Outline. Introduction to Wind Energy. US Wind Energy Installations. ME 483 Alternative Energy Engineering II 1

Transcription

1 Wind Power Introduction February, Introduction to Wind Energy Larry Caretto Mechanical Engineering 48 Alternative Energy Engineering II February, Outline Current use of wind energy Advantages and disadvantages of wind Wind turbine components Calculation of wind power Wind power coefficient, c p Power dependence on V Probability analysis of wind Economics and R&D tasks Organizations and companies 4. US Renewable Energy Use -7 8 US Electric Net Summer Capacity (EIA Data).5 6 Energy Use (quads) Capacity (GW) Conventional Hydroelectric Geothermal Energy Biomass Solar Energy Wind Energy Energy Type 4 Biomass Geothermal Solar Wind Total/ 4 US Wind Energy Installations US Wind Power Locations Actual 9: 9,9 MW installed; Cumulative 5,59 MW /reports/4q9.pdf DOE May 8 report: ME 48 Alternative Energy Engineering II

2 Wind Power Introduction February, World Wind Energy Association European notation uses a decimal point as the thousands separator World Wind Energy Association forecasts 6 GW by Currently generating over % of world electricity European data uses. instead of, as thousands separator 7 UK Wind Capacity (GW) 8 Germany Spain USA India Denmark China Italy Countries in rank order for Portugal France Netherlands Canada Japan Austria Australia Others /worldwindenergyreport8_s.pdf Contribution of Wind Wind Advantages 9 No atmospheric emissions that cause pollution or greenhouse gasses. No fuel costs One of the lowest-priced renewable energy technologies available today (4 to 6 cents per kilowatt-hour Sites can coexist with on farms or ranches benefiting the economy in rural areas Wind Disadvantages Requires a higher initial investment than fossil-fueled generators. Wind is intermittent not always available when electricity is needed cannot be stored (unless batteries are used) not all winds can be harnessed to meet the timing of electricity demands. Wind Disadvantages II Good sites are often far from cities where the electricity is needed. Other uses for the land may be more highly valued than electricity generation. Concern over the noise produced by the rotor blades, aesthetic (visual) impacts, and sometimes birds have been killed Most problems greatly reduced by new technology or by better siting of wind plants. ME 48 Alternative Energy Engineering II

3 Wind Power Introduction February, NEG Micon MW turbine Hagesholm, Denmark Commissioned August 999 Rotor diameter 7 m Tower height 68 m Active stall control percent_wind_energy_ report_revoct8.pdf Figure - 4 No longer used faq/basicop.html Blades Turbine blades as airfoils Lift becomes force in direction of rotation 5 faq/basiccf.html 6 energy_report_revoct8.pdf windandhydro/wind_how.html ME 48 Alternative Energy Engineering II

4 Wind Power Introduction February, Wind Turbine Components Anemometer: Measures the wind speed for system control Brake: A disc brake to stop the rotor in emergencies Controller: starts up the machine at wind speed about 8 to 6 mph and shuts off the machine at about 65 mph to avoid system damage Wind Turbine Components II Gear box: connects the low-speed (- 6 rpm) shaft to the high-speed ( to 5 rpm) shaft required by generator Generator: produces 6-cycle AC electricity Nacelle: contains the gear box, lowand high-speed shafts, generator, controller, and brake 9 Wind Turbine Components III Pitch: Blades are pitched (turned) out of the wind when winds too high or too low to produce electricity Rotor: The blades and the hub together are called the rotor Tower: Towers are made from tubular steel Wind direction: Upwind" turbines operate facing into the wind Wind Turbine Components IV Wind direction: Downwind" turbines operate facing away from the wind Wind vane: Measures wind direction and directs yaw drive to orient the turbine with respect to the wind Yaw drive: Required on upwind turbines to keep them facing into wind Yaw motor: Powers the yaw drive Wind Power Power in incoming air m& e m& V / (ρva)v / ρav / P Air density, ρ. kg/m A swept area of rotor π(d rotor ) /4 V wind velocity Simple model of rotors as a actuator disk At plane of actuator disk pressure change provides rotational power Analyze flow in stream tube starting far upstream from rotor and ending far downstream from it Wind Power II Apply Bernoulli equation for frictionless flow from far upstream to just before disk and just after disk to far downstream Thrust to rotor is difference in pressure at rotor times rotor area Use continuity equation for streamtube Use momentum balance equation to determine force delivered to rotor Power delivered to rotor force times velocity See text for full derivation 4 ME 48 Alternative Energy Engineering II 4

5 Wind Power Introduction February, Wind Power III Result for actual power, P ρa(v + V )(V V )/4 V upstream velocity (before turbine) V downstream velocity c p power coefficient turbine power divided by power in wind c p ( + V )( V V ) ρa V 4 V V + VV ρav V P P V V 5 c p V Betz Limit: c p.max 6/7 V VV r Find r for Maximum c p + VV V dc p dr r + r ( r + r) V r V r r max + rmax r max Called Betz limit after person who first did computation in 99 max 6 ( ). 59 c p max Wind Turbine Power Coefficient Effect of V Dependence.7 Power Coefficient Cp Energy calculations assume Betz c p and a m rotor diameter Velocity Ratio (V /V ) 7 and for plot 8 Wind Classes ( m) Effect of Wind Variations Class power/area(w/m ) mim max Speed(m/s)/(mph) min max 4.4/ /9.8 5./.5 5./.5 5.6/.5 5.6/.5 6./.4 6./.4 6.4/4. 6.4/4. 7./5.7 7./ /. 9 Data for three locations below show same average wind speed (6.m/s) but increasing power density (W/m ) resulting in increasing wind class Culebra, Puerto Rico 6. 4 Tiana Beach, New York San Gorgonio, California Consistent wind speeds provide more energy at same average speed ME 48 Alternative Energy Engineering II 5

6 Wind Power Introduction February, Wind Classes (5 m) Class power/area(w/m ) Speed(m/s)/(mph) min max min max 5.6/.5 5.6/.5 6.4/ /4. 7./ / / /6.8 8./ / / /9.7.9/ Wind Power Efficiency Incoming wind at m/s has,46 kw Rotor with d 6 m and c p.44 produces,4 kw (,97 kw to generator) Generator produces,5 kw of which kw are delivered to transformer Rated c p ( kw)/(46 kw).94,76 kw delivered to grid from transformer Usual grid loss is about 8% Eric Hau, Wind Turbines, Springer, 5 Wind Turbine Size General ternds for wind turbines Power is proportional to blade area or rotor diameter squared Volume, weight and material cost is proportional to rotor diameter cubed There should be some optimum size above which increases in power will cost more than for smaller machines Power continues to increase, however, due to improvements in materials and design 6 ME 48 Alternative Energy Engineering II 6

7 Wind Power Introduction February, Evolution of Blade Designs Turbine Size History wind_energy_report_revoct8.pdf Figure -7 7 DOE Wind Annual 7, 8 Wind Energy R&D Variable speed generators improve generation over a range of wind speeds Gearless turbines that reduce the turbine operating costs Lighter tower structures allowed because new turbines and generators reduce or better distribute stresses and strains Wind Energy R&D II Smart controls and power electronics enable remote operation and monitoring of wind turbines enable remote corrective action in response to system operational problems. Turbine designs where power electronics are needed to maintain power quality also have benefited from a reduction in component costs 9 4 AWEA Economics 5 MW wind farm with class 4 winds Capital cost: $65 million Annual power: 5 GWh (5% capacity) Annual gross: $6. million (@ 4 /kwh) Annual expenses: $8. million Expense for debt service (6% debt finance) at 9.5% for 5 years $4.98 million/year (6% of total expenses) Distribution costs: $.8 million/year 4 AWEA Economics II O&M costs: $.664 million/year Land costs: $.45 million/year Administration: $.45/year Annual Loss: $.7 million Producer tax credit (.8 /kwh): $.76 million Income after PTC: $.588 million Annual return on equity investment.% for 5 years 4 ME 48 Alternative Energy Engineering II 7

8 Wind Power Introduction February, Residential Wind Turbines Installed in rural areas and outer suburban properties greater than acre Installed cost $6, to $, Rule of thumb: average wind speed mph and electricity cost /kwh Payback period 6 to 5 years 8 to ft tower required Quieter than a washing machine 4 Organizations American Wind Energy Association World Wind Energy Association National Renewable Energy Laboratory DOE wind and hydro programs Global Wind Energy Council 44 Companies and Sizes DOE Wind Annual 7, 45 DOE Wind Annual 7, 46 Sample Companies Vestas (includes former NEG Micon) Headquarters in Denmark March, 9 website claims installation of 8, wind turbines in 6 countries for % market share US office in Portland, OR Range of products from 85 kw to. MW Previously had 4.5 MW turbine 47 Sample Companies II General Electric A natural fit for a company that works in both energy systems and turbomachinery Purchased company initially founded as Zond energy from Enron after the financial collapse of Enron 5 installations.9 GW (6.9%).5 MW,.5 MW and.6 MW turbines for onshore and offshore applications 48 ME 48 Alternative Energy Engineering II 8

9 Wind Power Introduction February, Sample Companies III Siemens Locations worldwide MW and.6 MW turbines for onshore and offshore applications Total installed capacity on web site on March, 9 is 7,79 turbines with a total of 8.8 GW capacity Sample Companies IV Clipper 65 Carpentaria Avenue, Santa Barbara Founded in by James Dehlsen who founded Zond in 98 Main product is Liberty Wind Turbine.5 MW with rotor diameters between 89 m and 99 m depending on wind class Three blades, variable speed drive ( rpm) Current Technology Turbines power range from just under MW to -5 MW Larger rotor diameters used for larger peak power machines to get higher capacity factors Typical rotor diameters on modern machines range from 6 to 9 m Seek reductions in weight by new materials and design integration 5 ME 48 Alternative Energy Engineering II 9