On/Off Operation of Carbon Capture Systems in the Dynamic Electric Grid On/Off Operation of Carbon Capture Systems in the Dynamic Electric Grid Rochelle Group Research Review January 11, 2008 Stuart Cohen Graduate Research Assistant Department of Mechanical Engineering: Thermal Fluid Systems Division The University of Texas at Austin

Outline Background and limitations of current techno-economic analyses of CCS My proposal to investigate CCS within the electric grid Illustration of grid dynamics and implications of on/off operation of CO 2 capture Summary of Research Objectives

Typical Techno-Economic Analyses take 2 forms: Bottom Up Approach: Plant Level Analysis Economic Indicators Cost of Electricity ($/MWh) CO 2 Removal Cost ($/tCO 2 ) Total Plant Cost ($/kW) Local Environmental Effect Plant CO 2 Emissions (ton) Static Plant Performance Specifications CO 2 Removal Efficiency, (%) Plant Output (MW) CO 2 Capture Energy (MWh/tCO 2 ) Economic Assumptions Equipment Costs ($) Fuel Costs ($) Discounting Rate (%)

Typical Techno-Economic Analyses take 2 forms: Top Down Approach: Macro-scale Energy Analysis National Electricity Market Trends Projected Population Growth Consumer Energy Use Behavior Input Parameters of Interest Cost of each Energy Technology ($/MWh) CO 2 Market Value ($), Date of Application, Growth Rate Effects on Energy Use US Energy Consumption US Energy Mix Market Penetration of CCS Global Environmental Effect US CO 2 Emissions (ton)

These Analyses have Several Strengths… Macro-scale Energy Analyses – Demonstrate qualitative long term effects – Demonstrate macroeconomic tradeoffs – Consider interactions between energy sources – Consider regional variation in energy use Single Plant Analyses – Detailed technology assessment – Demonstrate plant level tradeoffs

But Also Several Limitations Macro-scale Energy Analyses – Ignore dynamics of plant dispatch – Limited detail of plant performance Single Plant Analyses – Use static plant performance parameters – Site and technology specific – Ignore varying electricity demand – Do not consider interactions between energy supply technologies

Proposal Take an intermediate approach between single plant and macro-scale energy analyses Study the feasibility and effects of turning CO 2 capture systems on and off in response to electric grid dynamics Optimize the performance, economics, and environmental effects of turning CO 2 capture on and off under a given electricity supply/demand scenario

Grid Level Analysis Market Based Economic Indicators Cost of Electricity ($/MWh) CO 2 Removal Cost ($/tCO 2 ) Total Plant Cost, ($/kW) Environmental Effect CO 2 Emissions – Plant and Grid (ton) Variable Performance Specifications CO 2 Removal Efficiency (%) Plant Output (MW) Economic Assumptions Equipment Costs ($) Fuel Costs ($) Grid Parameters Electricity Demand (MW vs. Time) Dispatch Options and Costs ($/MWh) Market Value of CO 2 ($)

My Hypotheses Turning CO 2 capture on and off in response to grid supply/demand can lessen the cost of implementing CCS Optimal practices can be determined from grid supply/demand scenarios The flexibility of Post-Combustion capture using chemical absorption favors such practice

Electricity Demand throughout the Day Source: ERCOT Reliability/Resource Update 2006 Natural Gas Nuclear Coal Total Coal Capacity

Using On/Off CO 2 Capture During Peak Load Natural Gas Nuclear Coal Capture Turned Off 30% Coal Capacity Total Coal Capacity

Source: ERCOT January 2 August 17 Capture Turned Off

Source: ERCOT Capture Off Capture On January 2 August 17

Source: 2007 GE Wind Analysis for ERCOT Total Load Wind Generation Load minus Wind Capture Turned Off Hourly Variation in Wind and Load: 15000MW Wind in TX Scenario 30% Coal Capacity

Source: ERCOT Peak Load Capture Turned Off 30% Coal Capacity

Source: ERCOT and ICE

My Work Will Analyze the effects of on/off CO 2 capture operation under several electricity supply/demand scenarios Incorporate knowledge of amine absorption systems into grid level analysis of CO 2 capture Investigate technical limitations of on/off operation at a system level

Overall Research Goals Determine performance, economic, and environmental tradeoffs of on/off CO 2 capture Determine optimal operation of CO 2 capture for a given electricity supply/demand scenario Provide industry with a tool to help guide the implementation and use of CO 2 capture systems Determine technical feasibility of on/off CO 2 capture at the system level

Bottom Line CO 2 Capture is expensive, BUT Dynamic electricity supply/demand provides an opportunity for using on/off operation to lower CO 2 capture costs

Thank you. Questions? Comments?