Virtual Tracker panel arrangement

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Re: Virtual Tracker panel arrangement

Postby Smurf1976 » Sat Feb 09, 2013 2:02 pm

Gordon-Loomberah wrote:I don't think there would be much to gain with another MPPT input, but a lot could be gained by using a 2kW inverter with Smurf's current PV array!

Agreed on both points.

So far as my inverter is concerned, it comes down to how much money I'm willing to invest into solar PV overall. That's not a question of profit, but of risk and it relates to governments changing the rules.

Old rule in Tas = maximum 3kW to qualify for 1:1 Net fit. Throw in the rapidly falling cost of solar PV and I ended up with two systems, total 2.88 kW (8 x 170 and 8 x 190) on two separate 1.1kW inverters. All up, both inverters cost me $400 in total (first one free, second one $400) which explains why I have them.

Then came the rule change which allows bigger systems. Hence adding the 9 x 250W panels recently.

But they're planning to privatise the retail side of the electricity industry down here with the switchover to private ownership less than 12 months away (January 2014). That being so, I'm just not willing to invest more $ into solar PV at the moment in case it ends up being a bad financial decision to do so.

95%+ of the increase in production I'd get with a bigger inverter would be exported to the grid since my daytime load is usually just the fridge and a couple of clocks etc as the house is empty during working hours Monday to Friday. So I'm just waiting to see what happens there, and in the meantime it's an interesting experiment to see just how much energy I do get from the current setup. I'm expecting about 3000 kWh over 12 months from it (in addition to the 1640 kWh I get from the other completely separate system with an identical inverter and 8 x 170W panels facing north).

I'll see what happens in January next year. That's unless the privatisation idea falls in a hole as I suspect it might.
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Re: Virtual Tracker panel arrangement

Postby trebla » Fri Feb 15, 2013 1:29 pm

Very interesting results G-L. I assume that the graph would be somewhat less flat and more like the north-facing output if the panels were on standard E and W facing roof slopes of about 30 degrees +/- 10 degrees.

Also, I would be interested to see the difference in daily power output between your N and E-W arrays in mid winter. I suspect the E-W panels would lose proportionally more insolation than the N panels, but perhaps by simply rotating your E and W frames to face more NE and NW the fixed array could be optimised for a maximum flat output for midwinter days. (You might similarly get a better midsummer output by rotating the frames to face more SE and SW). Actually, for your 31 degrees latitude the horizontal rotation would be somewhat less than it would need to be further south - there's probably an algorithm for this, but I would just follow the rising and setting sun. This is all very well for the back yard or for flat roofs, but with pitched roofs I think your stuck with equinoctial optimisation unless your good at complex geometrical construction.
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Re: Virtual Tracker panel arrangement

Postby Gordon-Loomberah » Fri Feb 15, 2013 1:49 pm

Yes, if they were tilted more like typical roof angles, then the graphs would be more peaky, but not as much as the N-facing panel curve. A-frame houses with E and W facing rooves are best suited for direct on-roof mounting in this arrangement, a more typical roof would require mounting frames, perhaps A-frames mounted on a N-facing roof. It's an easy build for ground mounted panels though.

Those tests were done not long after the summer equinox, when the sun rises well to the SE- so its not far off the worst end of summer performance for the Virtual Tracker arrangement, and it would improve up until the March equinox, with the sun more face-on to the panels, (although the sun hours decline) after which time the advantage will decline. Yes, having a limited amount of pointing adjustment would increase the output a bit, but the off-pointing for most of the time isn't very much compared with N-facing panels (for low latitudes), so it's probably not worth the extra mounting complications... you may as well build a proper tracker.
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Re: Virtual Tracker panel arrangement

Postby Cherokee Solar » Sat Feb 16, 2013 6:34 pm

Hi Gordon,

Thanks for taking the time to experiment with your idea - I did hear about it first from you! :D

Now that we know it works, I'm going to leave this as the last option for weaning myself off fossil fuels for the winter (Honda generator).

First came extra panels;
Then tree clearing;
Soon a 500w wind turbine; and
Lastly, a virtual tracking PV array maxed out for winter gain (facing NE).

The pareto principle is a nightmare...

96% of the year is no drama, the last 4% is a real drama... :shock:

Chris
Off grid solar + hot water. Heavily insulated + owner built flamezone house BAL-FZ. 300 mixed fruit trees + herbs + flowers + vegetables. Bees + heritage chickens. High up in the mountains north of Melbourne. http://ferngladefarm.blogspot.com.au/
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Re: Virtual Tracker panel arrangement

Postby Poundy » Wed Mar 20, 2013 8:31 am

Hmm, there's a rumour that NSW will permit you to add a NET metered system and not affect your current Solar Bonus GFIT. I have some east and west facing roofspace, perhaps now is the time to try the Virtual Tracker for real.
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Re: Virtual Tracker panel arrangement

Postby Gordon-Loomberah » Wed Mar 20, 2013 8:41 am

It's a bit more than a rumour ;)
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Re: Virtual Tracker panel arrangement

Postby Tracker » Wed Mar 20, 2013 2:33 pm

Smurf1976 wrote:But they're planning to privatise the retail side of the electricity industry down here with the switchover to private ownership less than 12 months away (January 2014). .....


Just noticed this comment..

I would wonder if it would not be better to jump in NOW... I would have thought that transition to PRIVATE retailers, would require that they honor existing arrangements, but, you can be certain that they WON'T be friendly and allow extra benefits AFTER they take over...
It's a gamble, but I suspect that I would be right.. If there is an advantage now... do it now...
..
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Re: Virtual Tracker panel arrangement

Postby Smurf1976 » Wed Mar 20, 2013 7:08 pm

Tracker wrote:I would wonder if it would not be better to jump in NOW... I would have thought that transition to PRIVATE retailers, would require that they honor existing arrangements, but, you can be certain that they WON'T be friendly and allow extra benefits AFTER they take over...
It's a gamble, but I suspect that I would be right.. If there is an advantage now... do it now...

I think you could well be right, although I'd expect the uncertainty would scare away some who can't afford to take risks.

It's a tad illogical financially, but I'm leaning toward the idea of putting the 4th string up late this year so that it's in prior to the changeover for the reasons you state. I'm keeping a fairly close watch on what's going on - I'm not in the power retailing industry but suffice to say I'm pretty close too it in terms of work so will likely hear what's happening before most.
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Re: Virtual Tracker panel arrangement

Postby Tracker » Thu Mar 21, 2013 7:13 am

Smurf1976 wrote: I'm leaning toward the idea of putting the 4th string up late this year so that it's in prior to the changeover

I would be inclined to apply for the MAX. and leave the options open..
We all know how THEY work.. They jump in early and close applications , so as to kill the last minute rush.... :?

The ideal would seem to be a virtual tracker system to cover YOUR background power, and then an efficient north facing system to supply a more demand based system.. ie. Off grid...On Grid..

The thing that concerns me for the virtual tracker system, that Gordon quantified and Karl had long ago exploited, is that it is not making best use of the available power.. ie there is 12% more POWER to be had from pure north..
The problem is how to have the best of both worlds... :?:
..
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Re: Virtual Tracker panel arrangement

Postby Gordon-Loomberah » Thu Mar 21, 2013 9:29 am

Tracker wrote:The thing that concerns me for the virtual tracker system, that Gordon quantified and Karl had long ago exploited...


Except that Karl was all pointing N apart from when he ran out of space, and suffered lots of clipping. The idea of the VT is to avoid that clipping and maintain even production throughout the day, and not cook the maxed out electronics in the process.

12% more power is useless if you cant use it and are being paid nothing or a pittance if you export it, just so the retailers can make a profit at your expense by selling it to your neighbour. Closely matching production to usage is the target these days!
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