Solar Cell connection to grid
 

I am interested in building solar panels. I would like to connect them to my electric panel. I know when you run a generator you have to keep the generator power seperate from the line power. How can you connect the power from the solar cells to the panel. Will there not be a problem with power coming in from another source?

Thank for response,
Rox

Line power = AC
solar panel power = DC
AC ≠ DC

[quote=Roxelectric;307033]I am interested in building solar panels. I would like to connect them to my electric panel. I know when you run a generator you have to keep the generator power seperate from the line power. How can you connect the power from the solar cells to the panel. Will there not be a problem with power coming in from another source?

Thank for response,
Rox

Solar panel would go through an inverter before going to the panel.
Rox

PaliBob,
Thanks for your response.
Rox

Like mentioned you'll want an inverter for this. You may also want to setup a battery bank as I'm not sure how good solar panels are current wise. Also to connect to the grid you'd need to somehow make sure the inverted AC phase is 100% in sync with the incoming power service. So lets assume you have 120v AC coming out of your inverter you'll want to connect the same poles together.

This is called "Net Metering".

You would use a "Grid Tie Inverter".

Like these (Single Phase 60 Hz in U.S.)...
http://www.xantrex.com/web/id/13/type.asp

Grid-interactive inverters are readily available. The DC side connects to the solar panels, and the AC side connects to the electrical panel. These are permanent connections.

When the solar panels receive enough sunlight to be effective, the inverter makes AC out of the DC, and synchronizes its output to the electrical panel. It then backfeeds everything the solar panels can produce into the grid. Most of them even adjust the DC input for the maximum solar panel efficiency. Typical DC voltages range from about 200 to about 600.

In the event of a grid power failure, the inverter automatically shuts down. Thus, no power is backfed into a dead power line. After grid power is restored, it'll wait about 5 minutes, then begin backfeeding again.

Most utilities require the inverters to be UL listed and IEEE 929 approved. I've yet to see a grid-interactive inverter that didn't meet both of these. They also require a lockable disconnect somewhere near their meter.

You'll need approval from the local utility for this type of installation. A solar system is a generating station, and each system must be commissioned by the serving utility. This is federal law, not state or local. Most utilities require a building permit for the installation. This can be a very simple process, or an absolute roadblock. Most larger building departments are well versed in these installations, and very easy to deal with. Some of the smaller ones haven't a clue, and are more obstructionist gestapos than anything else. Like the one where I live.

Ask your local utility about 'net metering'. This is where your system basically turns your meter backward when its generating, and the meter turns forward at night. Most utilities have such a program, but it varies state to state. Some states offer rebates based on the actual output of the system.

Rob

I believe the way the law is worded, if the inverter is UL listed, the Utility cannot require an engineering analysis of the unit.....it is assumed to meet all requirements. If you put the system together yourself, the Utility can rightly require you to prove that it will meet all the standards on islanding, frequency, overload protection, harmonic distortion, etc.