Solar Power Shed Project

[scott_vt]

Afternoon Rob,
I trust you had a good vacation !

Just curious about those Watson Trackers . Do they syncronize them but punching in Lat Lon coordinates or do they actually track the movement of the sun. I would think the former, they are really quite interesting just to look at !

BTW, I womt even ask the price You know the old sayin, if you gotta ask you cant afford it

 

[patrick_g]

I hope you either have a calm wind situation or good insurance to cover wind damage. Those panels have quite a lot of area and will generate some massive loads in a good blow. It is good that they revert to a neutral position, horizontal, at night but what about strong winds during the day.

I have been through a series of "I'm really sure this version of the antenna is bullet proof as regards storms and we won't need any kind of deicer." ...and then once again I climb a 100 ft+ tower to help a buddy (science and math teacher) install the new improved guaranteed bullet proof version of a repeater antenna.

I was in Tatum, NM the year it was declared a national disaster area due to an ice storm bringing down the electric lines from the neighboring town, Lovington, with the generating plant, 22 miles away.

The nearest TV transmitting tower was located at CapRock, NM. It was the tallest man made structure in the US (world?) and due to climatic considerations the deicing equipment was deemed wasted expense. During that ice storm it fell down in a twisted heap.

You may never see ice at your location but you will see thunderstorms which will give you wind and lightning. With the investment you have made in this power shed, I wouldn't skip the worst case analysis of storm survivability for wind, hail, and lightning nor would I skip insurance.

Pat

 

[3RRL]

Afternoon Rob,
I trust you had a good vacation !

Just curious about those Watson Trackers . Do they syncronize them but punching in Lat Lon coordinates or do they actually track the movement of the sun. I would think the former, they are really quite interesting just to look at !

BTW, I womt even ask the price You know the old sayin, if you gotta ask you cant afford it

Hi Scotty,
You know I don't know how the tracking system works? I know he has to set them for "solar North" meaning he determines what time of day the sun is at the middle of it's path from rising to setting, then he sets it from there. Someday I will learn more about how it works.

I hope you either have a calm wind situation or good insurance to cover wind damage. Those panels have quite a lot of area and will generate some massive loads in a good blow. It is good that they revert to a neutral position, horizontal, at night but what about strong winds during the day.

Pat, LOL ...I hope the same thing.
We checked into the wind condition and it is very low at our place. That was another reason wind power was not included. That doesn't mean we don't get gusts, however. I've seen evidence of gusting when we get back to camp (infrequently though) and things have been blown around. There's only so much you can do and guard against before being overwhelmed by the possibilities and then trashing the project altogether in fear of a disaster. Laying them horizontal is not a bad idea. Once I move up there and a wind comes up, there's nothing preventing me from having them flatten out until the storm subsides. Maybe some sort of safety tie off lines? I'll have to check how our insurance treats wind damage as related to non building structures. If a rider is necessary, so be it.

Eddie,
Star Wars? How about Star Trek? I told you William Schatner has a place a couple miles down the road.

 

[patrick_g]

Rob, Drive a stake (a few feet tall) in the ground. Put little pegs in the ground (or lay out marker rocks) at the tip of the stake's shadow at various times of the day. The pegs (or rocks) will describe a a nice smooth continuous curve. Look at the curve and eyeball where the curve comes the closest to the tall stake. Draw a line from the tall stake to the closest approach of the curve. This is local true north. With the change of the seasons the observed altitude of the sun will vary as will the curvature of the shadow's path but the shortest distance will always point true north and the time of the shadow's closest approach to the stake is local noon.

Local noon can vary considerbly from noon by a clock set to local civil time because your longitude may vary from the center of the time zone. Except for daylight savings time, the error between your observed local noon and noon on your atomic clock is a constant and does not vary with the seasons.

Being so or becoming so attuned to the sun you might enjoy a nice decorative tall permanent stake with marker stones or stakes to indicate the hours of the day for various seasons. Important solar days are the summer and winter solstices (longest and shortest days of the year.) You might want to mark the autumnal and vernal equinoxes as well.

Once marked and identified the marker stones or stakes are a reliable clock and calander. We aren't practicing pagans, Druids, or such but when we were at our leashold in Mexico doing our solar thing we constructed one of these. Maybe we are easily entertained but we certainly enjoyed it and it make a nice conversation piece as well as a neat decoration.

Maybe the trackers can be programmed with a panic switch or panic mode that when invoked commands them to all go horizontal. Then with a simple wind velocity limit switch you could easily have them automatically go into self protection positioning. I'd suggest two limits. One that if exceeded causes them to go horizontal and another lower limit that the wind has to go below before they go back to normal pointing.

There are wind alarm capable weather stations but if it were me I would probably make my own damped limit switches. If the trackers require a logic level voltage or NC or NO contacts it would be easy to provide whatever.

If you are interested but don't spark much interest with your solar guy, just find out if the trackers can be commanded to horizontal by as hoc commands and if they can be returned to normal service by an ad hoc command. If the answers are yes and yes and you have a way to issue these commands to the trackers but no interest on the solar guys part, I'd be happy to make some simple suggestioins as to how to accomplish the deed.

Pat

 

[3RRL]

Pat,
Thank you for all the great suggestions again, and the offer to help me. Sure do appreciate that. The solar guy is so inclined and has (will) make provisions for the horizontal storm position via a control from inside. He was already thinking about it when we went up there.

I really like the idea of finding local true North for each season. He did that also with a stake and marked the positions to find "noon". But I like your idea of having several sets of stakes and rocks (whatever) as permanent markers for each season. Much like local sun dials I presume. Very cool indeed.

 

[patrick_g]

Rob, Not to be a nitnoid but true north is true north is true north and once you have it you have it close enough for any of your purposes for many centuries.

It really doesn't vary by season and only varies enough to be noticed by normal means in a short span of centuries. Ever spin a top? The gyroscopic action keeps the axis pointing in the same direction, essentially, but there are some other motions. The top of the top seems to describe a small circle with maybe some minor variations embroidered onto the motion. The circle is caused by precession (torque induced precession) and nutation is the minor nodding as the circle is moved through. There is also polar motion that is induced by tides, ocean currents, and such when the top is the Earth.

You won't be bothered by any of these. For my and your personal use none of these imperfections in the gyroscopic motion of the earth will be noted by a stake and shadow.

A separate stake (AKA gnomen, shadow pointer) for each season, as you suggest, might be neat. Of course you can do it all with one gnomen as well. Each season or subdivision of same has an associated curve that is one of an infinite family of curves. If you mark each season or subdivision of the seasons with say, a different color rock or stake then you can easily discern the situation for any season.

By placing your markers at precise times (it is OK to use your local time, even to use daylight savings time) the shadow will repeat its path on subsequent years making this a clock. These can be used as a calandar as well as a clock.

Another idea I had but haven't done yet that I would like to share is elevating the markers. You could place marking wands (stakes) in the ground such that the tip of the shadow just grazes the top of the wand. A colored stone or crystal or prism located there would change its lighting when touched by the shadow and I think that would make a neat effect. Another advantage of placing the wands such that the top of them are just touched by the shadow is that you can do this in a flower garden or other area where plants might cover the rocks or short stakes at ground level.

It is a fairly easy task to lay one of these out and once done well it will work just fine for a long long time.

Another solar "gadget" that has fascinated me is the noon cannon. On plantations and other large holdings before it was common for just about everyone to have a timepiece they used to fire a cannon at noon to mark the middle of the day. Eventually somone put a magnifying lense near the touch hole of the cannon so that at noon the concentrated light of the sun's image would hit the powder in the touch hole. The cannon would fire at noon, automatically. I have seen some ornate examples of these in museums and other collections. There were examples on display at the San Diego Yacht Club along side the America's Cup when it was there.

Regarding your storm response on your trackers... you want to automate the system so that in case of a storm when you are not home the system will self protect. The two obvious choices for doing it are: 1. get a signal from a hoime weather station that has wind alert feature or 2. add wind velocity switches and the simple logic required to command the system to self protect and command it to resume standard operation.

You will want different limits for these decision points. Lets say (and I am just guessing at wind values, I don't know the guarateed wind survival figures on your equipment) you want to protect if wind exceeds 30kts and to resume if the wind falls below 20kts. You will need the effect of retriggerable one shot multivibrators as timers. This will allow the wind sensing system to note when the wind exceeds a threshold value and then pause for a specified time interval. If during this interval the wind speed stays above threshold the system issues a command to self protect.

Then so long as the wind stays above the lower threshold value (20kts in our example) the system stays in self protect mode. The "hysteresis" (difference between the upper and lower threshold values) prevents the system from constantly trying to protect and unprotect if the wind happens to be near the upper threshold value. The timer effect at the lower threshold requires the wind to go below the lower threshold value for a specified time interval before the system resumes normal operation.

You do want to choose wisely, Grasshopper, the upper and lower threshold values as well as the delay times (which are not neccessarily the same for upper and lower threshold.)

Hopefully this doesn't sound too complicated because it isn't really. You can build a reliable system to do this with parts from Radio Shack or on-line component sources. The output of the system is one of two possible states. One state represents a command to self protect and the other is a command to resume normal operation. Because of the built in delays of the timer circuits the system can't "go crazy" and try to quickly alternate between protect and normal. Yoiur solar guy will have to specify what the tracker controller needs to see as a command. It could be a voltage or a switch closure or ...

Pat

 

[EddieWalker]

Hey Pat,

I'm really enjoying reading your suggestions and thougths on the sundial. One of these days, I think I'd like to buidl something like that in an open area and set it in concrete. Do something nice with some iron and make a display out of it. Maybe in a flower garden, but make it big enough that you have to walk through it to see it!!!

If you, or anybody else, ever decides to build one, please start a thread on it and post some pictures. I'm sure there are plenty of us here who would really enjoy it.

Lots of great ideas here. Thanks.
Eddie

 

[patrick_g]

Eddie, I'm glad you are interested in and enjoy the sun stuff. What you suggest WRT the walk through garden is what I think I would like too. I'm still cogitating on the crystals/prisims/whatever. The things I described all have the shadow pointing out the time/seasons. I have some ideas on how to have the sunlight be the pointer so the various markers (prisms/crystals/piece of colored glass are illuminated at specific times instead of shadowed. That would, I think, be a tad complicated to explain by this medium.

Consider the example of the noon cannon. If the magnifying glass were fairly large with a long focal length or a curved mirror could be substituted for the magnifying glass. The image of the sun (bright spot formed when burning ants and such) could be projected in turn onto the various crystals/prisms/colored glass (maybe not in too sharp of a focus so as to not overheat the target.) If you could arrange for the bright image of the sun to be directed to the same spot where the end of the moving shadow was then you'd get way more contrast and the effect should be quite sutnning.

Unfortunately, even though I had upper division optics and am an amature astronomer, I am not an optical physicist (like my FIL was) so the ray tracing and design of the system is much harder for me. If I could get a young optical designer interested that would make it way easier as a bright optics guy could save me from pursuing dead ends and make the task go faster.

Oh well, I can always do the shadow pointer thing.

A side note: Lots of garden catalogs sell "sun dials" but sun dials are made for a specific latitude and are only "right"
at that latitude. I have read books on sun dials and there is just a lot more to a sun dial than meets the eye of the casual observer.

Pat

 

[Doc_Bob]

Bob,
That same picture in your quote has me standing 5' uphill to the very left in a tan shirt. I'm 6ft 190lbs. Check it out.

You are right, I missed you in the pic, result of too small a pic, me reading to fast and the similar colors made you blend into the background. Next time,where something like bright blaze orange
Bob

 

[Defective]

Bob,

I'm jealous. I wish I could afford to do an off-grid setup like yours. I'm truly enjoying this thread.

Now, back to the hijack...

Patrick,

Why not just put your "crystals/prisms/colored glass" inside tubes and orient them carefully? This would give you at least part of the effect you're looking for.