Each power plant thus presents a unique opportunity when looking at the issue of increasing
efficiency, and reducing emissions. Figure 5 illustrates a relationship between efficiency
improvement and CO2 emissions (for CFPPs using bituminous coal) highlighting the lower
emissions of higher pressure CFPPs. Upgrading from subcritical operation to supercritical steam
conditions (with required pollution technology) could add at least 20 years to a plant’s service
life,22 depending on the regulatory and environmental regime in place. A subcritical plant could
achieve at best 40% efficiency (on an LHV basis), while a supercritical steam plant could
potentially achieve an efficiency two points higher and emit 4% less CO2.
23 Advancing the
technology from a supercritical to an advanced ultra-supercritical CFPP could see an efficiency of
46% to 48%, which could mean as much as 18% to 22% less CO2 per MWh generated than an
equivalent-sized subcritical PC unit.24 However, “[m]ajor plant upgrading involving conversion
of subcritical to supercritical or ultra-supercritical ... has seldom progressed beyond studies
because of the high cost.”25