DE GUZMAN Wind Printing

DE GUZMAN, Maria Louren, A.2006-34080

EgyE 201 2nd Semester A.Y. 2013-2014

Assignment 1

WIND ENERGYPART 1

A. Specifications

Wind, from which wind energy is derived, is basically air inmotion.1 It is mainly induced by the uneven heating of the earth’scrust by the sun.2 The differences in temperatures caused by thisuneven heating results to high and low pressure systems whichcauses air to move. Air always moves from higher pressure tolower pressure.1In this view, wind is technically an indirect formof solar energy.2 In the case of wind energy, it is the winds’kinetic energy that is converted to electrical or mechanicalenergy to do work.3

Often, wind energy is claimed to be not only pollution free butalso, since wind is naturally occurring, is technically speakingfree in itself. The energy and environmental impacts of itsutilization, however, is not.

Wind energy is often erratic, unsteady, and treacherous, exceptin certain areas.2 Exploration of these areas where wind energycan be harnessed, as well as the key parameters that should beconsidered.

I. Classificationsa. Planetary Winds

Planetary winds are caused by the greater heating by the sunof the earth’s surface near the equator compared to that ofthe northern and southern poles. Warm tropical air rises andflows through the upper atmosphere towards the poles whilecold air from the poles flows down and back to the equator.Direction of motion of winds under this classification withrespect to the earth is affected by the planet’s rotation.Warm air moving towards the poles in the upper atmospheretakes on an easterly direction which results to the“prevailing westerlies” in both the northern and southernhemispheres. Also, the inertia of cold air moving towardsthe equator nearer to the surface of the earth causes it to

1 Meteorologist Jeff Haby. “What Causes the Wind to Blow?”.theweatherprediction.com.Para. 1-22 M.M.El-Wakil. “Chapter 14. Wind Energy”.Powerplant Technology. 3 California Energy Emission. “Chapter 16. Wind Energy.” Energy Story. Para. 1 1

turn west, which results to the “northeast trade winds” andthe “southeast trade winds” in the northern and southernhemisphere respectively.2 The winds mentioned above areshown in Figure 1 below for easier understanding.

Figure 1. Planetary Winds in the Earth's Atmosphere (EPRI)2

b. Local Winds

Winds under this classification are caused by two (2)mechanisms. First is “differential heating” of both land andwater. Solar isolation during the day is readily convertedto the land surface’s sensible energy but partly absorbed inthe layers below the surface of the water and partlyexpended in the water’s evaporation. Land mass becomeshotter than the water, which causes the air above land toincrease in temperature compared to the air above water. Thewarmer air above the land rises and the cooler air above thewater sinks to replace it. Shore breezes are of thismechanism. Assuming clear skies, the direction of breezes isreversed at night because land mass cools to the sky at afaster rate than water.1The differential heating mechanismis illustrated in Figures 2, 3, and 4 below.

Figure 2. Shore Breeze (Sea Breeze)


Figure 3. Shore Breeze (Land Breeze)

The second mechanism is caused by hills and mountain sides.Air above the slopes heats up at day and cools down at nightmore rapidly than the air above the lands of lower altitude.This causes the warmer air to rise up along the slope duringthe day and the cooler air to sink during the night.1

Figure 4.Mountain and Valley Breeze2


B. Samples

Wind energy is often harnessed with the use of turbines.Installation may be done on-shore or off-shore. One example ofon-shore installation is of the wind farm here in the Philippinesknown as Bangui Bay Wind Farm. A picture of the actual site isprovided below in Figure 5.The site is located at Bangui Bay,Ilocos Norte, has 20units of 1.65MW wind turbines, and generates33MW of power.1

Figure 5.Bangui Bay Wind Farm1

An example of off-shoreinstallation is the KårehamnWind Farm in theBorgholmKommun Region inSweden with 16 3MW turbinesinstalled 3.8km from the shore.The plant has a total capacityof 48MW.2 Compared to on-shore wind farms installation of the turbines is more difficultfor off-shore. The design of the turbines’ foundation as well asthe attack on the construction is more complicated as allmaterials and equipment will have to be taken to the site on sea.The construction process is then exposed to demanding weatherconditions and all key components have to be installed in largenumbers in deep water and high altitude.3In this view, off-shoreinstallations tend to be more costly.

Figure 6.Kårehamn Wind Farm2

1 Bangui Wind Farm Official Facebook Account2 4C Offshore. “Karehamn”. http://www.4coffshore.com/windfarms/windfarms.aspx?windfarmid=SE08 . Ret. 24-Nov-13. 4

http://www.4coffshore.com/windfarms/windfarms.aspx?windfarmid=SE08


Other means of harnessing wind energy is discussed later in thispaper in the Extraction and Handling sections.

1 Bangui Wind Farm Official Facebook Account2 4C Offshore. “Karehamn”. http://www.4coffshore.com/windfarms/windfarms.aspx?windfarmid=SE08 . Ret. 24-Nov-13. 5



C. Matrix of Properties

Since the main resource utilized by wind energy is wind and windis basically air in motion, properties of air is presented belowin Table 1. Air properties affect the amount of power than can beharnessed from wind as will be shown in a later section of thispaper.

Table 1. Table of Properties of Air at Standard Temperature and Pressure

ITEM # PROPERTIES VALUES

1 Density 1.293 kg/m3

2 Specific Heat (cP) 1.005 kJ/kg•K3 Thermal Conductivity 0.0243 W/m•K4 Kinematic Viscosity 13.30x10-6 m2/s5 Prandtl’s # 0.715

6 Air GasConstant(Ideal) 0.2869 kJ/kg•K

Note that all property values 1 to 5 above are at the standardtemperature and pressure of 273.15K and 105 Pa.In the generationof energy from wind, items 1 and 6 above are usually used asassumptions in theoretical calculations; equations are providedand discussed later in this paper. In reality, these values aredependent on the temperature and pressure of the air.

D. Critical Parameters

Because wind energy is usually harnessed with the use windturbines, one key parameter then that should be considered in theutilization of wind energy is wind velocity, i.e. speed anddirection. The values of critical wind velocities vary dependingon turbine design. Below defined are the critical parametersattributed to wind energy.1

Velocity. Significant wind velocity values vary at values around 7to 80 miles per hour or 3.13 to 35.76 m/s, depending on windturbine design.2

1 EnergyBible.Org. “Wind Speed and Wind Energy.” Wind Energy. energybible.org. Ret. 23-Nov-2013.2 Windustry.Org. “Chapter 6 : Siting Guidelines”. www.windustry.org. Ret. 24-Nov-2013.3 Dr.GL. Johnson. “Chapter 2 Wind Characteristics”. Wind Energy Systems. Nov. 20, 2001. Ret. 04-Dec-20134 Aerospace Blockset.“Dryden Wind Turbulence Model.” http://www.itu.dk. Ret. 04-Dec-2013 6

Atmospheric Stability refers to the amount of mixing present in theatmosphere. Air mass is attracted to the earth by the force ofgravity and for this not to fall to the earth’s surface, theremust be an equal and opposite force directed away from theearth. This opposing force comes from the decrease in airpressure with increasing height. The greater the density ofair, the more must pressure decrease upward at a higher rateto hold the air at constant height against gravity, which iswhy the pressure decreases quickly with height at lowaltitudes, where density is high, and slowly at high altitudeswhere density is low. The balanced force condition is referredto as “hydrostatic balance” or “hydrostatic equilibrium”.Average atmospheric pressure as a function of elevation abovesea level for middlelatitudes is provided in Figure 7. Thiscurve is part of the model for the U.S. Standard Atmosphere.The pressure is assumed to not vary with localtemperature; it is assumed that the column of airdirectly above the point of interest maintains the samemass throughout any temperature cycle.3

Turbulence is defined as fluctuations in wind speed. Thisaccounts for the intermittency in the power that iseffectively harnessed from the wind.4 In this view, it isimportant that turbulence be modeled such that it can bepredicted. Prediction is usually done with the use ofstatistics, methods of which will not be discussed in thispaper as it is quite complicated. Turbulence can be consideredas a stochastic process defined by velocity spectra. One modelof wind turbulence is the Dryden Wind Turbulence Model. Thismodel gives the probability of exceedance given the RMSTurbulence Altitude in ft/s and the altitude in thousands offeet for

1 EnergyBible.Org. “Wind Speed and Wind Energy.” Wind Energy. energybible.org. Ret. 23-Nov-2013.2 Windustry.Org. “Chapter 6 : Siting Guidelines”. www.windustry.org. Ret. 24-Nov-2013.3 Dr.GL. Johnson. “Chapter 2 Wind Characteristics”. Wind Energy Systems. Nov. 20, 2001. Ret. 04-Dec-20134 Aerospace Blockset.“Dryden Wind Turbulence Model.” http://www.itu.dk. Ret. 04-Dec-2013 7

medium to high altitudes.1 This model is usually used in the USfor aircraft design and simulation applications. Figure 8shows the Dryden Model.

Intermittency is the characteristic of being not continuouslyavailable due to some factor outside direct control. Figure 9shows readings in Puerto Rico throughout the month of Octoberof 2013. The more peaks and variations in readings such asthis illustrate intermittency.

Figure 7.Ave. Atmospheric Pressure vs Elevation Above Sea Levelfor MiddleLatitudes 2

Figure 8.Dryden Wind Turbulence Model1

1 Aerospace Blockset.“Dryden Wind Turbulence Model.” http://www.itu.dk. Ret. 04-Dec-20132 Dr.GL. Johnson. “Chapter 2 Wind Characteristics”. Wind Energy Systems. Nov. 20, 2001. Ret. 04-Dec-20133 “Wind monitor data”. Puerto Rico. http://www.naic.edu/~phil/wind/wind_mon.html. October 2013. Ret. 04-Dec-2013

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Figure 9.Wind Velocity vs. Time3

1 Aerospace Blockset.“Dryden Wind Turbulence Model.” http://www.itu.dk. Ret. 04-Dec-20132 Dr.GL. Johnson. “Chapter 2 Wind Characteristics”. Wind Energy Systems. Nov. 20, 2001. Ret. 04-Dec-20133 “Wind monitor data”. Puerto Rico. http://www.naic.edu/~phil/wind/wind_mon.html. October 2013. Ret. 04-Dec-2013

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Another key parameter that should be considered is location.During siting, other parameters are also considered, such as landuse, aesthetics, human safety and comfort, and environmentalimpacts.1

Harnessing wind energy would require large open spaces tomaintain access to the wind resource. Wind projects are bestsited in areas where the winds are not turbulent. Even if a sitehas high average wind speeds, turbulent wind is not good forcreating lift onwind turbine blades which causes the rotor tospin. Wind turbulence also causes stress on the equipment whichwould decrease its life span.1

E. Estimates1) World

Shown below are the global statistics of win capacitiesinstalled in the world as of the year 2012.

Figure 10.Installed Wind Capacities in the World2

1Project Goodman. “The Wind Energy Industry; A Global Perspective”. www.projectgoodman.com. Ret. 29-Nov-2013.2 Global Wind Energy Council. “Global Statistics”. www.gwec.net. Ret. 24-Nov-2013.

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Figure 11.Global Cumulative Installed Wind Capacity 1996-20122

1Project Goodman. “The Wind Energy Industry; A Global Perspective”. www.projectgoodman.com. Ret. 29-Nov-2013.2 Global Wind Energy Council. “Global Statistics”. www.gwec.net. Ret. 24-Nov-2013.

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Figure 12.Global Annual Installed Wind Capacity 1996-20121

Table 2.Global Installed Wind Power Capacity in 2012 - Regional Distribution1

1 Global Wind Energy Council. “Global Statistics”. www.gwec.net. Ret. 24-Nov-2013.12

1 Global Wind Energy Council. “Global Statistics”. www.gwec.net. Ret. 24-Nov-2013.13

2) Philippines

According to the country’s Department of Energy (DOE), ThePhilippines, being situated on the fringes of the Asia-Pacificmonsoon belt, exhibits a promising potential for wind energy.Data from the Philippine Geophysical Astronomical ServicesAdministration (PAG-ASA) shows that the country has a meanaverage of about 31 watts per square meter (W/m2) of wind powerdensity.2

Currently, as presented in the Samples section of this paper,the country has one (1) operating wind farm in Bangui IlocosNorte with a capacity of 33MW which supports about 40% of thepower demandofIlocos Norte, making the province less relianton the power from La Union.3

In 2006, it was computed that the power generated by the windfarm allowed for over 1 million USD (P45.46 million) insavings. In the future, there are plans to expand the projectfurther and almost double wind farm's capacity. It isprojected that additions to the project in the next 10 yearswould boost the wind farms share on Ilocos Norte’s demand to70%.3

1 Windfinder. ww.windfinder.com. Ret. 24-Nov-201314

F. Exploration

Basically exploration is done with the use of wind maps and actualsite data gathering.

Figure 13.Global Wind Map As of November 24, 20131


Figure 14.Philippines Wind Map As of November 24, 20131


Figure 15.Philippines Wind Energy Potential Sites1

The following sites have been identified by the DOE as havinghigh potential for wind energy utilization.1

Ilocos Mountain Province Cuyo Island Basco Catanduanes Tagaytay City Lubang and Cabra Islands Western portions of Batangas Guimaras Masbate Northeast coast of Negros Occidental Palawan

1Republic of the Philippines Department of Energy. “Wind”. www.doe.gov.ph. Ret. 24-Nov-2013. 17

G. Extraction and Handling

Because wind is naturally occurring, no extraction and handlingis done to produce the resource before utilization. But one wayto forcefully “extract” wind is by inducing it using the sameconcept of heating to creating pressure differences. This isshown in the figure below.

Figure 16.Heating Chamber / Tower

Prior to utilization, siting is done to decide location, takinginto consideration the critical parameters discussed in theprevious section of this paper. The following instruments aretypically used during siting.a. Anemometer – to measure wind speedb. Wind Vane – to get wind directionc. Thermometer –to measure ambient air temperatured. Barometer – to measures air pressure

For off-shore installments, additional information is needed todecide whether a site is suitable. One parameter is the oceandepth. There are two ways to determine ocean depth; one is by theuse of acoustic echo-sounders on ships and another is bysatellite altimetry.1Echo sounders measure the depth of the oceanby transmitting sound pulses and observing the time required toreceive the echo from the bottom. The time is then recorded by aspark burning a mark on a slowly moving roll of paper.2A satellitealtimeter, on the other hand, measures the height of thesatellite above the sea surface. This is subtracted from theheight of the satellite's orbit and the difference is the sealevel relative to the center of the Earth.3

1 R. Stewart. “Chapter 3 – The Physical Setting”. oceanworld.tamu.edu. Ret. 24-Nov-20132 Dietrich, et al. (1980)3 Stewart (1985)1 18

Figure 17.Acoustic Echo Sounder1

1 R. Stewart. “Chapter 3 – The Physical Setting”. oceanworld.tamu.edu. Ret. 24-Nov-20132 Dietrich, et al. (1980)3 Stewart (1985)1 19

Figure 18.Satellite Altimetry1

H. Transportation and Storage

Wind, as a source, is not transported or stored as the windutilized is naturally occurring, which is why siting is veryimportant if wind energy is to be utilized effectively. What isactually transported and stored is the output electricitygenerated by the turbines as a solution to the problem ofintermittency of the wind as an energy source and is not coveredin this paper.

I. Conversion

Figure 19 below shows the conversion of energy.

1 National Oceanic and Atmospheric Administration. “Chapter 3 NOAA Operations”. www.ppi.noaa.gov. Ret. 24-Nov-2013

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Figure 19.Energy Conversion for Wind Energy

1 National Oceanic and Atmospheric Administration. “Chapter 3 NOAA Operations”. www.ppi.noaa.gov. Ret. 24-Nov-2013

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Solar EnergyEarth’s surface’s uneven heating inducing air movementKinetic EnergyWind's KE harnessed by turbines

Since wind energy is harnessed mainly by turbines, Figure 20below shows the different parts inside a turbine which enablesthe conversion of kinetic energy to the desired electrical energyoutput.

Figure 20.Parts of a Wind Turbine

Wind turbines come in many sizes and configurations and are builtfrom a wide range of materials. A wind turbine consists of a rotorthat has wing shaped blades attached to a hub; a nacelle that housesa drive train consisting of a gearbox, connecting shafts, supportbearings, the generator, and other machineries; a tower; and ground-mounted electrical equipment. The wing shaped blades on the rotoractually harvest the energy in the windstream. The rotor convertsthe kinetic energy in the wind to rotational energy transmittedthrough the drive train to the generator. Generated electricity canbe connected directly to the load or feed to the utility grid.1

The basic driving force of air movement is a difference in airpressure between two regions.This air pressure is described byseveral physical laws: Boyle’s law, which states that the product ofpressure and volume of a gas at a constant temperature must be aconstant, and Charles’ law, which states that, for constantpressure, the volume of a gas varies directly with absolutetemperature. The combination of these two laws gives the ideal gaslaw. In equation form, Boyle’s, Charles’, and the Ideal Gas Law aregiven below respectively.

1 Dr.GL. Johnson. “Chapter 2 Wind Characteristics”. Wind Energy Systems. Nov. 20, 2001. Ret. 04-Dec-20132 M.M.El-Wakil. “Chapter 14. Wind Energy”. Powerplant Technology. 22

(Boyle’s Law)1

(Charles’s Law)1

(Ideal Gas Law)1

Now, for the power that can be harnessed from wind, the followingequations are used.2

= mass-flow rate, kg/s or lbm/hρ = incoming wind density, kg/m3 or lbm/ft3

A = cross-sectional area of stream, m2 or ft2

Vi= incoming velocity, m/s or ft/h

J. After Conversion Technologies

No after conversion technologies are applicable for wind energyas it is naturally occurring.

1 Dr.GL. Johnson. “Chapter 2 Wind Characteristics”. Wind Energy Systems. Nov. 20, 2001. Ret. 04-Dec-20132 M.M.El-Wakil. “Chapter 14. Wind Energy”. Powerplant Technology. 23

PART 2

A. Schematic Diagram of Production

Wind, in itself as a source of energy is produced naturally asdiscussed in the Specifications section. Figures 1, 2, 3, and 4show how this is possible. A schematic has also been provided inFigure 19 in the above section.

B. Energy Used in Production

The energy used in the production of wind as a source isquantified by the amount of solar energy absorbed by the earth’ssurface, both land and water.

Figure 21.Earth’s Energy Balance1

From Figure 21 above, 55% of the incoming energy from the sun isabsorbed by the earth’s surface, 30% is directly reflected backto space by clouds, the earth’s surface and different gases andparticles in the atmosphere (earth's albedo, or reflectivity, is0.3 on average), and 20% is absorbed by the atmosphere andclouds.1The table below provides sample values to quantify thisamount of energy.

Table 3. Solar Energy Values as Received by the Earth2

ITEM

#PROPERTIES VALUES

1Extraterrestrial SolarRadiation Intensity(Solar Constant)

1.353 kW/m2

2 Terrestrial Solar RadiationIntensity

depends on air mass(ma)

1 NC State University. “Earth Energy Balance”. Climate Education for K-12.www.nc-climate.ncsu.edu. Ret. 24-Nov-20132 M.M.El-Wakil. “Chapter 14. Wind Energy”. Powerplant Technology. 24

@ ma=1; 0.9249 kW/m2

@ ma=4; 0.2345 kW/m2

Solar Constant given above is the value of the direct radiationfrom the sun, unscattered by atmosphere. Its exact value variesaround 3.5% per year due to earth's rotation. The terrestrialsolar radiation intensity, on the other hand, factors inscattering by the atmosphere. It is composed of beam radiationand diffuse radiation and is dependent on the air mass ratio,which is the ratio of the optical thickness of atmosphere,through which beam radiation passes to the surface, to theoptical thickness at sun’s zenith (directly above). This is givenby the equation:

1 NC State University. “Earth Energy Balance”. Climate Education for K-12.www.nc-climate.ncsu.edu. Ret. 24-Nov-20132 M.M.El-Wakil. “Chapter 14. Wind Energy”. Powerplant Technology. 25

whereθz is the zenith angle.1

From the 50%, around 7% is transferred to the air, which induceswind. What is called as the Earth’s Radiation Budget isillustrated by the figure below.

Figure 22.Earth’s Radiation Budget2

C. Emissions Emitted in Production

Emissions are only calculated for the energy used in theconstruction and operation of turbines since the natural processof producing wind does not have this.

D. Strategies for Energy Resource Improvement and Sustainability

I. Improvements to Conversion

No improvements can be offered to the production of wind.

II. Emissions ReductionBecause there are no emissions associated with the productionof wind, there is, therefore, nothing to reduce.

REFERENCES

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1 M.M.El-Wakil. “Chapter 14. Wind Energy”. Powerplant Technology.2 National Aeronautics and Space Administration (NASA). “Earth's Radiation Budget Facts” http://science-edu.larc.nasa.gov/EDDOCS/radiation_facts.html. Ret. 04-Dec-2013 26

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University of Oldenburg in Germany.<http://phys.org/news/2013-04-turbines-great-turbulence-consequences-grid.html>

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