Monday, November 2, 2009

Shopping and redesign

There is an upside, and a downside to doing major work on your own house.

The upside, is that after you get an initial price for materials, you can continue shopping for a better price, on better materials, until you actually have to order the materials.

The downside, is that until you order a particular item, you may have to keep redesigning other elements as you change which item you are ordering.

My choice of solar panel may have changed 3 times in the last 3 days!!

I said in one of my first posts, that I was designing a system to generate my own power from sunlight. The primary element in a system like this is what is called a photovoltaic panel or module. Its job is to sit out in the sun, and soak up sunlight and produce electricity. It should do this for the next 25 to 30 years, or longer. It has no moving parts, makes no noise, and in my case will sit on a rack out in the field behind my house.

So, I have about 15 companies bookmarked in my browser, who sell components that I will need to build the system that will generate my electricity, including photovoltaic modules. I have been watching to see which modules would give me the most power for the least cost. I had designed the system to utilize 18 modules made by Kyocera. Each of the modules I chose will theoretically generate 205 watts under bright sun. Then things changed...

Oh, how much electricity is that you ask? Well, 205 watts would be enough to light up a couple hundred watt bulbs which you might use for areas where you want a lot of light. Or, it would be somewhat more than what 3 60 watt bulbs would need, the sort of bulb typically used in a hall light, or a table lamp. The entire array was going to have 18 of these modules, and generate 18x205 watts at maximum, or 3690 watts. If you have an electric water heater, it probably uses more than that. The burners on an electric stove can use more than that. A hair dryer on high may use almost half of that. The modules aren't expected to provide all the power the house will need, all the time. They convert energy from the sunlight into electricity, and that energy is stored in batteries to be used when needed. If used effectively and efficiently, you can do a lot with that size array.

Now the modules aren't going to just sit on the ground. They need to face so they get hit by as much sunlight as possible. To do that, they will face toward the south (since I am in the northern hemisphere), and I will put them at an angle that will try to maximize the energy that I can use. If I was connected to a utility, I could use the utility as a battery, and try to generate as much electricity as I could throughout the year. So, I would angle the modules to they can take full advantage of the bright and long hours of sun in the summer. Since I am using batteries, I can only store a small amount of electricity for a short time. Therefore, I want to generate it close to when I will need to use it. This means that during the short days of winter, with the sun lower on the horizon, I want to get as much out of the limited sunlight as I can. So I will tilt the modules at a high angle. Much higher than a normal roof pitch, more like the roof pitch on an A frame house. I am the solar contractor, I am designing and buying or building everything. I needed racks to mount the panels on. My dad and I had worked out a design, and we built a prototype.

Now it was time to order the rest of the materials for the racks. However, some of the measurements for the racks will be determined by which modules I buy. So I went and looked to determine if the ones I had selected were the ones I really wanted to use. I found where I could get some other modules for a significantly lower price for the amount of power they would generate. They would generate 225 watts each, and so for a similar amount of power, I would only need 16 modules, and they were less expensive per module than the Kyocera modules I had been planning to use.

I ordered the modules this morning. The company sent me an email confirming my order, and the credit card company, indicated a pending charge on my credit card. So I went and ordered the materials for building the racks, and ordered enough to build the 7 remaining racks I would need. Everything was going smoothly.

Then I checked my email this evening. They indicated that there was a problem, and they had refunded the charge on my credit card. Of course by the time I checked the email, they were closed. So I couldn't get this straightened out today. I decided to take one more look at what other solar modules were available at the various companies I had bookmarked. As I was looking through the products, I spotted one which looked strange. It was a huge price on a module. This didn't make sense, so I clicked on the listing to see if it was just a typo. It turns out that the listing was for 20 panels, not one. From the write up, the price apparently includes the shipping, and is about half of what I was originally going to pay for the 18 Kyocera modules! However, I can't just order it on the website, I will have to call them. So, I have my fingers crossed, if this works out, it could cut a large amount off the cost of my solar modules. It will however entail another redesign of some of the wiring, as the modules will need to be hooked up differently than I was planning, and I will have to order material for another 2 racks.

Ah, the fun of redesign

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