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AE 4701 Assignment #5: Final Report for the Wind Turbine

Proposal in Croix-des-Bouquets, Haiti

By Sahithya Chodimella Aerospace Engineering, Georgia Institute of Technology

Summer 2014

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Table of Contents Introduction __________________________________________________________________ 3

Proposal Recap and New Revisions _______________________________________________ 3

Croix-des-Bouquets, Haiti ____________________________________________________ 3

Local/National Energy Resources and Amount of Consumption _______________________ 4

Exploring Various Wind Tunnel Modeling Tools and Implementation __________________ 4

Turbine Design Parameters and Blade-Element/Momentum Theory ____________________ 4

Power Output Analysis _______________________________________________________ 5

NREL Cost Model Analysis ___________________________________________________ 5

Environmental/Community Concerns & Potential Solutions ____________________________ 6

Avian _____________________________________________________________________ 6

Noise _____________________________________________________________________ 7

Power Quality ______________________________________________________________ 7

Conclusion __________________________________________________________________ 7

Appendix ____________________________________________________________________ 8

Figure 1 Wind Resources Map of Haiti at 80 m _______________________________________________________ 8

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Introduction This report will briefly re-iterate on each previous sub-topic related to the wind turbine proposal

for Croix-des-Bouquets, Haiti. This includes, but not limited to, the following:

Describing Croix-des-Haiti’s capability as a “windy” site and its lifestyle/history, that

have interested VESTA engineers to propose wind turbine technology

Sharing research on the site’s annual energy consumption and what energy resources are

sought out by the local population

Introducing wind tunneling tools used in turbine design to determine performance (power

and power efficiency distribution with wind speed and tip speed ratio)

Describing the blade design and how Blade Element Momentum (BEM) theory was

applied

Sharing power output results from WT_PERF modeling tool and analyzing it

Discussing a cost analysis of the model provided by NREL

Supporting figures have been placed in the Appendix.

Note: After a revision with other experts, certain changes have been implemented to improve the

cost and power output, but compromising efficiency slightly. RPM of the turbine could be

lowered, but is unnecessary for our current needs.

Lastly, the following sub-topic will be addressed: Issues and concerns regarding the

environment, including avian protection, noise reduction, and power quality control. While wind

turbines are very helpful, they can also create a nuisance if proper provision is not considered.

Hence it will be the main focus of this report and the conclusion to this proposal before

submitting it to a professional review panel.

Proposal Recap and New Revisions

Croix-des-Bouquets, Haiti Croix-des-Bouquets is a suburban city 12.9 km northeast of the capital of Haiti, Port-Au-Prince.

It is home to over 200,000 people, but this number has increased greatly since the 2010

earthquake, as it willingly took in millions of refugees1. Post the catastrophe, a field hospital was

set up, along with camps, to accommodate victims for treatment and urge physicians worldwide

to volunteer their skills for the cause. The rehabilitation process still continues today and has

become a more and more expensive ordeal in other aspects, such as operating and maintaining

equipment continuously to be able to make proper diagnoses. While all staff of the medical

center work free of charge, the number of medical equipment amasses to a large electricity bill

which cannot be avoided in the current circumstances. Hence, it is just as strenuous on the field

hospital as it is for the general population.

The Ouest Department major city is notably located on the Plaine du Cul-de-Sac1, which is

fertile lowland that extends from southeastern Haiti to southwestern Dominican Republic. Here,

several organic crops are grown, primarily beans, corn, and sweet potato. This type of terrain is

1 http://en.wikipedia.org/wiki/Croix-des-Bouquets

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excellent for a wind turbine to power a large suburb as Croix-des-Bouquets. As shown in Figure

1, the area surrounding the city possesses a velocity range of 7.0 to 7.5 m/s2. This is a class IV at

80 m elevation and, for the energy needs of this area, is a sufficient wind speed range.

Local/National Energy Resources and Amount of Consumption Croix-des-Bouquets is known as a modern, culture hub, yet still assimilates the traditional ways

of energy consumption, and so does the rest of Haiti. It mainly retrieves its electricity from fossil

fuels, i.e. petroleum, natural gas, and coal, and some hydroelectric plants. In Figure 2, a 2011

statistic provided by the CIA World Factbook shows fossil fuels to be almost a three-quarters of

the resources consumed by the nation3. Additionally, the current cost of energy is $0.35/kWh,

which sums up to $770,000/year. Hence, much of Haiti’s economic debt and deteriorating

environment would be reduced if it invested renewable energy technology, and definitely in wind

turbines.

Exploring Various Wind Tunnel Modeling Tools and Implementation To begin understanding what is required of the wind turbine design to be able to obtain the

desired results, one must familiarize his- or herself with the latest wind tunnel modeling tools.

There are currently over 10 active design codes used for structural dynamic, aerodynamic, and

power output analysis of wind turbines. Of them, the main candidates used for rotor performance

are WT_Perf, FAST, and PROPID. According to Wind Energy Explained: Theory, Design, and

Application by James F. Manwell, “WT_Perf calculates rotor blade performance using blade-

element/momentum theory….was developed by NREL, but originally written in the 1970s by

Oregon State University. It operates as a steady-state model, and computes power, torque, thrust,

etc.” From the same text, FAST and PROPID are also described. PROPID is a tool not too

different then WT_Perf, except for the fact that its focus was chiefly on “the aerodynamics,

structure, cost, and noise.” Lastly, FAST incorporates Aerodyn in its code to perform an

aerodynamic and dynamic analysis of the forces acting on blades. This then accounts for 14

degrees of freedom and has therefore proved to be marginally more advanced than WT_Perf.

However for the purpose of this project, WT_Perf is sufficient, as the target was to obtain power

curves.

Turbine Design Parameters and Blade-Element/Momentum Theory The design of the turbine depends on several physical features, including blade radius, number of

blades, blade shape, hub height, airfoil family, terrain roughness factor, local wind speed, etc. To

determine these parameters, basic equations and relationships from blade-element/momentum

(BEM) theory were used (refer to Appendix for more information). The first step was to

determine blade radius, based on the given rated power of 1 MW. It was found to be

approximately 50 m. Next, the minimum hub height was determined using the 1.8*R ratio, which

gave us 90 m. If this hub height was not satisfactory, it could be increased using the power law to

obtain a higher wind velocity. 3 blades were set for this turbine. Then an airfoil family was

chosen to section the 15-segment blade. Initially, S818-827-828 was selected as it was a set

already designed for extra-large blades. However, due to lack of available information on the

aerodynamic data of 827/828, incorrect, low values for Cp were being retrieved by WT_Perf.

2 http://www.nrel.gov/wind/international_wind_resources.html#haiti

3 https://www.cia.gov/library/publications/the-world-factbook/geos/ha.html

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This was vindicated by simply setting all sections to S818, which had an acceptable L/D value

and eventually allowed the performance output higher, appropriate Cp values.

Figures 3 and 4 show the twist and chord distributions of the blade. Since only one airfoil shape

was used, a smooth twist distribution was easy to obtain, which then makes it reliable for

manufacturing purposes. The chord distribution was also found, non-dimensionalized, and

linearized for similar reasons.

Power Output Analysis In Figures 5 and 6, two important power curves are shown: Power output vs. wind speed and Cp

(power coefficient) vs. tip speed ratio. The highest power generated at the maximum chosen

pitch angle was approximately 2.8 MW at 16 m/s at 5 degrees; this would be 67 MW-hours per

day. 1,800 solar panels on University Hospital in Port-Au-Prince produce nearly twice this

amount, which is said to offset nearly 72 tons of coal4. This relative to the former is greater,

which is understandable as a field hospital or medical center runs on less equipment.

Nonetheless, it is still sufficient and can be a replacement for 35 tons of coal. The maximum Cp

obtained at a pitch of 5 degrees is 0.47 at a tip speed ratio of 7.5; this is normal for large wind

turbine designs. In both graphs, we notice that they both peak before decreasing. This is because

WT_Perf operates based off of BEM theory, which assumes that the spanwise flow along the

blade is neglected, but in reality aerodynamic properties like lift, drag and pressure are

augmented (especially at the root). Hence the optimization code doesn’t account for stall-delay

of stall-regulated rotors and the appropriate model must be chosen by the user to increase the

accuracy of BEM predictions.

In addition to the performance predictions of WT_Perf, the Weibull method estimation was also

used to determine how much energy could be capture by the wind turbine design. The annual

production computed to be approximately 25.6 GWh/year, which is slightly higher than what

WT_Perf outputted (~24.5 GWh/year). Both use the BEM procedure, however according to

Figure 7, the Weibull distribution predictions show much lower power output for a given wind

speed range than WT_Perf. This is probably because it doesn’t account for any pitch effects.

NREL Cost Model Analysis The cost of the wind turbine depends on several services and professions. From manufacturing to

engineering to legal issues, every detail of the project is contributed by various sectors of

expertise. In Table 1 a breakdown of the cost model is shown, divided into sub-categories for

components of the turbine, the initial capital cost, balance of station costs, land taxes, operation

and maintenance, etc. Here, the most expensive investment would be the initial capital cost. But

with the amount of energy captured annually, the rate of cost has significantly reduced, to about

8 cents/kWh. This would certainly help uplift the Haitian economy and prevent further debt,

especially for earthquake victims who are struggling to recover financial stability and need

employment to do so.

4 http://www.goodnewsnetwork.org/new-hospital-in-haiti-powered-by-1800-solar-panels/

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Environmental/Community Concerns & Potential Solutions While wind turbines are certainly favorable for sites in need of an economic boost and are

possibly wind-abundant, it is important to ensure that the installment of one near the city neither

disturbs the population nor harm any wildlife. In this section, issues concerning the environment,

society and other power-related issues will be addressed. Hopefully these approaches will be

seen as sufficient and effective enough to convince the people of Croix-des-Bouquets and

potential investors to accept this proposal.

Avian The primary question that is often brought up when introducing wind turbines is how the

company plans to protect or repel local birds from them. Large turbines that are placed in open

areas and reach high altitudes are especially a threat to fowls that migrate along such paths, as

they can collide with the moving blades. Also, the long, extended size of the blades can appear to

be branch-like and mislead animals to perch on them. The annual number of bird deaths per year

due to wind turbines could be a hindrance to the acceptance of this project. However, there are

some options this company could offer to resolve these issues. This includes a visual disguise, an

alarm/sounding system, radar/EMF propagation, impact detection, limited operation, etc.

Visual disguise is a simple yet effective way to warn animals in flight of the obstacle ahead. This

can work like how road signs help drivers at night time, by using bright and bold colors to

contrast with sky. This could be done by just spray painting the blades post-manufacture, with

distinct colors that are eye-catching yet still aesthetic.

An alternative would be use sound to alert or scare birds away from the premise. An alarm would

sound off once a bird has approached the area of the turbine, from a certain distance away. The

system would utilize a form of motion detection via cameras placed on the hub of the turbine.

This could be an effective method, but perhaps also a noisy nuisance if too frequent.

Next, radar/EMF signals could be propagated to irritate and annoy birds to move away from the

sound. Usually because these signals are set such high frequencies, they are above the normal

human hearing level and hence won’t be a disturbance to the population. This option would

certainly reduce the number of bird collisions without compromising the aesthetic appearance or

peaceful environment. Its only fallback is that it would be more expensive than the two former

options.

An impact detection system is recent idea that came out of a collaborative research effort by

Oregon State University and Meslands Community College in New Mexico. The concept is to

slow the turbine speed once it feels a strike hit its blade. Because it is still undergoing testing, the

readiness level of this method would be medium and probably implemented within the coming

year.

Aside from these technological approaches, other options would include carefully selecting a

location near the site that does not interfere with migratory paths, creating a sanctuary to attract

birds, or limiting peak operation times. Placing the wind turbine in site that is open land with

fewer trees nearby would be ideal, but this is not always the case everywhere obviously. But

certainly a spot which is not near homes of large endangered species is always better. Also,

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limiting the operation times would also help, but could be bad for business. This would have the

wind turbine shut down or slow down when wind speeds are not at peak.

In Haiti, there are several wild and unique species of birds, including the Vervain Hummingbird,

the Stolid Flycatcher, and the Golden Swallow. While these are not necessarily large birds, they

are endangered already and travel frequently everywhere in Haiti, including cities. There are

currently 10 protection sanctuaries in Haiti for these animals, issued by the government. Hence,

placing a turbine in Croix-des-Bouquets would require that it be located far from any of the

sanctuaries and implements one of the technologies above, preferably the radar/EMF signal

activation. Bold coloring of the blades would also work, and aesthetics is anyways the least of

population’s issues in its current state.

Noise Wind turbines are thought to be quite loud and resounding; however, decibel estimation is

primarily objective and largely depends on how far the wind turbine is from homes in the site.

Recently, a straightforward, neat was released by GE to explain how loud a turbine can “appear”

be at certain distances. As it can be seen, a wind turbine placed about 300 meters away would

sound like somewhere between an air conditioner and refrigerator (30-40 decibels). The blades

themselves are moving at “snail’s pace” and only create a soft “whooshing” sound.

In Croix-des-Bouquets, because it is a small suburb, the number of homes affected is fewer but

nonetheless an issue to be dealt with. There is also a great amount of open space surrounding the

city where the wind turbine will have enough distance from main population.

Power Quality Because this turbine will be mainly serving the medical center, there is no major issue

concerning the power grid. The benefits to the local population would be only economic in terms

of employment and efficient health care. Also, the electricity supplied to the center would be

“net-metered”, meaning it would solely be charged for how much it uses per day, in spite of

being connected to the common power grid.

Conclusion Having a wind turbine installed in Croix-des-Bouquets to support a relief-mission medical center

can be beneficial if it is not only well-designed, but also is wisely placed further from bird

protection sites and uses animal retraction methods, is placed strategically near a site but with

enough distance to help reduce noise, and ensures low-interference with the community’s power

grid. This design is large in size and rated power, and hence comes to be useful for high power

consumption facilities like a medical center. After completion of the analysis based on the blade

design, tower height, and the site’s wind speed capacity, the peak amount of produced power

nearly surpassed the expected 2000 kW mark and has reduced the cost by approximately 27

cents. In addition to power and cost, one must also do a reality check in terms of societal and

environmental implications that could arise. Practically, having a wind turbine in Haiti is a risk

to a lot of the nature and wildlife, as there are over a thousand species that are unique to the

country and are constantly migrating internationally and domestically. Hence, already existing

sanctuaries can be utilized to help determine an ideal location for the wind turbine without

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placing it too far from the site of interest. Location also affects the intensity of noise felt by the

community. In this case, noise is a very small concern for the people in Haiti, but this can still be

addressed for Croix-des-Bouquets, as it is a suburb. As long as the turbine is 300 meters or

further from the site, it will not project itself in an obnoxious manner. The power grid is a minor

concern for this particular concept, as it will only affect the medical center in terms of its request

for net-metering. This way, despite the turbine operating on a common power grid, the power

company will only be charging for the electricity that is supplied to and consumed by the

medical center.

Appendix

Figure 1 Wind Resources Map of Haiti at 80 m

Figure 2 Percentage of Energy Resources used in Haiti (2011)

71%

29%

Fossil Fuels

Hydroelectric Plants

Croix-des-Bouquets

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Figure 3 Chord distribution

Twist distribution

0.0000

0.0100

0.0200

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0.0500

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0.0700

0.0800

0.0900

0 0.2 0.4 0.6 0.8 1 1.2

c/R

r/R

Chord Distribution

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-4.0000

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4.0000

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β (degrees)

r/R

Twist distribution

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r O

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(kW

)

Wind Speed (m/s)

φ = 0 deg

φ = 1 deg

φ = 2 deg

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φ = 4 deg

φ = 5 deg

0

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φ = 0 deg

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Rating (kWs) 1000 1000 Baseline Projected Component Major

Component Component Percent Cost Element

Component Costs $1000 Costs $1000

Improvement

% Improvement

Rotor 395 395 0.0%

Blades 243 243 0.0%

Hub 53 53 0.0%

Pitch mchnsm & bearings 99 99 0.0%

Drive train,nacelle 424 424 0.0%

Low speed shaft 6 6 0.0%

Bearings 42 42 0.0%

Gearbox 74 74 0.0%

Mech brake, HS cpling etc 2 2 0.0%

Generator 55 55 0.0%

Variable spd electronics 79 79 0.0%

Yaw drive & bearing 57 57 0.0%

0 5 10 15 20 25 30 35 40

Windspeed (m/s)

Wind, Energy

Rayleigh Probability Weibull Probability Weibull Betz

Turbine Energy Weibull Cp

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Main frame 41 41 0.0%

Electrical connections 40 40 0.0%

Hydraulic system 12 12 0.0%

Nacelle cover 15 15 0.0%

Control, safety system 10 10 0.0%

Tower 419 419 0.0%

TURBINE CAPITAL COST (TCC) 1,249 1,249 0.0% 0.0%

Foundations 70 70 0.0%

Transportation 33 33 0.0%

Roads, civil works 57 57 0.0%

Assembly & installation 86 86 0.0%

Elect interfc/connect 91 91 0.0%

Permits, engineering 21 21 0.0%

BALANCE OF STATION COST (BOS) 358 358 0.0% 0.0%

Project Uncertainty 162 162 0.0%

Initial capital cost (ICC) 1,769 1,769 0.0%

Installed Cost per kW for 1.5 MW turbine 1,769 1,769 0.0%

(cost in $)

Turbine Capital per kW sans BOS 1,374 1,374 0.0%

(cost in $)

LEVELIZED REPLACEMENT COSTS

(LRC) ($10.7 kW) 11 11 0.0% 0.0%

O&M $20/kW/Yr (O&M) 2 2 0.0% 0.0%

Land ($/year/turbine) 3 3 0.0%

Net 7.5 m/s ANNUAL ENERGY PRODUCTION Energy MWh (AEP) 2562.48 2562.48 0.0% 0.0%

Fixed Charge Rate 11.85%

COE at 7.5 m/s $/kWh 0.0875 0.0875 0.0%