On/Off Operation of On/Off Operation of Carbon Capture SystemsCarbon Capture Systems

in the Dynamic Electric Grid in the Dynamic Electric Grid

Rochelle Group Research ReviewJanuary 11, 2008

Stuart CohenGraduate Research Assistant

Department of Mechanical Engineering:Thermal Fluid Systems Division

The University of Texas at Austin

OutlineOutline

• 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 CO2 capture

• Summary of Research Objectives

Typical Techno-Economic Typical Techno-Economic Analyses take 2 forms:Analyses take 2 forms:

Bottom Up Approach: Plant Level Analysis

Economic Indicators• Cost of Electricity ($/MWh)• CO2 Removal Cost ($/tCO2)• Total Plant Cost ($/kW)

Local Environmental Effect• Plant CO2 Emissions (ton)

Static Plant Performance Specifications

• CO2 Removal Efficiency, (%)• Plant Output (MW)• CO2 Capture Energy (MWh/tCO2)

Economic Assumptions• Equipment Costs ($)• Fuel Costs ($)• Discounting Rate (%)

Typical Techno-Economic Typical Techno-Economic Analyses take 2 forms: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 ($/MWh)• CO2 Market Value ($), Date of Application, Growth Rate

Effects on Energy Use• US Energy Consumption• US Energy Mix• Market Penetration of CCS

Global Environmental Effect• US CO2 Emissions (ton)

These Analyses have Several These Analyses have Several Strengths…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 LimitationsBut 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

ProposalProposal

• Take an intermediate approach between single plant and macro-scale energy analyses

• Study the feasibility and effects of turning CO2 capture systems on and off in response to electric grid dynamics

• Optimize the performance, economics, and environmental effects of turning CO2 capture on and off under a given electricity supply/demand scenario

Grid Level AnalysisGrid Level Analysis

Market Based Economic Indicators

• Cost of Electricity ($/MWh)• CO2 Removal Cost ($/tCO2 )• Total Plant Cost, ($/kW)

Environmental Effect• CO2 Emissions – Plant and Grid (ton)

Variable Performance Specifications

• CO2 Removal Efficiency (%)• Plant Output (MW)

Economic Assumptions• Equipment Costs ($)• Fuel Costs ($)

Grid Parameters• Electricity Demand (MW vs. Time)• Dispatch Options and Costs ($/MWh)• Market Value of CO2 ($)

My HypothesesMy Hypotheses

• Turning CO2 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 Electricity Demand throughout the Daythroughout the Day

Source: ERCOT Reliability/Resource Update 2006

Natural Gas

Nuclear

Coal

Total Coal Capacity

Using On/Off COUsing On/Off CO22 Capture Capture During Peak LoadDuring Peak Load

Natural Gas

Nuclear

Coal

Capture Turned Off

30% Coal Capacity

Total Coal Capacity

Source: ERCOT

January 2

August 17

Capture Turned Off

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

CaptureTurned Off

30% Coal Capacity

Source: ERCOT and ICE

My Work WillMy Work Will

• Analyze the effects of on/off CO2 capture operation under several electricity supply/demand scenarios

• Incorporate knowledge of amine absorption systems into grid level analysis of CO2 capture

• Investigate technical limitations of on/off operation at a system level

Overall Research GoalsOverall Research Goals

• Determine performance, economic, and environmental tradeoffs of on/off CO2 capture

• Determine optimal operation of CO2 capture for a given electricity supply/demand scenario

• Provide industry with a tool to help guide the implementation and use of CO2 capture systems

• Determine technical feasibility of on/off CO2 capture at the system level

Bottom LineBottom Line

• CO2 Capture is expensive, BUT

• Dynamic electricity supply/demand provides an opportunity for using on/off operation to lower CO2 capture costs

Thank you. Thank you.

Questions? Comments?Questions? Comments?