Complete rookie needs help with first project

[Sunking]

Load is a 12V 15W LED. 8 hours/day -> 15*8=120Wh. With fudge factor 1.5 that gives 180Wh required per day
The place the system will be installed has 3 sun hours in december (worst case). That means the panel will have to be a 60W one.
The battery has to have a 5 day self reliance which means it requires at least 120*5=600Wh of energy. Assuming it will output a voltage of 12V that means it needs to have 50Ah
The controller will have to process 60W of power which means it will have to be a 5 Amps one.

Have I missed anything?

If you are using PWM controller Fudge Factor is 2. For MPPT 1.5. However 60 watt panel will work as minimum required with PWM is 50 watts.

[Jokeaccount]

What he actually told me is that I have two options:

1) Connect each panel to a different controller (not cost effective)
2) Connect each panel in parallel into a single controller but the panels will output less Wattage than expected (just like your connection instead of 1k gives 750W)

Anyways, let me give you a run down of what I have so far to make sure I haven't made a huge mistake somewhere:

Load is a 12V 15W LED. 8 hours/day -> 15*8=120Wh. With fudge factor 1.5 that gives 180Wh required per day
The place the system will be installed has 3 sun hours in december (worst case). That means the panel will have to be a 60W one.
The battery has to have a 5 day self reliance which means it requires at least 120*5=600Wh of energy. Assuming it will output a voltage of 12V that means it needs to have 50Ah
The controller will have to process 60W of power which means it will have to be a 5 Amps one.

Have I missed anything?

[mega man]

1) I asked a fellow student about connecting 2 panels in parallel or in series and he said that such a connection wouldn't net the 45W required. Also, connecting them separately would require 2 controllers which is definitely not cost effective. But what is this about the 45W panel not operating at full capacity? I know that in the calculations of Wh required for the load we increase by a 50% (fudge factor), is that it?

the fellow student your asking is also still learning, i have 1000watts of panels(1kw) comprised of more than 1 panels which are wired parallel and i get about 750watts when it reads on my mppt controller, i don't have a sun issue as most of you do as i live in Jamaica where its always sunny(we do have rain sometimes lol), as the day breaks i begin to charge and have sun all the way until 5 in the evening(sometimes even longer), and with all these panels i use a single 60amp controller so him telling you about 2 controllers is incorrect, and fudge factor is an added amount used when calculating expected needs, panels operating at less than what they say they are has nothing to do with that, if a panel says its 280watts your most likely to get 220watts or say 240watts, to see a max reading you'd have to be exposed to extreme circumstances.

cheers.

[Naptown]

Two identical panels wired in parallel will give you 50 watts from the panels
Now if you are using a pwm controller it will only be about 35 watts
Since your panels will put out 17 volts approx that is all the amps you will get.

[Jokeaccount]

just connect 2x 25watt panels in parallel, you'll maintain the same voltage but increase the wattage, and if its 45w you need i'd suggest u getting say 65-70watts of panels, a 45w panel will operate at 25w so you need more to acquire a specific target

1) I asked a fellow student about connecting 2 panels in parallel or in series and he said that such a connection wouldn't net the 45W required. Also, connecting them separately would require 2 controllers which is definitely not cost effective. But what is this about the 45W panel not operating at full capacity? I know that in the calculations of Wh required for the load we increase by a 50% (fudge factor), is that it?

[mega man]

just connect 2x 25watt panels in parallel, you'll maintain the same voltage but increase the wattage, and if its 45w you need i'd suggest u getting say 65-70watts of panels, a 45w panel will operate at 25w so you need more to acquire a specific target

[Jokeaccount]

Except from the previous question (which I'm still looking for an answer) I also have a new one:

It seems that I'm gonna need a 45W panel. Now I went and checked the store and they sell 20 and 25 W panels (no 45 ones). Can I connect a 20 and a 25 to make 45 with a single battery? I have the feeling that the output voltages will be different thus making it impossible but wouldn't that be the same even if I connected two 25s to make a total of 50W panel? Maybe they have the same specs but different positions and other factors could make them have slightly different output voltages right?

[SunEagle]

Tell you what. I am feeling generous today. I will cut you in for 30% ownership of the company. Send a check of $10,000 good faith deposit and then we will talk.

ya got my interest. how about 6% interest for $2000?

[Jokeaccount]

Ok i've checked the tutorial on the sticky and I'm now looking to get the numbers down. I found this link for sun hours per day: http://pveducation.org/pvcdrom/prope...lar-insolation

The thing is, the graph calculates 3 things. Incident power, power on the horizontal and module power. It says that module power is when the panel faces south with a 45 degree angle. Is that the number I'm looking for? I tested to see if Tucson (which the tutorial says has 5.6 kwh/m2/day) with latitude of 32 gives the same via this calculator and it gives a 6.1 (close to 5.6) on the module graph whereas Seattle gives 1.2 on the horizontal graph, so now I'm confused. I'm guessing the Module graph is the one i need as long as I put the panel in a 45 degree angle but still I'd like to be sure

THanks

[Sunking]

I'll be looking for it on Kickstarter, so I can invest and maybe even become a dealer.

Tell you what. I am feeling generous today. I will cut you in for 30% ownership of the company. Send a check of $10,000 good faith deposit and then we will talk.

[inetdog]

Horse feathers. I have for sale a unit that contains an electric motor, alternator, and a PF device with a PF of 2. All you have to do is get the motor spinning to get the alternator generating electricity an you have free power for life.

I'll be looking for it on Kickstarter, so I can invest and maybe even become a dealer.

[Sunking]

PF = Power Factor. It is a number less than 1.0

Horse feathers. I have for sale a unit that contains an electric motor, alternator, and a PF device with a PF of 2. All you have to do is get the motor spinning to get the alternator generating electricity an you have free power for life.

[inetdog]

SunEagle: Thanks i'll look out for that link

Just Google "PVWatts" for a start.
PF = Power Factor. It is a number less than 1.0 which tells you how much "useless" current is going through your wiring in addition to the part that is actually delivering power. An inductor (motor) , a capacitor (CFL) and a power supply all can have a low Power Factor. Which makes an inverter work harder to deliver the same amount of actual power.

[Sunking]

Yeah i remember we did that in school. I suppose i don't have to calculate sunlight in the specific location right?

You had better or else it will fail. Most importantly is the winter Solar Insolation Sun Hours.

It also makes you realize the huge cost. For example 400 Wh/day with 3 Sun Hours requires a 200 watt panel.

[Naptown]

Power factor