Solar help

[Domeguy]

You determine what size wire to use after you know what size panel you are going to use and know the total watts and amperage they will kick out. You also need to know how long the wire will need to run. You can then cheat and use charts like this.
[IMG][/IMG]

If you needed 6 amps, and the wire run distance was 42 feet, in order to get a 2% voltage drop! you would use a #8 wire.
For anyone who is interested in learning about solar installation, I highly recommend this book. It explains everything in easy to understand language. It is the book I always reach for when I need to check something.
"Photovoltaics Design & Installation Manual" put out by Solar Energy International. Published by New Society Publishers. Their phone # 1-800-567-6772 , and they are based out of Canada.
[IMG][/IMG]

[jamesneuen]

Ok so it's like with batteries to get higher amps or volts. If similar panels output all 12 volt, will the size determine the amperage?

Sorry to beat a dead horse.

[jamesneuen]

I'll have to get a few books I think. Or maybe buy an electrician a few beers

[Domeguy]

On the back of every panel, usually near the wiring hookup junction box will be a sticker with all the information of the panel on it. It will look like this.

[IMG][/IMG].

I copied this from the web so I don't have to type it all.



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11-23-2008, 12:53 PM #1
ASUgrad
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Nov 2008
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Solar Panel Hookup. Series or Parallel?
Hi, I was wondering what would be the best way to hook up a solar panel system for maximum production. From what I understand it comes down to either series or parallel. Thank you.

Jackie
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11-24-2008, 10:00 PM #2
SolarGuy
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Oct 2008
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Re: Solar Panel Hookup. Series or Parallel?
Hello Jackie and thanks for joining Solar Panel Talk. I'll explain briefly what the two mean.

Series wiring is when you connect a positive terminal from one solar panel and connect it to the negative of another. Doing this will result in higher voltage (the sum of voltage from the panels) while the amps stay the same.

Parallel wiring is when you connect a positive with a positive and a negative to a negative. When you do this the voltage remains the same, meanwhile the you get higher amps. So two 12 volt/3.5 amp panels hooked up in parallel would output 12 volts at 7 amps. Four panels hooked together would produce 12 volts at 14 amps and so on.

Hopefully that will help you in deciding which way you want to hook them up.
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12-13-2008, 02:11 PM #3
D_Robbins
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so why would you want more voltage compared to amps and vice versa?
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02-02-2009, 10:04 AM #4
Greg
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Series or parallel
Just to see this clearly....sorry to be a bit thick.....but does this mean one runs series to charge batteries, and parallel to run appliances directly?
Thanks J.SUN
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02-03-2009, 06:39 PM #5
solar_geoff
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Your module and inverter combination dictates how you should wire everything. These modules wired in series are called "strings." The number of modules per string is dictated by your inverter operating voltage window. For example, SMA inverters have a DC voltage window of between 250-600V. Your maximum number of modules per string is controlled by the module open circuit voltage (Voc) adjusted for your lowest record temperature (600v/Voc x NEC 690.7 correction factor). The minimum number of modules per string is controlled by the module max power voltage (Vmp) adjusted for your hottest record temperature. The Voc and Vmp correction factors are found on the module data sheet.

It is always good practice to add 10-20% to your turn-on voltage to account for the drop in output that the modules will experience over 20-30 years (usually 10-20%).


Once you have determined your number of modules per string, you then add strings in parallel. You do not want to add to many strings because your inverter can only produce power up to it's nameplate wattage (with a few exceptions). Basically you want to make sure your AC wattage is as close to your inverter rating as possible, so that you are not paying for DC watts not converted to AC electricity. It will not, however, damage the inverter to exceed its maximum usable current. You could have 1000 strings wired to a 2000w inverter and not damage it, as long as your number of modules per string falls into the inverter DC operating voltage range. The reason for this is that the inverter is able to "throttle" the current flowing through it with capacitors. Any power in excess of the inverter's capacity is simply not created.

To determine your AC wattage: (#modules)x(module PTC wattage)x(inverter efficiency)

Whew!
End copy!

Now refer to the above picture from my previous posting with 2.4 series and parallel circuits in power sources. Look at figure 2-2. Each panel will put out 12VDC and 3A. It shows 2 panels hooked up in series. The voltage now will be 24V but the amps will stay at 3A. 3 panels together in series would make it 36V, 4 panels would make 48V, but the amps will still be 3A.

In figure 2-3, the same 2 panels are wired in parallel. The output now is 12V, but the amperage now is 6A. Add a third panel and you will have 9A, add a 4th panel, you will have 12A, but the voltage will still stay at 12 volts.

Solar panels wired in series will increase the voltage, but the amperage will stay the same.
Solar panels wired in parallel will increase the amperage, but the voltage will stay the same.

[jamesneuen]

Oooooo that I can understand. But will 12 volts at 6 amps transfer the same amount of power as 24 volts at 3?

[Domeguy]

Sorry, but no. Let's go to the definition of what volts, watts, resistance, and amps are:
Voltage: the electrical pressure that forces electrons to flow. Voltage is sometimes called electromotive force.
Watts: A watt is a unit of measurement of electrical power. 746 watts is equal to 1 horsepower.
Ampere: the rate of flow of electrons through a circuit. One ampere is equal to the flow of 1 coulomb (628 X 10 to the 16 power, or 10 with 16 zeros electrons) per second.
Resistance: the opposition to current flow of electrons. A unit of measurement of resistance is the ohm.
So let's make a small model. Think of a house in a valley. The house get it's water from a water tank next to the house by way of a direct pipe to the tank. The house has a sink, and the sink has a faucet. Depending on how much water is in the tank determines how much water pressure comes out of the faucet. If the tank is full, the pressure will be high. If the tank is low, the pressure will be low. Now think of the tank as the power source, and the pipe as the amperage, and faucet as the watts, and a leak in the pipe as resistance. If you increase the amount of water in the tank, or voltage, the amount of water coming through the pipe is determined by the size of the pipe, so to increase the amount of water, or amperage, you need to increase the size of the pipe. Once you get the amount of water flowing through the pipe you want, you can open the faucet to get you correct amount of water, or watts. I hope this makes any sense.

[jamesneuen]

But by that reasoning a 2 inch pipe flowing at 60 psi would generate the same water at the end result as 4 inch pipe at 30. The only difference is the faucet/watts and the hole/resistance.

I think I just need to take some electrical classes because my brain is starting to hurt. lol.

Thank you for trying to help and I do understand a few things better but I don't really have a knowledge base to start it on for deeper understanding.

[Domeguy]

As I stated in the beginning, I am in no way an expert, and it may have forgotten more than I learned over 5 years ago. I may not have expressed that analogy correctly as I was trying to remember how an instructor explained it to us, and I may have gotten a bit of it wrong. But I can't stress enough what help a GOOD book on solar power is. And I can guarantee the photovoltaic book I mention above, and here again.

Photovoltaics Design and Installation Manual
Published by New Society Publishers
P O Box 189. Or. Solar Energy International
Gabriola Island, BC. PO Box 715
V0R 1x0, Canada. Carbondale, CO. 81623-0715
1-800-567-6772. 970-963-8855
www.new society.com. www.solarenergy.org

You can get it from the publisher here
[IMG][/IMG]

Or from Amazon for a lot cheaper.
[IMG][/IMG]

It is well worth the money.

[Kesephist]

Maybe I'm not getting it properly... the solar power layout you folks are all touting is photovoltaic, sunlight to electricity direct.

Is there out there a solar to steam to turbine power layout that doesn't cost a bleedin' fortune?

Kesephist

[Domeguy]

Not unless you consider several hundred million cheap.[IMG][/IMG]