I am in need of assistance in determining what size solar panels, batteries and charge controller to use for my solar system. Everything will be 24V DC. I will be powering a unit that uses 200watts and will be running 8Hrs/day. This unit when not running uses 100watts in standby and will be running for the rest of the day when it is not running at 200watts. I also have a pc that uses 75 watts and will be running 24 hrs/day. This is a off grid situation. I have a fairly large trailer with out riggers to mount all of the panels and equipment to. As of right now I do not need AC power. Any suggestions would be appreciated.
Sizing my solar system
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Welcome to the forum my friend. You came to the right place for help. Piece of cake. You want 5000 wh per day.
24 volt battery Capacity = 1040 Ah weighing 1600 pounds and cost roughly $5000. If you baby it will last 5 years before replacement.
Panel Wattage = 2200 watts
MPPT Controller = 80 amps
Easy Peazy. Don't forget you will need a generator and AC charger for those cloudy spells and you are all set to go. Let us know if you need anything else. We are open 24 hours per day.
Good Luck.MSEE, PE -
If I was to change the unit from only running 200watts for 8 hrs per day and not going into standby mode for the rest of the day at 100watts. What would be the required system for this? I am little concerned about having 1600 Lb battery on the trailer.Comment
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I am very new to the solar field, Sorry for the all the questions. When you say 2200 watt panel size, is that like 7 or 8 300watt panels( since they are more common) in series or parallel? Is the battery just one big battery or is it best to use multiple batteries for this in series or parallel?Comment
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200W x 8 hours = 1600Wh a day. You don't say where you are, so I can't do an accurate sizing for the solar, but guessing worst case of 2.5 sun hours, 1600Wh/2.5 sun hours/.67 inefficiencies=955W. Round up to 1000W, so 4 panels that are 250W each. Wired in 2 parallel strings of 2 in series.
1600Wh x 2 (50% DoD) x 1.2 temperature compensation (again guessing how cold it will get) / 24V = 160Ah per day of storage. Without a generator, you'd need to determine how many days you would potentially be without sunlight, minimum of 3 I would imagine, so 160Ah x3 days = 480Ah 24V battery bank minimum. 2 parallel strings of 2 8A8D 12V 245Ah batteries in series, if they'll fit. 20.75" x 11 " x 11" 158lbs each. Times 4 batteries = 632lbs. You can do more smaller batteries if needed, but the overall weight will end up being about the same.
8.7Isc for a 60 cell 250W panel x 2 in parallel = 17.4A
40V nominal in / 24V nominal out = 1.66 ratio in to out
1.66 x 17.4A x 1.25 NEC = 36.1A = 40A MPPT charge controller needed at minimum. For example, Morningstar TS-MPPT-45.Solar Queen
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Solar Queen, Could you spec things out with my first thread. I am wanting to get a worst case scenario. A unit @ 200Watts 8 hrs/day and 100watts in standby the rest of the day. Also had pc running 24/day 75 watts. Everything 24V. No generator wanted and everything is DC. No invertor needed. Thanks in advance!!Comment
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I guessed right for sun hours, 2.5 in December. 100W x 16 hours is also 1600Wh, so double the size as previous quote. 2000W solar and 320Ah 24V battery bank per day of backup.Solar Queen
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Just saw about the PC. (200W x 8 hours) + (100W x 16 hours) + (75W x 24 hours) = 5000Wh
5000Wh / 2.5 sun hours / .67 = 2985W, round up to 3000W of solar
5000Wh x 2 (50% DoD) x 1.3 (went a little colder) / 24V = 541Ah 24V battery bank per day. x 3 days = 1625Ah
3000W solar / 300W 24V panels = 10 panels (went with bigger 24V 72 cell panels), 5 parallel strings of 2 in series ($300 each = $3300)
1625Ah / 915Ah 2V battery (Concorde PVX-9150T) = 2 parallel strings of 6 in series, 12 total. ($440 each = $5200) 94lbs each x 12 = 1128lbs.
2 60A charge controllers needed, ~$500 each.
At least $10k.Solar Queen
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Solar Queen, another newbie question. How do the charge controllers hook into system? How do they connect to the panels. Do they run in series of each other?Comment
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