Exciting news, people: for the past couple of weeks, we've been spending most of our spare time on our solar electric project! The pipes, rebar and conduit for the two pole mounts (which will each hold 4 solar panels) are in place; the next thing is to pour the concrete that will anchor the poles. Once the concrete is cured, the next thing will be assembling the frames that hold the solar panels, and installing the panels themselves.
We've been planning for this and organizing this project for a long time, certainly since before we moved to the farm five years ago. A lot of thought went into sizing the system; that is, figuring out how much power we wanted to produce, and from there, choosing the best combination of components to produce that power. No doubt about it, the equipment is expensive, and we didn't want the setup to be bigger than we actually need; frankly, that's just wasteful. On the other hand, we also planned for the addition of hydroelectric power to the system at some point.
Several months back, after burying my head in manuals and studying wiring schematics, I assembled the main power panel. This impressive setup includes two 3.6 kW inverters, a 240-volt transformer, a DC disconnect panel, an AC breaker box, and an 80-amp charge controller. I also built a large wooden box to house our bank of 16 deep-cycle batteries. Before we started working on all this, I really didn't know much of anything about house wiring (or electricity in general, for that matter). I was a bit intimidated at first, but eventually decided I should just dive in and start learning. After all, we're the ones who will be using this system, so I figure I ought to have at least some understanding of how it all works.
Here's the overview: The solar (photovoltaic) panels convert sunlight to electricity. Cables run from each panel, or series of panels, to a combiner box. This box contains breakers and terminal bus bars, to which the cables are connected. Larger cables then carry the combined power from all panels to the charge controller, which in turn carries power to the battery bank. As the name suggests, the charge controller controls the charging of the batteries, partly to prevent overcharging. It is basically the brains of the system.
The 16 6-volt batteries will be wired in two series of 8 batteries each, as we are building a 48-volt system. Very large cables, one positive and one negative from each series, then carry the battery (DC) power to the DC disconnect breaker, and from there to the inverters. The inverters then convert the DC power to AC, and more cables carry this power to the AC breaker box and out to the main house wiring.
Oh, and there will also be wiring from the generator to the AC box; the system is programmed to automatically start the generator to charge the batteries, if the level of charge drops below a designated point.
Pretty simple, isn't it?
Actually, there is a lot of detail in every part of this project. We've invested a lot in all this, one way and another, and we are taking things fairly slowly at this point; it's worth double- and triple-checking to make sure we've done it right the first time. It's very interesting and sophisticated equipment, and we're fairly thrilled that after all the planning, it's finally all coming together.
Be sure to check back; I'll be posting more soon, along with photos.