New Photovoltaic Array

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After rewiring my power center and replacing my batteries, there was only one thing left to do, adding 16 Evergreen EC 110 photovoltaic panels

For years my house has limped by on less than 480Watts of PV panels. This worked when the wind generators were functional, but as the PV panels turned brown, the batteries old, the current array just wasn't big enough.

I also had plans to add a DC refridgerator and DC deep well pump to replace propane powered devices. Because of the difficulty of getting propane delivery for 6 months of the year (winter), and the rising cost of propane, I wanted to switch to an entirely renewable source of energy. This additional heavy DC loads forced me to upgrade to around a 2KW system. Typically winter around here has been tense, with short but cold days. I wanted sufficient power to not worry about the winter months anymore in the slightest.

The concept of adding several racks of photovoltaic panels to the geodesic domes was unpleasant, and would be a nightmare of engineering. Instead I decided to mount them on my 3 car garage, which convieniently is mostly aligned due south, and only 140 feet from the power shed.

I first used my GnuAE program to size the new array properly. I also used my Solar Pathfinder to find the optimal height on the garage roof. It turned out that mounting the panels straddling the roof gave me an extra hour of sunlight per day without removing any trees. At first I wasn;t sure mounting them straddling the roof would work, mostly because the winds here can be fierce at times. It's often averaging around 50mph, and gusting at 80mph more than a few days a year. I finally decided that the leading edge of the panels would be facing mostly into the wind, and added extra diagonal bracing.

Rather than build my own racks, I broke down and bought Uni-Solar racks, which later on I really appreciated. I had decided to use Evergreen 110 watt panels, because they were readily available and use environmentally friendly manufacturing techniques. The hardest part turned out to be putting the footers for the racks on through my shake shingle roof. I had to buy the extra standoff footers from Uni-Solar, since the default ones only work on an regular singles. Then I had to use plumber vent flashing around each foot. Working the flashing under the shingles turned out to be the hardest part. Vent flashing for 1.5 inch pipe also turned out to be very difficult to find, but eventually I managed to order some.

Since the array was going to be 140 feet from the power shed, I wired the panels to produce 48 volts DC, and bought an Outback MX60 charge controller that takes a 60Amp/48VDC input, and puts out 24VDC to my battery bank. I also ran two pairs of AWG #2 wire in parallel, because I needed to keep the voltage drop & voltage loss down below 3%. It's also much easier working with two pairs of AWG #2, than a single thick pair of AWG #01.

I did most of the work over the fall and winter of 2003-2004, a day or two a week till it was done. The most time consuming part was digging the ditch, and mounting the feet for the Uni-Racs. Once the racks were up, it only took an hour or so per rack to get everything mounted and wired up. There is room in the wiring to add more arrays in the future, so I only have to do this project once.


old PV Array Part of the problem with this location is that a flat roof is incredibly stupid when you live at 9000 feet and get many feet of snow. It leaks way more than I would like. Plus the original array of almost 30 year old panels aren't needed now that I have the new array fully operational. It might be nice keeping them for the additional 400 or so watts they still produce, but I'd rather move them to the garage. I left enough room in the wiring calculations for more arrays on the garage roof for this purpose. A future project (probably this summer) is to rip the old array down, and build a false roof over the flat spot to keep snow and rain from collecting and leaking into the house.
long ditch for conduit My son Abel and I dug the 140 foot ditch together through dirt and solid rock. I got to show him some interesting techniques I learned working for the Park Service many years ago for digging through rock with only hand tools. He works with the Boulder County trail crew in the summer, so he's no stranger to breaking rocks.


ditch dug through solid rock We dug through several rocky stretches. One was mostly sandstone. He dug through this by drilling holes with a battery powered drill, and then breaking off big pieces with the digging bar. Luckily PVC bends, at least at this diameter of piping. We found that we could snake the conduit around the worst of the obstacles, and find a somewhat easier path. This one huge rock was the crux, as it was bedrock, but we continued to find a way to wind our way through.


conduit under buried wire Ya gotta love a house built and wired with zero plans... I knew someplace in the yard were the wires from the wind generator, but had no idea where, as I didn't build this place. I knew there were also other potential wiring suprises burid in the yard elsewhere. I decided that because of the rock and the wires, I'd take the time to dig the ditch by hand. Some people go to gyms to work out, I got to break rocks for a month. Anyway, while digging away by hand, found the wind generater wires! As you can tell, they aren't to code, not being deep enough, nor the proper type. I'm planning on replacing them anyway when I get around to replacing or fixing the two dead wind generators.


forest fire beyond garage This is the now empty roof of the garage, with the Overland Forest Fire burning away 2 miles in the background. You can see why the tree cover forced me to mount the panels as high as possible on the roof. I later took the footer part of the belfry off as well, and then covered the hole and reshingled it. This was an interesting day too. While I was running the propane powered generator to fill the cistern, ( I figured a full cistern is good when there is a forest fire nearby) I noticed it had gotten suddenly all quiet... So I walked around back to the power shed, and the generator was on fire! I'm a big believer in fire extinguishers, so I put the fire out, but the generator was now covered in melted plastic and soot. Luckily about this time the wind changed direction, and the fire passed us by about 2-3 miles. I managed to get the generator rebuilt for about $600, but we had to have water delivered to fll the cistern while waiting for parts. There are more pictures of the forest fire here.


belfry coming down To start this project, I had to remove the belfry from the roof, since I wanted to put PV panels there instead. This was a pain in the neck project getting this thing unmounted, and off the roof. I always laugh at how some supposedly electrical projects involve more carpentry than electrical skills. I managed to use a battyer powered saws-all to cut the nails off after prying it up with crowbars. The belfry was pretty heavy, so I lowered it off while repelling down next to it to prevent it from hanging on something.


Eric loading his panels and wind generator I made a large bulk order for several people when I ordered the equipment to keep the costs down. This is my friend Eric loading the panels and wind generator on his trailer for his soon starting house project. (which is fully off-grid, and now mostly done). Eric's got a great story about the power company inspector showing up unannounced, and was going crazy cause he couldn't find the usage meter. When he asked "where's your meter ?", Eric got to reply "There is none!".


PV combiner box This is the begining of the PV combiner box I built. You can buy these preassembled from Xantrex, Outback, or a number of other places. I built my own because I wanted to use an 18x24 inch box so I'd have room for switches in the middle. The switches let me reconfigure the racks to have their power go to the main power shed, or to the garage's seperate power system for the Solar lab.


spools of wire When you're running lots of wire, it helps to keep it organized. This setup worked well for me to make all the wire easily accessible for measuring and cutting.


This is the beginning of mounting the UniRac's to the roof. Since the underground cable was all done, I'd wire up each rack as I got it done, increasing the power for my tiny system as winter was approaching. This shows nicely what the UniRacs look like before mounting panels and in use.


All done! All done! This is the array of 16 panels, all mounted and wired up. I did leave enough room on the roof to add two more racks, one on each side if I need future upgrades. I could also mount another array below the existing one, although it would have problems with tree shading during the winter months.



Copyright 2012 Seneca Software & Solar, Inc