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NREL is a national laboratory of the U, S, Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC,
Energy Storage: Days of Service
Sensitivity Analysis
Michael Penev, Neha Rustagi, Chad Hunter, Josh Eichman
National Renewable Energy Laboratory
Hydrogen and Fuel Cell Technical Advisory Committee
March 19, 2019
This presentation does not contain any proprietary, confidential, or otherwise restricted information
Screening Analysis Motivation: Role of H2 in Energy Storage Market
National Renewable Energy Laboratory Innovation for Our Energy Future 2
42%
37%
13%
5.6%
1%
1%
0.3%
0.09%
0 1,000 2,000 3,000
Thermal storage
Batteries
Flywheels
Compressed air w/ natural gas
Capacitors
Flow batteries
Hydrogen (power to gas)
Compressed air
Global operational capacity in 2018 (MW)
Source: DOE Global Energy Storage Database: https://www.energystorageexchange.org/
Global Energy Storage Inventory: • 95% is pumped hydro serving diurnal operation • Batteries typically provide few hours of storage • Thermal storage is predominantly molten salt for concentrated solar • Fly wheels provide very short duration storage (frequency regulation)
Pumped hydro96%
Screening Analysis Scope
National Renewable Energy Laboratory Innovation for Our Energy Future 3
System Energy storage options Performance & cost metrics
H2 & fuel cell Tank storage Salt domes Current status Future potential
Battery, lithium ion Battery Current status Future potential
Analyzed Components:
• Rectifier
• Electrolyzer
• Hydrogen compressors
• Hydrogen storage
• tank storage
• salt domes (geologic, 3 in USA)
• Batteries
• lithium ion
• Power generation
• fuel cell
• Inverter
Cost and performance parameters were extensively peer reviewed by battery and
hydrogen technology experts.
Current timeframe assumes 6¢/kWh electricity cost for storage recharging.
Future timeframe assumes 3¢/kWh electricity
cost for storage recharging.
Electrolyzer
Diagrams of Storage
National Renewable Energy Laboratory Innovation for Our Energy Future 4
DC Battery
Storage
Power
Conditioning
System
Inverter
Rectifier
Hydrogen
Storage
AC DC
AC DC
Power
Conditioning
System
Inverter
Rectifier AC DC
AC DC Fuel Cell
Compressor H2 H2
H2
Battery Energy Storage Round Trip Efficiency ~95%
Hydrogen Energy Storage Round Trip Efficiency ~35%
Simple Benchmark Profile
National Renewable Energy Laboratory Innovation for Our Energy Future 5
-10%
-8%
-6%
-4%
-2%
0%
2%
4%
6%
8%
10%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 24 48 72 96 120 144 168
Time (hours)
Disch
arging | ch
arging
(%/h)
Stat
eo
f ch
arge
(%)
Simple diurnal cycle:
4 hours power generation
8 hours storage recharge
12 hours stand-by
Interest focus: long duration storage capability
Simple cycle provides a transparent and intuitive means of benchmarking energy storage systems.
Capital Cost Summary
National Renewable Energy Laboratory Innovation for Our Energy Future 6
Technology Timeframe
Assumption
Charging
($/kW)
Storage
($/kWh)
Discharging
($/kW)
Battery Current 196 218 60
Battery Future Potential 183 80 60
Hydrogen in tanks Current 942 35 574
Hydrogen in tanks Future Potential 432 18 300
Hydrogen in salt domes Current 942 0.08 574
Hydrogen in salt domes Future Potential 432 0.08 300
Hydrogen storage provides: • lowest cost of stored energy • more expensive charging and discharging capital • lower round-trip efficiency
Charging capital: Rectifier, Electrolyzer, Compressor
Storage capital: Batteries, H2 storage tanks, salt dome
Discharging capital: Inverter, fuel cell
H2FAST Model Used For Levelized Cost Analysis
National Renewable Energy Laboratory Innovation for Our Energy Future 7
0.59
0.17
0.13
0.03
0.00
0.21
0.17
0.12
0.10
0.09
0.08
0.04
0.04
0.03
0.02
0.01
0.01
0.00
0.00
0.00
0.00
Peak electricity sales
Inflow of equity
Inflow of debt
Monetized tax losses
Cash on hand recovery
Dividends paid
Off-peak electricity
Hydrogen storage
Planned & unplanned…
Repayment of debt
Interest expense
Income taxes payable
Electrolyzer
Installation cost
Fuel cell
Rectifier
Property insurance
Selling & administrative…
Cash on hand reserve
Inverter
Compressor
Operating revenue
Financing cash inflow
Operating expense
Financing cash outflow
Real levelized value breakdown of peak electricity ($/kWh)
-10%
-8%
-6%
-4%
-2%
0%
2%
4%
6%
8%
10%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 24 48 72 96 120 144 168
Time (hours)
Disch
arging | ch
arging
(%/h)
Stat
eo
f ch
arge
(%)
• Equipment sizing • Cost estimation • Efficiency estimation
• Energy Use • Energy Costs • Financial Assumptions
Techno-economic assessment is made based on minimal equipment sizing to achieve
benchmark cycle. H2FAST model was used to evaluate levelized cost of peak power.
Preliminary
https://www.nrel.gov/hydrogen/h2fast.html
Levelized Cost of Energy vs. Duration of
Storage Li-Ion Battery
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
0 1 2 3 4 5 6 7
Financing
Maintenance
Installation
Discharging capital
Storage capital
Charging capital
Operating cost
LCO
E o
f p
eak
po
we
r (2
016$
/kW
h)
Storage duration (days)
Purchased electricity
Excellent round-trip efficiency (95%) minimizes operating costs (purchase of electricity @ 6¢/kWh). Capital intensity is dominated by battery module cost.
National Renewable Energy Laboratory Innovation for Our Energy Future 8
Preliminary
Levelized Cost of Energy vs. Duration of
H2 Storage (FC + Tanks)
National Renewable Energy Laboratory Innovation for Our Energy Future 9
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
0 1 2 3 4 5 6 7
Financing
Maintenance
Installation
Discharging capital
Storage capital
Charging capital
Operating cost
LCO
E o
f p
eak
po
we
r (2
016$
/kW
h)
Storage duration (days)
Purchased electricity
Preliminary
Lower round-trip efficiency (35%) induces higher operating costs. Lower capital cost for storage reduces total cost escalation for long duration storage.
15h
24h(1d)
48h(2d)
72h(3d)
96h(4d)
120h(5d)
144h(6d)
168h(7d)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4 Current.Battery
Current terrestrial H2
Storage duration
LCO
E o
f p
eak
po
we
r (2
016$
/kW
h)
15h
15h
24h(1d)
48h(2d)
72h(3d)
96h(4d)
120h(5d)
144h(6d)
168h(7d)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4Current.Battery
Future.Battery
Current terrestrial H2
Future terrestrial H2
Storage duration
LCO
E o
f p
eak
po
we
r (2
016$
/kW
h)
15h
15h
13h
12h
24h(1d)
48h(2d)
72h(3d)
96h(4d)
120h(5d)
144h(6d)
168h(7d)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4Current.BatteryFuture.BatteryCurrent terrestrial H2Future terrestrial H2Current geologic H2Current geologic H2
Storage duration
LCO
E o
f p
eak
po
we
r (2
016$
/kW
h)
Fuel cells + geologic storage
• Below ~13h with current technology, batteries have economic advantage. • Durations over ~13h favor hydrogen technologies. • Windows of cost use 6¢/kWh electricity for current timeframe and 3¢/kWh for future timeframe.
Economic Performance Benchmark Current
& Future Hydrogen and Batteries
National Renewable Energy Laboratory Innovation for Our Energy Future 10
Preliminary
-100%
0%
100%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 24 48 72 96 120 144 168
Time (hours)
Disch
arging
|chargin
g (%
po
we
r) St
ate
of
char
ge(%
)Hydrogen Co-Production Opportunity
Simple diurnal cycle:
4 hours power generation
8 hours storage recharge
12 hours stand-by
-100%
0%
100%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 24 48 72 96 120 144 168
Time (hours)
Disch
arging
|chargin
g (%
po
we
r) |p
rod
uctio
nSt
ate
of
char
ge(%
)
H2 co-production would improve economics if H2 price exceeds variable operating costs. O2 co-production may also bear value.
hydrogen co-production 11
Take-aways
National Renewable Energy Laboratory Innovation for Our Energy Future 12
1. Hydrogen energy storage technologies have economic
advantage for long-duration storage
Above ~13h of storage with current tech
2. Round-trip efficiency disadvantage over batteries can
be overcome for storage durations greater than ~12h
3. Additional work is needed to understand the potential
revenue (avoided cost) of long-duration storage
4. Energy storage system economics can be improved
with H2 co-production
Acknowledgements
National Renewable Energy Laboratory Innovation for Our Energy Future 13
Peer review for this analysis has included representatives
from:
• DOE, Office of Energy Efficiency and Renewable Energy
(EERE), Fuel Cell Technologies Office
• DOE, EERE, Vehicle Technologies Office
• Xcel Energy
• Southern Company Services
• Argonne National Laboratory
• National Renewable Energy Laboratory
Backup Slides
National Renewable Energy Laboratory Innovation for Our Energy Future 14
Parity Duration Sensitivity vs. Techno-Economic
Parameters (Current, H2 vs. Batteries)
Round-trip efficiency improvements are most important • Electrolyzer, compressor, fuel cell • Above uses 6¢/kWh
12.0
11.9
13.7
14.5
14.6
15.1 20.1
18.3
16.4
15.6
15.6
11 12 13 14 15 16 17 18 19 20 21
Fuel cellenergy production
(24, 20, 16) kWh/kg
Electrolyzerenergy use
(43.4, 54.3, 65.2) kWh/kg
Electrolyzercapital cost
(590, 737, 885) $/kW
Hydrogen storagecapital cost
(935, 1,168, 1,402) $/kg
Fuel cellcapital cost
(406, 507, 608) $/kW
Hydrogen-battery parity storage duration (h)
Preliminary
15
Means of Improving Round Trip Efficiency
Increased efficiency can be traded for capital
expenses 1. Increase electrolysis & fuel cell active area
2. Consider solid oxide electrolysis (SOEC)
3. Consider SOEC with thermal storage (store waste heat from power
generation and use for thermal needs in electrolysis)
4. Consider high pressure electrolysis (reduce compression needs)
5. Consider compression energy recovery with turbo expander
Round trip efficiency is more important than capital cost. Improving efficiency can be traded for increased capital cost.
16
NREL | 17
Technoeconomic Parameter Details
Techno-Economic Parameters Current status Future potential Reference
Rectifiers
Rectifier efficiency 98.4% 98.4% [2]
Rectifier cost ($/kW AC) 196$ 183$ [3]
Total installation cost factor (% of equipment capital) 57% 57% [3]
System O&M (% of capital cost) 1% 1% assumption
Electrolyzers
Electrolyzer power use (kWh DC/kg) 54.3 50.2 [3]
Electrolyzer cost ($/kW DC) 737$ 232$ [3]
System life (years) 20 20 [4]
System O&M (% of capital cost) 8% 9% [3]
Total installation cost factor (% of equipment capital) 57% 57% [3]
Compressors
Power use (kWh AC/kg) 1.42 1.42 [5]
Compressor cost factor A (equation form c=A*p^B; where p is power) 2290 2061 [5]
Compressor cost exponent B (equation form c=A*p^B; where p is power) 0.8225 0.8225 [5]
Total installation cost factor (% of equipment capital) 187% 187% [5]
System O&M (% of capital cost) 4% 4% [5]
Storage
Terrestrial storage installed cost ($/kg) 1,168 600 [5], [6]
Terrestrial storage installed cost ($/kWh LHV) 35 18 assumes 33 kWh/kg H2
Terrestrial storage O&M (% of capital cost) 1% 1% [5]
Geologic storage installed cost ($/kg) 2.69 2.69 [5]
Geologic storage installed cost ($/kWh LHV) 0.08 0.08 assumes 33 kWh/kg H2
Geologic storage O&M (% of capital cost) 4% 4% [5]
Cushion gas (%) 17.1% 17.1% [5]
17
NREL | 18
Technoeconomic Parameter Details
Techno-Economic Parameters Current status Future potential Reference
Fuel cells
Fuel cell power production (kWh DC/kg) 20.0 23.3 [7]
Fuel cell cost ($/kW DC) 507 237 [8]
Total installation cost factor (% of equipment capital) 20% 20% assumption
System O&M (% of capital cost) 6% 6% [8]
Inverters
Inverter efficiency (%) 98.6% 98.6% [9]
Inverter installed cost ($/kW) 60$ 60$ [10]
Total installation cost factor (% of equipment capital) 20% 20% assumption
System O&M (% of capital cost) 1% 1% assumption
Batteries
Charging efficiency 98.3% 99.4% [11]
Discharging efficiency 98.1% 99.4% [11]
Cost ($/kWh) 217.5 80 [12], [13]
System life (years) 10 10 [14]
System O&M (% of capital cost) 1.0% 1.0% assumption
Total installation cost factor (% of equipment capital) 20% 20% assumption
System O&M (% of capital cost) 1% 1% assumption
Feedstock
Electricity cost ($/kWh) 0.060 0.030 assumption
18
NREL | 19
Technoeconomic Parameter Details
Total tax rate (statefederallocal)
General inflation rate
Depreciation method
Depreciation period
Leveraged after-tax nominal discount rate
Debt/equity financing
Debt type
Debt interest rate (compounded monthly)
Cash on hand (% of monthly expenses)
21.00%
100%
3.70%
Revolving debt
1.50
10.0%
5 year
MACRS
1.90%
19
NREL | 20
References
[1] NREL, H2FAST, Spreadsheet version, Retrieved October 2018 from: https://www.nrel.gov/hydrogen/h2fast/
[2] ABB, 2014, High energy efficiency rectifier to power ETI Aluminyum's smelter in Turkey. Retrieved on July, 2018 from: http://www.abb.com/cawp/seitp202/2ea17550ae4cb481c1257b3b003a0515.aspx
[3] Hydrogen Production Analysis H2A, Central PEM Electrolysis, Retrieved October 2018 from: https://www.hydrogen.energy.gov/h2a_prod_studies.html
[4] NREL communications with electrolyzer manufacturing companies
[5] Argonne National Laboratory, Hydrogen Delivery Scenario Analysis Model (HDSAM) version 3.1. Retrieved on July, 2018 from: https://hdsam.es.anl.gov/index.php?content=hdsam
[6] Department of Energy. 2015. Multi-Year Research, Development, and Demonstration Plan, Hydrogen Delivery. Retrieved February, 2019 from: https://www.energy.gov/sites/prod/files/2015/08/f25/fcto_myrdd_delivery.pdf
[7] U.S. Department of Energy. 2016. Multi-Year Research, Development, and Demonstration Plan, Fuel Cell Section. Retrieved October, 2018 from: https://www.energy.gov/eere/fuelcells/doe-technical-targets-fuel-cell-systems-and-stacks-transportation-applications
[8] Battelle Memorial Institute. 2016. Manufacturing Cost Analysis of 100 and 250 kW Fuel Cell Systems for Primary Power and Combined Heat
and Power Applications. Retrieved on July, 2018 from: https://www.energy.gov/sites/prod/files/2016/07/f33/fcto_battelle_mfg_cost_analysis_pp_chp_fc_systems.pdf
[9] ABB. ABB central inverters. Retrieved on July, 2018 from: https://new.abb.com/docs/librariesprovider22/technical-documentation/pvs800-central-inverters-flyer.pdf?sfvrsn=2
[10] Fu, Ran. Et. al. 2017. U.S. Sollar Photovotaic System Cost Benchmark: Q1 2017. Retrieved February, 2019 from: https://www.nrel.gov/docs/fy17osti/68925.pdf
[11] Apostolaki-Iosifidou E, Codani P, Kempton W, Measurement of power loss during electric vehicle charging and discharging, Energy (2017), doi: 10.1016/j.energy.2017.03.015.
[12] InsideEVs. GM: Chevrolet Bolt Arrives In 2016, $145/kWh Cell Cost, Volt Margin Improves $3,500. Retrieved on July, 2018 from: https://insideevs.com/gm-chevrolet-bolt-for-2016-145kwh-cell-cost-volt-margin-improves-3500/
[13] Boyd, Steven. 2019. Batteries and Electrification R&D Overview. https://www.energy.gov/sites/prod/files/2018/06/f53/bat918_boyd_2018.pdf
[14] Smith, K., Saxon, A., Keyser, M., Lundstrom, B., 2017, Life Prediction Model for Grid Connected Li-ion Battery Energy Storage System, National
Renewable Energy Laboratory, Retrieved October 2018 from: https://www.nrel.gov/docs/fy17osti/67102.pdf
20
Long duration storage benefit
• Present work shows likely cost advantage of long duration hydrogen storage
compared to other storage technologies
• Additional cost advantages may include revenue from hydrogen and avoided
costs.
To understand competitiveness of long duration storage, we can perform
cost/benefit comparison using LCOE and avoided costs (LACE)
Preliminary Results – Do not cite
• Previous work has
shown that market for
multi-day storage is
currently limited
• Using power system
models, we can
calculate the benefit
(avoided cost) of
operating the storage
Preliminary results from the EPRI-DOE H2@Scale CRADA Project
show how storage can be used as renewable penetration increases.
21