Home Solar power:
"And so it begins"
After four years of living here at Boo Manor, I've decided that we're going to be here for the long haul, and have started working on some long-term projects for the house. The payoff on these projects is going to be a number of years in the future, but it's time to get started.
First on my list has always been solar power. Ever since I was a kid, I always wanted a solar house. Must have been that book I read in first grade about solar cells; the idea of getting something for nothing was planted in my head. Of course that isn't quite the case (PV systems are expensive) but I still liked the idea.
Well, last winter the power line between the house and the shed shorted out. Replacing the line would probably entail digging up a good chunk of the driveway; a task I really just don't want to deal with. So instead I decided to put a solar power system in the shed to power the lights and my tools. Simple task...
Well, no.
Actually this has been a process. The first step was to install an inverter and batteries, to see if this would even be possible. Being that I had no idea if this was even feasible, I started small: A 600 watt APC UPS with a power cord running to the house. Unplugged the house wire, fired up the UPS...
Well, it sort of worked. However the battery lasted 15 minutes tops. Not unusual, since this was a 6 amp/hr gel cell at 12 volts. So I took the UPS apart, bought a pair of 80amp sealed batteries at a hamfest, hooked it together with speaker wire and hit the switch.
The UPS promptly melted the wires.
Drat.
Fortunately I fused the batteries. If I had not, the wires would have ignited anything near them. Lesson #1 when working with batteries: ALWAYS FUSE EVERYTHING.
The problem was amperage. A 12 volt system takes 10 times the amps to run a 120 volt load. And wires are always rated in amps. A 600 watt load at 110 volts is about 6 amps. Or about 60 amps at 12 volts.
In a situation like this, you have two choices: big big wires or get an inverter that can double the voltage. At 24 volts, a 600 watt load will pull a max of 30 amps, much smaller and easier to deal with.
So I dragged the APC 1200VX UPS out of the house, took it's little (20amp/hr) batteries out and wired it to the 80amp/hr batteries with 6 gauge cable. It works. Runs everything in the shed.
Now to charge the batteries.
In charging the batteries, I needed the panel. So off I went to Atlantic Solar to pick up a PV panel. After some shopping, I went with a Solarex MSX-120 panel (120 watts at 24 volts) and a SunPower 30 amp charger. The charger has a dippy little display, but it's better than nothing.
On Labor day I went up on the roof of the shed, bolted the panel down (facing north; I'll fix that later) connected it to the charger with 20amp Romex cable (hey, it's weatherproof) and fired it all up.
It began to charge. At 3.5 amps peak. At first I thought something was wrong, since 3.5*24 is only about 84 watts. Then I realized that I needed to check the *voltage* off the panels as well as the amperage. The voltage under charge load was 30 at the panels. Thus the panel was pushing 30*3.5=105 watts into the system. Given my inclination, and the fact that the panels are nowhere near aligned with the sun, that's not too bad...
The shed has a lot of shade around it, but I am expecting about 3 hours of morning sun on the panels. 3 hours of sun*100 watts=300 watt/hours a day. My battery pile is 80amps*24 volts or 1920 watt/hours so it should be able to charge the batteries from flat dead in about 7 days.
Not bad. However not great. The big problem here is I seem to get only 3 hours of good sun before the trees cut off the light. And if there is the *slightest* bit of shadow, the panels go from 3.5amps down to 1amp. I'm not sure I will ever get more than this, which means I might be in a bit of a bind. I'll have to think about what the best way might be to power this shed. Maybe I will wind up putting the panel over on the little shed (which might get more sun)
Well, I disconnected the power line this morning. We'll see how it works this week, then I will get up there next weekend and lift the panel off the roof. The system gets absolutely NO afternoon sun, so perhaps I will re-angle the panels to point to the East and let them pick up more of the morning light instead of pointing them due-south. We'll see what happens.
Where next? Read my Solar thoughts page for some future possible plans...