Using AC Solar Panel in Off-Grid Installation ?

Re: Using AC Solar Panel in Off-Grid Installation ?

You really need to define what is not "negotiable" in your system... If you want to use your existing 4 + whatever panels and design a system around them--Can do.

Of if you have a particular battery bank, then we design around that.

But--As always, the ideal is to design around your loads. If a system does not meet your loads--then it is not very useful. If the system is too big or "unbalanced" between battery bank, inverters, panels and various DC and AC battery chargers--It can be a waste of money...

For example, your freezer is a known load we can start with. Nominally, you need a ~1.2 to 1.5 kWH AC inverter. 12 volts would be OK, or 24 volt would be a bit better (and allow you more expansion options later). But this "costs" you the existing AC inverter and possibly the current solar charge controller and any DC Battery charger you may have currently.

The 4 "AC" converted to "DC" panels would charge a 24 volt battery bank pretty well with a 24 volt PWM controller--Which is a lot less expensive that just about any MPPT controller.

A 1.5 kW AC inverter would "want" a ~300 AH battery bank (just using rules of thumbs to keep discussion from getting too cluttered). A 300 AH @ 24 volt battery bank would want 5% to 13% rate of charge from solar... You could get away with 5% if system is not used too often--You should look at 10%+ if system is used often and/or for many weeks at a time (and you want to limit generator running/fuel usage):

• 300 AH * 29 volts charging * 1/0.77 panel+controller derating * 0.10 rate of charge = 1,130 Watt array "nominal"

Using the solarelectrichandbook site:
Port-au-Prince
Average Solar Insolation figures

Measured in kWh/m²/day onto a solar panel set at a 72° angle from horizontal:
(For best year-round performance)

Jan
Feb
Mar
Apr
May
Jun


5.58
5.73
5.69
5.69
5.63
6.26


Jul
Aug
Sep
Oct
Nov
Dec


6.26
5.77
5.44
5.22
5.13
5.29


Say 5.0 hours of sun minimum (that is a very sunny place), a 1,130 Watt array will produce:

• 1,130 watt array * 0.52 end to end system eff * 5.0 hours of sun per day = 2,938 Watt*Hours per day

That will probably keep your freezer running, plus lights, laptop, etc. very nicely.

And your overnight power usage from the battery bank (or dark day):

• 300 AH * 24 volts * 1/2 days of no sun * 0.50 maximum discharge * 0.85 inverter eff = 1,530 WH per day (no sun, or over night AC from battery power)

Around 3.3 kWH per day (3,300 Watt*Hours) is pretty close to a normal electric life with lots of conservation and turning off things not being used.

Comparing to your requirements:

Night Time:
2 60W fan @ 6hrs most night
Lighting 52W @ 4 hrs
TV Power Consumption (Max): 50W @ 4 hrs

2 * 60 watts * 6 hours = 720 Watt*Hours of AC power
52 watts * 4 hours = 208 Watt*Hours
50 watts * 4 hours = 200 Watt*Hours
==========================================
1,128 Watt*Hours per night

Daytime
mini-freezer 140W @ 6hrs
Phone - camera - laptop charging.
Occasional use of a blender 600W

140 Watt * 6 hours = 840 Watt*Hours
Phone+camera+laptop = 400 Watt*Hours (if laptop used 4-8 hours per day)
Blender 600 watts * 1/10th hour per day = 60 watts (6 minutes of use)
==========================================
1,300 Watt*Hours per daytime
2,428 Watt*Hours total of AC power per day.

That 300 AH @ 24 and 1,130 watt array would be "my" cost effective ideal system... Is it yours? I have no clue.

-Bill

PS: The above numbers are a bit on the conservative side--But keeps the calculations easier and allows for some extra power usage on your side. Things that run for many hours (laptop, freezer, fans, TV, lightning, etc.) are always strong canidates for conservation (most efficient versions you can buy) as well as doing accurate power measurements. The laptop may only use 200 WH per day (small system and 3 hours of use) or it may use 1,000+ WH per day (12 hours of usage on a bigger laptop). All guesswork until you have accurate numbers.

Re: Using AC Solar Panel in Off-Grid Installation ?

Sunny-HTI wrote: »

My projected load for now will be around 2,000 Watt (1,020 Daytime and 980 at nighttime).I am opened to suggestion, ideas and help from the forum to build an adequate system.

Is that 2,000 Watt*Hours per day?

In any case, what do you think of the system and analysis that I did in the previous post? It is pretty close to what you asked for (can drop it down in size a bit if my power estimates are on the high side, you want to use a generator more, etc.).

Once you nail down the loads and they system sizing--Then we can look at component selection.

-Bill

Re: Using AC Solar Panel in Off-Grid Installation ?

Harry, this your existing system?

4x30W PV - 30A Xantrex PWM - 2x6v Trojan T-105 225AH 1000 Watt 12V inverter

Have you put your freezer on your present system (see if it even starts)?

The big deal (for me) is the ~300 AH battery bank @ 24 volts (or ~600 AH at 12 volts if you want to keep the present 1kW 12 volt inverter)...

If that is too much battery bank, then what would be cost effective for you?

The battery bank is the "heart" of your system and will define starting surge current, how much power you can pull over night (or cloudy day), etc... The rest of the hardware "hangs" on the battery and is there to keep the battery "happy".

We can make any system configuration "work" (within reason)--But I would really like the system to meet your needs/expectations. You can push/pull specific parts of the system by -50% or +100% -- Beyond that, it is difficult to get stuff to "play together" nicely.

If the system is used a few days a week, or a couple weeks at a time and turned off the rest of the time--Solar power is very difficult to make it cost effective. Many times, a smaller/efficient genset and the cost of fuel is still chea per (if you can get a Honda or Yamaha inverter-generator--it would not be a bad deal).

Batteries have a limited life (in tropics, batteries age faster) and standard golf cart type battery--Perhaps 3-5 years.

And with batteries, you can spend 2x as much (better batteries, larger bank) and the batteries will last around 2x longer.... No real cost savings, just longer times between more expensive battery changes.

If you have issue with theft--You probably want to leave the minimum size system possible out there--Just less to lose.

A small system for lights+radio+TV and the genset for the larger loads (1-2 gallons per day when those loads are needed).

For a part time residence system, minimizing your big loads that you run from solar and the bigger stuff from the genset (few hours during the day, perhaps a few times a week) is usually more cost effective.

-Bill