Commercial Wind Turbine Site Assessment Wes Slaymaker, P.E., - - PowerPoint PPT Presentation

Commercial Wind Turbine Site Assessment

Wes Slaymaker, P.E., Windustry Project Engineer

Focus on Energy- Training the Trainers Madison, Wisconsin February 10, 2005

2105 First Avenue South • Minneapolis, MN • (612) 870-3464 • wslaymaker@windustry.org

Commercial Wind Turbine Site Assessment

Outline:

• Overview of myself and Windustry
• Site Assessment (morning)
• Monitoring at Site (early afternoon)
• Siting of Commercial Turbines

(later afternoon)

• Wind Mapping Methods

(15 minute discussion at end of talk)

Wes Slaymaker, P.E.

• Project Engineer- have

worked for several wind developers in the Midwest developing wind projects from 1 to 100 turbines.

• Working to educate the

public on this new and exciting industry.

About Windustry

• Creating an understanding of wind energy
• pportunities for rural economic benefit.
• Non-profit based in Minneapolis, MN.
• Outreach and technical support for rural

landowners and communities in Midwest.

• www.Windustry.org
• Wind Farmers Network

Windustry’s

Wind Farmers Network

• A network for landowners, farmers, ranchers,

farm organizations, businesses, community leaders and others.

• A membership-based exchange for case

studies, individual experiences, lessons learned, negotiating points, and more.

• Online at www.windfarmersnetwork.org

Commercial Wind Turbine Site Assessment

What I will provide:

• Modest entertainment.
• 145 slide presentation- with all slides copied

for you, plus full page copies of map exercises.

• Real world examples from my experience.

Commercial Wind Turbine Site Assessment

What I will NOT provide:

• Complete details of a wind meteorologist’s work,

I’m not one.

• Expert knowledge on wind characteristics and

terrain for all parts of WI. (I’ve worked in a few areas- it’s a big state!)

• One right answer- fluids such as wind never behave

the same way twice, it’s an inexact science.

Commercial Wind Turbine Site Assessment

Small Turbines vs. Commercial Scale Turbines

• Commercial turbines must be financed and

require assured, significant returns.

1. Must know the wind resource, +/- 5% or better. 2. Need long term power contract. 3. Owner spends a lot of time getting project financed.

• Commercial turbines sell all their energy- need

robust interconnect, ability to use power locally,

• r transmit to load.

Commercial Wind Turbine Site Assessment

Small Turbines vs. Commercial Scale Turbines

• Commercial turbines need to be sited in the best

resource, not necessarily on the owner’s property!

• The need for an accurate turbine production

estimate requires extensive wind monitoring and data analysis. These points are the basis for this workshop…

Site Assessment

• What makes the

wind?

• Wind Prospecting
• Siting

Considerations

• Orography

Site Assessment

What makes the wind?

• Global wind

circulation.

• Global patterns

not much use for WI wind predictions.

Giddyup horse latitudes?- no wind at 30o North of the equator?

Site Assessment

What makes the wind?

• Isobars of

pressure.

• Wind flows

from areas of high pressure, to lower pressure.

• This is the

predominant wind in the Midwest.

A new high or low every few days.

Site Assessment

What makes the wind?

*three regions of interest for wind development in WI.

• Wisconsin has

areas with more annual wind power due to weather patterns and Great Lakes effects.

• Wind speed is

not just a function of elevation and topography.

Site Assessment

What makes the wind?

Local compensation winds:

• Caused by differential heating, most

prominent near large bodies of water.

• Can create additional wind energy beyond

what is produced by the large weather systems.

• Niagara escarpment wind turbines and those

near Great Lakes benefit from this effect.

Site Assessment

What makes the wind?

Surface Wind:

• Two conditions in the atmosphere (stable and

unstable) caused by the sun heating the ground and air.

– Stable air is when air is cooling fast and falling, can have sharp boundary layer (at night). – Unstable air has rising and falling air- turbulence. – Neutral air is when air is neither rising or falling.

Site Assessment

What makes the wind?

Nocturnal Wind Shear:

• At night a stable air mass below can have

boundary layer 60-150m above ground.

• There can be much higher winds above this

boundary layer.

• Can provide 10-20% more wind energy than
• riginally predicted.

Site Assessment

What makes the wind?

Vertical wind speed gradient & roughness:

• Wind speeds increase

with height above the ground.

• The more

“roughness” or

• bstacles to the wind,

the sharper the gradient.

Site Assessment

What makes the wind?

Land-Atmosphere Interactions:

• Local land features create micro sites with

better wind potential, best example is a ridge perpendicular to predominant wind direction.

• These will be the focus of much of today’s

commercial turbine siting discussion.

Site Assessment

Wind Prospecting

Some people have an intuitive sense for how to capture energy in the wind…

Site Assessment

Wind Prospecting

Big Picture View:

• Tall ridges clear of trees or obstacles in windy

parts of the state.

• Tall ridges clear of trees or obstacles in windy

parts of the state.

• Tall ridges clear of trees or obstacles in windy

parts of the state.

Sample Site 1: Oriska, ND

*Project Location

Site Assessment

Wind Prospecting

Site 2: Wilmont, MN

* Project Location

Site Assessment

Wind Prospecting

Site 3: Elk River, MN

* Project Location

Site Assessment

Wind Prospecting

Site Assessment

Wind Prospecting: Driving around

1. Clear of trees and obstacles greater than 40 ft tall for >2500 ft. 2. Location on a ridge perpendicular to predominant wind direction. 3. Location on top or downwind side

• f the ridge.

4. Ridgeline with moderate slope preferred.

Site Assessment

Wind Prospecting: Driving around

Flagging:

• Uses vegetation to

show predominant wind direction and intensity.

• Of limited use in

Wisconsin.

Site Assessment

Wind Prospecting: Topo Maps

What makes a good site in WI?

1. Areas along Niagara escarpment, from Green Bay to IL border. 2. Areas with land features extending higher than average elevation. 3. Southern half of state. 4. Locations closer to Lake Michigan.

Site Assessment

Wind Prospecting: Topo Maps

414

Tall hill on the Niagara escarpment was best public met tower site in WI, 6.7 m/s (15 mph) at 40m.

Site Assessment

Wind Prospecting: Topo Maps

Tall hill on the Niagara escarpment was best public met tower site in WI, 6.7 m/s (15 mph) at 40m.

Site Assessment

Wind Prospecting: Topo Maps

Significant ridge- 5.7 m/s (12.8 mph) at 40m Lowest wind shear- 0.20 from 25-60m

Site Assessment

Wind Prospecting: Topo Maps

Flat area near Lake MI-5.7 m/s (12.8 mph) at 40m Highest wind shear- 0.39 from 25-60m

Site Assessment

Wind Prospecting: Topo Maps

Tips:

• You can get all topos at

www.dnr.state.wi.us/maps/gis/datadrg.html

• Recent aerial photos can assist with site

reconnaissance at

www.geography.wisc.edu/sco/orthocat/index.php

Site Assessment

Siting Considerations

Surface Roughness:

• Roughness of water- .01 cm
• Roughness of short grass- 1 cm
• Roughness of tall grass or crops- 25 cm
• Roughness of forest or city- 1-4 m
• Roughness of brick wall- infinity

*Cannot be determined visually- must be measured

Site Assessment

Siting Considerations

Surface Roughness:

• The formula used most often for wind speed

increase with height- S/So=(H/Ho)α

• Alpha (α) changes with different surface

roughness, often assumed to be 1/7 (0.14) but can increase to as high as ¼ (0.25) for areas with forests or taller buildings

Site Assessment

Siting Considerations

Obstacles:

• Foremost consideration in the Midwest is TREE

cover- avoid like the plague!

• Old rule of thumb for trees of minimum 30 feet

higher than treetops won’t apply for large turbines (that’s a small turbine turbulence rule).

• Want ½ mile from tree groves as a rule, turbulence

robs a lot of energy from a turbine.

Site Assessment

Siting Considerations

Obstacles:

• Structures under 40 feet tall, OK.
• Scraggly fence row trees, OK.
• Turbine setbacks from roads and property

boundaries helps assure no impact from more turbines sited later on adjacent properties (minimum 1.1 turbine height).

Site Assessment

Siting Considerations: Hills

• Hills offer the best wind acceleration potential in

the Midwest when they are elongated ridges perpendicular to flow of wind.

• A nob hill has less influence on wind speed, mainly

provides increase in elevation.

• Turbulence concerns from cliffs and steep terrain

not often a concern in the Midwest.

• Edge of ridges also offers acceleration of wind and

good sites.

• Best wind is on top and just on the lee side of the

ridge (for gentle slopes).

Site Assessment

Siting Considerations: Hills

Graphic showing acceleration

• ver hills

with slopes

• f 17%,

25%, and 50%.

Source: US DOE 1978 Wind Power for Farms, Homes and Small Industry

Site Assessment

Siting Considerations: Valleys

• Valleys in Midwest have lower wind resource,

I’m not aware of any major channeling flow worth tapping .

• Large mountains are needed to funnel wind

through valleys.

• A valley can reduce boundary layer/friction

effects so wind speeds are higher closer to the ground (of note for small turbine project).

Site Assessment

Siting Considerations: Valley Exception?

* Project Location Turbines located on upslope benefit from “channeling” effect of ‘shores of Glacial Lake Agassiz’.

Site Assessment

Siting Considerations: Valley Exception?

Site Assessment

Siting Considerations:

Turbulence/ shear Turbine manufacturer’s concerns:

• Maximum inflow angle- direction of wind off
• f perpendicular to blades (<8 degrees*).
• Maximum turbulence intensity (16%*)
• Maximum wind shear acting on blade area

(.20*)

*Figures in parenthesis are for Vestas V82- 1650kW

Site Assessment

Siting Considerations:

How complicated is too complicated?

Q: Where do we put the turbine in this picture? A: You Don’t

(that’s downtown Milwaukee in the background)

Site Assessment

Orography: Calculating losses

• Significant tree cover- deduct 20-30% from

annual kilowatt-hour prediction.

• Large obstacle- need to use hourly wind

speed and direction data to subtract power from winds in the direction of obstacle.

Site Assessment

Orography: Turbine layout

• Orient turbines along the ridge, better to

place down slope than upslope.

• Place turbines so obstacles are on side with

least amount of wind power (often the east).

Site Assessment

Orography: Turbine layout

Montfort turbine array, all in a row heading East- West, no obstacles nearby.

Site Assessment

Orography: Losses from two

turbines sited near each other

• Typical recommendation to minimize “array” loss in

Midwest is 3-5 rotor diameters apart parallel to predominant wind direction and 7-10 rotor diameters apart perpendicular to dominant wind.

• That’s approx. 1,000-1,400 ft apart in rows and

2,250-3,400 ft apart otherwise- for an 82 meter rotor (268 ft) wind turbine (the Montfort wind farm’s spacing appears to be about 600-700 feet in rows, for a 70.5m rotor (231 ft).

Site Assessment

Orography: Losses from two

turbines sited near each other (cont.)

• Typical array losses for a wind project are 2-

4%, with multiple turbine interference

• possible. One turbine array loss of 1-2%

expected if you follow the previous page’s guidelines.

• When in doubt, keep them far apart.

Site Assessment

Orography: Assess a site

• When someone’s “gotta have it on their land”, use

conservative estimates (20% below expected from nearby anemometry site) if the land contains mixed trees, and gently rolling terrain (If its down the hill and wooded, use even “worse” numbers).

• Learn from MN Metro area wind studies and

turbines (capacity factors are half of those sited further South or West).

• Monitor at the site with minimum 50 meter tower,
• r hire WindLogics for power production estimate.

Monitoring at Site

• Guiding Principles
• Data Quantity and

Quality

• Monitoring

Instruments

• Data Validation,

Processing, and Reporting

Monitoring at Site

Guiding Principles

On site data is the preferred, the following are next best:

• Nearby (within 10-15 miles and in similar terrain

regime) public met data from tower >40m.

• Windlogics or similar wind prediction using a lot of

computer power and huge wind database.

• Everything else is just a guess.

Monitoring at Site

Guiding Principles: Strategy

• Get minimum 6 months of good wind data

(>80% recovery rate for the data), best to get 6 months with winter and summer represented.

• Correlate with a long term nearby data source

(airport data from NCDC).

Monitoring at Site

Guiding Principles: Strategy

• NCDC website for hourly data.
• www.ncdc.noaa.gov/oa/climate/climatedata.

html#HOURLY.

• 67 sites in Wisconsin to select from.
• Costs $20 per year of data.
• Retrieve from ftp site- large files.

Monitoring at Site

Guiding Principles:

Strategy for met tower

• Rent or buy and install a met tower, 40 meter

possible for flat terrain and few obstacles within ½

• mile. Otherwise, 50m or 60m.
• Get long booms (the fatter the tower the longer the

boom, minimum 3 feet) for anemometers and place

• n upwind side of tower.
• Check data often to avoid losing time due to lack of

data or bad data.

Monitoring at Site

Guiding Principles

• Lunch Break 12:00-12:30 pm

Eat, drink and be merry, but be back at 12:30 pm!

Monitoring at Site

Data Quantity and Quality

Measurements:

• Wind speed- at 10 m intervals, skipping even

intervals such as 20m, or 40m on a 50m tower.

• Wind direction- two vanes, near top and mid height.
• Temperature- measured near the logger, sensor in

separate box (optional).

• Barometric pressure- measured at logger (optional).

Monitoring at Site

Data Quantity and Quality

Measurements- Temperature:

• Temperature varies with height

Tp(z) = Tg – Rp(z-zg) Tg = temperature at ground level Rp = lapse rate 0.0065oC/m (z)- elevation above ground in meters

• Example:

T (50m)= 20°C – 0.0065*(50m-0m) = 19.67°C

Monitoring at Site

Data Quantity and Quality

Measurements:

• Vertical wind speed- a nice thing to have to

demonstrate to turbine manufacturer that the “inflow” angle is <8% (or whatever they require)- typically not measured.

• Use R.M. Young vertical prop wind

anemometer or similar.

Monitoring at Site

Data Quantity and Quality

sitenyeamo dayhouminu temp 10m anem120m anem239m anem340m anem4vane1_1vane2_39m 700 3 12 15 14 10 18.2 181 89 700 3 12 15 14 20 18.2 179 86 700 3 12 15 14 30 18.2 179 85 700 3 12 15 14 40 18.2 179 85 700 3 12 15 14 50 18.2 0.01 0.14 179 85 700 3 12 15 15 0 18.2 179 85 700 3 12 15 15 10 18.2 0.02 0.19 0.07 179 85 700 3 12 15 15 20 18.2 0.25 0.6 0.07 179 85 700 3 12 15 15 30 18.2 0.73 0.89 0.12 0.45 0.22 0.58 179 85 700 3 12 15 15 40 18.2 0.9 0.93 0.22 0.58 0.22 0.58 179 85 700 3 12 15 15 50 18.2 1.63 0.78 0.98 0.85 0.17 0.51 1.29 0.89 179 85 700 3 12 15 16 0 18.2 1.91 0.82 1.39 0.82 0.65 0.85 1.74 0.89 179 85 700 3 12 15 16 10 18.2 2.51 0.85 2.04 0.69 1.56 0.63 2.52 0.85 179 85 700 3 12 15 16 20 17.4 1.98 1.21 1.92 0.85 1.24 1.11 2.1 1.02 179 85 700 3 12 15 16 30 17.4 3.91 1.06 3.31 0.82 3.34 0.82 3.66 0.78 179 84 700 3 12 15 16 40 17.4 3.86 0.85 3.18 0.82 3.19 0.82 3.75 0.78 179 82 700 3 12 15 16 50 17.4 3.64 0.72 3.18 0.78 3.15 0.89 3.82 0.82 179 82 700 3 12 15 17 0 17.4 3.26 1.02 2.94 0.93 2.74 0.89 3.57 0.89 179 82 700 3 12 15 17 10 17.4 3.56 0.89 3.09 0.85 2.8 0.89 3.71 0.82 179 82 700 3 12 15 17 20 17.4 2.77 0.85 2.38 0.85 1.85 0.82 2.98 0.82 179 82 700 3 12 15 17 30 17.4 2.86 0.93 2.41 0.93 1.75 1.02 2.91 0.97 179 82 700 3 12 15 17 40 17.4 1.3 0.93 0.82 0.89 0.03 0.23 0.95 0.97 179 82 700 3 12 15 17 50 17.4 1.92 0.82 1.44 0.89 0.37 0.72 1.22 1.21 179 82 700 3 12 15 18 0 17.4 3.04 0.78 2.66 0.89 2.54 1.06 3.4 0.89 180 82 700 3 12 15 18 10 17.4 3.5 0.75 2.99 0.82 3 0.93 3.64 0.82 179 82 700 3 12 15 18 20 17.4 3.54 1.16 3 0.89 2.92 0.97 3.57 0.89 179 82 700 3 12 15 18 30 17.4 3.55 1.21 3.23 0.89 3.25 0.97 3.8 0.93 179 82 700 3 12 15 18 40 17.4 2.8 0.89 2.48 0.89 2.39 0.89 3.12 0.85 179 82 700 3 12 15 18 50 17.4 2.9 0.89 2.59 0.93 2.35 0.93 3.25 1.02 179 82 700 3 12 15 19 0 17.4 2.9 0.85 2.5 0.85 2.15 0.85 3.14 0.72 179 82

Sample

• f raw

wind data.

Monitoring at Site

Data Quantity and Quality

Parameters:

• Speed- sampling rate every 2 seconds and

averaged.

• Standard deviation-used for turbulence.
• Max and min.- not often part of dataset.

Some loggers store the 1 second or 10 second value.

Monitoring at Site

Data Quantity and Quality

Recording parameters and sampling interval:

• Standard is in metric units, client may prefer

English units.

• Sampling interval, 10 minutes is better, hourly

is acceptable.

• Wind vane often set North at 360 degrees.

Monitoring at Site

Data Quantity and Quality

Classification of Wind Sites- 50m Rayleigh distribution:

• Class I-

<12.5 mph (<5.6 m/s)

• Class II-

12.5-14.3 mph (5.6-6.4 m/s)

• Class III- 14.3-15.7 mph (6.4-7.0 m/s)
• Class IV- 15.7-16.8 mph (7.0-7.5 m/s)
• Class V-

16.8-17.9 mph (7.5-8.0 m/s)

• Class VI- 17.9-19.7 mph (8.0-8.8 m/s)

Need mid Class III or better winds for new turbines, for most projects to be economical/competitive.

Monitoring at Site

Data Quantity and Quality

Quality data assurance plan:

• IMPORTANT- check/download data often, much

good data is lost due to low batteries on logger, full card, or some other minor problem.

• Be sure all channels are programmed, and using

same units- verify outputs before leaving.

• If measuring temperature be sure the instrument is
• ut of direct sunlight and the “indirect heating”

effect.

Monitoring at Site

Data Quantity and Quality

Monitoring duration and data recovery:

• Absolute minimum of 3 months of good site data,

more typically need 6 months or more of data in a contiguous period.

• Need long term data to correlate with above

assumptions, otherwise 2 or more years site data needed.

• Data recovery rate of 60-70% or better required, would

like to see 90% or better.

Monitoring at Site

Monitoring Instruments: Sensors

Sensors- How accurate?

• Calibrated sensor solves this problem.
• Otherwise, anemometers often use frequency

signal, provides a fairly accurate translation to wind speed w/o calibration need.

• Directional sensors (wind vane) problems

arise more from confusion on orientation.

• +/- 0.2 mph (0.1 m/s)

Monitoring at Site

Monitoring Instruments: Sensors

Barometric Wind vane Temp.

Monitoring at Site

Monitoring Instruments: Sensors

Cup Anemometer Ultrasonic

Monitoring at Site

Monitoring Instruments

SODAR:

• SODAR- sonic detection and ranging uses acoustic

signals bounced from a ground unit up into the air and reflected back and captured to measure wind speed and direction.

• Units cost $40,000.
• Considered inaccurate as stand alone measuring

device; excellent device for detail studies of winds 50-200m high.

Monitoring at Site

Monitoring Instruments

Mini SODAR unit made by Aerovironment. Large met firms such as AWS Truewind and Windlogics have some of these units.

Monitoring at Site

Monitoring Instruments

Dataloggers and Power Supplies:

• Standard has been NRG Systems dataloggers,

they have 40m and 50m complete tower packages, $6-$8K.

• Many other dataloggers would be suitable.
• Most dataloggers run on 9V batteries, unless

barometric pressure sensor is needed, then need a larger battery and solar panel.

Monitoring at Site

Monitoring Instruments

Datalogger:

Campbell Scientific NRG

Monitoring at Site

Monitoring Instruments

Datalogger:

Wiring gets messy. NRG Term Reader used to verify instrument setup.

Monitoring at Site

Monitoring Instruments

Datalogger:

Note temp sensor location and cell phone antennae.

Monitoring at Site

Monitoring Instruments

Data Storage and Transfer Options:

• Most wind dataloggers have storage cards

that can be removed and plugged into a card reader to download to computer.

• Cell phone transfer of data is more expensive

and only recommended for those installing multiple towers.

Monitoring at Site

Monitoring Instruments

Monitoring Towers- Which height do I use?

• Tower height- taller is better. NRG tip up

towers now go to 60m tall. 60m complete system is $9,800 on their website. 50m system is $7,500 and 40m system is $5,500.

• If site is flat and open, then a 40m tower could

be used and a reasonable guess made on shear.

• Installation costs are from $2K-$3K and up.

Monitoring at Site

Monitoring Instruments

Monitoring Towers- Which height do I use?

Monitoring at Site

Monitoring Instruments

Monitoring Towers- cell tower use:

• Cell towers can provide heights up to and

beyond hub height (60-120m or 197’-394’).

• Many cell towers are managed by separate

firms that allow subleases for equipment.

• Average cost of $1,000-$1,500 for 1 year

lease.

• Need really long booms to avoid tower

effects.

Monitoring at Site

Monitoring Instruments

Cell tower used for met tower.

Monitoring at Site

Monitoring Instruments

Monitoring System Protection:

• Met tower is a wonderful lightning

rod, proper grounding using 6 foot long ground rods and large copper wire is required. Optical isolators are best protection for electronics

• Most met tower damage I’ve heard of is due

to tractors clipping the guy wires- mark those wires!

Monitoring at Site

Monitoring Instruments

Measurement reliability-

Biggest concern is loss of data/bad data from:

1. Icing 2. Batteries run out of juice 3. Datacard malfunctions 4. Datacard is lost after it is removed 5. Lightning fries equipment

Monitoring at Site

Monitoring Instruments

Measurement accuracy:

• Word is that the tower top

anemometer has a 2-3% speed up, and so a reduction in wind speed from this anemometer is needed.

• Tower shading must be accounted for, if there are

two instruments at each height, just use highest

• value. If only one instrument, have to filter out

wind from direction of the tower.

Monitoring at Site

Data Validation Processing, and Reporting

Methods:

• Big picture, either you are a spreadsheet,

database and math junkie, or you have a professional met firm analyze the data.

• You don’t have to do a full wind report to

get a reasonable production estimate- using the bin method and some educated guesses.

• Stay seated and I’ll fill your head…

Monitoring at Site

Data Validation Processing, and Reporting

Data Processing:

• Most data processing is done in the

software provided by the datalogger, and then additionally in a spreadsheet.

• Large data sets require database program to

handle all the records. A year of ten minute data is 52,560 records (Excel cannot handle multiple years).

Monitoring at Site

Data Validation Processing, and Reporting Data recovery (%):

• Try for >90% data recovery.
• Reasons for losses shown below:

Monitoring at Site

Data Validation Processing, and Reporting

Data recovery (%)-Reasons for losses:

• Malfunction

1. Lightning 2. Battery goes dead 3. Dog ate it

• Icing
• Maintenance
• Tower shadow
• Unknown

Monitoring at Site

Data Validation Processing, and Reporting Mean wind speed:

• Mean, or average wind speed, is shown for

each elevation with sensors.

• Ten minute or hourly data is validated, then

averaged monthly.

• Long term data source is used to adjust an

annual mean into a long term mean wind speed.

Monitoring at Site

Data Validation Processing, and Reporting Max 1 second gust

• Will the turbine survive it?
• There are average values for this figure for

different areas in the country.

• Used for foundation designs.
• Many turbines can survive 100 mph or

more.

Monitoring at Site

Data Validation Processing, and Reporting Standard deviation of speed:

• A number that indicates how much wind

speed changes above or below the mean.

• Tedious to calculate.

1. Compute the mean for the data set. 2. Compute the deviation by subtracting the mean from each value. 3. Square each individual deviation. 4. Add up the squared deviations. 5. Divide by one less than the sample size. 6. Take the square root.

Monitoring at Site

Data Validation Processing, and Reporting Standard deviation of speed- examples:

Std dev. =1 Most speeds close to the mean Std dev. =2

• Std. Dev. =3

Large variability

Monitoring at Site

Data Validation Processing, and Reporting Standard deviation of speed:

Formula:

For a set of data- 6m/s 19 times, 7m/s 54X and 8 m/s 42X:

Monitoring at Site

Data Validation Processing, and Reporting Mean wind shear:

• Shear shows amount of change in wind

speed with distance above ground.

• Calculated by S/So=(H/Ho)α

1. H- height above ground 2. S-wind speed 3. Alpha- shear coefficient

• Changes throughout the year.
• Midwest averages are high, 0.19-0.35.

Monitoring at Site

Data Validation Processing, and Reporting Mean wind shear:

• Often computed over several ranges, for

example, from 10-30m and from 30-50m.

• Must extrapolate if that same shear value

will apply to heights above measured, for example from 50-70m.

• Public tall tower data can help validate shear

assumptions- if close enough.

Monitoring at Site

Data Validation Processing, and Reporting

Mean Wind Shear: Notice differences in shear at different times of year.

Monitoring at Site

Data Validation Processing, and Reporting Vertical wind shear exponent: Alpha = log(S/So)/log(H/Ho) So for a site with wind speed of 10 mph at 10 meters, and 12 mph at 30 meters- Alpha = log (12/10)/log(30/10) = .17 That’s a lower number for the Midwest.

Note how you can mix units.

Monitoring at Site

Data Validation Processing, and Reporting Prevailing wind direction:

• Predominant direction the wind blows.
• Important to check direction when setting

up instrument.

• Data given in degrees, often North is 360o.
• Used to create a wind rose that shows

direction of wind and power in the wind.

Monitoring at Site

Data Validation Processing, and Reporting Mean turbulence intensity:

• Relative indicator of turbulence, not an

absolute value.

• TI = standard deviation/mean wind speed

1. Low- <0.10 2. Medium 0.10-0.25 3. Large > 0.25

Monitoring at Site

Data Validation Processing, and Reporting Wind power density:

• Amount of power in the wind.

Wind power density = 0.6125υ3CACT (W/m2) Where υ= wind speed (m/s) CA -Adjust for altitude = 1- Altitude/28682.5 (Altitude is in feet) CT –Adjust for temp = 519.67/(T + 459.67) (T is in degrees Fahrenheit)

Monitoring at Site

Data Validation Processing, and Reporting Wind Rose:

• Very useful graphic to show predominant wind

and wind power directions.

• Done with software such as provided by NRG.

Wind rose from Sturgeon Bay, WI

Monitoring at Site

Data Validation Processing, and Reporting Histograms:

• A graph showing wind

speed frequency distribution.

• Plot the wind speed on

X axis and frequency on the Y axis.

Monitoring at Site

Data Validation Processing, and Reporting Weibull and Rayleigh Plots: Give decent fit for most wind data sets.

Monitoring at Site

Data Validation Processing, and Reporting Rayleigh and Weibull plots:

• Rayleigh is one parameter, easier
• Weibull is two parameter, more accurate

Siting Commercial Turbines

• Use of wind data

sources

• Use of Measured Data
• Topographic

Indicators

• Field Surveys and Site

Ranking

• Potential Turbine

Placement

Siting Commercial Turbines

Use of Wind Data Sources

Wind maps: usefulness and accuracy:

• Overlay with actual tower locations, close to those

locations is somewhat accurate.

• 20 miles or farther from tower data equals guessing.
• Local ridges can improve wind power 10-100% over

that shown on wind maps (new maps try and use topography but are too conservative with some ridgeline wind speed accelerations).

• History of past wind maps provides a lesson.

Siting Commercial Turbines

Use of Wind Data Sources

Very general map, cannot be used for anything more than

• rder of

magnitude analysis.

Siting Commercial Turbines

Use of Wind Data Sources

Notice locations of met towers, there are large areas without tower coverage.

Siting Commercial Turbines

Use of Wind Data Sources

Wind resource models (Windlogics or similar):

• Supposed to yield fairly accurate estimates

(within 2-5%).

• Expense of modeling is high for an estimate and

banks still want to see site data.

• Could be of great use in areas of complex

topography (not Wisconsin).

Siting Commercial Turbines

Use of Wind Data Sources

Measured data:

• The most popular and accepted method is onsite

data from a tip up tower, 40-50 meter.

• Nearby data is also often used, public tower data

from up to 5 miles away has been used for financing commercial scale wind.

• Measured data from towers at a distance of 5-30

miles could also be used if terrain was flat, or nearly so.

• Measured data correlations are only as good as the

reviewing meteorologist- they must correct for topography!

Siting Commercial Turbines

Use of Wind Measured Data

What other data is available:

• There’s public data available on the Internet

for state sponsored sites.

• There is very limited data “for sale”.
• There are a few sites with data collected for

high level weather data (balloons), for pollution migration studies, and for other university related research (the appropriate faculty at local university can help find).

Siting Commercial Turbines

Use of Wind Measured Data

What is quality of other data:

• Public data- Decent, need to consider topography

differences between public site and your site- historically public met data is conservative for production estimates.

• 3rd party data- Wind developer, likely good data.

Perhaps suggest you pay their meteorologist for a turbine production estimate, w/o seeing the data.

• Weather data/research data- You are going to have a

research project of your own to convince a bank its worth considering.

Siting Commercial Turbines

Use of Wind Measured Data

How to perform a production estimate:

• Obtain data from source in ten minute or hourly

format.

• Eliminate “bad” data. This includes icing events, and

negative numbers. Icing events are detected by long periods of zero wind speed in the winter (can reference local climate data for daily record of temp and precipitation).

• If tower has multiple anemometers at a single level,

must go through and select for anemometer with least tower shading (often its simpler to just select highest value between the two).

Siting Commercial Turbines

Use of Wind Measured Data

Tower shading:

Disregard data from downstream anemometer.

Siting Commercial Turbines

Use of Wind Measured Data

How to perform a production estimate:

• Scroll through data and look for obvious bad

data, chop it out.

• Sort wind speed column ascending, and place

in bins of 1 mph intervals (or use fancier software techniques to count).

• Assemble a chart of wind speed bins (by 1

mph intervals) and number of hours in each

• bin. Paste the hourly numbers into Windustry

spreadsheet calculator.

Siting Commercial Turbines

Use of Wind Measured Data

How to perform a production estimate-spreadsheet:

• www.windustry.org/calculator
• Now you must select

appropriate losses for turbine, 10-14% is good range.

Percent Adjustment Factor Reduction

Air Density Enter Elevation at Site, feet 1000.00 Adjustment factor for above elevation 2.97% Enter average temperature, F 49.00 Adjustment factor for above temperatur -1.98% Blade Soiling 4.00% Blade Icing 2.00% Wake Effect 0.00% Secondary Electrical Losses 2.00% Yaw and Miscellaneous Losses 3.00% Availability Losses, Initial 3.00% Total Compounded Initial Losses ......... 14.16% Anticipated Availability Loss Increase/year 0.50% Maximum Anticipated Availability Losses 10.00%

Siting Commercial Turbines

Use of Wind Measured Data

How to perform a production estimate-spreadsheet:

• Properly select anemometer height and wind shear.

Shear values are typically measured and reported for public data sites, make a guess for your site. NOTE: small changes in shear can equal big changes in production! This is where professional meteorologists earns their fee.

• If your public data site has wind speeds at hub height,

shear guess is not needed, just need a correlation guess based on differences in topography.

ET CALCULATES THE POWER PRODUCED BY THE WIND TURBINE AT YOUR SITE USING HOURLY WIN RE LOOKUP TABLES FOR COMMONLY AVAILABLE TURBINES, FOR POWER CURVES

Wind Speed and Power Curve Data -TABLE 2

This table is used to enter both the wind speed distribution data and a specific turbine power curve data. The power curves are to the right in TABLE 4 Turbine# 14 Make and Type of Turbine Selected below: Vestas 660kW 47m rotor 660.00 = Size of Wind Turbine, in kW 175.00 = Rotor Diameter, in Feet 236.00 = Wind turbine tower height, in Feet 95.00 = Reference height of wind speed distribution data below, in Feet 0.20 = Wind shear coefficient at site 1,538,355 = Initial Gross Annual Generation per turbine at reference height 1,845,415 = Initial Gross Annual Generation per turbine adjusted for specified hub height no = Enter "Yes" if wind speed is in Meters Per Second (M/S), rather than Mph 1.00 = Enter the increase in wind speed for each row of the table (e.g., 0.5, 1.0) Calculated Annual Gross kWh Generation Hub Height=Tower Ht. For Number Adjusted to Wind Hours kW Of Hours One Year Speed Units Per Bin Output In Data Set (8760 hrs) 6,673,755 1,538,355 0.0 Mph 279 0.0 1.0 Mph 273 0.0 2.0 Mph 423 0.0 3.0 Mph 543 0.0 4.0 Mph 731 0.0 5.0 Mph 934 0.0 6.0 Mph 930.00 0.0 7.0 Mph 1171.00 0.1 85 20 8.0 Mph 1418.00 0.3 361 83 9.0 Mph 1656.00 3.6 5,977 1,378 10.0 Mph 1788.00 19.7 35,142 8,101 11.0 Mph 2114.00 35.7 75,470 17,396 12.0 Mph 2251.00 56.2 126,404 29,137 13.0 Mph 2331.00 76.6 178,576 41,163 14.0 Mph 2311.00 102.0 235,659 54,321 15.0 Mph 2215.00 128.6 284,768 65,641

Siting Commercial Turbines

Use of Wind Measured Data

How to perform a production estimate- spreadsheet.

Siting Commercial Turbines

Use of Wind Measured Data

How to perform a wind correlation:

• Obtain data from source in same time interval

as that recorded, if possible.

• Use daily mean wind speed for correlation-

daily gives large enough time interval to avoid lag issues due to movement of weather systems.

• Do regression analysis on the two and get an

R2 value- lower is better.

Siting Commercial Turbines

Use of Wind Measured Data

How to perform a wind correlation:

• The longer the data set, the less uncertainty

there is in the mean wind speed.

• +/- 6% uncertainty with one year of data.
• +/- 3% uncertainty with 4-5 years of data.
• Uncertainty decreases as function of square

root of years, so for 2 years of data, decreases by 2 1/2 = 1.4.

Siting Commercial Turbines

Use of Wind Measured Data

How to perform a wind correlation:

Scatter plot of values; site met tower mean daily speed versus airport data daily mean wind speed- use similar elevations AGL . R2 = 0.91

Siting Commercial Turbines

Topographic indicators

Ridges oriented perpendicular to wind:

• THESE ARE THE BEST FEATURES!
• Ridges accelerate wind as it flows over them.
• Ridges oriented parallel or oblique to

predominant wind direction also good.

• Famous Buffalo Ridge of Minnesota rises 700’
• ver surroundings and increases wind speed

from 15.5 mph at 70m to 18mph at 70m (that’s a 65-75% increase in kilowatt-hours!).

Siting Commercial Turbines

Topographic indicators

Highest elevations within a given area:

• A tall hill often provides the same benefit as a

tall tower- but not wind acceleration.

• High elevation is good, and typically means

increased wind power over surroundings in the Midwest.

• Some areas have high elevation, but due to

tree density and weather patterns, still lack decent wind production (near Lake Superior).

Siting Commercial Turbines

Topographic indicators

Locations where local winds funnel:

• Not seen many examples of this in the

Midwest for commercial turbines.

• Long ridges can turn winds that hit them
• bliquely and possibly accelerate them

somewhat by funneling phenomena.

• Windy passes of California are the classic

funneling examples.

Siting Commercial Turbines

Topographic indicators

Available land area:

• Often must compromise on siting given

landowner’s property boundaries- BUT always consider economics of nearby sites.

• Many turbine projects were planned on
• wner’s property and later moved to a spot

with better winds and adjacent interconnect.

Siting Commercial Turbines

Topographic indicators

Positions of existing roads and dwellings:

• Setback turbines from homes a minimum of

750 ft, for noise reasons.

• Farmsteads are often wind breaks and should

be setback from by 2000 ft or more if possible.

• Site turbine as close to town roads as possible,

unless some site deep in the property has much better production.

Siting Commercial Turbines

Topographic indicators

Positions of existing roads and dwellings:

• Farmsteads are major wind obstacle.

Anemometer above grain leg- mounted 85’ AGL, wind speeds reduced to 30’ levels compared to nearby met tower.

Siting Commercial Turbines

Topographic indicators

Land cover:

• Forests rob turbines of power, minimum

setbacks of ½ mile or more if possible.

• Tall towers help alleviate forest effects, but
• verall, open sites have better winds (as

demonstrated by production numbers).

• Fence row trees can create turbulence, but still

not cause major reduction in wind power at 70m.

Siting Commercial Turbines

Topographic indicators

Proximity to power lines:

• KEY COMPONENT OF SUCCESSFUL

PROJECTS!

• Rules of thumb for a 1.5-1.8 MW project*:

1. Within 1.5 miles of substation. 2. Substation has >3MVA transformer. 3. Fault Current at turbine >800-1000A. 4. Interconnect voltages of 12.5 to 41 kV. *All these items can be overcome with more money!

Siting Commercial Turbines

Field Surveys and Site Ranking

Available land area:

• Very important to define all possible turbine

sites first, and slowly eliminate each based on economics and permitting.

• Assign numerical scores to each component:

1. Topo features that increase the wind. 2. Distance from forests. 3. Distance from nearby houses. 4. Distance to interconnect point.

Siting Commercial Turbines

Field Surveys and Site Ranking

Land Use:

• Airport issues are often first to cause

difficulties with large turbines on tall towers (blade tips approach 400’ high).

• Most land uses in agriculture areas are

compatible with wind turbines, from a production standpoint.

• Largest issues are noise at nearby houses,

and the viewshed impacts.

• Property value depreciation worries.

Siting Commercial Turbines

Field Surveys and Site Ranking

Location of Obstructions:

• Keep obstructions on the side of turbine

with least wind energy- consult wind rose

• Possible taller tower to avoid turbulence

from obstructions (costs additional $30- $50K for 80m versus 70m for 1.65MW)

• Obstructions can also block turbine noise

and view- an advantage?

Siting Commercial Turbines

Field Surveys and Site Ranking

Site accessibility:

• Need to keep road to turbine accessible at all

times, watch for road areas that will flood or drift with snow.

• Need to allow for access for large crane to

site throughout turbines life- gear box or blade replacement.

• Privacy or vandalism concerns?

Siting Commercial Turbines

Field Surveys and Site Ranking

Potential impact on local aesthetics:

• Big concern to the neighbors!
• Best to send letters and hold meetings early

to discuss impacts and benefits of the project.

• Noise impacts can be studied and predicted

using manufacturer’s noise curves and distance to adjacent houses.

• FAA blinking lights- get least obtrusive

allowable-low flash frequency.

Siting Commercial Turbines

Field Surveys and Site Ranking

Distance to Noise Ratio NM82

August 2 0 0 3 25 30 35 40 45 50 55 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 1000

D istance fro m T urbine (meters)

3 m/s 4 m/s 5 m/s 6 m/s 7 m/s 8 m/s 95% Rated Power

Potential impact on local aesthetics: noise.

Siting Commercial Turbines

Field Surveys and Site Ranking

Cell phone service reliability for data transfer:

• Met tower dataloggers can send data via cell;

it’s costly and can cause data loss. For single met installations stick with data cards.

• Wind turbines will be connected via a

dedicated land line. Budget for this cost.

Siting Commercial Turbines

Field Surveys and Site Ranking

Possible wind monitoring locations:

• Very important to get good data, best site is

the proposed turbine location.

• Many times turbine location is undefined, so

site met tower in a corner of the field, near the road and in an area representative of the wind regime (same distance from trees,

• bstacles, same location on ridge).
• Keep in mind the that guy wires extend

150 ft.

Siting Commercial Turbines

Potential Turbine Placement

• Get FAA clearance first. It’s free and often if you

are ok at one location, you’ll be ok 500 ft away and vice versa.

• Initial interconnect and electrical cost estimates.
• Start township/county permit process.
• Monitor the wind.
• After all above items pass the test, then start

narrowing search for the turbine location. DONT START WITH RIGID TURBINE LOCATION!

Siting Commercial Turbines

Turbine Placement: Exercise West WI

Siting Commercial Turbines

Turbine Placement: Exercise West WI

Overview:

1. Airports, FAA- nearest airport 6 miles North 2. Permitting- St Croix River is National Riverway, within 1 mile- red flag! Township level in Polk County. 3. Interconnect- 2.7 miles to 3 phase 12.5kV line, 5 miles East to get to a 69kV line, otherwise its all single phase 4. Existing wind data- Focus on Energy wind estimate program indicates 13.8 mph wind at 70m, corresponds pretty well with WI wind map 5. Nearest public met tower, #401, 40 miles Southeast 6. Topography- moderate elevation, no ridge, mixed woods and fields.

Siting Commercial Turbines

Turbine Placement: Exercise SE WI

Siting Commercial Turbines

Turbine Placement: Exercise SE WI

Overview:

1. Airports, FAA- nearest airport 9 miles West, landing strip ¾ mile south- requires clearance as well 2. Permitting- by Township in Rock County 3. Interconnect- 0.5 miles to 3 phase 12.5kV substation at Emerald Grove, 2 miles South to get to a 69kV line 4. Existing wind data- Focus on Energy wind estimate program indicates 13.9 mph wind at 70m, corresponds pretty well with WI wind map- Both are low 5. Nearest public met tower, #407, 75 miles Northeast 6. Topography- moderate elevation, some ridge, mainly open fields but a large woodlot nearby.

Wind Mapping Methods

Wind Mapping Methods

Pros and Cons

Wind maps based on tower met data and topography provide a good general estimate- in areas near those towers! Examples are MN wind map made using WASP.

• IL map made by

AWS Truewind, using airport data and very limited tower data. Very general guide.

• Highlights some

good topo features… Wind Mapping Methods

Pros and Cons

Wind Mapping Methods

Pros and Cons

• AWS Truewind used often due to lower cost.
• Terrain features and land cover play large part

in the determination of wind speeds over large areas.

• Models are very broad and general for most of

the area of coverage, a large grid is used to show an entire state.

• Can be used to see a few of the large ridges

with wind acceleration features.

Wind Mapping Methods

WindLogics Method

• Windlogics type maps and analysis are

expensive but can be very thorough; might take a room of computers a week or a month to complete.

• More importantly the large wind data sets can

be used for wind forecasting and modeling of turbine output for utilities and transmission

• perators.

References

People: AWS Truewind- Mike Markus Vestas- Phil Stiles WindLogics-Grant Brohm NRG Systems- David Blittendorf Texts/reports: Wind Power for Home & Business, Paul Gipe Wind Energy Systems, Dr Gary L. Johnson WI WRAP report- Global Energy Concepts MN WRAP report- MN Department Commerce ND POWER wind data report Various EPRI reports

Contact Information

Windustry

2105 First Ave. S. Minneapolis, MN 55404 Main Phone: 612-870-3461 Wes Slaymaker: 612-870-3464 E-mail: wslaymaker@windustry.org Web: www.windustry.org