August 11, 2010 at 7:27 pm | Solar Cell Company
- Posted by admin | 3 Comments
Without permission from the power company? I know it’s probably illegal, but Arkansas has the worst rules regarding this and it’s not worth it to do it legally because they make you pay for a special meter, plus additional monthly charges, and then they pay you nearly nothing for any power you send back to the grid. So it’s pretty clear that they don’t want you to do it. What I want to do is set up PV solar cells to produce about 1 kW max, then just hook this into my system in parallel. This will (I reckon) offset some of my consumption during the day, and also give me something to run my refrigerator, freezer, and well pump (one at a time) when the power goes out, which it frequently does in this remote location.
I am also a small worried about undervoltage on these appliances. Will I need UV protection breakers for them? (expensive) And what happens if I am not consuming enough of the solar production? Will something burn out, or will voltage go too high? I know how voltage regulators work on mechanical generators, but have no thought what is going on with solar panels.
Yeah, I am an engineer so don’t assume that I’m stupid. I am just ignorant about solar cells and electronic power inverters.
OK, this really helps. I really wanted to avoid having a battery bank though, because it’s expensive and troublesome to maintain. I may be better off to just get a small gasoline-powered generator for emergencies.
I hadn’t considered synchronization, as the power supply is only single-phase 220v. I now see, but, that there would be a frequency difference between my output and right sinusoidal 60 hz power. (I’m familiar with synchronization of 3 phase power systems, but not this.) Thanks, guys.
First of all, solar cells produce low voltage DC, so you need batteries to store the DC, a charge controller to control the charging, and, most vital, a excellent sine output inverter. The output from solar arrays varies all over the place so the charge controller and batteries are needed to control that. The inverter will shut down if the current goes too high, or the input voltage goes outside of specs. so you don’t need any UV protection.
The inverter generates the 120 volts 60Hz you need if you are in the US.
But you cannot connect the inverter output to your power lines, you will burn out the inverter or get the power company very upset. AC voltages don’t add. They will be at two slightly different frequencies, and the voltage will add and subtract as the phase changes. You will get high currents into or out of the inverter or into or out of the AC mains. Something burns out quickly.
You need a special switch that disconnects the AC mains and connects your inverter output. You can do this for the entire house or a part you select.
Or you need a special inverter that synchronizes with the power company frequency and phase, but you need the permission of the power company to do that, plus a special meter, as sometimes power will flow back into the meter.
Or, for small scale, just an outlet strip plugged into the inverter, into which you can plug your appliances when power goes out.
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