Fundamentals of Wind Energy

Transcription

1 Fundamentals of Wind Energy Charles Newcomb Wind & Water Deployment Section Manager SEET Technology Workshop June 17, 2011 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

2 TOPICS Introduction Energy and Power Wind Characteristics Wind Power Potential Basic Wind Turbine Theory Types of Wind Turbines Review of Small and Large Turbines Review of the Current Wind Market Project Development Further Information

3 years go, in the Middle East What is Wind Power years ago, in Europe 140 years ago, water-pumping wind mills 70 years ago, electric power The ability to harness the power available in the wind and put it to useful work.

4 ENERGY AND POWER ENERGY: The Ability to do work Electrical energy is reported in kwh and may be used to describe a potential, such as in stored energy or the amount of energy used over a time period, like 1000 kwh per day POWER: Force at any instant The amount of energy needed at any instant in time. Represents current generation and constraints such as Generator Size or an instantaneous load which is measured in kw

5 P = 0.5 ρ v 3 P: power, Watt Power in the Wind ρ: density of air, kg/m 3 V: wind speed, m/s We call this the Wind Power Density (W/m 2 ) which is a measure of the power available in the wind at a specific point or as an average over a longer period of time

6 Power from the Wind P = 0.5 ρ v 3 Cp A S Cp = Coefficient of Performance (an efficiency term) A S = The swept area of the wind turbine blades Multiplied by time give you Energy

7 Critical Aspects of Wind Energy P = 0.5 ρ Cp v 3 A S V 3 : Doubling of the wind speed results in an 8 fold increase in power ρ: High density air results in more power (altitude and temperature) A s : A doubling of blade length, increases the area four-fold Cp: Different types of wind turbines have different maximum theoretical efficiencies (Betz limit 0.593) but usually between.4 and.5

8 Velocity The Impact on Increasing Wind Speed A small increase in wind speed increases the available energy greatly Annual Energy, MW h Annual Energy Output Capacity Factor (%) 50% 40% 30% 20% 10% Average Wind Speed, m/s 0%

9 Elevation, ft 10,000 9,000 8,000 7,000 6,000 5,000 4,000 3,000 2,000 1, Density Change Compared to Sea Level, % Changes with Temperature Temperature, F Air Density - Changes with Elevation Density Change Compared to 59 F, %

10 Swept Area 500 kw 1257 m 2 (40m) 300 kw 415 m 2 25 kw 78 m 2 10 kw 38 m 2 1 kw 6 m kw 2400 m 2 (56m) A = (π D2 ) 4

11 Wind Characteristics and Resources Understanding the wind resource at your location is critical to understanding the potential for using wind energy Wind Speed Wind Profile Wind classes Collection and reporting Wind Direction Wind speed change with height

12 So, which is better 1. A location where the wind that blows only 50% of the time at 10 m/s but is calm the rest of the time 2. A location where the wind that blows all of the time at 5 m/s P = 0.5 ρ Cp v 3 A S Both have exactly the same annual average wind speed

13 Impacts on Wind Speed Many things impact the speed and direction of the wind at any specific location, making local measurements important

14 Wind Speed Increases with Height Because of friction with the earth, air closer to the surface moves more slowly The farther we get away from the earth (increase in altitude) the higher the wind speed gets until it is no longer effected by the earths surface Height, m :10 12:20 12:30 12:40 12:50 Pow er Law Log Law Wind Speed, m/s 8 10

15 Height m Wind Shear Wind Speed, m/s SURFACE The type of surface (grass, trees) impacts the wind shear Real vs. apparent height

16 V N = V O h h N O N Factoring in Measurement Height The Power Law V N = V O h h N O N V N : Wind speed at new height, V O : Wind speed at original height, h N : New height, h O : Original height, N: Power law exponent. Terrain Power Law Exponent Water or ice 0.1 Low grass or steppe 0.14 Rural with obstacles 0.2 Suburb and woodlands / Source: Paul Gipe, Wind Energy Comes of Age, John Wiley and Sons Inc, 1995, pp

17 Height Impacts on Power 3.50 Increase Compared to 30 ft Wind Speed Increase Wind Power Increase Tower Height, ft

18 Micro-Siting Example: Obstruction of the Wind by a Small Building (Caution) Prevailing wind H Region of highly disturbed flow 2H 2H 20H

19 Basic Wind Turbine Theory Lift and Drag The different types of wind turbines Aerodynamics How turbines work Power Curves The performance of wind turbines Power Availability - Power your can get from the wind Different types of lift turbines

20 Types of Small Turbines Drag Design High torque* High wind speed design* Very durable* HAWT Design Aerodynamic lift Higher efficiency Lower weight Moderate wind speed operation Tower accessible VAWT Design Aerodynamic lift Higher efficiency Lower weight Moderate wind speed operation

21 Aerodynamic Drag FLAP PLATE CUP PANEMONE TURBINE shield rotation WIND

22 Aerodynamic Lift

23 Lift Wind Turbines

24 WTG Power Curve Rated wind speed Cut in wind speed Cut out wind speed

25 Important Terms Cut in wind speed: The wind speed that the turbine starts producing power (may be different than the speed at which the turbine starts spinning) Rated Wind Speed: The wind speed at which the turbine is producing rated power though rated power is defined by the manufacture Cut out wind speed: The wind speed at which the turbine stops producing power Shut down wind speed: The wind speed at which the turbine stops to prevent damage Design wind speed: Wind speed that the turbine is designed to withstand without falling over

26 Wind Turbine Power Curve Bergey 1500 (manufacturer s data) Power (kw) Wind Speed (m/s)

27 Wind Speed Frequency of Occurrence Average Wind Speed: 5 m/s (11 mph) Time (Hours) Wind Speed (m/s)

28 Annual Energy Production: 2643 kwh/year Bergey 5 m/s (11 mph) average wind speed Energy (kwh) Wind Speed (m/s) All available energy may not be captured

29 Types of Lift Turbines HAWT VAWT

30 Basic Properties of HAWT Basics of a horizontal axis wind turbine Types of turbines Small distributed turbines Large grid connected turbines

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32 Parts of a Wind Turbine Rotor

33 Basic Motion of a Wind Turbine Pitch Rotation Yaw

34 Different Types of Wind Turbines Utility-Scale Wind Power ,000 kw wind turbines Installed on wind farms, MW Professional maintenance crews Classes 4 and up (> 6 m/s average) Distributed Wind Power 100 W kw wind turbines 1,500 kw 10 kw Installed at individual homes, farms, businesses, schools, etc. On the customer side of the meter High reliability, low maintenance Classes 3 and up (>5 m/s average)

35 Sizes and Applications Small ( 10 kw) Homes Farms Remote Applications (e.g. water pumping, telecom sites, icemaking) Midscale ( kw) Village Power Hybrid Systems Distributed Power Large (>1000 kw MW) Utility-scale wind farms Large Distributed Power

36 Large Wind Turbines Typically induction or variable speed permanent magnet generators Create AC power supplied to the grid Actively controlled

37 Parts of a Wind Nacelle Turbine Power Plant Blades Boeing Tower

38 Characteristics of Large WTG Power Types Doubly-fed Induction (asynchronous) Permanent Magnet (Variable speed) using power electronics Power System Efficiencies Aerodynamic Rotor Drive train / gear box Generator Power Conversion (if applicable)

39 Control of Large WTG Fixed Pitch (Stall regulated): As the attack angle changes (due to increasing wind speed) parts of the blade stop producing lift and limit power. Variable Pitch: The rotation (pitch) of each blade is individually controlled to control lift according to wind speed Yaw: Motors control yaw behavior based on a wind direction vain, used to shut down wind turbine in high winds but can also be a source of problems. Brake: All wind turbines are required to have two of them but there are several types: Aerodynamic: Flaps on the blades that cause drag or pitching of blades to feather, typically redundant, failsafe Mechanical: Disks or calipers, like your car. Electrical: using the generator to cause electrical resistance.

40 Other Large (and Small) Turbines Considerations Policy Siting Transmission External Conditions Intermittency Extreme events

41 Drivers for Wind Power Declining Wind Costs Fuel Price Uncertainty Federal and State Policies Economic Development Public Support Green Power Energy Security Carbon Risk

42 Key Aspects of Development Project Development Social Acceptance Land Control Wind Studies and Wind Assessment Report Permits Land Use Environmental FAA Transmission Studies and Interconnection Power Purchase or Project Sales Agreement Taken From Dale Osborn

43 Land Control Required Rights Ingress and Egress Wind study, project construction and operation rights Transmit the energy and RECs from the site Term Initial Period Operational Period Landowner Compensation Royalty or Fixed Floor payment Reclamation Insurance Property Tax Site Plan Wind Study Installation of a met tower Measures wind speed and direction, temperature Instruments generally installed at 60m, 50m and 40 or 30m Good tower for installing bat monitoring devices as well No electrical service is required Measurements must occur for at least one year Ten minute increments Critical data as it determines output projections for wind facility Must be analyzed by Certified Meteorologist - suitable for Due Diligence Review

44 Permits Land use Governed by County Commissioners through zoning ordinances or Conditional/Special Use Permits. Governs: Permitting is a public process with hearings and citizen input Opponents attempt to create perceptions with unsubstantiated claims Critical process includes the county planning department Permits can be issued in 90 days to one year Permits Environmental Process and Studies vary widely based on: Public or private land State rules and regulations County rules and regulations Citizenry education Typical Studies Include Critical Issues Assessment Flora and Fauna Studies (very site specific) Cultural and Archeological Reviews

45 Permits Environmental Key Laws and Enforcement Agencies National Environmental Policy Act (NEPA) Bald and Golden Eagle Protection Act Migratory Bird Protection Act National Historic Preservation Act Native American Graves Protection and Repatriation Act Federal Aviation Administration) All towers above 200 feet must be lighted - regularly above 400 feet FAA is responsible for all such towers (database) Each wind turbine must apply for and receive a Determination of No Hazard Form 7460 Has become a very Contentious Issue Transmission Studies and Access Regulated by the Federal Energy Regulatory Commission (FERC) Transmission Management Varies by Region Kansas is in the Southwest Power Pool (SPP) Colorado and most Western State are managed by Individual Utilities Under FERC Guidelines there are Three Studies To Sell the Power, a Project must be able to deliver to the buyer Economically, it is always better to sell the power to the utility to whom the project is interconnected; Often not Possible

46 Power Purchase (PPA) or Project Sales Agreement This is the Financeable Document PPA must be with Creditworthy Utility Typically fixed price for years Price may escalate or be flat for the term Utility purchases what is produced, when it is produced It is the utility s best interest to own the projects Financing Tax Credits Have Great Value (not a special deal) Passed through in a lower Cost of Energy (PPA) Tax Credits to expire in 2012 Only project owners get the tax credits Financing is non-recourse Generally seeking 9% after tax unlevered ROR (20 years) Developers and buyers have project pro-forma models which correlate

47 Further Information / References Web Based: American Wind Energy Association Wind Powering America windpoweringamerica/ Danish Wind Industry Association guided tour and information Wind Technologies Market Report. windandhydro/pdfs/2009_wind_technologies_market_report.pdf Publications: Ackermann, T. (Ed s), Wind Power in Power Systems, John Wiley and Sons, west Sussex, England, (2005). Wind Energy Explained, J. F. Manwell, J. G. McGowan, A. L. Rogers John Wiley & Sons Ltd Paul Gipe, Wind Energy Basics: A Guide to Small and Micro Wind Systems, Real Goods Solar Living Book. AWS Scientific Inc. Wind Resource Assessment Handbook produced by for the National Renewable Energy Laboratory, Subcontract number TAT , 1997 Thanks to: Ken Starcher, Alternative Energy Institute, West Texas A&M University

48 Carpe Ventem ` Charles Newcomb Section Manager Wind and Water Deployment National Wind Technology Center charles.newcomb@nrel.gov 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