Completing the solar panel

I finished my solar panel project this week. I’ve been working on it on and off for the past two years and it’s finally done. The only thing I need to complete is to put the clear acrylic panel on top to protect the cells.

Here are my previous posts on building the solar panel. Part 1 gives information on the parts I bought to build the 18 volt, 60 watt PV solar panel. Part 2 describes my frustration of learning to solder the cells and the time needed to do this well. Part 3 describes my attempt to solder the tab wire to the negative part of the cell and how I’m going to wire the cells to produce the correct voltage.  This last post will summarize the task of completing the solar panel before school starts and what my future plans are with solar power panels.

Video of the completed solar panel

It took me a couple of days to complete all the soldering. I got better at it as I went along and only broke a few cells. Luckily I bought enough and I still have about ten left. The hardest part was dealing with corrosion that built up on the tip of the soldering pen and getting an even flow of solder to flow onto the three positive connections on the back of the cell. I had to scrap a few cells because of poor solder connections.

As you can see from this image, the back of each cell has six places that need to be soldered. This side is the positive side and was the hardest part to solder because each of the six squares needed to have a small piece of solder deposited before I could solder using the tabbing wire. Some people recommend that you hold down the tabbing wire with a small piece of wood when you are soldering them together, but I found that a small book worked better and was not too heavy.

 Assembling the cells

After all the cells were completed, I had three strings of twelve for a total of 36 cells. Each cell has 0.5 volts so this should give a total output of 36/2= 18 volts.

I was now ready to attach the cells to the inside panel. I put a small drop of silicone on the back of each cell and gently pressed them into place in the panel box. After I had them  lined up in three rows, I soldered the rows together in series using the larger tabbing wire. I then used some spare wire I had to make the final connection between the positive end and the negative end to complete the solar panel.

The big test

I actually completed the solar panel and wiring  in the middle of August, but I couldn’t test it as it was raining for days on end. I did take a quick reading inside by the window then and read 4 volts. I thought maybe one of the cells was not soldered correctly, but thankfully, it was due to the clouds and rain condition. This past Friday I went to school to test the solar panel as it was a bright sunny day. On the first measurement, I recorded 19.0 volts. It made my day knowing the solar panel was working correctly. It went up to 19.1 volts in all sun and down to 18.3 when a cloud passed by. The total cost for this project was about  $160.00. I didn’t need to buy some small pieces of wire, screws and paint as I already had some laying around. The biggest cost was the solar cells.

What’s next

My next task is to research and find a deep cycle battery and an inverter to connect to the panel. The battery is a very important part of the system as it stores the energy to power any appliances. This panel may only light a 60 watt bulb for a short time, but I will investigate other types of lights like LED lights and other small appliances to see how long they can be powered using one or two panels. I also may try and build another solar panel using all acrylic and no wood. This solar panel that I just completed would never hold up on a roof for very long and that was not the intention here. I will put in in the sun during the day and bring it in at night.

My goal was and is to learn as much as possible about manufacturing low cost photovoltaic systems (PV systems) that can be made and used in the Philippines. The Philippines already has some of the largest solar manufacturing plants producing the worlds solar cells. The problem is that the cells manufactured in the Philippines are exported to other countries because of the high cost and regular Filipinos not being able to afford these systems.

I believe that bringing this do-it-yourself solar panels, make-your-own-technology to the Philippines will help with innovation in making and using low cost panels. Professional made PV systems are expensive because of the very high manufacturing cost associated with the solar panels designed to last 20 – 30 years, or more. I believe the cost can be greatly reduced if more people are given a chance to experiment with ( play with) and design smaller systems to last in the 3-5 year range. These smaller systems could be brought in during the night to save on wear and tear due to moisture, rain, and general outdoor conditions.

This was a great project for me to build. It’s a good example of bridging the gap between theory and practice. Much is written on building PV systems and the electrical theory involved, but few people actually build the solar panels and experiment with them. Everything doesn’t have to last 30 years. I’m sure there are better and more cost efficient way to assemble these panels that haven’t been discovered yet. Filipinos are very resourceful and need to have solar electricity development in their economy. Given the Philippines’ abundant sunshine and its large work force, solar power and the Philippines is a perfect fit.

This week I gave a demonstration of the egg in the bottle to my classes. This is a favorite demo and I always enjoy doing it. This is a good demo when learning about pressure. To start, burn a piece of paper and put it into the bottle and quickly put the hard boiled egg on top. As the fire goes out, the pressure inside goes down and the higher pressure on the outside pushes the egg in.

Here is a link to my last science lab- the hexaflexagon, which we did last week and you can see the video to learn how to construct and add content to the hexaflexagon.

I have seen this egg demo using a small water balloon and it works the same. To get the egg out, you can try to blow into the bottle which has never worked for me. I usually use an Alka Seltzer and water to pop the egg out. I have also used putting the bottle under hot water to warm the air inside the bottle to expand and push egg back out.

Extensions and discussion

It’s difficult for students to visualize a change in pressure until they see this demonstration. Some of the students have experience going under the water and experiencing increased pressure in their ears, and that helps to understand the concept.  For the egg here, it’s the pressure difference that pushes the egg in.

Also, be careful to explain that the lack of oxygen alone doesn’t “suck” the egg in. After I question the students, I explain how the egg goes in and then have them explain to their lab partner. At the end of the class, I have them write their explanation on paper about the egg demo and hand it in so I can check for any misunderstanding.

Making and encoding the video

Here is my latest video on the egg in the bottle video. Again, I used iMovie and since the demo is short, I used a movie trailer. This worked out well as the audio has music and the audio from the classroom was very chaotic. I encoded the flv video as the highest level, which gave me a file size of about 39 meg.

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This week we built hexaflexagons in class and added science content on each of the four sides. I thought since the water cycle has four main vocabulary terms, it would be creative to put one vocabulary word on each of the four sides. We also used this for the layers of the atmosphere. Hexaflexagons have four sides and can be constructed with only one piece of paper.

This activity builds enthusiasm for learning science and is a good hands-on activity– much like the great bag of science. See the video gallery for all the science videos here.

History of the hexaflexagon

I first learned about hexaflexagon from Martin Gardner when I was in college.  In his book, Mathematical Puzzles and Diversions, Gardner shows a few different ways to construct a flexagon and hexaflexagon. Even though Gardner wrote about the hexaflexagons, others are given credit for their discovery. A graduate student named Authur Stone, while at Princeton University, created the first flexagon by playing around with some paper in math class.

This is a fun activity to do when you have four of something. I also did this with another science class with the layers of the atmosphere.

Here is the video on how to construct your own hexaflexagon. I made this video with iMovie and did a voiceover to give directions on how to construct the hexaflexagon. I exported with mpeg-4 as a Quicktime movie and encoded to flash using iSkysoft Video Converter.

How to fold the hexaflexagon

Start with a piece of paper with the length twice as long as the width. From there, follow my video instructions to complete your own hexaflexagon. Students can add content before or after it’s done. We have made both small and very large hexaflexagons in class over the last few years. Using colored markers is easier that colored pencils as the markers don’t press in on the paper. Remember, the better you make the creases, the easier the hexaflexagon will turn. Watch the video for directions.

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I did this activity with all my students and it was a long day yet lots of fun.

If you have any extensions, comments, or ideas let me know in the comments.

Here is a link to their website.

Click the image to go to the site and give it a try. I’ll give some hints on how this works in the comments. Try it a few times and see if you can find the number theory behind Robin.

I have this drinking bird on my desk and the kids can’t stop watching it. It keeps drinking the water all day long. As long as I keep adding water to the beaker, the bird will keep drinking. It’s not really drinking the water, just dipping its beak in the water. The water evaporates and cools the beak, thus the liquid moves up.

From Wikipedia

1. The water evaporates from the felt on the head.
2. Evaporation lowers the temperature of the glass head (heat of vaporization).
3. The temperature decrease causes some of the dichloromethane vapor in the head to condense.
4. The lower temperature and condensation together cause the pressure to drop in the head (ideal gas law).
5. The pressure differential between the head and base causes the liquid to be pushed up from the base.
6. As liquid flows into the head, the bird becomes top heavy and tips over during its oscillations.
7. When the bird tips over, the bottom end of the neck tube rises above the surface of the liquid.
8. A bubble of vapor rises up the tube through this gap, displacing liquid as it goes.
9. Liquid flows back to the bottom bulb (the toy is designed so that when it has tipped over the neck’s tilt allows this), and vapor pressure equalizes between the top and bottom bulbs
10. The weight of the liquid in the bottom bulb restores the bird to its vertical position

We’ve been here in Mindanao, Philippines for almost two months now, and tomorrow we are leaving to go back to Pennsylvania. Our bags are packed and we are ready to go. Our taxi will pick us up tomorrow morning at 5:30 am for the hour and a half drive to Davao International Airport. My mother in law and sister in law are flying up to Manila with us to help with the kids and to get a little more bonding time in. We’ll stay in Manila until Wednesday morning, when our flight for JFK.

We had a great time here with the usual ups and downs. The weather was hot and humid but there was an exceptional amount of rain with some flooding in our area, especially last month. I’ve had lots of time to read, think, and spend time with my family.

Our long flight leaves Wednesday morning and 20-something hours later, we arrive at JFK on Wednesday night. I’m usually good on long flight as long as the baby sleeps for a while. I walk the kids around the aisles to stretch our legs and to pass the time on the plane. I’m just hoping I can make the time change quickly when I’m back.

Last week we went to Samal island to swim at the beach. We took a small boat (bangka) ride from Davao to Samal. The ride is about 15 minutes. As you can see the water is very clear at Paradise island Resort. We stayed until noon and went back to Davao where we went to People’s Park for a stroll. We stayed in Davao for the night and then went back to Digos.

I’m trying a new video player for this post. I’m using the same flv video as before but I’m not using the plugin to play the video. I’ll see how this one works.