Baseload Coal Investment Decisions under

CO2 tax less than $29/ton would lead companies to continuing to choose PC, paying the tax ... To provide insight for a decision maker thinking about a...
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Environ. Sci. Technol. 2007, 41, 3431-3436

Baseload Coal Investment Decisions under Uncertain Carbon Legislation JOULE A. BERGERSON* University of Calgary, 2500 University Avenue, Calgary, Alberta T2N 1N4, Canada LESTER B. LAVE Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213

More than 50% of electricity in the U.S. is generated by coal. The U.S. has large coal resources, the cheapest fuel in most areas. Coal fired power plants are likely to continue to provide much of U.S. electricity. However, the type of power plant that should be built is unclear. Technology can reduce pollutant discharges and capture and sequester the CO2 from coal-fired generation. The U.S. Energy Policy Act of 2005 provides incentives for large scale commercial deployment of Integrated Coal Gasification Combined Cycle (IGCC) systems (e.g., loan guarantees and project tax credits). This analysis examines whether a new coal plant should be Pulverized Coal (PC) or IGCC. Do stricter emissions standards (PM, SO2, NOx, Hg) justify the higher costs of IGCC over PC? How does potential future carbon legislation affect the decision to add carbon capture and storage (CCS) technology? Finally, can the impact of uncertain carbon legislation be minimized? We find that SO2, NOx, PM, and Hg emission standards would have to be far more stringent than twice current standards to justify the increased costs of the IGCC system. A CO2 tax less than $29/ton would lead companies to continuing to choose PC, paying the tax for emitted CO2. The earlier a decision-maker believes the carbon tax will be imposed and the higher the tax, the more likely companies will choose IGCC w/CCS. Having government announce the date and level of a carbon tax would promote more sensible decisions, but government would have to use a tax or subsidy to induce companies to choose the technology that is best for society.

Introduction This paper has three goals: 1. To show how an engineeringeconomic analysis should be done for a utility that needs new capacity now and is choosing among coal technologies. 2. To provide insight for a decision maker thinking about a new coal plant and worried about more stringent emissions standards for pollutants and carbon dioxide (CO2), given his/her expectations about carbon regulation. 3. To provide insight to the U.S. Department of Energy, other regulators, and society about the differences between the choices that a private company would make and those that society would prefer. We examine policy instruments that would lead a private party to choose the optimal public decision. The rising demand for electricity in the United States together with the high price of electricity from natural gas * Corresponding author phone: (403)220-7794; fax: (403)282-9154; e-mail: [email protected]. 10.1021/es062198e CCC: $37.00 Published on Web 03/28/2007

 2007 American Chemical Society

generation plants leads to a demand for additional baseload generation capacity. Faced with the need for more baseload generation, American Electric Power proposes to build an IGCC plant, in part to resolve technology uncertainties before baseload capacity is needed in the future (1). Texas Utilities recently proposed 11 new PC plants with full environmental controls and provisions to retrofit them for carbon capture. Due to increased public pressure, they have recently modified their proposal to 3 plants; 2 of which will be IGCC and they will issue a request for proposals for capture technologies to be installed during plant construction (2). While some new capacity will come from renewable resources, such as wind and photovoltaic, much of it will be powered by coal or nuclear. In many regions of the U.S., a coal-fired generation plant will produce the cheapest reliable, dispatchable electricity. Coal-fired power plants have a history of generating massive amounts of air pollution and carbon dioxide. Someone planning a new coal-fired plant today faces uncertainty concerning how restrictive emissions standards will be on conventional pollutants, heavy metals, and greenhouse gases. Available technologies could handle all of these problems, but they are more expensive than a simple pulverized coal plant. In the extreme, a planner must decide between building a low cost plant that might be obsolete in a decade or a super-clean plant whose generation costs are so high that the plant could not compete in the current market. We examine the current choices and uncertainties that a planner faces. The analysis clarifies, subject to the expectations of the planner, what is the best choice for a new plant.

Method While comparing the costs and performance of operating plants is most desirable, advanced plants with the technology required to overcome future problems have not been built. Thus, we base our analysis on the IECM v. 5.02 (Integrated Environmental Control Model), a publicly available model developed at Carnegie Mellon University to enable the U.S. Department of Energy and others to compare the performance, emissions, and cost of various electricity generation technologies, assuming a range of plant characteristics, fuel types, and emissions constraints (3). Although this is a model, it has been fitted to the best recent costs of actual plants and of detailed engineering estimates of new plants. We model plants with similar power output (approximately 450-480 MW-net) and burn the same coal (Illinois #6 with 3.25% sulfur and a heating value of 10 900 BTU per pound; we also consider Pittsburgh #8 coal). We assume the following: 1. a capacity factor of 75%; 2. Illinois #6 coal costs $35/ton; 3. private companies use an interest rate of 10%; 4. plants last 30 years; and 5. society makes decisions using an interest rate of 3%, reflecting the social rate of return on new investment. Several parameters are varied in a sensitivity analysis. The costs are in 2002 dollars, corrected for inflation. All weights are in short tons.

Literature Review Previous studies compare PC and IGCC systems (4, 5) and the capital costs can differ by 1-20% (1-3, 6). Efficiencies of 30-40% (HHV) are generally assumed for both technologies, depending on technology type, coal type, environmental controls, and operating conditions. Carbon capture technology has substantial energy and cost penalties. The cost penalty is higher for the PC system (61-84%) than the IGCC system (20-55%) (2). IGCC or PC plants could be made “sequestraVOL. 41, NO. 10, 2007 / ENVIRONMENTAL SCIENCE & TECHNOLOGY

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TABLE 1. Environmental Controls for PC and IGCC Systems emission controls

PC efficiency IGCC efficiency

plant type

CO2 capture system

SO2

NOx

PM

Hg

supercritical

amine 90% shift + Selexol 90%

FGD 98% Selexol 98%

infurnace controls + SCR 95% SCR 50%

ESP 99% raw gas cleanup 100%

injected carbon 93% undeteremined 93%

GE gasifier

TABLE 2. Output of IECM Based on Input Specifications for Each Case private cost ($/kWh) capital O&M total cost PC uncontrolled PC controlled PC controlled + CCS IGCC baseline IGCC controlled IGCC controlled + CCS

0.021 0.027 0.036 0.030 0.031 0.035

0.019 0.025 0.051 0.024 0.025 0.039

0.040 0.051 0.087 0.054 0.055 0.074

efficiency (% - HHV)

SO2

40.1% 39.3% 29.2% 34.4% 33.4% 29.3%

0.049 0.0012 0.0000080 0.0012 0.0013 0.0015

tion-ready” (7). Other studies have addressed retrofitting carbon capture technology (8). American Electric Power (5) found that current environmental regulations do not justify the additional expense of the IGCC plant over a PC plant, but they conclude that even with the uncertainty of future carbon regulation, they would invest in an IGCC plant due to fuel flexibility, byproducts and product flexibility, and furthering the commercialization of the IGCC technologies. The Electric Power Research Institute assessed the costs associated with retrofitting an IGCC (GE gasifier) facility for CCS with and without forethought of this retrofit when the plant is built (9, 10). Preinvestment adds a cost premium of 3% without CCS and 22% with CCS (over the original plant without CCS or preinvestment). However, the retrofit without preinvestment would result in a cost of electricity 30% greater than the preinvestment case. Sekar et al. (4) found that the then current European prices for carbon (roughly $23-33/ton of CO2) and stabilizing atmospheric carbon at 450 or 550 ppm justified the investment in IGCC; other assumptions did not. Reinelt et al. examined operating a coal plant or replacing it with PC or IGCC with and without CCS (without the possibility of PC retrofits) (11). Regulatory uncertainty chills new investment. We examine whether stringent pollution control would lead to preferring IGCC over PC, the effect of uncertainty concerning the timing and tightness of carbon emissions constraints, the effect of current technical uncertainties for IGCC, the effect of technical retrofit, and the differences in technology choice between a private company (using a high discount rate) and society (using a low discount rate).

The Technology Options for Coal Recognizing the need for new generation investment, the Energy Policy Act of 2005 provides incentives for construction of IGCC generation plants. Although there are several IGCC plants in operation, newer technologies have been developed (and continue to be developed in projects such as the U.S. FutureGen Initiative (12)) but not demonstrated commercially. Almost all current coal plants use a pulverized coal (PC) technology, grinding the coal into tiny particles, blowing it into a boiler, and generating steam, which turns a turbine. The best control technologies remove 98%, 90%, and more than 99% of the SO2, NOx, and particles, respectively. These plants could be fitted with an amine scrubber to remove 90% of the CO2 from the flue gas, but the capital cost increases 3432

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emissions (lb/kWh) NOx PM 0.0059 0.00011 0.00014 0.00019 0.00011 0.00014

0.076 0.00029 0.00018 0.0000099 0.000010 0.000012

Hg

CO2

electricity produced (billion kWh/yr)

7.6E-08 5.6E-09 7.3E-09 8.8E-08 6.4E-09 5.2E-09

1.8 1.8 0.25 1.9 2.1 0.25

3.1 3.0 2.3 3.6 3.5 3.1

and the net efficiency declines, since 30% more coal is required to maintain output; see Table 1. The IGCC technology partially burns coal, creating a stream of CO, H2, and CO2 (about 300 BTU/cubic foot). Impurities such as sulfur are removed before the gas is combusted to produce electricity in a combined cycle system. The IECM software does not currently provide an option to add NOx or mercury controls to the IGCC system. For the IGCC system to meet the same NOx emissions standards as the PC system (i.e., 95% removal), an SCR unit operating at 50% removal efficiency was added to the system (outside the model). The mercury control was assumed to attain the same level of removal as the PC system using activated carbon in the IGCC system (at similar cost to the PC system). Both technologies offer effective pollution control and removal of 90% of the CO2. When this technology is included, the IGCC plant becomes the slightly more efficient and lower cost option, as shown in Table 2. The attractiveness of building an IGCC plant is limited by uncertainty concerning the performance and reliability of the technology, since it is new (see ref 7). Control measures decrease efficiency, requiring more coal and resulting in more SO2 emissions. We estimate the levelized cost of electricity (COE) from each plant as the sum of capital costs, operations, and maintenance and the cost of the pollution emissions over its assumed operating life. The PC system is a supercritical plant with higher efficiency than a subcritical plant (used in most analysis) with little cost increase. The IGCC system uses a GE (formerly Texaco) gasifier; the system minimizes cost at the expense of efficiency. Other configurations of the GE gasifier (or other gasification technologies) could be more efficient but less competitive economically. A higher quality coal, Pittsburgh # 8, is relatively more helpful for the IGCC plant (e.g., the IGCC baseline run increases from 34% efficiency using Illinois coal no. 6 to 37% using Pittsburgh coal no. 8). Lower ranked coals have a relatively greater penalty for the IGCC plant (13).

Results: 1. Can Increased Stringency of Pollution Regulations Justify the Use of IGCC? We create a pollution emissions index with a value of 100 for current standards, measured by the current prices for emissions allowances, the estimated social benefit of reducing particulate matter emissions, and the EPA estimate of the social benefit of reducing mercury emissions. When the index number is 50 or 200, the amounts charged for emissions are

FIGURE 1. Change in the levelized cost of electricity using different generation technologies and environmental controls. FIGURE 3. Change in discounted total plant cost ($/kW-net) with change in introduction of carbon tax of $0/ton, $29/ton, $50/ton, and $100/ton of CO2.

FIGURE 2. Total cost of electricity as the carbon tax changes. halved or doubled, respectively. As shown in Figure 1, the cost of electricity is not changed appreciably for the “controlled” plants as the pollution index goes from 0 to 200, since the plants are so tightly controlled that emissions are small. In contrast, the costs of an uncontrolled pulverized coal plant rise rapidly as the pollution index is increased. At a pollution index above 20 (the “crossover” point), stringent emissions control technologies should be added. The figure also shows that the costs of the PC and IGCC systems are similar. The costs of the two systems converge slightly, since the PC has slightly higher PM emissions. For a Pollution Index greater than 50, the IGCC plant with full controls is cheaper than the baseline IGCC plant. Within the limits of the IECM model, emissions standards do not favor IGCC over PC. Hereafter, we assume that current emissions constraints apply (an index of 100). See the Supporting Information for further details.

Results 2: What Carbon Tax Justifies the IGCC? Few people agree on the date and stringency of carbon regulation in the U.S. We represent stringency as a penalty for emitting a ton of CO2, ranging from 0 to $100 per ton of CO2 (equivalent to $367 per ton of carbon). Figure 2 shows the cost of electricity for both technologies with and without CCS (assumed to remove 90% of CO2). If a company were committed to build an IGCC plant, a tax greater than $20/ton ($22/tonne) of CO2 favors the IGCC system with CCS. If they were committed to a PC system, the carbon price would have to be $46 per ton (the crossover point) or more to justify adding CCS. If they are simply looking for the cheapest generation, they would choose a PC without CCS for a CO2 tax less than $29/ton and an IGCC system with CCS for a higher tax. At the current price of $10-$15 per ton

FIGURE 4. Cost of electricity ($/kWh) with change in introduction of carbon tax of $0/ton, $29/ton, $50/ton, and $100/ton of CO2. (currently discussed by companies and regulators in the U.S. as well as roughly the price of CO2 being trading currently in the E.U.), companies generating electricity from coal would simply pay the tax. Unless the tax were at least $29 per ton, companies would continue to use PC plants. The timing of a carbon tax is important, as in Figure 3 for IGCC. The vertical axis is the present discounted cost of electricity capacity; the lower the cost, the better. The horizontal axis is the number of years between when the plant is built and when the carbon tax is imposed (we assume the tax continues after that). In this analysis, there is no option to add a carbon capture technology after the plant is built. Figure 3 shows that delaying the tax until year 30, when the plant is shut, is equivalent to not imposing the tax: To the basic IGCC plant, we impose a CO2 tax of 0, $29, $50, or $100 per ton. If a tax of $29 is applied in year 0, the cheapest plant is IGCC with CCS. Figure 4 shows the same trend, using the cost of electricity (using a weighted average of discount rates) instead of the total discounted plant cost. For tax levels of $29, $50, and $100, the plant’s owner would have to expect that tax would be applied before year 6, 10, or 16, respectively, to warrant building the plant with CCS. If the tax is imposed later, the owner would build the plant without CCS and pay the tax when it is imposed. Discounting at 10% per year makes later tax imposition less costly; for example, the present discounted cost of a $100/ton tax in the 29th year to $1.70/ ton in year 0. (Note that the crossover points would be slightly VOL. 41, NO. 10, 2007 / ENVIRONMENTAL SCIENCE & TECHNOLOGY

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TABLE 3. Summary of Costs, Emissions, and Electricity Produced for Each of the Options Considereda before carbon tax

PC controlled PC w/CCS PC w/CCS retrofit PC w/CCS retrofit w/preinvestment IGCC IGCC w/CCS IGCC w/CCS retrofit IGCC w/CCS retrofit w/ preinvestment a

CO2 emissions (lb/kWh) 1.8 0.25 1.8 1.8 2.1 0.25 2.1 2.1

after carbon tax

cost ($/kWh)

electricity produced (kWh/yr)

CO2 emissions (lb/kWh)

cost ($/kWh)

electricity produced (kWh/yr)

0.051 0.087 0.051 0.052 0.055 0.074 0.055 0.059

3.0E+09 2.3E+09 3.0E+09 3.0E+09 3.5E+09 3.2E+09 3.5E+09 3.5E+09

1.8 0.25 0.25 0.25 2.10 0.25 0.25 0.25

0.051 0.087 0.105 0.089 0.055 0.074 0.089 0.078

3.0E+09 2.3E+09 2.3E+09 2.3E+09 3.5E+09 3.2E+09 2.9E+09 3.5E+09

With and without a carbon tax of $100/ton of CO2.

later if the IGCC plant with CCS were charged the same tax as the plant without CCS, but the differences are small.) A carbon tax of $50/ton or $100/ton raises the cost of electricity from an IGCC without CCS from $3.8/MW-net to $7.4 or $11/kW-net, respectively (if the tax is imposed in year 0).

Results 3: What Can Be Done To Minimize the Impact of Uncertain Carbon Legislation? Preinvestment can lower the cost of building a power plant today that would have to be retrofitted with CCS. The idea of a “Capture Ready” plant can mean many things (6): 1. identification of sequestration site, 2. allocate space for equipment at various levels, 3. install and run shift reactors (partially or fully), 4. size for IGCC w/CCS, 5. capture CO2 but do not sequester, or 6. some combination of these activities. The following analysis considers 4 technology options: 1. an IGCC system without CCS, 2. an IGCC system designed and built with CCS, 3. a system that is built to run as an IGCC plant optimized without carbon capture (same as option 1) and is then retrofitted to have CCS when a carbon tax is implemented, and 4. a system built to run as an IGCC plant without carbon capture but preinvestment has been made in order to prepare adding the CCS equipment when the carbon tax is implemented. The last option is designed to minimize the costs associated with the transition when the carbon tax is imposed as well as maintaining the same electricity output, despite the CCS energy penalty. The preinvestment includes allocating space for the future CCS equipment. The composition of the syngas changes when CO2 is removed which means that the flow rate and heat content of the syngas entering the gas turbine also changes. In order to compensate for these changes, a larger gasifier is added when the carbon tax is imposed in the fourth option. The original gasifier could either be sold or used as an additional train. This larger gasifier will process more coal, producing more syngas. The size is determined by matching the BTU content of the syngas and the volumetric flow rate. Four similar PC scenarios are also considered. Please see the Supporting Information for further details. The penalty associated with building a plant without CCS and then retrofitting it later is uncertain. Experience with the retrofit of other emission control technology might help to inform this assessment (14). The efficiency of the plant is assumed to be identical to a plant where CCS was built in initially. We treat the capital cost of a retrofit parametrically, examining retrofit penalties of 0%, 20%, and 50% (of the total plant cost) for the PC and IGCC plants. Figure 5 assumes that the penalty associated with retrofitting the CCS is 20% for both the PC and the IGCC plants. If the retrofit penalty were zero, a PC plant is the most attractive option, unless the CO2 tax is imposed before year 14. A 50% retrofit penalty lowers the likelihood a plant will be retrofitted but raises the 3434

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attractiveness of installing CCS initially: IGCC with CCS is the best technology for a tax that is applied before year 7 (instead of year 3 with a 20% penalty). If the tax is applied in years 7-13 (rather than 3-8), IGCC with preinvestment and then CCS is the best strategy. When the tax is applied after year 13 (rather than 15), PC with retrofit is the best choice. Note: the results presented in Table 3 differ slightly from those presented in Table 2 due to the fact that Table 3 includes the cost associated with the conventional pollutants emitted for each scenario. Decreasing the CO2 tax from $100/ton to $50/ton moves backward the years when IGCC with CCS dominates, but, like raising the retrofit penalty to 50%, there are no qualitative changes in the decisions.

The Social Choice No nation is likely to go from a carbon tax of 0 to one of $50 or $100 per ton, although EU prices will likely rise over time. We chose the tax levels for exploration, rather than to represent our best forecast. Until the tax crossed the $29 point, the cheapest generation would be PC with no CCS. Only after that point is there pressure to build CCS or go to an IGCC plant with CCS. We focus on the best actions that plant owners can take, given the uncertainty. Figure 5 shows the optimal action for a private company facing a cost of capital of 10% per year. Figure 6 shows the optimal action for society, based on a capital cost of only 3% per year. Not surprisingly, the difference in discount rates leads to different decisions; we examine the social cost of these differences If a CO2 tax of $100/ton were imposed in year 0 or year 1, the optimal technology would be the same using either the private or public cost of capital, as shown in Table 4. Thus, no policy intervention would be needed. If the tax were imposed in years 2-10, the company would select a PC with retrofit and preinvestment, while the public would prefer an IGCC with retrofit and preinvestment. Because the company selected the “wrong” technology, society would have to pay $0.011/kWh-net more. Similarly, in years 11-15, the company would select a PC with retrofit and preinvestment, while the public would prefer an IGCC with retrofit and preinvestment, costing society $0.0085/kWh. In years 16-25, the company would prefer a PC with retrofit, while society would add preinvestment. The social loss would be $0.010/kWh. If the tax were not imposed until after year 25, both the company and society would select the same technology. Thus, if society knew today that we were going to impose a $100/ton tax in year 10, we should either offer to subsidize an IGCC with retrofit and preinvestment or impose a tax on a PC with retrofit and preinvestment (as well as technologies other than the preferred one).

FIGURE 5. Change in cost of electricity ($/kWh) with change in introduction of carbon tax of $100/ton of CO2 with the consideration of retrofits (10% discount rate).

FIGURE 6. Change in cost of electricity ($/kWh) with change in introduction of carbon tax of $100/ton of CO2 with the consideration of retrofits (3% discount rate).

TABLE 4. Differences between Private and Public Choices at Several Time Periods year carbon tax is imposed

private decision

public decision

25

IGCC w/CCS IGCC w/CCS PC w/retrofit and preinvestment PC w/retrofit and preinvestment PC w/retrofit

30

PC

IGCC w/CCS IGCC w/CCS IGCC w/retrofit and preinvestment IGCC w/retrofit and preinvestment PC w/retrofit and preinvestment PC

1 10 15

regret ($/kWh) 0 0 0.011 0.0085

IGCC plant were coal type (Illinois #6 or Pittsburgh #8), coal price ($27-$50/ton), atmospheric pressure (12-15 psia), capacity factor (65-85%), gasifier temperature (2350 -2550 F), and whether additional trains are included (0, 1, or 2). As expected, reasonable differences in the assumptions and IECM costs and performance lead to a broad range of crossover points. Before spending billions of dollars on a new PC or IGCC plant, we recommend that the decision makers using this analysis explore their best judgments about the costs and performance of the available technologies. Please see the Supporting Information for further details.

0.010 0

Uncertainty The estimates made in this analysis are uncertain. The IECM software was used to conduct sensitivity analyses for the PC and IGCC plants. The variables considered for the PC plant were coal type (a range of bituminous coals), coal price ($27-$50/ton), and capacity factor (70-80%). Atmospheric pressures from 12 to 15 psia were also considered, since they affect efficiency. However, the range in pressures changed plant costs less than 1%. The variables considered for the

Discussion The analysis assumes the accuracy of the technologies as modeled in IECM. The costs of actual plants are likely to differ. The precise results shown are subject to uncertainty. To help an investment decision, the parameters for that plant and its fuel are needed, together with expectations about future carbon regulation. The following insights are drawn from this analysis: 1. Tighter SO2, NOx, PM, and Hg emission standards would not favor a controlled IGCC system over a PC system. 2. If a carbon tax were imposed before a coal burning, electricity generation plant were built, the tax would have to be at least $29/ton of CO2 before the company would VOL. 41, NO. 10, 2007 / ENVIRONMENTAL SCIENCE & TECHNOLOGY

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decide to add CCS and would choose an IGCC plant. For a lower tax, they would build a PC plant and pay the tax. With no current tax on carbon, a decision-maker would have to expect a sharp increase in the tax over the lifetime of a new plant before he/she would invest in a carbon capture plant. 3. If a company is committed to building an IGCC plant, despite its higher cost, and a CO2 tax greater than $20/ton was imposed before the plant was built, CCS should be added. 4. More generally, a CO2 tax less than $29/ton would not change the choice of technology: PC without CCS would produce the lowest cost electricity. 5. The earlier a decisionmaker believes the carbon tax will be imposed and the higher the tax, the more likely he/she will build IGCC w/CCS. 6. High discount rates make building an IGCC w/CCS less likely. 7. The option to retrofit becomes more important with higher carbon tax and lower retrofit penalty. A low retrofit penalty leads to delaying the installation of CCS until the CO2 tax is imposed, while a high retrofit penalty motivates initial CCS installation. 8. Current assessment of “capture ready preinvestment” makes only a small difference in this analysis, but further options for preinvestment should be investigated. 9. If companies make their decisions using a 10% discount rate and society bases its decisions on a 3% discount rate, there will be significant conflicts between public and private decisions. Having government announce the date and level of a carbon tax would promote more sensible decisions, but government would have to use a tax or subsidy to close the gap between decisions made on a 3% versus 10% discount rate. 10. Current uncertainty concerning the costs and reliability of IGCC and the carbon capture technologies as well as the date and stringency of carbon emissions constraints make investors reluctant to build any new coal technology today. Both power producers and society would gain from resolving uncertainties on the timing and level of a carbon tax and by clarifying the cost and reliability of alternative technologies.

Acknowledgments This research was made possible through support from the Climate Decision Making Center (CDMC) located in the Department of Engineering and Public Policy at Carnegie Mellon University. This Center has been created through a cooperative agreement between the National Science Foundation (SES-0345798) and Carnegie Mellon University. The authors thank Mike Berkenpas, Granger Morgan, Jay Apt, and the reviewers for their helpful insights.

Supporting Information Available Additional text, tables, and figures. This material is available free of charge via the Internet at http://pubs.acs.org.

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Literature Cited (1) Braine, B. H.; Mudd, M. J. Integrated Gasification Combined Cycle Technology. An American Electric Power Service Corporation White Paper. May 5, 2005. (2) TXU Corp. News Release. KKR, TPG and TXU Corp. Announce IGCC Plans. Available at http://www.txucorp.com/media/ newsrel/detail.aspx?prid=1028 (accessed 03/07). (3) Center for Energy and Environmental Studies. Integrated Environmental Control Model v. 5.02; 2005. http://www.iecmonline.com/ (accessed February, 2006). (4) Rubin, E. S.; Rao, A. B.; Chen, C. Comparative Assessments of Fossil Fuel Power Plants with CO2 Capture and Storage, Proceedings of 7th International Conference on Greenhouse Gas Control Technologies (GHGT-7), Vancouver, Canada, September 5-9, 2004. Rubin, E. S., Keith, D. W., Gilboy, C. F., Eds.; Elsevier; 2005; Vol. 1: Peer-Reviewed Papers and Overviews. (5) Booras, G.; Holt, N. EPRI. Pulverized Coal and IGCC Plant Cost and Performance Estimates. Gasification Technologies; Washington, DC, October 3-6, 2004. (6) Sekar, R. C.; Parsons, J. E.; Herzog, H. J.; and Jacoby, H. D. Future carbon regulations and current investments in alternative coal-fired power plant technologies. Energy Policy In press. (7) Stephens, J. C. Coupling CO2 Capture and Storage with Coal Gasification: Defining “Sequestration-Ready” IGCC, Fourth Annual Conference on Carbon Capture and Sequestration DOE/ NETL, May 2-5, 2005. (8) Simbeck, D. R.; McDonald, M. Existing Coal Power Plant Retrofit CO2 Control Options Analysis, From 5th Greenhouse Gas Control Technologies Conference, 2000. (9) Holt, N.; Booras, G. Phase Construction of IGCC Plants for CO2 Capture - Effect of Pre-Investment: Low Cost IGCC Plant Design for CO2 Capture; Electric Power Research Institute: December, 2003. (10) Rutowski, M. D.; Schoff, R. L.; Holt, N. A. H.; Booras, G. PreInvestment of IGCC for CO2 Capture with the Potential for Hydrogen Co-Production. Gasification, Technologies 2003, San Francisco, CA, October 12-15, 2003. (11) Reinelt, P.; Keith, D. Investment in U.S. Power Generation Facilities under Regulation and Natural Gas Price Uncertainty: Timing of Plant Retirement and New Technology Choice. Submitted to The Energy Journal. (12) U.S. Department of Energy. FutureGen Initiative. Available at http://www.fossil.energy.gov/programs/powersystems/futuregen/ (accessed 02/07). (13) Holt, N.; Booras, G.; Todd, D. A Summary of Recent IGCC Studies of CO2 Capture for Sequestration, Proceedings from The Gasification Technologies Conference. San Francisco, CA, October, 12-15, 2003. (14) Rubin, E. S.; Yeh, S.; Antes, M.; and Davison, J. Use of Experience Curves to Estimate the Future Cost of Power Plants with CO2 Capture. Int. J. Greenhouse Gas Control forthcoming in 2007.

Received for review September 14, 2006. Revised manuscript received February 2, 2007. Accepted February 26, 2007. ES062198E