Operated for the U.S. Department of Energy by Midwest Research Institute • Battelle • Bechtel

National Renewable Energy Laboratory

Small Wind PowerFor South Dakota

Jim GreenNational Wind Technology Center

Wind Power History800-900 years ago,

in Europe140 years ago,water-pumpingwind mills

70 years ago,electric power

1400-1800 years ago,in the Middle East

Small Wind Turbines are Different

• Large Turbines (600-1800 kW)• Installed in Windfarms, 10 - 100 MW• Provide Low Cost Power to the Grid• < $1,000/kW• Require 6 m/s (13 mph) Average Wind

Speeds

• Small Turbines (0.3-50 kW)• Installed Off-Grid or at On-Grid Facilities• $2,000-6,000/kW• Designed for Reliability / Low Maintenance• Require 4 m/s (9 mph) Average

300 kW WindTurbine

10 kW WindTurbine

Small Wind Turbines

Bergey EXCEL, 10 kW

• Configuration: Up-wind, horizontal axis,2 or 3 blades, aligned with wind by the tail

• Blades: Fiber-reinforced plastics, fixedpitch, either twisted/tapered, or straight(pultruded)

• Generator: Direct-drive permanent magnetalternator, no brushes, 3-phase AC,variable-speed operation

• Overspeed Protection: Passive furling(rotor turns out of the wind), no brakes

• Result:– Simple, rugged design– Only 2–4 moving parts– Little regular maintenance required

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Small Wind Turbine Towers• Guyed lattice and tube towers

are the least expensive andmost commonly used towersfor small wind turbines

• Adequate space is needed forthe guy wires and their anchors

• Free-standing towers are usedwhere space is limited

Tilt-Up Towers

• Tilt-up versions of guyed towersare available for easierinstallation and maintenance

• Uses 4 guy wires instead of 3

The Wind Turbine Controller

• Battery-Charging– Converts AC power to DC for battery-charging– Regulates the battery voltage to prevent over-charging

• When the battery is fully charged:– Power is diverted to another load, or …– The rotor is unloaded and allowed to

“freewheel”

• Grid Interconnection– “Inverter,” converts the power to

constant frequency 60 Hz AC

• UL label may be required

Small Wind TurbineMaintenance and Lifetime

• “Low maintenance” not “no maintenance”– Annual inspection and maintenance– Tightening bolts and electrical connections, inspecting

slip rings, checking for corrosion, checking guy wiretension, inspecting/replacing leading-edge tape, etc.

– Beyond 10 years: blade or bearing replacement maybe needed

• Lifetimes of 10 to 20 years are possible withproper installation and annual maintenance

“A wind turbine will see as many operating hours inone year as an automobile will see in 200,000 miles!”

Small Wind Turbine Cost & Warranties

• Initial cost is between $2,000 and $6,000/kW for asmall wind turbine, controller, and tower

• There is a trade-off between the incremental cost ofa taller tower and increased wind turbineperformance

• Buyers must make judgements between initial costand rugged/durable design.

• Warranties– 5 years typical– Coverage of “materials and workmanship”

Zoning for Your Wind Turbine

• Short towers, 30–35 ft, can be installed with only abuilding permit

• Taller towers often require a “special use review” by thecounty commissioners

• Zoning issues include noise, obstruction of views,safety, and setbacks

• Zoning approval may be difficult or impossible to get forurban and suburban locations, is less a problem in rurallocations

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Estimation of Annual Energy Production

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0.8

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1.2

1.4

1.6

1.8

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 23 23 24 25

Wind Speed (m/s)

Pow

er (k

W)

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400

600

800

1000

1200

1400

1600

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25Wind Speed (m/s)

Tim

e (H

ours

)

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50

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450

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

Wind Speed (m/s)

Ener

gy (k

Wh)

PowerCurve

Frequency ofOccurrence

Annual EnergyProduction

“Hot Tips” on Wind Energy

• “Buy Reliability”“Based on experience, I side with the ‘school of heavy metal,’those who believe that beefiness of components is directlyrelated to the longevity of the equipment.” M. Sagrillo, smallwind turbine expert

“Hot Tips” on Wind Energy

• “Buy Reliability”“Based on experience, I side with the ‘school of heavy metal,’those who believe that beefiness of components is directlyrelated to the longevity of the equipment.” M. Sagrillo, smallwind turbine expert

• “Taller is Better”Taller towers give better performance due to smoother windand higher wind speeds

Wind Speed and Power Increase withHeight Above the Ground

1.0

1.5

2.0

2.5

3.0

3.5

0 50 100 150 200 250Tower Height, ft

Incr

ease

Com

pare

d to

30

ft

Wind Power IncreaseWind Speed Increase

Alpha = 0.2

“Hot Tips” on Wind Energy

• “Buy Reliability”“Based on experience, I side with the ‘school of heavy metal,’those who believe that beefiness of components is directlyrelated to the longevity of the equipment.” M. Sagrillo, smallwind turbine expert

• “Taller Is Better”Taller towers give better performance due to smoother windand higher wind speeds

• “Pay Attention To Micro-Siting”For best performance, locate wind turbines above and awayfrom obstructions to the wind

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Micro-Siting Example:Obstruction of the Wind by a Building

Prevailing wind

H

2H 20H

2HRegionof highlydisturbed

flow

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Questions?

• Ranch near Wheeler, TX

• Water-pumping for 120 headof cattle

• Whisper 1000 wind turbine,1 kW, 9 ft rotor, 30 ft tower

Off-GridWind Water-Pumping

Case Study:Off-Grid Stock Tank Heating with Wind

• University of Wyoming

• Bergey Windpower 1500 windturbine, 1500 W, 10 ft rotor

Case Study:Off-Grid Home with Wind/PV System

• West of Boulder, CO, at 9,000 ft• Bergey 1500 wind turbine, 1.5 kW, 70 ft tower• Solarex PV panels, 480 W• 24 VDC battery, 375 Ah• Onan generator, propane-fueled,

3 kW (at altitude)• Trace inverter, 120 VAC, 1 phase• Propane used for range, refrigeration,

space heat, hot water (w/solar pre-heat)• First wind turbine installed in 1978, fourth wind

turbine now in service• PV installed 1984 w/ tax credits• System cost about $20,000

120

1/4 mile

Source: PG&E

Line

cos

t (pr

esen

t val

ue, $

x 1

000)

100

80

60

40

20

01/2 mile 3/4 mile 1 mile

$12/ft

$10/ft

$8/ft

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Costs for Line Extensions

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Hybrid Power SystemsCombine multiple sources to deliver reliable electric power

Regulation and conversion

PV modules

Battery bank

Load

P171-A339918

AC or DC

Wind turbine

Generator

Solar and Wind Resources are Complimentary400

350

300

250

200

150

100Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Hou

rs o

f sun

shin

e or

ave

rage

win

d po

wer

(Wat

ts/m

2 )

Hours of sunshine/month

Average wind power/month

Data from SE Iowa

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Do I Use Wind or PV?

Kansas SolutionsLarge 7.519 kWh/d Optimal

First PV-only System

Difference (PV/Opt.)

PV (kW) 0.0 1.0

BWC XL.1 (#) 2 0

Diesel (kW) 1 1

Battery (kWh) 18 18

Inverter (kW) 2 2Renewable % 89% 48%Generator Run Time 729 2015 176%Diesel Fuel Usage 386 1074 178%

Total NPC $20,940 $28,349 35%

• Optimal system in central Kansas:wind/generator hybrid, no PV

• Analysis done with HOMERsoftware