Update techno-economic benchmarks for fossil fuel-fired power plants with CO2 capture

Publication Overview

Publication Summary

• With little significant technology improvement in the interim two years, the performance of USC PC plant in the current study was very similar to that in the earlier study. Over the same period, however, H-class GT (gas turbine) developments had led to a 1%-point efficiency improvement in NGCC plant.
• Due to the concentration of CO2 in the flue gas from coal-based plants, the levelised cost of electricity (LCOE) increases by more than 80% as the CO2 capture rate is increased from zero to 90%. For both the unabated USC PC case and the 90% capture case, the LCOEs were 1 to 2% higher than the costs in the earlier study. Despite significantly increased CAPEX, the increases in LCOE were tempered by lower prices for limestone and coal.
• Although the estimated CAPEX for NGCC was around 5% lower, the higher costs of maintenance and higher gas price resulted in LCOEs for the baseline (reference) case and the 90%-capture case being 1 to 3% higher than comparable cases in the earlier study. A decrease in the CO2 avoidance cost (CAC) was attributable to the slightly higher reference LCOE (i.e. with no capture).
• For both natural gas-fired and coal-fired plants, increasing the CO2 recovery from 90% to 99% (USC PC) and 98.5% (NGCC) yielded only modest increases in the CAC – 5% (NGCC) and 4.3% (USCPC).
• Flue gas recirculation was found to be a particularly effective option to reduce the costs associated with carbon capture on NGCC plants. Recirculation of around 50% of the exhaust gas to the gas turbine inlet led to a higher CO2 content and the need for less flue gas to be treated, leading to substantial savings in the CAPEX and OPEX of the capture unit. For the 90% and 98.5% capture rate cases, the LCOE decreased by 2-3%, whilst the CAC was reduced by between 8 and 12%.
• There are good reasons to expect the techno-economic performance of NGCC plants with CCS to improve further in the future. First, new materials are emerging for application in the gas turbine that could lead to net increases in electrical efficiency of more than 2%-points for both the unabated and 98.5% capture rate cases. Second, technology enhancements for oxy-fuel gas turbine designs could reduce the LCOE by 13%. Finally, integration of a molten carbonate fuel cell (MCFC) with an NGCC not only increases the power output but could also raise the efficiency to close to 60% – with an LCOE of €64.4/MWh.
• The operating flexibility of USC PC and NGCC cases with capture was explored. As shown in an earlier IEAGHG study2, ‘solvent storage’ and ‘on/off capture’ remained viable options, whereas the present cost of ‘battery energy storage’ made it unattractive for use at scale.
• While operating flexibility is a valuable service in the contemporary energy market, there is a trade-off with efficiency. This trade off was investigated for coal-fired power plants. It was found that the 700°C steam temperatures targeted in advanced-USC PC plants were not particularly compatible with good operating flexibility. It was envisaged that conventional USC PC designs would remain the technology of choice for flexible operation within grids with highly variable demand, such grids becoming more common.