1. Sol Searcher
Team T3
Prepared For: Dr. Lukas Swan
Prepared by: Cohen Poirier, Chris Newton, Bryan Ellis, and Qing Dong
Due: April 6th 2016
2. i
Abstract
This report is intended to show the design process and results of the solar tracking system project
completed. Referencing Dr. Lukas Swan's project introduction, the project purpose is defined as
to build a solar tracking system operating on a condensed solar day while adhering to solar
zenith, azimuth equations, and to use the final design in a class competition to pump as much
water as possible. Unique to the final design referenced in this report is the solar azimuth
tracking motion controlled by a compound gear system and solar altitude tracking motion
controlled by a dual winch system. Through the design process, essential and important design
requirements were created. Prototyping was an important part of the design process because it
accelerated design reiteration and idea generation. Testing was completed in order to calibrate
the mechanism of altitude motion and azimuth motion to be ready for competition. After
competing, the final design was able to pump 1090 mL of water, finishing 12th place. These
results are specific to solar tracking design referenced in the report. Upon completing the project,
the final design was evaluated on how well it met the design requirements, and suggestions were
made to improve the design. The final design was able to meet all of the essential requirements,
but failed to meet some of the important requirements. It was suggested that more calibration be
completed, and some tweaking to the compound gear system in order to improve the design.
3. ii
Table of Contents
List of Figures................................................................................................................................iii
List of Tables .................................................................................................................................iv
1. Introduction............................................................................................................................... 1
1.1 Project Purpose ................................................................................................................... 1
1.2 Theoretical Background..................................................................................................... 2
2. Design Requirements ................................................................................................................ 4
3. Design Process........................................................................................................................... 5
3.1 Design Selection................................................................................................................... 5
3.2 Data Collection.................................................................................................................... 6
3.2.1 Altitude Rotation.......................................................................................................... 6
3.2.2 Azimuth Rotation......................................................................................................... 8
3.3 Design Development............................................................................................................ 9
3.3.1 Support System ............................................................................................................ 9
3.3.2 Altitude Tracking....................................................................................................... 11
3.3.3 Azimuth Tracking...................................................................................................... 13
4. Design Performance................................................................................................................ 16
4.1 Design Evaluation ............................................................................................................. 16
4.2 Competition Performance ................................................................................................ 18
4.3 Proposed Corrections ....................................................................................................... 18
5. References................................................................................................................................ 19
Appendix A .................................................................................................................................. 20
4. iii
List of Figures
Figure 1: Solar Azimuth and Altitude angle versus time………………………………………….3
Figure 2: Solar Azimuth and Altitude angular velocity versus time……………………………...3
Figure 3: Organization of Kit Contents…………………………………………………………...5
Figure 4: Trigonometric Relationships of Altitude vs. Winch……………………………………7
Figure 5: Comparison of Winch and Altitude……………………………………………………..8
Figure 6: Half-Day Azimuth Angle vs Time……………………………………………………...9
Figure 7: Panel Racking Assembly………………………………………………………...…….10
Figure 8: Front view of the base support system assembly………………………..…………….10
Figure 9: Top view of the base support assembly………………………………………………..11
Figure 10: Altitude motor and winch assembly………………………………………………….11
Figure 11: Detailed view of Altitude mechanism assembly…………………………………..…12
Figure 12: Off-Set Winch………………………………………………………………………..13
Figure 13: Gear Section Connection………………………………………………………..……13
Figure 14: Azimuth System……………………………...………………………………………14
Figure 15：Completed Azimuth System.......................................................................................15
5. iv
List of Tables
Table 1: Kit Contents……………………………………………………………………………...1
Table 2: Desired Angular Velocity and Required Reduction…………………………………......9
Table 3: Pinion and Gear Combinations………………................................................................14
Table 4: Gear Section Arcs............................................................................................................15
Table 5: Final Design Evaluation Based on Design Requirements and Performance...................16
6. 1
1. Introduction
1.1 Project Purpose
Water is essential to everyday life from having showers, and washing dishes to the most basic
aspects of survival. In remote locations access to this precious recourse is often limited, and off-
grid power is required to transport water to the places it is needed. Photovoltaic modules are an
excellent solution to produce electricity in remote locations for pumping water.
The purpose of this project was to design and build a solar tracking system, with the intention to
optimize the energy output from the photovoltaic modules. The project includes the design of a
solar tracking system, PV module racking system, and accommodation for electrical
interconnections. Maximum electricity generation is achieved when the photovoltaic modules are
perpendicular to the sun.
While design process began in early February, the materials to complete the task were not
revealed until February 22nd. Table 1, from Dr. Swan’s Design Kit Contents list 2016, shows the
contents of the kit delivered. The kit is broken into categories with a range of structural
components, a limited amount of rapid prototype material, 4 PV modules and two Tamiya 6-
speed gearboxes.
Table 1: Kit Contents
7. 2
1.2 Theoretical Background
Maximum electrical energy and efficiency is achieved when a PV module is
perpendicular to the sun rays.
Electric powered pumps are used to push water through a pipe, usually against gravity.
The sun tracks across the sky differently each day of the year.
Photovoltaic modules directly convert sunlight into electrical energy in a quiet and
renewable manner
Solar Tracking is governed by a series of mathematical equations that specify the location of the
sun in the sky at a given time. These equations were provided by Dr. Lukas Swan’s Project
Introduction [2] they are as follows:
𝛿=23.45×sin(360*(284+𝑛)/365) (1)
Where the angle of declination, 𝛿, is dependent on day of year, 𝑛, from 1 to 365.
𝜃𝑧=acos[sin(𝛿)*sin(𝜙) + cos(𝛿)*cos(𝜙)*cos(𝜔)] (2)
Where 𝜃𝑧 is the solar zenith angle, which is dependent on the angle of declination, 𝛿, the
latitude, 𝜙, and the hour angle, 𝜔. For this problem, the angle of declination is 23.45 degrees, the
latitude of Halifax is 45 degrees, and the hour angle of 15 degrees per hour has been reduced to
1.5 degrees per second.
𝛼𝑠=90°−𝜃𝑧 (3)
Where 𝛼𝑠 is the altitude angle measured from the horizon to the sun, which dependent upon the
solar zenith angle, 𝜃z.
𝛾𝑠=[(+1 IF 𝜔≥0), (−1 IF 𝜔<0)]×|acos(cos(𝜃𝑧)*sin(𝜙)−sin(𝛿)*sin(𝜃𝑧)*cos(𝜙))| (4)
Where 𝛾𝑠 is the solar azimuth angle, which is dependent upon the sign (+/-) of the hour angle, 𝜔,
the solar zenith angle, 𝜃𝑧, the angle of declination, 𝛿, and the latitude of the location, 𝜙.
In order the most water, a design that keeps the face of the solar panels perpendicular to the light
source at the focal point 24” above the base plate is preferred. In order to achieve maximum
efficiency, the design should be able to track the sun as accurately as possible to keep the solar
panels perpendicular to the sun’s light at any given time.
Based on equations 1 through 4, an excel spreadsheet was plotted that condensed a 24 hour day
into 4 minutes. Figure 1 shows a plot time vs. altitude angle and time vs. azimuth angle
superimposed on one another. From the information provided Figure 1 specifications in the
designs could be made to meet the requirements stated. The PV cells need to be facing the light
source to produce maximum power output. Moreover, Figure 1 shows that while the day may be
240 seconds in duration, there is only 155 seconds of sunlight. Since competition only includes
the time of sunlight, design was completed accordingly.
8. 3
Figure 1: Solar Azimuth and Altitude angle versus time
Figure 2: Solar Azimuth and Altitude angular velocity versus time
9. 4
Figure 2 shows azimuth and altitude angular velocity versus time. Based on figures 1 and 2, it
was agreed upon that the best method to track the movement of the sun would be to approximate
the speed of the altitude angle as linear, and to produce a variable speed system for the azimuth
angle.
2. Design Requirements
Design was conducted under the following constraints as provided in by Dr. Lukas Swan’s
Project Introduction [2] these are the most basic requirements for the design parameters.
Use only the materials in the kit.
Have a 12” by 12” by ¾” plywood baseplate with nothing protruding below, and nothing
on the upper edge to allow for clamping.
Use only fixed voltages on DC power supplies.
The panels must not translate in any direction (X, Y, Z) more than 4” from the focal
point.
Design based on a 4 minute solar day.
The effective competition day is Jun 21 in Halifax NS (𝝋 = 45°), which is day n = 172.
From these basic requirements, two categories were made to provide additional requirements to
help in the design and construction phases. Broken into two categories, essential and important
requirements.
Essential Requirements Important Requirements
Free standing on the provided base Variable speed about the altitude and
azimuth directions
Two axis of rotation, independently or
together
Simple design, for ease of construction
and testing
Must have approximately 240 degrees
of rotation about the azimuth
Accurate tracking of solar angles
Must have approximately 70 degrees of
rotation about the altitude
Strong design that is robust and sturdy
to account for possible real world
weather conditions
Accommodation for electrical
interconnections
Ascetics
10. 5
3. Design Process
3.1 DesignSelection
From the onset of design development, material usage was to be prioritized and initial design
was conducted accordingly. Figure 3 shows the organization of the kit contents upon receiving
the kit. Close attention to material availability and exhaustion was to be kept in mind through the
building, and reiteration of the design process.
Figure 3: Organization of Kit Contents
From the beginning of the design process, three separate design categories were created, they are
as follows: Azimuth motion, altitude motion, and support system. Several designs were produced
for each category, and each design was evaluated based on a design selection matrix that
corresponded to each category. The frame mount that was initially chosen for the frame design
was a feasible design when the kit was received. However, the rack design still had to be slightly
altered. The goal was to produce a support design that used the least amount of material to
provide the most stable and clean design.
11. 6
To track the solar altitude motion, a system that allowed the panels to start in a vertical
orientation, decline back to about 29 degrees from the horizontal, and then incline back to the
vertical orientation was needed. The chosen winch design, after some alterations, was the most
feasible choice with the items available in the kit. The theory of the altitude control is that each
winch has a set amount of string, to start the string is fully wound around the spool and as it
starts operation the string is let out, the counter force pulls the panels back keeping tension on the
string. Once all the string has been released, as a result of it being fixed to the winches it begins
winding itself up pulling the panels back down against the counter force.
In order to track azimuth motion, a variable speed system was required, preferably one that is
able to mirror itself after midday as the function describing the azimuth motion is mirrored about
the halfway point. The original selected design would make use of a rack and pinion system with
different levels to mesh at specific times. After review, it was decided that this would require far
too much material. Instead of having a long pinion system, a tree of gears would cause rotation
of the azimuth. A compound pinion would require much less room and a rack and would still
provide the same variability as the original idea.
3.2 Data Collection
Important information to consider when designing the components for the solar altitude and
azimuth tracking mechanisms are the specifications of the Tamiya 6-Speed Gearboxes provided.
From the speeds at which the components need to operate in combination with the approximated
RPMs found on a Tamiya specification sheet [1], the motors must turn as slow as possible. The
recommended operating range of the motors is 1.5V – 4.5V, providing a range of 6300 to 9400
un-loaded RPMs. Therefore, the components should be designed to operate within these
specifications with some room for adjustment. As an example at 1.5V if the motors are set up as
intended on the ratio of 1300.9:1 the output will be close to 5 RPM without load.
3.2.1 Altitude Rotation
To solve the altitude parameters a relationship between the height of the winch (L), length of the
rope at given time (l), and altitude angle (a). As shown in Figure 4 the focal point is where the
arrow hits the black line, and based on trigonometric relations the inside angle was also found to
be the parameter (a).
12. 7
Figure 4: Trigonometric Relationships of Altitude and Winch
In order to relate the length of the string to the altitude angle it was necessary to introduce
variables to find and equate relationships.
L = y + z (5)
Where L is the length of a PV module, y is the vertical distance from a tilted panel’s bottom edge
to the focal point, and z is the difference between L and y.
b = Lsin(a) (6)
Where b is the horizontal distance from the vertical axis to the bottom edge of the title panel, and
a is the altitude angle.
Y = Lcos(a) (7)
Where y is the vertical distance between the tilted panel’s bottom edge from the focal point, and
a is the altitude angle.
L = √𝑧2 + 𝑏2 (8)
Where l is the distance from the bottom edge of the tilted panel to its vertical projection.
By finding angular velocity and because it was known that the winch will have some radius, R,
rotating at a frequency 𝑓, in revolutions per second, the length of rope as a function of time could
be found.
𝑙 = 2𝜋𝑓𝑅𝑡 (9)
13. 8
From equations (5), (6), (7), and (8) altitude angle in terms of length was found to be;
𝑎 = cos−1
(1 −
(2𝜋𝑓𝑅𝑡)2
2𝐿2 ) (10)
Figure 5: Comparison of Winch and Altitude
By plotting this equation in excel variables could be manipulated in order to find a frequency and
radius that fit the requirements. Taking into account the need to be operating around 5 rpm, the
winch will have a diameter of 2cm, placed 30 cm down the stand from the focal point. Figure 5
shows the approximated altitude position of the sun as a function of time (in red), compared to
the actual altitude position of the sun as a function of time (in blue).
3.2.2 Azimuth Rotation
The azimuth pathing of the sun presents a different set of challenges; requiring more variable
speeds but only in one direction. Also, the azimuth path function mirrors itself beginning at
noon. This means that to determine required angular velocities only half of the graphs shown in
figure 1 and 2 need to be considered. Analyzing the first half of the solar day, it was determined
that there were three distinct regions where the velocity could be approximated as linear without
significant losses in accuracy. Figure 6 shows the plot of azimuth angle vs time for the first half
of the solar day. Also shown are the linear approximations for the three distinct sections.
14. 9
Figure 6: Half-Day Azimuth Angle vs Time
Rounding the velocities to one decimal place, estimates of 1, 1.9 and 3.3 deg/s were used for
design purposes. Using an estimated motor input of 5 deg/s the input reduction from motor to
shaft was calculated and is presented in Table 2.
Table 2: Desired Angular Velocity and Required Reduction
Motor Speed (deg/s) Desired Shaft Speed (deg/s) Required Reduction
5 1 5
5 1.9 2.63
5 3.3 1.52
3.3 DesignDevelopment
3.3.1 Support System
To support the combined weight of the PV modules a mount made of the ½” plywood (Figure A-
11) was used in the center. This support reached up higher on panels above and below the center
axis offering back support this was connected to the existing holes in the PV panels. Additional
panel connection wood was added made of ¼” plywood (Figures A-8, A-9) connected along the
central axis fastening the panels above and below together. On the top and bottom of the
modules two slender basswood panel connection (Figure A-10) pieces were used that served dual
purposes. Each piece fastened adjoining left and right panels together, the bottom piece also
severed as an attachment for the altitude string and the top for the elastic band counter pull.
Basswood was used as altitude pivot joint (Figure A-12) connecting the modules to the PVC
y = 1.0267x - 168.58
y = 1.8801x - 245.9
y = 3.3152x - 398.93
-140
-120
-100
-80
-60
-40
-20
0
20
40 50 60 70 80 90 100 110 120
AzimuthAngle(deg)
Time (s)
15. 10
shaft. In order for the modules to rotate around the shaft about the altitude direction the small
PVC was used as an axel fitting through the shaft that was centered between both basswood
pivots. Figure 7 shows the assembly of the racking components.
Figure 7: Panel Racking Assembly
For the base support system shown in figures 8 and 9, three triangle legs (Figure A-16)
optimized stability while leaving room for the azimuth motor to be installed and driven. The
three support legs attached to a square guide (Figure A-15) a portion of the way up the shaft to
prevent the structure from tipping from the weight of the panels. Attached to the baseplate
(Figure A-6), was a circular guide (Figure A-7) which would contain ball bearings allowing for
ease of rotation about the vertical axis.
Figure 8: Front view of the base support system assembly
16. 11
Figure 9: Top view of the base support assembly
3.3.2 Altitude Tracking
As dictated by the calculations for the altitude system the winch control is mounted on the ABS
shaft (Figure A-1) the same distance down as the height of a single PV cell. The winch system
contains two spools that are mounted directly to either side of the drive shaft of the Tamiya
motor. The motor is mounted onto a small piece of ¼” plywood screwed directly into the ABS
shaft, the assembly of the altitude system can be seen below in Figure 10. The Altitude system
contains two parts, a counter force in the form of two elastic bands and the winch control, both
can be seen below in Figure 11.
Figure 10: Altitude motor and winch assembly
17. 12
Figure 11: Detailed view of Altitude mechanism assembly
The counter force mechanism is a long piece of basswood (Figure A-4) mounted off the back of
the shaft near the top, the length of the basswood functions as a moment arm. Two elastic bands
are mounted to the end of the basswood which are secured by squeezing the elastic bands
between two pieces of ¼” plywood (Figure A-5) on either side of the moment arm by tightening
two nuts. The same method of connection is used to fasten the elastic bands to the top of the
panels.
The winch system is made up of two spools, each comprised of two spool caps (Figure A-14),
and one spool center (Figure A-15). Initially it was intended to reduce torqueing the motor on the
PVC shaft left or right but after construction it was found they served a better purpose. At the top
of the altitude cycle when the panels are in the fully declined position, because of the size of
each spool, as the string winds there was a section of delay causing the panels to pause at the top.
The string would release tension and take half a turn to return to tension in order to pull the
panels down. To fix this problem the string was off set on each winch, one at the top and one at
the bottom. Figure 12 illustrates the off-set, the blue dots represent where the strings are fixed to
each winch. This resulted in the string of one spool being under tension on the way out while the
other’s string was slack being half a rotation ahead. When maximum altitude was reached, the
spool that was initially slack immediately started to pull back down effectively eliminating the
delay. To fasten the string to the bottom of the panel two small pieces of ¼” plywood were used
to fix two pulleys off of the panels. This was done in order to cause the string to always pull
downward, instead of at an angle, reducing torque on the motor.
18. 13
3.3.3 Azimuth Tracking
To estimate the azimuth path, a system of gears was developed to provide three unique speeds
that were mirrored halfway through the run. To do this, three pinions (Figures A-18 to A-20)
would be used to mesh at specific points with gear sections (Figures A-21 to A-23) attached to
central ABS shaft of the structure. Since the gear sections share a center point with the pipe they
also have the same angular velocity. To attach the gear sections to the pipe,
15
64
inch holes were
drilled into the pipe which allowed a tight fit for the section plug as seen in Figure 13.
Figure 13: Gear Section Connection
The holes were spaced so that the gear sections would not overlap vertically or horizontally.
Vertical spacing allowed for the gears to only mate with the desired pinions and avoid contacting
Figure 12: Off-Set Winch
Representation
19. 14
larger pinions as seen in Figure 14, horizontal spacing can prevent sticking when transitioning to
the next gear section.
Figure 14: Azimuth System
Because the sections are extensions of the shaft, they needed to be able to fit inside the structural
supports. This meant that the gear sections would have a maximum outer radius equal to the
radius of the central support circle (Figure A-7) and a minimum base radius equal to the radius of
the ABS shaft (Figure A-1). The system designed accomplishes this, with a maximum size gear
section having an outer radius of 47 mm and the smallest gear having a base radius of 23.81 mm.
Gears and pinions design were driven by the results of the first section consisting of the smallest
pinion (Figure A-18) and largest gear section (Figure A-21). Since the center to center distance
for all levels of the gear system had to be the same the lower sections had to adhere to this
restriction, requiring the system to deviate from the desired velocity reductions. Table 3
highlights the resulting gear and pinion combinations as well as the desired reduction and
designed reduction.
Table 3. Pinion and Gear Combinations
Tier Pinion Diameter
(mm)
Gear Diameter
(mm)
Desired
Reduction
Actual
Reduction
1 (Figure A-18
and A-21)
18 90 5 5
2 (Figure A-19
and A-22)
32 76 2.63 2.375
3 (Figure A-20
and A-23)
42 66 1.52 1.57
The length of each tier section was determined by referencing the half day angle vs time graph
(Figure 6). From this the desired amount of rotation at each speed can be determined. For
example, the first speed rotates the shaft for the first ~53 deg and so the desired arc of the gear
20. 15
section for speed one is 53 degrees. To ensure proper functioning, angles were adjusted so that
there were full gear teeth for each section. Table 4 summarizes the final gear section arcs for the
three speeds.
Table 4. Gear Section Arcs
Section Desired Arc (deg) Actual Arc (deg)
1 53 55.6
2 26 20
3 44 45
Total 123 120.6
All values in Table 4 represent half of the solar day; Sections one and two were doubled by using
two separate but identical gear sections (Figures A-21 and A-22) and section three was created as
one gear section (Figure A-23). This resulted in a total rotation capability of roughly 241 degrees
Because the output speed motor was much higher than 5 deg/s a separate pinion (Figure A-24)
and gear (Figure A-25) were developed. The motor reduction pinion was attached directly to the
motor shaft using a nut and epoxy. The motor reduction gear was glued to the bottom of the
compound gear tree and served as the base as seen in figure 14. This reduction system had fewer
restrictions and was able to reduce the angular velocity from 1/3 of the motor shaft speed.
Figure 15. Completed Azimuth System
21. 16
Once complete, the motor reduction gear and the three tier pinions were aligned with a 3/16
piece of dowel placed through a hole in their respective centers and glued together with epoxy as
seen in Figure 14 and 15. The dowel was glued into a structural support which also held the
motor in the proper position to transmit power as seen in figure 15. The base is positioned so that
the center of the pinions is the required 54 mm from the center of the ABS pipe.
4. Design Performance
4.1 DesignEvaluation
Table 5: Final Design Evaluation Based on Design Requirements and Performance
Table 5 shows how the design was evaluated based on the requirements that were outlined as
important at the beginning of the project, evaluated by 4 categories simplicity, size, robustness
and accuracy. The requirements are restated from section 2 below. Each criteria is weighted
evenly and the score given in the overall build category is an average of the three scores given
each design category of azimuth, altitude and structural components.
Essential Requirements Important Requirements
Free standing on the provided base Variable speed about the altitude and
azimuth directions
Two axis of rotation, independently or
together
Simple design, for ease of construction
and testing
Must have approximately 240 degrees
of rotation about the azimuth
Accurate tracking of solar angles
Must have approximately 70 degrees of
rotation about the altitude
Strong design that is robust and sturdy
to account for possible real world
weather conditions
Accommodation for electrical Ascetics
Criteria Azimuth Altitude Structural
Components
Overall Build
Simplicity 2 4 4 3.3
Size 5 4 4 4.3
Robustness 4 3 4 3.7
Accuracy 3 3 N/A 3
Performance N/A N/A N/A 1090 mL
67% of maximum
22. 17
interconnections
Of the essential requirements, every goal was met. The design had dual axis tracking in the
azimuth and the altitude, it was free standing and had the ability to support the weight of the
solar panels with ease. Accommodation was also made for the electrical interconnections. Each
aspect support system, altitude and azimuth met the important requirements differently and are as
follows.
The rack and support system design is strong, while using minimal materials. Each panel has
three connections of support resulting in a sturdy design without the need to drill into the
aluminum to attach the panels together. The basswood panel connection supports (Figure A-10)
at the top and bottom are an efficient use of material as they serve to as structural pieces and are
essential in the performance of the altitude. The base could be more stable by adding a fourth
leg, this was a tradeoff made because the space was needed to mount and drive the azimuth
control. The design was created with a smart use of materials and even without the fourth leg, it
was an extremely robust end product. The support system was simple, clean and ascetically
pleasing.
The winch design was simple taking up minimal room on the shaft of the ABS pipe. The spools
were relativley easy to construct and the elastic counter force mechanism proved to be a simple
solution instead of using springs or a counter weight. By mounting the spools directly to the
motor, space was reduced, but at a tradeoff. The tradeoff being that the only way to slow down
the altitude tracking was to change the voltage supplied to the motor or to change the size of the
spools, as the design provdied no room for gear reduction. Another aspect of this tradeoff is that
because there was no reduction, the motor was required to handle all the torque directly.
Secondly, two spools were initially introduced to reduce the force on one side or the other of the
motor so that it could pull and release evenly. However, since there was a delay section at noon
in the solar day, it was found that accuracy could be improved if the points where the strings
were fastened were offset one at the top and bottom. Despite these concerns, the design proved
strong enough to handle the uneven stresses. For the accuracy the altitude had full the full range
of motion required, but only accunted for linearly approximated speed. Because of this aspect
some accuracy was sacraficed.
The lack of accuracy in following the azimuth is likely due to a mix of some tradeoffs to the
design process as well as limitations of motor speeds available for competition. During the
design process some errors were predicted because the gear system can only produce linear
speeds. It was predicted that this would cause some error but that the approximations would not
cause significant losses to production. The problem with the linear speeds was increased by the
design decision to only use one diametric pitch for the gears for simplicity. Because of this
limitation and the limitation of center to center distance there was designed error between the
three estimated speeds for the path and the ones produced from the design. Finally, the gear
design requires a specific motor output in order to function correctly. The designed system was
produced before fully determining what speeds would be available over the range of voltages to
the motor. This oversight meant that there needed to be a decision about whether to rotate
slightly too fast or too slow, resulting in more error during competition.
23. 18
4.2 CompetitionPerformance
During competition, each group was given two attempts to pump the most water possible. The
final design referenced in this report pumped 790 mL on the first attempt, followed by 1090 mL
on the second attempt, placing 12th in the competition. For the first run the panels’ electrical
connections were improperly done resulting in only three panels working for the first attempt.
This is a result of not testing with the water pump prior to the competition day. In the second
attempt the voltages used allowed the design to more accurately track the sun with all four panels
producing electricity. Overall the design could have performed better if more testing had been
done. In the last column of Table 5 the evaluation of the final design based on the initial design
requirements and competition performance is shown. The last category is for overall
performance and presents how the outlined design did in competition.
4.3 Proposed Corrections
In order to improve the final design especially performance, more testing and calibration was
needed. Additionally, tracking accuracy was limited due to minor inconsistencies between the
azimuth and altitude components compared to the theoretical goals. Moreover, because of the
nature of the design for each component only linear approximations for the speeds were
provided. An average score of 3 for accuracy in the overall build category of Table 5 reflects
these aspects. Extensive calibration and testing would have helped to mitigate these issues,
providing more time to change the tracking components accordingly. Since both aspects were
approximated however even with extensive testing the design never had the capacity to achieve
perfect results, the only way to change this would be to go with a different design.
For the azimuth system the most significant improvement to be made to the design would be to
further explore different diametric pitch options to better match the calculated estimates for
angular velocity. Changes to the diametric pitch allows for more potential reductions while
maintaining the same center to center distance to the pipe. Another improvement to the azimuth
would be to further explore output speeds of the motor and creating a different set of gears for an
initial reduction that produced a compound pinion angular velocity of 5 degrees per second.
Finally, adding more tiers to the compound pinion and gear section design may produce a more
accurate model as more linear divisions of the curve will be closer to following the true curve.
The main constraint of the number of tiers is that the transitions between levels can be difficult to
produce consistently and more tiers would require more materials compared to minimal increases
in performance.
