Installing in Nicaragua

Wilis

Hi,
I ask a few questions a week or so ago about a solar install in Nicaragua. The system is in a container on a boat going there now. I did not design or order this system. This system is 30 CS6P-230P PV’s.

Pmax 230W
Vmp 29.6V
Imp 7.78A
Voc 36.8V
Isc 8.34A

The company has included 2 CC XW-MPPT60-150. The Voltage will be 48v. The batteries are 16 US Battery US 305XC 6V 310W. Two Strings of 8 for the 48V.
I have looked on the Xantrex calculator to see how they would set up the PV’s because the company that sold the system has told me to hook up 6 strings of 5 PV’s. This looks like over voltage to me. I email them and they said it would be ok because of the poor sun in Nicaragua. I have been there and feel we will get good sun but have not measured it. What does the experts think about this install.

niel

Re: Installing in Nicaragua

i tend to agree with you as 5 x 36.8vmp = 184v and is far above the max for the xw. with 4 this will be under the max rating of the controller, but that leaves 2 pvs out of the mix unless 2 more are bought to be seriesed with them. 8 strings of 4 or 7 strings of 4 are workable. sg was involved with the design of the xw so he will have the final opinion if he differs here.

Wilis

Re: Installing in Nicaragua

Thanks Niel for the quick reply but PV's don’t fit in suitcases. I will be willing to run less PV's on this system if that is what is best. We seem to have enough PV to run our load and charge batteries and do have a gen for backup. We have other building that could use a PV or 2 for lights. With the mission and foreign countries it is harder to change and get parts. That is way I am trying to think about this now before I get there. I will be waiting to see what others think. Wilis

AntronX

Re: Installing in Nicaragua

Connect 3 panels in series x 5 = 15 panels total per each controller.

3 x 29.6 V = 88.8 V (at 25 degrees C panel temperature)

88.8V x 80% = 71 V (at summer temperatures + some wiring losses)

14.5 V x 4 = 58 V (highest system voltage during charging)

71 V / 58 V = 1.22 / 1 (good input / output ratio, will keep controller operating at maximum efficiency)

230W x 15 x 80% x 97% = 2,667 W per controller

2667 W / 48 V = 56 A (charge controller current worst case scenario at summer temperature)

Windsun

Re: Installing in Nicaragua

Wilis wrote: »

I have looked on the Xantrex calculator to see how they would set up the PV’s because the company that sold the system has told me to hook up 6 strings of 5 PV’s. This looks like over voltage to me. I email them and they said it would be ok because of the poor sun in Nicaragua. I have been there and feel we will get good sun but have not measured it. What does the experts think about this install.

Nicaragua... poor sun?? The yearly average insolation there is 5.7.

Are those people idiots? I have not been there for 30 years, but unless the sun has changed since then, it is pretty intense anyplace away from the jungle or palm trees. It can get rainy there, but that would have nothing to do with the max panels in series.

As you may have figured out, you will need 3 XW controllers to run the system, not two. The max amperage could be nearly 150 amps, and those are limited to 60 amps each.

Wilis

Re: Installing in Nicaragua

Below is the information I received from the company that designed this system. See post 1. Please if you are selling and installer solar equipment don’t tell your customers something that is not true. If you don’t know find out before you tell them anything. I have wired many homes and have a 2 year electronic degree but no solar experience. About 6 months ago I decided to install a home solar system that NAWS helped me design. They could have sold me most anything but worked with me to get a system when I told them what I wanted to do with it. I have learned so much from this experience and from this forum.
If you are just starting out find a company that will help and be there after some of the rest are gone.


Company name removed.

The interconnection of the XW with the charge controllers is covered in the XW Installation Instructions starting on page 81. You will see that the conductors from the string combiner are connected to terminals inside the XW PDP, through the internal DC breakers to the the charge controllers. Wiring the array in six strings of 5 modules will provide the optimal charge output to the batteries under optimal conditions. This configuration is not optimal for straight power production, but for your purposes, this is the best we can do. In the U.S., the CSI modules should produce around 29 volts most of the time. This means the DC output of one string should be approximately 145V, within the operating specs of the SCC. However, the open circuit voltage of 5 modules DOES exceed the 150Voc rating of the controllers. Most likely, this will never be an issue where they will be installed as the mean temperature and irradiance in Nicaragua have, historically, never coexisted at levels that would produce the kind of voltage that would overload this system. March and April are the hottest months and also have the highest irradiance in Waspam (about 5.5k/M²). These conditions are, frankly, not very good for producing electricity, but what can you do? I had to balance maximum production with system safety. Sincerely, I believe that a 5-module string will produce less than optimal voltages, but I cannot safely recommend a 6- module string. I strongly recommend using the 5-module string, at least for the first 6 months or so. If the voltage levels are insufficient to serve the station's needs, the array could be reconfigured to five strings of 6 modules, which would decrease amperage but increase voltage. The output in wattage would be relatively unchanged, but the changes could be better suited under the conditions. Honestly, that was the biggest issue while designing this system. It took me almost 2 months to gather enough data on Nicaragua to become comfortable with the system parameters. But, since I have no specific, accurate data on the station's exact location, I cannot guarantee anything. What I can say for certain is, the system we sent you will be safe and will produce SOME power. How much, I cannot say. Frankly, I would not install this system here in the U.S. With irradiance levels in the winter of around 7 to 8k/M², those modules may not damage the SCCs, but would scram them for sure! But, all the data I could get said Central America never gets above 7k and only on the Pacific coast.

AntronX

Re: Installing in Nicaragua

Wilis wrote: »

Please if you are selling and installer solar equipment don’t tell your customers something that is not true. If you don’t know find out before you tell them anything.

Who are you directing this sentence at? I am a bit confused.


Company name removed.

Wiring the array in six strings of 5 modules will provide the optimal charge output to the batteries under optimal conditions. Yea, but when controller goes into absorption mode, and drops PV current, the PV voltage will go up beyond 150V limit and possibly damage charge controller.


This configuration is not optimal for straight power production, but for your purposes, this is the best we can do. What? What is this nonsense?

In the U.S., the CSI modules should produce around 29 volts most of the time. This means the DC output of one string should be approximately 145V, within the operating specs of the SCC. Yea ok, but what about peak open circuit voltage?

However, the open circuit voltage of 5 modules DOES exceed the 150Voc rating of the controllers. Most likely, this will never be an issue where they will be installed as the mean temperature and irradiance in Nicaragua have, historically, never coexisted at levels that would produce the kind of voltage that would overload this system. Clueless! It will produce that kind of voltage as soon as you connect 5 panels in series together. Even if it's cloudy.

March and April are the hottest months and also have the highest irradiance in Waspam (about 5.5k/M²). These conditions are, frankly, not very good for producing electricity, but what can you do? What? that's not instantaneous but average solar irradiance per day! That value is in no way proportional to PV open circuit voltage! That's how much solar energy a square meter receives in one day, not an instantaneous solar radiative power.


I had to balance maximum production with system safety. Sincerely, I believe that a 5-module string will produce less than optimal voltages, but I cannot safely recommend a 6- module string. I strongly recommend using the 5-module string, at least for the first 6 months or so. You are right, 5 module string will produce less that optimal voltages, because the charge controller will blow up the moment this array is connected to it! It may not last 1 second, let alone 6 months...

If the voltage levels are insufficient to serve the station's needs, the array could be reconfigured to five strings of 6 modules, which would decrease amperage but increase voltage. The output in wattage would be relatively unchanged, but the changes could be better suited under the conditions. Honestly, that was the biggest issue while designing this system. It took me almost 2 months to gather enough data on Nicaragua to become comfortable with the system parameters. Should have spent that 2 months studying how to really design solar systems...

But, since I have no specific, accurate data on the station's exact location, I cannot guarantee anything. What I can say for certain is, the system we sent you will be safe and will produce SOME power. No, the way you propose to wire PVs will blow up the controller

How much, I cannot say. Frankly, I would not install this system here in the U.S. With irradiance levels in the winter of around 7 to 8k/M², those modules may not damage the SCCs, but would scram them for sure! But, all the data I could get said Central America never gets above 7k and only on the Pacific coast. Frankly, I would not install this system the way you propose anywhere on Earth!


To Wilis, I am curious to know who this company is.

Windsun

Re: Installing in Nicaragua

AntronX is correct about what they stated.

I thought this was one of the stupidest statements - he seems to be using big words to create a snow job - irradiance levels of 8k watts/squre meter are what you might get on the sunny side of the planet Venus. He seems to have insolation mixed up with that.

How much, I cannot say. Frankly, I would not install this system here in the U.S. With irradiance levels in the winter of around 7 to 8k/M², those modules may not damage the SCCs, but would scram them for sure! But, all the data I could get said Central America never gets above 7k and only on the Pacific coast.

It is pretty obvious that whoever wrote that is highly ...confused. He is saying that the average insolation is low, and then equating that to lower Voc into the controller, which makes no sense.

Not sure why it took him 2 months to gather data for Nicaragua - it took me about 10 minutes. Notice in the chart link below that the MAX temperature is well below what you get in many areas - in fact it is 20 degrees C less than the max summer temps in Phoenix AZ. That tells me that the Voc will NOT drop near as much as that person predicts.

The biggest factor there, and in many similar locations, is not the temperature, but the amount of rainy/cloudy days during the rainy season, which can severely reduce the total output of the solar array.

http://www.climate-zone.com/climate/nicaragua/fahrenheit/managua.htm

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Wilis

Re: Installing in Nicaragua

Hi again,

I am sorry if I have confused anyone with my post #6. I did not want anyone to think that Naws had anything to do with the company that has not been helpful with my solar install in Nicaragua. Naws was very helpful with my home install and I would recommend then to anyone installing a solar system.
I did not choose or purchase the equipment for the Nicaragua project; I just was offered the challenge of installing it. Being new to solar I wrote the company for information, thinking they should be able to provide instructions. Now I am coming to this forum to see if what I have learned here and from the internet is the best way to install the project. Thanks to everyone that has replied and to anyone that might yet reply. Wilis

BB.

Re: Installing in Nicaragua

Just to be clear, the CSI panels can only be 3 in series unless the temperature never falls below 70F (Voc=148 VDC at 70F).

With 3x series panels Voc=114 volts at 60F and Vmp=71 volts at 100F... Just fine for the controller.

You now have 5 strings with 3 panels each in series or 15 panels per controller... According to panel specs, it will just be at its peak current of 60 Amps. However they will probably average (because of warm weather) closer to 45 amps peak day in and day out. The typical maximum current (perfect weather, cool day) is probably more on the order of 50 amps rather than 60+ amps.

Sounds like other than playing with the wiring--you have the major parts you will need and can get their system operating nicely (with the change in series/parallel solar panel wiring).

You may be missing some way of paralleling the 10 parallel strings together (instead of the planned 6 strings)... You should have a series protection fuse in each string--the CSI spec. sheet did not say, but at Isc=8.3 amps--the series fuse/breaker should be around 18-20 amps (what ever is available in that range).

-Bill

Windsun

Re: Installing in Nicaragua

BB. wrote: »

...However they will probably average (because of warm weather) closer to 45 amps peak day in and day out. The typical maximum current (perfect weather, cool day) is probably more on the order of 50 amps rather than 60+ amps.
-Bill

I am not so sure it will drop that low, what we have found in very high humidity areas, such as that one, that the air has a higher ability to cool the panels (enthalpy), even in direct sun. I don't have any specifics for that, as it depends so much on how much - if any - wind you have. 20 years ago I could have done the calculations, but getting too senile I suppose