soldering work station notes

Hi, today I'm going to make some notes on my workstation area, so anyone trying to follow along at home won't make the same mistakes I did. First, we'll talk about strategy a bit, and prep work; this is important, in order to limit the time the soldering gun is actually on, causing a burn risk in your house.

Wire use strategy
I actually cut out 3"x6" card stock, and taped a bunch of paper tabbing wire to it, in a dry run, and made the following determinations for my 6 cell by 6 cell configuration, there will be 6 cells with positive wires sticking out half an inch, and 6 cells with negative wires sticking out half an inch. That left 24 cells with a 'normal' wiring, so before I laid even one cell on the panel, I would need the following for each panel

6 cells wired on just the negative side, with tabbed wires sticking out just long enough to connect to the bus (roughly 3 3/8 in).
6 cells wired on the positive side with tabbed wires sticking out 1/2 inch, and 'regular length' wires on the negative side. (roughly 2 7/16 in)
24 cells with 'regular length' wires on the positive side. (roughly 6 1/16 in)

I wanted to do both panels at once, so multiply the above number by 2, and pre-cut all my tabs
24x3 3/8" tabbed wires
24x2 7/16" tabbed wires
96x6 1/16" tabbed wires

Once that was done, I set up my work area with a flux pen, solder and the cheapest 30 watt soldering gun that is sold at Radio Shack. The tabbed wire is pre-coated with solder, and over time as my technique got better, I was able to complete the connection without using my roll of solder, but in the beginning, a little solder helped a lot.

MISTAKES I MADE
1. Always use the flux pen, otherwise the wires will pop off really easily.
2. I used a felt-covered table, and cracked a cell pressing down too hard, as the cell flexed inward. I switched to a flat table, covered with a thin cloth to prevent scratches, and that worked really well.

doing all the work of tabbing the cells took about 10 hours, spread across 3 days. All that's left is to attach the cells to each other within the solar panel, which I have yet to modify, since the 3-inch by 6-inch measurement was inaccurate. I plan on doing that tomorrow evening (meeting with the district manager of USSD this evening, on continued plans to become a sensei -- they typically charge $8000 for 'instructor school'), completing the solar panel Friday evening, and actually exposing it to the sun on Saturday..

Here's a link to a nice diy solar website

Hi. http://www.hotsolarenergyfacts.com/green-energy/simple-steps-to-powering-your-residence-with-home-made-solar-power. This is a nice 'overview' site, that pretty much covers what I'm doing. I think that some pictures would be helpful, but besides that, it's a pretty nice description.

pics of solar panel elements

I don't have the grid-tie inverter or plexiglass to cover the panels, but here's the rest of the components. Where I thought it was useful, I put a measuring device, such as a ruler or a t-square, so you could see the dimensions of the objects.


Here is the tabbing wire, which I solder to the back of each cell.

Here's the front/back of the same cell, you can see how I have soldered the tabbed wire to 6 points on the back. When they are attached, the wires will go from the back(positive side) of this cell to the front (negative side) of the cell below. They will end up in a grid of 6 by 6, for 36 cells, measuring roughly 19 inches by 38 inches.


Below is a stack of 35 cells, so you can see the thickness. the stack behind it only contains 24 cells, but they are all tabbed, increasing the thickness.















Here's the 'raw' panel, which will be changing a bit, but you can see that it's build to hold 3 solar arrays at 6x6 cells, of 37"x19", roughly 37"x61" total.




So that's all but the kill a watt power measuring device, which will be included in the next post, as well as the grid-tie inverter.

Solar Cells +other stuff arrived

Hey, so my solar cells showed up at the end of last week, and the first thing I did was confirm the measurement. Bad news, they are labelled as '3x6 inches', but they aren't. The size is actually 3 and 3/16 by 5 7/8. I actually pre-built the panel to be the correct size, based on an accurate cell size, so needless to say, some re-engineering is taking place. Besides that, everything is going swimmingly; The cells I bought came 'untabbed', meaning no tabbed wire has been attached to them, so I began soldering late on Sunday. After about 5 hours, I'd say I'm half done with the tabbing efforts, and expect to be able to place the cells sometime around the end of the week (after the redesign of the solar panel itself). Also, the cells themselves are super-thin; to give you an idea of how thin, a stack of 40 cells is about 1/2 inch in height. So the math says the cell is each cell is 1/80 of an inch in fractions, or .0125 inches in decimals. Soldering them together is definitely a difficult task, and I'm a little worried that some of them are flawed, as just touching the soldering gun to one caused it to crack from the heat.

I also have been able to mess around with the 'Kill a Watt' power reader ($9.99+shipping and handling on ebay seems to be a typical lower-end price), and came up with some interesting numbers. My laptop takes up about 40 watts of electricity, while the desktop is at around 150 watts. I haven't done the math, but perhaps from an electricity-usage standpoint, laptops could be cheaper than desktops. Some stats from around the house:

Microwave uses 1300 watts
Vacuum uses about 1000-1200, depending on whether the brush is running.
Wife's computer uses about 130 watts.
I can't measure the clothes dryer, as it's a 240 volt appliance, but the heating coil has the number '5400 watts' on the side, which is probably a good clue.

I also took some readings on the various items with standby lights in the house, such as the phone charging stand, the charger for AA and AAA batteries for the kids' various video game controllers. None of the devices with red lights on them took enough power to actually register on my meter, so less than 1 watt. I actually found one that was labelled ( the kids' bathroom led night light), and it said .3 watts. Multiplying that by 24 hours, 30 days, it consumes 216 watts a month. there are around 20 devices with little lights on the front, so assuming they all use this amount, I'm consuming about 2 kilowatt-hours of electricity per month running standby lights. At 10 cents a kilowatt-hour, that's roughly 40 cents. So that's good to know, and it puts my mind at ease on what power is being consumed by what objects. It's strange, because when I touch the block of a power supply on these items, it's typically hot to the touch, which makes me think 'huge energy use', but it turns out this is just a perception, not a reality.

At this point, it seems that the most efficient thing to do would be to abandon the solar photovoltaic array, and put up a clothesline in the back yard, so that we could stop running the dryer so much. It costs us 54 cents in electricity every time we run the thing for an hour.


Anyway, the next 3 days will be busy, between karate class, work load, and more karate (I got invited to try out the karate teaching school for a couple of hours on Tuesday, which I'm super-pumped about). I'm hopefully going to finish the pre-soldering after karate on these days, and get the panels mounted on Thursday, or at least that's my hope, so there may not be another post until Friday, as there won't be much to add. Maybe I'll do a 'pictures' post tonight, to show the components.

Solar energy -- the math

Here's a link that explains the math, and keeps me from just plagiarizing what is already out there.

greenecon.net

OK, so as my last post revealed, I'm going to attempt to create solar panels from scratch. This is kind of a neat engineering problem, where I have to address the following questions:

1. How do I protect the solar cells while still exposing them to the sky? What about hail? How much reinforcement do I need if 2 feet of snow falls on them?

2. How do I attach them to my roof? Or would ground-level poles be better?

3. How big should the final system be?

4. What is the best wattage/voltage for the panels to run at?

5. how big should the panels be?

6. How much heat are they going to generate, and if I build the panels from wood, will I end up starting a fire on my roof?

7. Is it better to put more panels up, mounted flat to the roof, or to use less panels, and mount them at a sharper angle? What kind of extra reinforcement will I need to deal with wind, if I mount the panels at an angle.

So, to help answer these questions, I have looked at a lot of websites, watched a bunch of youtube videos, and really haven't come up with a lot of answers. The main thing is to avoid over-engineering this project, and paying way more than I should. So what I've done is ordered a enough supplies on Ebay to build a single panel, at 129 watts, and 18 volts, along with a simple grid-tie inverter that plugs directly into a wall socket, and a 'kill a watt' power meter to monitor what amount of electricity is generated. The shopping list so far?

$99.99 for a 300 watt grid tie inverter, rated for an input of 14-28 volts
$138 for 72 1.8watt, 0.5 volt solar cells plus miscellaneous parts to attach them to each other
$21.99 for a sheet of plywood to mount the panels to.

So, the math on the solar panels is like this:
I'm building 2 mini-panels of 36 cells connected in parallel, which gives us 18 volts (0.5*36), and 64.8 watts (1.8*36) I can then connect those 2 panels in series, to keep the volts steady, but push the amps up, essentially to stay under the 28 volt limit on the inverter.

I'll add some pics once they arrive, and once the panel is built, so that its construction will become clearer. The construction of the actual panels will probably require about 50 hours of soldering/building time, so I'm imagining getting the panel into operation about mid-April.

solar Cells, how do they work

OK, I spent days learning about solar cells, to get to the point where they actually made some sense, mostly because I didn't get a basic concept. The cells themselves are all about surface area, and they are about as simple in construction as it is possible to be. The entire front of the cell is the 'positive side' and the entire back of the cell is the 'negative side'. So if I take a solar cell out of its package, drag it into the sunlight, and touch the positive probe from my multimeter to anywhere on the front, and my negative probe to anywhere on the back, I can get the voltage of that cell. The cells that I ordered have 2 parallel stripes down the front, where I can solder the tabbing wire (a special thin, flat wire that will lie flat under the cell), and there are 6 solder points on the back (little squares of pre-applied solder, I believe) 3 on each side line up with the parallel stripe on the front. So if I were to connect 5 cells together, the first cell's positive wire would be connected to nothing (later on, it connects to the positive terminal on whatever we are powering) The negative side will be soldered to the positive on cell 2. The negative side on cell 2 will be soldered to the positive side on cell 3 and so on, until cell 5 where the negative wires will be nothing, to form the negative terminal to whatever we are powering.

So, to design my panels, I had to understand parallel and series wiring. Read below, or visit the wikipedia entry.

The first is wiring in series. If you connect several cells, + to -, then the voltage goes up while the current stays steady. For example, if connect 10 cells together, in series (cell 1 negative terminal connects to cell 2 positive terminal. Cell 2 negative terminal connects to cell 3 positive terminal and so on), and each has a voltage of .5, this means you will get 5 volts (10*.5 volts) out of the cells. I actually tested this out, by taking 6 AA batteries, and lining them up, positive to negative. Each one is rated at 1.2 volts, but in actuality produces 1.4-1.5 volts fully charged (there are electronic rules that tell us that when we place the batteries under 'load' this will drop to 1.2, so this is actually a proper voltage reading). The voltage reading was 7.8, so the 'series' wiring was proven out. This is called wiring in series. Incidentally, this explains why, if you are jump-starting your friend's car, and connect positive to negative, instead of positive to positive, you blow up both your electrical systems. Doing so essentially drops 24 volts through both cars, frying everything in sight.

Second is wiring in parallel. When we do this, the current increases, while voltage stays the same. In this case, we are connecting the leads from positive to positive. in the car battery example, the voltage will end up being 12 volts, while the wattage is the sum of the 2 batteries' wattage.

These 2 concepts are important to understand, because the solar panel has to be of a sufficient voltage and wattage to run the grid tie inverter, which will be explained in a later post.

I'll get through a couple more 'concept' posts, then start posting pictures of what I've done. I'll also post cost information, as well as establish some baseline of what the break-even point is on a photovoltaic system.

Solar array DIY stuff

Hey, I've started up a new hobby; I'm going to be attempting to create a home-built photovoltaic solar panel system for my home. I've been watching prices for commercial solar installations for years, and the price has never been right. The cheapest system I've seen was $13,000, with about a 25 year payback period, which is just far too long. But then I got the idea to search ebay for the components of a solar array, and found that the price dropped pretty significantly. So I ordered some 'solar cells, similar to this ebay item. The trade-off in building your own photovoltaic system is, number one, the learning curve, and number 2, there is a LOT of soldering work. So my plan is to build a couple of panels as a test case, mount them on my roof, and then share the results. If it's a big failure, I'll post my mistakes here, and whatever I learn, I'll share that as well. Thanks, more posts coming soon.