5.3. ECCSR 02-15-2017Subject: FW: questions about solar powered picnic table status
From: Dahmus, Maria E. [mailto:medahmus(�)stthomas.eduj
Sent: Monday, February 06, 2017 10:31 AM
To: Sevcik, Tim
Cc: Fernandez, Alexander U.
Subject: questions about solar powered picnic table status
Hi Tim,
Thank you again for taking the lead on the engineering senior design project at the University of St. Thomas!
left a message, but I thought I'd email as well.) I wanted to touch base with you on a few questions about the
project to be sure it's all proceeding as planned.
1) Regarding the construction of the table: Kristin mentioned that the streets department was planning to
construct the table, benches, and roof. Will the streets department be doing the construction rather than a
general contractor? Could the team talk with the streets department (or general contractor) to be sure what
they're designing works with what the City plans to construct and also to be sure the team stays on schedule
for their components of the project? Is there a contact person you could connect them with for that?
2) Regarding the budget for the project: Kristin mentioned that there is $2000 available for the project from
the 2017 Energy City account. (Is this still correct?) Should the engineering department send you (or
someone else at the city) an invoice for that portion of the project so the team can continue to purchase
components to build table? (Kristin handled this part for the first payment, so I'm not sure what the process is
or the exact status of the budget from the city's end.)
I'm also cc'ing the student project lead, Alex Fernandez, to this email so we're all up-to-date on the
questions/status.
Thank you again for working with the Senior Design Clinic and the Sustainable Communities Partnership on
this project!
Maria
Maria Dahmus, Ph.D.
Assistant Director, Office of Sustainability Initiatives
University of St. Thomas
St. Paul, MN 55105
Phone: 651-962-6391
medahmus@stthomas.edu
www.stthomas.edu/osi
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Sponsored by: The City of Elk River
Sponsor contact: Kristin Mroz, City of Elk River
Team 6 Advisor: Dr. Greg Mowry, UST
Project Recognition: Maria Dahmus (SCP)
Invited Guests: Dr. John Wentz (UST), Dr. Sarah Baxter (UST), John Angeli (UST),
Steve Albers (UST), Brian Plourde (UST), Paul David (UST), Tim
Sevcik (Parks Dept.- City of Elk River) via Skype
Team 6 Senior Design Project
Members: Alex Fernandez, Charlie Gerten, Josh Gutzmann,
Mike LeMay, Frank Pitera, Nicole Muske
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Customer Requirements Review
The project should be an educational hub for the community on solar energy and also
highlight the city's green energy focus via an educational display.
The project should be capable of powering standard portable electronics, retain
functions of providing shade and a picnic area in an open park, and be a standalone
unit independent of the city's grid.
The project should be durable and weatherproof.
The energy system should be capable of delivering at least 30OW for 8 hours during a
sunny summer day.
The energy system shall have a master control for power shut-off in case of
emergencies and maintenance and be protected against faults, theft, abuse, or
accidents.
The system will have timed LED lights for illumination and patron reading.
Location Profile
Orono Park is an approximately 34 acre park located on the west shore of Lake
Orono in the city of Elk River that is heavily frequented by residents
throughout the year. Local events are sometimes held there and draw crowds
of over 600 at a time.
Approximately 500 residents visit the park weekly with park demographics
ranging from families with kids, young adults, and teenagers to retirees.
Weekends see a significant increase in park patrons.
The park includes a boat launch, dog park, green playground, skateboard park
as well as several powered pavilions that are available for use only upon prior
request.
Orono Park serves as a hub for the city hall campus, the YMCA, the city library,]_
Sherbourne county fairgrounds and local residents looking to relax from nearby arksandre
sporting events like softball.
Profile cont'd
Orono Park sees an average of 11 hours of sunlight with sunrise at approximately
7:27 AM and sunset at approximately 6:36 PM**.
The park has a clean line of sight facing south with no obstructions and a listed
altitude of 912 feet above sea level. Per research (including information from local
solar installers), a solar panel would need an angle of 12-20 degrees to the normal
in order to capture maximum sunlight directed towards the park.
• Weather in Elk River is slightly more sunny than other parts of the metro and
recent temperature ranges have been between -25 to 50 degrees Fahrenheit
(2009). The lowest recorded temperature was -40 degrees Celsius in 1943 and the
highest was 55 degrees Celsius in 1944.
• Snowfall is very tow fort e city with 7.5" being the highest 24 hour dump in recent
weather reports (as of 2007)**.
Project Design Considerations
The physical structure shall be designed to incorporate the Elk River city logo in
addition to the "Powered by Nature" logo.
The energy storage and electronics compartment housing the batteries and
inverter shall be located on a raised platform under the table to allow for
drainage and easy access by park maintenance staff.
• The table shall be separate from the bench to allow for legroom, Americans
with Disability Act compliance and easy access by park maintenance staff.
Review of Design Choices
The project started with 5 different designs done by our team
Graphics Artist.
For a quick reminder they are represented in the following
sketches...
TnBu DESIGN #1
SHIFT ID HOF PERK STORAGE
Fr SIDE ROOF SUPPORTS IMIDE OF TABLE
L1UTH SIDE
01, ;—]
L—
NORTg SIRE
OF TRBLE
ST(RRCI INSIDE Of
POUF UK
TnBLE Dula 4?
ROOF WITH SYMETRIC PERK
ANU CENTER MMU
9m SIDE
DF ME
:C,llll�!vinvmw-
Wig sin
OF TABLE
BATTERY STARGE
INSIDE OF TABLE
TV
ROOF PEN
TABLE Dun #3
FLOWER-LIKE ROOF DESIGN
& HILKIRGONAE TABLE
TABLE DESIGN 44
ROOF WITH TREE-11KE CANOPY
� BRANCHING SUPPORTS
TABLE DESIGN #5
Fuii ROOF KOK
F sluf Suppom
MICN DETAILS
ROOF SUPPORTS A
THU LEG 14LRY
RR N DRIP
ER GE
VENTING FOR
HE HT
�JGITRL
DJSPEf1Y
SIDE VIIN OF ROOF
& ROOF SUPPORTS
SIDE VIEW OF TABLE LEC
TAKE DESIGN 45
Poll ROOF Kor
6 910E SUPPORTS
PQM'EA1 d A9
NATUREI
3D Rendering of the Solar Table
Structure with closed access
panel
Structure with open access
panel
Project Direction
In order to determine the proper components for the Electrical System, a load
profile analysis was conducted to determine the estimated usage for the
project in the park.
Using that information, a source profile analysis was also conducted to ensure
that power generation exceeded the load.
► A power budget was then created from that data to determine the
components for the entire electrical system.
! The following slides address the source and load profile analysis.
Load Profile
Survey was taken to help determine use
► Source profile created using NREL's PV -Watts tool
► Load and Source profiles compared for overlap
Load Profile
The following loads were assumed on a per
month basis
Load estimates were made based on average
electronic devices
Load and Source profiles compared for
overlap
Projected Load and Generation for July 4th
Watts
—\'REL Projected Generated Power —Projected Load
900
800
700
600
500
400
300
200
100
0
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Time of Day (24 Hr Time)
P0NER6iil 1*48
,�T
600
450
400
350
I J.
a
m
3
zm 250
8
d
200
150
100
50
0
Power and SOC from 3, 248 watt pannels 1113 to 1118
I I I I I
soc aa.mlrs
-Panel mat
—wars ro luatl
L wd PY048
hi � -\
0 20 40 60 60 100 130
hours
P6wEITURE
nE a A9
N"
600
500
400
A
m
3
v 300
IL
IL
200
100
Power and SOC from 3, 248 watt panne Is 7113 to 7118
soc arrq„s�s
-Panes anptt
watts to load
-Load Profile
---------- ----------- ------------ ---------- ----
VO 20 40 60 80 100 920
hours
P/IE0EI I
NATURE
Electrical System
The Electrical System was decomposed into four main subsystems:
The Energy Generation system
Solar Panels
The Energy Storage System
Battery
Charge Controller
► The Distribution System
Inverter
Outlets
.1 rfTaNm
Solar Panels (3)
Connected in 750 Watts
Parallel
35V
21A
Breaker
60A Charge
Controller
Quad USB Outlet
(99% efficient)
88% efficient
14V
300W Inverter
120V Receptacles
Data Logging 53A
(92% efficient}
(2)
120V
Disconnect
Switch
60Hz AC
300W Inverter
120V Receptacles
(92% efficient)
(2)
Breaker Hail
EAect
LED Light(s)
2 Batteries in Parallel Sensors
12V DC
(1-2W)
12V Nominal11
INATUR:�]
Power Electronics
Design Choice
The solar panels generate DC only- the goal is to send generated solar voltage to an
energy storage unit
With the design choice of a battery, charging needs to be regulated efficiently
► This leads to charge controller (2 types used today, PWM, MPPT)
► Outputs are AC and DC separately
11
We could have an AC and DC bus, but it's very easy to get AC output with an inverter.
From there, we can use receptacles that have built-in AC and DC output with just a AC
input.
Energy Generation System
This sub -system includes the following components:
Solar Panels
Mounts and Rails
POWER CLASS
MINIMUM PERFORMANCE AT STANDARD TEST CONDITIONS, STC' (POWER TOLERANCE -SW /-0W)
Power at MPPw
P_
[W]
Short Circuit Current'
hp
[A]
— Open Circuit Voltage'
V.
[V]
Current at MPP'
Iwe
[A1
8.91
8.97
9.03
Voltage at MPF'
V„'
[VI
Efficiency'
q
[%]
MINIMUM PERFORMANCE AT NORMAL OPERATING CONDITIONS, NOG
330
335
340
330
335
340
9.49
9.54
9.59
46.55
46.81
47.07
8.91
8.97
9.03
37.02
37.33
37.63
216.5
2 16.8
217.1
Power at MPP'
P_ [W]
244.7
248.4
252.1
E Short Circuit Current'
Iu [A]
7.65
7,69
7.73
e Open Circuit Voltage•
V. [V]
43.44
43.68
43.92
Current at MPP'
Ir, [A]
6.99
7.04
7.09
Voltage at MPP'
V_ [V]
35.01
35.29
35.56
11OQ0 Wim-, 25C, s, --m AIA I 5
Measurement tolerances SIC -3%; NOC i5%
180n W!m', NOU. spectrum AM 1.5G
'typical values, aclual values may ditfer
__4
PBWEAEm BY
INATUREJ
Energy Storage
The purpose of the energy storage unit in our system is to store
energy produced by the panels when the user is not using that energy
771
• Energy storage devices explored
• Lead Acid Batteries
12V 100AM DEEP CYCLE
0 Lithium Ion Batteries
LITHIUM ION BATTERY
SMART'
BATTERY
• Super Capacitors��
Energy Storage Cont.
Option 1: Lithium Ion Batteries
Used in mobile applications, light weight with a
charging efficiency greater than 95%
► 3% or less self discharge per month
► Does not lose capacity as discharge current increases
► Can not handle low temperatures
► Cost to outfit our system: $2600
12V 100AH DEEP CYCLE
LITHIUM ION BATTERY
4& SMART'
BATTERY
pww.sr�yR�arrtr•cow
,asdoaurww
Energy Storage Cont.
Option 2: Lead Acid Batteries
Used in auto and marine applications, a heavier battery
with a charging efficiency between 80-85%
o
► 1-10/ self discharge per month
► Loses total energy capacity as discharge current
increases
MMMWAM1 BOMY
► Can operate in wide range of temperatures
► Cost to outfit our system: $616
Very small leakage current
► Great for short term high current applications,
but does not store a high amount of energy
► Can operate in a wide range of temperatures
► Not feasible for our high energy storage
scenario
Energy Storage Condu
By comparing the efficiency, cost,
and temperature ranges of the three
different storage options, lead acid
batteries are the best for our
application.
We decided to go forward with the
Concord Sun Xtender Absorbed Glass
Mat battery. The low internal
impediance and the fact that it is
completely sealed to prevent spills
and leaks make this the optimal
battery.
Sion
RENEWABLE ENERGY
AGM
Distribution System
This sub -system includes the following components:
Inverter
GFCI outlets and USB outlets
Inverter Selection
Pure sine wave vs Modified sine wave
Some electronics won't function with modified sine wave
Inverter/ Charger vs Inverter
Inverter/ charger allows the charging of a battery from
another source if the batteries get low. This was not selected
because it is primarily used in a generator or grid -tie system.
Specs
Power rating, temperature rating, protection types and
recovery, output configuration, etc. L'
pr"o
z �-
� IJ
Charge Controller Selection
► TriStar MPPT60 from Morningstar
► Temperature rated to fit requirements
► Power rating covers our array max output
► Comparable price to other charge controllers
► TrakStar MPPT
Outlet Selection
► Leviton 20A GFCI WR TR AC outlets
► Legrand Quad USB outlet, built in transformer
► Respective "in -use" covers
Owego
I ..A
Mi _'M
Educational and Sensor System
This sub -system includes the following components:
Data Logging
LED and Timer
► Educational Plaque
Educational Plaque
The plaque shall reflect the city of Elk River's focus on green energy along
with information on solar charging and use.
There will also be information showing the cooperation between the city and
the University of St. Thomas.
► The decision was made to have the plaque showcase the city's colors of blue,
green and brown.
► More information and action on this to be determined.
Solar and Load Data Logging
► The solar generation and load data logging can be
performed with Wattmon data acquisition box
(DAQ) and a dual Hall effect sensor device
► The Hall effect sensor measures the DC current and
relays the info to the acquisition device for logging
► The DAQ has a few different data retrieval methods
SD card
e Direct computer connection via LAN
Data Acquisition
Viewing the data over the Internet via the park WiFi r — -
► The Wattmon DAQ offers flexibility for viewing the
load and solar data
DC Hall Effect Sensor
19 FMARrers 0 ff Mrs 0 PRI Fag re
Home Graphs Energy In and Out in Watts Graph
Energy In and Out in Watts Graph on 07/0712013
...........
07 10712013 a Day View Month View
MIT"Mm"Irl"T "M
,Soo
-= SOW charge
Load Watts �
,000
Grid Charge Watts
500 .
0
-1000'
1500
•2000
00.00
0200 0400 0600 0800 10.00 1280 1x.00 lea 1890 20.100
paNERI
A Wji BT
Physical Structure
Using research of industry standards, various materials were considered in order to build the structure
and provide support for the energy generation system. Research details can be referenced in the
design discussion and appendix. The materials were narrowed down to the following:
Wood
Plastic Lumber
Concrete
Coated Steel (Thermoplastic or plastisol coated)
Aluminum
*N/B: The table comparison showing the major attractors and detractors between considered
materials is also included in the attached technical slide.
Material Choice
After research, the decision was made to
use engineered Cedartone pressure treated
lumber for the table, bench and roof
supports.
This is a type of hardwood that has proven
very reliable for a large number of builders
of similar park structures".
Being treated, it does not rot or decay easily
outdoors, is resistant to water damage due
to repellent applied on surface, has
exceptional durability and is easy to work
with.
Wood is a natural material and would fit
more in line with the 'Powered by Nature'
theme.
Benches
Both benches shall be dimensioned to National Park Services standards of 9.5"
wide, 24-30" high and length sufficient to seat 8 adults.
The decision was made to go with a more contemporary design reflecting
aesthetics and simple functionality.
Benches shall be placed on either side of the table for easy access to the
table and allow easy access per Americans with Disabilities Act standards.
See through Middle
The table design includes a 12 x 96 x 0.25 inch high
impact resistant polycarbonate in the middle.
This allows park visitors to see the guts of the table in _
operation and also satisfies the educational aspect of
the project.
The polycarbonate weighs approximately 47 lbs and has I
compressive strength of 12500 psi, UV resistance, is
flame inhibiting and has strong chemical resistance.
Aesthetics and Lobo
Every effort was made to incorporate the Elk River logo and Powered by
Nature logo on the project.
The base pedestal for the table was designed to include the "Powered by
Nature" logo on the door of the maintenance access as shown in the 3D
modeling.
The Elk River logo will be placed on the side of the benches using a
carving or adhesive.
► Gable style roof
► Classic rib steel roof panels
► Shiplap sheathing
n�.
Roof
Mount Selection
► Quickmount Classic Shake Mount IronRidge XR rails
flashing
Anchor and Footing
► 3' Steel sleeve with plate and J -bolt
► 4" Slab
► 4" Compact fill
► 5-6' reinforced concrete footing
Moving Forward
Create testing method for components
Work with Contractor on dates and design
► Test individual parts and assembled structure
Finalize the project details in PDR
12/07/16
12/07/16
Finalize the ordering of parts
12/08/16
02/01/17
Finalize the project details in CDR
02/01/17
03/10/17
Begin construction of the table assembly
02/16/17
03/19/17
Begin testing electrical components
02/01/17
02/12/17
Begin testing data logger, LED Et timer
02/01/17
02/12/17
Begin testing protection methods
02/12/17
02/26/07
Begin testing full electric systems
02/26/17
03/19/17
Begin construction of the roof assembly
02/16/17
03/19/17
Begin concrete pour
03/01/17
03/15/17
Full installation and delivery of system
03/16/17
03/30/17
NATURE
Post Design Cost
Electrical Components: $3,007
Physical Structure Materials: $2,794
► Total: $6201
► This cost does not factor in construction or the cost of pouring concrete