Off-Grid System in the Amazon Forest

**Matrix** · 05-02-2019, 03:10 PM

Seems like your choices are solid enough. Have you run sizing calculations to see if the MPPT charge controller can handle 9 panels at 24v? I have 9 285W panels connected to my Midnite solar CC and using the Midnite Solar sizing tool I was real near the max of array size for output and 1 controller.

Do you know what configuration you will run the panels? I assume 3 series 3 parallel. In that case you are supposed to use a combiner box and 3 breakers rated for the panel output because you now have 3 strings. I would use a combiner for ease of service and install anyway. You will be dealing with upwards of 100v +/- DC and a combiner is not a bad idea when used to power the system down for service. cost of a combiner box and breakers is very minimal. I would look at Midnite solar for those options. I might even consider a Midnite Solar E-Panel designed specifically for the SW. This makes install very neat, clean, fast and simple. Provides a location for all necessary breakers and disconnects and makes the system overall more safe from unintentional tampering. The combiner, E-Panel for SW and breakers would add less than $500 to the total install.

Schneider seems to provide the best equilibrium between cost and quality. Is this brand reliable? Since this system operates in remote area, it is mandatory that is a robust design.

I believe it is. Your decision in choosing Schneider is the same reasons I chose Schneider, they seemed to offer the most bang for the buck. And SW is robust especially in small / medium size off grid applications. I wonder though, for the costs, why have you not gone up to the SW 4024 for a larger inverter size and head room. Efficiency loses on paper do not look that much different. And price is pretty close. But the later would allow for more surge and some momentary larger loads. You have not said anything about loads. Is there a pump involved?

**Mike90250** · 05-03-2019, 09:33 PM

ConextSW2524 Inverter/Charger (2500W)

Schneider MPPT 60-150 Charge controller

You will want a System Control Panel, a ComBox or a Gateway, to be able to monitor, control and adjust anything. (listed in order of expense)

**Markhaus** · 05-09-2019, 05:08 AM

Hello!

Thanks for the comments here. I tried the Midnite sizing tool and it is indeed extremely useful. If the budget will allow I was indeed planning to install a ComBox at least, so I can plan future expansions or system adjustments.

At the moment I was also with another, striking doubt about safety. I will review Brazilian regulation with the local Solar company responsible of installation, however on a general level I do not know if providing a 24V or 48V system. May be you can give some nice insights:

1) The Solar system will be installed in an indigenas Amazon tribe in the middle of nowhere. They do not have any clue about electrical safety nor I trust them about not doing dumb things around the system.
2) If I install a 24V system (1500-2000W solar panels of 24V all in paralles with a gigantic combiner box), 24 V battery bank and inverter), I will have a safe to touch voltage, but very dangerous and fire-throwing currents in case they go above 1500W (60A). Also I really do not like the idea of having 1500-2000W of solar panels all in parallel at 24V.
3) If I install a 48 V system and 150V solar panel set-up, the currents will be way more reasonable. However the system it is not safe to touch anymore.

I will stress to the installer to enclose and protect all system component to avoid unintended touch: (separate room, cabinets etc.). Moreover I will limit their system power to 1500W max. for the moment.

Even there, the solar panels will still be at 150V. Can I sleep nicely with a 150V solar panle system in the middle of the amazon? Or indeed is better to have a weaker 1000W system with all panels in parallel? (worst case: a loose cable or some crazy indigenas doing wierd stuff around the panels and the 24V will not give them a shock). On the other hand a 24V system may burn the wood house where is installed... not nice again.

On the table there was also the possibility of using a Schneider MPPT 80-600V, so I can connect all panels in series and get rid of the combiner box (simpler system). way lower currents but now a 600V system.

Any inputs from your experience?

Thanks

Bests

**Matrix** · 05-09-2019, 08:18 AM

You are mentioning and asking opinion about inverter output sizes, but not saying anything about loads. So it's hard to say if a 1000w or a 1500w inverter is enough.
- What will the system be installed for? LED Lights, fans, power tools, refrigerator?
- how many Watt hours do you plan on needing to use per day?

Also, if the indigenous peoples there would possibly damage or destroy the system, do they really need electricity? Why are you installing the system? Will it be for the people who are traveling in to work with the locals?

**BoloMKXXVIII** · 05-09-2019, 10:38 AM

I am one of the most junior members here and have about 0.0005% of the knowledge (or less) of some here, but I can't help but wonder why you wouldn't split up the panels into groups with their own separate charge controllers...all feeding into the same battery bank. You could reduce your voltage and amperage per group in case the locals "do something stupid".

**Markhaus** · 05-09-2019, 04:56 PM

Originally posted by Matrix

You are mentioning and asking opinion about inverter output sizes, but not saying anything about loads. So it's hard to say if a 1000w or a 1500w inverter is enough.
- What will the system be installed for? LED Lights, fans, power tools, refrigerator?
- how many Watt hours do you plan on needing to use per day?

In this cases the system size depends half on what they want and half on what we want to give them. I explain: they need electricity (two computers, internet and light bulbs) but they start from a very bad system of about 1000W. The problem is firstly on poor panel quality (badly oriented, too few and old panels, PWM controller). So anything better/safer than this is a plus.
I could give them a 1000W system and would be enough for them. The thing is that with similar price they could get a 2000-2500W system for future expansion: more computers, more houses with light etc. They do not have easy access to LED light bulbs, so a 1000W system may come quickly short with few more house with light. At the moment only 10 houses have light (assuming at least 600W). About energy consumption: according to my calculations a battery bank of 5 kWh would be enough.

Originally posted by Matrix

Also, if the indigenous peoples there would possibly damage or destroy the system, do they really need electricity? Why are you installing the system? Will it be for the people who are traveling in to work with the locals?

Fair question: these are not isolated indigenas: they have PCs, they do videos, travel, some went to university etc. several villages have their own PV system, but the situation is the same for all: bad quality equipment, unsafe installation, poor maintenance.
As a voluntary project, they asked us a more reliabale system in order to have proper illumination during the evening, keep up their cultural works (videomaking, audio recordings etc).

So here I am: I am the engineer responsible for this project and I want to give the safest and more reliable system possible to them. If I rely only on what suppliers suggest I would end up with some random brand which would break after few months... (someone gave them a MPPT from a low quality manufacture and lasted just a couple of months...).

@Bolo: That is a good idea.
If I connect 4 or 6 panels in parallel for each charge controller ( I will need a PWM though) I can have two ore three chargers with way less current (at least unitl they do not merge in the battery busbar). Still need two or three combiner boxes...

If I decide to connect two parallel strings of 3 panels, I would have something like 120V system. Still 120V so dangerous... I may as well just use a Scnheider 80-600V MPPT, connect 12 panels in series (roughly 550V) and I get rid of combiner boxes.

CONCLUSIONS:
I tried to look for smaller Outback or Studer Inverter/charges: for the same price as for a Conext SW I get half the power. And Schneider is still a quality Inverter... Unless some of you may argue that Studer or Outback are WAY more reliable and definitely worth the extra money given the remote area. At the moment I would put Outback, Studer and Schneider on the same quality and reliability level, even though Schneider has only 2 years warranty... not a good sign.
So I would like a safe to touch 24V battery and inverter system and a 24 V PV system. While I see feasible to get a safe 24V inverter system, I see it very complex to get a 24V PV system of above 1000W...

Moreover, as I will use 12V SLA batteries, getting 5kWh of effective capacity in a 24V system means having three string of batteries in parallel... Not nice.

I hope you enjoyed the long reading and thanks for giving your input here! Cheers

**Matrix** · 05-09-2019, 08:41 PM

Thanks for all the updates. Yes it sounds like the people have some reasons not to destroy the system. And that is good.

But from your loads already listed seems to me your design could already be on the small side. And u say there is a possibility of adding more homes. I would certainly consider the SW 4024 3200 Watt inverter and might even consider a 48v system and the SW 4048. With 48v u could run 8 cheap and readily available 6v 220ah golf cart batteries in series and have over 10kwh of storage and right at your needed 5kwh and not be discharged to 50%.

I'm sure there are social, cultural (needs of the peoples and how responsible they will be with the system) and financial elements (your NGOs budget) to your equation that I don't understand and don't have access too... But food for thought. I'd probably go 48v and design a system that would be more than sufficient to charge those batteries daily.

**Matrix** · 05-09-2019, 08:45 PM

I think a draw to the Outback inverter might be that u can get it in a sealed version. But to have 240v split phase ud have to have 2 of them I think.

As long as the inverter is installed out of the weather and not exposed to crazy dampness etc, the SW is a fine unit for the price

Off-Grid System in the Amazon Forest

Off-Grid System in the Amazon Forest

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