Author Topic: Add a solar tracker or buy more panels?  (Read 4019 times)

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fabieville

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Add a solar tracker or buy more panels?
« on: August 30, 2016, 11:48:39 PM »
I am trying to find out if its better to add a solar tracker to a system or just buy more panels with the same money that it would take to build a tracker.

I currently have a 500 watt array consisting of (2) 250watt solar panels with a mppt charge controller to regulate them. They are currently flat mounted on my roof. There aren't any trees or building overhead so I get good amount of sun but I am still loosing out on some energy due to the fact that they are fix mounted and not on a tracker.

I am trying to figure out if it makes sense to build a tracker to get close to the 500watt most times or just buy 2 more of the same panels with the same money that it would cost me to build the tracker?

In other words would buying 2 more 250watt panels bringing my array to 1000watt total and have them fix mounted outperform or have similar daily production as my current 500watt array which would be on a tracker?

In simple terms would a 1000watt fixed mounted array out perform a 500watt array on a tracker?
I get about 7-8hrs of sunshine each day in Jamaica

I really love trackers but they cost too much and more complicated and have higher risk factors and maintenance.
« Last Edit: August 31, 2016, 09:14:18 AM by fabieville »

DamonHD

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Re: Add a solar tracker or buy more panels?
« Reply #1 on: August 31, 2016, 03:46:08 AM »
Look at a system such as PVGIS (for Europe in this case):

http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php#

and let it compute output for you with an without trackers (ie can do 1- and 2- axis).  The panel will not be running at full output the whole time even with a tracker.  In particular in cloudy weather the light is not very directional.

Unless you are very short of space more panels is probably cheaper and simpler, but get some actual numbers!

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fabieville

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Re: Add a solar tracker or buy more panels?
« Reply #2 on: August 31, 2016, 09:13:15 AM »
I use the PVGIS system and did the calculation and it shows that the fixed mounted 1000watt array would outperform the 500watt array on a tracker. I did more than one calculations with all kind of adjustments and always adding a difference of 500watt extra for the fixed mounted array because the cost to build the tracker would allow me to buy 500watt worth of solar panels and all the different calculations and adjustments shows me that the array with the 500watt more would always perform better. I am in Jamaica and the map could not zone in on my area so I choose a area on the map in Africa which I assumed has similar amount of sunshine like in Jamaica.

Anymore thoughts on this topic? I would greatly appreciate your ideas.

george65

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Re: Add a solar tracker or buy more panels?
« Reply #3 on: August 31, 2016, 10:00:49 AM »
I have been looking into solar myself and am about to set up a system.
From what I read, the best solution is to aim the panels True north at the latitude of your location and be happy.
If your panels are not aimed optimally in a fixed position, you'll make more up by fixing that than adding a tracker.  From what I read, a lot with solar panels is " close enough" and they can be a fair bit off in some orientations without a huger loss of performance.  You just want to make sure the don't get even partially shaded though.


 That said, I'm intending to build my own frame work and have it 2, maybe 4 position adjustable for each season, Summer and winter at least.  I am also thinking to offset it a little to the direction of the afternoon sun for a few reasons but I can easily monitor and test it and see how that goes.
I have to look into this a bit more but I may be able to use something like an electric gate closer arm to ajust for seasonal tilt.

500W is really a piddling amount of panels these days and the gains I believe you would make with a tracker -Might- be 10%. I don't think it would even be that much but play devils advocate and call it 20% which Is probably never going to be an increase you'd get to.   Thats a 100W gain on your present system. No way in hell it what worth setting up a tracker for.

Where I am, there are a lot of Cheap, used panels available. Many are only 2-3 years old and have been replaced by people wanting to upgrade their systems that have limited roof area, coming from homes being torn down to rebuild, insurance through electrical problems etc.
I'm going to pick up 5x 225W panels next week which I am paying  $200 for. I'll see how I go with those and add from there.

Don't know where you are but there is no way you could do better with a tracker than an extra panel.... or several. Used panels are great value from what I am seeing.  They all come with a 20 or 25 Yr warranty so obviously in the scheme of their life,  even 4 years out of them (>20%)  for at least a 75% cost saving is a damn good deal.

And lets thing logically... these used panels are being upgraded and replaced after a few years. Who really thinks they are going to have the same panels on their roof  in 20 years even if you are still at the same place? the technology is moving so fast we'll probably be replacing the whole roof as one panel  and  all be off grid with the development of residential batteries and it will all cost a pittance of what it does now.  Probably be a mandatory regulation in fact.

I'd definitely be looking for extra used panels and if you can't get them, should still be able to pick up new for under $1 a watt and there is no way a tracker on that size system especially is going to outdo that bang for your buck.

Also think in less than ideal conditions, cloudy days for example. You will get a LOT more out of extra panels under those conditions that a tracker would give you there as well.

DamonHD

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Re: Add a solar tracker or buy more panels?
« Reply #4 on: August 31, 2016, 11:34:10 AM »
Hi,

@george65  Maybe a Jamaican should aim at true south (or a little to one side of it to maximise output at some time other than noon)!  B^>

Also, I agree with you on th 2nd-hand panels; I picked up a similar bargain, which works out about 10x cheaper per watt than the grid-tie that I put up ~8 years ago.  Astonishing.

@fabieville  more panels, possibly on separate strings/controllers and pointing in different directions to generate energy throughout the day may be your best bet, similar to my experiment here in some ways:

http://www.earth.org.uk/expanding-off-grid-PV-system.html

Rgds

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madlabs

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Re: Add a solar tracker or buy more panels?
« Reply #5 on: August 31, 2016, 02:24:41 PM »
I'd say add the panels and forget the tracker. I have always wanted to build one and have all the stuff to do so. But I just can't justify the time to build and debug and then maintain. And I'd love to do it, as a project. Would be fun. But there are other things to do with time and money.

When I first moved off grid I made a small array that I could adjust seasonally. I soon discovered that I was too lazy to move it and that I did just fine when I left it in the fall/spring setting. So when I upgraded to 4.3kW worth of panels I just made them fixed. Works great and takes no effort to maintain on my part!

Just one lazy guy's .02

JOnathan

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Re: Add a solar tracker or buy more panels?
« Reply #6 on: August 31, 2016, 02:39:09 PM »
Hi,

A few years ago, I developed a Simple, Robust and Cost effective 2kW Tracker.

Because most Trackers stuff was either to expensive, built and weighs like a tank, and just not cost effective for the 28% to 30% gain over a static array at N48 52' 03".

Anyways, I put a small book together, and hopefully it will help others.   http://www.echorenovate.com/purchase-book---make-a-2kw-solar-tracker.php

We here are a Not for Profit, the cost covers the colour printing and the postage anywhere in the World.

Yes, the Trackers have been tested in Hurricane conditions.  Regards the improved output against a static array, again my trackers have been tested against my 2.5kW static array.

Cost of materials of my 2kW tracker, about $800 USD, that includes the Sensor circuit from Dave in Australia and the important 24inch Actuator.

I trust this helps.

Mods.... Hopefully this reply does not contravene your selling rules.   
Everything is possible, just give me time.

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3 Hugh P's 3.7m Wind T's (12 years) .. 5kW PV on 3 Trackers, (8 yrs) .. 9kW PV AC coupled to OzInverter MINI Grid, back charging AC Coupling to 48v 1300ah battery

mab

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Re: Add a solar tracker or buy more panels?
« Reply #7 on: August 31, 2016, 04:06:03 PM »
I do have a tracker that i built back when PV cost £10/watt and it made sense to maximise the output of a small array. I still use it but only because it's already there.

I'd buy more PV - on a sunny day the extra PV would still give you more than a tracker I think - and on an overcast day a tracker doesn't give you anything, whereas extra PV will still give you extra power.  Although, as you're in Jamaica, you probably don't see as many overcast days as I do in Wales.

Ungrounded Lightning Rod

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Re: Add a solar tracker or buy more panels?
« Reply #8 on: August 31, 2016, 04:06:22 PM »
A decade or more ago solar panels were very expensive.  Despite the cost (and maintenance, and extra points of failure) you could sometimes come out ahead with a tracer.

But the price of panels has dropped like a rock.  (Something like Moore's law applies to their technology improvements.)  Meanwhile the price of the mechanical stuff for a tracker has not fallen substantially (has perhaps risen?) and the cost of the components of its control electronics (where it's even used), though it may have dropped, hasn't dropped substantially.

So these days it makes more sense to just buy more panels and keep it cheap, simple, and reliable.

Nearly the only place I've seen pros installing trackers at all these days are in large solar arrays, such as those over parking lots, where rotating a single shaft can tilt a BUNCH of panels at once.  Even there they're not tracking the sun in 2-D, just rotating on a parallel-to-the-ground axis.  Such systems have gaps between the panels, and are limited in how far they can track before the next row of panels shades the current set.  For a home system you'll probably be more pressed for space and will want to make the panels contiguous.  So one big composite panel, facing equatorward and tilted up to your latitude (maybe +- a seasonal adjustment or just tilted up a bit extra to get more power in the winter when sunlight is weaker and more precious), or several east-west rows of them spaced so they don't shade each other even at the winter solstice, is what I'd suggest.

(I DID see one at an auto dealership.  But it isn't a proper tracker - the panel, though it has two motorized joints, ends up at a fixed angle to a vertical axis rather than facing the sun.  It looks to me like more of an advertising gimmick than a serious solar energy collector.)
« Last Edit: August 31, 2016, 04:14:50 PM by Ungrounded Lightning Rod »

frackers

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Re: Add a solar tracker or buy more panels?
« Reply #9 on: August 31, 2016, 07:34:08 PM »
When I put 24 panels onto a barn roof that faced south (i.e away from the sun here), I knew I'd require frames to get them pointing towards the equator. http://gilks.ath.cx/gallery3/index.php/Solar/IMG_1967

By adding 2 extra holes in each support I can adjust them from 15deg (summer) to 45deg (spring/autumn) and to 60deg (winter). I get some shading when they are very upright (the rows are too close together!!) so this winter I've left them at the spring/autumn setting and not seen an appreciable difference in output to last year.

I always go to http://www.solarpaneltilt.com/ to see if/when I should be adjusting the angle of my panels.


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Ungrounded Lightning Rod

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Re: Add a solar tracker or buy more panels?
« Reply #10 on: September 01, 2016, 01:26:57 PM »
I get some shading when they are very upright (the rows are too close together!!) so this winter I've left them at the spring/autumn setting and not seen an appreciable difference in output to last year.

Partial shading of a panel can cause a disproportionate reduction in the output.  That's because, in a series string of solar cells, the output current of the string is that of the lowest output current cell in the string.  (How much this derates the panel depends on how it's mounted, how it's wired internally, and where the shadow falls.)

So you should be careful not to adjust them to the point where they shade each other, even a little.  Leaving them in the spring/autumn position is probably close to optimum.  Best would be setting them, for winter, to the minimum of the recommended tilt and the angle where the noonday sun on the winter solstice just misses shadowing the cells on the non-first-rank panels. (The last rank, of course, can be adjusted to the winter angle.)

Aim angle error only gives you a few percent reduction in power, even at the solstices.  For a new installation I'd be tempted to forego even the seasonal tilt adjustments and buy about 12% extra panels, instead.  That would avoid the hassle, as well as giving me extra power in the spring and fall
« Last Edit: September 01, 2016, 02:11:13 PM by Ungrounded Lightning Rod »

DamonHD

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Re: Add a solar tracker or buy more panels?
« Reply #11 on: September 01, 2016, 05:40:49 PM »
For my purposes, aiming to maximise mid-winter production, and for simplicity of mounting and best use of space in my small garden, I have just bought far more panels then nominally needed and mounted them vertically.  As ULR says, the loss from being 20 degrees or so from optimum is not huge.

Rgds

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