OFF GRID POWER; various thoughts on...

[MountainDon]

Yeah Dave, poles are actually king in my book.      I was thinking of expanding on the original thoughts, but I was rushed and concerned my response with the original roof question. I do like poles a lot more than roofs though, for PV panels, no doubt on that.

No scrambling on the roof required.
No penetration problems (with the roof)
Excellent circulation of air around panels.
Easy to adjust the angle, see my quickee adjuster with the month positions marked.
        http://countryplans.com/smf/index.php?topic=2335.msg97225#msg97225 scroll down one image
         I am happy with the way that turned out. 1x1, 11 gauge (1/8" for those who don't do metal gauges) steel tubing
Easy to adjust left-right to pick the best sun orientation line.
On roof panels seldom have perfect sun orientation lines.
Easier to clean when necessary. I have a long handled (extended with PVC pipe) broom and a long handled mop.

Buy old drill pipe. I got 4" ID 1/4 inch wall quite cheaply, compared to new. THe Uni-Rac mount is sturdy and well made, easy to mount the panels to. I added my brace arm for two reasons, ease of adjustment to as a wind brace.

Personally, I would not want to have to access panels, or anything else, on a 12:12 roof if I didn't absolutely need to. As a last factor, a special GFCI may be code required for panels on a metal roof. Not sure if that in for Grid Tied only or if for Off Grid as well? I'd have to check in that.

Ground level racks are also usable in some place.  



Dave knows a little bit about solar.       http://www.sierratel.com/offgridsolar/

[davidj]

In retrospect, pole mount sounds good.  Or, more to the point, working on a 12:12 roof sounds anything but good!  Unfortunately I've got a lot of 100ft high trees on my lot and only two open areas - one where I put the house (positioned so the S facing roof gets the most Sun!) and one 200ft from the house right on the road (if you can call our dirt track a road).  I guess I could put something by the road, but it would definitely distract from the otherwise wilderness feel of the approach (and would be more likely to be stolen).  Cutting down trees is also an option, but it would be hard to clear out enough space without changing the feel of the lot.

A pole-mounted system would also need to be pretty solid (or very easy to tilt) as we get a lot of snow (100 psf snow load).

Re the thermal issues - I'd think there should be pretty good circulation thanks to convection on a 12:12 roof.  There has to be at least an inch of space due to the seams, and there should be plenty of temperature differentials to get air moving.  And the roof itself has an inch of ventilation underneath it too.

I was planning on using a GFCI on the panels as my supplier (Sierra Solar - very helpful company) said that I'd need one.

[MountainDon]

 Unfortunately I've got a lot of 100ft high trees on my lot and only two open areas - one where I put the house (positioned so the S facing roof gets the most Sun!) and one 200ft from the house right on the road

Trees up to 75 feet with us. Same sort of situation. That's why our cabin is where it is and the panels where they are; 300 feet away. Works well, but it needed all that copper wire (#2AWG) and conduit.

The Uni-Rack site gives wind loads on their model of racks, not sure about snow. The panels would have to be raised enough to allow for clearance height with all the snow that slides off. Our experience has been that the snow has little problem sliding once the sun comes out. If we;re there at the snow time I usually snowshoe down to them and brush them off. I keep the broom and washers tied vertically to a nearby tree rather on the ground so I can find them in winter.

[intelijoc]

I'm spitballin the idea of setting a solar array on my vacant property ( currently structureless).
Will I first have to connect to the "grid" utility company?
If I did this, would I be able to sell electricity back to the utility company for cash?  Or would they simply issue credits to an existing account.. am I making sense?

[MountainDon]

If your possible building plans include being grid tied you should check with the local power company before doing anything. The power company we use at home has a great plan for grid tied residential customers. With them it's possible to select from a plan that just gives credits to your account when you produce more than you use. They have another plan where they will pay credits by monthly check. The company we could connect up in the mountains by the cabin has no such buy back offerings at all at this point. So it not only varies state to state, but it varies company by company.

Being grid tied can save you the cost of the batteries needed to be fully off grid. That has the drawback of leaving you in the dark when their side fails.

Note that even if your location is remote enough to be lenient on building codes, or maybe no codes at all, if you connect to a power grid, they will almost certainly have rules that need to be met, including minimum equipment standards. They may also require a professional electrician for part or all of the PV installation and actual grid connecting.

[intelijoc]

I did not know about the minimum standards, rather; never considered it. Sounds like a permit may be in the future.  I'm a pole away from power.  Can I get power dropped to my parcel, (without ant site plan or building plans?)say to use for temporary 3-4 weeks stays in a travel trailer. I could always boondock

[MountainDon]

Once again that is sometimes a local thing. To get a permanent hookup here in the suburban area one needs a building permit first. But up in some more rural areas here you can get a power pole and meter by simply asking and paying for it. There will likely be a monthly fee, just for being connected, even if you do not use power. Ask on that. If they have a good buy back PV program the energy made when you are not there could pay for that and leave money left over. But as I pointed out the way the companies do that is all over the place, good to bad and worse.

G/L   It would be nice to have checks coming in the mail when you aren't there. 

[intelijoc]

Checks coming in the mail when I'm not there would be ideal.  I'm doing a recon trip out there in July. 

[MountainDon]

If you know the name of the power company you might be able to find all the info online. My city company has everything available online, all the rules and docs that are needed. Then again the mountain coop has nothing.

[intelijoc]

That was my heading: online search, phone calls and documentation.  The July trip is for information gathering from a real world perspective.  I like to be hands on and meet/greet as many people on the mountain as possible.  The owners behind my parcel have spent considerable time clearing deadfall,etc.  I want to meet them. I also discovered 2 lots with driveway, septic and electric for sale on my road.  FWIW- one piece or land for sale has the drive, septic and electric with a log home kit bundled and sitting there. It's been like that for at least 2 years- the bundles of precut ready to go logs laying on the property at 10,000ft-snow, and all the elements.  I actually remember seeing this debacle in the summer of '07 so that's pushing 3 years.  What a shame.

[MikeOnBike]

Hope this is the right thread for this.

We plan to start a 20'x32' cabin this summer.  The first task is to build a 10x12 shed to camp in and store materials and tools.  We will eventually have solar power and the solar panels will either be on the shed roof or next to it.  The shed is directly behind and to the north of the cabin.  Both the shed and the cabin will have have their roof ridge oriented east/west.

We are at ~43.5deg lat.  Our sun altitude alternates between 23deg and 70deg.  I need to make sure that the solar panels on the shed roof will not be in the shadow of the cabin.   I need the angle A between the ridge of the cabin and the eve of the shed to be less than 23deg.  Any more than that and the solar panels will be in the shadow of the cabin in the winter.





First a few numbers to work with:
Cabin to Shed Distance  33ft.
Cabin Depth to Roof Ridge 10ft.
Cabin Base Elevation  0ft.
Shed Base Elevation   3ft.
Cabin Max Height    24ft.
Shed Height to Eve  10ft.

We can use a little trigonometry to find the angle A between the cabin roof line and the shed eve.  The tangent of an angle is defined as the opposite side divided by the adjacent side.

Op
---- = tan(A)    The inverse tangent or arctangent will give us the angle A which is the slope from the cabin ridge to the shed eve.
Adj

The cabin height is the base cabin elevation + the max cabin height or 0 + 24 = 24
The height of the shed eve is the base shed elevation + the shed height to the eve or 3 + 10 = 13
The Opposite side is the difference between these two or 24 - 13 = 11

The distance between the ridge line of the cabin and the shed is the distance between the shed and the cabin + the cabin depth to the roof ridge or 33 + 10 = 43.  This is the Adjacent side of the triangle.  Now reach for a calculator with trig functions or find a web calculator.

11
--- = tan(A) = 0.255814   The arctangent or inverse tangent of 0.255814 is  atan(0.2555814) = 14.34 deg.
43

14.34 deg is less than the minimum winter sun angle of 23 deg at my location so I don't have to worry about a shadow on my solar panels in the winter.

Hope this might help someone with a similar situation.  It should be useful if you have a cabin or trees due south of your solar panels.

[Dave Sparks]

Mike,
That was a nice post and I am sure helpful. One of the other ways is basically using posts and being at the site during the winter solstice. Kind of the no math version. I think it is best to always live thru a year at the site! It is amazing how many different things will occur to one. Hey Don!  What time is happyhour?

Oh yea, the reason I posted was to tell you guy's that some of these long runs of cable we have to do, will be getting easier. Magnum energy has a 250V charge controller out this summer and there is another that I can't talk about that will enable some very, very long runs with small wire.

[MountainDon]

That's cool. Good of you to share this trig lesson. It goes to show there are good reasons to pay attention in class.  

[intelijoc]

I've done due diligence part 1.  Contacted county planning, power company and mapping.  Seems like the bottom line is to get power on my property I need a rought site plan, driveway, septic and well and an engineer to coordinate all.  Sine the lots is less that 2 acre it need to be wetlands free.  What I did not ask was if I could get power dropped to the lot for use with a travel trailer- yikes!  I want to be able to use my place sooner than later.  It may be 5-7 years before I have the financial bump ++ to get a permanent structure built.  I was considering extended stays.  The solar was a way to maybe get cash when I am not present. 

[davidj]

14.34 deg is less than the minimum winter sun angle of 23 deg at my location so I don't have to worry about a shadow on my solar panels in the winter.

I was just thinking about similar things myself.  One thing to watch out for with this calculation - you need to have an angle that's quite a bit less than 23 degrees (as you have), otherwise you'll get Sun in the middle of the day but only for a minute or two!

We're at a latitude of about 39.5 degrees north, so I think the Sun gets up to more like 27-28 degrees mid winter.  Looking at some graphs I found on google, if you have a 20 degree vertical angle to an obstruction, with at least 30 degrees each way horizontally to the SE and SW, then you get Sun from 2 hours before midday to 2 hours after.  It looks like this'll probably cover almost all of the solar energy you're gonna get at that time of year.  Time to get out the inclinometer I bought from John, stand on top of a step ladder and see if Don's suggestion of pole mount panels is gonna work...

[MikeOnBike]

David, you have a good point.  My model is a fairly simple representation.  It does not consider the varying angle of the sun from sunrise to sunset.  It is only 2 dimensional, a snapshot in time. 

If we use the middle 5 hours of the day, the sun at our site alternates between 15 deg. and 23 deg.  I can probably get by with making sure the angle between the cabin ridge and the shed eve is at least 15 deg.

Since the angle in my example is 14.34 I will just barely be clipping the panels with a shadow during that 5 hour window.  At my site the 4 hour window that you suggest is 18 deg. so that period would be shadow free.

[OlJarhead]

Having considered my dilema of the well being located too far from where I plan to install my battery bank (about 150 feet) I've thought seriously about buying a Costo 60 watt system which includes 4 15w panels, a 7am charge controller and 200 watt inverter.  It's $269 and a deep cycle Marine battery with 85 amp hours of reserve runs about $62.

My thought is that I can install this system on the small pump house I plan to build and put a switch in it so I can turn on the pump easily (today I have to clamp the battery to the pump using the alligator clamps coming out of the well head).

What do you all think? 

I plan a 600 watt solar system for the cabin with 1000 watt inverter but thought perhaps this would be a good second system for the pump and perhaps someday a small shed can be put there also with some lights running off the inverter (or 12v).  Also I was thinking I could use the inverter to charge my Ryobi drill batteries.

Thoughts?

[OlJarhead]

OK I took the plunge and bought the Costco system and a Deep Cycle 12v battery (85 AH) for the well.  Once home I tested it all out and found each panel kicked out ~20-22 vdc and the Charge controller ran about 20vdc (it tells you 5-10% of panel output).  The panels are in parallel and produce a combined 60 watts in optimal conditions according to the booklet that comes with it.

I hooked up the battery which was running ~12.5v and in about an hour the controller kicked off.  Which, according to the booklet happens at 14.2v.

When we get to the property I'll build a small pump house to house the battery and controller as well as the inverter and set up a station to charge a second 12v battery (I like a back up battery and keep my old jeep battery for the well) and a station fore the Ryobi charger (need to check wattage).

I'll let you know how this works out for us but I'm hopeful we can run the well pump at least a couple hours a day and not have to use the generator any longer to charge a battery to pump.

We used to run a trickle charger (2amp) during the day while working on the cabin and then hook it up for a few hours (the battery) on the well -- then repeat in a couple days.

This last time we got busy and forgot to charge the battery for the well and the cistern ran pretty low (pressure at the spicket was way down)...so I need to get 1000 gallons (or close to it) back into the cistern and keep it up there for the summer months of cabin work.

It's VERY nice having ice cold water in the summer!

This investment was ~$330 and I'm hopeful in the end that it will save generator usage and gas as well as the need to plumb electric from the cabin solar (12vdc) to the well.

[MikeOnBike]

OlJarhead,

I'm really interested in how this works for you.  I have a similar situation.  Our main cabin's solar/battery is about 250ft from the spring.  I was thinking about the same kind of setup you are using.

We will have three cabins on our property.  Mine is the furthest and highest elevation gain from the spring.  I'm about 1200ft. away and 150ft. above the spring.

I'm considering this pump to give me a couple of gallons/min to fill the water tanks in each cabin.

Solar Pump
http://www.firemountainsolar.com/waterpumps.html#solarslowpump

Elevation/GPM Chart
http://www.firemountainsolar.com/pdf/solarslowpump.pdf

[davidj]

In retrospect, pole mount sounds good.  Or, more to the point, working on a 12:12 roof sounds anything but good!  Unfortunately I've got a lot of 100ft high trees on my lot and only two open areas - one where I put the house (positioned so the S facing roof gets the most Sun!) and one 200ft from the house right on the road (if you can call our dirt track a road).  I guess I could put something by the road, but it would definitely distract from the otherwise wilderness feel of the approach (and would be more likely to be stolen).  Cutting down trees is also an option, but it would be hard to clear out enough space without changing the feel of the lot.

After wandering around the lot for a while I've found a point by the driveway that's a fair distance from the "road" and that has a decent view of the Southern sky.  The trees to the South are about 25 degrees above the horizon, so it's not gonna get much sun December and January, but I guess that's what backup generators are for.  What's more I can put the generator/inverter shed and propane tank near by, and run LPG and 240V side by side for the 200' to the cabin.

This is good news, as I thought my cabin was facing almost South, but it turns out it's facing roughly magnetic South, not true South.  What's more it's the wrong side of magnetic South too, so it's almost 25 degrees off.  I guess it's a good idea to check the magnetic declination before you have the whole cabin built....

So goodbye scary chicken ladders and fussy roof clips, hello solid and dependable schedule 80 steel tube.

Now all I need to do is find out how much pole and concrete I need to hold up 50 sq ft of panel centered 10ft off the ground in a fashion that the building inspectors don't object to and the snow won't destroy...

[MountainDon]

Now all I need to do is find out how much pole and concrete I need to hold up 50 sq ft of panel centered 10ft off the ground in a fashion that the building inspectors don't object to and the snow won't destroy...

UniRac, manufacturer of pole mounts and so forth, has info on pole sizes, depths, etc for various combinations of panels and expected wind loads. Sorry, I have no link at hand but have a printed brochure someplace.  Google UniRac Albuquerque

[Bob S.]

I have been watching this topic for guite a while. And it has accured to me that you could build a coverd patio/out door kitchen ect. with a shade made from solar panels. Not protected from rain but protected from the sun, should work well.

[MountainDon]

Sure. The Intel Fab here has an array that is the shade roof for parked cars, I believe.

(They have it I'm not sure on the parked cars....   Car shades are common in the SW)

[OlJarhead]

OlJarhead,

I'm really interested in how this works for you.  I have a similar situation.  Our main cabin's solar/battery is about 250ft from the spring.  I was thinking about the same kind of setup you are using.

We will have three cabins on our property.  Mine is the furthest and highest elevation gain from the spring.  I'm about 1200ft. away and 150ft. above the spring.

I'm considering this pump to give me a couple of gallons/min to fill the water tanks in each cabin.

Solar Pump
http://www.firemountainsolar.com/waterpumps.html#solarslowpump

Elevation/GPM Chart
http://www.firemountainsolar.com/pdf/solarslowpump.pdf

Just got in but the first trial has been a good one, albeit a learning one!

First off, it rained almost the entire time!  I'm not sure how much that hurts solar panels but I DO know that it's a calculation that you must take into account when designing a system.  Cloud cover means poor performance.

So, having experienced rapid charging in full sunlight (rapid is a subjective term of course) I was surprised at how slowly the panels charged the battery in cloudy rainy weather.  But not really   I was actually surprised how well they did despite the clouds though I did move them to track the sun to maximize the solar power generation.

I hooked up the 85ah deep cycle battery to the well when we arrived and began pumping water right away.  Once we had 26 gallons in the tent trailer I let the pump run until the battery dropped (without panels) to 12.3v.  I then shut it down.

The next day I assembled the panels and let the battery charge to 12.9v by making 3 adjustments to the panels -- 7:30am they faced East (to catch the morning sun) and by about 1PM I faced them South and finally around 5PM I faced them West -- however, it was raining and pretty dark with clouds most days.

I pumped the well enough to drive the battery down to 12.3v again on Wednesday and it really down-poured!  The weather was foul but the battery seemed to almost hold under the strain as long as the panels faced the sun.

Thursday after letting the battery hit 12.9v again I let the well pump and drive it down to 12.4v again then disconnected  it.  I did notice however, that in light clouds and almost sunlight the battery hovered around 12.4v as long as on the charge and didn't seem to drop lower.

On Friday the sun poked out a little more and the battery climbed about 13v for the first time   It was working!  I pumped more water and continued to track the sun with the panels.

I've now decided that a lazy susan would be a good way to track the sun -- just assemble on big enough to sit on top of a well house and then rotate it during the day to catch the sun...after all, why spend $1000 on a tracking pole for a $269 set of panels?

All in all I'm impressed with how well they worked and am certain that if the sun were out all day I'd have a full cistern.  As it is it rained so much that when the sun finally did come out it was nearly a shock!  Most days were in the 50's (is this really June?) and very cloudy and wet.

Last night it dropped to about 39 degrees and was clear....and we came home today.

[davidj]

I have been watching this topic for guite a while. And it has accured to me that you could build a coverd patio/out door kitchen ect. with a shade made from solar panels. Not protected from rain but protected from the sun, should work well.

This was actually our second-from-last plan - a "solar gazebo".  I was gonna build a timber-frame 10'x12'x10' structure, put a steel tube across the middle of it and mount a tiltable panel.  In Summer we'd drop the panel flat and put the picnic table under it.  In winter we'd rotate it near vertical and it would catch the low Sun and shed snow (and not be in the way at that time of year - "hanging out in the yard" isn't really gonna happen when there's 4' of snow on the ground!).  It all fell apart when I realized that "cabin South" and "true South" were actually 25 degrees off from each other and hence it wouldn't get as much Sun as I'd hoped.

The Sierra Nevada brewery in Chico also has a parking lot shade structure made of solar panels.  But I prefer their "recycling" - the brewing mash gets sent to a local cattle farm in exchange for (very tasty) steaks which they server at the restaurant!