New Photovoltaic Array

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.