Effects of Cold Temperature and Main March 27, 2017 Intercooling on Recuperator and Recompression Cycle Performance Nathan T. Weiland, Charles W. White, Andrew C. O’Connell nd 2 European Supercritical CO2 Conference, 30-31 August, 2018

Solutions for Today | Options for Tomorrow U.S. DOE Fossil Energy sCO2 Technology Program NETL: The DOE Fossil Energy Laboratory

• NETL is managing/coordinating two Fossil Energy (FE) sCO2 technology programs: • FE Base sCO2 Technology Program (indirectly & directly heated cycles for FE applications) • DOE sCO2 Crosscut Initiative (STEP – indirectly heated sCO2 Brayton cycle)

• FE Base sCO2 Technology Program • Development of individual cycle components • Systems analyses • Specific interest in adv. indirect cycle & IGCC direct cycle • Near term application to natural gas

• DOE sCO2 Crosscut Initiative (STEP) • Collaboration between DOE Offices (Fossil, Nuclear, Renewable) • Mission: Address technical issues, reduce risks, and mature technology • Objective/goal: Design, build, and test 10 MWe pilot facility (STEP) • FE/NETL designated as lead budget focal for STEP

2 NETL Research & Innovation Center (RIC)

Role in Supercritical CO2 Technology Program

Goal – Develop technology toward achieving the program goal of increased efficiency using sCO2-based power cycles. Approach – Perform R&D on turbine blade cooling, oxy-combustion, and materials, along with systems studies.

Aerothermal/ Oxy-combustion Materials Systems Analyses PI: Jim Black PI: Peter Strakey PI: Omer Dogan PIs: Weiland, Shelton, Liese Cool turbine blades to allow Improve efficiency using higher Evaluate material corrosion, Steady-state and dynamic higher turbine inlet temperature direct-fired cycle erosion, mechanical property modeling, techno-economic temperatures. with oxy-combustion. degradation in sCO2. Identify evaluations of various materials compatible in sCO2. configurations of sCO2 power cycle plants (direct- and indirect-fired cycles)

Proposed Oxy-Fuel Combustor Source: NETL

Source: NETL Source: NETL Source: NETL

3 Background 1 Utility-Scale Indirect sCO2 Plant Study

CO2 Compression, Drying, CO2 • Objective: Establish cost and 3 Vent and Purification Unit Product CO CO2 29 2 Purification Drying 30 Ambient Air 27 performance baselines for LP CO2 1 MAC 2 Cryogenic ASU Compressor w/ Compression/ Pumping commercial-scale indirect sCO2 Intercooling Interstage O Knockout power plants with carbon capture Interstage Cooling 2 28 Knockout Water 4 and storage (CCS) 26

5 6 • Early work shows that the narrow 22 N Heater 2 21 18 temperature addition window of a 17 19 ID 20 8 24 GAS FD Fan COOLER 10 Knockout recompression sCO2 Brayton Cycle Bag Water 15 House restricts selection 41 16 PA Fan Fly Ash Oxy- 7 23 9 42 • Modified oxy-fired, atmospheric pressure Circulating 46 Fluidized Bed MAIN CO Coal 11 Combustor 2 CFB with CCS chosen for analysis COMPRESSOR Limestone 12 31 45 HIGH LOW 40 39 TEMPERATURE 44 TEMPERATURE 34 CO • Recompression cycle with reheat and/or 2 RECUPERATOR 33 RECUPERATOR 36 TURBINE 35 main compressor intercooling 32 CO2 14 COOLER (4 combinations x 2 temperatures) Note: Block Flow Diagram is not intended to 38 represent a complete process. Only major Bottom

process streams and equipment are shown. Ash Bypass CO2 Compressor

Source: NETL 37 1 National Energy Technology Laboratory (NETL), "Techno-economic Evaluation of Utility-Scale Power Plants Based on the Indirect sCO2 Brayton Cycle," DOE/NETL- 2017/1836, Pittsburgh, PA, September 2017.. 4 Utility-Scale Indirect sCO2 Plant Study Summary of Overall Plant HHV Efficiencies1

• Relative to the steam Rankine cycles 42 40,8 41,2 using oxy-fired CFBs and CCS: 39,9 40 39,5 • At 620 °C, sCO2 cycles are 1.1 – 3.2 Source: NETL percentage points higher in efficiency 38 36,9 36,8 • At 760 °C, sCO2 cycles are 2.6 – 4.3 36 36,2 35,3 percentage points higher 34 34,7 33,6 • 32 The addition of reheat improves sCO2 Plant (HHV Efficiency %) 760 °C 620 °C cycle efficiency by 1.3 – 1.5 percentage 30 points Rankine Base IC Reheat Reheat+IC • The addition of main compressor Power Summary (MW) B22F Base IC Reheat Reheat+IC intercooling (IC) improves efficiency Coal Thermal Input 1,635 1,586 1,557 1,519 1,494 sCO2 Turbine Power 721 1,006 933 980 913 by 0.4 – 0.6 percentage points CO2 Main Compressor 160 154 148 142 • Main compressor intercooling reduces CO2 Bypass Compressor 124 60 117 58 Net sCO2 Cycle Power 721 711 708 704 702 compressor power requirements for both the Air Separation Unit 85 83 81 79 78 main and bypass Carbon Purification Unit 60 56 55 54 53 Total Auxiliaries, MWe 171 161 158 154 152 Net Power, MWe 550 550 550 550 550

5 sCO2 Compression Power

• sCO2 compression power requirements 120 100-120 are very sensitive to the proximity of the RC - Base 80-100 operating condition to the CO2 critical 100 60-80 point (Tcr = 31 °C, Pcr = 7.37 Mpa) 40-60 80 RC – with MC 20-40 • Main compressor intercooling reduces Intercooling 0-20 the bypass compressor inlet temperature 60 • Condensing sCO cycles can significantly 2 40 Pressure Ratio = 4 reduce compression power requirements ηc = 85% • Reducing compression power improves 20 MC cycle efficiency and specific power Condensing Specific Compression Power (kJ/kg) Power Compression Specific 0 Cycles 10090 80 MC RC 70 60 50 LTR HTR Heater 40 10 Cooler 30 8 9 20 6 7 105 Turb Source: NETL Source: NETL

6 Main Compressor Intercooling Effects Background 10.5 MW 11.4 MW No Intercooling 9.2 MW 8.0 MW With Intercooling 100 MW • The incorporation of main compressor 100 MW intercooling improves the specific power MC RC 1 238 C 474 C of a recompression cycle 85 C 30% 189 C 460 C 53 C 28% LTR HTR PHX • Reduces sCO2 mass flow 35 C Cooler 700 C • Reduces required cycle size and cost 35 C 700 C T 95 C 248 C 517 C 63.6 MW 108 MW • The effects of intercooling on cycle 47.6 MW 63 C 199 C 517 C 74.4 MW 58.5 MW 120 MW efficiency are complex, and require 33.7 MW 70.0 MW consideration of temperature distributions 700 along the recuperator train 600 No Intercooling 500 With Intercooling C) • A single stage of intercooling for the main ° CO2 Dome compressor offered both higher overall plant 400 efficiency (0.4 – 0.6 percentage points) and lowers 300 1 the cost of electricity by 1.8 to 2.7% 200 Temperature ( Temperature • Efficiency benefit increases (0.6 – 1.6 percentage 100 points) when the pressure ratio between 0 intercooled main compressor stages is optimized2 1 1,5 2 2,5 3 Specific Entropy (kJ/kg K) Source: NETL 1 National Energy Technology Laboratory (NETL), "Techno-economic Evaluation of Utility-Scale Power Plants Based on the Indirect sCO2 Brayton Cycle," DOE/NETL- 2017/1836, Pittsburgh, PA, September 2017. 2 Y. Ma, M. Liu, J. Yan and J. Liu, "Thermodynamic study of main compression intercooling effects on supercritical CO2 recompression Brayton cycle," 7 Energy, vol. 140, pp. 746-756, 2017. sCO2 Cooling Integration Study

• Objective: Determine the extent to which increasing cooling capacity and cooling system operation conditions can improve the efficiency and cost of electricity (COE) from a utility-scale indirect sCO2 power plant. • Approach • Determine steady state plant performance as a function of cooler exit temperature and pressure, as well as the number of main compressor intercooling stages • Novel options for resolution of resulting temperature pinch point problems • Quantify impact on plant efficiency, specific power and other cycle parameters for condensing and non-condensing CO2 cycle operation • Develop cost and performance models of wet and dry cooling technologies • Optimize plant COE as a function of cooling technology and capacity • Expected Impacts • Cooling system optimization results are applicable to all sCO2 plant types • Published cooler cost and performance modeling tools will enable similar COE optimization by others

• Enables COE optimization at any sCO2 plant site given its ambient conditions

8 sCO2 Recompression Brayton Cycle (sRBC) General Cycle Design

• Cycle design features from previous work1: CFB • Circulating Fluidized Bed (CFB) coal combustor FGC HPT • Reheat turbine MC • Third recuperator stage (VTR) and an that LPT supplements the HTR

• Intercooled main CO2 compressor RC VTR

• Flue gas cooler (FGC) in parallel with the LTR LTR HTR • Transfers additional thermal energy from the low quality Cooler combustion flue gas to the sCO2 cycle • Applicable to recovery sCO2 cycles • Present work focuses on low temperature components only • Other cycle components are only analyzed to establish a baseline plant efficiency for evaluation of parameter sensitivities • Results generally apply to other hot-side cycle configurations and heat sources

Source: NETL 1 National Energy Technology Laboratory (NETL), "Techno-economic Evaluation of Utility-Scale Power Plants Based on the Indirect sCO2 Brayton Cycle," DOE/NETL- 2017/1836, Pittsburgh, PA, September 2017.. 9 sRBC Power Cycle Analysis Methodology

CFB • When used, the main CO2 compressor is assumed to have a single stage of intercooling: FGC HPT

• Intercooler outlet temperature is set equal to the MC LPT main CO2 cooler outlet temperature • Intercooler pressure drop is 0.014 MPa (2 psid) • Isentropic efficiencies and pressure ratios for each RC VTR compression stage are approximately equal LTR HTR • Recuperator exit temperatures are set using Cooler design specifications in the Aspen Plus model • Target a minimum temperature approach (Tapp) of Source: NETL 5.6 °C (10 °F) at one or both ends of the LTR

• Similar design specifications are applied to the flue gas and CO2 coolers. • Second law validation of the heat integration scheme is accomplished from a pinch analysis performed on each heat exchanger

10 sRBC Power Cycle Assumptions and Operating Point

• All sCO2 cycle analyses performed using the Major assumptions and specifications Span-Wagner Equation of State via REFPROP applied to the sRBC cycle analysis • Design variables adjusted in sensitivity analyses: Parameter Value Turbine inlet temperature (°C) 760 • CO cooler exit temperatures (T ) of 20, 25, 30, 35 and 2 cooler Compressor outlet pressure (MPa) 34.6 40 °C Intercooler pressure drop (MPa) 0.014 Results for T = 30 °C will be the least accurate due • cooler Turbine exit pressure (MPa) 7.9 proximity to the CO critical temperature of 31 °C 2 Nominal compressor pressure ratio 3.8 • Main compressor inlet pressure Turbine isentropic efficiency 0.927 • Number of main compressor intercooler stages Compressor isentropic efficiency 0.85 • Effect of intercooler pressure drop on plant Cycle pressure drop (MPa) 0.41 Minimum temperature approach (°C) 5.6 performance (0.14 – 1.4 bar) showed no significant difference the when a single stage of intercooling was used

11 Effects of Main Compressor Inlet Conditions Results 45 Tcooler = 20°C • Sensitivity analysis was performed on the 44 Tcooler = 25°C Tcooler = 30°C process efficiency vs compressor inlet pressure 43 Tcooler = 35°C Tcooler = 40°C (CIP) for each Tcooler examined 42 • For each Tcooler process efficiency shows a maximum at a particular CIP 41 40 Process (% Efficiency HHV) • For Tcooler below the critical temperature, the 39 plant efficiency is particularly sensitive as the 5 6 7 8 9 10 CIP falls below its optimal value Main Compressor Inlet Pressure (MPa) 10 • Actual compressor inlet pressure used was 0.069 Mpa Optimal CIP (10 psi) greater than the calculated optimal CIP 9 Saturation line Pseudo-critical line • Optimal CIP for any CO2 Tcooler is slightly 8 higher than the saturation pressure or pseudo- 7 Pressure (MPa) critical pressure 6 • Consistent with other results in literature3 5 20 25 30 35 40 Source: NETL Cooler Temperature, Tcooler (°C) 3 S. R. Pidaparti, P. J. Hruska, A. Moisseytsev, J. J. Sienicki and D. Ranjan, "Technical and Economic Feasibility of Dry Air Cooling for the Supercritical CO2 Brayton Cycle Using Existing Technology," in The 5th International Symposium - Supercritical CO2 Power Cycles, San Antonio, Texas, 2016. 12 Effects of Main Compressor Inlet Conditions Results, Cont’d

• Preliminary analysis shows that a reduction in main compressor inlet temperature from 40 °C to 20 °C yields a 35% increase in plant specific power = • Equivalent to 26% reduction in cycle mass flow, which may 𝑁𝑁𝑁𝑁𝑁𝑁 𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐 𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝 𝑜𝑜𝑜𝑜𝑜𝑜𝑜𝑜𝑜𝑜𝑜𝑜 𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆 𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃 reduce the capital cost of the sCO2 power cycle One stage of intercooling𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇 and𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚 optimal𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓 CIP • Alternatively, lower mass flow can reduce heat exchanger 250 pressure drops to improve efficiency 240 • Specific power improvement 230 220 is due to reduced compression 210 power requirements with 200 increases in sCO2 density at 190 Specific Power (kJ/kg) lower temperatures 180 170 • Lower sCO2 temperatures yield 20 25 30 35 40 internal temperature pinch Cooler Temperature (°C) problems in heat exchangers Source: NETL 13 Flue Gas Cooler Correction of Low Temperature Anomalies

• The flue gas exiting the oxy-CFB has a higher moisture content (20.1%) than that for a conventional air-fired CFB due to flue gas recycle for CFB temperature control • Compression without intercooling generally yields a feasible flue gas cooler design • A temperature cross due to water condensation occurs in the flue gas cooler with: • Tcooler ≤ 25 °C for compression without intercooling • The addition of a single intercooler stage for all Tcooler values studied • To correct the internal pinch point, the hot side (flue gas) exit temperature is limited to its dew point • Consistent with power plant practice to avoid corrosion of downstream flue gas equipment

• Achieved by reducing the mass flow rate of the cold sCO2 to the flue gas cooler, reducing the recoverable heat from this heat exchanger • Alternatively, the flue gas could be allowed to partially condense up to the point where the minimum Tapp was achieved Source: NETL 14 Flue Gas Cooler Correction to Internal Pinch Point

• Original Model included • Introduction of the design • Boiler efficiency = heat transferred condensation and an internal flue correction lowers the process to the cycle / fuel thermal input efficiency by 0-1% gas cooler pinch point • Original Model yields boiler • • FG Cooler Modification corrects Large efficiency increase with the efficiency increase as water is introduction of one intercooler condensed from the flue gas with the design to maintain the hot side stage, but low impact from decreasing cold sCO2 temperature temperature at or above Tdew additional stages • FG Cooler Modification fixes the • Plant efficiency for the corrected • No efficiency impact due to flue flue gas cold end temperature at its case is 0-2% lower than for the gas cooler correction with no dew point, so flue gas heat original, uncorrected sensitivity intercooling recovery remains constant 45analysis 42,2 97 Original Model 44 1 Intercooling Stage 42,0 Tcooler = 35 °C 96 FG Cooler Modification 41,8 43 41,6 95 1 Intercooling Stage 42 41,4 94 41 41,2 Original Model Original Model 40 93 FG Cooler Modification 41,0

FG Cooler Modification Boiler Efficiency (% HHV) Process Efficiency (% HHV)(% Process Efficiency Process Efficiency (% HHV)(% Process Efficiency 39 40,8 92 20 25 30 35 40 0 1 2 3 4 5 20 25 30 35 40 Cooler Temperature (°C) Number of Intercooling Stages Cooler Temperature (°C)Source: NETL 15 Low Temperature Recuperator Internal Temperature Profiles 260 240 T = 30 °C • 220 cooler LTR pinch analysis was conducted for all C) Tapproach = 5.6 °C ° 200 sensitivity variables with a fixed Tapproach of 180 160 5.6 °C enforced at both ends 140 120 Non-Intercooled, Cold • The addition of main compressor 100 Non-Intercooled, Hot LTR Temperature ( Temperature LTR 80 Intercooled, Cold intercooling leads to a significant internal 60 Intercooled, Hot 40 temperature pinch point within the LTR 0 200 400 600 800 • Temperature crosses occur for T = 35 & 40 °C Heat Transferred (MWth) cooler 12 C) ° 10

• Small internal approach temperature also T ( Δ occurs without main compressor intercooling 8 in some cases 6 4 20 C, 0 IC 20 C, 1 IC • Points to the need for internal LTR pinch 2 30 C, 0 IC 30 C, 1 IC analyses for all sCO2 systems studies 0 40 C, 0 IC LTR Temp. Differential, Differential, Temp. LTR 40 C, 1 IC -2 Source: NETL 0 200 400 600 800 Heat Transferred (MWth) 16 Low Temperature Recuperator Internal Temperature Pinch Correction Strategies

• Low approach temperatures lead to higher cycle efficiency, but also higher LTR cost due to the need for increased heat transfer surface area • Alternative temperature approach specification Cases are considered to avoid infeasible LTR situations: LTR Cold End, ΔTC LTR Hot End, ΔTH • Case 1: Temperature approach specification 14 C)

° Case 1 applied at both the hot and cold ends of the LTR ( 12 Tcooler = 30 °C • Case 2: LTR hot end and cold end temperature ΔT Case 2 approaches are increased equally until the internal 10 Case 3 Case 4 temperature approach attained the target Tapp 8 • Case 3: Hot end ΔT is set to the target value, and 6 cold end ΔT is adjusted until the internal minimum 4 T reached the target value T app 2 approach • Case 4: Hot end ΔT is set to the target value, and Differential, Temp. LTR target 0 cold end ΔT is adjusted until the average LTR Tapp equals the target value 0 100 200 300 400 500 600 700 Heat Transferred (MWth) Source: NETL 17 Low Temperature Recuperator Internal Temperature Pinch Correction Strategy Effectiveness

58,6% • Case 1 yields increased efficiency and specific power T = 30 ° C with main compressor intercooling, but results in an 58,4% cooler infeasible design due to the low internal temperature 58,2% 58,0% pinch 0 IC • The remaining strategies generally result in slightly 57,8% decreased cycle efficiency with main compressor 57,6% Case 1 Case 2 Cycle Efficiency 57,4% intercooling, though specific power increases in all Case 3 1 IC 57,2% 2 IC cases Case 4 57,0% • Case 3 is the preferred strategy, since the minimum 195 200 205 210 215 temperature approach is strictly adhered to throughout the LTR, while maintaining a higher Specific Power [kJ/kg] efficiency than the Case 2 strategy Case Key • The size and cost benefits of a 4% increase in specific power Case 1: ΔTH = ΔTC = Tapp; ΔTint < Tapp are expected to offset the slight reduction in efficiency, thus Case 2: ΔTH = ΔTC > Tapp; ΔTint = Tapp Case 3 is chosen for most of the remaining analyses Case 3: ΔTH = ΔTint = Tapp; ΔTC > Tapp • Accomplished by increasing the bypass fraction Case 4: ΔTH = ΔTavg = Tapp; ΔTC > Tapp Source: NETL 18 Low Temperature Recuperator Case 3 Correction to Internal Pinch Point 45 1 Intercooling Stage • Heat exchanger design corrections are 44 cumulative, thus the LTR Modification (gray 43 lines) results also includes the FG Cooler 42 Modification design changes (orange lines) 41 Original Model FG Cooler Modification 40

Process Efficiency (% HHV)(% Process Efficiency LTR Modification • The Case 3 correction to the LTR Tapproach 39 specification reduced the magnitude of the 20 25 30 35 40 Cooler Temperature (°C) process efficiency and specific power, but did not 250 change the qualitative trend 240 1 Intercooling Stage • The LTR Modification to correct the internal temperature 230 pinch reduces plant efficiency by about 0.2 - 0.4 percentage 220 points 210 200 Original Model • Net impact of the FG Cooler Modification was to lower the 190 FG Cooler Modification Specific Power (kJ/kg) Specific Power specific power 0-2% while the LTR Modification lowers the 180 LTR Modification specific power an additional 1-2% at a given Tcooler 170 20 25 30 35 40 Source: NETL Cooler Temperature (°C) 19 Low Temperature Recuperator Case 3 Correction to Internal Pinch Point, Cont’d 42,6 • Heat exchanger design corrections are 42,5 Tcooler = 30 ° C 42,4 cumulative, thus the LTR Modification (gray 42,3 lines) results also includes the FG Cooler 42,2 Modification design changes (orange lines) 42,1 • Applying the design corrections to the FG Cooler 42,0 FG Cooler Modification Process Efficiency (% HHV)(% Process Efficiency 41,9 LTR Modification and LTR renders the plant efficiency relatively 41,8 insensitive to main CO compressor intercooling 0 1 2 3 4 5 2 Number of Intercooling Stages • LTR Modification reduces the specific power 216 214 Tcooler = 30 ° C benefit when intercooling is used 212 • The most significant increase in specific power occurs with a 210 208 single stage of intercooling 206 • With a single stage of intercooling, specific power 204 202 improvements are higher as T increases (not shown) FG Cooler Modification cooler 200 Specific Power (kJ/kg) Specific Power LTR Modification • Tcooler = 20 °C: specific power increases about 2% 198 196 • Tcooler = 40 °C: specific power increases about 5% 0 1 2 3 4 5 Source: NETL Number of Intercooling Stages 20 Main CO2 Cooler Internal Temperature Pinch and its Correction

• For condensing sCO2 power cycles, an internal pinch point can occur in the sCO2 cooler • Under typical cooling water assumptions with a water inlet temperature of 15.6 °C (60 °F) and a range of 11.1 °C (20 °F): • For Tcooler = 25 °C, the CO2 cooler yields an internal pinch point (3.7 °C) where the CO2 begins to condense • For Tcooler = 20 °C, the proposed cooling system configuration is infeasible due to a temperature crossover • Correction Strategies: • Reduce the cooling water temperature range by increasing the water flow rate • Reduce the cooling water inlet temperature by altering the design

• Reduce the target minimum Tapp in the cooler • Each correction strategy has implications for cooling system design and cost • Further work under this study has developed cost and performance models for various cooling technologies, and identified the cooling system designs that leads to the lowest sCO2 plant COE Source: NETL 21 Summary and Conclusions Study Objectives

• Reducing the cold sCO2 temperature in the recompression cycle is shown to significantly improve plant efficiency and specific power • Increasing specific power reduces sCO2 cycle mass flow, and may reduce sCO2 cycle size and cost, and/or reduce heat exchanger pressure drops • To a lesser extent, main compressor intercooling also improves plant performance by reducing the temperature and flow to the recycle compressor • Intercooling is shown to cause internal temperature pinch problems in the low temperature recuperator • Several strategies for avoiding these problems are presented • Maintaining the LTR hot side approach temperature is essential for maintaining cycle performance • The bypass flow fraction can be increased slightly to reduce or eliminate the internal temperature pinch • The effect of water condensation in the flue gas cooler is considered • Applicable to fossil-fueled indirect sCO2 and waste heat recovery applications • Main compressor intercooling and colder sCO2 temperatures increase the likelihood of flue gas condensation in this heat exchanger, though this is dependent on the water content of the flue gas

• Finally, CO2 cooler temperature pinch point issues are considered for cases in which condensation of CO2 occurs • Further work under this study has developed cost and performance models for various cooling technologies, and identified the cooling system designs that lead to the lowest sCO2 plant COE

22 Other NETL sCO2 Systems Analyses 2017 - 2020

Steady State Techno-Economic Analyses Off-Design/Dynamic Cycle Analyses

1. Utility-scale Oxy-coal CFB with CCS 1. Development of Dynamic sCO2 Compressor and 2. Utility-scale Air-fired coal CFB without CCS Recuperator Models 3. Component Cost Correlations for Indirect sCO Power Cycles 2. Development of Control Strategies for 10 MW 2 2 4. Indirect sCO2 Heat Source Integration Study Recompression Brayton Cycle (STEP Plant) 5. Indirect sCO2 Bottoming Cycle Deployment in NGCCs 3. STEP Plant Dynamic Model Validation and Lessons 6. Indirect sCO2 Cooling System Optimization for Plant Site Conditions Learned 7. Scenario Analysis of Indirect sCO2 Market Deployment 4. Off-Design Modeling of Utility-scale Coal-Fired Indirect sCO Indirect sCO2 Plant 5. Variation of Indirect sCO2 Plant Performance and Economics with Ambient Conditions

2 1. Integrated Coal Gasification/Direct sCO2 Plant 1. Dynamic Model of a Direct-Fired sCO2 Cycle 2. Natural Gas-Fueled Direct sCO2 Plant with Incomplete Combustion 2. Off-Design Direct sCO2 Plant Model and Variation 3. Cooling System Integration & Optimization for Direct sCO2 Plants of Performance & Economics with Ambient 4. Cooled Direct sCO2 Turbine Model Development Conditions Direct sCO 5. High-Pressure ASU Model Development for Direct sCO2 Power Plants Blue: Completed Analyses Orange: Ongoing Analyses Green: Future Analyses

23 Questions? [email protected]

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