Planning South America Off-Grid Installation. Some questions.

Galecra

Hi,
I'm from Argentina. I'm planning my first off-grid system for a house to be installed where grid is not available.
As I go to USA a couple of times each year, I have the chance to purchase some things there, considering here in Argentina they are 4x more expensive and older.
But I cannot make much mistakes, I have to know what to buy and buy them in advance, or I'll need to wait 6 months until next trip.

Considering that I wish to have more money to make a bigger system, the calculations for the house to be usable are around 220Ah per day, 2.5 KWh/day, using the house everyday to live in (is not a weekend cabin).
I estimated 7hs each day of good sun, as it is an area having at most a month/year really cold. With that I got around 600-700W (depending of course on the money available) solar array, considering losses and inefficiencies.
With those numbers, good luck and weather, I would be getting around 30-35Amps from a 12V solar array peak.
I'll get a generator for backup, but my idea is to use it as few as possible in the future...

So, my questions are:

1 - Do these calculations make sense, considering the loads I estimated for our living?

2 - Should I go with a 12V or 24V system?
I have a concern with the inverter, as finding affordable 24VDC-220VAC is not that easy, for a 600W pure sine inverter which is far more than what we need for now.. for bigger-bigger loads we would run them thru the generator or get a cheaper modified sine in the future.

3 - What charge controller should I get, MPPT or PWM, and what Amp rating? In this amount of power I'm planning, is a MPPT useful?..
I wish I could go for the MS TriStar 45A MPPT, that would cover all of our needs.
We could make an effort and buy it if it makes really difference, but a non-MPPT is less than half off the price. As we are short of money and things are expensive we have to make the best use possible of the resources. So if the MPPT will save me from buying another pv or make a real difference at the end of the day, then we would consider it.

4 - in case we can't buy the panels all together, but expanding the system over time let's say in two stages, then probably the panels will have different specs...Would be a good choice to get two smaller charge controllers instead of one-big controller, so then I can group the panels in two arrays by their specs?

5 - Related to 4), Can I mix PWM and MPPT and both together charge a single battery bank?

6 - Related to 4), if I group all the panels in one array, then for an array having panels with slightly different specs, is PWM or MPPT better?

Thanks a lot!, and sorry for the long message...

BB.

Re: Planning South America Off-Grid Installation. Some questions.

Galecra wrote: »

But I cannot make much mistakes, I have to know what to buy and buy them in advance, or I'll need to wait 6 months until next trip.

I would also add "tools" to that list... For a good DC Current Clamp Meter ($/usefulness), I would look at this Sears Model (you can pay $300-$400+ for a Fluke meter and not go wrong--but at $60, this is a very useful piece of test gear for not much money).

Other tools would include a decent Hydrometer (specific gravity)--if you have flooded cell batteries. Also a Battery Monitor is really nice too (Victron Energy makes a couple with good reviews here on the forum too)--Almost a requirement for AGM/Sealed Batteries (no specific gravity measurements).

Considering that I wish to have more money to make a bigger system, the calculations for the house to be usable are around 220Ah per day, 2.5 KWh/day, using the house everyday to live in (is not a weekend cabin).

Sepcificaly, at what voltage 220 Amp*Hours per day (12/24/48/230 etc.)?

I'll get a generator for backup, but my idea is to use it as few as possible in the future...

My suggestion is to plan the system to run from solar for ~9 months of the year... Depending on your local weather conditions, trying to run 12 months of the year require too large of an array--vs running a genset and fuel costs.

Doing a little comparisons between oversized array vs genset backup on a spread sheet to compare will help you figure out what will work for you (if you have "gloomy winters", almost no solar array will produce enough power. If you have good/clear winters with a few days of stormy weather every so often--just running the genset every second early morning to get the batteries back to 80-90% state of charge will carry you through bad weather nicely and with efficient fuel usage).

So, my questions are:

1 - Do these calculations make sense, considering the loads I estimated for our living?

A 100 kWH per month (~3.3 kWH per day) seems to be enough power to run a normal home (lights, TV/Radio, some well pumping, even a clothes washer) pretty well. Of course, you need to look at conservation closely... A 2 meter flat screen TV with a DVR/Satellite Receiver and a large Desk Top Computer is going to use a heck of a lot more power than a 21" LCD monitor/TV running on a Laptop computer.

So, your 2.5 kWH per day system seems very reasonable.

2 - Should I go with a 12V or 24V system?
I have a concern with the inverter, as finding affordable 24VDC-220VAC is not that easy, for a 600W pure sine inverter which is far more than what we need for now.. for bigger-bigger loads we would run them thru the generator or get a cheaper modified sine in the future.

I like to 1) define the loads, then 2) define the battery bank... From that point everything pretty much falls out.

Load wise--What is your peak wattage (average loads, pump starting loads, etc.)... Roughly, if you are 1,200 watts or less, you can pretty much stick with 12 volt system--If that makes sense for you (some folks use 12 volt car/truck/Recreational Vehicle) devices/appliances/electronics/pumps/etc. because they are cheap and plentiful.

If your wattage is in the 1,200-2,400 watt range or so (deep well pump, larger battery bank and solar/generator charging), a 24 volt system makes more sense. I like to recommend keeping the average DC current to around 100 amps maximum or so--keeps wiring/switches/breakers/fuses/etc. reasonable size/costs.

For example a 1,200 watt AC inverter on 12 volts would need:

• 1,200 watts * 1/10.5 volts cutoff * 1/0.85 eff * 1.25 safety factor fuses/wiring = 168 Amp minimum 12 volt branch circuit

You would round up to 175/200 amps to run the inverter at its rated load.

And, battery bank wise, there are several ways of sizing the battery bank. First is 1-3 days of "no sun" plus 50% maximum discharge (for long life)... for a 2.5 kWH per day system you would get (assuming 2 day of no sun):

• 2,500 WH * 1/12 volt battery * 1/0.85 inverter eff * 2 days no sun * 1/0.50 max discharge = 980 AH @ 12 battery bank

Assuming a 600 watt maximum inverter with 1,200 maximum surge, I would suggest a C/0.4 maximum rate of discharge:

• 1,200 Watt * 1/12 volt * 1/0.4 max surge rate of discharge = 250 AH @ 12 volt minimum battery bank rating

So, in this case, your battery sizing is based on the average power usage per day.

3 - What charge controller should I get, MPPT or PWM, and what Amp rating? In this amount of power I'm planning, is a MPPT useful?..
I wish I could go for the MS TriStar 45A MPPT, that would cover all of our needs.

MPPT charge controllers are great if you have a long run from the solar array to the battery bank/battery house (you can run higher array voltage and smaller array wiring).

Also, they are great for matching "non-standard" solar panels to your battery bank voltage. Very often, solar panels >100 Watts are not Vmp~17.5 volts but usually much higher voltage. The big market for solar panels is solar Grid Tied systems which use "higher voltage" solar panels--which makes them much cheaper than Vmp~17.5v panels

If you have a short run from Array to Battery bank and you can get Vmp~17.5 volt panels (assuming 12 volt system) at a good price--Then PWM controller can be fine for your needs.

In general, arrays less than 200 watts are fine with PWM. And arrays over 400 watts may make more sense with a MPPT charge controller.

We could make an effort and buy it if it makes really difference, but a non-MPPT is less than half off the price. As we are short of money and things are expensive we have to make the best use possible of the resources. So if the MPPT will save me from buying another pv or make a real difference at the end of the day, then we would consider it.

In the end--You will need to do a "paper" design and costing for both systems--and see what the results are.

MPPT controllers are very nice--if you use them where they have strengths (matching higher voltage arrays to lower voltage battery banks). If you do not need that--then MPPT controllers tend to just run the system design costs up for not much return.

4 - in case we can't buy the panels all together, but expanding the system over time, then probably the panels will have different specs...Would be a good choice to get two smaller charge controllers instead of one-big controller, so then I can group the panels in two arrays by their specs?

You might have to do this anyway... Panel availability/specifications are changing so often that 1-2 years later you may not find any matching panels to mate with your existing array.

5 - Related to 4), Can I mix PWM and MPPT and both together charge a single battery bank?

Should not be a problem. Just keep the cable runs from each charge controller to the battery bank short and heavy. (each controller should have its own Controller to Battery bank run--do not share one run with multiple chargers--they may confuse each other and reduce your charging current).

6 - Related to 4), if I group all the panels in one array, then for an array having panels with slightly different specs, is PWM or MPPT better?

If you can match parallel connections to Vmp within 10% and series connections Imp ratings to within 10%--then that is just about a "perfect" match.

The farther away you get from the 10% match point, the more losses/issues you will have.

Hope I helped/made sense.

I did not discuss the sizing of the solar array / generator charging yet... You need to do that side of the paper design first before buying any hardware (to ensure efficient use of your money, good battery bank life, and good fuel efficiency).

We can save that for the next set of posts.

-Bill

Galecra

Re: Planning South America Off-Grid Installation. Some questions.

I would also add "tools" to that list...

Yes, I'm looking forward for a AC DC clamp meter with reactive-active and cosfi (just for the fun of it)...
Regarding the battery monitor, I'll use what the controller has, or get some cheap digital ammeter and voltmeter here in Argentina...

I'll try to avoid flooded batteries, going for the sealed/agm options or see what I can get in my country (getting batteries back from USA is not an option)

Sepcificaly, at what voltage 220 Amp*Hours per day (12/24/48/230 etc.)?

220Ah at 12V.

Doing a little comparisons between oversized array vs genset backup on a spread sheet to compare will help you figure out what will work for you ...

In general, we have clear winters...
Here (we use litters), it is around 1.3u$s a litter, and the generator uses around 1litter/hour. Very general, if I have to run the generator 2hs each day, by the end of the month I have spent around 60u$s. I can get a used 50W panel for u$s250, so using the generator half of the year that frequently I pay for another panel.
I understand that avoiding the generator by using pvs will be too costly, but I expect in the future to be able to run the "regular" days without the generator, leaving the generator for time-to-time heavy loads, hard winter days, or strings of cloudy days...


So, your 2.5 kWH per day system seems very reasonable.

I like to 1) define the loads, then 2) define the battery bank... From that point everything pretty much falls out.

Load wise--What is your peak wattage (average loads, pump starting loads, etc.)... Roughly, if you are 1,200 watts or less, you can pretty much stick with 12 volt system--If that makes sense for you (some folks use 12 volt car/truck/Recreational Vehicle) devices/appliances/electronics/pumps/etc. because they are cheap and plentiful.

Our loads are:
Mostly electronics (a couple of notebooks which we work with almost 10hs/day, a wifi router 10hs/day, a modem 10hs/day, the DirecTV converter 5hs/day, a music radio and deskjet printer just sometimes, the cell phone-shaver-battery-digital camera chargers 6hs/day). I measured around 1amp in 220AC connecting all of them together at the same time.
Water pumping, for which I'm considering some SHURflo models, to lift water from a ground cistern (filled by a truck bringing us water once every 2 months) up to a tank 30-40 feet higher than the cistern. We are only two persons, adults, used to live with "what we have", so a pump with 1-2 GPM will be enough if it runs a couple of hours each day. What I have seen from SHURflo it's around 4-5A 12VDC.
Some led lamps.
A floor or roof fan for the very hot summer days.
The regulator and inverter.
Some ghost loads,
and maybe some thing we would use from time to time like sewing machine 0,5A 220VAC, some little tool, etc.. let's say a couple of times/week.

No TV (we use the notebook), no microwave, no clothes washer, no air conditioner, no bread maker, no coffe maker... I think the refrigerator will be propane powered, as doing it electric will required a 2x solar power system...
For heating we will use wood and kerosene (which is normal here).
For water heating we will use a solar water heater (which work really well here), and gas heated water as backup.

If your wattage is in the 1,200-2,400 watt range or so (deep well pump, larger battery bank and solar/generator charging), a 24 volt system makes more sense. I like to recommend keeping the average DC current to around 100 amps maximum or so--keeps wiring/switches/breakers/fuses/etc. reasonable size/costs.

For example a 1,200 watt AC inverter on 12 volts would need:

For what you say, a 12VC would be ok for us.
I calculated around 420W using everything at the same time, and considering the water pump is 12V (and I could make some led lamps 12V as well) the power required in the inverter for a "regular" day would be even less than 400W.
So a 600W pure sine will be fine most of the time for now, leaving the heavy loads to the generator.
Here I have a couple of questions:
1 - For these kind of loads, is a pure sine really a better choice, or a modified would work just fine?, considering finding 230VAC pure sine is not easy in the <=800W range, and they are much more expensive than modified ... Here in Argentina pure sine almost do not exist, only for inverters >3000W or so... that's why if it is a real improvement, I was thinking on buying in USA a low power pure sine (let's say 400-600W), and then if I need more power then get here a cheaper modified bigger one...
2 - Most of our loads are really DC loads (notebooks, router, modem, charger, etc) working in different voltages... is there a way / adapters to use DC directly for these appliances? I mean for example, my notebook charger is prepared to plug into AC, if I want to run it DC I have to find another charger.. same for the router, etc...

And, battery bank wise, there are several ways of sizing the battery bank. First is 1-3 days of "no sun" plus 50% maximum discharge (for long life)... for a 2.5 kWH per day system you would get (assuming 2 day of no sun):

Your battery estimation is similar to the one I calculated...
Considering 2 no-sun days and 60% discharge (we need to save money :-)), I got 750Ah-800Ah.

MPPT charge controllers are great if you have a long run from the solar array to the battery bank/battery house (you can run higher array voltage and smaller array wiring).

I can't tell this as the house is not built yet.. but it is a rather open place and I can put the panels close to the house.

Also, they are great for matching "non-standard" solar panels to your battery bank voltage. Very often, solar panels >100 Watts are not Vmp~17.5 volts but usually much higher voltage. The big market for solar panels is solar Grid Tied systems which use "higher voltage" solar panels--which makes them much cheaper than Vmp~17.5v panels

If you have a short run from Array to Battery bank and you can get Vmp~17.5 volt panels (assuming 12 volt system) at a good price--Then PWM controller can be fine for your needs.

Well, in Argentina solar power is in dippers, and things cost more than gold... the most common panels found here are 17.5 Vmp, 21.7Voc, up to 85W (85W is rare)..., I'm trying to double check if I'll be able to bring with me panels from USA (as airline luggage).. if not then probable I'll need to buy the panels here.

MPPT controllers are very nice--if you use them where they have strengths (matching higher voltage arrays to lower voltage battery banks). If you do not need that--then MPPT controllers tend to just run the system design costs up for not much return.

I see a good point with MPPT that I'll be able to use more variety of panels, and get as much as possible power from them, even with 17.4 Vmp.
if I use 17.4 Vmp panels, will mppt make a good worth difference? .. as I said, panels and stuff are really expensive here, so making good use of the resources is very important. I see the difference between a 45A PWM and a 45A MPPT Morningstar is 200u$s .. I would by 20W-25W pv with that here.
One of my main concerns is with the controller, as I don't know yet if going for one 45A mppt, or one smaller mppt and one smaller pwm for future expansions, or one 45A pwm, or two smaller pwm ...

Should not be a problem. Just keep the cable runs from each charge controller to the battery bank short and heavy. (each controller should have its own Controller to Battery bank run--do not share one run with multiple chargers--they may confuse each other and reduce your charging current).

By "run" I understand the wiring between the controller and the battery bank, you mean to wire the controllers separately up to the point where they reach at the battery bank to make a parallel connection ...

If you can match parallel connections to Vmp within 10% and series connections Imp ratings to within 10%--then that is just about a "perfect" match.

The farther away you get from the 10% match point, the more losses/issues you will have.

When there is such a difference, or worse... which controller will work better, PWM or MPPT?

BB.

Re: Planning South America Off-Grid Installation. Some questions.

Galecra wrote: »

Yes, I'm looking forward for a AC DC clamp meter with reactive-active and cosfi (just for the fun of it)...
Regarding the battery monitor, I'll use what the controller has, or get some cheap digital ammeter and voltmeter here in Argentina...

I'll try to avoid flooded batteries, going for the sealed/agm options or see what I can get in my country (getting batteries back from USA is not an option)

At least in the US, AGM's are 2x or more expensive than flooded cell, and many times, will not even last as long as flooded cell.

Yes AGM is more efficient (90-98% vs 80-90% for flooded cell)--So you would need ~10% larger array to account for extra losses.

If you have problems obtaining several gallons of distilled water (or filtered rainwater, deionized water) per month--Or you have a need for "clean/no acid fumes batteries--then AGM may be worth it for you...

Plan on avoiding Gel batteries--they can be easily damaged from too much charging current.

220Ah at 12V.

you are looking at 10-28 amps of charging current--so your choice of charge controllers is pretty easy.

MorningStar controllers are pretty nice. You might also want to look at the Rogue 30 amp 12/24 volt MPPT controller. Includes the digital display in base pricing.

In general, we have clear winters...
Here (we use litters), it is around 1.3u$s a litter, and the generator uses around 1litter/hour. Very general, if I have to run the generator 2hs each day, by the end of the month I have spent around 60u$s. I can get a used 50W panel for u$s250, so using the generator half of the year that frequently I pay for another panel.
I understand that avoiding the generator by using pvs will be too costly, but I expect in the future to be able to run the "regular" days without the generator, leaving the generator for time-to-time heavy loads, hard winter days, or strings of cloudy days...

Roughly, you should be getting around 3kWH to 5kWH per 4 litters of petrol.

If you can monitor the kWH generated (with some sort of 230 VAC kill-a-watt meter) and compare that to fuel used--you should be able to quickly identify your "fuel efficiency" and figure out the best way to charge your battery bank (and you may have to look at different AC charge controllers to find the optimum for your needs).

Our loads are:
Mostly electronics (a couple of notebooks which we work with almost 10hs/day, a wifi router 10hs/day, a modem 10hs/day, the DirecTV converter 5hs/day, a music radio and deskjet printer just sometimes, the cell phone-shaver-battery-digital camera chargers 6hs/day). I measured around 1amp in 220AC connecting all of them together at the same time.

If you can find one of these Morningstar True Sine Wave inverters in 230 VAC 50 Hz (300 watt continuous, 600 watt for ~ 10 minutes)--These are really nice inverters for the price and functions they support ("low power search/standby mode"; remote low voltage switch DC on/off input).

Put the "good/expensive" TSW on your electronics, wall transformers, cell/battery AA battery chargers, etc... And get a big old cheap MSW inverter to power your hand drill, mixer, etc.

So, yes, for living off grid, I would highly recommend TSW inverters for your critical loads (sensitive, would hurt you if they failed, etc.) and use MSW for your "don't care" loads and simple universal motor hand tools, sump pump, etc..

All About Inverters
Choosing an inverter for water pumping

You can check with our host NAWS to see if they can get the 220v/50hz Morning Star inverter... Or you can try SunElec too (they export a lot to the Caribbean--I think--too). Note, other than helping to moderate this forum for NAWS--none of us moderators have any business connections with either vendor.

Water pumping, for which I'm considering some SHURflo models, to lift water from a ground cistern (filled by a truck bringing us water once every 2 months) up to a tank 30-40 feet higher than the cistern. We are only two persons, adults, used to live with "what we have", so a pump with 1-2 GPM will be enough if it runs a couple of hours each day. What I have seen from SHURflo it's around 4-5A 12VDC.

SHURflo and others make some very nice pressure pumps that will work on 12 (or 24) systems very nicely. You should not need an AC pump.

Some led lamps.
A floor or roof fan for the very hot summer days.
The regulator and inverter.
Some ghost loads,
and maybe some thing we would use from time to time like sewing machine 0,5A 220VAC, some little tool, etc.. let's say a couple of times/week.

Normal living stuff--should not be a problem. The "ghost loads"--put them on a power strip and turn them off when not needed (unplugged cell/battery chargers, turn off TV/Satellite receiver/networking/printers when not in use, etc.).

No TV (we use the notebook), no microwave, no clothes washer, no air conditioner, no bread maker, no coffee maker... I think the refrigerator will be propane powered, as doing it electric will required a 2x solar power system...
For heating we will use wood and kerosene (which is normal here).
For water heating we will use a solar water heater (which work really well here), and gas heated water as backup.

Look around for a 1 kWH per day 220 VAC refrigerator. Living there year round--It may be worth it to you to increase the system size to support the extra loads (when you take propane costs and fridge maintenance into account).

One of the "interesting projects" is converting a chest freezer to refrigerator... Can get cooling loads down to 250 WH per day (note: may not be "spouse" friendly).

Chest freezer as a chest refrigerator

For what you say, a 12VC would be ok for us.
I calculated around 420W using everything at the same time, and considering the water pump is 12V (and I could make some led lamps 12V as well) the power required in the inverter for a "regular" day would be even less than 400W.
So a 600W pure sine will be fine most of the time for now, leaving the heavy loads to the generator.
Here I have a couple of questions:

Perhaps two of the Morning Star 300 watt TSW inverters would be worth it for your too... Lots of people use the 120 VAC versions here and love them (I am on-grid, so I am just relating comments from the others here).

1 - For these kind of loads, is a pure sine really a better choice, or a modified would work just fine?, considering finding 230VAC pure sine is not easy in the <=800W range, and they are much more expensive than modified ... Here in Argentina pure sine almost do not exist, only for inverters >3000W or so... that's why if it is a real improvement, I was thinking on buying in USA a low power pure sine (let's say 400-600W), and then if I need more power then get here a cheaper modified bigger one...

Good Plan

2 - Most of our loads are really DC loads (notebooks, router, modem, charger, etc) working in different voltages... is there a way / adapters to use DC directly for these appliances? I mean for example, my notebook charger is prepared to plug into AC, if I want to run it DC I have to find another charger.. same for the router, etc...

Sending 12 VDC very far is difficult. Lots of voltage drop issues, heavy (expensive) copper wire and such. Also, a solar PV deep cycle battery system will run from 10.5 volts to 15 volts or so... Some DC power adapters (computer / car adapters) seem to blow up if subjected to more than 14.2 volts or so.

Personally, I really like the MorningStar TSW inverters and 120/220 VAC power. Simple AC distribution wiring and the inverter in "search mode" will turn on when >6 watt AC loads are turned on (many folks leave inverter "in search" and just turn on the AC loads directly).

Your battery estimation is similar to the one I calculated...
Considering 2 no-sun days and 60% discharge (we need to save money :-)), I got 750Ah-800Ah.

If you need to save money (who doesn't)---Look at flooded cell batteries and even used forklift batteries.

Forklift batteries will use more water and are a bit less efficient--but can be very rugged and long life (and still decent life if purchased used from a reliable source).

Well, in Argentina solar power is in dippers, and things cost more than gold... the most common panels found here are 17.5 Vmp, 21.7Voc, up to 85W (85W is rare)..., I'm trying to double check if I'll be able to bring with me panels from USA (as airline luggage).. if not then probable I'll need to buy the panels here.

Under 100 Watt panels tend to be very expensive... The 125-135 watt panels seem to be about the maximum size that can be shipped without special considerations.

Obviously, the cost for shipping / insurance to your front door (from whatever the source) is the end cost for you...

MPPT vs PWM controllers... Design the rest of the system first, then see what controllers will better address your needs.

In general, using Vmp~17.5 volt panels--then a MPPT may be 10-15% more power IN COLD WEATHER (near freezing and below). For hot weather, there will be little increase in output (Vmp voltage falls as panels get hot).

By "run" I understand the wiring between the controller and the battery bank, you mean to wire the controllers separately up to the point where they reach at the battery bank to make a parallel connection ...

Yes, "home run" each controller to the battery bank (or Star Connected with the battery at the center of the star, etc.).

Sorry, English is my only language--and obviously, I am not very good at it either. :roll:

When there is such a difference, or worse... which controller will work better, PWM or MPPT?

MPPT are great choices if you need the high array / non-standard array voltage input. And MPPT controllers have more options (remote panels, more programming options, some even have networking/Ethernet connectivity, etc.).

-Bill

Galecra

Re: Planning South America Off-Grid Installation. Some questions.

Thanks again for your answer...
I have been researching a bit, and I'm considering the option of buying the solar cells kit and doing the panels myself.. That way I'll be able to buy the kits in USA and bring them with me to Argentina on the plane with no problem...
Do you have any experience building the panels yourself? is it really difficult to make it work?...

I'll research about the Morningstar inverter, I think is a good option, looks like a good product... a little bit short of power for my needs but I'm designing to have a parallel inverter for the heavier loads...

Do you know the Blue Sky charge controllers? Do you have good comments about them? .. I see they have some MPPT models at good prices, like Blue Sky Solar Boost 2512i or Blue Sky Solar Boost 2000E 12V

If I'm gonna make my own panels, I think a MPPT perhaps is better, as the output voltaje of the panels could not be the best match.. and as building the panels myself is cheaper I'll be able to get some more W as if I had to pay for the industry made panels..
This is the point where I'm still not sure about... I know I'll probably need more than 30A for the controller... I don't know yet about getting
1) one PWM 45A controller...
2) two smaller PWM controllers, one with load control so I connect the water pump and a few led lamps to it.
3) one MPPT 45A controller , or one MPPT 30A controller hopping not getting short.
4) one smaller MPPT, and one smaller PWM so I connect the water pump and a few led lamps to it.

BB.

Re: Planning South America Off-Grid Installation. Some questions.

Galecra wrote: »

Thanks again for your answer...
I have been researching a bit, and I'm considering the option of buying the solar cells kit and doing the panels myself.. That way I'll be able to buy the kits in USA and bring them with me to Argentina on the plane with no problem...
Do you have any experience building the panels yourself? is it really difficult to make it work?...

Please do not make your own panels... They will not last (weeks/months/maybe a year). There are lots of issues and many of the raw cells (some/most/all?) are seconds and rejects from regular panels. There can be issues with using these reject panels.

If you want/need to build your own, here is a set of threads on another forum that made some very professional looking panels (any good, I have not a clue):

Oztules' series:

http://fieldlines.com/board/index.ph...,144982.0.html
http://fieldlines.com/board/index.ph...,144995.0.html
http://fieldlines.com/board/index.ph...,145004.0.html

I'll research about the Morningstar inverter, I think is a good option, looks like a good product... a little bit short of power for my needs but I'm designing to have a parallel inverter for the heavier loads...

Most off-grid inverters cannot be "paralleled" (stacked) to support larger loads. If you mean parallel several inverters from a single battery bank to supply multiple (smaller) loads--that is fine.

Do you know the Blue Sky charge controllers? Do you have good comments about them? .. I see they have some MPPT models at good prices, like Blue Sky Solar Boost 2512i or Blue Sky Solar Boost 2000E 12V

I would suggest to stay away from them... Some known issues with them. They sort of work OK but (in general) appear to be older designs and are barely acceptable in many uses (I am on grid--just years of reading other's opinions here).

If I'm gonna make my own panels, I think a MPPT perhaps is better, as the output voltaje of the panels could not be the best match.. and as building the panels myself is cheaper I'll be able to get some more W as if I had to pay for the industry made panels..

Please do not. You can try making a couple and see how they work out for you (years of wind/rain/sun) and decide to make more or not. Also, try to avoid flammable materials (wood, plastic panels, etc.). Solar panel failures and fires (home made) are fairly common.

This is the point where I'm still not sure about... I know I'll probably need more than 30A for the controller... I don't know yet about getting
1) one PWM 45A controller...
2) two smaller PWM controllers, one with load control so I connect the water pump and a few led lamps to it.
3) one MPPT 45A controller , or one MPPT 30A controller hopping not getting short.
4) one smaller MPPT, and one smaller PWM so I connect the water pump and a few led lamps to it.

Not quite sure how you are planning on using load control--but in general, load control (voltage based) is not very accurate and in many cases, is set too low (below ~11.5 volts) and ends up killing batteries anyway.

-Bill

Galecra

Re: Planning South America Off-Grid Installation. Some questions.

Still researching on panel options...

Do you know the amorphous flexible solar panels? like this one: Uni-Solar Laminate 124 Watts 30.00Vmp $208.32
That's easier to carry on as luggage, and even at that price is much cheaper than regular panels down here in Argentina... I can then put those laminates on the roof or another surface.. though they are pretty large..
Ar they weather proof? do they last long?.. I see a good point on them not having glass or breakable things...


Regarding the inverters, do you know the PowerBright brand? They do make 12VDC-230VAC converters modified sine waive at a good price. I'm thinking on getting one Morningstar 220VAC inverter for the regular loads <300W , and another bigger and cheaper PowerBright to connect the heavier loads...

Also, as most of our loads (laptops, chargers, etc) have international adapters which run with 120VAC or 230VAC, I'm thinking getting a 12VDC-120VAC inverter is also a good choice, and then I can buy here a transformer 120VAC-220VAC for the few loads that must run with 220VAC..


Directly connected to DC I would have the water pump, and maybe a couple of lights... how would I connect them?, just directly to the battery (I don't think it would be a good idea)? or do I need some sort of controller or voltage regulator between? That's what I meant in my previous message on using the load control outputs of the charge controller to connect the water pump..

BB.

Re: Planning South America Off-Grid Installation. Some questions.

Galecra wrote: »

Do you know the amorphous flexible solar panels? like this one: Uni-Solar Laminate 124 Watts 30.00Vmp $208.32
That's easier to carry on as luggage, and even at that price is much cheaper than regular panels down here in Argentina... I can then put those laminates on the roof or another surface.. though they are pretty large..
Ar they weather proof? do they last long?.. I see a good point on them not having glass or breakable things...

With amorphous panels--typically they are about 1/2 as efficient as mono/poly crystalline panels--so you need ~2x the square meter area for the same amount of power.

Personally, I am not a big fan of amorphous/plastic/flexible panels unless you have a real reason for them--perhaps yours is a good reason (shipping size/costs).

While I am not sure that the UniSolar (and others) will last as long as glass panels--given that my own "Grade A" glass panels from a reputable mfg. needed to be replaced in about 5 years--I will not make any predictions for you.

Regarding the inverters, do you know the PowerBright brand? They do make 12VDC-230VAC converters modified sine waive at a good price. I'm thinking on getting one Morningstar 220VAC inverter for the regular loads <300W , and another bigger and cheaper PowerBright to connect the heavier loads...

Also, as most of our loads (laptops, chargers, etc) have international adapters which run with 120VAC or 230VAC, I'm thinking getting a 12VDC-120VAC inverter is also a good choice, and then I can buy here a transformer 120VAC-220VAC for the few loads that must run with 220VAC..

You can get good (expensive) MSW inverters too--or stick with cheap and locally available that meet your needs. For a off-grid live/work situation (9+ months a year), spending money on "good inverters" with remote heads, various power saving/monitoring features are pretty nice to have.

However, by the time you pack them for Argentina (or buy local)--They simply may not be worth it for you.

Regarding using a transformer--I would suggest avoiding using them, if possible. Transformers are not usually very good for use on MSW inverters (lots of losses) and even on TSW inverters, you may end up with 5% or more in losses.

Certainly will not hurt to try--but measure your DC power into the inverter and see if you can tolerate any additional power usage/losses by using these guys (and, for example, you may find that "search mode" will not work with a transformer on the AC output).

Directly connected to DC I would have the water pump, and maybe a couple of lights... how would I connect them?, just directly to the battery (I don't think it would be a good idea)? or do I need some sort of controller or voltage regulator between? That's what I meant in my previous message on using the load control outputs of the charge controller to connect the water pump..

Tough question to answer. In general, low voltage disconnects have limited current support (~8-30 amps depending on manufacturer and model).

And, measuring battery bank voltage to estimate state of charge is not very accurate. Plus you have more voltage drop through the extra hardware and wiring.

Is this going to be an unattended system/pumping at times and you need to protect the battery bank?

Setting up a system for unattended operation can get complex and expensive.

If you/family are always going to be there--then you can cycle pump power as needed and save the money/complexity.

-Bill

Galecra

Re: Planning South America Off-Grid Installation. Some questions.

your panels were under warranty, right?... I should check in case I pack them to another country, if the warranty will still apply ...

I think these flexible panels will be easier to pack, even I can put them inside my luggage...
I see that they require more space than a glass panel for the same amount of power, I think I'll need to handle that if I want to get the other benefits...
I'm reading that these panels are good for hot conditions as they do not lower the voltage that much, and they do not have glass.. the house will be in a rather hot area with some heavy stone ice storms from time to time, so these could be good points...


Regarding the pump, yes, there will always be someone at home to turn it off/on when needed. My concern is if connecting the pump directly to the battery bank will be ok, or if something in the middle like a voltage regulator or load control is needed.
If the pump can be connected directly to the battery bank, then I'll put a flood switch (don't know how to say it) in the tank so it's stop pumping when the tank get's full, and monitor the battery charge manually periodically and if voltage to low then turn the pump off...