natural gas-fueled distributed generation sofc systems
TRANSCRIPT
Natural Gas-Fueled Distributed Generation SOFC SystemsPerformance and Cost of Electricity
Prepared for:10th Annual SECA Meeting10th Annual SECA MeetingPittsburgh, PA, USA
Date: July 14th, 2009
4910 163rd Avenue NE, Redmond, WA 98052, USAt: 206 229 6882; e: [email protected]
Agenda
1 Background Objective and Approach
System Definition
1
2
Background, Objective, and Approach
3 Heat & Material Balances
4 Cost AnalysisCos a ys s
5 Conclusions
Interest in fuel cells for distributed generation has Background
gwaxed and waned.
• Around 2000, interest in DG peaked:Around 2000, interest in DG peaked:– Low natural gas cost (Henry Hub ~$2/MMBTU)– Prospect of suitable new generation technologies
• Fuel cells were thought to be a good fit:– Low emissions– High efficiency– Small scale
• But:– Fuel cells were not ready
$ /– Natural gas cost rose (Henry Hub >$4/MMBTU)
DOE wanted to understand the performance & cost Objective
pstate-of-the-art SOFC in DG applications.
• Basis for analysis:Basis for analysis:– 5 MWe grid-connected system– SOFC stack technology available commercially 2020– Relevant energy cost (EIA projections)– Appropriate operating strategies (incl. CHP) – Consider cost implications of DG operation
• Based on detailed performance & cost analysis• Allow comparison with central generation options
such as IGCC and IGFC• Consider potential impact of CCS requirements
We used our established fuel cell system model to Approach
yproject NG DG SOFC system performance and cost.
Define SystemDefine System
Analyze Stack Analyze Stack PerformancePerformance
Compute System Heat & Material Balances
Compute System Heat & Material Balances
System Efficiency, Emissions
Obtain Sizing ParametersObtain Sizing Parameters
Estimate System CAPEX & OPEXEstimate System CAPEX & OPEX
LCOECAPEX & OPEXCAPEX & OPEX
Consider Impact of Carbon Capture Separately in Sensitivity AnalysisSeparately in Sensitivity Analysis
Agenda
1 Background Objective and Approach
System Definition
1
2
Background, Objective, and Approach
3 Heat & Material Balances
4 Cost AnalysisCos a ys s
5 Conclusions
The application and scale dictates a simple and System Definition Design Considerations
pp pefficient flowsheet.
• Stack technology: atmospheric w/ separated flowsStack technology: atmospheric w/ separated flows• Relatively small system:
– Simple maintenanceSimple maintenance– Easy siting / permitting– Low cost
• This means:– Avoid wet scrubbing / adsorption processes– Minimize # of unit operations– Minimize water consumption– Avoid noisy components (compressors)
System Definition Process Flow Diagram
SOFCCathodeAir Air PreheatAnode
Cathode
Steam Superheat
Steam Generator
Water
Air Air Preheat
SuperheatGenerator
PreheatNatural
SMRPreheatGas
SMR
Tail Gas
Burner
Exhaust
The SOFC stack assumptions used are consistent System Definition Stack Assumptions
pstate-of-the-art stacks and with other recent studies.
• Performance consistent with state-of-the-art planar Performance consistent with state of the art planar technology:– Polarization similar to current performance– Durability and temperature range consistent with DOE
program targets for 2015C h ll (125 2) d l (2000 2) ll– Case with small (125 cm2) and large (2000 cm2) cells
Fuel Utilization 70% / 86%
Key Stack Performance Characteristics
Stack Temperature 650 – 800°C(single pass / overall)
Cathode Stoichiometry
Anode Recycle
70% / 86%
2 86
60%Cell Voltage
Stack Temperature
0.83V
650 – 800 C
Cell Current Density 0 50 A/cm2 Cathode Stoichiometry 2.86Cell Current Density 0.50 A/cm2
Several carbon capture options are technically System Definition Carbon Capture Options
p p ypossible.
• Sorbent capture from exhaustSorbent capture from exhaust• Water gas shift + capture from syngas• Oxyfuel combustion of anode exhaust + whole gas Oxyfuel combustion of anode exhaust + whole gas
capture
Agenda
1 Background Objective and Approach
System Definition
1
2
Background, Objective, and Approach
3 Heat & Material Balances
4 Cost AnalysisCos a ys s
5 Conclusions
To achieve high efficiency, significant recuperation Heat Balance
g y, g pis necessary.
Sankey Diagram for Baseline 5 MW NGDG SOFC System
0 8 MW O h
2.5 MW Thermal Losses
1.3 MWth Chemical Recuperation
Heat
Fuel
0.8 MW Other Parasitics
5.5 MWth Thermal Recuperation
5.2 MWe Net
9.1 MW Gas Feed
5.8 MWeDC P
Fuel Cell
Stack
Steam Methane Reformer e
PowerFeed DC Power
1.9 MW Syngas Recycle
StackReformer
Syngas recycle is critical to the system water Water Balance
y g y ybalance: it provides steam for the reformer.
Water Management (5 MW System)
0 4 kg/s 0.03 kg/s Make- Up 0.4 kg/s
moisture to exhaust
Make- Up Water
Steam Methane Reformer Net Water
0.52 kg/s in SyngasRecycle
Net Water consumption: ~800 gal/day
(or 7 gal/MWhnet)y ( g / net)
~58% efficiency (HHV) is achievable in simple-Performance Analysis Results
y ( ) pcycle configuration.
System Performance (5 MW DG System)
Fuel Utilization (single pass, overall)
Cathode StoichiometryAnode Recycle
70% / 86%
2.8660%
Fuel Cell Stack
St / C b R ti 3R f
Cell VoltageStack Temperature
0.83 V650 – 800°C
Fuel Cell Gross Power 5.7 MWSteam / Carbon RatioMethane SlipWater Use
37%
800 gpd
Reformer
Blower Power 230kWBoPOther Parasitic LoadsBlower Power
50 kW230kWBoP
Exhaust Temperature 315 °CSystemSystem Efficiency (HHV Basis) 57.6%y y ( )
Cell voltage and stack temperature rise have the Performance Analysis Sensitivity Analysis
g pgreatest impact on efficiency.
Sensitivity of System Efficiency (5 MW DG System)y y y (5 MW G Sy )
Cell Voltage 0.77 0.85 VFuel Cell
57.6%
Anode Recycle
Stack ∆T
40 - 75%
75 – 200°CStack
Fuel Utilization 60 %– 85%
Stack Heat LossSteam / Carbon Ratio
50 %– 200%2 – 3.5Reformer
Fuel Utilization 60 %– 85%
Other Parasitic Loads
Blower Efficiency
25 – 250 kW
50%- 85%
BoP
56% 58%54% 60%56% 58%54% 60%
Oxyfuel combustion & whole anode gas capture Cost Analysis Results LCOE Impact of CO2 Capture
y g plikely presents the most realistic CCS option.
Impact of CCS on Efficiency (Maximum 30 gCO2/kWh Emissions)
40%
50%
60%
Effic
ienc
y V
)
20%
30%
0%
Sys
tem
E(%
HH
-10%
0%
10%
Baseline Shift & Absorb End-of-Pipe Oxy-Fuel
Net
MEA
With CSSNo CSS With CSSNo CSS
Agenda
1 Background Objective and Approach
System Definition
1
2
Background, Objective, and Approach
3 Heat & Material Balances
4 Cost AnalysisCos a ys s
5 Conclusions
The cost analysis followed a well-established Cost Analysis Results CAPEX Approach
ymethodology, building on several previous studies.
• Bottom-up activity-based stack cost analysisBottom up activity based stack cost analysis• BoP equipment costs via scaling from quotes• Costs were escalated to 2007 based on DoC’s PPICosts were escalated to 2007 based on DoC s PPI• A uniform 42.5% installation factor was used
The cost analysis indicates that installed CAPEX Cost Analysis Results CAPEX
ywould be around $870/kW
Capital Cost Estimates (5 MW DG System, 2007$)
800900
1000
net)
QC, Assembly, InstallationControls Inverter
500600700800
t ($/
kWn Controls, Inverter,
InterconnectionRotating Equipment
Th l M t
200300400500
ital C
ost Thermal Management
Reformer
0100200
Cap
i
Stack Infrastructure
SOFC Stack
Small Cells Large Cells
The LCOE from NGDG SOFC systems ranges from 7 Cost Analysis Results LCOE
y gto 9.5 cents/kWh.
NGDG System LCOEy
89
10
Fixed O&M
5678
¢/kW
h)
Non-Fuel Variable O&M
1234
LCO
E (
Fuel
CAPEX
01
Baseload 12 on / 12 off
CHPoff
Gas price, carbon capture, and stack degradation Cost Analysis Results LCOE Sensitivity Analysis
p , p , gmost strongly impact LCOE for DG systems.
Sensitivity of LCOE (5 MW DG System)
Gas Price (2 5 - 12 $/MMBTU)
A id d Di t C t (0 2 ¢/kWh)Stack Degradation (0, 1.5%)
Carbon Capture (0 - 90%)Gas Price (2.5 - 12 $/MMBTU)
Capacity Factor (60 - 95%)CAPEX (660 - 1220 $/kW)
Avoided Distr. Cost (0 - 2 ¢/kWh)
4 5 6 7 8 9 10 11 12
System Efficiency (52 - 61%)
Agenda
1 Background Objective and Approach
System Definition
1
2
Background, Objective, and Approach
3 Heat & Material Balances
4 Cost AnalysisCos a ys s
5 Conclusions
Technically spectacular NGDG SOFC systems Conclusions
y p yappear feasible...
• State-of-the-art SOFC enable highly efficient, State of the art SOFC enable highly efficient, simple-cycle, systems:– ~58% efficiency (HHV basis)– Water use ~7 gal/MWh– CO2 emissions 340 g/kWh (CCS technically possible)– Very low noise, local air emissions
• But degradation should be reduced to 0 5%/1 000 h l~0.5%/1,000 hrs or less
… and in some selected market segments their cost Conclusions
gcould be attractive.
• In high-volume production:In high volume production:– CAPEX ~$870/kW (2007$)– LCOE 7.2 – 9.3 ¢/kWh/– Strong function of gas price, capacity factor
• This range is likely competitive in selected market segments (CHP, incentives, local conditions)
• It is not broadly competitive with central generation• If deep carbon reductions are required(>60%):
– CCS would be required – NG DG would likely be uncompetitive
Acknowledgement
• Thanks to Wayne Surdoval and Mark Williams for Thanks to Wayne Surdoval and Mark Williams for guidance,
• to Jim Powers and Phil Khore for input in pformulating the analysis assumptions,
• And to numerous others for feedback• Carried out under a DOE subcontract to RDS
(#41817M2846)