Assessing the Impact of Distributed Wind Generation

1. Assessing the Impact ofDistributed Wind Generation Tom McDermott, Ph.D., P.E. Senior Consulting Engineer www.enernex.com APPA E&O Tech. Conf., April 16, 2007

2. UWIG’s DistWind Project • Funded by APPA (DEED), NRECA (CRN), EPRI, California Energy Commission, others • Web-based Screening Software Tools • Flicker evaluation • Economics • Web-based Engineering Software Tools • Voltage control • Overcurrent protection • Case studies, application guides, measurements UWIG DistWind

3. Distributed Wind Economics • Capacity Factor: Determines Energy Production • Look at Wind as an Energy Source, not Capacity • Tax Incentives: Enhance the cash flow • Production Tax Credit (PTC) • Clean Renewable Energy Bonds (CREB) • Plus the usual considerations • Debt and Equity financing • Insurance, O&M, tax requirements • Evaluate by net present value (NPV), internal rate of return (IRR), payback period, etc. UWIG DistWind

4. Production Tax Credit (PTC) • Energy Policy Act of 1992 – 1.5 ¢/kWhr • Has been extended five times • Adjusted for inflation – currently 1.9 ¢/kWhr • Lasts for 10 years • Must pay federal income taxes in order to use the PTC • Equivalent REPI for non-taxable entity, under-funded • Tax Relief and Health Care Act of 2006 • Extended PTC to December 31, 2008 UWIG DistWind

5. PTC In WindFinance UWIG DistWind

6. Clean Renewable Energy Bonds • A “tax credit bond” for municipals, cooperatives, tribal governments, others who can’t use PTC • Issuer pays no interest; instead the bondholder receives a Federal tax credit • Energy Tax Incentives Act of 2005 authorized $800M for CREBs issued in 2006 and 2007 • 786 Applications Filed by April 26, 2006 • 610 Approved; 112 for Wind and 434 for Solar • Tax Relief and Health Care Act of 2006 • Extended CREB another $400M (Total $1.2B) • Extended CREB to December 31, 2008 UWIG DistWind

7. CREB In WindFinance UWIG DistWind

8. Capacity Factor • Energy = CF * (8760 hrs/yr) * (kW rating) • Wind speeds are variable • Power depends on speed3 • Actual site measurements are best • Electrical power output depends on the turbine and interface design • Complicated function of aerodynamics and controls • Controls are generally considered proprietary UWIG DistWind

9. http://www.nrel.gov/wind/wind_map.html UWIG DistWind

10. Economics: Capacity Factor Module • Wind Data: • Actual Measured Distribution • Measured Average Annual Speed • Average Annual Speed from a Map • Power Curve: • Specific • From Library • Uploaded • Generic UWIG DistWind

11. What is Flicker? • Short-term Voltage Fluctuations that may cause perceptible, or objectionable, lighting flicker Flicker Period [s] UWIG DistWind

12. What Causes Flicker? • Motor starting and load variations • Arc furnaces and welders • Wind turbines • Variations in wind speed • Blade pitching • Tower shadowing • Wind shear or gradient • Start and stop UWIG DistWind

13. Variations in Wind Speed • Inertia and controls help soften the impact UWIG DistWind

14. Effect of Blade Pitching • Pitch control affects power curve, but doesn’t respond instantly • Stall-regulated blades more closely maintain rated output UWIG DistWind

15. Tower Shadowing • Sometimes called 3-P Effect, 0.5 – 1.5 Hz UWIG DistWind

16. Wind Shear or Gradient • Blade torque varies with position because the wind speed varies with height UWIG DistWind

17. Turbine Start and Stop • Similar to motor starting, but advanced controls and interface may soften the impact UWIG DistWind

18. Old-Style GE Curve • Rectangular Voltage Change, 50% Duty Cycle UWIG DistWind

19. Measurement is Complicated! UWIG DistWind

20. Flicker Evaluation • IEEE Std. 1453-2004 follows the IEC approach • If PST = 1, 50% of the people will complain • Measured every 10 minutes (144 times per day) • Planning Level: PST > 0.9 only 1% of the time • Flicker varies along the feeder UWIG DistWind

21. Flicker Calculator • Quick Answers • On Web Site: • NEG Micon • Nordex • Vestas • GE • Requested: • Mitsubishi • Clipper • others UWIG DistWind

22. Estimating Short-Circuit Strength • Same Data as Used for Harmonic Studies • Estimate the System Impedance at Point of Common Coupling (PCC) at Primary Voltage UWIG DistWind

23. Feeder Simulator for Engineering • Imports MultiSpeak • Shortcuts • Sample Files • On-line Help UWIG DistWind

24. Voltage Control Outputs Checks ANSI C84.1 UWIG DistWind

25. Overcurrent Protection Outputs CB1 should not lock open UWIG DistWind

26. Case Study #1: TVA Buffalo Mountain • Three Vestas V47 WTGs, Total 2 MW • 13.2-kV Feeder, 9.6 miles long, 69-kV Source • No Voltage Control Problems • Removed the High-Speed Reclose Operation • No Reduction of Reach or Sympathetic Trip UWIG DistWind

27. Case Study #2: PGE Hunter’s Point • 12-kV Feeder, 6.4 miles long • One GE 1.5xle Turbine, 1500 kW • Use high-efficiency turbine, greater hub height, and higher wind shear factor than in CEC study • No Flicker Problems or Limits • Voltage Control and Overcurrent Protection limit the total WTG to 7500 kW UWIG DistWind

28. Case Study #3: Illinois Rural Electric • One NM82 Vestas/NEG Micon Turbine, 1.65 MW • Operating since May 2005 • 12.47-kV Feeder, 34.5-kV Transmission Source • IREC Filled out the Feeder Simulator Data Sheet • Overvoltage and Undervoltage Trip Functions are Essential • Evaluated Use of CREB (actual project had 46% grant funding, before CREB available) • Two Turbines → Flicker and Tap Changer Issues UWIG DistWind

29. East River Coop, Chamberlain, SD • Two Nordex N60/1300 Turbines • 69/12.47-kV Substation Transformer, 3750 kVA • 4/0 Cable, 1/3 Concentric Neutral, 12 kft from Substation • On a Dedicated Feeder, but Still had Flicker Complaints • Solutions implemented by Basin Electric: • Turbine Vendor adjusted Controls • Dynamic VAR Compensation • Dedicated Transformer (2500 kVA Mobile) UWIG DistWind

30. Members-Only Index Page(www.uwig.org/distwind) DEED members please contact Michele Ghosh Suddleson for password; msuddleson@APPAnet.org Demos at the UWIG Booth in Vendor Showcase UWIG DistWind