Cost and Complexity of Carbon Dioxide Capture Options for Power Plants
Performance and Cost Comparison
NETL has completed a comprehensive study comparing the performance and cost of various fossil fuel-based power generation technologies, with and without carbon dioxide (CO2) capture. Power generation systems investigated include integrated gasification combined cycle (IGCC), pulverized coal (PC), and natural gas combined cycle (NGCC) plants. Performance and cost evaluations were made based on a consistent technical and economic approach that reflects current market conditions for plants starting operation in 2010. Twelve different power plant configurations were analyzed and they are as follows: 1
- IGCC - based on GE Energy's gasification technology operating at the 'radiant cooling mode of operation' – without CO2 capture
- IGCC - based on GE Energy's gasification technology operating at the 'radiant cooling mode of operation' – with CO2 capture
- IGCC - based on ConocoPhillips' gasification technology – without CO2 capture
- IGCC - based on ConocoPhillips' gasification technology – with CO2 capture
- IGCC - based on Shell's gasification technology – without CO2 capture
- IGCC - based on Shell's gasification technology – with CO2 capture
- Subcritical PC power plant without CO2 capture
- Subcritical PC power plant with CO2 capture
- Supercritical PC power plant without CO2 capture
- Supercritical PC power plant with CO2 capture
- NGCC power plant without CO2 capture
- NGCC power plant with CO2 capture
Among these systems, IGCC CO2 capture is pre-combustion based, using selective Selexol technology. PC and NGCC power plant CO2 capture designs are post-combustion, using amine absorption.
Figure 1 shows the estimated thermal efficiency of the various power generation systems studied, in terms of high heating value (HHV). As shown, CO2 capture incurs a sizable thermal efficiency penalty. Comparing just the coal-based power generation plants, potential efficiency reduction for the pre-combustion IGCC plants ranges from 6.4 to 10.9 absolute percent (with an average of 8.7%), whereas an 11% reduction was estimated for post-combustion flue gas CO2 capture for the PC plants.
|Figure 1 – Net Plant Efficiency (HHV Basis) (click chart to enlarge)
These performance results showing more favorable efficiency of IGCC vs. PC types are to be expected, considering that the CO2 in IGCC syngas is much more concentrated and pressurized than the CO2 in the flue gas of a PC power plant. Both concentration and pressure aid in separating CO2 from the syngas. The high CO2 partial pressure allows for the use of physical separation processes, whereas the PC gas separation must use a chemical absorption process because of low CO2 partial pressure. Chemical absorption and regeneration is relatively more energy intensive.
Cost (Total Plant Cost and Levelized Cost of Electricity)
Figure 2, below, shows the estimated Total Overnight Cost (TOC) of the various power generation systems, with and without CO2 capture. The TOC for each plant was calculated by adding owner's costs to the Total Plant Cost (TPC). The TPC for each technology was determined through a combination of vendor quotes, scaled estimates from previous design/build projects, or a combination of the two. TPC includes all equipment (complete with initial chemical and catalyst loadings), materials, labor (direct and indirect), engineering and construction management, and contingencies (process and project). Escalation and interest on debt during the capital expenditure period were estimated and added to the TOC to provide the Total As-Spent Cost (TASC). As shown, the average TOC for IGCC CO2 capture cases is $3,568/kW, whereas the average TOC of post-combustion flue gas CO2 capture for the PC plants is $3,590/kW.
|Figure 2 – Plant Capital Costs (click chart to enlarge
The cost of electricity (COE) is the revenue received by the generator per net megawatt-hour during the power plant's first year of operation, assuming that the COE escalates thereafter at a nominal annual rate equal to the general inflation rate, i.e., that it remains constant in real terms over the operational period of the power plant. The COE results are shown in Figure 3 with the capital cost, fixed operating cost, variable operating cost, and fuel cost shown separately. In the capture cases, the CO2 transport, storage, and monitoring (TS&M) costs are also shown as a separate bar segment. In non-capture cases, NGCC plants have the lowest COE (58.9 mills/kWh), followed by PC (average 59.2 mills/kWh) and IGCC (average 77.2 mills/kWh). In capture cases, NGCC plants have the lowest COE (85.9 mills/kWh), followed by PC (average 108.2 mills/kWh) and IGCC (average 111.8 mills/kWh).
|Figure 3 – Cost of Electricity by Component (click chart to enlarge)
1. Cost and Performance Baseline for Fossil Energy Power Plants study, Volume 1: Bituminous Coal and Natural Gas to Electricity (Nov 2010).