Mountain cabin off-grid

Horsefly

westbranch said:

Huh ?????
Since we don't really know what panels we will end up getting, we may get some of the more square Kyocera panels (66" by 52").
vs
I've done all the math on voltage drop on my wiring to the CC, and I've got a little less than 3% drop....  (Good, but it should be 3%  all the way to the batteries.)
hth

Gee whiz. So is your issue that the voltage drop will change because I may be using either of the two panels I've looked at?  If that's it, I'm below 3% drop in both cases.

I came back to this thread to ask about mounting the PV panels. Do you have any thoughts on that?

westbranch

Mounts, yes, I prefer the KISS concept. strong and sturdy as we have very strong buffeting winds at our place, as we are exposed to the lake at the end of a steep valley that goes all the way to the coast... When Van. Island and the lower coast area was getting those torrential rain storms we got them too..  Winds over 50 Mph and snap directional reversals are common as the winds tumble along the valley sides. I would like a T-o-p mount but I don't think it would survive too long.  Here is a link to a solid well anchored design I like. http://kb1uas.com/mnsforum/index.php?topic=3470.0...  I also will be using this concept for some panels.  http://kb1uas.com/mnsforum/index.php?topic=2511.msg33197#msg33197

hth

Horsefly

Awesome! Thanks @westbranch!  That's a great forum for examples. Like you, I'm not thinking a good ground mount structure will be better than a pole mount.

Thanks again!

Wbuffetjr1

Horsefly,

I have been lurking a long time and closely following your thread. I am putting up a system near you this summer as well.  We have a place at 10,000' between Montrose and Ridgeway.  Maybe you can shoot me an email?? Wbuffetjr!@hotmail.com

Horsefly

Email sent!

Edit: It bounced!  Are you sure about that email address? I didn't think an exclamation point was allowed in an email address.

BB.

Try "1" (one) instead of "!".

-Bill

Horsefly

Thanks Bill. I tried again.

Wbuffetjr1

Haha, good call Bill, it was supposed to be a 1.

Horsefly

It's been a while since I posted about my project. Now that it is up and running, I thought I should post a follow-up. Here's the electronics, in the basement of our cabin:

And here's the PV array ground mount:

The first day we hooked it up the batteries (which we had been using prior to the PV hookup with periodic generator charging) didn't get to float until after noon. For the next several days until I left the cabin, the wife and I did what we could to challenge the system. We took showers at night (causing the well pump to run), warmed dinner in the microwave, she used a curing iron, and we enjoyed lights and cell phone charging, and laptop usage at will. Still, the system returned to float by 11:00am pretty much every day for the 3 days we were there. Oh, and it was raining off and on for two of those days!

I owe a TON of thanks to the people on this forum. You guys are kind, helpful, and smart. Thank you so much for educating me over the past 8 months. We're very pleased (so far) with what we ended up with. 

EDIT - Credit where credit is due: The major electronics (inverter, charge controller, and Midnite E-Panel) and lots of the little things (battery cables, etc) were purchased from NAWS, the forum sponsor. Great prices and great support to my questions. The PV panels and some of the other stuff I found here in Colorado so I could avoid freight costs.

mcgivor

Very nice workmanship indeed, good to hear everything worked out.

Horsefly

Thanks mcgivor. Coming from you, I really appreciate that.

I should say, the little digital meters (purchased for something around $15 each on E-Bay) are really fun to watch. They can't be very accurate, and they don't provide a whole lot more data than is already provided by the Scheider System Control Panel (SCP) and the front panel of the charge controller, but they are fun!

The current shunts for both are mounted in the wireway below all the boxes.

mcgivor

Looks like you are running 3 panels in series, was thinking of doing that, currently I have 2 series, almost have the same setup but with a SW 2524-230, wish everything was available here, have to wait 90 days to get the Schneider DC switchgear to complete the installation. The meter is a nice touch gives some indication of production, do the numbers match the SCP, more or less? 

Horsefly

mcgivor said:

Looks like you are running 3 panels in series, was thinking of doing that, currently I have 2 series, almost have the same setup but with a SW 2524-230, wish everything was available here, have to wait 90 days to get the Schneider DC switchgear to complete the installation. The meter is a nice touch gives some indication of production, do the numbers match the SCP, more or less? 

The numbers are not too far off on either the input to the CC or the output from the CC, except when the current is pretty low, like just as the sun is coming up. The meters continue to say 0.0 for some time, while the SCP and the display on the CC show something less than an amp. Not too bad though.

One issue is that the display can only go up to 100VDC. With my three panels in series and running at an elevation of 8,800 ft, the voltage from the PV array routinely goes above 100V, as high as 108V.  This is especially true when the batteries are in float, which is most of the day. That doesn't harm the meter, but it starts to flash until I clear the alarm. No biggie I guess.  I couldn't find a version that goes above 100VDC.

mcgivor

Without  looking back into previous posts, what distance and wire gauge are you using?

Solray

I'd have gone with 48 volts rather than 12 or 24.

BB.

Very clean install.... Kind of went "big" on your system vs your first post in the discussion.

Looks like it will supply your power needs for a long time to come.

Will you have any issue with "heaving" (ground freezing) with using the ballasts vs post holes below frost line?

Enjoy!
-Bill

Horsefly

mcgivor said:

Without  looking back into previous posts, what distance and wire gauge are you using?

It worked out to be about 170 ft including going down to the ground from the combiner box into the cabin and down the basement wall to the CC.  I did the math using the NEC table. I was shooting for 3% total drop (1.5% on the red and on the black). Using a Vmp for three panels in series of 94.5V and a current (Imp) of two strings in parallel of 17.78A, With 6AWG wire, I came up with a 3% total loss at 75 deg C at a distance of 162 ft. At a more nominal 25 deg C, the total drop of 3% would take me out to 197 ft. For a while it looked like we might be closer to 200 ft so I considered 4AWG wire, but clearly it would have overkill.

Horsefly

Solray said:

I'd have gone with 48 volts rather than 12 or 24.

Not sure what to do with that comment. Good for you, I guess.

I did a significant amount of cost trades, mathematical analysis of loads through the day, and consideration of some ancillary requirements like 12VDC for some loads that are already in the cabin.  I'm guessing you don't know all that.  Anyway, the increased cost for a 48V inverter couldn't be justified, and made some things harder to do rather than easier.  It was considered though.

jonr

I predict it will tip over - at > 88 mph of wind :-).

Horsefly

jonr said:

I predict it will tip over - at > 88 mph of wind :-).

Well, I certainly hope not. It should be OK according to the Snap-N-Rack on-line tool. Although that was set to 90MPH, so maybe you are close. 

With all the cross member bracing and 3,000 lbs of concrete, the thing is pretty rock solid. We don't get much real strong winds up there, except micro-bursts. That pole fence you see behind the ground mount has been there for 42 years (I built it in HS), and I'm not thinking it would still be standing if there was a 90 MPH wind at any time during the last 40 years.  I'll just keep my fingers crossed!

Dave Angelini

Good Job !  Enjoy the showers!  

Horsefly

BB. said:

Very clean install.... Kind of went "big" on your system vs your first post in the discussion.

Looks like it will supply your power needs for a long time to come.

Will you have any issue with "heaving" (ground freezing) with using the ballasts vs post holes below frost line?

Enjoy!
-Bill

Yeah, I was talking with my siblings (partners in this effort) on how it grew. They had added some additional future loads to include, but most of the increase was me doing the analysis over and over. As I've mentioned before, I got the epipphany from reading your posts that it makes more sense to size the PV array according to what you need to charge the battery, rather than base it on the daily energy needs. That (and lower prices for panels) led me to a bigger PV array than I would have imagined.  The PV went from two 300+ watt panels, to three panels, to four panels, and finally to five panels (which had to round up to six to make an array for the MPPT). Funny how that always works.

The well pump by itself drove me to a bigger inverter than we would otherwise need. However, it runs so little during the day (2 min, 40 seconds each time, and generally no more than 3-4 runs in a day) that it doesn't have a huge impact on the battery bank.

We shouldn't have any problem with the heaving. That tends to happen where the soil is a little more moist. The ground up there stays pretty dry, and we don't think the 3000 lbs of concrete will get lifted at all.

We would have preferred deeper concrete piers instead of the ballasts, but it's solid bedrock a few feet down. In fact, my plan for one 8 ft ground rod ended up being two 4 ft rods, and even then I had to use a jack hammer in several different candidate places before we could get them down that far.

Horsefly

Dave Angelini said:

Good Job !  Enjoy the showers!  

Yeah, the only bad news is that I used to be able to tell my wife and daughters they had to take short showers so we didn't run the generator so much. Now my only excuse is the hot water tank!

Estragon

LOL. I get them to help haul the 100lb propane tanks now and again.

Horsefly

Well, we have a fixed 500 gal tank out behind the cabin. I could tell them to go move it, but after a while they would figure that out and I'd need something new. 

Solray

Horsefly said:

Solray said:

I'd have gone with 48 volts rather than 12 or 24.

Not sure what to do with that comment. Good for you, I guess.

I did a significant amount of cost trades, mathematical analysis of loads through the day, and consideration of some ancillary requirements like 12VDC for some loads that are already in the cabin.  I'm guessing you don't know all that.  Anyway, the increased cost for a 48V inverter couldn't be justified, and made some things harder to do rather than easier.  It was considered though.

My system is similar with a few 12 volt loads, I used a 110 ac to 12 volt DC converter for the 12 volt portion. It was pretty straight forward, the other option it a 48 volt dc to 12 volt dc converter made for golf carts, but I wanted to have a little more head room on the 12 volt side just in case.
There are trade offs whatever you decide on. I like the 48 volt set up though and will do the same again on the next project as well.

engineer

Maybe combining solar panels, small residential wind turbines and diesel generator would help. If one component isn't working another would take its place. You don't want to be with no power in winter and in an isolated place.

Horsefly

Solray said:

My system is similar with a few 12 volt loads, I used a 110 ac to 12 volt DC converter for the 12 volt portion. It was pretty straight forward, the other option it a 48 volt dc to 12 volt dc converter made for golf carts, but I wanted to have a little more head room on the 12 volt side just in case.
There are trade offs whatever you decide on. I like the 48 volt set up though and will do the same again on the next project as well.

Obviously a simple 12VDC wall wart could provide the 12VDC from my 120VAC inverter power. That wasn't the point. The inverter we are using can be programmed for start and stop of down times, where it puts itself into standby.  Our design was using a few 12VDC items such as hallway nightlights, phone chargers, etc. so that if we chose to we could use this feature to shut down the inverter every night from 11:00pm to 6:00am or so. This would eliminate tare loss during that period, yet still provide the few things through the night that were needed. Like I said, this was all stuff you didn't know when you made your comment. That's fine.

I did look into 48VDC-to-12VDC buck converters. They are far less common than the 24VDC-to-12VDC converters because of the large market for 24VDC trucks that want to use 12VDC items. Less common mostly meant I was going to be rolling the dice on quality and how hard it would be to replace.

mcgivor

Solray said:

I'd have gone with 48 volts rather than 12 or 24.

We all make choices, some are calculated, others based on what is practical, or both, what one dose has no relevance on what another chooses, circumstances differ, I wanted to go 48v but the Schneider SW 4048 was not available in the local market, so went 24V, I made my compromise, go ahead tell me I was wrong 

Solray

mcgivor said:

Solray said:

I'd have gone with 48 volts rather than 12 or 24.

We all make choices, some are calculated, others based on what is practical, or both, what one dose has no relevance on what another chooses, circumstances differ, I wanted to go 48v but the Schneider SW 4048 was not available in the local market, so went 24V, I made my compromise, go ahead tell me I was wrong 

Ok, if that's what you want. 
I never said anyone was wrong, but if that is what you think I said, then yes, you are wrong.

You could just as easily implied that I was saying that I was wrong because I would have made a different choice, it's all in how you perceive things.

My guess is that no one needs to be told that we all make choices, but you chose to say it anyways, so does that make you wrong?

I also think he made a good choice, just a different one. I have different expectations from a system and that leads to different choices, not better or worse.