noob questions

[woodall33]

Hi, I am brand new to this forum.  I've always been interested in alternate energy and have read alot of the forum threads here, and will obviously need to read alot more.  I do have a few questions that I have not been able to answer in the posts that I have read.  I'm not anywhere ready to start throwing stuff on the roof, but someday I would like to slowly build a solar project for my home.

1) Do solar panels generally have a "protective" diode already built in?  Or is that something that needs to be wired in downstream from the panel?  I've seen people mention that they have seen some with it built in, but was curious about that.  Or do they use some other sort of protective measure, to keep from any kind of reverse flow back into them?

2) When banking solar panels, as long as they have some kind of protection (i.e...a diode), can you mix/match brands?  It seems that no two brands of panels are really identical(i.e...exact load voltage, current ratings, etc..), so I didn't know how well variety coexists.  Will one try to overrun another?

3) My goal is to one day install a moderate solar system (grid-tie) in hopes to shave a little of my monthly bill.  The bill isn't terrible by any means, but it would be a fun project and if it goes well, I would like to be able to build on it.  I have yet to contact my REA to see if grid-tie is even allowed, but assuming it is, are there certain brands of grid-tie inverters to look for/stay away from?  Aside from the obvious input/output specs, what other things should be considered when looking at inverters?  

4) For the grid-tie inverters, how are they actually wired into the system?  For example, if you have a 32A inverter, does it just use a special 30A breaker in your fuse panel to interface into your existing electrical system?  I've always been curious to the appropriate way that the two systems are actually interfaced inside a home.

5) If the solar system grows large enough to eventually be self-sufficient and is based on a grid-tie design, do you still have the ability to use battery storage (with the grid-tie)?  I'm thinking that early on, if the grid-tie is in place and used as a supplement, in the event of a power outtage, having a battery storage in place would allow me to shut off the unnecessary things and still have power until REA comes back.  Am I just doing wishful thinking with this?

6) And one last question.  In a grid-tie scenerio, if the grid fails and batteries are installed in your home as a storage means, is there a way to automatically stop the outflow into the grid while its down?  I'm thinking along the lines of protection for the linemen who are out working on the lines.  If they think they are working a cold line and the reality is that I'm still cranking out juice upstream at them, well, thats not a good scenerio.  Plus, potentially my neighbors would be pulling down my system hard in a scenerio like that, so are there any automatic disconnects if the grid fails, to isolate me from the real world?  Yes, I could simply go out to the pole and throw the main disconnect, but if I'm not home and the power goes out, then I would prefer to have an automatic feature for that.  

Again, this is a great forum and I've learned quite a bit so far, but am very curious about these few things.  Sorry if any of my questions seem dumb, I simply didn't know the answers to them.  Any and all input is greatly appreciated.  Thanks in advance.

[nanotech]

I can answer #6 for you.

In the situation where the grid power goes out on a grid-tie inverter, it automatically isolates the grid from your system.  That's the main difference between grid-tie and "normal" inverters.  They do two different things than "normal" inverters.  They synchronise your inverter to the grid frequency and they isolate your RE from the grid in case of grid faiure.

[asheets]

for #1... some of the common panels do have a blocking diode, but the common wisdom here is to assume that it isn't there or that it has failed.  Put your own bridge rectifier in the circuit unless your specs are hyper-critical.

[asheets]

For 2, 3, and 4...  I'd recommend starting small, and with some batteries.  Get used to maintaining and building the system 1st.  Start off by powering one or two small subsystems in your home/barn/garage/business before even considering cutting yourself off of the grid or doing grid-tie work.

My current solar setup is simply running my garage and driveway lights, and there's always some little tweak or repair that I'm doing on the weekends.  My wife would kill me if I had to bring down the entire house every time I needed to fiddle with something.  With my setup, she doesn't notice and I get the same valuable experience without much performance pressure.

[kenl]

Question #2 Can you mix and match? Brand names can be mixed. Try to stay around the same voltage for panels wired together in the same system. You could series 2 12v panels and paraell them with 24s but its just easier to to stay around the same volts. Keep in mind that a 12 volt panel puts out more like 16-17 volts peak. Where as 24v panels will put out in the upper 20s to low 30s. kenny

[ghurd]

For #1- Small panels may have a diode built in. It is not the best idea for larger panels, so no 'full sized' PV has them. Any decent controller takes care of it.

For #2- They coexist fine. Having all the same voltage, matched to the battery bank, will be best.  Every 12V battery =~ 17V(peak power) =~ 21V(open).  A 24V PV makes ~41V open.

For #3- Grid tie is a long ways off in your future. If you expect to save any money.

For #4- Pointless question. You can not (legally & here) do it yourself. See #3!

For #5- Thats about right. There are cost issues, ie: replacing a 10,000ah battery bank every so often for 1 hour use per year, and keeping it charged the rest of the 8759 hours.  A 12V 100ah battery will run a cell phone and CFL a LONG time. A 12V 400ah battery will run a radio or TV a long time.

For #6- I believe most larger grid-tie systems have this as an option. Keeping some circuits on, while others are off. Any UL approved grid tie system will have a feature to prevent islanding (killing a lineman or suppling the neighbors with AC).

Two cents.

G-