urban wind turbine senior design project final...

Title Page

URBAN WIND TURBINE SENIOR DESIGN PROJECT FINAL REPORT

By:

Michael Austin

Cody Bateman

Torrey Roberts

Mirai Takayama

Prepared For

ME 480 Senior Design

Boise State University Mechanical Engineering Department

May 5, 2005

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Executive Summary

The goal of this senior design project was to determine the optimal location for an urban wind turbine system on top of one of the Boise State University (BSU) College of Engineering Buildings (COEN). We selected a turbine system from potential vendors that would perform efficiently at the location. We have determined that the center of the Micron Engineering Center (MEC) building at a height of 20-30 ft above the rooftop is the optimal location for a wind turbine. The Bergey XL1 is a 1kW turbine that could be purchased and installed at this location. This turbine has an 8.2 foot diameter and would produce approximately 370 kW-hr/year at this location. Our decisions were based upon months of wind flow analysis, wind data analysis, and turbine performance analysis which is explained in the pursuing sections. From an economic stand point, a turbine installation on the MEC building would be a very poor choice. A break-even point would never be reached for the 20 to 30 year life span because of the low average wind speeds. However, the wind turbine could be used for research and observation by BSU faculty and students.

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Table of Contents Title Page ............................................................................................................................. i Executive Summary............................................................................................................ ii Table of Contents............................................................................................................... iii Introduction......................................................................................................................... 1 Objectives ........................................................................................................................... 1 Background ......................................................................................................................... 2 Design Solution................................................................................................................... 4

Location ...................................................................................................................... 4 Turbine System Selection ......................................................................................... 11

Analysis............................................................................................................................. 12 Location .................................................................................................................... 12 Fluent Background.................................................................................................... 12 FloWorks Background .............................................................................................. 13 CFD Analysis............................................................................................................ 13 March Case Study ..................................................................................................... 19 Turbine System ......................................................................................................... 23 Safety Analysis ......................................................................................................... 26

Discussion ......................................................................................................................... 27 Conclusions....................................................................................................................... 27 Recommendations............................................................................................................. 28 References......................................................................................................................... 29 Appendix........................................................................................................................... 30

Turbine Power Curves .............................................................................................. 30 Turbine Cost Tables .................................................................................................. 32 FloWorks Wind Maps............................................................................................... 36 Fluent Wind Maps..................................................................................................... 38 Monthly Boise Airport Wind Rose ........................................................................... 40

1

Introduction

Demand for power in urban areas is constantly increasing. Innovative ideas for generating power are needed. Wind turbines placed on top of existing or new structures present a possible solution. Past experience gained in installation of small wind turbines is now being used to create systems with better performance, lower costs, and higher reliability. Due to increased energy demand, urban wind turbines systems are under examination.

The purpose of this senior design project was to determine the optimal location for a wind turbine on top of one of the College of Engineering (COEN) buildings and to select an appropriate turbine system that will operate efficiently and safely in an urban environment. The turbine would be used primarily for educational and observational purposes if installed. According to wind data from the Boise Airport, the average wind speeds from 1997 to 2003 were 7.6mph. Since, most wind turbines require minimum wind speeds of 8-10 mph to begin operating, turbines at this location will not generate significant amounts of power. However, average wind speeds for Boise in March are 8.8 mph.

Installing a wind turbine on one of the COEN buildings is not a good economical choice; however it will enable the university to perform research regarding urban wind turbines. Information gathered from this research can be applied to other more economical turbine locations.

The turbine needs to be installed in the optimal location to harvest the maximum amount of wind power available. In addition the turbine needs to fulfill the following user needs:

• Operate in low wind speeds.

• Monitored easily by faculty and students.

• Accessed easily by faculty and students.

• Include power storage and delivery system.

• Safe to operate in an urban environment.

Objectives

Initially our objective was to install an operational wind turbine to power the Segway and COEN Electric Vehicle by the end of May 2005. Shortly after investigating the project scope, we concluded the task was far too vast for a single semester project and we needed to narrow our focus.

The new scope consisted of determining the best wind turbine location at the COEN based on wind speed and selection a suitable wind turbine system by May 2005. A budget for this project was not provided by BSU. Therefore our only cost objective was to keep capital costs low.

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Background

Several factors have influenced a renewed and increased interest in wind energy. People want alternative forms of energy to reduce their dependency on fossil fuels. Additionally, wind turbines have continued to become more efficient, while at the same time becoming more cost effective. In Idaho, power is provided at one of the lowest rates in the country. However, with increasing pressure to sustain migratory fish restrictions and recent low water flows, power rates are sure to rise. This is driving consumers and the power industry to look for alternative form of energy.

Ranked 13th out of 50 states for wind energy potential, Idaho has 7,370 km2 of class 3 or greater wind area (Figure 1). Over 8,000 mega watts of wind energy potential is available; unfortunately most of the high wind regions are not located near current transmission lines. The state provides a personal tax deduction of 40% of the cost of installing a solar, wind, or geothermal electric or heating system for the year of installation, and 20% for each year thereafter. Net metering is available for wind turbine systems less than 100kW. The Energy Division of the Idaho Department of Water Resources (IDWR) provides five year loans at 4% interest for wind and other renewable energy projects1.

Figure 1 – Idaho Wind Classification Map

http://rredc.nrel.gov/wind/pubs/atlas/maps/chap3/3-03m/html

According to the Department of Energy (DOE), small privately owned wind turbines require wind speeds greater than 10 mph and the utility supplied electricity cost greater than 10 cents per kilowatt hour for economic viability2. According to Idaho Power’s website, the current small commercial rates are about 7.6 cents per kW-hr.

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Other universities are also investigating the possibility of wind energy. The University of Massachusetts has installed an alternative energy system on the top of their engineering building; consisting of 3 different types of wind turbines and a set of solar panels. They connected the system to a 24V battery bank and to the grid with a 4kW trace inverter. The types of wind turbines installed included: a Bergey 1500W at 80’ (above ground), a World Power Technologies Mariner H500 at 45’, and a Southwest Windpower Air Marine 300 at 45’. Overall, the turbines produced 20% less power than expected, due to the underestimated turbulence of the environment. They installed the entire system for $52,000 in 1998; adjusted for inflation this would approximate $64,000 today. The most expensive part of the project was the engineering required to safely install the equipment on the roof of a public building3.

The power that can be generated from wind is linearly dependant on the swept area of the turbine blades, but a function of the velocity cubed4.

3))()()((5.0 VACpP ρ=

This means wind speeds of 12.6 mph have twice the energy of wind speeds at 10 mph (only 2.6 mph less). Therefore, small differences in wind speed can have a significant impact on the power generated by a wind turbine. Based on conservation of energy, the Betz limit states that the turbine blades cannot extract more than 59% of the total energy available in the wind. In other words, assuming the rest of the system operates at 100% efficiency, the maximum efficiency achievable is 59%. Most wind turbine systems operate within the range of 10% to 30% combined efficiency. Also, most wind turbines do not start to generate power until the wind reaches at least 7 to 8 mph.

Urban wind turbine installations present certain concerns not found in rural wind farms. Traditionally noise produced by turbine blades has been bothersome to those living near wind turbines. Wind turbines typically produce some broadband noise as their revolving rotor blades encounter turbulence in passing air. This type of noise is described as a “whooshing” sound. However, most modern wind turbines are typically not any louder than passing traffic. Figure 2 shows wind turbine noise compared with noise from other activities. The noise level of smaller wind turbines can sometimes be higher because of the higher rotational speed. In addition, less money and research has been invested in reducing noise on smaller turbines than larger turbines5.

Figure 2 – Typical Noise Levels

www.gov.on.ca/.../ engineer/facts/03-047.htm

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Safety is another concern when considering the installation of a wind turbine in an urban area. This is especially true when people are present near the base of the building. Turbulent locations also increase the chance of failure due to the increased load variation imposed on the system. Any failures resulting in falling objects would have catastrophic results and a negative impact on public confidence of urban wind energy systems. When placing an urban wind turbine, it is important to install and design for failure prevention and provide failsafe features to prevent injury.

The turbine owner must follow a strict maintenance program. Tips of wind turbine rotor blades can reach speeds up to 300 mph4. Hail, dirt, and insects contacting the blades at theses speeds can cause premature wear to the blade edges causing extreme physical forces. Thrust and vibration loads also subject the bearings and tower to loads. The lifespan of these bearings depends on the wind conditions and level of maintenance. Turbine manufactures will usually specify activates and intervals required for maintenance. The entire wind system, including the tower, storage devices, and wiring should be inspected on a regular basis. If maintained properly a wind turbine system can last up to 20 to 30 years.

Several different types of wind turbines have been proposed that can be categorized as being either vertical axis or horizontal axis. Vertical axis turbine designs eliminate the need to align the turbine with wind direction and reduce issues related to turbulence. Unfortunately the companies previously producing these turbines have all gone out of business. Vertical axis turbines were eliminated early on in our analysis, and several different brands of horizontal turbine manufactures were evaluated.

Design Solution

Location

We determined the center of the MEC building as the optimal location for a wind turbine at the COEN. This location had the highest wind speeds according to our models and had adequate mounting characteristics. The location is also safer than placing a turbine near the edge of the building. It allows some protection for pedestrians below if a blade fails and allows safe access for a person observing or maintaining the turbine, not near any building edges.

We created detailed and simplified solid model for analysis using SolidWorks, a computer aided drafting program (Figure 3). This model was used to determine wind flow patterns over the COEN Buildings in two separate Computational Fluid Dynamics (CFD) programs. Precise dimensions for the COEN buildings were obtained from the building architectural drawings and field measurements. The dimensions for overall locations and sizes of surrounding buildings were approximated from the Ada County Assessor’s aerial maps.

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Figure 3 - COEN & Surrounding Area

We applied Fluent and FloWorks, two CFD Modeling packages, to map the bipolar wind patterns over the BSU COEN buildings (major wind flow patterns vary from the Northwest and Southeast directions). Both programs indicated that the best location for the wind turbine was in the center of the Micron Engineering Center’s penthouse roof; where the maximum wind speed occurs at approximately 20 to 30 feet above the roof. Wind speed data generated from Fluent and FloWorks for both major wind patterns are indicated in Figure 4 through Figure 7.

8.0 MPH SE WIND ANALYSIS WITH FLUENT

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105

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165

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Location, (in)

Ve

loc

ity

Ma

gn

itu

de

, (i

n/s

)

82 ft (0ft above MEC Roof)











Maximum Wind Speed =170 in/s

at 10ft and 15 ft above MEC Rooftop

3500 inches from origin.

Figure 4 - SE Fluent Wind Analysis

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8.0 MPH SE WIND ANALYSIS WITH FLOWORKS

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Location (in)

Ve

locit

y (

in/s

)

82 ft (0ft above MEC Roof)4@Line1_187 ft (5 ft above MEC Roof)4@Line1_192 ft (10 ft above MEC Roof)4@Line1_197 ft (15 ft above MEC Roof)4@Line1_1102 ft (20 ft above MEC Roof)4@Line1_1107 ft (25 ft above MEC Roof)4@Line1_1112 ft (30 ft above MEC Roof)4@Line1_1117 ft (35 ft above MEC Roof)4@Line1_1122 ft (40 ft above MEC Roof)4@Line1_1127 ft (45 ft above MEC Roof)4@Line1_1132 ft (50 ft above MEC Roof)4@Line1_1

Maximum Wind Speed =167 in/s at 15ft and 20 ft above MEC Rooftop3500 inches from origin.

Figure 5 - SE FloWorks Analysis

8.0 MPH NW WIND ANALYSIS WITH FLUENT

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Location, (in)

Velo

cit

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ag

nit

ud

e, (i

n/s

)

82ft (0ft above MEC Roof)87ft (5ft above MEC Roof)92ft (10ft above MEC Roof)97ft (15ft above MEC Roof)102ft (20ft above MEC Roof)107ft (25ft above MEC Roof)112ft (30ft above MEC Roof)117ft (35ft above MEC Roof)122ft (40ft above MEC Roof)127ft (50ft above MEC Roof)132ft (0ft above MEC Roof)


at 15ft above MEC rooftop


Figure 6 – NW Fluent Wind Analysis

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8.0 MPH NW WIND ANALYSIS FROM FLOWORKS

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Curve Length (in)

Velo

cit

y (

in/s

)



at 25ft above MEC rooftop approximately


Figure 7 - NW FloWorks Wind Analysis

For each of these graphs, 0 inches represents the origin of the solid model generated with SolidWorks. The origin is located at the NW corner of the Engineering Technology (ET) building (reference Figure 8). The lines in the graph represent flow trajectories in a vertical plane 2100 inches (175 ft) southwest from the origin parallel to the Northwest-Southeast directions. This is indicated in the top view of the model used in Figure 8 below. The solid red line represents the plane used in creating graphs above. The grid is in squares of 500 x 500 inches with coordinates at the corners of the map.

Figure 8 – NW Wind Flow Plane Top View

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There are some slight differences between both CFD Models. The Southeast wind graph generated using Fluent indicates a maximum wind speed of approximately 170 in/s (9.7 mph) 10 to 15 feet above the MEC penthouse rooftop 3400 inches from the origin. FloWorks indicates a maximum wind speed of 167 in/s (9.49 mph) 15 feet above the MEC penthouse rooftop at 3300 inches from the origin. Comparisons between the two models are shown in Table 1 through Table 4. The values in these tables represent the best wind power elevations.

Table 1 – FloWorks vs. Fluent Velocity Profile Comparison 3300” From Origin SE Wind

Elevation

Above

Rooftop

FloWorks

Velocity

(in/s)

Fluent

Velocity

(in/s)

%

Difference

10ft 163 160 -1.88%

15ft 167 166 -0.60%

20ft 166 166 0.00%

25ft 165 167 1.20%

30ft 161 166 3.01%

35ft 158 164 3.66%

Table 2 – FloWorks vs. Fluent Velocity Profile Comparison 3400” from Origin SE Wind

Elevation

Above

Rooftop

FloWorks

Velocity

(in/s)

Fluent

Velocity

(in/s)

%

Difference

10ft 165 170 2.94%

15ft 167 169 1.18%

20ft 165 168 1.79%

25ft 163 166 1.81%

30ft 160 165 3.03%

35ft 157 163 3.68%

Table 3 – FloWorks vs. Fluent Velocity Profile Comparison 2700” from Origin NW Wind

Elevation

Above

Rooftop

FloWorks

Velocity

(in/s)

Fluent

Velocity

(in/s)

%

Difference

10ft 147 161 8.46%

15ft 153 166 7.58%

20ft 160 165 3.27%

25ft 161 164 1.78%

30ft 159 163 2.08%

35ft 158 162 2.38%

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Table 4 – FloWorks vs. Fluent Velocity Profile Comparison 3000”from Origin NW Wind

Elevation

Above

Rooftop

FloWorks

Velocity

(in/s)

Fluent

Velocity

(in/s)

%

Difference

10ft 138 141 2.57%

15ft 149 152 2.38%

20ft 158 159 0.79%

25ft 162 161 -0.13%

30ft 161 162 0.87%

35ft 160 163 1.42%

Wind isoline maps were generated using FloWorks and are shown in Figure 9 and Figure 10. The closely spaced orange isolines indicate that the location with the best wind speed is the center of the MEC building at this elevation.

Figure 9 – FloWorks Wind Isolines 20 feet Above Top of MEC Building SE Wind

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Figure 10 – FloWorks Wind Isolines 20 feet Above Top of MEC Building NW Wind

Isolines were also generated using Fluent, and are as shown below. For Fluent, the velocity isolines are in m/s. Fluent and FloWorks gave similar solutions; the middle of the MEC is the best place to locate the turbine.

Figure 11 – Fluent Wind Isolines 20 feet Above Top of MEC Building SE Wind

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Figure 12 – Fluent Wind Isolines 20 feet Above MEC Building NW Wind

Turbine System Selection

According to our analysis, the Bergey XL1 1kW turbine system ranked 3rd in power output and was the least expensive. We recommend this system for the MEC building because of its low initial capital cost. The turbine has a rotor diameter of 8.2 feet. Bergey also provides a matching tower, generator, and power conversion system. Table 5 summarizes the parts and prices for the expandable system.

Table 5 – Bergey Turbine System Price List

`

Power Output : 1 kW Company : Bergey

Type : Battery Charging Model : BWC XL 1-24

Product PriceTurbine

Turbine and PowerCenter multi-function controller 2,450$

Tower

Tower (30 ft tilt-up) 950$

Tower wiring kit, 7 Circuit 600$

Batteries

5.3kWh Battery Bank 450$

Inverter

1,500 W Inverter System 1,044$

Installation 10,000$

Total : 15,494$

Annual Profit & Loss

Energy Generation 29$

O&M (75)$

Payback Period NA

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Several types of turbines were analyzed to determine how they would perform in this area. We utilized the decision matrix in Table 6 to help select the best turbine.

Table 6 – Turbine Decision Matrix

Criteria

Importance

Weight (%) Rating

Weighted

Rating Rating

Weighted

Rating Rating

Weighted

Rating Rating

Weighted

Rating Rating

Weighted

Rating Rating

Weighted

Rating Rating

Weighted

Rating

Number of School Days Operating 32 3 0.96 4 1.28 2 0.64 2 0.64 4 1.28 4 1.28 4 1.28

Cost 20 4 0.8 4 0.8 1 0.2 2 0.4 4 0.8 3 0.6 3 0.6

Safety 15 2 0.3 4 0.6 4 0.6 4 0.6 3 0.45 3 0.45 3 0.45

kW-hrs per Year 12 0 0 2 0.24 4 0.48 0 0 0 0 3 0.36 3 0.36

Reliability & Maintenance 10 2 0.2 4 0.4 4 0.4 4 0.4 2 0.2 2 0.2 2 0.2

Aesthetics & Noise 7 3 0.21 3 0.21 3 0.21 3 0.21 3 0.21 3 0.21 3 0.21

Availability 4 3 0.12 4 0.16 4 0.16 4 0.16 2 0.08 2 0.08 2 0.08

Total 100 NA 2.59 NA 3.69 NA 2.69 NA 2.41 NA 3.02 NA 3.18 NA 3.18

Rating Value

Unsatisfactory 0

Just Tolerable 1

Adequate 2

Good 3

Very Good 4

SW Windpower Air X

400 WBergey 1 kW Bergey 7.5 kW

Concept Alternatives

Bergey 10 kW Proven Energy 600 WProven Energy 2.5 kW

Battery

Proven Energy 2.5 kW

Grid

Analysis

Location

Fluent and FloWorks were the two CFD modeling packages used to model the wind patterns over the BSU COEN Buildings. Using both modeling packages allowed us to verify our results. To ensure accuracy of the results, we used architectural drawings and Ada County Assessor maps to define elevations and locations of the COEN and surroundings to accurately define the solid model. After the solid model was defined, we imported it into both CFD packages for analysis.

Fluent Background

Fluent is the industry CFD software leader. It is a very robust and accurate software package. Fluent uses GAMBIT as its modeling and meshing program that enables the user to model complex geometry where the fluid flow analysis takes place. In our case we imported the model defined in SolidWorks as an IGES file into GAMBIT. The model was then broken up into an unstructured grid, called a mesh that consists of user defined shape elements. Smaller element shapes and sizes provide more accurate result. However, decreasing an elements size greatly increases the computation time. So, the solid model was simplified to allow a timely analysis of the wind flow patterns. The simplification of the solid model is shown in Figure 13 and Figure 14.

Figure 14 – Initial Model COEN &

Surrounding Buildings Figure 13 – Simplified Model COEN &

Surrounding Buildings

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This simplified model was analyzed in both FloWorks and Fluent to check precision between the two modeling packages. The result precision is tabulated in the “% Difference” column in Table 1 thru Table 4. The more complex initial model was used in SolidWorks for a March wind study when the average wind speeds increase to around 8.8 mph.

FloWorks Background

Fluent’s user interface requires extensive knowledge and experience to produce accurate results. For this reason, user friendly CFD packages like FloWorks are available to the average user. FloWorks is the CFD modeling package fully embedded within the SolidWorks Computer Aided Drafting Program. Its user interface is designed for the average design engineer who may not have the expertise required to operate Fluent. One of the drawbacks to its user friendliness involves lack of functionality. For example FloWorks does not have the ability to model two phase flows nor will it allow you to change the mesh elements shape like Fluent. However, you can control mesh element gap size represents, so more accurate results may be obtained.

CFD Analysis

The initial analysis of the wind flow patterns over the COEN Buildings involved both Fluent and FloWorks. Analyzing the same model with the same inputs allowed us to verify the accuracy of the results with respect to each CFD system. In this case, we imported the simplified model shown in Figure 13 into both Fluent and FloWorks. The input velocity for this analysis was 8.0 mph which is close to the spring time wind speed average. We did multiple studies in which we altered the wind direction between Northwest and Southeast. The parameters associated with the modeling can be found below in Table 7.

Table 7 – CFD Modeling Parameters

Modeling Parameters Fluent Floworks (Using Floworks Wizard)

Time step size Every 0.2 seconds Steady State

Time Frame Analyzed 0 - 40 seconds Steady State

Unsteady Formulation 2nd

order implicit NA

Velocity Formulation Absolute NA

Energy Equation OFF Adiabatic (OFF)

Viscous Model K-epsilon Default

Boundary condition of the

building surface

No slip shear

condition

.06 in Surface Roughness

Fluid Type Air Air

Physical Features Turbulent Turbulent

Analysis Type NA External (excluded internal spaces and excluded

cavities without flow conditions)

Velocity Parameters 8.0 mph (SE and

NW directions)

8.0 mph (SE and NW directions)

Pressure 101.3kPa (Default) 101.3 kPa (Default)

Temperature 291K (Default) 291K (Default)

Result Resolution NA 3

Gap Size 3”-600” (at each

edge of

Tetrahedral)

Default at 1088” (edges of parallelogram) Mesh

Elements are approximately twice the size of

Fluent

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The difference in mesh sizes can be seen in the Figure 15 and Figure 16. Where Figure 15 represents the tetrahedral meshes made by Fluent and Figure 16 represents the rectangular prism meshes generated by FloWorks. Figure 17 and Figure 18 represent the NW velocity contour maps of the plane passing directly through the center of the MEC building. The location of the plane is 2100 inches from the origin and the plane is parallel to the SE direction.

Figure 15 – Fluent Mesh

Figure 16 – FloWorks Mesh

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Figure 17 – NW Wind FloWorks Contour Map at 2100” from Origin

Figure 18 – NW Wind Fluent Contour Map at 2100” from Origin

The FloWorks output velocity is in inches/second whereas the Fluent output velocity is in m/s. Both of the color scale maximums are equal (i.e. 177 in/s = 4.5 m/s) so there is a direct correlation between the two color schemes. If both contour maps show the same color in the same area the wind speeds experienced in that area are similar. This is evident in the region directly above the center of the roof of the MEC building. Both contour maps show a trend of increased velocity over the top edge at about the same elevation. This is evident in Table 1 through Table 4.

Alternatively, if the contour maps do not show the same color in the same area the conclusion could be made that the wind speeds are different for that area between the models. This phenomenon is evident in the tail section of the flow indicated in dark blue by the FloWorks model. There is a slight difference in the wind tail colors where the recirculation occurs. This is more than likely due to the different mesh sizes. The FloWorks mesh is approximately twice the size of the Fluent mesh. The mesh size difference was an oversight in the initial stages of the modeling project. However, the maximum wind speed results due not seem to differ by more than 3.2% in the attractive wind turbine placement elevations between 10-35 ft above the roof. This is apparent in the highlighted regions of the following tables.

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Further analysis shows that there is a slight vertical component to the wind vectors in these areas. The following figures show that this vertical component is nearly the same between both modeling packages.

Figure 19 – SE Wind Vector Gradient Map

Figure 20 – SW Wind Vector Gradient Map

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When looking at the graphs of the y-velocity vector vs. location, the magnitude of the y-velocity is negligible at the center of the MEC building (2800 to 3300 in).

8.0 mph NW Analysis with Floworks

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Y-v

elo

cit

y (

in/s

)

82 ft (0ft above MEC Roof)4@Line1_1

87 ft (5 ft above MEC Roof)4@Line1_1










Figure 21 – NW Vertical Velocity Analysis

8.0 mph NW Analysis with Fluent

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Figure 22 – NW Vertical Velocity Analysis

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8.0 mph SE Analysis with Floworks

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Figure 23 – SE Vertical Velocity Analysis

8.0 mph SE Analysis with Fluent

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Figure 24 – SE Vertical Velocity Analysis

The following table analyzes the vertical vector magnitude at the center of the MEC building 3000 inches from the origin. The location can be seen in Figure 8.

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Table 8 – Vertical Vector Magnitudes NW at 3000” from Origin

Elevation

Above

MEC

Rooftop

FloWorks

(in/s)

Fluent

(in/s)

Difference

(in/s)

5ft 5.73 0.15 5.59

10ft 8.39 1.94 6.45

15ft 10.78 5.89 4.89

20ft 13.32 8.00 5.32

25ft 10.31 9.07 1.24

30ft 11.97 8.17 3.80

35ft 9.44 7.86 1.58

40ft 13.51 10.87 2.63

45ft 13.94 8.47 5.48

50ft 13.66 11.12 2.54

Table 9 – Vertical Vector Magnitudes SE at 3000” from Origin

Elevation

Above

MEC

Rooftop

FloWorks

(in/s)

Fluent

(in/s)

Difference

(in/s)

5ft -4.64 -5.12 0.48

10ft -3.20 -3.75 0.55

15ft -2.11 -2.33 0.22

20ft 1.40 -0.74 2.14

25ft 2.94 0.80 2.14

30ft 2.59 0.01 2.57

35ft 4.21 0.53 3.68

40ft 5.51 3.77 1.73

45ft 6.48 2.52 3.96

50ft 7.46 5.55 1.91

The data in the above tables shows that the maximum difference in vertical velocity magnitude in the NW direction is 5.59 in/s (.32 mph) and 3.96 in/s (.23 mph) in the SE direction. This is a small variation in the velocity in the y-direction so we can be assured that wind velocities experienced by turbine blades between the elevations of 20-35 ft will be mostly normal to the blades ensuring the optimum performance of the turbine.

March Case Study

We used the initial model shown in Figure 14 to run a March case study of wind speeds from the Northwest and Southeast at an average of 8.8 mph. Due to the complexity of the solid model, we chose to analyze the wind flow using FloWorks only. Time was not available to run the analysis with Fluent.

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The FloWorks results indicated that the best location for the wind turbine is the center of the MEC building between 20ft and 30 ft above the penthouse rooftop. Figure 25 and Figure 26 shows vector gradient maps of these results. The vertical components of the velocity vectors are still approximately 10% of the vector magnitudes. So the results were very similar to that of the studies done with the simplified model discussed in the previous section. However, due to the increase in the initial wind speed the vertical components are slightly larger.

Figure 25 – SE Wind Vector Gradient Map March Case Study

Figure 26 – NW Wind Vector Gradient Map March Case Study

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Evident from the above figures, the maximum wind speeds for the model are 180 in/sec. The figures above show the turbine blade axis 25 ft above the rooftop. The surrounding red color indicates this is a very suitable location for the turbine.

Boise airport wind data from 1997 to 2003 was utilized to get a general idea of the wind characteristics in this area. This data indicated that, for an entire year, we could expect an average wind speed of 7.6 mph. Average wind speed for each month ranges from 6.7 mph low in January to an 8.8 mph high in March as shown in Figure 27.

5

6

7

8

9

10

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

Month

Month

ly A

vera

ge W

ind S

peed (m

ph)

Figure 27-Monthly Avg. Wind Data Boise Airport 1997-2003

The Boise airport wind data also indicated that the wind direction in our area is generally bi-polar; the wind typically blows from either the NW or the SE. A wind rose for the month of March is illustrated in Figure 28.

Figure 28-Wind Rose Data March Boise Airport

22

Data from the wind anemometer and the Boise airport was compared in an attempt to determine the wind correlation factor. Figure 29 shows a correlation equation between wind speeds at the airport to wind speeds at the MEC roof top. According to our correlation, the MEC roof tops will have higher wind speeds than the Boise Airport for wind speeds greater than 6mph. Wind speeds below 6mph are in the non-operational range for our turbine.

y = 1.8601x - 6.0624

R2 = 0.8029

0

5

10

15

20

25

30

35

4 6 8 10 12 14 16 18 20

Airport Wind Speed (mph)

ME

C R

oo

f-T

op

Win

d S

peed

(m

ph

)

Figure 29 – MEC and Boise Airport Wind Speed Correlation

However, the wind direction between the MEC and Boise airport is similar about 23% of the time within a 22.5 degree range. The variation is greater from 12:00pm to 7:00pm than other times of the day. Wind speeds measured at the same time for the Boise airport and the MEC are shown in Figure 30.

0

5

10

15

20

25

30

35

12:50AM

2:50AM

3:50AM

4:40AM

5:50AM

6:50AM

8:50AM

9:50AM

10:50AM

11:50AM

12:50PM

2:50PM

3:50PM

4:50PM

5:50PM

6:50PM

7:50PM

8:50PM

9:50PM

10:50PM

11:50PM

Time

Win

d S

pe

ed

, (m

ph

)

Airport Wind speed MEC roof top Wind speed (mph)

Figure 30 - Boise Airport/COEN Wind Speed Correlation Avg. 4/18/05 to 4/25/05

23

The entire COEN complex was measured in order to generate models of the buildings. This was done with a combination of field measurements and Architectural drawings. Wind measurements were taken with a hand held anemometer during the month of March to get a general feel for the wind characteristics on top of the building. Other wind measurements were collected from the airport and the tower mounted anemometer on the MEC east side. Table 10 shows some of the wind measurements recorded in March with a hand held anemometer at about 14.5 feet.

Table 10 - MEC Wind Measurements 3/8/05 (left) & 3/10/05 (right)

NW corner (10 feet from west side edge and 10 feet from north side edge) SW corner (10 feet from west side edge and 10 feet from south side edge)

Max, (mph) Min, (mph) Average, (mph) Time Direction, (degree) Max, (mph) Min, (mph) Average, (mph) Time Direction, (degree)13.7 5.5 9.3 4:18 315 15.9 0.0 11.7 3:48 32012.4 6.0 7.1 4:24 315 23.1 0.0 14.2 3:50 300

7.2 1.4 1.9 4:26 315 18.7 4.5 11.7 3:52 29013.5 0.0 6.4 4:29 295 18.8 4.5 12.3 3:54 29010.3 4.5 5.7 4:33 280 16.7 2.2 7.0 3:56 2859.1 4.6 5.1 4:35 310 18.2 0.0 15.1 3:58 300

10.3 5.2 7.0 4:37 300 18.0 9.7 11.3 3:59 29014.6 5.1 11.2 4:39 300 24.9 4.7 20.4 4:01 27015.0 7.2 11.7 4:41 310 24.9 4.7 14.8 4:03 270

15.9 8.4 10.9 4:43 310

Average of this period 4:18pm - 4:43pm 7.6 305 Average of this period 3:48pm - 4:03pm 13.2 291

North End (21feet from west side edge and 10 feet from north side edge) South End (23feet from west side edge and 10 feet from south side edge)

Max, (mph) Min, (mph) Average, (mph) Time Direction, (degree) Max, (mph) Min, (mph) Average, (mph) Time Direction, (degree)

15.9 4.9 11.1 4:46 310 15.4 4.0 9.2 4:10 28011.8 5.4 9.3 4:48 285 17.9 7.4 11.4 4:12 28017.1 4.1 5.6 4:50 280 21.2 8.5 11.6 4:13 290

14.2 0.0 8.0 4:52 295 20.1 7.6 11.4 4:15 28511.4 6.7 7.4 4:54 295 21.3 11.3 14.4 4:17 28013.6 8.2 12.9 4:55 290 16.6 8.2 14.0 4:18 28514.2 6.4 8.4 4:57 310 20.6 7.1 15.2 4:20 280

16.9 9.3 11.2 5:00 300 13.3 1.1 12.1 4:22 27016.2 5.3 15.1 5:02 310 17.0 4.0 6.4 4:24 27012.8 7.4 9.5 5:03 320 15.0 2.4 9.3 4:26 270


NE corner (35 feet from west side edge and 10 feet from north side edge) SE corner (38 feet from west side edge and 10 feet from south side edge)

Max, (mph) Min, (mph) Average, (mph) Time Direction, (degree) Max, (mph) Min, (mph) Average, (mph) Time Direction, (degree)

13.0 6.8 9.6 5:09 290 15.0 6.9 8.4 4:29 29012.3 4.3 4.9 5:11 290 16.7 3.7 13.5 4:31 2906.5 0.0 4.7 5:13 290 8.5 7.0 8.0 4:33 280

10.3 5.0 6.3 5:16 300 19.2 4.9 14.1 4:35 27512.2 2.6 7.7 5:18 290 17.5 8.0 10.9 4:36 27014.1 8.0 9.3 5:19 300 17.8 5.2 11.9 4:39 27014.1 4.5 10.8 5:22 310 19.0 1.4 16.1 4:40 280

12.6 6.5 9.9 5:24 300 17.1 8.4 14.7 4:43 28014.3 6.9 10.4 5:25 300 21.6 5.7 11.3 4:45 28513.9 5.0 8.5 5:26 300 18.2 1.5 14.5 4:47 280


Turbine System

When analyzed at the MEC location, none of the turbines will produce enough energy to overcome annual overhead and maintenance costs. The greatest producing turbine will generate a mere $68 of energy per year, at an installation cost of approximately $50,000. A wind turbine installation on the BSU campus, and at nearly any location in the Boise metro area, does not meet economic justification. However, setting aside return on investment or other like investment comparators, we can use the initial cost estimates to aid in selecting a turbine. Educational purposes are the primary reason for this turbine installation, therefore we continued with our selection greatly based on the number of operating days per year, and the least costly method to achieve a working unit.

24

Manufactures data was used to create a performance curve for each horizontal axis turbine analyzed. With Microsoft Excel’s© curve fit function we were able to generate a polynomial function of power vs. wind speed for each turbine. The R-squared values for the curve fit were greater than 0.99 for all of the turbines. The average wind speed from each day for the past 7 years was then plugged into the polynomial functions to determine how the turbine would perform in this area. The graph in Figure 31 shows performance for several different brands of turbines through one year based on average wind speeds from 1997 to 2003.

0

1

2

3

4

5

6

J F M A M J J A S O N D J

Kilo

watt

Ho

urs

Per

Day

Bergey Excel R 7.5kW Bergey XL1 1kW Proven Energy WT2500 2.5kW

Proven Energy WT600 0.6kW Bergey Excel 10kW Southwest WP Air X 0.9kW

Figure 31 – Predicted Turbine Power Output 15 Day Moving Average

The 7.5 kW turbine manufactured by Bergey would produce the most power. At around $50,000 to install, the Bergey Excel 7.5 kW has a rotor diameter of 22 feet. Installing a turbine this expensive may not be a feasible solution. Table 11 summarizes the turbine types and cost. The 2nd and 3rd best power producers included a 2.5 kW turbine manufactured by Proven Energy and a 1 kW turbine manufactured by Bergey, respectively. Both of these turbines were much more cost effective and would operate for many more school days per year than the larger turbine. An example power curve that we used in the analysis is illustrated in Figure 32 for the Bergey XL1.

25

0

200

400

600

800

1000

1200

1400

0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0

Wind Speed (mph)

Po

we

r (W

)

Figure 32 – Bergey XL1 Theoretical Power Curve

To facilitate observation by facility and students, the turbine should operate on school days, even if the power produced is minimal. Table 11 summarizes turbine size, yearly estimated power produced, and number of school days the turbines operates. If the average wind speed for the day exceeded the minimum start up speed for the turbine, the turbine was considered to operate on that day.

Table 11 – Turbine Performance Summary

Turbine Type Rating Blade Diameter (m)

Power Produced

Yearly (kW*hr)

Number School Days

in Operation

Total

System

Cost

Bergey Excel-R 7.5kW 6.7 882 122 $50,590

Proven WT2500 2.5kW 3.5 580 247 $22,141Bergey XL1 1kW 2.5 373 247 $15,594

Proven WT600 0.6kW 2.55 124 247 $17,172

Bergey Excel 10kW 6.7 106 122 $37,000Southwest WP Air X 0.6kW 1.14 27 187 $12,191

Power produced by the turbine and generator must be conditioned into an acceptable format. The system could delivery power to a battery bank, to the municipal grid, or directly to the load (appliances, lighting, etc.).

Lower voltage (12 to 48 V), direct current power is a good choice for battery charging and some low load residential requirements. Battery charging is more expensive, due to the high cost of the special batteries required. However, if the goals are to net meter and connect the power with the grid, a certified signal conditioner will be required. Net metering will require working with Idaho Power to complete the install.

26

Most turbine applications significantly benefit from towers, where the turbine is positioned into faster wind speed above the ground surface. Our turbine will be located on the roof top of the MEC building, already 80 ft above street level; a tower is mostly needed to overcome any turbulence effects of the roof structure. The MEC building’s height already helps position the turbine above the transition region of ground and surface objects.

Existing towers and wiring packages from turbine manufactures can be purchased in sizes ranging from 20 to 100 ft. Our wind modeling analysis determined that using a tower 20 ft high on the MEC building would place the turbine above any ill effects of the building’s own turbulence. Any tower taller than 20 ft would not significantly improve wind harvesting capability over the cost incurred in the tower.

Monitoring systems purchased from the turbine manufacturer are designed with the specific turbine performance and output in mind. We were able to locate the different types and costs for monitoring systems available; however, a more detailed user requirement study is needed to finalize a monitoring decision.

Safety Analysis

We considered the failure modes of turbines and possible design accommodations to identify and reduce the risk of injury from the wind turbine. A competent individual must inspect the turbine system on a regular basis to check for fatigue wear. In addition, most turbines will require yearly maintenance and upkeep to reduce the possibility of failure and extend the lifespan. Placing the turbine near the center of the building would increase the probability of a failed blade landing on the building structure and not striking a pedestrian.

A structural and vibration analysis of the building at the install location should be performed. Local building codes will need to be meet in the installation and the turbine will probably have to be inspected by building code officials after installation. A permit may be required to erect the turbine.

10

12

14

16

18

20

22

24

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51

Week 1 thru 52

Win

d S

peed

, (m

ph

)

Figure 33 - Maximum Avg. 2 min. Wind Gust 1997-2003

27

Figure 33 shows the maximum average 2 minute wind gust from 1997 to 2003. The highest wind speed for a 2 minute gust is around 21 mph. However, instantaneous gust were up to twice as high at the Boise airport (a few measurements on the MEC roof exceeded 100 mph, however these velocity measurements occurred during steady wind speeds of approximately 6mph so they were negated for this study). The turbine selected must have safety features to stop operation when the force from the wind speed will exceed design stresses. Most turbines stop operation via a brake or unfurling mechanism at about 40 mph.

Discussion

This project only encompassed a portion of the work that would need to be performed to complete a turbine installation on top of the MEC building. Safety and structural mounting conditions will have to be addressed as mentioned in the previous section. A joint effort between the mechanical and electrical engineering departments at BSU is imperative to the completion of a functioning wind turbine.

Foot traffic, even in small amounts, on top of the MEC building will degrade the life of the roof and cause premature wear and failure. Precautions should be taken to minimize damage to the membrane roof, as it is not designed to handle foot traffic. Incorporating required structural features and safety features will encompass the majority of the installation cost. This design work could be used for another senior design project that builds on this one.

Due to the poor economics of the project and the safety issues, we speculate that the turbine system will probably never reach installation. Installing urban wind turbines on existing building presents several problems, and the benefit achieved at this location simply is not very significant.

Conclusions

We have concluded that the best location for a wind turbine at the COEN is at the center of the MEC building 20-30 feet above the penthouse roof. This structure is approximately 80 feet high and appears to have the best wind characteristics of the three COEN buildings. The highest magnitude of wind velocity was also at the center of this building. Installing the turbine in the center enables easy access and the ability to tie off the turbine tower at more locations. The Bergey XL1 1 kW turbine appears to be the best turbine package that could be purchased and installed on the MEC roof. This turbine was the 3rd best performer and was by far the most cost effective.

28

Recommendations

To complete the installation several important items will have to be performed, some of which are included below:

• Structural analysis of roof structure where turbine is to be installed.

• Contact the roofing contractor who performed the installation for the MEC roof to certify the warranty will not be in-validated and to have additional mounts installed as needed.

• Safety needs to be further considered before installation.

• Building permits may have to be obtained.

• A vibration analysis of the structure and turbine should be performed to ensure that the turbine is not going to produce any undesirable vibrations that could create failure of the turbine or the structure.

• Involving the electrical engineering department in the power connection would be beneficial.

• Install a maintenance path to the turbine to avoid premature wear of the membrane roof.

• If the wind tunnel in the HML high bay become operational in the near future. It could be used to perform scaled testing and verify the results of our models. This was part of our original plan; however the wind tunnel was not operation through out the semester.

29

References

1 Idaho Department of Water Resources. 15 February 2005. http://www.idwr.state.id.us/energy/Energy/ altenergy.htm

2 Small Wind Energy Systems for the Homeowner. U.S. Department of Energy. GO-10098-374. FS 135. January 1997.

3 Case Study of a Residential-Scale Hybrid Renewable Energy Power System in an Urban Setting. Z.M. Salameh and A.J. Davis. University of Massachusetts. 2003

4 Wind Energy Manual. 1 February 2005. http://www.energy.iastate.edu/renewable/wind/wem/wem-01_print.html

5 Facts About Wind Energy and Noise. American Wind Energy Association. Washington, D.C. 2001

6 Engineering Design. Eggert, R. J., Prentice Hall, Inc., 2004, Englewood Cliffs, New Jersey

7 Specifications for Small Wind Turbines for Autonomous Energy Systems. C.G. Condaxakis. et.al. Wind Energy and Power Plant Synthesis Lab. Crete, Greece

30

Appendix

Turbine Power Curves

Bergey Excel-R 7.5kW

y = 0.0029x6 - 0.0976x

5 + 0.2003x

4 + 13.382x

3 - 41.402x

2 + 15.171x + 2.5

R2 = 0.9988

0

1000

2000

3000

4000

5000

6000

7000

0 2 4 6 8 10 12 14 16 18 20

Wind Speed (m/s)

Po

wer

(W)

Bergey XL1 1kW

y = -0.1275x3 + 7.0907x

2 - 60.187x + 136.88

R2 = 0.9953

0

200

400

600

800

1000

1200

1400

0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0

Wind Speed (mph)

Po

wer

(W)

31

Proven WT2500-2.5kW

y = -2.77x3 + 74.138x

2 - 321.27x + 392.01

R2 = 0.9998

0

500

1000

1500

2000

2500

3000

3500

0 5 10 15 20 25

Wind Speed (m/s)

Po

wer

(W)

Southwest WP Air X

y = -0.5848x3 + 17.073x

2 - 95.006x + 149.44

R2 = 0.9986

0

100

200

300

400

500

600

700

0 5 10 15 20 25 30

Wind Speed (m/s)

Po

wer

(W)

32

Bergey BWC Excel-10kW

y = -5.3868x3 + 196.9x

2 - 1304.4x + 2419.8

R2 = 0.9976

0

2000

4000

6000

8000

10000

12000

14000

0 5 10 15 20 25 30 35

Wind Speed (m/s)

Po

wer

(W)

Turbine Cost Tables

`


Type : Battery Charging Model : BWC XL 1-24


Turbine and PowerCenter multi-function controller 2,450$

TowerTower (30 ft tilt-up) 950$

Tower wiring kit, 7 Circuit 600$ Batteries

5.3kWh Battery Bank 450$ Inverter

1,500 W Inverter System 1,044$


Total : 15,494$


Energy Generation 29$ O&M (75)$

Payback Period NA

33

Power Output : 7.5 kW Company : Bergey

Type : Battery Charging Model : BWC Excel-R/120


Turbine and PowerCenter multi-function controller 19,900$ Tower

Tower (64 ft tilt-up) 1,250$

Tower wiring kit 1,000$ Batteries

84 kWh Battery Bank (5 string at $1,944 each) 9,720$ Inverter

11 kW Inverter System 8,030$ Power Center

DC Power Center Option, 7 circuit 690$


Total : 50,590$



O&M (75)$

Payback Period NA


Type : Grid Connect Model : BWC Excel-S/60


Turbine and PowerCenter multi-function controller w/ GridTek 10 Inverter 24,750$ Tower

Tower (64 ft tilt-up) 1,250$

Tower wiring kit 1,000$ Batteries

NA -$ Inverter

NA -$ Power Center

NA -$


Total : 37,000$



O&M (100)$

Payback Period NA

34

Power Output : 600 W Company : Proven Energy

Type : Battery Charging Model : WT600/048


600 Watt 48V wind turbine/generator 3,610$

Tower100 ft. guyed-lattice tower kit 2,163$

-$ Batteries

5.3kWh Battery Bank (from Bergey) 410$ Inverter

NA -$

Power Centercharge controller with HV control. Included MCB Isolator (No Meters). 665$

48V Analogue Volt and Ammeters for use with ECM600 Controllers 323$


Total : 17,172$



O&M (75)$

Payback Period NA

Power Output : 2.5 kW Company : Proven Energy

Type : Battery Charging Model : WT2500/048


2.5 kWatt wind turbine/generator 7,152$ Tower

Tilt-up self supporting wind turbine mast (6.5m). 2,163$

Batteries

10kWh Battery Bank (from Bergey) 820$ Inverter

NA -$ Power Center

2.5kW, 24 or 38V DC battery charging controller. Includes 2 DC and 2,005$ 3 AC divert load connections, V&I meters plus 8 system status indicators.

Suitable for use with a DC system or DC/AC using an inverter.


Total : 22,141$



O&M (75)$

Payback Period NA

35

Power Output : 2.5 kW Company : Proven Energy

Type : Grid Connect Model : WT2500/300


600 Watt wind turbine/generator 7,152$

TowerTilt-up self supporting wind turbine mast (6.5m). 2,163$

Batteries

NA -$ Inverter

NA -$

Power CenterIsolation and rectification controller for use with grid connect inverter. 1,018$

Included V&I meters for perfomance monitoring.


Total : 20,333$



O&M (100)$

Payback Period NA

Power Output : 400 W Company : Southwest Windpower

Type : Battery Charging Model : Air X 24V


900 Watt wind turbine/generator 538$ Tower

45 ft. tower kit 199$

Batteries

5.3kWh Battery Bank (from Bergey) 410$ Inverter

1,500 W Inverter System (from Bergey) 1,044$ Power Center

NA -$


Total : 12,191$



O&M (75)$

Payback Period NA

36

FloWorks Wind Maps

FloWorks Wind Map 1 – NW Wind Velocity Path Lines Colored by Magnitude

FloWorks Wind Map 2 – South Face MEC Building NW Wind Velocity Path Lines

37

FloWorks Wind Map 3 – SE Wind Velocity Path Lines Colored by Magnitude

FloWorks Wind Map 4 - South Face MEC Building SE Wind Velocity Path Lines

38

Fluent Wind Maps

Fluent Wind Maps 1 – NW Wind Velocity Path Lines Colored by Magnitude

Fluent Wind Maps 2 – SE Wind Velocity Path Lines Colored by Magnitude

39

Fluent Wind Maps 3 – South Face MEC Building SE Wind Velocity Path Lines

Fluent Wind Maps 4 – South Face MEC Building NW Wind Velocity Path Lines

40

Monthly Boise Airport Wind Rose

January

February

March

April

May

June

41

July

August

September

October

November

December

urban wind turbine senior design project final...

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