System sizing checkup
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New_Climber
Registered Users Posts: 12 ✭
I have a garage/shop/barn that currently doesn't have any electric wired to it. I have been using a 100ft ext cord to get some power for lights.
I am wanting to install a small solar system to be used for all my overhead lighting. My load I currently foresee is 10 - 13w CF over head lights of which I see using for about 5hrs per day, for half the week.
So, is my calculation correct that I will need 650w of capacity (13w*10ea*5hr)?
Then for battery capacity: 32XHS-12v has 105ah at 5-hr rating....This battery gives me 1260watts total over 5hrs? (am I reading the battery information correctly)?
As for panels, I already have 2-Grape solar 185w, 36wmpp....So to make a rough estimate of how much power these can produce I just took total rated power and halved it...so I can make about 185w/hr. I live in the pacific northwest so using peak sun of 3.5hrs per day, I can produce about 640w per day.
Questions:
Are my calculation remotely correct? Also, I am not sure if I have enough power production to recharge my batteries, especially in the winter when I get the least amount of sun?
I know I also will need an inverter and charge controller, but I just want to see if I was on the right path to start with?
Thx for the help?
I am wanting to install a small solar system to be used for all my overhead lighting. My load I currently foresee is 10 - 13w CF over head lights of which I see using for about 5hrs per day, for half the week.
So, is my calculation correct that I will need 650w of capacity (13w*10ea*5hr)?
Then for battery capacity: 32XHS-12v has 105ah at 5-hr rating....This battery gives me 1260watts total over 5hrs? (am I reading the battery information correctly)?
As for panels, I already have 2-Grape solar 185w, 36wmpp....So to make a rough estimate of how much power these can produce I just took total rated power and halved it...so I can make about 185w/hr. I live in the pacific northwest so using peak sun of 3.5hrs per day, I can produce about 640w per day.
Questions:
Are my calculation remotely correct? Also, I am not sure if I have enough power production to recharge my batteries, especially in the winter when I get the least amount of sun?
I know I also will need an inverter and charge controller, but I just want to see if I was on the right path to start with?
Thx for the help?
Comments
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Re: System sizing checkupNew_Climber wrote: »I have a garage/shop/barn that currently doesn't have any electric wired to it. I have been using a 100ft ext cord to get some power for lights.
Then look at solar for the education/backup power...I am wanting to install a small solar system to be used for all my overhead lighting. My load I currently foresee is 10 - 13w CF over head lights of which I see using for about 5hrs per day, for half the week.
So, is my calculation correct that I will need 650w of capacity (13w*10ea*5hr)?- 650 Watt*Hours per day.
Then for battery capacity: 32XHS-12v has 105ah at 5-hr rating....This battery gives me 1260watts total over 5hrs? (am I reading the battery information correctly)?
Nominally, recommend 1-3 days of "no sun" plus 50% maximum discharge for long life. For 2 days of power:
650 WH * 1/12 volt battery bank * 2 days no sun * 1/0.50 max discharge = 217 AH per day
You can go with 105 AH @ 12 volts, but you will only have one day of "no sun" carry through. And a bit shorter battery life--But it is certainly a valid configuration.As for panels, I already have 2-Grape solar 185w, 36wmpp....So to make a rough estimate of how much power these can produce I just took total rated power and halved it...so I can make about 185w/hr. I live in the pacific northwest so using peak sun of 3.5hrs per day, I can produce about 640w per day.
Note that you should never plan on using 100% of your power every day--But if you go in the shop every other day, you will be OK.Questions:
Are my calculation remotely correct? Also, I am not sure if I have enough power production to recharge my batteries, especially in the winter when I get the least amount of sun?
If you are on the cost, the amount of sun can be terrible. Using PV Watts fixed array tilted to latitude for Quillayute WA:Month Solar Radiation (kWh/m 2/day) 1 1.51 2 2.21 3 3.12 4 4.04 5 4.73 6 4.74 7 4.91 8 4.57 9 4.37 10 3.31 11 1.87 12 1.85 Year 3.44
So, yes, during winter you may need a lot more panel or use a lot less power. That Marine layer is a killer.
I know I also will need an inverter and charge controller, but I just want to see if I was on the right path to start with?
The Rogue 30 amp MPPT controller would be a great fit.
The MorningStar 300 watt 12 volt TSW inverter is the best small / 12 volt inverter out there right now.
-BillNear San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset -
Re: System sizing checkuphen look at solar for the education/backup power...
I am wanting to install a small solar system to be used for all my overhead lighting. My load I currently foresee is 10 - 13w CF over head lights of which I see using for about 5hrs per day, for half the week.
So, is my calculation correct that I will need 650w of capacity (13w*10ea*5hr)?
650 Watt*Hours per day.
Basically, I am using this solar system more as an education lesson then to get power to the shop. The battery I quoted, I already have for a travel trailer, and I have the panels, so I am somewhat half way there with equipment.
As for your correction as quoted, you highlighted HOURS per day. With my plan, I would use 13w*10ea=130w per hour the lights are on. If I use them 5hr per day, isn't it a total of 650watts per day? Or are you correcting my mis-use of terminology?? Meaning 650watts total per days, should be stated as 650watt hours (wh) per day? As I have learned, using the correct terminology makes getting help so much easier. -
Re: System sizing checkupNew_Climber wrote: »Basically, I am using this solar system more as an education lesson then to get power to the shop. The battery I quoted, I already have for a travel trailer, and I have the panels, so I am somewhat half way there with equipment.
As for your correction as quoted, you highlighted HOURS per day. With my plan, I would use 13w*10ea=130w per hour the lights are on. If I use them 5hr per day, isn't it a total of 650watts per day? Or are you correcting my mis-use of terminology?? Meaning 650watts total per days, should be stated as 650watt hours (wh) per day? As I have learned, using the correct terminology makes getting help so much easier.
The confusing part is the Watts per Hour... Watts is already a Rate (like Miles per hour). There is not a Watts per Hour (--actually there is, it is the equivalent to acceleration or ft/sec2).
Multiply Watts * Hours gives you Watt*Hour which is equivalent to MPH * Hour = Miles driven.
I understand the desire to learn more about solar by starting with a small system... Your system will work fine (within its limitations).
-Bill
PS: Watts are already Joules Per Second (J/S)... And somebody decided to call the "derived unit" a "Watt".
Sort of like naming Miles per Hour a "Bill". And Bill*Hours would be miles driven.Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset -
Re: System sizing checkup
Power is measured in watts, and is a rate of energy usage. WattHours is an amount of energy.New_Climber wrote:Then for battery capacity: 32XHS-12v has 105ah at 5-hr rating....This battery gives me 1260watts total over 5hrs? (am I reading the battery information correctly)?
that's 1260 watthours or 1.26 kilowatthoursNew_Climber wrote:If I use them 5hr per day, isn't it a total of 650watts per day?New_Climber wrote:My load I currently foresee is 10 - 13w CF over head lights
So your load is 130 watts. Your inverter must be sized larger than that because the power factor of CFs is less than 1. May I suggest the morningstar suresine 300. Also, no inverter is 100% efficient. Therefore you will be drawing more than 650 watthours from your battery every day. That's more than 50% of your battery's capacity and will shorten your battery's life.
--vtMaps4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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