oxides (NOx) or mercury emissions. Throughout the past 50 years, various technologies to control these pollutants have progressed from about TRL-4 to full commercial availability. This experience has shown that the achievement of TRL-9 can take approximately 20 or more years. This long development period is largely dictated by costs, design, construction and operational testing activities associated with the pilot plants (to achieve TRL-7), sub-scale commercial demonstration plants (to achieve TRL-8) and the first full-scale, commercial deployment (TRL-9).
The use of TRL in the context of advanced coal technologies has some drawbacks. The TRL classification system was devised by NASA to assess technology readiness only. It was not designed to address ‘economic’ readiness. Thus, a technology may reach TRL-9 and be technically mature and still not meet project economic requirements. The TRL system does not address the economic feasibility of deploying the technology.
In the past few years, ‘full scale’ coal-fired power plants purchased by utilities have a net capacity exceeding 400 MWe and largely greater than 600 MWe. For the purposes of a TRL assessment of advanced coal technology, it is suggested that TRL-9 would be achieved by a power plant in the capacity range 400-800 MWe (net). By this metric, successful operation of the Kemper County (524 MWe) would achieve TRL-9, albeit at a CO2 capture rate less than the 90% commonly imagined. Successful operation of Boundary Dam (110 MWe) and FutureGen (200 MWe) would achieve TRL-8: sub-scale commercial demonstration plant. Technology suppliers to Boundary Dam and FutureGen may claim ‘commercial’ operation, but it would be operation at a scale significantly less than that commonly purchased by utilities.
Integrated CCS demonstration is crucially needed
Although current technology needs further improvements, it is extremely important to demonstrate CCS on a commercial scale as soon as possible. This is needed for the demonstration of capture technology operating in an integrated mode in a real power plant and in a real power grid environment. It is also necessary to demonstrate sequestration/storage at sufficient scale that has credibility for further deployment. Unless progress is made at the commercial CCS demonstration scale to answer these two basic issues it will become increasingly difficult to justify continued R&D funding on potential improvements to capture and storage technologies.
If multiple CCS demonstrations with improved technologies are to be achieved at large-scale (i.e., TRL-9) by 2020 to proceed with commercial deployment, then many technologies need to be approaching the pilot plant stage (TRL-7) today. However, currently there are very few organizations funding demonstrations at one-tenth to full commercial-scale. Some pilot plant scale capture projects have been funded but advancing to sub-commercial scale demonstrations and larger will require an order of magnitude greater level of funding.
The total capital cost of investment for PCC demonstration would be significantly lower if PCC was retrofitted to an existing coal plant than if a new SCPC with PCC was constructed. However, the technical risk is probably not very different from that associated with a newly built SCPC with PCC. PCC retrofit to an existing plant will also incur a loss of power output of perhaps 30% so that replacement power may be needed.