Solar Tracking

[kalakoa]

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I spent $1800 to triple my admittedly puny original 720 watt array to 2160 watts.

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At $1/W, more solar panels would be cheaper, without the need to maintain complicated mechanical tracking hardware.

[Wao nahele kane]

quote:

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Originally posted by kalakoa

quote:

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I spent $1800 to triple my admittedly puny original 720 watt array to 2160 watts.

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At $1/W, more solar panels would be cheaper, without the need to maintain complicated mechanical tracking hardware.

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Okay, I'm not getting pissy here, I'm just going to lay it out regarding what's best and what's not best.

Bottom line; It's all subjective to the situation and there are many potential variables regarding the matter, thus there is no "golden fact" applicable to every situation and the price of panels is only one aspect of the several possible aspects regarding the matter. If all solar panels fell to one cent a watt tomorrow, there will still be situations where having more than X array area is neither possible, desired or necessary and tracking is the best option. Giving up land for two very large arrays is not always practical to some nor is the expense and hassle in altering the layout of a current infrastructure to accommodate another monster array to gain the appropriate solar line of sight. Thus the expense be it the money in diverting a driveway, cutting down desired trees or what have you may still exceed the cost of a solar tracker even if the panels were free. Other considerations are light reflection from fixed panels that in some cases can damage nearby food crops etc. Solar trackers reflect light back at the sun and not someone's crops, car, house, etc. There's also the expense of an additional charge controller if necessary and its installation if not a DIY. There's far more to the matter than dollars. What works for one person may not work for another person.

So with that in mind... the best option will always be determined by individual need.

- Armed citizens provide security of a free State.

[kalakoa]

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So with that in mind... the best option will always be determined by individual need.

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Agree 100%.

That said, I try to capture things in the design phase: by orienting the house such that the roof is ideal for solar, I was able to lay the panels flat (with simple mounting hardware), thereby avoiding the need to maintain complicated mechanical devices in a hostile tropical environment.

I still do some tracking, but with MPPT controllers (again -- no moving parts).

There seem to be lots of misconceptions about PV, such as "needs huge land area" -- this may be true for the 10-15KW that a mainland house "needs", not so much here.

[ericlp]

Dual Axis Kits are nothing new. They are however more expensive than a single axis unit. That being said. Would be nice to see the pictures of your project. If I had that kinda cash to spend... I'd probably get something like this and be done with it.

http://www.youtube.com/watch?v=A3COMC0eT3Q

[Wao nahele kane]

My house has a flat top viewing roof deck (5th floor)so no room for panels on that. As per solar line of sight, it's amazing that with so much open area there is very limited space in and around the power station position for solar arrays. Tree shadows only a smidgen partially on an array can severely diminish electrical output and when you've big arrays (20 or more panels)it takes substantial wide open space to avoid partial shadowing throughout the day.

Truth be told... I'd like a 10-15KW system so I could do some of my 250 amp welding off solar instead of using my Miller Bobcat. My 5Kw PV system doesn't have the necessary punch. As per the tracker I'm building, there will be no maintenance short of washing the panels and re-painting the frame every 10-20 years or so. The motors are sealed brushless and subject to near no-load use circumstances, the slewing drives are industrial based behemoth mechanisms with zerk fittings and sealed grease gear enclosures. Those off the shelf systems (that will not work fully automated here 20% of the year) with linear actuators (gate openers) would require expensive replacement mechanism type maintenance, not so with my system. It's being built to work on this Island.

- Armed citizens provide security of a free State.

[MarkP]

Kalakoa:

What angle from horizontal are your panels? I assume most are pointed true south.

I have a 40' shipping container with a 12' wide roof that overhangs the ends so have roughly 45' x 12' to put panels on. The 9 240 watt panels I now have basically max out the single Morningstar 45 amp mppt controller I have and they fit neatly on the roof. If I were to go twice as large I would have to decide what land area to sacrifice. If I had a square pyramidal roof instead of a long skinny roof I would have to break my panel bank up into perhaps 3 banks of 3 and then I would have to buy 2 more controllers so each bank that gets sun at different times and different amounts would have its own controller, so tracking with excess panels and charge controllers does come with a cost.

At present I am not hurting for power but then I haven't hooked up the big screen TV yet. I spoke with friends who live closer to Hilo and they said they have something like 2,500 watts now but would double or triple that if they could. Hilo has got to be sunnier than Eden Roc so I don't know what they are using it all for but then again they have 10 times the money I do and a real house so they are finding a way to burn that power. Then again I haven't looked at the state of charge of my batteries yet today so I may have to start the generator. I basically have only one day's storage.

[Wao nahele kane]

MarkP,
Since you're already maxed on the Morningstar and if you have the LOS space. Doubling may work best with a split angle east/west by south. IE One array pointing South East and the other South West since you'll need to purchase another CC. This way you have 2 peak power output periods with an elongated upper charging envelope period in between. That would produce more power than having them all pointing in one direction.

- Armed citizens provide security of a free State.

[Wao nahele kane]

Another less expensive (than tracking) addition with the split pointing is to prop those panels on an adjustable elevation stand, where you can adjust the elevation 8 times a year in quartered increments from above horizon around 40 up(winter) dropping the prop support down to 90 elevation above horizon (summer) and then back up again to the lower winter elevation.

- Armed citizens provide security of a free State.

[kalakoa]

Seasonal tilt adjustment makes more sense in northern latitudes, and is probably "more" effective with monocrystalline panels.

Simple test rig in the driveway tells me it doesn't make a difference with thinfilm panels at 20 degrees N; I get the same power output from nearly-flat to nearly-vertical.

You can make a PV array as large as your controller will handle, but it works best when all panels have identical Vmp/Imp. (Engineers will say "use blocking diodes where the sun or shading may vary" -- most modern panels already have these.)

[Wao nahele kane]

Kalakoa,
I've not yet tried an angle tilt experiment with my polycrystalline panels yet but there should be a large effect. Did you compare amperage as well as voltage output or just voltage? Typically a reasonable angle doesn't result in much voltage fluctuation output but the amperage output is vastly effected. The annual deviation in noon declination is greatest at the equator at 46+ plus degrees, that annual angle deviation decreases closer to the poles.
Blocking diodes are only useful in parallel where one panel is shaded in the parallel group. In series... it's a whole different issue where an entire series panel group is effectively crippled. If someone has 4 series strings and one panel in a string is blocked up to a 1/4 power loss may occur. The panel cells within aren't typically diode protected amongst one another.

- Armed citizens provide security of a free State.