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Toward optimization of a wind/ compressed air energy storage (CAES) power system

Toward optimization of a wind/ compressed air energy storage (CAES) power system. Jeffery B. Greenblatt Samir Succar David C. Denkenberger Robert H. Williams Princeton University, Princeton, NJ 08544 Guyot Hall, (609) 258-7442 / 7715 FAX, jgreenbl@princeton.edu.

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Toward optimization of a wind/ compressed air energy storage (CAES) power system

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  1. Toward optimization of a wind/ compressed air energy storage (CAES) power system Jeffery B. Greenblatt Samir Succar David C. Denkenberger Robert H. Williams Princeton University, Princeton, NJ 08544 Guyot Hall, (609) 258-7442 / 7715 FAX, jgreenbl@princeton.edu Electric Power Conference, Baltimore, MD, 30 March – 1 April 2004 Session 11D (Wind Power II), 1 April 2004 Foote Creek Rim, Wyoming

  2. Energy in a Greenhouse World • U.S. 2001 electricity use: 3,600 TWh. Only 0.5% was wind-generated. • U.S. wind potential: ~10,600 TWh/yPossible major role in climate-change mitigation…under carbon constraint, can wind compete with coal? • Resource concentrated in sparsely populated Great Plains—exploitation requires getting wind power to distant population centers Sources: AWEA, 2003; EIA, 2003; EWEA, 2001, Wind Force 12

  3. Does wind power need storage? Three roles for storage: Power Make wind dispatchable (price arbitrage; even at small wind market share) Time Time Offset declining capacity value of wind power as market share expands Value Market share Facilitate use of remote, high-quality wind resources by reducing transmission costs—role first advanced by Cavallo (1995)

  4. Electric storage options Cost with 20 hrs. storage ($/kW) Source: Schainker, 1999 and EPRI/DOE, 2003 Technology Compressed Air Energy Storage (CAES) (≥ 300 MW) Pumped hydroelectric Advanced battery (10 MW) Flywheel (100 MW) Superconductor (100 MW) Capacity ($/kW) Storage ($/kWh) ~1 10 100 300 300 440 900 120 150 120 460 1100 2100 6200 6100 • CAES is clear choice for: • Several hours (or more) of storage • Large capacity (≥ 300 MW)

  5. CAES system Compressor train Expander/generator train Air Exhaust PC PG Intercoolers Heat recuperator PC = Compressor power in PG = Generator power out Fuel (e.g. natural gas, distillate) 70-100 bar Aquifer, salt cavern, or hard mine Air Storage hS = Hours of storage (at PG)

  6. A wind/CAES model PWF PTL CF CAES plant Wind farm Transmission PWF = Wind Farm (WF) max. power out (rated power) PTL = transmission line (TL) max. power Underground air storage CF = TL capacity factor For this application CAES is needed to provide baseload power

  7. Research objectives • What are the important parameters that affect capacity factor (CF) and cost of energy (COE) at end of TL? How do these parameters interact? • What is the lowest cost wind/CAES configuration for baseload power (e.g., CF > 0.80)? • What combination of parameters (including cost improvements) are required to make wind/CAES competitive with coal at end of TL?

  8. d dv [1–e–(v/c)k] (v)= Wind farm simulation Weibull wind speed distribution Wind turbine power curve Turbine Cp = 0.39 Array efficiency = 0.86 (below rating) = 1 (above rating) Cut-out Rated power Cut- in (k2 > k1) Power Probability Rated speed Wind speed Wind speed Wind speed time series Wind power time series Autocorrelation time (hA) } Power “lost” Rated power Wind speed Wind speed Time Time

  9. CAES model Lost power (if storage full) CO2 Compressor Generator Air PC PG Loss Loss Fuel Air storage Spilled power hS HVDC TL PTL Direct output (≤ PTL) PWF Loss

  10. Base case configuration Wind resource: k = 2.0, vavg = 8.98 m/s, Pwind = 560 W/m2 (Class 5) hA = 5 hrs. System CF = 0.84 COE = 9.5 ¢/kWh PC = 0.67 PTL (1330 MW) PG = 1.00 PTL (2000 MW) Comp Gen hS = 20 hrs. = 4 hA (~700 Mft3) WF: PWF = 2.5 PTL (5000 MW) Spacing = 50 D2 vrated = 1.5 vavg Hub height = 84 m TL: PTL = 2000 MW D = 1500 km V = +408 kV DC Eo/Ei = 1.5 CAES system

  11. Base case cost assumptions • Wind turbines: $923/kW (Malcolm & Hansen, NREL, 2002) • 1500 kW, 70 m diameter, 84 m hub height • CAES system: $460/kW (EPRI/DOE, 2003) • $155/kW compressor, $170/kW generator, $170/kW BOP, $1/kWh storage (solution-mined salt cavity) • Transmission:$345/kW, $460k/km (Hauth et al., ORNL, 1997) • $215/kW line, $100/kW converters, $30/kW right-of-way • 15% capital charge rate

  12. Wind farm size vs. COE Min. COE: 8.8¢/kWh (–8 %) PWF = varied PC = 0.7 PTL PG = 1.0 PTL hS = 4 hA V = 408 kV Trans. losses Transmission CAES Wind farm * * = Base case 1.0 1.5 2.0 2.5 3.0 1.7 Wind farm size (PWF/PTL)

  13. CAES compression vs. COE Min. COE: 9.2¢/kWh (–4%) Trans. losses PWF = 2.5 PTL PC = varied PG = 1.0 PTL hS = 4 hA V = 408 kV Transmission CAES Wind farm * * = Base case • 0.0 0.2 0.4 0.6 0.8 1.0 1.2 CAES compression size (PC/PTL)

  14. CAES generation vs. COE Min. COE: 9.1¢/kWh (–5%) PWF = 2.5 PTL PC = 0.7 PTL PG = varied hS = 4 hA V = 408 kV Trans. losses Transmission CAES Wind farm * * = Base case • 0.0 0.2 0.4 0.6 0.8 1.0 1.2 0.3 CAES generation size (PG/PTL)

  15. CAES storage time vs. COE Min. COE: 9.5¢/kWh (no change) Trans. losses PWF = 2.5 PTL PC = 0.7 PTL PG = 1.0 PTL hS = varied V = 408 kV Transmission CAES Wind farm * * = Base case • 1 10 100 1000 CAES storage time (hours)

  16. Transmission voltage vs. COE Min. COE: 8.6¢/kWh (–10%) Trans. losses PWF = 2.5 PTL PC = 0.7 PTL PG = 1.0 PTL hS = 4 hA V = varied Transmission CAES Wind farm * * = Base case • 400 600 800 1000 1200 Transmission voltage (kV)

  17. Optimization Base case Case A Optimum COE = 7.5¢/kWh (–21%) COE = 9.5¢/kWh CF = 0.84 CF = 0.81 Trans. losses Trans. losses PWF = 2.5 PTL PG = 1.0 PTL PC = 0.7 PTL hS = 4 hA V = 408 kV PWF = 1.8 PTL PG = 0.5 PTL PC = 0.8 PTL hS = 10 hA V = 700 kV Transmission CAES Transmission CAES Wind farm Wind farm

  18. Competition with Coal IGCC withCCS (CO2 Capture and Storage) IGCC Wind/CAES • Coal IGCC: 6.2 ¢/kWh • Wind/CAES: 7.5 ¢/kWh • What does it take to make wind/CAES competitive? • Need some combination of: • Better winds • Cheaper turbines • Production tax credit • Carbon tax 1500 km Assume: IGCC ($1635/kWe,  = 30%) in Portland, Oregon Wind/CAES in E. Wyoming Fuel prices: $1.36/MBtu (coal); $4.64/MBtu (natural gas)

  19. Wind power density vs. COE 7.5 ¢/ kWh PWF = 1.8 PTL PG = 0.5 PTL PC = 0.8 PTL hS = 10 hA V = 700 kV Pwind = varied Cturb = $923/kW 6.2 ¢/ kWh Coal IGCC with CCS Trans. losses Transmission CAES Wind farm * * = Case A • 400 600 800 1000 560 930 Wind power density (W/m2) Wind power class: 4 5 6 7+

  20. Turbine cost vs. COE Current: 7.5 ¢/ kWh Future: 6.2 ¢/ kWh PWF = 1.8 PTL PG = 0.5 PTL PC = 0.8 PTL hS = 10 hA V = 700 kV Pwind = 560 W/m2 Cturb = varied Coal IGCC with CCS * * = Case A • 200 400 600 800 1000 650 923 Turbine cost ($/kW)

  21. Production tax credit • Expired Dec. 31, 2003; extension through 2006 in pending energy bill (H.R. 6) • 10-year credit @ 1.8 ¢/kWh renewable energy • Levelized credit = 1.1 ¢/kWh (assume 25-year lifetime, 89% renewable content of wind/CAES) PWF = 1.8 PTL PG = 0.5 PTL PC = 0.8 PTL hS = 10 hA V = 700 kV Pwind = 560 W/m2 Cturb = $923/kW Wind/CAES Case A Wind/CAES with PTC Coal IGCC with CCS 7.5¢/kWh 6.4 ¢/kWh 6.2 ¢/kWh

  22. Carbon tax vs. COE Assume: Turbine cost: $923/kW Class 5 winds (560 W/m2) Production tax credit of 1.1 ¢/kWh Wind/CAES will compete at $140/tC but is sensitive to technology cost; essentially a dead heat! Wind/CAES w/ PTC Coal IGCC w/ CCS Break-even ~$140/tC Coal IGCC w/ CCS: 0.042 tC/MWh; 0.42 ¢/kWh per $100/tC Wind/CAES: 0.026 tC/MWh; 0.26 ¢/kWh per $100/tC

  23. Other competing technologies Assume: Turbine cost: $923/kW Class 5 winds (560 W/m2) Production tax credit of 1.1 ¢/kWh Coal IGCC Coal SC steam Wind/CAES w/ PTC NGCC Coal IGCC w/ CCS CO2 vented Non-decarbonized electricity will have trouble competing in carbon-constrained market, with exception of natural gas (NGCC).However, diversity will require competition with decarbonized energy.

  24. Conclusions • Explored wind/CAES sensitivity of transmission capacity factor and cost of energy to multiple configuration parameters. • Optimal configuration (with today’s technology and no subsidy) gives 7.5 ¢/kWh for 2 GW wind/CAES system with 81% CF and 1500 km transmission line • Break-even cost with coal IGCC/CCS achievable with at least one of the following: betterwind resources,lower turbine cost, production tax credit with carbon tax.

  25. Future research • Explore model sensitivities, particularly cost assumptions, in more detail • Develop more detailed case studies for configurations such as the Wyoming-to-Oregon wind/CAES system depicted here • Develop better synthetic wind algorithms for general use

  26. Acknowledgments • Dennis Elliott, Michael Milligan, Marc Schwarz, and Yih-Wei Wan, NREL • Al Dutcher, HPRCC • Marc Kapner, Austin Energy • Nisha Desai, Ridge Energy Storage • Bob Haug, Iowa Municipal Utilities District • Paul Denholm, University of Wisconsin, Madison • Joseph DeCarolis, Carnegie Mellon University • Al Cavallo, NIST

  27. Extra material

  28. Wind turbine rating vs. COE Min. COE: 9.5¢/kWh (no change) PWF = 2.0 PTL vrated = varied PC = 0.7 PTL PG = 1.0 PTL hS = 4 hA V = 408 kV Trans. losses Transmission CAES Wind farm * * = Base case 0.5 1.0 1.5 2.0 Wind turbine rating (vrated/vavg)

  29. Transmission distance vs. COE 9.5¢/kWh PWF = 2.5 PTL PC = 0.7 PTL PG = 1.0 PTL hS = 4 hA V = 408 kV D = varied Trans. losses Transmission CAES Wind farm * * = Base case 500 1000 1500 2000 2500 Transmission distance (km)

  30. Storage vs. autocorrelation time 100 Cut along constant hS: Base case CF = 79% 10 CF = 74% Base case CF Storage time (hS) (hrs. log scale) hS = hA case CF = 70% 1 CF = 65% hA (hrs. log scale) No improvement in CF if hS >> hA or vice-versa 0.1 0.1 1 10 100 Autocorrelation time (hA) (hrs. log scale)

  31. Compressor/generator ratio Max. CF = 85% 1.5 Slope ~ 1.7 For given CF, least cost configuration appears to lie along slope line Minimal increase in CF for PG/PTL = 0.5  1 Base case 1 PC/PTL CF = 81% 0.5 CF = 76% CF = 72% CF = 68% 0 0.5 1 1.5 PG/PTL

  32. Power derating Rated power vavg = 7.9 m/s Pwind = 560 W/m2 (Class 5) 1500 kW vrate/vavg kW MWh/y CF # turbines $M $/kW ¢/kWh* *15% CCR 1.2 770 3400 0.51 2600 1.17 1500 5.2 1.5 1500 4700 0.36 1300 1.39 920 4.4 770 kW Power probability Full range vrate/vavg = 1.2 1.5

  33. Exploiting lower wind classes 8.4 ¢/ kWh 7.5 ¢/ kWh PWF = 1.8 PTL PG = 0.5 PTL PC = 0.8 PTL hS = 10 hA V = 700 kV Pwind = varied Cturb = $923/kW Trans. losses Transmission CAES Wind farm * * = Base case • 400 600 800 1000 450 560 Wind power density (W/m2) Wind power class: 4 5 6 7+

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