ET 494 – Senior Design II

Solar Parabolic Mirror

Hot Water Distiller

Final Report

Shae Lessard

Advisor: Dr. Junkun Ma

November 30, 2012

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I. Abstract

In this senior design, I worked on making a solar, salt or river water distiller. This device will take contaminated river or salt water and convert it into safe drinking water. What I was set on doing for my project is making a solar distiller that will provide enough fresh drinking water for an average household in one day. This was made for families in rural areas that may not have an option for city or well water. If these people do however have a salt water source or other source where the water is contaminated, they can use my design to get a sufficient amount of fresh water for a day. I have designed the project up to the parabolic mirror, container, and automation of the system. Due to setbacks and the difficulty of acquiring materials, I was only able to test different types of water, build my parabolic mirror in the time given, and do testing on the energy output of my parabolic mirror. Some of the materials, such as the old satellite dish were hard commodities to come by. The process of having the final design automated will be finished next semester.

II. Methodology

Water TestingThe main idea behind this design was that water can be filtered of most contaminates,

through the heating of water until it evaporates, and then catch and cool the condensation back down to water. After this process is complete, one has clean water and the part of the contaminated water that cannot be filtered anymore is removed.

The part of this design that took some research was finding out exactly what is considered clean and safe drinking water? My design did not need any additional filtering after coming up with the results of my water tests. The way I decided if my design needed any additional testing was finding out exactly what my distillation removed from local water. The water I tested was water that is readily available around this area of Hammond. I tested pond water and local river water. My tests tested the water for bacteria, pesticides, nitrates, ph, hardness, chlorine, and lead. There were some obvious contaminants that would not be in the local water but I tested for them anyways because they came with the kit that I purchased. I did tests before and after the pond and river water was distilled to see what the difference was and to have a control to compare data. The method of distilling the water was very simple. I boiled my water samples on the stove in a pot with a parabolic lid on it and inserted a smaller bowl in the center to collect the condensation collected on the top. There is an example of what was done in figure 1.

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Figure 1

I also got pictures of what was left over after the distillation process was done. In figure 2 was what was left of the river water after it was distilled and figure 3 was the clean water that was collected from the parabolic lid.

Figure 3 Figure 4

Figure 5 is a picture of the complete test kit that was used. In figure 6, 7, 8, and 9 are pictures of all the different tests in the kit.

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Figure 5 Figure 6 Figure 7

Figure 8 Figure 9

Figure 6 is the bacteria tests, figure 7 is the lead and pesticide test, and figure 8 is the Nitrite test. The results from the tests were actually surprising. The distillation removed pesticide and nitrate/nitrite from the river water and changed its hardness. The hardness before the tests, however, was already low enough to be considered safe. The distillation also removed the harmful bacteria from the water as expected. In figure 10 I have all the results and what the specified EPA standards are at the bottom of the graph. If the test was a simple p/n, meaning positive or negative, it simply means that the test showed that the level was either above or below the EPA standards. Ppm stands for parts per million and ppb stands for parts per billion.

Test Bacteria(p/n)

Pesticide(p/n)

Nitrate/Nitrite(ppm)

pH(ppm)

Hardness(ppm)

Chlorine(ppm)

Lead(p/n)

Pondw/o dis.

P N 0.5 6.5 0 0 N

Pondw dis.

N N 0 6.5 0 0 N

Riverw/o dis.

P P 0.5 6.5 25 0 N

Riverw dis.

N N 0 6.5 0 0 N

EPAstandards

None Below 3 Below10 Between6.5-8.5

Below 50 Below 4 Below15 ppb

Figure 10

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Calculations

The calculations I did for this project had to answer my questions of the how big this design should be and how well would it work. The questions I had to answer with these calculations were, how much water can I boil and distill with only so much surface area reflecting back the sun’s rays? I had to figure out what was a manageable amount of water to boil, at what efficiency will my parabolic mirror reflect back sunlight, and what amount of energy was the sun emitting directly.

My calculations started with how much water I wanted to boil. The way I did this was to plug different amounts of water into my calculations until I got a decent time to boil and condense all my water. I would up picking two and half gallons. In my original calculations with my parabolic mirror putting out 75% efficiency, it would take about 23 minutes to boil and 2 hours and 43 minutes to evaporate the whole two and half gallons of water. The calculations start the initial and final temperature of the water. I also have to find the mass of the water I want to boil. Once this is found, I figure out the energy required to boil the water and the energy required to evaporate the water. Once I know the energy required to do all this, I figure out the amount of energy my parabolic mirror will put out by knowing the surface area of my parabolic mirror and assuming that it will capture and reflect back at a focal point all this energy. I then add efficiency to my calculations for imperfections in the mirror. From this, I calculate my time to boil and evaporate the water. Later in this report, through tests, I find out my calculations are a little off due to the fact I assumed the best energy per square meter I could get was 1000 watts per square meter when in fact the average watts per square meter is larger. In figure 11, I have included all my calculations in Microsoft equation 3.0.

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ΔT=T f−T i=100oC−23oC=77oC

2 .5 gallons∗3.78 kggallon

=9 .45 kg

9 .45 kg∗1000 gkg

=9 ,450g

specific heat of water=4 . 184J /( goC )Energy required to boil water=9 ,450g∗77oC∗4 .184 J /(goC )=3 ,044 ,487 .6 J

Energy required to evaporate water=2260Jg

∗9 ,450 g=21 ,357 ,000 J

Surface area avalible=surface of a paraboloid=πa6 h2 [ (a2+4h2 )3/2

−a3 ]where a is radius and h is height .

Focal po int perpindicular from the center=π 3 ft6 (1 ft )2 [ ((3 ft )2+4 (1 ft )2)3/2

−(3 ft )3]=31 .22 ft 2

1m2=10 .763 ft2

31 .22 ft 2∗1m2

10 .763 ft2=2.90m2

η=75 %

energy avalible from mirror=2 .9m2∗1000Wm2 =2 ,900W

2900W∗0 .75=2 ,175W

time it will take to boil=3 ,044 ,487 .6 J2,175J /sec

=1399 .76 sec s

time in minutes=1399 .76 sec s∗1 min60 sec s

=23 .32 min s

time to evaporate all 2 .5 gallons completly=21 ,357 ,000 J2 ,175 J /sec

=9819 .31 sec s

time in hours=9 ,819 .31secs∗1 min60sec s∗

1hr60 min s =2hrs 43 min s

Figure 11

How the design will operate

The way this design will work was a challenge at first, but I soon figured out that through a few specialized parts and control of a mirco-controller, I could automate my system relatively easily. The pumping and cleaning system will get power from a 12 volt battery hooked to a solar panel for charging. The way the system will work at the end of next semester, once all the pieces are put together and I have all the components working correctly, the pump will start by pumping water into my container until a level switch is pushed up and opens the circuit for the pump. The container will refill itself during the day as the water level drops due to evaporation and condensation. The container is designed to capture the condensation captured on the lid and the

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water vapor through a condensing coil. Here is a picture of the pump and the level switch that will be used in the design in figure 12 and 13 respectively.

Figure 12 Figure 13

Once the container is filled with approximately two and a half gallons of water, the parabolic mirror will focus the suns light energy at the container. The container will be mounted at the focal point of the parabolic mirror. I have included a picture of the satellite and the material used to cover it in figure 14, 15, and 16 respectively.

Figure 14 Figure 15 Figure 16

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The Cleaning SystemThe container will also have an automated cleaning system that will be controlled by a

arduino uno microcontroller and a h-bridge ran through a low pass filter running a 12 volt valve. The valve is normally closed and when 12 volts is applied, the valve will open. The valve will be mounted to the bottom of the container so it will drain. At night when the container is not distilling water, the micro-controller will tell the h-bridge to send power to the valve and the valve will open. Once the valve is open, the water will drain out of the container making the level switch close and turning of the pump. The arduino will be programmed to leave the valve open for three minutes letting the pump run and flush water through the container. Once the time is up, the valve will close and the container will fill, opening the level switch and stopping the pump. There is a picture of the valve, h-bridge, and the arduino below in figures 19, 20, and 21 respectively.

Figure 20 Figure 21 Figure 22

The valve will be timed to open for three minutes at night every twelve hours so the system will flush itself, refill, and wait for the next twelve hours to pass. I wrote a sample arduino program just to make sure the valve will open and close using an h-bridge. The program below was just a sample program, but the final program will be very similar if I leave the cleaning only based on a timing parameter. The program in figure 24 below opens and closed the valve every five seconds. The valve was run through a low pass filter and powered by a power supply. I have included a venn diagram of how the cleaning system will work in figure 23 below.

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Figure 23

Figure 24

AutoCad DrawingsI also drew my container and lid in autocad, which is currently being made of 1/8” food

grade stainless. The drawing of the container and lid are shown below in figure 25 and 26 respectively.

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Figure 25

Figure 26My testing of the parabolic mirror actually gave me some interesting results. I first had

to cover my satellite dish with my reflective material. I found out after covering my satellite, I covered more surface area than originally calculated. I will show this in another set of calculations I recalculated after this test. In my testing of my parabolic mirror, I was loaned a device that measures light energy per surface area. There is a picture of this device below in figure 27.

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Figure 27

I first took a few measurements of what the sun was putting out at the time with no clouds and it averaged 1500 watts per square meter. This also changed some of my calculations performed earlier. I then attached it to a two by four and aimed it the focal point of the parabolic mirror. Here is picture of the mirror, and how I tested the it with the meter in figures 28 and 29.

Figure 28 Figure 29

The meter actually topped out at 220 0 watts per meter when I was trying to test the output of my parabolic mirror, so I was not able to figure out exactly what the output was at 1500 watts per meter. In my first calculations, I estimated that it would put out about 2175 watts, so this tells me that the parabolic mirror exceeded my expectations. The amount of heat this parabolic mirror was focusing was well over what I had expected. I did a quick experiment to see how long it would take to change the surface temperature of two by four painted black to capture the light. The results were very surprising. I was able to change the surface temperature of this two by four from 83 degrees Fahrenheit to 420 degrees Fahrenheit in a minute and twenty three seconds. I was also able to catch black construction paper on fire in 47 seconds. These were just to show the shear energy the mirror in concentrating at the focal point. Here is a picture of the surface temperature test and catching the paper on fire in figures 30 and 31 respectively.

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Figure 30 Figure 31

We also got hungry and fried two eggs in a 10 inch skillet. This took about 13 minutes to completely cook the eggs. I have included two pictures of this below to show how this was done and the end result respectively in figures 32 and 33.

Figure 32 Figure 33

Here are my calculations after figuring out my actual surface area and knowing the average amount of energy the sun is emitting. Here are my second calculations after knowing these new facts in figure 34 below.

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ΔT=T f−T i=100oC−23oC=77oC

2 .5 gallons∗3.78 kggallon

=9 . 45 kg

9 . 45kg∗1000 gkg

=9 ,450g

specific heat of water=4 . 184 J /( goC )Energy required to boil water=9 ,450g∗77oC∗4 .184 J /(goC )=3 ,044 ,487 .6 J

Energy required to evaporate water=2260 Jg

∗9 ,450 g=21 ,357 ,000 J

Surface area avalible=surface of a paraboloid=πa6 h2 [ (a2+4h2 )3/2

−a3 ]where a is radius and h is height .

¿ π 40 .5 in6(7 .5 in )2 [((40 . 5in )2+4 (7 .5 in )2)3/2

−(40 .5 in )3]=5325 .87 in2

5325 .87 in 2∗1 ft12in

∗1 ft12 in

=36 . 99 ft 2

36 . 99 ft 2∗1m2

10 .763 ft 2=3 .44m2

η=75 %

energy avalible from mirror=3 . 44m2∗1500Wm2

=5160W

2900W∗0 .75=3 ,870W

time it will take to boil=3 ,044 ,487 .6 J3 ,870 J /sec

=786 .69 secs

time in minutes=1399 .76 sec s∗1 min60 sec s

=13 .11min s

time to evaporate all 2 .5 gallons completly=21 ,357 ,000 J3 ,870J /sec

=5518.60 sec s

time in hours=9 ,819 .31 secs∗1 min60sec s

∗1hr60 min s

=1hr 32 min s

Figure 34

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The new supplies and design changes where due to better heat dissipation than the original design and cheaper. The design changes were three main things: container change, a check valve for the inlet of the container, and using water to dissipate heat from the condenser instead of using a fan and air. The main reason for changing the container design was because of cost. The original design previously mentioned would have cost around $750 to build and would have been hard to drill into once made because it would have been made of stainless.

The second design change was the check valve mounted on the side of the container. This was mounted to the inlet of the container from the pump, this was to make sure steam did not flow through my inlet line and into my pump and damage it. The pump I choose was not made for high heat and it prevented steam loss.

The last design change was the how the condensing coil was cooled. Cooling it with water instead of air was because water dissipates heat better than forced air can.

In figure 35, are pictures of the new supplies I had to incorporate into the design.

Figure 35

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These are some more pictures of the other supplies acquired for the design in figure 36.

Figure 36

One the main problems I had with the new container was getting it to seal because I could not weld on it because I did not know anyone and I cannot weld aluminum. The only way I could mount my check valve inlet and electric valve was by drilling a hole the outside diameter of the pipe diameter and mount it with gaskets and lock rings. Even with this it still leaked. I wound up using JB Weld epoxy and high temperature RTV silicon. You can the supplies in figure 37.

Figure 37Another obstacle with the container was the color. A shiny pot would reflect most the

light energy instead of absorbing it. This was not too hard to figure out though. I did have some difficulty finding heat paint. It also had to be flat black so none of the energy was wasted.

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I found a flat black high heat header paint from the automotive store that was perfect. There is a picture of the paint used in figure 38, and a picture of the container in figure 39.

Figure 38 Figure 39The next challenge was making the valve and pump operated as told earlier in the report.

I used the Arduino to talk to my h-bridge. I had a level switch hooked up to 5 volt signal going to a digital input. Whenever this level switch was closed, the Arduino would get a high signal input into pwm pin 3 and my code tells it to send a high signal to the h-bridge. This signal was ran through a low pass filter and into S2 input which told the h-bridge to give power to M2B and M2A from the battery inputs based on the type of signal I fed in. The h-bridge will receive a pwm signal as long as it is feed through a low pass filter. This signal could be from 0 to 255. This sends out a range signal from 0V to 5V, this in return determines the amount of voltage given to the motor outputs from the voltage source. In my case the voltage source was a small 12V motorcycle battery. The valve was also controlled by a pwm signal the same way but was just timed to open at night so the container would clean itself of all the contaminates from the day. I drew the circuit for the electrical box I built to do this and have the code here. The circuit is in figure 40 and the program is in figure 41.

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Figure 40

Figure 41

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In figures 42 and 43 are pictures of the electrical box built.

Figure 42

Figure 43

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The next part was putting the condenser together. The condenser was pretty simple. I found a 50 foot copper coil online already made for a home beer brewing kit. It was kind of pricey but worth. Once I got copper coil, I found out it fit almost perfectly into a five gallon bucket. So I made it out of the bucket. I put the inlet sticking out from the top, bent the outlet to the bottom and drilled put it coming out the bottom. I also attacked a valve to the bottom so I could drain the condenser water and refill it if got too hot; this was so I could leave the condenser attached the frame while I drain it and fill it I used JB Weld to seal the condenser container. The condenser is show in figures 44 and 45.

Figure 44 Figure 45

Here are some pictures of the complete design put together in figures 46, 47, and 48.

Figure 46 Figure 47

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Figure 48The next part after working out the kinks was the test results. They wound up not being

nearly as good as I predicted last semester when I just did testing on the parabolic mirror. The amount of energy the design was able to capture and use was not nearly as great as thought to be in previous calculations. The design only had a 18.66% percent efficiency rate only capturing 962.87 watts. The average output of the distiller after it got to boiling temperature and boiling was 3.87 cups per hour. In figure 49 are my calculations to come up with these results.

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Figure 49One of the last parts to this the last project was figuring out whether the distiller filtered

out the contaminates and passed EPA standards when done. So I ran the same test I ran the first semester. I tested the water before and after distillation to check for the differences and what the distillation removed. The results were very similar to the home tests done on the stove the first semester. It killed the bacteria present, removed the little nitrates and hardness in the water. Figure 50 contains the results.

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Test Bacteria(p/n)

Pesticide(p/n)

Nitrate/Nitrite(ppm)

pH(ppm)

Hardness(ppm)

Chlorine(ppm)

Lead(p/n)

Pond w/o dis.

P N 0.5 6.5 25 0 N

Pondw dis

N N 0 6.5 0 0 N

EPAStand.

None Below 3 Below 10 Between 6.5-8.5

Below 50 Below 4 Below15ppb

Figure 50Also in figure 51 I have included some before and after pictures of the water being distilled.

Materials Pricing List

Item Cost/unit Quantity CostMicro Controller 20.77 1 20.77

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12V Valve 68.47 1 68.4712V Fan 40.42 1 40.42Jumper Kit 6.37 1 6.37Pump 24.01 1 24.01Adhesive mirror 16.99 17 288.83temp switch 22.65 1 22.65h-bridge 82.99 1 82.99level switch 60.36 1 60.36satellite dish 50 1 50fuel 165 1 165water test 12.88 8 103.04shipping 39.76 1 39.76bowl 4.27 1 4.273/4" check valve 12.64 1 12.6416 quart pressure cooker 71.54 1 71.5425'-3/16" copper tubing 39.32 1 39.32container 280 1 280Colmen 5 gallon containers 11.26 2 22.523/8" copper chiller 89.99 1 89.99frame material 90.48 1 90.48bolts and lock rings 38.01 1 38.018"x8" pvc electrical box 21.98 1 21.9850" rubber hose 32.98 2 65.96Galv. wire 7.67 1 7.673' of 1/2" all thread 6.5 1 6.5fuses, fuse holder, switch 16.57 1 16.57laser thermometer 62.41 1 62.41capcitors, resistors 2.59 1 2.59high heat pvc tubing, fittings 28.62 1 28.62tie wraps and sticky backs 4.66 1 4.66avt high heat silicon,regular 13.34 1 13.34couplings, reducers, ect. 10.37 1 10.37

Grand Total 1862.11

III. Timeline Fall 2012 September 5 – Have my proposal done and approved. Present my proposal. Start

buying additional parts needed.

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September 19 – Receive parts. Have a new container decided on and start working on integrating parts into new container.

October 3 – Have frame to hold up parabolic mirror and component box built. Start working with all parts received.

October 17 –Have component box built and start having components interact with each other.

October 31 – Keep working on having parts interacting with each other. Add any additional components if needed.

November 14 – Have all new components working with design and start testing results. Test heat conversion results and test water samples to make sure the distiller is filtering water properly.

November 28 – Finish up final presentation and report.

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