Need some help designing a off grid 24hr system

[Madrass]

Hello my name is Dwayne and I am seeking in assistance with designing a full off grid system total load 14720watts would like to design it to be expanded in future.

1.How many batteries are needed
2. Array configuration and quantity

 

[Norwasian]

Hello my name is Dwayne and I am seeking in assistance with designing a full off grid system total load 14720watts would like to design it to be expanded in future.

1.How many batteries are needed
2. Array configuration and quantity

For me, the first step in designing the system was determining what and when the loads would be. This impacts how much production will be needed, and how much battery storage will be required to supply it. If the loads are not heavy during the non-solar hours, much less battery is needed, and, from what I have ascertained, the battery can easily be the most expensive component of the system.

So I would start by calculating the expected wattage of usage/loads, with an eye to the typical time of day for those loads. Then, in my case, to mitigate against cloudy days (for a completely off-grid setup with no option of public utility/grid as a backup), I doubled the battery capacity that I estimated would be necessary for one diurnal cycle. This should get me through at least one cloudy day without recharging. Then I added an additional 20% to the battery capacity to keep from cycling it too deeply. In the math, in other words, what I would actually draw out from the battery should not exceed .8C (80% of the battery capacity), as it is not good to run the battery to zero, even for LiFePO4 batteries (which I want to use).

Until you know your usage requirements, you are not yet prepared to make any determination of battery size, nor of paneling. If your peak usage coincides with peak solar production, you may be able to supply it from the panels without a large investment in batteries. Of course, remember that rainy days do happen--and only you will know how mission-critical your system must be. If it's okay to be out of power on occasion, it can make a big difference in your planning and budget as compared to majorly over-designing a system that is fail-safe even given a week of rain. In my case, the week of rain may be a reality, so I am hoping to use a generator as a backup for charging the batteries in those times (usually only about three-four weeks per year during rainy season).

 

[OffGridForGood]

PVWatts.nrel.gov

 

[Madrass]

If Highest monthly consumption is 800kwh and lowest 370kwh monthly there's nothing more that is needed than to design a system that fits well in that criteria with over 12hrs daily sunlight more than enough to charge fully with the correct array sizing

 

[DIYrich]

800kWh per month is about 27kWh per day. For off grid, the rule of thumb is 3 days of battery, so that is 80kWh of battery.

For panels, I would want enough for 50kwh per day in months where you use 800kwh, or enough to produce 2 days of usage in 1 day during the worst solar production month. If you have week long rains during monsoon season, then plan for that.

If you have a backup generator, you can cut back.

 

[MichaelK]

One lesson quickly learned when going off-grid is that you will be hard-pressed to maintain exactly the same off-grid lifestyle as it was on-grid.

One thing you will find though is that 27kWh per day can be strikingly decreased with proper conservation. At my own place, with lights, TV on, the computer running, and frig on 24/7, I'm only consuming in the range of 4-5kWh of power, and could get that down to 3.5kWh if I felt like it.

Being in Florida, I'll expect that your single biggest power hog will be air-conditioning. Although whole-home air-conditioning is doable on solar, you may find it prohibitory expensive. How about multiple room air-conditioners, that can be turned on and off as needed? I have air-conditioning at my own cabin, but typically restrict it to upstairs in the bedroom only for sleeping.

I'd say, going room by room, you could reduce consumption to about 5kWh per room in an overnight situation. Generally, solar could supply 100% of your air-conditioning load during the day with no issues at all. It's the overnight running of the air-con that will put the most strain on your system.

I'd say start looking at a solar array of maybe 4000W of panels and a 500Ah battery bank that powers a 6-8kW inverter. Look at quality brands making low-frequency sine-wave models like Outback's Radian, or Schneider's XW-Pro.

 

[Madrass]

800kWh per month is about 27kWh per day. For off grid, the rule of thumb is 3 days of battery, so that is 80kWh of battery.

For panels, I would want enough for 50kwh per day in months where you use 800kwh, or enough to produce 2 days of usage in 1 day during the worst solar production month. If you have week long rains during monsoon season, then plan for that.

If you have a backup generator, you can cut back.

That sounds just about right ️ where this house is its positioned E to W and In Jamaica sunlight from 7am until 5pm 11hrs a day

 

[DIYrich]

Generally, solar could supply 100% of your air-conditioning load during the day with no issues at all. It's the overnight running of the air-con that will put the most strain on your system.

When off-grid, while the general case is interesting, you have to plan for the worst case. Running AC when it is 90 degrees and cloudy.