First timer going full-bore in Central America

[miahallen]

I'm planning a major move to Central America soon...the locals tell me I should expect greater than 800W/h/m2. There is no "grid" in the area, so off-grid solutions are my only option. The community is eco-friendly, and I DO NOT plan to supplement my solar system with a generator. If power runs out, we'll just have to get by without it. I've gone through most of the sticky information trying to figure out what the optimal system for me would be, and I think I have a plan, would you experts please evaluate me and tell me how I'm doing thus far? Thanks in advance.

1. Based on my family's power usage over the past few years, I would need about 25Kwh per day.
2. Fudge factor - 25Kwh x 1.5 = 37.5Kwh
3. Sun hours in December = 11h ... solar isolation = 8.8Kwh/m2/day
4. Size of Solar panel array = 37.5Kwh / 8.8h = 4.26Kw
5. Battery size required = 25Kwh x 5 = 125Kwh / 48V = approx 2600Ah @ 48V
6. Charge controller = 4.26Kwh / 48V = 89A (I haven't found a controller that will do this)
7. Battery bank = 8 x 460Ah 6V = 3680Ah @ 48V

The immediate problem I've identified is that the charge controllers only allow up to 60A output, which is not enough for my proposed system. So I would rather downgrade as I believe our lifestyle change will encourage lower power consumption. So my revised system would be built as follows:

1. Shooting for 5Kwh per day or less.
2. Fudge factor - 5Kwh x 1.5 = 7.5Kwh
3. Solar isolation in December = 4Kwh/m2/day
4. Solar panel array = 7.5Kwh / 4h = 1875W required ... I would use fourteen 230W panels = 3220W
5. Battery size required = 5Kwh x 5 = 25Kwh / 48V = approx 520Ah @ 48V
6. Charge controller = 3220wh / 48V = 67A ... I would use a 150A MidNite Solar Classic 150
7. Battery bank = 8 x Rolls S-530 530Ah 6V = 530Ah @ 48V

I think this would provide my family and I plenty of power in our new home, the question is, have I missed any steps....and have I done my calculations correctly?
Would you suggest any revisions to my plan...and would you recommend sourcing any of the equipment from alternative stores?
My biggest concern is the battery bank seems way too big (1666Ah needed, 3690Ah planned)....but I think that is probably preferable right?

Thanks again in advance

[Sunking]

Where are you getting 8 sun hours from? I would be very skeptical of that. You use the worse case month and there are no places on earth I know that have a minimum 8 Sun Hours during the full year.

As for charge controllers using 48 volt battery and 4.26 Kwh is no problem using a Midnite Solar Classic 150. The 150 can take up to 5020 watt on a 48 volt battery.

Classic Power Charts
Classic Comparison.

The one step you overlooked or dismissed is a generator. A generator and AC charger is mandatory for any off-grid solar system especially if you have a significant investment in batteries. Solar is not capable of providing the required preventative maintenance batteries require. A 100 Kwh battery is going to cost you around some $20,000 for a good 5 year battery. Without a generator you will have to replace then in a year or less.

You can get a inverter with generator input and built in AC charger. Trust me you need it. You will deeply regret not getting a genny with an inverter with built in geneey support and charger.

[inetdog]

Where are you getting 8 sun hours from? I would be very skeptical of that. You use the worse case month and there are no places on earth I know that have a minimum 8 Sun Hours during the full year.

At or near equator, with clear horizon to horizon view AND using a horizontal axis tracker?
Without tracking there is certainly no way to get 8 sun hours equivalent, AFAIK, just based on the geometry.

[Sunking]

At or near equator, with clear horizon to horizon view AND using a horizontal axis tracker?
Without tracking there is certainly no way to get 8 sun hours equivalent, AFAIK, just based on the geometry.

I did not catch that. THX

[paulcheung]

I'm planning a major move to Central America soon...the locals tell me I should expect greater than 800W/h/m2. There is no "grid" in the area, so off-grid solutions are my only option. The community is eco-friendly, and I DO NOT plan to supplement my solar system with a generator. If power runs out, we'll just have to get by without it. I've gone through most of the sticky information trying to figure out what the optimal system for me would be, and I think I have a plan, would you experts please evaluate me and tell me how I'm doing thus far? Thanks in advance.
[*]Battery size required = 16Kwh x 5 = 80Kwh /48V = approx 1666Ah @ 48V[*]Charge controller = 2760wh / 48V = 57.5A ... 60A @ 48V[*]Battery bank = 8 x 460Ah 6V = 3680Ah @ 48V (overkill I know)[/LIST]

my biggest concern is the battery bank seems way too big (1666Ah needed, 3690Ah planned)....but I think that is probably preferable right?

Thanks again in advance

Where do you get that calculation from? 8x 460AH 6V =3680AH @48volt?
It is not 3680 AH @ 48 volts , it is only 460AH @48 volt. You need 24 of the 2volts 1776 AH or 32 of those 6volts 460AH batteries to make it 1840AH @48 volt.
Like Sunking said, Generator is a must for off grid.

Cheers.

[Mike90250]

Two things

1) you need an energy diet. You need to obtain the most efficient appliances, shift loads to daylight hours (don't need to recharge batteries if you use the power in the daytime). Energy Star rated appliances are a good start.

2) got to re-consider the No Generator decree. Does your planned site have monsoon weather for a month ? Cloudy days mean you only harvest 10% of a normal day's power. Two cloudy days and your batteries are flat, and starting to sulphate. Or you don't have enough power for an EQ cycle in the cloudy season. About the only choice to avoid stratification, is AGM batteries, which are not susceptible to stratification. But AGM is quite expensive. Replacing batteries killed by no generator is also expensive. You can't just "switch off loads" to preserve batteries, unless you do it in the late afternoon as the sun sets, to leave you with full batteries overnight. If you run loads at night, and the batteries are low in the AM, and it ends up being a cloudy, no power day, you are hosed.

[miahallen]

WOW! Great replies so far, thanks for all of your contributions...I know I have a lot of reading and thinking to do, and this definitely confirms it

@Mike90250
I do have pretty efficient appliances, but we are computer whores and we'll be curbing that habit. We also will not be using electric heating/cooling, so I know that will also help a lot.
I'm really not certain how much energy we'll end up needing, so I'm really taking blind shots at the figures right now. But I'm trying to be realistic and not expect any miracles.

@paulcheung
Thanks, I new my math had to be off, with everyone talking about how expensive batteries are, thanks for setting me straight....would twelve (12) 4V batteries @ 1557Ah work then? That's only $15K

http://www.gogreensolar.com/products/rolls-surrette-4-ks-21ps-4v-1-557ah-deep-cycle-battery

@Sunking & inetdog
Based on reports from solar users in the region who say they get 875W/h/m2...but I suppose that is on sunny days at noon huh? I'm not sure if I'll setup axis tracking, but I'm planning to look into it. The location is Belize, so yes...fairly close to the equator

[miahallen]

The one step you overlooked or dismissed is a generator. A generator and AC charger is mandatory for any off-grid solar system especially if you have a significant investment in batteries. Solar is not capable of providing the required preventative maintenance batteries require. A 100 Kwh battery is going to cost you around some $20,000 for a good 5 year battery. Without a generator you will have to replace then in a year or less.

You can get a inverter with generator input and built in AC charger. Trust me you need it. You will deeply regret not getting a genny with an inverter with built in geneey support and charger.

Can you point me in the right direction where I should begin looking? The "GoGreenSolar" doesn't seem to have any generators?
Also, will the inverter I selected above have a generator input? It doesn't appear to...

http://www.gogreensolar.com/products/cotek-sk3000-148-3000-watt-48v-pure-sine-wave-inverter

[Mike90250]

Can you point me in the right direction where I should begin looking? The "GoGreenSolar" doesn't seem to have any generators?
Also, will the inverter I selected above have a generator input? It doesn't appear to...
http://www.gogreensolar.com/products...-wave-inverter

Generator. There is a new style of generator, with auto-throttle speed/power control, that provides DC to an Inverter, and the inverter produces nice, clean AC. The Honda EU-2000 is the typical of that class. They are very quiet, and at less than full load, slow themselves down, saving fuel. Called Inverter Generators. Even Harbor Freight has an inverter model now (but I hear it only sounds like a generator)

Inverter. Many of the higher quality inverters, have a way to feed AC power into it, and it turns into a battery charger. A 95% efficient charger. Most chargers are in the 60 - 75% efficient class, and you pay for it in extra fuel costs, because you need a larger generator. And Outback and Xantrex/Schneider/Conext have inverters that can work WITH a generator, charging the batteries, and then supplying peak surge power if a load comes on that is more than the generator can handle. (Generator Support). Do you have a well pump?

But first, you need to dial in your loads. Modern laptops are now quiet efficient. But their sat modem may not be.

[miahallen]

Yes, I plan to have a well pump.

[Sunking]

You do not want that inverter. It is made for mobile applications. You need one made for premises wiring systems that are hard wired and does not use plugs. You need something like Schneider Conext XW series.

[paulcheung]

If you can't afford the XW series, at least get one of the Magnum MS4448PAE which have very good efficiency on 1500 to 2500 watts @90% according to their claim. The magnum have the AC charger build in the inverter, you can connect the generator to it and it has auto start for the generator.

[Mike90250]

Yes, I plan to have a well pump.

Good, now you need to know the volume and head you need, research the RIGHT size pump (not 3 sizes larger because that's what everyone else uses) and incorporate that into your power budget. I had to plan for 3,000 gallons of pumping daily for summer tree irrigation, so have tanks, pumps and several thousand feet of 2.5" PVC between my water storage, and use. Gives me about 75# of water pressure.

[miahallen]

OK...so I've reconfigured based on your recommendations...
I also found some data on solar insolation: http://www.gaisma.com/en/location/belize.html

1. Shooting for 5Kwh per day or less.
2. Fudge factor - 5Kwh x 1.5 = 7.5Kwh
3. Solar isolation in December = 4Kwh/m2/day
4. Solar panel array = 7.5Kwh / 4h = 1875W ... I would use eight 295W panels = 2360W
5. Battery size required = 5Kwh x 5 = 25Kwh / 48V = approx 520Ah @ 48V
6. Charge controller = 2360wh / 48V ~ 50A ... 60A @ 48V
7. Battery bank = 8 x 963Ah 6V @ 48V

Based on the calculations above, how does the shopping cart below look?
solar.JPG
Plus the Honda generator mentioned earlier (EU2000i)

Also, what are your recommendations for battery brand? So far I've looked at these "Trojan", and also the "Rolls Surrette" which seem to be slightly better value (and weigh 30% less).

[paulcheung]

If you use 820 or 925 amps battery you need to use panels produce at least 4000watts to charge the batteries at C12 rate. if you only use 10kwh in 24 hours and most of the heavy load are in the day when sun shining, and you have a generator for rainy days. I would just get 450 amps battery and 3000 watts panels and replace the battery every 3 years or 4 if you carefully maintain these batteries.

If money is not a problem, by all means get these 820 or 925 amps batteries and put the panels to 4000 watts and use two Charge controllers, you will be ok.

Cheers.