table of figures and tables - automated computational ... · web viewpouring a cement pond,...

Aquaponics Choluteca 2012Honduras Service Learning Project; ENG 692; March 2012

Team Members: Killian Llewellyn, Lisa Reisenauer, Nial Tilson, Tom ZajdelAdvisors: Roger Dzwonczyk and Miriam Simon

Table of ContentsTable of Figures...........................................................................................................................................5

Introduction.................................................................................................................................................6

Background.............................................................................................................................................6

Participants..............................................................................................................................................7

Project Details.............................................................................................................................................7

Problem Definition..................................................................................................................................7

Vocational School Expansion..............................................................................................................7

Clinic Power Supply............................................................................................................................7

Water Testing......................................................................................................................................8

Scope of Work.........................................................................................................................................8



Water Testing......................................................................................................................................8

Deliverables.............................................................................................................................................9



Water Testing......................................................................................................................................9

Solution Details.......................................................................................................................................9


Aquaponics Solar Power Supply.......................................................................................................12

Water Testing....................................................................................................................................17

Sustainability and Maintainability.........................................................................................................19

Vocational School Expansion............................................................................................................19


Water Testing....................................................................................................................................19

Project Schedule........................................................................................................................................20

Pre-Trip Preparations.............................................................................................................................20

General..............................................................................................................................................20

Vocational School Expansion............................................................................................................20

2


Water Testing....................................................................................................................................20

Implementation and Results......................................................................................................................21

Vocational School Expansion................................................................................................................21

Aquaponics Solar Power Supply...........................................................................................................22

Pump Analysis...................................................................................................................................22

Panel Mounting.................................................................................................................................23

Wiring................................................................................................................................................25

Solar Power System Results..............................................................................................................30

Water Testing........................................................................................................................................31

Schedule and Budget.............................................................................................................................33

Future Recommendations..........................................................................................................................33

Vocational School Expansion................................................................................................................33

Aquaponics Solar Power Supply...........................................................................................................34

Water Testing........................................................................................................................................34

Conclusion.................................................................................................................................................34

Appendices................................................................................................................................................36

Appendix A: Electrical Datasheets........................................................................................................36

Appendix B: Electrical Assessment of Aquaponics System..................................................................37

Calculations...........................................................................................................................................38

Auxiliary Figures and Tables.................................................................................................................38

Documents.............................................................................................................................................39

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Table of Figures and TablesFigure 1: Solar power system schematic....................................................................................................11Figure 2: Solar power capacity and requirements.....................................................................................12Figure 3: Battery bank capacity versus duty cycle.....................................................................................13Figure 4: Panels required to charge battery versus duty cycle...................................................................14Table 1: Materials and costs for solar system............................................................................................15Figure 5: The nitrogen cycle in aquaponics systems..................................................................................16Table 2: Safe level ranges for key chemicals and indicators......................................................................17Table 3: Costs for water testing supplies (no shipping or taxes)................................................................18Figure 6: Aquaponics system at the vocational school after the expansion of the lower plant bed............21Figure 7: Solar panel installation site.........................................................................................................22Figure 8: Birds-eye view sketch of solar cell support frame......................................................................23Figure 9: Finished solar cell array.............................................................................................................24Figure 10: Wire run from solar panels to breaker......................................................................................25Figure 11: Wiring through the junction box..............................................................................................25Figure 12: Transfer switch wiring and schematic......................................................................................26Figure 13: (a) Aquaponics system breaker wiring and (b) physical transfer switch...................................27Figure 14: Solar power system electronics wiring.....................................................................................28Figure 15: Solar panel terminal wiring......................................................................................................29Figure 16: Solar panel wiring sketch.........................................................................................................29Figure 17: Layout of the ponds and plant boxes at the clinic.....................................................................31Table 4: Water Testing Data for the School and Clinic.............................................................................31

4

Introduction

Background

Beginning in 2010, ECOS, Dr. John Merrill, and the Office of International Affairs have

pursued an interest in coordinating and implementing humanitarian engineering projects in

Choluteca, Honduras. A team was sent in 2010 to research and assess the area. The following

year, a team of eight students led by Dr. Dzwoncyzk implemented the first project working with

Larry and Angie Overholt, associated with World Gospel Mission.

This project included the design and provision of an aquaponics system in Choluteca. An

aquaponics system is a self-sustaining system in which a fish tank provides nutrients to growing

plants, which in turn, clean the water for the fish. An aquaponics system requires food for the

fish and energy to power a pump to move water from the fish tank to the plants. This is often

achieved by solar power in order to provide a self-sustained system. The system is capable of

producing fruits and vegetables as well as fish for consumption or sale. Aquaponics systems can

range from small personal systems to immense commercial systems.

The 2011 Choluteca team successfully constructed an aquaponics system at a vocational

school run by Larry Overholt. This year, another eight students will return to improve on the

aquaponics system created in 2011 and change the power source for another, larger aquaponics

system.

5

Participants

Participant Primary Responsibility

Killian Llewellyn Total System Equilibrium

Lisa Reisenauer Water Quality Testing

NialTilson Container Expansion

Tom Zajdel Electrical Components

Miriam Simon Team Advisor

Dr. Roger Dzwonczyk Team Advisor

Project Details

Problem Definition

Vocational School Expansion

A vocational school in Choluteca, Honduras teaches Honduran students various

vocational skills and introduces them to potential business opportunities. Approximately one

year ago, an aquaponics system was installed at the school to help teach the students how fish

and agricultural plants could be grown and harvested simultaneously and profitably. Currently,

the fish tank of the school’s aquaponics system is not supporting tilapia so that they can to serve

as food or to be sold. It has been requested that we investigate expanding the size of the fish tank

so that the fish can grow to the proper size for sale or consumption.

Clinic Power Supply

In addition to this system, there is another, larger aquaponics system at the Overholts’

clinic. However, as a result of its size, it consumes large amounts of electricity in order to

6

circulate the water from the lower fish tank to the upper botanic level. The Overholts have

requested that their currently owned solar panels be incorporated into the system so that they can

become the tank’s sole source of power. Furthermore, it was requested that we provide the

option of freely switching the system between grid power and solar power.

Water Testing

Currently there is no water testing being done on either of the aquaponics systems. The

Overholts have requested that we establish a system of periodic testing of the chemical quality of

the aquaponics systems at both the Overholt’s clinic and the vocational school.

Scope of Work


The goal of this project is to expand the fish tank for the aquaponics system at the

vocational school. This project will allow for further education and exploration at the vocational

school in the area of aquaponic agriculture.

Clinic Power Supply

The goal of this project is to power the Overholts’ aquaponics system with solar panels

and provide the system the ability to switch from solar power or grid power for the pump. In the

event that there is surplus power available from the solar panels, the energy can be used to

supply power to an outlet for miscellaneous uses.

Water Testing

The goal of this project is to establish a system of periodic testing of the chemical quality

of the aquaponics systems in order to determine the overall health of both the systems at the

Overholt’s clinic and the vocational school.

7

Deliverables

Vocational School ExpansionThe project of expanding the aquaponics system at the vocational school will deliver a

functional, appropriately sized fish tank for the vocational school’s aquaponics system that will

support fish that are large enough to be sold or consumed. Documentation of the project will be

delivered as well.

Clinic Power Supply

The project of providing power to the Overholts’ aquaponics system will deliver

installed solar panels to power the pump in the aquaponics systemand the ability to switch the

pump energy supply from grid power to solar panels. Supporting documentation will also be

provided for the electrical system.

Water Testing

The project of testing the health of the aquaponics systems at both the Overholt’s clinic

and the vocational school through a system of periodic testing of the water’s chemical quality,

will deliver a system of chemical tests that will determine the levels of key chemicals in the

water. The determination of these key chemicals will allow the user to then conclude whether or

not the system is healthy, and, if the system is unhealthy, what is the root cause of the system’s

lack of health. Supporting documentation will also be provided for the testing system.

Solution Details


Through collaboration with the Overholts and investigation on the part of the OSU

project team, there were four potential solutions for the tank expansion at the Vocational School.

These design solutions included building a wooden frame with a rubber liner, framing and

8

pouring a cement pond, building a container from welded steel, and purchasing a pre-made water

container on site.

The first potential solution involved the construction of a sturdy wooden frame. This

would involve strong walls and supports, such as construction grade 2” x 4” supports, and

plywood walls. To make the structure water-tight, a commercial pond-liner, or rubber liner

would be purchased for use in the inner cavity to ensure a water tight seal in the container.

The cement pond option would involve framing a pond using construction grade wood

framing. This would require the structure to be framed for not only the inside of the pond, but

the inside contour as well.

The steel pond would be a sustainable method to use some of the excess materials on site

at the vocational school. From our initial investigation, there was deemed to be excess steel (rod

and plate) available for use. This design would consume those excess resources by using them to

construct a pond, welding the joints to provide a water tight seal.

The fourth and final potential solution would involve finding an adequate sized container,

and purchasing this container in Choluteca. Investigation for this resource would involve

communicating with the Overholts to determine an adequate tank for purchase. Among the

many different types of tanks that would be acceptable for use in this project, a type of container

intended for use is similar to a livestock water trough. These containers are sturdy for use with

large animals and have a large capacity range, with an ideal capacity of roughly 200-500 gallons.

Through discussion, these designs were analyzed to determine which would be the most

ideal for implementation on site at the vocational school. Rubber pond liners were researched on

the internet, and determined to be a very expensive option. Through discussion with the

Overholts, it was determined that the price of concrete would be outside the intended budget of

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the project. Along with cost, finding an adequate place to locate the cement pond would require

the construction of a large pad. Due to the rainy nature of the local climate and the muddy

ground conditions, a heavy cement pond would not rest on the ground during the rainy season

without some amount of sinking into the muddy ground. The welded steel pond tank would

require few purchased resources, but would also require the assembly of mismatched and

potentially incompatible parts to create the final product. From this analysis, it was determined

that the pre-made water container would be the most feasible and cost-effective design.

Communication with Larry Overholt regarding these designs also showed that purchasing

a pre-made container would be the optimal solution. With this, Larry searched for local sources

of water containers, and provided us with options to make a decision based on tank size and cost.

Through his investigation, he informed the project team of a local resource regarding water

containers, with tank sizes of1,100 liter ($160); 1,500 liter ($180); 1,700 liter ($230); 10,000 liter

($1,650). He also informed the project team of the possibility of finding a used tank for a

cheaper price depending on the size.

It is estimated that the grow bed currently at the vocational school has a volume

approximately of 190L (50 gal). This corresponds to about 95L (25 gal) of water that can support

up to 10 kg (20 pounds) of fish at a maximum according to the Aquaponic Gardening

Community, which suggests that for every three kilograms of fish, 50 liters of water and 100

liters of grow bed should be used. Additionally, the currently installed 360 gallon per hour pump

only will pass 90 gallons of water per hour on the 25% duty cycle and it is recommended by the

Aquaponic Gardening Community that the system is completely passed each hour, especially for

smaller systems. As a result, expanding the tank may not be within the scope of the project, as it

10

may risk the stability and health of the current system, however, it may be necessary to consider

expanding the grow beds to sufficiently clean the water.

Aquaponics Solar Power Supply

The purpose of the solar power supply is to reduce the clinic’s current reliance on

expensive grid power. The aquaponics system at the clinic uses two 80W AC pumps: one for

water circulation and one for aeration. These two pumps require 160W to operate. The current

system uses 160W over a 100% duty cycle, which may not be necessary. This system will use

timers to reduce the duty cycle. A schematic of the final system is shown below in Figure 1.

Figure 1: Solar power system schematic

We have access to 17 50W solar panels, so nominally four panels will be required to

provide sufficient power to the pumps. These panels are rated at 50W its maximum output, so

some margin of safety should be used to account for cloudier conditions. If we use a safety

margin of 1.5, the system will have to generate 240 W at its peak which requires 5 panels. Figure

11

2 summarizes these energy requirements. Nominally, this system will require a 250-400 W

inverter, so a 400 W inverter will be used.

Required Power

1 Panel 5 Panels 17 Panels Total0

100

200

300

400

500

600

700

800

900

Solar Power CapacityPo

wer

(W)

Since the pumps must run overnight, a battery bank is required. The system’s battery

bank should be sized so that it will last through the longest nights that Choluteca experiences.

The longest nights occur during the winter solstice, where nights are roughly 13 hours long.

To be safe, the battery bank will be sized to run for 18 hours in case of low sunlight days.

If a 12V battery bank is used, every 100W from the inverter requires roughly 10A DC from the

battery. The 20W overestimation accounts for the conversion inefficiency of the inverter. If this

current is to be drawn from the battery for 18 hours with a Duty% duty cycle, the total charge

drained from the battery bank will be:

160W

10 WA

×18 h× Duty %× 1.80

=Capacity A h

12

Figure 2: Solar power capacity and requirements

Notice that since deep cycle batteries should not be discharged below 20% capacity, a

factor of 1/0.80 is included in the formula. The linear relationship between maximum duty cycle

and battery bank capacity is shown in Figure 3 below.

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 1000

50

100

150

200

250

300

350

400

Battery Bank Capacity vs Duty Cycle

Duty cycle (%)

Capa

city

(Ah)

Figure 3: Battery bank capacity versus duty cycle

If both pumps are run at full capacity, one 12V 105Ah battery could supply a 30% duty

cycle. If any more charge is required from the battery bank, two batteries will be required. The

bank must also be charged back to its full capacity during the daylight hours, so the proper

number of solar panels must be used to ensure complete recharging during Choluteca’s shortest

days.

The solar panels output a peak voltage of 16V and peak current of 3.27A. Since the

battery’s charge will never drop below 20%, the solar cells only need to charge 80% of the

battery’s total capacity. We assume that the shortest day in Choluteca is about 11 hours, and 10

of these daylight hours are usable by the panels. Also, all output power is used to charge the

13

battery during the off cycle while all power generated in excess of 160W will charge the battery

during the on cycle. The number of panels required is related to the duty cycle by the following

relationship:

C A h=10 h× 3.27 Apanel

× (1−D% ) × N panels−10 h ×(160 W− 50 W

panel× N panels)

12 V× D %

This relationship is plotted below in Figure 4.

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 1000.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

18.00

Panels Required vs Duty Cycle

Duty cycle (%)

Num

ber o

f pan

els (

50W

eac

h)

Figure 4: Panels required to charge battery versus duty cycle

The project budget and scope are limited by the cost of deep-cycle batteries. Two 105 Ah

batteries will be used, which will allow the pumps to be operated on a 60% duty cycle, or the

equivalent of using 2304 Wh each day. This total power capacity can be split unevenly between

14

the two pumps if desired (duty cycles at 80% and 40% for example), which gives some

flexibility as to how the final system will set up. The total cost of the system is compiled in Table

1 below, noting that there is no required cost for the solar panels since they are already in the

clinic’s possession.

Table 1: Materials and costs for solar system

Item Cost

Solar Panels $0

Sunforce Q-Controller - 12V, 450

W

$58.57

Batteries - 12V, 105Ah (X2) $285.71

Whistler Pro Inverter - 200W $29.72

Timers (X2) $12.94

AWG 12-2 with ground $49.97

Miscellaneous and Shared Supplies(Wires, Switches, etc.)

$63.50

TOTAL $500.41

The system could be configured to only supply power to one pump or to split power

between the pumps in any ratio. The ultimate constraint is that only 2304 Wh of energy are

delivered to the pumps any given day, and the balance between the two pumps will be decided

on the visit. 9 solar panels will be installed to deliver this amount of energy, in addition to the

necessary additional energy for battery charging. These panels will output 3.27A X 9 = 29.43 A

at peak output conditions, so a 30A charge controller is necessary.

15

According to the recommendations by the Aquaponic Gardening Community, the total

volume should be circulated each hour. According the diagram of the clinic aquaponics system,

it was found that it required 11 hours for the entire volume of water to be circulated based on the

currently installed 1000 gallon per hour circulation pump. Calculations of this flow rate can be

found in the calculations in the appendix. While this does agree with the recommended flow

rates, its stability can be explained by the larger scale system that can better maintain a healthy

environment. As a result, it is suggested that the circulation pump be run at 100% to reduce the

potential risk of disturbing the established equilibrium, resulting in a 20% duty cycle on the

aeration pump. However, further consultation with the Overholts is required to decide the exact

duty cycle for the pumps.

Water Testing

Three products were selected to test and monitor the levels of key chemicals in the fish

tank of the aquaponic systems. The key chemicals to be monitored are ammonia, oxygen, nitrate,

and nitrite. The water’s pH and temperature will also be monitored. Ammonia, nitrate and nitrite

were chosen because they comprise the nitrogen cycle as shown in Figure 5. Oxygen, pH and

temperature were chosen because they must be kept within certain ranges in order to ensure the

health of the fish. The safe level ranges for these chemicals and indicators are listed in Table 2.

16

Figure 5: The nitrogen cycle in aquaponics systems

Table 2: Safe level ranges for key chemicals and indicators

Chemical or Indicator

Safe Range Units

Temperature 70 – 85 (20-30) °F (°C)pH 7-7.5Ammonia < 0.02 Ppm NH3/NH4

Nitrate < 25 ppmNitrite < 1 ppmOxygen 6-7 mg/L

The items purchased and their respective costs are outlined in Table 3. Twenty five nitrate

and nitrite test strips (both tests are on one strip) were purchased. The strips will change color

depending on the levels of nitrate and nitrite in the water. On the container there is a chart that

enables the reader to translate color shades to nitrate and nitrite levels. A similar method is used

by the Live Meter Master Test Kit to determine the water’s ammonia and pH levels. However,

the Live Meter Master Test Kit uses cartridges that continuously read the ammonia and pH

levels. The cartridges must be replaced once every four to six weeks. The Live Meter Master

Test Kit also monitors the temperature in both degrees Fahrenheit and degrees Celsius. Finally, a

17

miniature marine & fresh water test lab was purchased to detect dissolved oxygen levels. The

oxygen test requires chemicals to be mixed in a test tube. The liquid in the tube will then change

color depending on the level of dissolved oxygen present. Again a chart is provided that allows

the user to translate color into dissolved oxygen concentration.

Table 3: Costs for water testing supplies (no shipping or taxes)

Vendor Description PriceFresh Water Systems

Nitrate/nitrite water test strips

$7.89

Foster-Smith pH, temperature and ammonia monitor; refill kit

$38.97

That Fish Place Mini Lab oxygen test kit $11.89Total $58.75

Sustainability and Maintainability


By expanding the fish tank, the system may not be able to handle the increase in water.

Rather, the plant beds should be expanded in order to thoroughly clean the water and result in a

stable system. However, once the system is established, the aquaponics system will be able to

provide both vegetables and fish for consumption or sale. The system will only require input in

the form of fish food as the current system already has sufficient circulation for the size of the

tank from its solar panels and manual pump.

18


After installing solar panels and the electrical system, the grid energy required to run the

pumps as the clinic will be greatly reduced as the solar panels will produce a portion of the

needed energy. No regular maintenance is required to generate power and maintain the system.

Water Testing

Implementing water testing will allow for the ability to determine the quality of the

system. With the knowledge of the water quality, it will possible to identify potential risks to the

health of the systems. Water testing does require periodic interaction; however, it ensures that the

water is sufficiently healthy for fish growth.

Project Schedule

Pre-Trip Preparations

General

Prior to departure, the team has planned out how each specific task will be handled in

Honduras. Additionally, documentation and transportable purchases have been made. Because

this project will be implemented at the same time as a wind turbine project, each task will be

scheduled based on the worker demand of the wind turbine.


It is arranged so that a water container will be able to be purchased before or after arrival

depending on further, onsite assessment of the vocational school aquaponics system. Because the

system is located at the vocational school, it will be completed when there are idle workers from

the wind turbine project.

19


Some electrical components have been purchased. These items include the inverter,

timers, and the charge controller. The remaining electrical components will be purchases in

Honduras. Because the system is located at the clinic, a day will be arranged so that the

installation can occur on a day in which the wind turbine project requires fewer workers.

Water Testing

Water testing supplies have been purchased and creation of the supporting documentation

is in progress. Due to its multiple locations, this task will be completed at the same time as the

other aquaponics tasks. In country, the Overholts will be given the water testing kits and be

taught how to use them. They will also be taught how to determine when a system is unhealthy

and how to determine the lack of health’s root cause based on the results of the chemical tests.

This training will include supporting documentation to be left with them in country.

Implementation and Results


The lower plant bed of the system was expanded to accommodate a 2:1 ratio between the

volumes of the total plant beds and the fish tank, respectively. The first step of this process was

to calculate the volume of plant bed needed. Because of space limitations between the fence and

the pond, which was too heavy to move without draining, it was determined that the width of the

lower bed should be 32 inches. The longest piece of scrap wood that could be found and would

be suitable for the bottom of the bed was 48 inches long. The depth of the bed necessary to

provide the targeted volume of the plant bed within the previously determined dimensions was 8

inches.

20

The second step was to create the plant bed. Scrap wood was measured, cut and

assembled to produce a box with necessary dimensions. The box created to hold the plant bed

was built to be one foot deep. This allowed for a sufficient lip around the top of the plant bed to

support growing plants and ensure that the necessary amount of gravel could be added to the bed.

A thin plastic liner was attached to the inside of the box using screws to make the box water

tight.

The third step was to create a support structure for the plant bed. An extension was added

to the existing system structure that would support the box that had been put in place.

During the addition of the plant bed box, it was discovered that there was not sufficient

room to fit the lower plant bed between the upper plant bed and the fish pond. This was solved

by increasing the height of the upper plant bed, which involved adding supports for the bed

higher on the frame. Overlapping the upper and lower plant beds with the fish pond made it

possible for water to be drained from the upper plant bed to the lower plant bed and from the

lower plant bed to the fish pond via gravity powered siphons without additional water

transportation systems. The completed system can be found in Figure 6, below.

21

Figure 6: Aquaponics system at the vocational school after the expansion of the lower plant bed.


Pump Analysis

The first step in augmenting the Overholt’s aquaponics power system was to perform an

electrical assessment of the pumps’ energy usage. Detailed results of this assessment may be

found in Appendix B. The results showed that the two pumps were using a relatively low amount

of real power, only 46.1W and 15W, when their rated power was 80W. This energy usage results

in an estimated cost of $52.55 per year, assuming that electricity costs $0.10/kWh.

The team then tested the effect of reducing the pumps’ duty cycle on water quality. The

timers were installed and set to operate the pumps on a 50% duty cycle. No noticeable change in

water quality was observed as a result of reducing the duty cycle, which means that the original

estimation of the energy needs of the solar power system can be relaxed by one half. Details of

the water quality analysis can be found in the Water Testing section.

22

Panel Mounting

The team chose to mount the panels on top of a concrete support structure on the second

floor of the Overholt’s clinic, which is marked in a photograph in Figure 7. Here, the panels

could be illuminated throughout the day without occlusion from most of the surrounding trees.

Figure 7: Solar panel installation site

A steel mounting frame was used to hold the panels in place. The frame was lifted on top

of the concrete supports and rotated to face diagonally. Two steel C-channels were placed

underneath the frame to provide additional support, and the frame was tied to the concrete

support structure in several places with rope. The frame could house 9 panels on its southern-

oriented face and 8 panels on its northern-oriented face. Figure 8 shows a birds-eye view sketch

of the frame installation.

23

Figure 8: Birds-eye view sketch of solar cell support frame

Nine panels were installed in the southern-oriented face, and a steel crossbar was put

across the panels in order to prevent them from slipping out in heavy winds. The panels were

also attached to each other using thick steel wire, further securing the panels in their place.

Figure 9 is a picture of the complete array.

24

Figure 9: Finished solar cell array

Wiring

Once the location was selected, a 40-foot piece of wire was run from the panel

installation site to the breaker box controlling the panels. The wire was attached to the concrete

supports and electrical conduit using plastic zip ties and finally run through an electrical junction

box just above the breaker. The completed wire run is shown in a rough sketch with approximate

dimensions marked in Figure 10. Team member Killian Llewellyn is shown running the wire

through the junction box in Figure 11.

25

Figure 10: Wire run from solar panels to breaker

Figure 11: Wiring through the junction box

26

At the breaker, the switch controlling the circuit that the two pumps were on was

identified. Both pumps were on the same circuit, meaning that the final solar power system was

required to provide power to both pumps simultaneously, not one at a time. A transfer switch

was installed on the wall in order to allow the user to switch the system between grid and solar

power. The transfer switch and the terminal connections used for the circuit are sketched in

Figure 12 to show the flow of power, along with a schematic of the circuit. A photograph of the

final breaker wiring and transfer switch are shown in Figure 13. When the switch is placed in the

“up” position, the pumps use grid power, and when the switch is in the “down” position, the

pumps use solar power.

Figure 12: Transfer switch wiring and schematic

27

Figure 13: (a) Aquaponics system breaker wiring and (b) physical transfer switch

Then, the solar panels and battery bank were connected to the Sunforce charge controller.

The black wire from the solar panels was connected to the positive input terminal of the charge

controller, while the white wire from the panels were connected to the negative input terminal.

The battery bank consists of two 12V, 105Ah lead acid deep-cycle batteries wired together in

parallel. The inverter’s inputs were then attached to the battery, putting the black wire to the

positive terminal, and the white wire to the negative terminal. A sketch of the wiring is presented

in Figure 14.

28

Figure 14: Solar power system electronics wiring

Once all the circuitry near the breaker was completed, the panels were wired together.

The positive terminal of each panel was connected to the positive terminals of the panels on

either side, and the negative terminal of each panel was connected to the negative terminals of its

neighbors. In this way, the panels were wired together until the panel on the far side of the stand.

This terminating panel was also connected to the wire running down to the breaker box. The

black wire was connected to the terminating panel’s positive terminal, and the white wire was

connected to the panel’s negative terminal. The copper ground wire was connected to the solar

panel frame, completing the solar power circuit. Figure 15 shows what one wire connection to a

solar panel terminal looks like and Figure 16 shows a sketch of the basic connection on the

backside of the array.

29

Figure 15: Solar panel terminal wiring

Figure 16: Solar panel wiring sketch

Solar Power System Results

The solar system did seem to charge the batteries from a 50% charge to about an 80%

charge after one day. However, since the panels were facing south, they were only truly

illuminated during the first half of the day, and some of the battery charge seemed to have been

drained during the second half of the day. The panels were expected to charge more of the

30

battery, but they are somewhat old, so they individually did not output as much energy as

expected.

The transfer switch works fine, but the inverter would not deliver power to the pumps due

to insufficient battery bank charge. If the battery bank were charged more fully, the inverter

would be able to power the aquaponics pumps. Therefore, when the team left Honduras, the solar

system would not power the aquaponics pumps due to insufficient battery charge. The charge

may slowly build up over time and enable the solar use of the system.

Water Testing

The water in the fish ponds was tested at both the clinic and the school. At the school it

was determined that the nitrate levels were at a safe level, but were higher than desired. The pH

of the pond at the school was the opposite. It was within a safe range but was lower than its ideal

level. Therefore, the plant bed was enlarged. See the Vocational School Expansion section for

more details on the plant bed’s enlargement. While the data collected did not indicate highly

unfavorable water conditions, the sample was taken at a time when the system did not represent

its fully stocked state.

At the clinic all of the tested levels were close to ideal. A layout of the Clinic’s courtyard

containing all of the ponds and plant beds is shown in 17. All of the data from the testing is

included in Table 4.

31

Figure 17: Layout of the ponds and plant boxes at the clinic.

Table 4: Water Testing Data for the School and Clinic

Pond Date & Time Nitrate (ppm)

Nitrite

(ppm)

Ammonia (ppm)

pH Oxygen (ppm)

B Sunday 9:10 AM 0 0 - - 5B Sunday 7:30 PM - - 0 7.4 -A Sunday 7:40 PM 0-5 0 0 - 7C Sunday 7:45 PM 0-5 0 - - 5A Monday 7:20 AM - - 0 7 7B Monday 7:30 AM - - - - 4C Monday 7:30 AM - - 0 - 5

School

Wednesday 8:45 AM 5 0 0 6.6 9

A Wednesday 4:45 PM 0 0 - - 10C Wednesday 5:00 PM 0 0 0 - 8B Wednesday 5:15 PM 0 0 0 - 8

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Schedule and Budget

The first day of work involved water testing and the solar panel installation. Water testing

was performed on each tank at the clinic and the water quality information was recorded. The

solar panels were tested and the mounting frame was positioned to its final location. The

preliminary wiring was performed and the duty cycle was reduced by timers.

The second working day was used to finish panel installation and wiring. The batteries

were purchased and the transfer switch was fully wired. The system was left to allow the

batteries to charge.

The third day of work was used to analyze the school aquaponics system and begin the

tank expansion. The result of the third day’s work was a completed plant bed box for the system.

The fourth day involved augmenting the existing framework and adding additional

support to the frame in order to establish a functioning system.

The total costs of the preparations for the trip were $185.72. This included purchasing

components for the electrical system without batteries, water testing materials, and

miscellaneous components such as wires. The cost of supplies purchased in Choluteca was

$314.69, the majority of which was the cost of the batteries. Additional purchases included more

wire and transfer switches. The net total cost of the project was $500.41.

Future Recommendations


For future improvements, it is suggested that the entire system should be expanded to

provide a larger system capable of providing a useful amount of resources. For further

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expansion, the ratio of the plant bed volume to fish tank volume should be maintained at a 2:1

ratio. Additionally, further expansion of the fish tank volume would either require a pump that is

capable of passing more water through per hour or a better energy system, such as an increased

number of solar panels, to support the pump at a higher duty cycle.

The expanded plant bed box used a sheet of tarp and scrap wood in order to hold the

material for the plant bed. However, the materials used were not suitable for long term support.

The tarp was not intended to hold water and scrap wood used appeared to rapidly decay when

exposed to the open environment. As a result, the crafted box may not hold water properly or it

may structurally collapse from decaying parts. Future teams should explore methods of creating

a more durable box using materials specifically designed to hold liquids.


It is recommended that the additional eight solar panels should be installed in order to

provide more energy to charge the batteries in less time. The wire chosen for wiring the panels

together would have to support a larger amount of current, up to 20 Amperes. The gauge of wire

presently installed meets this condition.

Water Testing

Water testing should be regularly performed in order to monitor the health of the system

and a record should be kept of the results. If changes are made to the system, the frequency of

testing should be increased.

Conclusion

After 10 weeks of planning, plans for solar panel installation and water testing were

prepared for implementation. In Choluteca, the solar panels were successfully installed; however,

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due to time constraints, the efficiency was unable to be determined. Even though the efficiency

was not determined, it was found the energy requirement of the pumps was less than expected

and, as a result of lowering the duty cycle, the pumps required less energy which reduced the

cost of running the pumps regardless of the efficiency of the solar panels.

Water testing was started and used to monitor the effects of the changes to the duty cycle

of the pumps. The data from the clinic pools indicated that no significant changes affected the

system with a reduced the duty cycle. The water testing data from the school system suggested

that water quality was not entirely responsible for failure of the system; however the low number

of fish present may not accurately represent the system at its fully operational state.

Due to the availability of extra workers, one of the plant beds was expanded. The plant

bed was successfully expanded to hold a larger amount of plant bed so that the appropriate ratio

could be obtained between plant bed and water volumes. While the size was successfully

increased, the materials used in the expanded tank did not appear to be able to withstand the

outdoor environment, which generates the need to research better materials or strategies for

holding plant bed materials.

All three projects were able to successfully demonstrate features for creating a

sustainable aquaponics system that can serve as a model for other systems. The solar panel

installations demonstrate using solar energy for running aquaponic pumps. The water testing

presents a model for maintaining a healthy system. By expanding the plant beds, the importance

of having a proper plant bed to water volume ratio was shown. Additionally, the aim for a low

budget expressed the capability of creating such a system without resorting to heavily priced

alternatives. Ultimately, the three projects were capable of providing examples of the key

features of aquaponics as a sustainable technology.

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Appendices

Appendix A: Electrical Datasheets

Figure A1: Solar Panel Nameplate

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Appendix B: Electrical Assessment of Aquaponics System

17-24 March 2012

Electrical AssessmentOverholts’ Aquaponics PumpsCholuteca, Honduras CA

Date 18 March 2012Time 8:45AM local

Location Overholts’ house, Choluteca, HondurasDevice Lower aquaponics submersible water pump, Tetra WGP1000, 1000g/m

80W 120VAC 60Hz, www.tetrawatergardening.com, operating at 100% duty cycle

Voltage 117VACPower factor 0.69

Frequency 60HzVolt-amperes 66.7VA

Amperes 0.57APower 46.1W

Watt-hours 0.58kWh (energy usage over elapsed time)Elapsed time 12h 34m

Estimated cost/year $40.29/year @ $0.10/kWh (scale to actual rate)

Date 19 March 2012Time 7:55AM local

Location Overholts’ house, Choluteca, HondurasDevice Upper aquaponics submersible water pump, Tetra WGP1000, 1000g/m

80W 120VAC 60Hz, www.tetrawatergardening.com, operating at 100% duty cycle

Voltage 117.5VACPower factor 0.20

Frequency 60HzVolt-amperes 72.6VA

Amperes 0.62APower 15W

Watt-hours 0.34kWh (energy usage over elapsed time)Elapsed time 23h 16m

Estimated cost/year $12.26/year @ $0.10/kWh (scale to actual rate)

Test equipment: P3 International P4460 Kill-O-Watt EZ electric usage monitor

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http://www.tetrawatergardening.com/

http://www.tetrawatergardening.com/

Calculations

Clinic Water Volume and Circulation Calculation

Volume: (3.8*1.93*0.44) m3 + (2.35*1.77*0.7) m3 + (3.76*3.76*2.58) m3 = 42.61 m3 = 42610 L

Circulation: 42610 L * 0.264 gal/L * 0.001 hour/gal = 11.25 hours for complete circulation at

100% duty cycle of the circulation pump.

Auxiliary Figures and Tables

Figure A1: Clinic Aquaponics System Overhead Layout

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DocumentsThe Aquaponics Team Agreement

Team Members

Killian Llewellyn, Lisa Reisenauer, NialTilson, Tom Zajdel

Team Project Expectations (Course requirements,workplan, etc.)

All meetings require punctuality, attendance, and active participation. In the event of failing to comply with the previous expectations, team members are expected to complete any assigned work and submit prior to the meeting. Members are responsible for any material discussed and distributed at the meeting.

All members are expected to achieve the tasks set by the established timeline. Should tasks fail to meet deadlines, it must be brought to the attention of the group immediately and addressed accordingly.

Team Leader shall keep record of all team meetings and post a summary of the meeting events that is available to all group members after the meeting.

Team Member Roles and Responsibilities (Team leader, secretary, etc.)

Team Leader – Lisa Reisenauer

Documentation – Killian Llewellyn

Historian –Tom Zajdel

Team Meeting Ground Rules (Decision-making, discussion, etc.)

All members must be mindful and respectful of the thoughts, opinions, ideas, and strategies of each member.

Constructive criticism shall be used appropriately and effectively. All members should be mindful that no criticism shall be intended as a personal attack.

Team Member Signatures

1. __Killian Llewellyn_________ 2. ________Lisa Reisenauer_________

3. __NialTilson_____________ 4. ________Tom Zajdel_____________

Date signed ___1/11/2012______________

Document 1: Aquaponics Team Working Agreement

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