as solar charging station design report
TRANSCRIPT
Associated Students: Solar Charging Station
Title Pa
Maytham Alhaddad
Salam Ali
Erik Marquis
Jairo Orozco
Chao Vang
MECH/MECA 440A
Final Design Report
May 17, 2016
Department of Mechanical and Mechatronic Engineering
and Sustainable Manufacturing
California State University, Chico
Chico, CA 95929-0789
ii
Executive Summary
The AS Solar Charging Station project was brought forth to the Sustainability Fund
Allocation Committee (SFAC) by Trenten N. Bilodeaux, Director of the Panel Law Project
Community Legal Information Center (CLIC) and Dr. Gregory Kallio, Professor of Mechanical
and Mechatronic Engineering, in an effort to provide a visible campus element that underscores a
commitment to sustainability.
The primary objective of this project is to design and implement an off-grid solar charging
station that will allow up to six students to charge and use their portable electronic devices.
Currently, there are no outdoor facilities for charging electronic devices on campus. The station
adds a visual element of campus sustainability, while teaching students of the technologies
associated with solar energy. The Solar Charging Station features thin-film photovoltaic solar
modules, a 14’ x 14’ pyramidal shade structure, security lighting, dual GFCI/USB outlets, auxiliary
charging cords, sustainably sourced wood, as well as access to an integrated monitoring system of
the charging stations performance. Furthermore, the station provides up to 1457 kWh/day to allow
up to 18 devices (phones, laptops, tablets) to be charged for the 12 hours of operation, all while
providing two days of autonomy on days of overcast and little sun via a 780 Amp hour (Ah) battery
bank.
iii
Acknowledgements
Sponsor
Sustainability Fund Allocation Committee, Associated Students
Ricardo Jacquez
Dean, College of Engineering, Computer Science and Construction Management
Ben Juliano
Interim Assoc. Dean, College of Engineering, Computer Science and Construction Management
Dr. Gregory Kallio
Professor of Mechanical and Mechatronic Engineering
Steven Eckhart
College of Engineering, Tech Shop Supervisor
Dave Gislon
College of Engineering, Tech Shop Technician
Scott Vanni
Lecturer of Mechanical and Mechatronic Engineering
David Sprague
Assistant Director of Design, Construction and Maintenance
Tom Ussery
Academic Facilities Administrator
Jenny Dempsey
Regional Manager, USA Shade & Fabric Structures
Dennis Partington
Network Manager, Network Operations
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Table of Contents
Executive Summary.................................................................................................................... ii
Acknowledgements.................................................................................................................... iii
List of Figures............................................................................................................................. vi
List of Tables.............................................................................................................................. vii
Nomenclature.............................................................................................................................. viii
1. Background and Introduction.................................................................................................. 1
2. Problem Definition................................................................................................................. 2
3. Concept Generation................................................................................................................ 3
4. Final Design............................................................................................................................ 5
5. Detailed Analysis and Design................................................................................................ 6
5.1 Solar Access.............................................................................................................. 6
5.2 Electrical Load Analysis........................................................................................... 7
5.3 PV module Selection................................................................................................ 10
5.4 Battery Sizing and Selection.................................................................................... 10
5.5 PV Array Sizing and Charge Controller Selection.................................................. 11
5.6 Inverter Sizing and Selection................................................................................... 12
5.7 Wire and Breaker Sizing.......................................................................................... 12
5.8 Educational Signage and Monitoring Equipment.................................................... 14
5.9 System Integration................................................................................................... 15
5.10 Shade Structure and PV Mounting........................................................................ 16
5.11 Seating: Table and Benches....................................................................................18
5.12 Testing Results and Interpretation..........................................................................24
6. Planning................................................................................................................................. 29
7. Budget.................................................................................................................................... 29
8. Justification............................................................................................................................ 32
9. Discussion.............................................................................................................................. 33
10. Recommendations................................................................................................................34
References..................................................................................................................................35
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Appendix A: Load Analysis and Equations..................................................................................A1
Appendix B: PUGH Analysis...................................................................................................... B1
Appendix C: Component Spec Sheets..........................................................................................C1
Appendix D: Wiring Diagram.......................................................................................................D1
Appendix E: CAD Drawings.........................................................................................................E1
Appendix F: Full Test Plan and Data ...........................................................................................F1
Appendix G: Budget Analysis......................................................................................................G1
Appendix H: Login Information...................................................................................................H1
Appendix I: Gantt Chart.................................................................................................................I1
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List of Figures
Figure 1: Solar Charging Station Location......................................................................................4
Figure 2: Design Concept 1.............................................................................................................4
Figure 3: Design Concept 2.............................................................................................................4
Figure 4: Final Design Concept.......................................................................................................6
Figure 5: MiaSole FLEX-01, 220W Module.................................................................................10
Figure 6: Login Display Location..................................................................................................15
Figure 7: Single Post, Pyramidal Shade Structure.........................................................................17
Figure 8: PV Array Arrangement..................................................................................................18
Figure 9: Table and Bench Final Design Concept.........................................................................19
Figure 10: Battery Storage.............................................................................................................20
Figure 11: Tabletop Decal.............................................................................................................21
Figure 12: Center Console Component Storage............................................................................22
Figure 13: GFCI/USB Outlets and Auxiliary Cords......................................................................23
Figure 14: Evening Lighting at Location.......................................................................................24
Figure 15: State of Charge Test ....................................................................................................26
Figure 16: Budget Breakdown.......................................................................................................31
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List of Tables
Table 1: Must Do Engineering Specifications...............................................................................3
Table 2: Average Sun Hours..........................................................................................................7
Table 3: Average Laptop Charger Output......................................................................................8
Table 4: Average Cell Phone Charger Output................................................................................8
Table 5: Average Tablet Charger Output.......................................................................................9
Table 6: Load Calculation..............................................................................................................9
Table 7: Wire Sizing......................................................................................................................13
Table 8: Breaker Sizing.................................................................................................................14
Table 9: Battery State of Charge...................................................................................................28
Table 10: Section Budget Breakdown...........................................................................................32
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Nomenclature
𝑉𝑜𝑐,𝑀𝑎𝑥 Maximum Open Circuit Voltage
𝑉𝑜𝑐,𝑆𝑇𝐶 Standard Test Condition Open Circuit Voltage
𝛽𝑜𝑐 Open Circuit Temperature Coefficient
𝑇𝑎𝑚𝑏,𝑚𝑖𝑛 Minimum Ambient Temperature
𝐼𝑆𝐶 Short Circuit Current
𝐼𝑐𝑐,𝑚𝑎𝑥 Maximum Charge Controller Current
VDI Voltage Drop Index
𝑉𝑚𝑝𝑝 Voltage at Maximum Power
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1. Background and Introduction
Starting in 2006, the Associated Students (AS) Sustainability Fund was created when
students voted to fund the creation of the AS Sustainability Program and a fund for student-driven
sustainability projects. Approximately $80,000 in funds are available annually for these projects.
The Sustainability Fund Allocation Committee (SFAC) is in charge of allocating funds to projects
each semester. The AS Solar Charging Station project was proposed to SFAC by Trenten N.
Bilodeaux, a student and Director of the Panel Law Project Community Legal Information Center
(CLIC) and Dr. Gregory Kallio, Professor of Mechanical and Mechatronic Engineering, in an
effort to provide a visible campus element that underscores a commitment to sustainability.
This project is intended to fulfill a technological need and an educational objective in the
area of sustainable energy. The technological need is a widespread demand for charging portable
electronics devices on campus, especially in an outdoor environment where students can gather
and enjoy the wonderful Chico climate. The educational objective is to provide a visible campus
element that underscores a commitment to sustainability while teaching students of the
technologies associated with solar energy. To date, no other physical entity exists on campus that
fulfills these goals in the area of solar energy. Currently, there are several solar charging stations
on the market for purchase; unfortunately, most are simply too expensive and do not provide
students the opportunity to implement the engineering design and fabrication process. Funding for
this project has been secured from SFAC in the amount of $12,000, with a contribution of an
additional $3,325 from the College of Engineering bringing the total amount of this project to
$15,325.
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2. Problem Definition
The problem is to design, build, and implement a solar photovoltaic (PV) charging station for
charging portable electronic devices. The design will incorporate University-approved seating
(table and benches) that are aesthetically integrated with the surrounding area. All this must be
considered, in addition to the following requirements:
The project must:
Be an off-grid system
Have educational signage
Have 120 VAC/Ground Fault Circuit Interrupter (GFCI) receptacles and Standard,
5VDC/2A max, USB receptacles
Have an emergency shutdown
Provide security lighting
Have all electrical components enclosed
Be aesthetically pleasing
Have seating for at least six people with 25% Americans with Disabilities Act (ADA)
access
Pass inspection by a licensed electrician
Be structurally robust
Have sufficient power and storage for six people charging typical devices (laptop and
smartphone) throughout the day
The project should provide:
A WIFI Hotspot
Shade
It would be nice if the project:
Has a system of cooling
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Collaborated with the Art Department for the aesthetics of the shade structure
The Solar Charging Station (SCS) will provide sufficient power and storage to charge all
electronic devices (smartphones, tablets and laptops) throughout the day. The “Must-Do”
quantitative engineering specifications are given in Table 1. The target values for power and
storage are determined as part of the design process (Section 5).
Table 1: Must-Do Quantitative Engineering Specifications
Requirements Engineering
Specifications Metric Method Conditions Target
Maximum
Footprint Area m2 Tape Measure BMU Location 8’ x 8’
Structurally
Robust Wind Speed mph
Manufactures
Specifications
Chico maximum
Wind Speed 85 mph
Sufficient
Power Power kW
Inverter
Specifications
6 People Using
Devices <0.685 kW
Sufficient
Storage Energy kWh
Battery
Specifications
Laptops, smart
devices and fans 1.45 kWh/day
3. Concept Generation
The site selected for the installation of the SCS is the Bell Memorial Union (BMU) outdoor
seating area. Of four other sites considered, the BMU location has the highest traffic of students
throughout the day, is most well-lit at night, and has comparable solar insolation. Figure 1 shows
the location of where the charging station will be installed. In order to provide accessibility and
provide adequate room for the station, one of the tables would have to be removed or placed in a
different location, pending the approval from the Associated Students.
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Figure 1: Solar Charging Station Location
Currently, there are several solar charging stations on the market for purchase in various
designs; however in keeping with the requirement that the SCS must be aesthetically pleasing and
integrated sympathetically with its surroundings, the design was based on the current seating, as
shown above. As Figures 2 and 3 illustrate, one design idea was to incorporate the same rectangular
seating in the SCS. Furthermore, as per customer requirement, the SCS will seat six people total;
seating for two people on each bench and two vacant areas at the ends of the table, reserved for
those with disabilities.
Figure 2: Design Concept 1 Figure 3: Design Concept 2
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Current solar charging stations on the market today utilize rigid, crystalline PV solar modules.
Unknown to many, there is an entirely different type of solar panel that can simply be rolled out
and attached using pressure sensitive adhesive (PSA). This type of module is known as thin-film
PV. In comparison, the crystalline solar module weighs, on average, about 10.4 kg (23 lbs),
whereas thin film modules can weigh as little as 2.3 kg (5 lbs). As opposed to crystalline modules,
which are installed on strong rooftops with a robost mounting system tilted at a fixed angle, thin
film modules can be rolled out and directly adhered to rooftops, polycarbonate fabric,
thermoplastic polyolefin and high density polyethylene (HDPE). This allows them to be installed
on various surfaces without racks or heavy support structures. The process of determining which
module to use for the SCS will be discussed more in detail in Section 5, as well as the battery bank,
charge controller, inverter and other solar components.
4. Final Design
With the customer requirements in mind and analysis complete, Figure 4 illustrates the final
design. Shown in the figure, the SCS will incorporate a pyramidal shade structure, thin-film solar
modules, multiple GFCI and USB receptacles, as well as auxiliary cords for various smart devices.
Among the features listed below, all electrical components will be enclosed within the benches
and center console, beneath the table top. These enclosures will each have locked, maintenance
doors to ensure easiest access to the components within. The detailed analysis and design of each
component will be discussed further in Section 5.
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5. Detailed Analysis and Design
The process for sizing and selecting the necessary components for an off-grid system are
as follows: solar access, measurements and analysis, electrical demand estimate, battery sizing,
module sizing, charge controller sizing, inverter sizing, wire sizing and breaker/fuse sizing. A step-
by-step analysis with corresponding calculations of theload analysis can be found in Appendix A.
5.1 Solar Access
It was necessary to collect details about the site of the project, which include effective sun
hours and longitude and latitude. Full-sky solar irradiation for Chico was computed by PVWatts,
a web source, and the Solmetric instrument, SunEye, was used for the shading analysis. Estimating
that the station will be in high demand 10 months (highlighted below) of the year and multiplying
the irradiation data from PVWatts by the percent solar access from the SunEye, the annual, average
sun hours per day is 4.2 hours, as shown in Table 2.
Figure 4: Final Design Concept
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Table 2: Average Sun Hours
Month Solar Radiation
( kWh / m2 / day )
SunEye Solar
Access
Fraction
Sun Hours with
Shading
(kWh/m^2/day)
January 3.52 0.19 0.6688
February 3.88 0.494 1.91672
March 5.17 0.811 4.19287
April 6.32 0.853 5.39096
May 7.25 0.864 6.264
June 7.48 0.888 6.64224
July 7.49 0.865 6.47885
August 7.21 0.860 6.2006
September 6.82 0.843 5.74926
October 5.54 0.747 4.13838
November 3.71 0.272 1.00912
December 3.12 0.170 0.5304
Average for
SCS 5.65 4.19
5.2 Electrical Load Analysis
Estimating the electric load is a key component of the process and requires careful
consideration. As previously mentioned, there will be seating for six people with 120V, GFCI and
USB receptacles. The first step was to determine the average charger output of all the devices that
will likely be plugged into the receptacles, i.e. laptops, smartphones (Android and iPhone), and
tablets. As Table 3 illustrates, the average output/power for many name brand laptops is
approximately 80 W. For various smart phones, the average output is approximated at 10 W, as
Table 4 demonstrates. Lastly, the average output for several tablets was tabulated at 15 W (see
Table 5 below).
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Table 3: Average Laptop Charger Output
Laptop Brand Potential Difference
(V)
Current
(A) Power (W)
APPLE 16.5 3.65 60.225
ASUS 19 2.37 45.03
ACER 19 3.42 64.98
ALIENWARE 19.5 7.7 150.15
DELL 19.5 4.62 90.09
GATEWAT 19 4 76
HP 19 4.72 89.68
LENOVO 20 3.25 65
SONY 19 4.74 90.06
SAMSUNG 19 3.33 63.27
TOSHIBA 19 3.95 75.05
FUJITSU 19 4.22 80.18
Average 18.96 4.16 79.14
Table 4: Average Cell Phone Charger Output
Cell Phones Potential Difference
(V) Current (A) Power (W)
Apple Iphone Charger 5.1 1 5.1
Samsung Smart Phone 7 2 14
Samsung Smart Phone 9 2 18
Blackberry Classic 5 0.85 4.25
Blackberry Passport 5 1.3 6.5
Average 6.22 1.43 9.57
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Table 5: Average Tablet Charger Output
The maximum load of the system was assumed when all eight 120V and 4 USB receptacles
are in operation, in conjunction with four enclosure cooling fans; however, the assumption that the
system will rarely, if ever, be fully seated and serving eight laptops and/or eight tablets and phones,
can be made. In addition, the assumption was made that each device would be used six days a
week; however the hours of operation for each differ, as Table 6 shows. The estimated average
daily use is 1457 Wh/Day.
Table 6: Load Calculation
Tablets Potential
Difference (V) Current (A) Power (W)
Apple iPad & iPad mini wall
charger 5.2 2.4 12.48
Apple USB cord 5.1 2.1 10.71
USB Power Adapter /
Charger for Samsung Galaxy 5 2 10
Sony Xperia Z4 Tablet 5 1 5
Toshiba - Excite tablet 12 3 36
Average 6.46 2.1 14.84
Appliance Quantity Watts Minutes
On/Hour
Hours
On/Day
Days
On/Week
Average
Watt
Hours/Day
Max Watt
Hours/Day
Laptops 4 80 60 2.5 6 960 1120
Cell Phones
(Andriod &
iPhone)
6 10 60 1.5 6 128 150
Tablets 4 15 60 1 6 102 120
Fans 3 8 60 12 6 267 312
Total Average Watt-Hours/Day: 1457
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5.3 PV Module Selection
The selection of which PV module to use, thin-film or rigid, began with a PUGH analysis
(refer to Appendix B). Using the Panasonic Hit Power 240S rigid module as the datum, various
thin-film and rigid PV panels were analyzed based on weight, dimensions, efficiency, warranty,
ease of installation and cost per Watt. The MiaSole FLEX-01, 220W module is the best option as
it is significantly lighter and smaller in dimension, as well as easier to install, than the rigid panel
(refer to Appendix C). Not only does the MiaSole FLEX-01, 220W module excel in the areas
mentioned above, the power output of the thin-film modules is less affected by high temperatures
and shading, meaning that the efficiency is slightly higher than rigid panels. As Figure 5 shows,
because of the modules thin and sleek design, the chance of vandalism and theft are reduced as the
flexible modules will not shatter if struck by debris.
Figure 5: MiaSole FLEX-01, 220W Module
5.4 Battery Sizing and Selection
The battery bank must meet the load demands without risk of more than 50% discharge or
producing harmful gases of the batteries. Per the customer requirements, the SCS must be easy to
maintain; thus Absorbent Glass Mat (AGM) batteries will be used. AGM batteries are lead-acid
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batteries, one of the safest lead acid batteries as there is little chance of a hydrogen gas explosion
or corrosion when in use and need minimal maintenance.
To size the battery bank, the daily load is divided by inverter efficiency, desired system
voltage, depth of discharge, and the battery temperature modifier. The days of autonomy are an
important factor in sizing the system. It is essentially a safety factor to account for days of overcast
and even modular malfunction. For this system, two days of autonomy was chosen as the stations
GFCI and USB outlets will completely shut down on Saturday, rendering it simply as a seating
area. This will allow the SCS to fully replenish its battery bank. The needed amp hours was
calculated to be approximately 630 AhDC/day. Assuming the system will be a 24V system, to
completely charge the battery bank, the maximum power point voltage (Vmpp) would need to be in
the range of 30 to 32V. Noting that the maximum power point voltage of the module is 22.6V and
that the wiring of the modules will be parallel (the voltage of each panel remains the same and the
amperage of each panel is added), a 24V system voltage would be incompatible with the modules;
therefore, the system will be 12V. Essentially, a battery bank of 648 Ah would have been sufficient,
however after further analysis in cost, the SCS will use four, 6V, 390 Ah Crown AGM batteries
(refer to Appendix C). The batteries will be arranged in two strings, each wired in series and
parallel so that the resulting voltage and amp-hour are 12V and 780 Ah. There are added benefits
to having a battery bank larger than what is calculated/needed, such as a large safety factor (~100
Ah) which, in turn, allows for more days of autonomy.
5.5 PV Array Sizing and Charge Controller Selection
The array sizing is determined by taking the daily load calculated above and dividing it by
battery and controller efficiency, sun hours, temperature loss factor, shading coefficient, and derate
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factor. This ensures that the battery bank will recharge in one typical day. The result of this was
685 WDC. The daily load of 685 WDC was divided by the MiaSole power rating of 220W,
yielding a need of 3 modules, with a very negligible deficit in power. The modules will be wired
in parallel so that the voltage of each module remains the same and the amperage of each module
is added. A charge controller was selected that could deliver the needed current and handle the
incoming voltage from the modules. Two charge controllers were considered: the Outback Power
FlexMax 60 and 80. Based on the calculations, a 77 amp max output is needed for the system;
therefore, the Outback Power FlexMax 80 charge controller is chosen (refer to Appendix C for
specification sheet).
5.6 Inverter Sizing and Selection
Powering the outlets, cooling fans, auxiliary cords and other system components requires
converting the DC power output of the batteries to useable AC power. This is done through an
inverter. The inverter is determined primarily by the system voltage (12V) and the largest,
simultaneous power draw. Given the predefined power loads described in Sections 5.2-5.4 and
noting that the derate factor accounts for all the system power losses that isn't equipment related
(i.e. wire lengths, wire connections, panel mismatch, etc.), the largest concurrent power loads
equates to 492 W. The inverter chosen is the Outback FX2012T.
5.7 Wire and Breaker Sizing
Wire and breaker sizing is crucial for delivering proper power to, for and between solar
components. Since the modules will be arranged in parallel, a combiner box with a circuit breaker
for each module is needed to prevent module damage from possible reverse currents. The PV
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arrays grounding conductor will be wired to a ground rod, which will be embedded 8 feet into the
concrete below the stations location. A direct current (DC) disconnect switch will be installed near
the place where the cables from the combiner box enter the housing. The main DC disconnect
switch is followed by a DC ground fault interrupter hat is designed to open the circuit when a
certain leakage current to ground from an ungrounded bus is detected. The current from the PV
array is responsible for charging and recharging the batteries. To protect them from overcharging
or from discharging by reverse currents, normally they are connected to the PV array via a battery
charger. To extract the maximum power out of the array, the PV panels should operate near
maximum power point (VMPP) of their I-V curve, as previously discussed. A DC voltage from the
battery bank is then converted to AC by a DC-AC inverter. Estimating the distances between each
component and box then calculating the ampacity and the voltage drop of the PV array to combiner
box, combiner box to the charge controller, charge controller to the DC disconnect, the DC
disconnect to the battery bank and battery bank to the inverter, the wire sizing for each was
determined, as Table 7 illustrates.
Table 7: Wire Sizing
PV array to combiner box: 10 AWG
Combiner box to charge controller: 6 AWG
Charge controller to Disconnect: 4 AWG
Disconnect box to inverter: 2/0 AWG
Inverter to Battery Bank: 2/0 AWG
The breakers needed for the SCS were determined by first calculating the maximum current of
each wire as it enters and exits each solar component. Once calculated, the breakers are sized and
the results are shown in Table 8.
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Table 8: Breaker Sizing
PV array to combiner box: 30 A
Combiner box to charge controller: 65 A
Charge controller to battery bank: 85 A
Battery bank to inverter: 175 A
5.8 Educational Signage and Monitoring System
The goal of the SCS is to provide a visible campus element that underscores a commitment
to sustainability while teaching students of the technologies associated with solar energy. As such,
an educational signage/display must be implemented into the overall design. Many design options
were considered; however after further research into Outback Power products, it was found that
the MATE3 System Display and Controller (MATE3) provides that ability to monitor and program
each OutBack component (inverter and charge controller). Along with the Outback HUB4, the
MATE3 coordinates system operation, maximizes performance, and prevents multiple products
from conflicting with each other, which could result in power drainage. In addition, it monitors the
overall system, provides feedback and can store data via SD card for system monitoring (refer to
Appendix C). In regards to system monitoring, the MATE3 is compatible with OpticsRE, an
interactive monitoring software provided exclusively for OutBack Power systems. By connecting
the MATE3 to the University’s network, via Ubiquiti AirWire, the information the MATE3
collects is sent wirelessly to a static IP address specific to the station. Once there, the data can be
configured and displayed into various graphs and charts displaying such data as battery state of
charge, energy coming into the modules and how much is being consumed by devices. Users of
the station can then login into OpticsRE with the username and password provides, placed next to
the GFCI/USB outlets as Figure 6 shows, to see the energy use and production and monitor factors
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such as kilowatt hours produced per day (kWh/day), depth of charge in the batteries and much
more. Furthermore, OpticsRE is accessible from any computer, tablet or phone, to allow those who
are curious accessibility at all times of the day, from the comfort of their homes.
Additionally, OpticRE allows the technician to monitor and configure parameters on the inverter,
MATE3 and charge controller, in addition to monitoring the system efficiency and performance.
Figure 6: Login Display Location
5.9 System Integration
With all the solar components chosen, as well as the wire and breaker sizes complete, the
wiring of the entire system and component layout was next to be planned out. As such, the four,
6V batteries will be located under one bench, whereas the remainder of the solar components such
as the inverter, charge controller and DC disconnect box will be located in the center console. The
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exact placement of these components will be elaborated on in Section 5.11. The complete wiring
diagrams, including breaker and wires sizing, can be found in Appendix D.
5.10 Shade Structure and PV Layout
With the use of thin-film PV modules, the need for heavy, bulky mounting equipment used
for traditional, rigid panels is unnecessary. The current seating at the BMU features a red,
collapsible and adjustable umbrella. In keeping with the surrounding design, the shade structure
will be single posted; however it will be pyramidal in shape, as shown in Figure 7 below. The
single post, pyramidal shade structure is a 14’ x 14’, non-collapsible and manufactured by Shade
Structures USA. Shade Structures USA is the largest fabric structure designer and manufacturer
in North America and handle everything from conceptual design to installation. The shade
structure is rated to withstand 115 mph winds, which fulfills the 85 mph wind requirement. It also
has a snow load of about 20 pounds, which is important as the modules will be adhered to the top
of it. Since the shade structures fabric is made of HDPE, the MiaSole modules adhesive will
securely fasten to it; however, as the modules have yet to be installed due to the timing of
permitting, it is unclear at how securely the modules will adhere. If the adhesive does not adhere
as expected, thin pieces of aluminum will be placed on all corners and two-thirds down each side
of the module and the underside of the fabric and riveted together. This creates a frame around the
modules and secures them into place, all while allowing air to flow in between fabric and module
to reduce the oscillation of the shade structures fabric.
As shown in the figure below, grommets have been placed in the fabric to allow the MC4
connectors to be pulled through, secured to the rafters and run down the column through grommets
placed at the top and bottom. In regards to the placement of the modules, keeping in mind that
17
they will be wired in parallel, each module will be placed horizontally on the South, East and West
facing sides in order to receive optimal sunlight throughout the day. Below, Figure 8 illustrates the
concept.
Figure 7: Single Post, Pyramidal Shade Structure
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Figure 8: PV Array Arrangement
5.11 Table and Benches
Initially, various solar charging station manufacturing companies were looked into to
manufacture the table and benches for the SCS, however due to various constraints such as design
implementation and manufacturing capabilities, the decision to simply manufacture the seating in
house was made. As such, the production of the seating was put under the direction of CSU,
Chico’s fabrication shop. The fabrication shop was provided with all necessary computer-aided
design (CAD) drawings, which can be found in Appendix E. As previously states, the benches and
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tabletop will be rectangular in shape in an effort to integrate the SCS with the surrounding tables
and be 25 percent ADA compliant, as Figure 9 illustrates.
Figure 9: Table and Bench Final Design Concept
To construct the benches, which will house the 4 AGM batteries in one bench as illustrated
in Figure 10, A-36 mild steel c-channels was used to create the skeleton and welded together with
one truss in each bench to ensure structural rigidity. To cover the frame, 12 gauge steel sheet metal
was used. The outer side of the benches (long panel facing away from table) are secured with torx
pin-in security machine screws, to allow for accessibility and maintenance of the batteries. The
remaining panels are secured to the frame through rivets and can only be removed with a power
drill. To ensure the batteries have adequate ventilation to maintain proper and safe battery
temperatures, one 115V, AC fan has been mounted (data sheet in Appendix C), in addition to a
natural vent to allow for proper circulation. Both ventilation slots will have mesh in the interior to
deter pests and dust from entering.
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To allow battery wiring to connect to other components and keep these wires safely enclosed and
out of the way a conduit has been placed underground, with the conduit openings located between
the bench and center console. A full dimensional drawing of the trench layout can be found in
Appendix E.
As shown in Figure 9, wood will be fastened to the bench and tabletop for aesthetics and
comfort. In an effort to uphold the sustainable practices shown throughout the campus, the wood
used came from a 400-year-old blue pine, that fell naturally up in Red Bluff. Brandon Grissom,
owner of Enjoy the Store reached out to this project and agreed to do the wood work.
Unfortunately, due to time constraints, the wood was unfinished by Grissom, but was completed
by the team. The work to ensure the completion and weatherproofing of the wood consisted of
sanding, staining, priming and applying resin and epoxy. In addition, a decal was added to the
tabletop, as Figure 11 illustrates. The decal was CNC’d by the Sustainable Manufacturing
department and inlaid within the table.
Figure 10: Battery Storage
21
Figure 11: Tabletop decal
The center median was constructed similar to the benches: using c-channels to form a
skeleton, placing 12-guage sheet metal panels over the frame and placing the blue pin wood on
top. Similar to the benches, the center median contains important solar components such as the
charge controller, DC disconnect box, inverter, etc. Once again, to maintain an optimal functioning
temperature for the components within, two 115V, AC fans are mounted to the sheet metal with
corresponding natural ventilation slots. All fans within the SCS are turned on and off via a
temperature controller. Once the temperature controller reads the interior temperature of the center
console at 90 degrees Fahrenheit, the three fans turn on and continue to run until the interior
temperature drops below 80 degrees Fahrenheit. In order to access the components within to
perform routine system maintenance and/or perform checks, the components are mounted to a
separate sheet of sheet metal and placed on a rail system to allow the technician to simply unlock
the side panels and easily monitor all components. The layout of all components is illustrated in
Figure 12.
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Figure 12: Center Console Component Layout
As stated earlier, a customer requirement is that the SCS has 120V GFCI and USB
receptacles. As Figure 13 shows, the GFCI and USB receptacles are placed in the middle of the
table with a dual outlet containing both the GFCI and USB plug-ins; there is a total of 8 GFCI
outlets and 4 USB outlets. All electrical wiring is encased and out of the way with all the outlets
protected from the elements by adding a weatherproof flip lid cover to each. In addition to the
GFCI and USB outlets, the station provides its users with two, 4-in-1 charging auxiliary cords for
all smartphone devices. The auxiliary cords will be available for the following phones and there
will be a total of 8 cords (2 for each category):
iPhone 4/4S
iPhone 5/5S/5C/6/6S
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Android
In an effort to deter the cords from being damaged or tampered with, the length of the cords will
be kept at 0.0381 meters (1.5 inches). In case of vandalism or damage to the cords, the vendor list
and price of all components can be found in Appendix G.
Figure 13: GFCI/USB Outlets and Auxiliary Cords
Another customer requirement dictates that the SCS have security features such as lighting,
emergency shut off switch and hours of operation. As Figure 14 shows, the location of the solar
charging station is adequately lit; however additional lighting is intended to deter vandals and
transients from approaching the SCS in the evening hours. This is achieved by the addition of
LED, motion detection lights that is set to turn on when someone approaches (within 15 feet) the
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station and stays on for a burst of 45 seconds. Another security measure will be to turn off all
power to the GFCI/USB receptacles, as well as the auxiliary cords, during hours of non-use. As
such, the SCS will be in operation from the hours of 8am to 8pm, Monday through Friday and
Sunday. This is achieved through a timer which is preset to “power on/off” the outlets and auxiliary
cords based on the parameters and times set.
5.12 Testing Results and Interpretation
As described in Section 1 and illustrated in Table 1, the SCS has a set of Must Do
Quantitative requirements that need to be tested in order to ensure that all customer requirements
are met and that the station works as designed (refer to Appendix F for full test plan and data
sheets). The tests conducted were as follows:
Figure 14: Evening Lighting at Location
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1. Maximum Footprint
a. Cannot exceed 8 x 8 feet
2. Storage Capacity/Days of Autonomy
a. Must sustain 2.78 kWh for 2 days without discharging the battery bank
more than 50%.
3. Maximum Power Specification
a. Inverter must sustain up to 0.685 kW/day to allow 6 people to charge
various devices.
4. Monitoring System and Mate3 Reconfiguration
a. Accurately monitor and collect data from the MATE3 and display said
data to OpticsRE, while allowing it to be user-friendly.
5. Safety Features
a. Ensure that the inverter shuts down once the battery state of charge
(SOC) reaches 50% to maximize the lifespan of the battery bank.
b. GFCI/USB receptacles will shut down after 8pm and turn back on at
8am.
The first quantitative test was the total footprint and straightforward to test. The maximum
footprint of the station cannot exceed 8 x 8 feet; the SCS total footprint is measured at 8 x 6 feet,
meeting and passing the requirement.
For the storage capacity and days of autonomy test, the station was designed to sustain a
2.78 kWh load for two days without depleting the batteries more than 50% in days of overcast and
little sun. The battery bank of the SCS is responsible for sufficiently storing solar energy collected
and allowing users to charge their electronic devices. Considering the battery bank is 780 Ah,
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about 100 Ah more than what is required, it was highly likely that the station would pass this test.
After sustaining an 800W load for three and a half hours, the state of charge (SOC) was 63%,
meeting and passing the requirement, as Figure 15 illustrates.
Figure 15: State of Charge Test
Powering the outlets, cooling fans, auxiliary cords and other system components requires
converting the DC power output of the batteries to useable AC power and is achieved through the
inverter. For the maximum power specification test, the inverter must sustain up to 0.685 kW to
allow 6 people to charge various devices. After the battery bank reached 100% SOC, the inverter
was loaded with an 800W load and monitored for an hour and half to ensure the inverter did not
shut down due to an overload. As expected, the inverter was able to sustain an 800W load for an
hour and a half, meeting and passing the third requirement.
The objective of the Monitoring System and MATE3 Reconfiguration test is to verify that
the collected data from the MATE3 is monitoring and accessible on the OpticsRE website. The
test process did not involve any measurements as it is assumed that the purchased components will
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function as specified in the vendor document. Once the initial log-in and configuration of the
MATE3 connectivity to a known network and OpticsRE was established, the display of features
such as battery SOC, inverter consumption, load consumption, etc. needed to be verified. By
powering the station and applying various loads via plugging in phones/laptops/tablets, real-time
data was monitored via OpticsRE. After setting up a guest account that users will be able to log
into, it was determined that the MATE3 and OpticsRE were communicating properly and
displaying real-time data, meeting and passing this requirement. Note that with the guest account,
users can only view data coming in and cannot change or view parameters set on the MATE3,
inverter and charge controller; only the administrator can do so (refer to Appendix H for login
information). In addition, it is necessary to check every 2 months with Outback Power Systems
via website for firmware updates for the MATE3 to ensure proper connectivity with OpticsRE.
Per customer requirement, the SCS will have security features such as lighting, emergency
shut off switches and hours of operation. One security feature is ensuring the inverter shuts down
once the battery state of charge (SOC) reaches 50% to maximize the lifespan of the battery bank.
If a battery is discharged more than 50% and not fully charged, the cycle life drops significantly
and permanent and irreversible damage could occur to the battery bank. As Table 9, on the
following page illustrates, the SOC of a 12V system should not fall under 12.1 Voc. Once the “cut
in/out voltage” parameters were set on the MATE3, an 800W load was once again placed on the
system.
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Table 9: Battery State of Charge
As expected, the inverter shut down all power to the receptacles and auxiliary cords once 12.1V
was reached. The charge controller then went into the bulk stage, in which all energy coming from
the modules are used to recharge the batteries. Once an open circuit voltage of 12.62V was reached
(90%), the inverter turned back on and provided power to the receptacles and auxiliary cords once
again. It is important to note that the batteries should never be discharged more than 50%, as this
can permanently cause damage to the battery bank. Once one battery is damaged, the entire bank
will need to be replaced. The SOC can be monitored at all times via OpticsRE. Technicians should
check it frequently; at least once a day.
In addition to the inverter shutdown, the SCS will utilize a system timer that will turn the
receptacles and auxiliary cords on and off at 8am and 8pm. This is in an effort to deter late night
use by transients and allow sufficient power storage for the following day. The timer used in this
application was the Outdoor Digital 2-Outlet timer. This timer features to-the-minute digital
settings and a countdown function. Once the timer was set with specific dates and times of
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operation and shut down, electronic devices were plugged into the receptacles and auxiliary cords
to determine if no power was coming to them. Upon seeing that the charging indicator not turn on
for the electronic devices, then come on at the defined time, the test was determined to be a success.
Note that the timer has a setting for daylight savings time and a technician can use the manual
override button to turn the timer off and outlet on. Even if the inverter does not supply the outlet
that the timer is plugged into with power, this timer retains its settings with a self-charging battery
backup. Once again, the full testing procedure documentation, as well as test data can be found in
Appendix F.
Planning
Project planning is an important aspect to the success of any project. The main milestones
for the SCS for the Fall semester included components of overall design: load calculations, concept
designs, working drawings and ordering all components before the semester concludes. The Spring
semester, on the other hand, focused on implementation. Among other things, the spring semester
included acquiring additional funds to complete the project, creating a test procedure for the
quantitative requirements, coordinating with Facilities Management Services regarding
installation of the shade structure, participating in the Sustainability Conference XI, as well as
acquiring proper permitting from the University. Testing procedures and the total Engineering
Hours for the Fall semester is estimated at 191 hours, whereas the Spring semester is estimated at
206 hours (subject to change). The start and finish dates reflect those on the detailed schedule in
Appendix I.
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Budget
In 2006, students voted to increase their fees by $5 each semester to support the creation
of the AS Sustainability Program and Fund. The majority of this money goes into the AS
Sustainability Fund which makes available approximately $60,000 annually for student-driven
projects. The SCS has received funding from SFAC in the amount of $12,000, as well as an
additional contribution of $3,325 from the College of Engineering, Construction Management and
Computer Science. The budget for the SCS was broken down into six sections:
1. Solar Modules
MiaSole FLEX-01, 220W Modules
2. Power
OutBack Power solar components
Battery Bank
Disconnects/Breakers
3. Electrical Accessories
Duplex, GFCI/USB outlets and auxiliary cords
Security Lighting
Fans
Timer
4. Seating and Shade Structure
Steel: C-Channel and Sheet Metal
Blue Pine Wood
Shade Structure
Powder Coating
Rivets and Security Machine Screws
5. Wiring
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6. Miscellaneous
Shipping and tax
Electrical Inspection
PE/EE Stamp of Approval
Figure 15 shows the budget breakdown of the project. As shown, the biggest contributor
of the budget goes to power, which includes items such as the charge controller, inverter, MATE3
and the battery bank. The second would be the seating and shade structure. The main reason for
this is that the shade structure itself cost $3763 and is the most expensive item on the budget. All
the remaining sections (solar panels, wiring, miscellaneous, etc.) play a small role in the overall
budget, none reaching 10 percent of the budget.
Figure 16: Budget Breakdown
8%
41%
4%
43%
2%
2% Current Budget Breakdown
PV Panel
Power
Electrical Components
Seating and ShadeStructureWiring
Miscellaneous
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Table 10, below, shows the amount for each of the six sections. The solar power component
section amounts to $5,465.75; taking up over 40% of the budget. On the other hand, the seating
and shade structure amounts to $5,900.26, the largest portion of the budget at 44%. The remainder
of the sections amounts to $2,160.27, bringing the grand total of the solar charging station to
$13,556.28. This leaves the SCS with $1,799.72 remaining in the budget. What has not been
accounted for in the budget is the work done by Facilities, Management & Services which includes
management, design, labor and materials of the installation of the shade structure. This cost has
been offset by Lori Hoffman, the Vice President of Business and Finance. Furthermore, the cost
of a Professional Electrical Engineering stamp of approval on the solar calculations has yet to be
accounted for in the budget, but has been included in the budget. A full budget analysis can be
found in Appendix G.
Table 10: Section Budget Breakdown
Section Cost
PV Panels $1,142.98
Solar Power Components $5465.75
Electrical Components $555.27
Seating and Shade Structure $5,900,26
Wiring $242.34
Miscellaneous $219.68
Total $13,526.28
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Justification
CSU, Chico is one of only 21 schools on the Princeton Review’s Green Honor Roll for
campus sustainability and has long been a sustainability trailblazer. President Paul J. Zingg was a
founding signatory of the American College and University Presidents’ Climate Commitment. The
Institute for Sustainable Development helps guide CSU, Chico's strong commitment to balancing
human, social, cultural, and economic needs with the natural environment. As such, in partnership
with SFAC, this solar charging station adds a visual element of campus sustainability, while
teaching students of the technologies associated with solar energy. In addition, it will be the first
of its kind to be implemented on the CSU, Chico campus and the first to allow students to monitor
factors such as kilowatt hours produced per day (kWh/day), depth of charge in the batteries and
much more. As the previous sections demonstrate, the SCS will successfully charge laptops, smart
devices and tablets throughout the day, all while capturing the SCS progress in real-time and
displaying it for all the students to monitor. With all of seating and installation of the shade
structure and fabric complete, as well as the component layout, the installation of the SCS on site
will occur by graduation weekend. However, it has been discussed that if the station cannot be
fully installed, pending the arrival of permitting from the University, the stations installation will
be completed before the beginning of the Fall 2016 semester.
Discussion
In summation, all calculations have been checked and approved and all of the customers
Must-Do, quantitative requirements have been tested and met. This station will be able to
accommodate any laptop, smart device and tablet plugged into it. The overall SCS system is the
first of its kind on the Chico State campus and first of its kind in the nation to utilize thin-film
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photovoltaic modules and a allow not only technicians, but its users to monitor the stations
progress. With the added ability for all users to monitor the stations progress at any time, from the
comfort of their handheld devices or laptops, it is the hope that users learn more about the
technologies associated with solar energy and hopefully foster sustainable practices and living.
The SCS not only met all of the specifications set forth by the customer, but also took steps
in ensuring its longevity and safety by securing funding for any maintenance that is required in the
years to come. Safety precautions have been put in place to decrease the level of vandalism;
however, it is understood that vandalism and possible harm to the station is inevitable. The College
of Engineering, Construction Management and Computer Science, in partnership with Associated
Students and Engineers for Alternative Energy, will ensure that the station is maintained and
remains a lasting entity to this campus’ goal of sustainability.
Recommendations
It is the recommendation of this group that more solar charging stations be implemented
throughout this campus. With a detailed design report that includes calculations, vendors and all
steps necessary at implementing more, it is achievable. However, this group does advise that all
parties and departments involved in the installation and implementation of the station meet to
discuss what is expected and jobs performed by each. Furthermore, it is recommended that
contracts be drafted to ensure that what each department agrees upon doing, is actually completed
in a timely manner. First and foremost, all permits should be acquired before components are
purchased. Once all proper permits are acquired, the implementation can begin.
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It is this teams hope to see more solar charging stations implemented on this campus, so
that generations upon generations of future Wildcats can enjoy the wonderful Chico weather, while
charging their personal electronic devices in a sustainable way.
References