What do I need here?

I am a complete novice when it comes to solar. I live in western Kentucky. I am currently building a new garage and carport/patio area without access to electricity. This area gets about 7 -9 hours sun in the summer and about 3-4 in the winter. I have been trying to find out what I need to power this building but not having a lot of luck. What I have found is that I need a system somewhere between $1000 and $8000 and 2-10 solar panels with a 500-2000 watt inverter. See why I need help? I don't want a huge system but I also don't want it to be too small that may cause me to run out of power overnight.

I will have 6-8 LED lights, a garage door opener (used twice per day), maybe a ceiling fan or 2 (only used while sitting on patio), and some plugs for my pit boss smoker (use this maybe 2 times per month for about 6-10 each time). Maybe in the future I will get some small infrared heaters (again only used while sitting on patio) to extend my season.

As you can see there will be very little to no constant power usage except for possibly some LED Christmas lights for about a month or so. If I can in the future I'd like some security cameras but right now it's just what's listed above.

I would like to know where I can find out how many and what size panels I will need along with the other equipment (inverters, cables, switches, fuses, etc. ) along with how many and what size/kind of batteries I would need.

Thanks in advance for your help and I greatly appreciate it.

Big_Al_Ky said:

I am a complete novice when it comes to solar. I live in western Kentucky. I am currently building a new garage and carport/patio area without access to electricity. This area gets about 7 -9 hours sun in the summer and about 3-4 in the winter. I have been trying to find out what I need to power this building but not having a lot of luck. What I have found is that I need a system somewhere between $1000 and $8000 and 2-10 solar panels with a 500-2000 watt inverter. See why I need help? I don't want a huge system but I also don't want it to be too small that may cause me to run out of power overnight.

Click to expand...

Link #1 in my signature. Use PVWatts for your exact location to nail down the "solar hours".

Big_Al_Ky said:

I will have 6-8 LED lights, a garage door opener (used twice per day), maybe a ceiling fan or 2 (only used while sitting on patio), and some plugs for my pit boss smoker (use this maybe 2 times per month for about 6-10 each time). Maybe in the future I will get some small infrared heaters (again only used while sitting on patio) to extend my season.

Click to expand...

Link #1 in my signature. Enter all the above (and any future/seasonal devices) into the energy audit spreadsheet. Make estimates of maximum daily use. Either you design to meet all needs, or you likely won't meet any.

Big_Al_Ky said:

As you can see there will be very little to no constant power usage except for possibly some LED Christmas lights for about a month or so. If I can in the future I'd like some security cameras but right now it's just what's listed above.

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Usage when you're not using it doesn't matter. Usage when you're using it matters. It's beyond irrelevant that you might only use this or that or the other on and off days or only seasonally. You need to look at every realistic case and ensure your system meets those needs.

Big_Al_Ky said:

I would like to know where I can find out how many and what size panels I will need along with the other equipment (inverters, cables, switches, fuses, etc. ) along with how many and what size/kind of batteries I would need.

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Impossible until you do as thorough an energy audit as possible.

Thanks for the response.

This is what I got from PVWatts but I don't know what it is telling me. Can you help me from here.

With your panels mounted at 20° tilt due south, this is what you get in hours by month:



In June, a 1000W array would yield 1000W * 6.33h = 6330Wh of energy.
In December, a 1000W array would yield 1000W * 1.70 = 1700Wh of energy.

PVWatts takes the last 30 years of weather data into account in generating those numbers.

Most importantly, it illustrates that winter performance is notably worse than summer.

It might be worth re-running it with your panels tilted to your latitude rather than 20°. That should improve winter noticeably with only a little impact on summer.

Thank you again for your response.

I understand what you are telling me but what do I do with it and where do I go from here? Just for instance, if I installed 1000W of panels and a 1000W inverter, how do I find out how many and what kind of batteries I will need? What else inline would I need(fuses, switches, etc.)? I know the battery drain depends on what is hooked up and running at the time. With that being said though, wouldn't the battery drain only come into play when there is cloud cover or at night with no more than I'll be using it? As I said earlier I'm not going to be running an air conditioner or refrigerator, it'll all be low amp items (LED lights, ceiling fan) except for the smoker and the occasional garage door opener.

Maybe I'm thinking it's simpler than it really is, if I am I'm sorry. Again I'm dumb when it comes to this subject.

Big_Al_Ky said:

Thank you again for your response.

I understand what you are telling me but what do I do with it and where do I go from here? Just for instance, if I installed 1000W of panels and a 1000W inverter, how do I find out how many and what kind of batteries I will need? What else inline would I need(fuses, switches, etc.)? I know the battery drain depends on what is hooked up and running at the time. With that being said though, wouldn't the battery drain only come into play when there is cloud cover or at night with no more than I'll be using it? As I said earlier I'm not going to be running an air conditioner or refrigerator, it'll all be low amp items (LED lights, ceiling fan) except for the smoker and the occasional garage door opener.

Click to expand...

Have you done this?

sunshine_eggo said:

Link #1 in my signature. Enter all the above (and any future/seasonal devices) into the energy audit spreadsheet. Make estimates of maximum daily use. Either you design to meet all needs, or you likely won't meet any.

Click to expand...

Big_Al_Ky said:

Maybe I'm thinking it's simpler than it really is, if I am I'm sorry. Again I'm dumb when it comes to this subject.

Click to expand...

It's trivial to buy components, install and connect them. If that's your goal, it's easy. If you're trying to meet some need, you need to define your energy needs (you need to go beyond just a list of things - you need their power usage and the time required) and your available solar (you've done this bit).

You can't get hung up on "I don't know." You need to make a sensible estimate. It doesn't matter that you might not use the power for days at a time. What matters is the day you use the crap out of it - you don't want to go dark halfway through the day.

Check out the power consumption of electric infrared heaters. That really redefines the scale of your system.

Batteries are there to provide power during the times PV is unavailable or insufficient. They are also there to act as a reservoir to store excess PV.

It really is pretty simple... You need X kWh/day. You need enough PV to provide that much energy per day (that's where the hours numbers from PVWatts comes in), and you need the same X kWh of battery to provide 24 hours of backup.

You need to establish X.

I did this and the worse case came up with 3,238 Total Watt Hours per Day and 97 kWh/mo. This is including things that I may never have but added anyway.

Does this get me closer?

If you use 3,238 watt hours in 24 hours, you would need about the same amount of battery storage (3,238 watt hours) then you will need 1904 watts of solar to generate that much power in December (3,238/1.70). let's round the needed solar to 2,000 watts or 2kw of solar panels needed. If you wanted to make sure the garage door opener works every day, you would need to multiply the number of cloudy days in a row by your daily consumption because cloudy days would roughly only yield 10% of the power you would generate on a 100% sunny day. If you wanted to make sure your system had power after a week of rain in December, you would need a battery with a capacity of at least 22,660 watt hours (7x3,238) Now it gets fun, if you have 2kw of solar, it will generate 12,760 watt hours of electricity on average every day in June. Since you will only use 3,238 watt hours per day, about 9,000 watt hours will be wasted. You would also need to account for whatever losses you may have from the charger and inverter and the inverter idle consumption.

This is why sizing a solar system is so complicated.

Big_Al_Ky said:

I did this and the worse case came up with 3,238 Total Watt Hours per Day and 97 kWh/mo. This is including things that I may never have but added anyway.

Does this get me closer?

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Yes!

Of all those devices you might run simultaneously, what is the maximum instantaneous power requirement in Watts?

3.2kWh/day

As mentioned, you'd need about 3.2kWh of battery for 24 hours of backup.

Now the question becomes what month do you want to use? If you want to ensure 3.2kWh/day available in all months, then you use December...

3.2kWh/1.7h = 1.9kW

Since you've already mentioned 1000W, that would mean you need 3.2kWh/1kW = 3.2h/day to meet your needs. Looking at the PVWatts output, you'd be good 8 months out of the year.

Thank you for your help. Since our winters are pretty cold and weather is not the greatest I would more than likely not be using anything but the garage door opener between mid November thru April.

From what I've seen else where, I'm pretty sure I can add on at a later date if I see I need to, Correct?

Big_Al_Ky said:

Thank you for your help. Since our winters are pretty cold and weather is not the greatest I would more than likely not be using anything but the garage door opener between mid November thru April.

From what I've seen else where, I'm pretty sure I can add on at a later date if I see I need to, Correct?

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Yes. Once you know the final goal, you can piecemeal it if needed.

You did mention infrared heaters, which I presume you would favor use in the cold months, AND if they use resistance heat, they can use crazy amounts of power.

The heaters were only a thought that will probably never happen. I already have propane heaters so I'll stay with them at least in the foreseeable future.