Solar Panel Installation

This post is a long time coming. I should have written about this subject over a year ago. Well, better late than never, I suppose.

For the first few months after moving in toward the beginning of May of 2011, we were running off of a battery bank charged every other day by a generator. It worked, but gas sure was expensive. I reckon our gasoline bill just for electricity ran about $150-$200 per month. I ordered and received two 230W solar panels shortly after arriving here, but due to time constraints, it took a while to get them hooked up.

There are not many cleared spots on our property. The area around the house is relatively clear, but there are tall cedar and fir trees very near the house casting shadows on some part of the cleared area at various times throughout the day. The other cleared area is the septic field, but that area is about 250 feet from the house, and running DC wiring that long for a mere 460 (peak rated) watts of power presents a few challenges. Direct current tends to lose voltage over long wiring runs. That can be mitigated somewhat by using larger wiring, but large wiring for that distance gets expensive, almost more than the solar modules in this small setup.

Since we didn't plan to live in our off-grid cabin through the winter just yet (although those plans changed later), I opted for a temporary setup close to the house, and we would just put up with the occasional shadows in the summer time. To keep costs down, I built a simple deck to which rails that support solar modules can be attached. The rails allow the modules to be set at different tilt angles throughout the year as the elevation of the sun changes. With a little help I hand-dug an approximately 18-inch deep trench from the house to the platform about 80 feet away. 2AWG wire was laid from the house to the platform inside schedule 40 non-metallic conduit layed in the trench. A combiner box attached to the platform connects the solar module wiring to the underground wiring through circuit breakers and a lightning arrestor. At the other end, inside the house, the underground wiring attaches to a Morningstar 60 amp MPPT charge controller. This charge controller is overkill for now since we only generate less than 9 amps at about 60 volts, but when we get more modules later, we won't have to upgrade the charge controller. I got this charge controller because it was reasonably priced, could convert high-voltage DC coming from the solar module strings to the 12-volt system already installed in the house as well as 24-volt or 48-volt systems which we might use in the future, and it has an ethernet interface for monitoring over the Internet. Since we planned to be away during the winter, I liked the idea of being able to keep an eye on the battery bank and energy production.

Now that we do live here during the winter, we realize that we are going to have to clear some trees to get some sun with the low sun angle in the wintertime. Also, the panels need to be raised at least six feet off the ground so I don't have to clear away the snow that slides down them all the time.

So how well does this system work, and how much did it cost?
May through August, when the sun is not blocked by trees, it works great. The only time we run the generator is to pump water out of the well into our holding tank and to equalize batteries (a subject for another day), or run a blender or vacuum cleaner, which adds up to may an average of 30 minutes per week. Outside of those months, solar electricity production drops significantly and we run the generator about 2 hours a day to keep the batteries, which are not in good shape, topped off. We run any heavy loads during the second half of the charge cycle so as not to overburden our 3KW generator.

During the winter, the solar panels produce nicely if the snow is kept
clear and the sun actually reaches them. More often than not, though,
it's cloudy in the winter.

Between the charge controller, combiner box, and solar panels, I spent about $1500. The solar panels cost a reasonable $2.25 per watt at the time (retail) though they can be bought for half that or less just one year later. I look forward to expanding the solar array as soon as I can create a permanent place to put them. Wiring and conduit cost about $300 more, plus maybe almost $100 more for blocks, pressure treated lumber, screws, etc. You're probably thinking $2000 is a lot less money than you've read about others spending on a solar setup. Remember, I did not have to purchase batteries or inverter since those were already here when we moved in and those are significant cost items. We do need to replace the batteries soon, though, and we'd like to replace the modified wave inverter with a pure sine wave inverter which will let us run our vacuum cleaner and Vitamix blender without firing up the generator. (Some motors and dimmer switches have problems with modified sine wave inverters.) If I would have knowm how much gas we would have saved those first few months I would have increased the priority for this project.