My 15.75 x 30 Jemez Cabin

[MountainDon]

A start on the Solar PV system; the pole mount at the bottom of the south slope. Used four inch drill pipe; 1/4 inch wall. Four and a half feet in the ground/concrete; approx 6.5 feet above ground depending if you're standing uphill or downhill. 300 feet to the cabin wall where the batteries and charge controller will be. 



That's the view straight south. Those two small pines may have to go come fall/winter.

[MountainDon]

The fruits of several months worth of labor in thinning trees and cleaning up forest debris. The Burn Pit! It'll be quite a show come winter.

[MountainDon]

We've also got a few scattered small burn piles ready to go in a few open areas. The building paper will keep the core dry. When there's some snow on the ground we'll fire them up and let them burn.



This was taken after a very nice rain.

[MountainDon]

I probably shouldn't say anything for fear of jinxing it, but we're going to get the skid steer either Sunday or Monday and push over some tress and scrap some round to more or less level. Then dig some post holes for the foundation.

[glenn kangiser]

That's one grand throne, Don.

300 feet to the solar is a long way -- Got big wire?  Not possible to put the inverter/batts  there and send 120 AC to the cabin?

[MountainDon]

For the panels I'm using (3 x195 watt in series for 72 volts DC, 8.2 amps, 2% max design voltage drop) number 3 AWG will do the job. Running the calculations for inverting it at the panels/batteries and transmitting 120 VAC doesn't really make much difference considering I'd like to use a 3600 watt inverter so I could run he microwave, toaster and maybe some power tools (small compressor, saws, etc.), from time to time without worrying about over currenting, or having a brown out. Allowing for 20 amps of 120 VAC with a max 5% voltage drop the cable size is 4 AWG; 30 amps it would be 3 AWG. So it doesn't really matter much either way. I'd rather have the batteries up at the cabin.

[glenn kangiser]

I figured you did the numbers - Just thinking -- no plans of ever increasing the amount of panels possibly requiring bigger wire?

Seems unplanned events always creep up on me requiring expansion.

[MountainDon]

One never knows. 

I plan on telling K she can't use any more power than what this system will provide. 






Maybe I can find a coin fed meter to promote conservation?

   

[ScottA]

Good plan Don...you do that.   

[glenn kangiser]

...but wouldn't it be nice if we had a _{insert energy consuming appliance name here} ? hmm   

[NM_Shooter]

Hi Don, looks good!  You do fast work.  You ever pass through Chama? 

The hardiboard that you put up... is that the fiber / concrete stuff?  If so, how do you fasten it along the edges without the nails blowing out chunks on the edge? 

BTW... I visited a high end, off-grid solar / wind / water place in ABQ a couple of days ago.  I didn't know these guys existed.  They do turn key custom engineering for high dollar applications, and also have a showroom for folks like me:

DIRECT POWER & WATER
4000 VASSAR DR N E
ALBUQUERQUE, NM 87107

Do you know of them?

[MountainDon]

Direct Power... I've heard of them but never been there. My neighbor looked into them a few years ago when planning his cabin system. He got turned off by one sales person who seemed to lose interest when he found out that he was only talking about a 500 watt system. He went to Affordable Solar instead and was pleased. That's just one anecdotal story so probably shouldn't count for much.

Chama... I'd like to pay a visit sometime but want to see if I can get my cabin shell up and dried in first.

Hardi-panel... You hit the nail on the head with your question. My only criticism of Hardi-panel is to do with nailing the vertical edges. If the framing is dead on centered the panels overlap the stud by 3/4 inch. Hardi states not to nail any closer than 3/8's inch to the edge. So I was nailing a bit more than the 3/8 figure back from the edge. Even then a had a couple spots where the edge cracked/broke. I "fixed" them with caulk. Now then, this would be no big deal if you were going to place battens over the joints between panels; one of Hardi's recommended methods to finish the seams. In my case it's "just a shed" and I shrugged the damage off. From a distance you can't tell (easily). I caulked all the joints, primed the caulking and then finish painted. I took a cheap and dirty way out on the corners and used 1" metal drip edge nailed over the corner joints.

Re the nailing... I was hand nailing. They say you can power nail but to be sure you don't break the surface.

Anyhow with that experience behind me I still like the cement board product, but think we're going to use it in the plank form on the cabin; horizontal siding. With that you don't nail so close to the edges. Also the panels are heavier.

Oh also, you need a dust mask or respirator or a stiff wind blowing the silica dust away from you. There are special circular blades for the product type. Also prime all cut edges.

[Sassy]

One never knows. 

I plan on telling K she can't use any more power than what this system will provide. 






Maybe I can find a coin fed meter to promote conservation?

   

Hmmm, like Glenn said, there's always just one more appliance or upgrade that we need 

[MountainDon]

640 feet of 2 AWG copper cable for just under $700 is now sitting in my garage. 

At one time I would have thought that outrageous. 

It's THWN-2 so I need to run it through conduit, but I have 200 feet of 1.25 inch that's been laying around for a while so that's not a big deal.

[NM_Shooter]

Hi Don,

Could you tell me where exactly, your garage is located?   

[MountainDon]

It's right here; attached to the house with the Medco locks, the electronic surveillance system, the cameras, Hans and Eva the Rottweilers,  my 12 ga shotguns and 45 cal handguns...

[glenn kangiser]

Looks like you left room for a bit of expansion.

[MountainDon]

The conduit, cable or the arsenal??

[glenn kangiser]

Don, Just thinking a bit here, but with an MPPT controller you could run the voltage a lot higher then drop it to your 12 or 24 v system thereby reducing the wire size.  The one we are using now will take up to around 100 volts then drop it to 12,24 or 48 I think.

"MPPT500 The MPPT500 charges batteries at up to 45 Amps with a universal PV input of up to 100 Volts and can charge 12, 24 or 48 volt battery systems using Maximum Power Point Tracking charge controller. Maximum PV input power is 500 watts. MPPT operation converts power wasted by conventional charge controllers into higher charge current. Boost may reach 30%. Additional features include PWM charge control and a battery temperature sensor and an LCD battery gauge which displays Volts and Amps. Accepts up to #2. 5 year manufacturers limited warranty. "

http://www.partsonsale.com/bzproducts.html

That means you can use smaller wire.

[glenn kangiser]

The cable-- and maybe the arsenal.

[MountainDon]

I'm going to use the Outback MX60A because...
... it's MPPT
... it will allow up to 1600 watts input when the output is set to a 24 VDC battery system, that covers future possible expansion.
... it can handle the expected cold weather high voltage peaks. Remember this is mountainous NM... possible winter lows down to MINUS 20-30 F degrees. (Hopefully not while I'm there... but I do have a big wood pile.)
... it can handle up to 60 amps output (70 with special programming), that covers future possible expansion.

I did come across the BZ MPPT controllers a year ago. The one thing that disqualified them was their maximum voltage. They rate it at up to 100 volts input. The panels I want to use have peak open circuit voltages of 31 to 33 volts (diff mfgs.) They are nominal 24 VDC. Three in series gives 72 VDC. However the peak OC voltage is 33x3= 99 VDC. To that you have to add or multiply in a safety factor for those mornings when it's darn cold. When the sun first hits the panels on such a day the voltage can spike 25% higher for just long enough to damage the controller. 99 x 1.3 (my safety factor) = 129 volts. That's too high for the BZ but within the max rated figure of 150 VDC for the Outback MX60. (The MX60 will shut down at 141 VDC but not smoke until 150+ VDC.)

So the system as planned is at about the upper limit for PV output voltages. More power would have to come from paralleling in more panels; another set of three.

The 2 AWG cable with a 315 foot run, 72 VDC, 8.33 max amps, will only have a voltage drop of 1.4%.  If (when?) I double the panel size the drop would be 2.8% which is still okay, although not ideal. My ideal is 2% max voltage drop.

[MountainDon]

Now we just have to dig the trench to bury the line/conduit. 

[glenn kangiser]

The Outback is one of the best-- I like the price of the BZ but it's not fancy.  Still did good for us at a good price.  I guess that's why he designed our system at 44 volts for the two sets of series panels in parallel.

Drew knows how to dig those trenches.  Maybe a turn plow behind the Jeep?

[MountainDon]

I'm considering a rented Ditch Witch, but I'm concerned about the slope about mid run. I'd hate to have it tumble down hill. I'm thinking of using the Jeep winch as a safety. But then there's the rental cost plus the fuel for an extra trip there and back... 132 miles round trip. Of course that's offset by the time and labor saved by not hand digging. Maybe Drew and crew needs to get away from all that smoke out there?  I was thinking of buying K a nice new trenching shovel with a longer handle than the one I have. She's taller than me. 

[MountainDon]

The Outback is one of the best-- I like the price of the BZ but it's not fancy.  Still did good for us at a good price.  I guess that's why he designed our system at 44 volts for the two sets of series panels in parallel.

Yep. The distance here is what queers a lot of my options. 

Is that a P.C. statement???