Steven A. Wright*, Thomas M. Conboy, and Gary E. Rochau

2011 University Turbine Systems Research Workshop

October 25-27, 2011 Columbus, Ohio

Sandia National Laboratories

Advanced Nuclear Technology

505 845-3014, sawrigh@sandia.gov

505 845-3143, tmconbo@sandia.gov

505 845-7543, gerocha@sandia.gov

OVERVIEW OF SUPERCRITICAL CO2 POWER CYCLE

DEVELOPMENT

AT SANDIA NATIONAL LABORATORIES

Goals of Presentation

• What is a Supercritical CO2 Brayton Cycle?

• Benefits of S-CO2 Power Systems – Economic and Environmental

– All Heat Sources

• DOE-NE Gen-IV S-CO2 Research Program

• Applications List (Fossil, Solar, Nuclear)

• Scaling Study Results (10 MWe)

– 10 MWe Development and Demonstration Program Status of

Development Effort

– Commercial and Government

• Summary and Conclusions

What is a Supercritical CO2 Brayton Cycle?

How does it work?

Liquid like Densities with CO2

Very Small Systems,

High Efficiency due to Low Pumping Power

1

25

Compressor

CO2

= =

Motor Alternator Waste Heat

Gas Chiller

Turbine

=

3

4

6

Heater

1

25

Compressor

CO2

= =

Motor Alternator Waste Heat

Gas Chiller

Turbine

=

3

4

6

Heater Turbine

Rejects Heat

Above Critical Point

High Efficiency Non-Ideal Gas

Sufficiently High for Dry Cooling

High Efficiency at Lower Temp

(Due to Non-Ideal Gas Props)

High Density Means Very Small Power Conversion System

Non-Ideal Gas Means Higher Efficiency at Moderate Temperature

Cycle Efficiencies vs Source Temperature

for fixed component efficiency

0%

10%

20%

30%

40%

50%

60%

200 300 400 500 600 700 800 900 1000

Source Temperature (C)

Cy

cle

Eff

icie

nc

y (

%)

1t/1c rec He BraytonSCSF CO2 Brayton3t/6c IH&C He BraytonRankine cyclestoday's efficiency levels

Steam CO2

He

T 31 C (88 F)

S

Liq Vap

Critical Point

Critical Point

88 F / 31 C

1070 psia / 7.3 MPa

He Turbine

(300 MWe)

1 m

Steam Turbine (250 MWe)

S-CO2 (300 MWe)

60% Density of Water

20%

10%

Comp.

Steam

Condensor S-CO2

Cooler

1 m

Supercritical CO2 Cycle Applicable to Most

Thermal Heat Sources

7

1

2

3

5

6

8

Compressors Turbine

HT Recup 4

Alternator Waste Heat

Chiller

LT Recup

CO2

Solar

Carbon Capture & Sequestration

CCS+EOR

Fossil Oxy-Combustion

Supercritical CO2

Brayton Cycle

DOE-NE

Gen IV

Nuclear

(Gas, Sodium, Water)

Military

SNL Solar Tower

SNL has Funding or Research Agreements with most Agencies Representing these Heat Sources

Fix Base & Marine ARRA

Geothermal

Waste Heat Bottoming Cycle

to a Gas Turbine

Energy

Storage & Heat

Transport &

CCHE

Key Features to a Supercritical Brayton Cycle

• Peak Turbine Inlet Temp is well matched to a Variety of

Heat Sources (Nuclear, Solar, Gas, Coal, Syn-Gas, Geo)

• Efficient ~43% - 50% for 10 - 300 MWe Systems

– 1000 F (810 K) ~ 538 C Efficiency = 43 %

– 1292 F (1565 K) ~ 700 C Efficiency =50%

• Advanced Systems (Increase Eff 5-8% points) & Dry

• Standard Materials (Stainless Steels and Inconels )

• High Power Density for Conversion System

– ~30 X smaller than Steam or 6 X for Helium or Air

– Transportability (Unique or Enabling Capability)

– HX’s Use Advanced Printed Circuit Board Heat Exchanger

(PCHE) Technology

• Modular Capability at ~10-20 MWe

– Factory Manufacturable (10 MW ~ 2.5m x 8m)

Advanced Heat Exchangers Meggit / Heatric Co.

Modular & Self Contained Power Conversion Systems ~ 1.5 m x 8 m

Turbine Building

Good Efficiency at Low Operating Temps

Standard Materials, Small Size, Simple,

Modular & Transportable

AFFORDABLE and FABRICABLE

S-CO2

Gen IV S-CO2 Brayton Cycle

Steam

Heat Source Operating Temperature Range

& SCO2 Power Conversion Efficiency

for Various Heat Sources

S-CO2 Power Conversion Operating Temperatures are Applicable for All Heat Sources

Optimum Design Requires Different Approaches for Each Heat Source

Supercritical Fluid Technology has Untapped Growth Potential

100 200 300 400 500 600 700 800 900 Temp C Temp C

Fossil &

Bio Fuels

Solar Power Tower

Solar Trough

Nuclear

43% ~54%

33% Water Sodium 41% He Gas 43% CO2 43%

LWR SFR HTGR AGR

Geo Thermal

Reactor Technologies

1000

36% DRY ~49%

37% 43%

36% DRY ~49%

28% 36%

43% ~54%

Assumptions (Turbomachinery Eff (85%/87%/90% : MC/RC/T), 5 K Approach T, 5% dp/p losses, Hotel Losses Not In Included, Dry Cooling at 120 F)

44% 50% Advanced Condensing Cycle SCO2

GROWTH POTENTIAL

17.5% 31% DRY

37% 50% 56% Wet

32 % 48% 53 % Dry

Advanced Cycles SCO2 GROWTH POTENTIAL

48% 50% 43%

Existing technologies

DOE Supercritical CO2 Program

Description

• DOE Gen-IV S-CO2 Research Program

– Sandia has developed two S-CO2 loops

• Compression Loop (At Sandia) + Brayton Loop (At Barber-Nichols)

• Testing Summary

– Brayton and Compression Loop Descriptions

– Compressor Performance Mapping

– Power Generation in Simple Heated Brayton Cycle

and in Split-Flow Re-compression Brayton Loop

– Mixtures

– Condensation Cycles / Rankine

– Gas Foil Bearing Development

– Thrust Bearing Heating

– High Speed PM Motor Generator Controller Development

– Sealing Technology

• Modeling

• Ability of Sandia S-CO2 Brayton Loop to Reproduce Other Cycles

• Summary and Conclusions

Key Technology Turbo- Alternator Compressor Design

Permanent Magnet Generator with Gas Foil Bearings

~24” Long by 12” diameter

Tie Bolts (Pre-stressed)

Turbine

Compressor

Laby Seals

Journal Bearing Thrust Bearing

Stator

Water Cooling PM Motor Generator

Low Pressure Rotor Cavity

Chamber (150 psia)

Gas-Foil Bearings

125 kWe at 75,000 rpm

Turbomachinery Wheels Designed and Manufactured By Barber-Nichols Inc.

Main

Compressor

Re-

Compressor

Turbine for

Re-Compressor

Turbine for

Main Compressor

Main

Compressor

Re-

Compressor

Turbine for

Re-Compressor

Turbine for

Main Compressor

OD=37.3 mm

1.47”

OD=57.9 mm

2.27”

OD=68.3 mm

2.69”

OD=68.1 mm

2.68”

Coriolis Flow Meter

305 K

7.69 kPa

2.58 kg/s

MC FlowValve

Coriolis Flow Meter

Flow A

127 kW

130 kW

305 K

7.69 kPa

Heaters(777 kW)

RC FlowValve

PCHE Gas Chiller

531 kW

Re-Comp

Main Comp

324 K

13.842 kPa

391 K

13.73 kPa

335 K

7.76 kPa

Turb B

Turb A

750 K

7.88 kPa

750 K

7.88 kPa

699 K

13.6`2 kPa

Expansion Volume

Flow B

MotorGen A

122 kW

130 kW

130 kW

130 kW

130 kW

810 K

13.5 MPa

3.15 kg/s

750 K

7.88 kPa

414 K

7.82 kPa

335 K

7.76 kPa

305 K

7.69 kPa

391 K

13.72 kPa

699 K

13.6`2 kPa

124 kW

MotorGen B

1

2

2m

Compressor

CO2

= =

Motor Alternator Waste Heat

Gas Chiller

Turbine

=

1

2

2m

Compressor

CO2

= =

Motor Alternator Waste Heat

Gas Chiller

Turbine

=

T = 305 K

T = 322.8 K

T = 305.7 K

P = 7690 kPa

P = 13842 kPa

P = 7705 kPa

0 kW

52.8 kW

50.2 kW

50.2 kW

0 % 95 % 66 %

3.51 kg/s

1

2

2m

Compressor

CO2

= =

Motor Alternator Waste Heat

Gas Chiller

Turbine

=

1

2

2m

Compressor

CO2

= =

Motor Alternator Waste Heat

Gas Chiller

Turbine

=

T = 305 K

T = 322.8 K

T = 305.7 K

P = 7690 kPa

P = 13842 kPa

P = 7705 kPa

0 kW

52.8 kW

50.2 kW

50.2 kW

0 % 95 % 66 %

3.51 kg/s

S-CO2 Development Sequence Motor-Driven-Compressor

Inlet Plenum

(Heated for Blowdown Tests)

50 kW Gas Pre-cooler

Haskel Pumps

For cavity purge

Haskel Pump

For System Fill

Motor Controller

Flow Meter orifice

Pressure

Drop Orifice

Support Skid

2m x 4m ~ 6’ x 12 ‘TDrain1 & 2

PDrain1 & 2

T300

P300

T900

P00

T901

P901

T400

P400

T500

P500

P100

T301

P301

Motor-Driven-Compressor

Inlet Plenum

(Heated for Blowdown Tests)

50 kW Gas Pre-cooler

Haskel Pumps

For cavity purge

Haskel Pump

For System Fill

Motor Controller

Flow Meter orifice

Pressure

Drop Orifice

Support Skid

2m x 4m ~ 6’ x 12 ‘TDrain1 & 2

PDrain1 & 2

T300

P300

T900

P00

T901

P901

T400

P400

T500

P500

P100

T301

P301

Sandia Single

Compressor Loop

DOE Gen IV Split-Flow

Re-compression

Brayton Loop

High Temp

PCHE Recuperator

2.2 MW

Electrical Immersion Heaters

130 kW each, ASME

810 K / 1000 F @ 2600 psia

PCHE Gas Precooler

0.5 MW

Turbo-Alternator-Compressor

Main Compressor, 124 kWe

Turbo-Alternator-Compressor

Re-Compressor, 122 kWe

Motor/Alternator Controller

High Temp

PCHE Recuperator

2.2 MW

Electrical Immersion Heaters

130 kW each, ASME

810 K / 1000 F @ 2600 psia

PCHE Gas Precooler

0.5 MW

Turbo-Alternator-Compressor

Main Compressor, 124 kWe

Turbo-Alternator-Compressor

Re-Compressor, 122 kWe

Motor/Alternator Controller

Compressor Maps

Thrust Loads

Gas-Foil Bearings

Seals

Motor Controls

Split-Flow / Re-compression Cycle Control

Multiple Configurations

Power Generation

High Temperature Operation

Startup, Shut Down Procedures

Other Supercritical Fluids (SF6)

Supercritical Mixtures

Condensation Cycle

GenIV-Supercritcal CO2 Brayton Cycle Loop PCHE Recup

2.3 MW

520 kW

Heater

Motor

Generator Controllers

Turbomachinery

Supercritical S-CO2

Brayton Cycle DOE-Gen IV

PCHE Recup

2.3 MW

1.6 MW

Gas Chiller

0.5 MW

Coriolis Flow Meters

Inventory

Tanks

Heater Controllers

Motor

Generator Controllers

Control

System

Supercritical CO2 Brayton Loop

Final Design, Currently Existing, and Alternative Layouts

Coriolis Flow Meter

400A 100A

MC Flow Valve

Coriolis Flow Meter

Flow A

130 kW

130 kW

300

Heaters (780 kW)

RC Flow Valve

PCHE Gas Chiller 531 kW

Re-Comp

Main Comp

500A

500B

400B

Turb B

Turb A

200B

200A

501

Expansion Volume

Flow B

Motor Gen A

122 kW

130 kW

130 kW

130 kW

130 kW

600

100B

203

202 201

503

502

124 kW

Motor Gen B

2011

2012

April 2011

Power Generation in Upgraded S-CO2

Simple Heated Recuperated Brayton Loop

0 1000 2000 3000 4000 5000 6000 70000

1

2

3

4

5

6x 10

4

Time [s]

TA

C A

Sp

ee

d [

rpm

]

TAC A Speed and Power

GenIV_110714_0952

RPM A

SetRPM1

Power A

0 1000 2000 3000 4000 5000 6000 7000-2

-1.5

-1

-0.5

0

0.5

1

1.5

2x 10

4

Po

wer

[W]

Startup Transient

Complete

Breakeven

Electrical Power

Generated 15 kWe

Motor/Generator Power

rpm

Measured T-S Diagram GenIV_110714_0952

Loss Measurements C-2 Compressor T-2 Turbine

Fraction of Turbine Power Used or Lost

Heat Loss

Windage Loss

Compressor

Thermal

Windage

Total Elect.

Fraction Elect. Loss

S-CO2 Power Cycle Economic and

Environmental Benefits

• DOE has invested 5 years and ~ $10-11 M on Proof-of-Principle S-CO2

Power Systems

• The Potential Economic and Environmental Benefits of S-CO2 Power

Systems are Large

– Useful with All Heat Sources

– Dry Cooling, Oxy-Combustion with CCS and EOR, Smaller, Simpler, Improved

Efficiency

• Development is Still Needed

– To date only small scale proof-of-concept development loops are operating

– Heat Source and Power Cycle are Linked (Cycle/Design Research)

– Heat Exchanger Development is Needed

• Micro-Channel Design Costs, Transient Cycling, Packaging, Failure Modes, Cost

Reductions, Nuclear Certification

– Commercial Engineering and Demonstration is Needed using

Industrial Hardware (~10 MWe)

• Already started in industry

• Government/Industry Partnership Role Makes Sense

Scaling Study

Scaling Rules and Ranges of Application for

Key Brayton Cycle Turbomachinery Components

TM Speed/Size

Turbine type

75,000 / 5 cm

Bearings

Seals

Freq/alternator

TM Feature 1.0

Power (MWe)

0.3 3.0 10 30 100 300

30,000 / 14 cm 10,000 / 40cm 3600 / 1.2 m

Single stage Radial multi stage

Axial multi stage

Single stage Radial multi stage

single stage Axial multi stage

Gas Foil

Magnetic

Hydrodynamic oil

Hydrostatic

Adv labyrinth

Dry lift off

Permanent Magnet Wound, Synchronous

Gearbox, Synchronous

Shaft

Configuration Single Shaft

Dual/Multiple

• 10 MWe allows use of Commercial Technologies

High Technology Commercial Technology

High $/kWe Lower $/kWe

Approximate Shaft Speed

and Turbine Wheel Diameter

Shaft Speed versus Elect. Power

1000

10000

100000

1000000

0.1 1 10 100 1000

Electric Power (MW)

Sh

aft

Sp

eed

(rp

m)

1 stage rpm

2 stage rpm

3 stage rpm

15 krpm

35 krpm

Turbine Diameter versus Elect. Power

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

0.1 1 10 100 1000

Electric Power (MW)

Tu

rbin

e O

D (

m)

1 stage Turb OD

2 stage Turb OD

3 stage Turb OD

0.25 m ~ 10”

Printed Circuit Heat Exchanger Scaling Rules Actual

Cost kW lb lb/kW $/lb $/kWth

60000 510 492 0.96 122 118

106000 1600 551 0.34 192 66

210000 2300 1410 0.61 149 91

Average 0.64 154 92

Specific Costs

Need Cost Reductions (Materials, Scale, & Advanced Manuf.) to reach 200$/ kWe

= $ 600/kWe

LT Recup Gas Cooler Water/CO2

Potential Applications • Nuclear

• (LWR, SFR, GCR, Molten Salt Reactors)

• Concentrated Solar Power (CSP) Towers + Troughs

• Military (Fixed Base and Marine)

• Fossil

– Oxy-combustion with Pulverized Coal with CCS + EOR

• Solar Power Towers

• Integrated Bio-Fuel/SCO2 Plant

• Military Applications (Fixed Base and Marine)

• Geo-Thermal

• Waste Heat Applications

– Gas Turbine Bottoming Cycle

– Supercritical Water Oxidation

Concentrated Solar Applications Small or Big ?

1-10 MWe or 100 MWe

0.200

0.300

0.400

0.500

0.600

0.700

0.800

0.900

280 290 300 310 320 330Ef

fici

en

cy o

r Sp

lit F

low

Fra

ctio

nCompressor Inlet T

S-CO2 Recompression Brayton Cycle (with Reheat and IC)

Efficiency

Split Flow Fraction

Advanced S-CO2 Power System

Reheat and Inter-Cooling TIT=700C

Steam Rankine (ENEL)

Gas Turbine (CES)

S-CO2

Or Combinations (PWR)

Fossil Application

Oxy-Coal Combustion

ENEL (Italy)

Nuclear Applications

Why is DOE-NE Interested?

1) Better efficiency than existing plants

2) Smaller Power Plants

(30% of Steam)

3) Simpler Power Plants

(1/10th number of valves)

4) May Eliminate the Intermediate Loop in Sodium Fast

Reactors

S-CO2 Power Cycles for Reactors

NGNP

High Temperature

Gas Cooled Reactor

850-900 C

Sodium Cooled

Reactor

500-550 C

LWRs

Pressurized

Water Reactor

330 C

Potential SMR

Applications

2

3

6

8

CompressorsTurbine

HT

Recup

4 7

Alternator Waste Heat

Cooler

LT

Recup

CO2

5

2

3

6

8

CompressorsTurbine

HT

Recup

4 7

Alternator Waste Heat

Cooler

LT

Recup

CO2

5

2

3

6

8

CompressorsTurbine

HT

Recup

4 7

Alternator Waste Heat

Cooler

LT

Recup

CO2

5

2

3

6

8

CompressorsTurbine

HT

Recup

4 7

Alternator Waste Heat

Cooler

LT

Recup

CO2

5

2

3

6

8

CompressorsTurbine

HT

Recup

4 7

Alternator Waste Heat

Cooler

LT

Recup

CO2

5

2

3

6

8

CompressorsTurbine

HT

Recup

4 7

Alternator Waste Heat

Cooler

LT

Recup

CO2

5

2

3

6

8

CompressorsTurbine

HT

Recup

4 7

Alternator Waste Heat

Cooler

LT

Recup

CO2

5

2

3

6

8

CompressorsTurbine

HT

Recup

4 7

Alternator Waste Heat

Cooler

LT

Recup

CO2

5

He

He

S-CO2

850 C

650C

450C

800 C

600 C

~ 54 %

~ 46 %

~ 50 % Efficiency

(S-CO2 Brayton)

~ 43 % Efficiency

(S-CO2 Brayton)

Sodium

525C

~ 40 % Efficiency

(S-CO2 Recup Rankine

Condensing Brayton)

315C

LWRs

SFRs

GCRs

Sandia Research Program Summary • Sandia/DOE have two operating S-CO2 test loops

– Research Compression Loop

– Reconfigurable Brayton Loop

• Measured Main Compressor Flow Maps – Overall Good Agreement with Mean-Line Predictions of the Performance Maps

– Over a wide range of operating Temperature, pressure, and density

• Using Brayton loop Configuration available in FY2010 and 2011 • Heater power was limited to 260/390/520 kW

• Produced Power in simple heated recuperated Brayton loops (Main TAC and Re-Comp TAC)

• Power Production in recompression loops (still limit to break even)

• Cold Startup, Breakeven, Power Production (6% efficiency and 20 kWe), Power/RPM Operation Maps

• Condensation in Tube and Shell and PCHE heat exchangers – Improved Efficiency, HX Development work is beginning

• Test (critical point) were performed with Mixtures of CO2, CO2-Neon, CO2 SF6,

CO2-Butane – Can Increase or decrease Tcrit

– Improved Efficiency (especially for low temperature applications)

• Thrust Gas Foil Bearing Tests and Modeling – Goal : higher thrust load capability and lower frictional power

• Natural Circulation – S-CO2 Gas Fast Reactor

– C3D CFD Model development

• Collaborations with Industry + Larger Scale System Development

Path Forward

– Path Forward

• Continue Testing of Proof-of-Principle Small Loop

• Work/Collaborate with Industry and other Agencies to develop

S-CO2 System for any heat source at the 10 MWe sized system

• Propose for First Nuclear Applications

– Use with LWRs

– Wet and Dry Cooling

– 37% and 30% Efficiencies

– Develop S-CO2 Systems for Nuclear Technology

– Begin Seeking Gov. Funded 10 MWe S-CO2 power system

development to support FE, EERE, NE, Other

• Useful for all heat sources (Nuclear, Solar, Fossil, Geothermal)

• Numerous early non-nuclear Products (Marine, Fossil, Solar,

Geo, Waste Heat, Heat Storage and Transport)

• Improved the economic and environmental benefits for all

systems (Smaller, Simpler, more Efficient, No Water Cooling)

S-CO2: Potential

Potential for S-CO2 Power Generation

Systems to Improve Economics and

Environmental Issues on a Large Scale

1) Dry Cooling

2) Oxy-Combustion, with CCS and EOR

3) Smaller and Simpler (than steam)

4) Improved Efficiency

5) Combined Heating, Cooling, and Power

Cycles

Applicable For All Types of Heat Sources