Newbie with inverter help!

[propeller]

Hey everybody!

Quick brief on my solar experience:
I am an electrical engineering major trying to get some hand on experience as I had trouble finding useful related projects at school. I'm also in the process of founding a club with related sustainable ideas as well, but I need help on my first solar panel.

Situation:
I have 48 photo-voltaic cells, the ones that are rectangles with 2 contact strips on them. Any ways my solar panel is arranged so that there are 6 rows with 8 cells per row.
Right now if I follow one of the two sides all the way through the 6 rows I get a steady 26 volts at 4 amps. Making the total 52 volts x 4 amps = 208 watts (in direct sunlight). I'm not sure if I combined those right btw. If anybody knows please tell me. (if I should add the volts but not amps or vice versa or whatever?) Anyways I'm wondering if there is a better way I could arrange the rows to work better with an inverter and/or what type of inverter should I use?

Thanks for anything!
-Adam

[Sunking]

Situation:
I have 48 photo-voltaic cells, the ones that are rectangles with 2 contact strips on them. Any ways my solar panel is arranged so that there are 6 rows with 8 cells per row.
Right now if I follow one of the two sides all the way through the 6 rows I get a steady 26 volts at 4 amps. Making the total 52 volts x 4 amps = 208 watts (in direct sunlight). I'm not sure if I combined those right btw. If anybody knows please tell me. (if I should add the volts but not amps or vice versa or whatever?)

Series voltage adds, current remains the same.
Parallel current adds, voltage remains the same.
Series or parallel power adds.

The voltage you end up with is really based on what the application of the panel will be used for like a grid tied system, off grid battery system, or a special application. For example if it is designed for a 12 volt battery system, then you will use 36 cells in series so the operating voltage at maximum power (Vmp) equal approximately 18 volts.

For grid tied systems, there is no real set voltage. Grid tied systems operate at much higher voltages so you are not chained to 36 cells in series for 18 volt output. Typically the Vmp of grid tied panels run between 24 to 50 volts, and even higher. So 48 to 100 cells in series with anything in between and even higher. If one single series does not obtain the power objective, you add another series string in parallel. Today about the largest panel is around 240 watts. Any larger and the panel becomes to physically large and heavy to handle, or withstand the mechanical stresses out in the elements.

[russ]

Welcome to Soalr Panel Talk Propeller,

Good luck with your project and the club. As Sunking has already shown you, the other members are ready to help out as best they can.

Russ

[propeller]

ok that's what I thought about the series and parallel. I've gone through my first year so mostly GEC's plus a lot of math and some physics, no engineering classes yet though.

anyways I was thinking if instead of 6 rows in series I could do 4 parallel sets by having each side of the contact strips followed through 3 rows. This would make it run at 13 volts (a lot closer to 12 but idk if it's close enough) and 16 amps.

I know it makes it more inconvenient that I have 48 instead of 36, that's just the deal I got on ebay and so I made use of all I had.

What my hopes are is that I can just be able to hook up the solar panel to a nice 160 watt AC stereo or something so we can have that on display at our booth at the student involvement fair. Eventually it may end up being grid tied and we might also rig it to track the sun, but for now I just need to find the best way to connect it to an inverter safely. I already killed a boombox with it!

[Sunking]

Eventually it may end up being grid tied and we might also rig it to track the sun, but for now I just need to find the best way to connect it to an inverter safely. I already killed a boombox with it!

Nah that is not going to happen. You cannot use DIY stuff on grid tied applications or part of your home wiring. Unless your name is Mr. UL Certified.

[propeller]

Understood, but aside from connecting it to the grid is there any advice on if what I suggested about the 13 V circuit? Also I'm having trouble figuring out if 16 amps is okay to go straight into an inverter. Thanks!

[Sunking]

Understood, but aside from connecting it to the grid is there any advice on if what I suggested about the 13 V circuit? Also I'm having trouble figuring out if 16 amps is okay to go straight into an inverter. Thanks!

Well since you are a student with no training right now, you may not understand what I am going to say.

A solar panel is not as power source like a battery or generator, they are current sources. Current sources are used to operate into a resistance with a narrow dynamic range. So in general you cannot use a solar panel to power a DC device directly, you have to have a buffer like a battery.

If you go look at any solar panel spec made for any 12 volt system you are going to notice a few very important specs called:

Voc = Voltage open circuit = around 22 volts.
Vmp = Voltage @ maximum power = around 16 to 18 volts.
Imp = Current @ maximum power = dependent on the power output of the panel in watts.
Isc = Current short circuit = roughly 5% more than Imp.

They will also show you a graph of current vs voltage with varying degrees of solar insolation.

So what all this means if you were to hook up say a 200 watt solar panel to say a boom box stereo, the output voltage will vary from 0 to 22 volts. It is not going to work very good if even at all.

To make it work you have to insert a voltage/current regulator (aka charge controller) and battery between the solar panel and device under load to regulate, store, and buffer the current source to match the power requirements of the device under load.

Ok as for the size of a panel to work on a 12 volt system you have physical limitations of physical size. To date the largest you can buy commercially is around 150 watts. Put that into spec and you get

Voc = 22 volts
Vmp = 17 volts
Imp = 8.8 amps
Isc = 9.3 amps
Width = 26 inches
Length = 60 inches
Weight = 40 pounds
Number of cells = 36
Type = mono crystalline.

[propeller]

Ok, that kind of helps. Still a little confused on some things:
1.
I found some 200 watt inverters online for cheap, that take in 12V, which means about 16.7 amps, and convert that to 120V AC. To me that sounds perfect because I'll have a max of 13 V at 16 amps, but maybe there's a reason why you didn't suggest that.
2.
With the charge controller if I understand correctly, you're saying I need the power going from the solar panel to a charge controller, then a battery, and then an inverter?
3.
If the above inverter isn't any considerable option is there anything I can do besides removing 12 cells from the panel?

Thanks again you really are helping me figure all this out!